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Flashcards in Micro 2 Deck (209):
0

What is orthoreovirus?

A member of reoviridae
Infects mammals, but not associated with serious disease in humans.

1

What kind of virus is rotavirus?

Reoviridae
-dsRNA genome - 11 segments
-most important cause of gastroenteritis in young children
-group A assoc. w/ human disease

2

What cells do Rotavirus infect?
How long is incubation?

Tip of villi in sm. intestine
- as few as 10 particles can cause infection
-1-4 days incubation period

3

Describe rotavirus pathogenesis

virus capsid proteins attach to glycolipid receptor on the apical enterocytes of sm. intestine villi.
-Damage to sodium and glucose absorptive mechanisms -> increased luminal H2O volume. Viral replication -> acute onset of vomiting and diarrhea
-Activation of intestinal nerves -> secretion of H2O
-Fluid accumulation in lumen of sm. intestine, 10-20 diarrheal episodes / day and severe dehydration

4

Describe rotavirus structure

Unenveloped, icosahedral, 3 layer protein capsid
Segmented dsRNA genome
capsid contains all enzymes needed for replication
VP4 receptor protein - binds glycolipid of host cell

5

What are the major coat proteins of rotavirus?

VP4 - outer coat - binds receptor (sialic acid / integrins)
VP7 - outer coat - stripped during endocytosis
VP6 - middle coat - major protein that is tested for in antibody titer
VP2 - inner coat

6

How is rotavirus infection diagnosed in a lab setting?

Presence of virus particles in feces early in illness
- immune electron micoscopy, ELISA, immunoassay

Rise in titer of Ab to VP6

7

What are the two most important viruses contributing to diarrheal illness in children?

Rotovirus (reoviridae)
Adenovirus

8

What type of genetic material is carried by Adenovirus?

dsDNA

9

What is the most common cause of viral gastroenteritis in older children and adults?

Norovirus

10

How is norovirus transmitted?

fecal-oral
also contaminated food: shellfish and contaminated water

11

How long is the Norovirus incubation period and how long does it remain contagious?

incubation: 12-48 hours
From onset of symptoms: highly contagious until at least 3 days after symptoms recede - infectious viral particles may be shed as long as 2 weeks after illness

12

Norovirus symptoms

Acute onset of vomiting, diarrhea, stomach cramps, headache, fever, chills, myalgia

symptoms resolve 24-48 hours after onset.

13

How is norovirus spread prevented?

Handwashing - soap and water (alcohol hand-gel is inadequate)
10% bleach to clean surfaces.

14

What family of viruses is norovirus from?

Calicivirus

15

What is norovirus genome?

ss+RNA

16

What virus families do Hepatitis viruses A-E belong to?

Hep A: Picornavirus
Hep B: Hepadnavirus
Hep C: Flavivirus
Hep D: satellite virus - undefined classification
Hep E: Hepevirus (Hep - E - virus)

17

Genomes of Hepatitis A-E

A: ssRNA
B: dsDNA
C: ssRNA
D: ssRNA (-)
E: ssRNA

18

Which Hepatitis viruses produce chronic illness?

B and C
D in the context of association with B (is not infective on its own)

19

What causes hepatic cellular carcinoma

Chronic viral infection is leading cause (HBV, HCV)
course of chronic illness is 25-50 years
Ultimate cause: constant inflammation and constant stimulation of cellular replacement -> mutation and tumor formation

20

What was the first successful recombinant vaccine for a human disease?

Hep B vaccine

21

How is HBV spread?

sexual contact and parenteral exposure

most adults clear infection - 5% do not -> chronic infection
--May be asymptomatic

22

Describe the HBV genome

Circular, partially double stranded DNA.
Full length (-), 20-80% (+)

23

Describe the process of HBV replication

Genome is circular (-) DNA with partial (+) DNA. In nucleus, cellular DNApol -> full dsDNA
(-) DNA -> full length (+) RNA via host cell RNA pol II
(+) RNA is packaged in new core proteins
viral RNA/DNA dependent DNApol -> full length (-)DNA
(-)DNA copied by viral DNApol -> partial (+) DNA
HBsAg containing envelope acquired on exocytosis

24

How is HBV prevented / treated?

Recombinant vaccine
Interferon - alpha and/or inhibitors of HBV polymerase

**These do not eliminate infection***

25

Describe Hep D'd genome and what it codes

Small (-)RNA genome (1.7kb)
codes one protein: delta antigen: RNA encapsidation

26

What is HDV superinfection?

Infection w/ HDV after host is already infected with HBV.
contrast w/ coinfection, where both acquired together
Superinfection -> high mortality (20%)

27

What family of viruses does HCV belong to?

Flavivirus

28

Describe HCVs genome

(+)ss linear RNA

29

How is HCV infection treated?

Combination of interferon-alpha and ribavirin
-can eliminate infection, but IFNa has unpleasant side-effects

2 new drugs w/ this mix -> 70-80% cure rate

30

How is HCV transmitted?

Contaminated blood products
Injection drug use
Mother to child (uncommon)
sexual contact

31

what is the leading cause for liver transplant necessity?

HCV infection

32

What is the course if HAV infection in humans?

Initial infection in intestinal mucosa -> liver -> lymphoid cells
Virus is excreted in large volume (10^8 infective units/ gm feces) in feces.

**no chronic infection** leading cause of jaundice world wide

33

Where is HEV infection most common? Who is most severely effected?

Mostly in developing countries - drinking water contaminated w/ feces. May be carried by rats, pigs, deer.
Pregnant women - 20% mortality rate

34

What are M cells?

Found in mucus membranes of GI - antigen presenting cells
phagocytize bacteria and foreign particles and pass them to macrophages underlying the Mcell

35

What is MacConkey's agar?

Selects for gram (-) organsisms
Bile salts and crystal violet inhibit gram (+) growth
pH indicator distinguishes between lactose fermenting (pink colonies) and non lactose fermenting organisms

36

3 types of secretory diarrhea and responsible organisms

Secretory Diarrhea: non-inflammatory, non-invasive
1. Bacterial enterotoxigenic: Enterobacteriaceae and Vibrionaceae
2. Bacterial neurotoxic: usually a preformed toxin is ingested: C.botulinum, B.cereus, S.aureus
3. Non-inflammatory parasitic: G.lamblia, C.parvum

37

3 types of invasive inflammatory diarrhea and organisms responsible

1. Bacterial cytotoxin caused inflammation: C.diff, EHECCCC
2. Bacterial invasive infection: Shigella, EIEC, Salmonella
3. Parasitic invasive: E.histolytica

38

Vibrio Cholerae: organisms of interest and characteristics

O1 and O139
Gram neg, oxidase pos, motile (single polar flagella), comma shaped rods
found in brackish water, fresh water ponds, can colonize shellfish
Two types of O1: Classic and El Tor
Classic - highly virulent, but does not survive freely in enviro well
El Tor - less virulent, but survives in environment for long periods

39

What are V.cholera's virulence factors?

Motility - single polar flagellum
Adhesion - tcp pili (toxin co-regulated pili) and other adhesins - tight adhesion to intestinal epithelium
Cholera toxin

40

Describe Cholera toxin and its activity

AB type toxin (A is enzymatic, B is binding, consists if 5 identical units)
ADP ribosylating
B attaches to GM1 ganglioside, A1 is released to enter cell
A1 ADP-ribosylates Gs -> chronic activation of Gs -> massively increased cAMP -> hypersecretion of fluids, chloride ions, inhibition of Na absorption
End result is massive fluid loss

41

Describe the etiology / pathogenesis of cholera

ingestion of organism via contaminated water or food
10^8 organisms needed for infection - V.cholera sensitive to gastric acid
2-3 day incubation period, high replication
vomiting, high volume watery rice-water diarrhea **no PMNs** profound dehydration

42

How is Vibrio cholera identified in the lab?

Stool sample
Culture on TCBS (thiosulfate-citrate-bile salt-sucrose agar) - highly selective for vibrio species
Positive oxidase test
O antigens: O1 and O139 - assoc. w/ cholera toxin producing strains

43

5 classifications of E.coli and assoc. symptoms

ETEC (Enterotoxogenic): Watery d., cramps and low fever. Infants and travellers. Cytotoxins increase cAMP or cGMP
EAEC / EAggEC (Enteroadhesive): Persistent infant d., also AIDS pts. Sometimes gross blood. Low fever. Aggressive adherence to intestinal mucosa prevents fluid absorption
EPEC (enteropathogenic): copious watery d. w/ mucus in infants. Fever, N/V. Adhere and destroy epithelium of INTESTINE
EIEC (enteroinvasive): watery diarrhea then scant bloody stools. fever. invasion and destruction of epithelium of COLON
EHEC (enterohemorrhagic): watery d. then grossly bloody d. Hemolytic uremia (O157:H7). Cytotoxic verotoxin prevents protein synth.

44

What is ETEC and how is it identified

Enterotoxic E.coli - causes secratory diarrhea - traveler's diarrhea, Montezuma's revenge. Major cause of infant mortality worldwide.

ELISA or agglutination tests for the presence of toxins
DNA probes for LT and/or ST genes

45

What are the ETEC toxins?

LT - heat labile toxin - destroyed at 100deg C for 30 min, 75% similarity to cholera toxin (AB structure) and same mechanism (B binds GM1, A unit: ADP ribosylation of Gs -> increased cAMP or cGMP) new evidence: Type II secretion
ST - heat stable toxin - not destroyed at 100deg C for 30 min., family of small molecules. Bind membrane bound guanylate cyclase -> chronic elevation of cGMP -> fluid and electrolyte loss
***note: both LT and ST are plasmid encoded***

46

How is ETEC spread? What are symptoms?

contaminated food and beverages
most common in tropics and in young
Symptoms: N/V, weakness, dizziness, then watery diarrhea

47

How do ETEC adhere to a host?

Colonization Factor Adhesions (CFA) - plasmid encoded - allow binding to epithelium of sm. intestine

Bundle forming pilus - similar to Tcp pili of v.cholera

48

What is EPEC and how is it identified in the lab

Enteropathogenic E.coli: causes severe, often fatal, diarrhea in infants and children primarily in developing countries. Traveller's diarrhea in adults.

Identified via ELISA and multiplex PCR

49

How does EHEC attach to host cells?

Bundle forming pilus - non-intimate attachment
Tir and intimin - closer, intimate attachment
-bacteria produce and secrete Tir (type III secretion), which embeds in host cell membrane and binds to bacterial intimin (in bacterial outer membrane), Tir interacts w/ actin cytoskeleton and forms pedestal-like structure beneath organism -> effacement: destruction of pili

50

Describe the etiology / pathogenesis of EPEC

Fecal - oral spread
Diarrhea not caused by toxin: caused by destruction of microvili (rearrangement of actin cytoskeleton) -> malabsorption and diarrhea

51

What is clostridium botulinum and how is it recognized in a lab?

Obligate anaerobe, gram (+) rod that produces botulism neurotoxin.
Spore forming
Usually clinical identification w/o culture
Can be grown in O2 free lab environment
Immune assay for toxin in food sample, blood, gastric contents

52

How does botulinum toxin work?

Usually ingested as a preformed toxin via contaminated food
**sypmtoms 12-36 hrs after ingestion**
AB toxin - B portion binds ganglioside receptors on nerve cells
Toxin blocks presynaptic release of ACh - prevention of muscle contraction and flaccid paralysis - death via respiratory collapse

53

Can botulinum toxin be inactivated?

Yes - boil 10-15 minutes
Spores are not destroyed (can withstand 100deg C for 3-5 hrs)

54

What are infant and wound botulism?

Infant botulism: infants have incomplete gut microflora. C. botulinum can colonize and produce toxin -> SIDS (v. rare)
-seen in cases of mothers giving infants honey

Wound botulism: colonization of deep wound (anaerobic) - organism found in nature, can contaminate wound, grow and produce toxin

55

What is the most common form of bacterial food poisoning?

Staph aureus

56

Describe S.aureus enterotoxin action.

Preformed toxin is ingested and absorbed. Assoc. w/ food being left out - potato salad, cold cuts.
Stimulation of neural receptors in gut - signal to emetic center -> projectile vomiting within hours
Enterotoxin is heat stable

57

What bacterial food-borne organism is associated with Chinese restaurants / fried rice?

Bacillus cereus

58

Describe B.cereus toxic effects

2 forms:
1. Emetic: (1-6 hrs post ingestion) ingestion of preformed toxin (fried rice held at room temp for a long period). S.aureus like N/V, cramps
2. Diarrheal: (8-16 hrs. post ingestion) toxin formed in vivo. Activation of intestinal AC -> elevated cAMP, fluid excretion, diarrhea. meat or veg. foods held at room temp after cooking.
*** both forms subside ~24 hrs. after onset ***

59

What is Clostridium perfringens?

Gram (+) rod, anaerobic spore-former.
Similar toxic effect to B.cereus
Assoc. w/ cooked food being left at room temp (meat, veg, gravy)
Abd cramps, N/V, diarrhea, no fever.
Symptoms 8-24 hours after consumption. Toxin produced in GI tract.

60

What are the symptoms of Giardia lamblia infection?

Acute watery diarrhea, cramping, flatulence.
May develop chronic diarrhea. Symptoms may wax/wane over a long period. Weight loss common.

61

What is Giardia lamblia and how is it identified?

Protozoan. Flagellated.
Two stage life-cycle: Trophozoite (free-living) cyst (infective)
Identified by microscopic examination of stool, duodenal aspiration, or duodenal biopsy - look for cyst
string test
Antigen test of stool

62

What is giardia's incubation period?

7-10 days

63

What is Cryptosporidium parvum? Describe infection

Protozoan most often isolated in HIV patients w/ diarrhea
severe, prolonged, watery diarrhea in immunocompromised, less severe in normal
Oocyst ingested in contaminated water -> sporozoite in intestine -> Enters intestinal epithelial cells -> sexual / asexual reproduction -> oocysts released and shed in feces

64

What is Clostridium difficile and how is it identified?

Gram (+) rod, anaerobic, spore forming
Normal flora in ~5% of adults, but can cause inflammatory diarrhea (inflammation of colonic mucosa)
Culturing is not helpful to identification
Toxin test on stool is most helpful: EIA

65

What are C.diff's virulence factors?

2 toxins
A: enterotoxin: -> accumulation of viscous bloody fluid in colon. Chemotactic for PMNs -> PMN lysis -> release of inflammatory mediators, fluid secretion, altered membrane permeability, Hemorrhagic necrosis of mucosa.
B: cytotoxin: disrupts actin polymerization and cytoskeletal organization, inhibits protein synthesis - similar in effect to diptheria toxin

66

What is pseudomembranous colitis?

Can be caused by C.diff infection
pseudomembrane forms at site of epithelial cell destruction - consists of fibrin, mucin, and dead PMNs, leukocytes
Produces watery, sometimes bloody diarrhea, may be mucus present. Abdominal pain and cramps, fever, nausea. In severe cases may be lethal.

67

What is EHEC?

Enterohemorrhagic E.coli (also STEC (shiga-toxin e.coli) and VTEC (verocytotoxin e.coli))

68

How is EHEC identified in the lab?

Gram (-) rod, facultative anaerobic
O157:H7 does not fement sorbitol, so can be selected for on sorbitol MacConkey agar
Serotype with anti-O157:57 serum
demonstrate pathogenic activity with vero cells
DNA probe for shigella toxin genes

69

EHEC virulence factors

Adhesion: Tir and intimin production - tight binding
Toxin: Shiga toxin
Type III secretion: attaching and effacing lesions

70

What is Shiga toxin?

Produced by EHEC also vero cytotoxin
AB toxin
B binds G3 ganglioside receptor. A subunit enzymatically modifies 28S rRNA of 60S ribosomal subunit - blockade of protein synthesis and cell death
Capillary thrombosis, inflammation of colonic mucosa, hemorrhagic colitis
Shiga Toxin I and II encoded by plasmids (Stx1, Stx2)

71

Describe the etiology of EHEC

Usually spread via contaminated food (Ground beef)
Small number of organisms can cause infection
Incubation period of 3-4 days - severe crampy watery diarrhea that evolves to grossly bloody diarrhea
Hemolytic Uremic Syndrome: 5-10% of patients - esp. children
-acute renal failure, thrombocytopenia, hemolytic anemia.
-shiga toxin damages renal glomerular cells

72

How is Shigella identifiable in the lab?

Gram (-), non-motile, lactose neg on MacConkey and Hektoen agars.
Serotyping - 4 groupings:
1. Group A: S. dysenteriae (Shiga bacillus - largest producer of toxin)
2. Group B: S. flexneri
3. Group C: S.boydii
4. Group D: S.sonnei (60-80% of US cases)

73

Describe Shigella infection and illness

Transmitted by food, fingers, flies, feces
Organisms multiply in sm. intestine, esp. lower sm. intestine.
First 12 hrs: abdominal pain, cramping, fever
12-72 hrs: organism is no longer in upper intestine. pain intensifies, dysentery, tenesmus, lethargy. Many PMN in mucoid stool.

74

Explain Shigella virulence

Invasiveness: entry via M.cells, passed to macrophage, apoptosis induced, IL-1, inflammatory factors, PMN chemotaxis
PMN open tight junctions allowing Shigella to penetrate epithelium.
Escape from phagosome and movement to epithelial cells. Actin rearrangement "actin based motility" - allows bacteria to move through cell and enter neighbors.
Epithelial cells die after infectoin - ulcerative colitis
Product is bacillary dysentery. Only S. dysenteriae produces toxin which contributes to death of epithelium. Primary virulence is via cell invasion.

75

What is EIEC?

Enteroinvasive E.coli
Behaves like Shigella - cell invasion, actin rearrangement - cell death - dysentery. Symptoms the same.
No tests to differentiate from other E.coli strains,but can be differentiated from Shigella. Rare.

76

3 forms of Salmonella infection

Gastroenteritis: most common - 8-48 hour incubation, abrupt onset, low fever, diarrhea, N/V, 2-5 day duration.
Bacteremia: invasion of blood stream following oral ingestion. High spiking fever, septic. Usually no GI symptoms. Rare.
Enteric (Typhoid) Fever: 7-20 day incubation, chills, headache anorexia, myalgia, enlarged spleen and lymph nodes, gradual fever, insidious onset, early constipation followed by bloody diarrhea, lasts several weeks. 1/3 of patients develop maculopapular rash (rose spots) on trunk.

77

In chronic carriers of Salmonella, where is the organism reservoir?

Gall bladder

78

What size Salmonella inoculum causes illness?

10^4 - 10^8
Large inoculum needed.

79

Explain Salmonella's virulence

Invasion: enter M cells or intestinal mucosa epithelial cells - multiplication within vessicles (phagosomes) -> cell lysis
Type III secretion: Actin rearrangement -> ruffled border
Endotoxin: Lipid A of LPS induces inflammatory response and contributes to mucosal dammage.

80

How is Salmonella identified in the lab?

Gastroenteritis: culture lactose neg, oxidase neg colonies, serological tests to determine serotype (there are many)
Bacteremia: blood cultures, stool cultures (usually negative)
Typhoid fever: early - blood culture, later - stool

81

How can Salmonella be differentiated from Salmonella in the lab?

Growth on Hektoen enteric (HE) agar
Salmonella grows distinct black colonies due to H2S production

82

What is campylobacter infection associated with?

Usually chicken consumption - undercooked
Sometimes other meats, raw milk

83

What are the symptoms of campylobacter infection?

Fever, malaise, abd. cramps, profuse watery / bloody diarrhea, mucosal inflammation.

84

How is campylobacter identified?

Small, motile, flagellated bacteria. Comma shaped, gram (-), Oxidase pos (vs. Salmonella and Shigella neg)
Microscopy: stool sample - darting motility
Will not grow on MacConkey
microaerophilic and capnophilic (doesn't ferment glucose)

85

What are Campylobacter's virulence factors?

Flagella - motile in mucus layer of sm. intestine, multiply in mucus
Toxins - enterotoxin, endotoxin, cytotoxin - destroy intestinal cells -> bloody diarrhea
Protein S - surface protien, blocks complement binding - serum resistance to phagocytosis
Autoimmune response: "Guillain-Barre" cross-reaction between host myelin and Campylobacter surface structure

86

What is Guillain-Barré syndrome as it relates to Campylobacter?

cross-reactivity between organism surface proteins and host myelin
Self-reacting Ab formed -> inflammatory demyelinating polyneuropathy
Symptoms emerge 1-3 weeks post infection. Bilateral weakness,

87

Yersinia enterocolitica - What and what does it cause?

belongs to family enterobacteriaceae - gram (+) cocci
Zoonotic - transferred from animals to humans (rabbits, rats, livestock)
Causes Enterocolitis with necrosis of Peyer's patches
-bloody diarrhea, fever, abd. pain lasting 1-2 weeks
-inflammation of messenteric lymph nodes mimics acute appendicitis (esp. in young children)
- transfusion related septicemia (grows in blood at low storage temps)

88

What bacteria is associated with transfusion related septicemia?

Yersinia enterocolitica

89

How does H.pylori protect itself from stomach acid?

Urease: Converts urea to ammonia and CO2. Organism is surrounded by a layer of ammonia that protects from acid.

90

How is H.pylori identified?

Small, gram (-), microaerophilic, motile, curved bacillus
Gastric biopsy for culture, and rapid urease - CLO (campylobacter like organism) test

91

What toxins does H.pylori produce?

Cytotoxin and mucinase - contribute to tissue destruction and infiltration of inflammatory cells in ulcer formation

92

How is Listeria monocytogenes identified?

Small, facultative anaerobes, non-spore forming, catalase pos, oxidase neg, B-hemolytic, gram (+) bacillus

93

How are people infected by Listeria monocytogenes and what is the result?

Listeria is ubiquitous in nature, but usually infection through food - raw veg, raw milk, soft cheese, fish, poultry, meat (including ready-to-eat, like hot-dogs)
Motile bacteria crosses mucosal barrier of intestine and enters blood stream and:
1. is cleared by host immune system
2. infects other organs (esp. in immuno suppressed population) -esp. CNS - meningitis
3. crosses placenta to infect fetus - birth defects, spontaneous abortion

94

What are 3 roundworms that can infect humans?

Ascaris lumbricoides - intestinal roundworm
Enterobius vermicularis - pinworms
Ancylostoma duodenale and Necator americanus - hookworms

95

What are symptoms of Ascaris lumbricoides infection?

Often asymptomatic
GI upset, colic, loss of apetite
In heavy infestation worms can ball up in sm. intestine and cause obstruction

96

What are Taenia saginata and Taenia solium?

Tapeworms
Taenia saginata - beef tapeworm
Taenia solium - pork tapeworm - can invade gut wall and migrate to other tissues and form cyst - cysticerocosis

97

What are symptoms of peritonitis?

Abdominal distention, pain, decreased appetite, fever, nausea, thirst, vomiting, absence of bowel sounds.
May be other signs of shock

98

Three types of peritonitis

Primary - develops without an evident source
Often associated w/ advanced liver disease
-Usually caused by gram (-) rods: E.coli, Klebsiella (>50%)
-~25 % by gram (+) organisms - streptococcus
Only facultative anaerobes - oxygen content of ascitic fluid prevents obligate anaerobes from living

Secondary: Trauma related - spillage of GI or UG organisms into peritoneal cavity. Usually polymicrobial.

Dialysis associated: often involves skin flora. Usually monomicrobial. usually: S. epidermidis, S.aureus, E.coli, Pseudomonas aeruginosa

99

What are E.coli virulence factors

Adherence - 20 factors
Endotoxin - lipid A (LPS of outer membrane): activates complement -> inflammation; stimulates cytokine release -> septic shock
LPS -> LPS binding protein -> CD14 on monocytes and macrophages -> activation

100

What organism is most frequently involved in CAPD peritonitis?

S.aureus

101

What are the virulence factors of S.aureus?

Pili - adherence
Capsule - antiphagocytic, promotes adherence to tracheal epithelium
Endotoxin - LPS - may cause shock
Exotoxin A - increases tissue destruction by inhibition of protein synthesis (similar to diptheria)
Extracellular enzymes - pyocyanin: blue pigment, suppresses other bacterial growth, impairs function of nasal cilia

102

How do intraperitoneal abscesses usually form?

Complication of general or secondary peritonitis, appendicitis, diverticulitis, surgery or other intra-abdominal pathology.
Usually polymicrobial (~4, up to 12) consisting of endogenous flora
*Bacteroides fragilis

103

What is Bacteroides fragilis and how is it identified?

Gram (-), anaerobic, encaspuslated bacillus
Normal flora of GI tract- causes infections when it escapes - major cause of intra-abdominal abscesses
Produces foul-smelling discharge from wound (anaerobic metabolites)

104

What organisms are commonly associated with congenital infections?

Viruses spread mother -> fetus: HIV, CMV, rubella
Bacteria: L.monocytogenes, T.gondii

105

What organisms are commonly associated with parinatal infection?

Perinatal: passage down birth canal
L.monocytogenes
E.coli
S.agalactiae (Group B strep )

106

What organisms are commonly associated with post-natal infection of the newborn?

Organisms that can be spread through milk, saliva, physical contact
L.monocytogenes
S.agalactiae (Group B strep - B-hemolytic)
E.coli

107

What is the leading cause of bacterial meningitis in newborns?

Group B strep
S.agalactiae - normal flora of female UG tract and GI

108

How is Streptococcus agalactiae identified?

Gram (+), catalase neg, B-hemolytic, grow as diplococci or short chains in liquid.
In the case of bacterial meningitis - lab evaluation of CSF. Culture needed, but immediate gram stain should be done for empiric treatment.

109

What are Early and Late Onset Diseases caused by GBS?

EOD: Within first week of birth (usually w/in 24 hrs)
-meningitis, pneumonia, bacteremia
LOD: After first week of birth
-usually meningitis
-risk factors less well understood

110

What are the risk factors for Early Onset Disease involving GBS?

Maternal carriage of GBS
Low anti-capsular IgA
Early delivery
Early / prolonged membrane rupture

111

What are GBS virulence factors?

Capsule - most important - 9 serotypes (type 3 most assoc. w/ disease)
-sialic acid moiety on terminal sugar - limits C3b deposition and complement activation, thus phagocytosis
Invasion - can invade respiratory epithelium and cross BBB
B-hemolysin - damages respiratory epithelium, cytolytic for brain epithelium, enables crossing of BBB

112

What E.coli strain is associated with newborn meningitis?

E.coli K1 - normal inhabitant of lg. intestine. Similar to GBS.

113

Virulence factors of E.coli K1

K1 polysialic capsule: resistance to killing by neutrophils and normal serum, survival in blood and CSF
Invasins: IbeA and IbeB: needed to cross BBB
Type O antigen LPS
S.fimbriae - important for establishing infection

114

What are symptoms of E.coli K1 meningitis in a newborn?

Variable, and possibly subtle
respiratory distress, fever, poor feeding, abdominal distension
Culture CSF and treat on suspicion

115

How are Listeria infections of the newborn usually acquired?

From contaminated food.
Mother consumes and transfers to fetus.
Organism exhibits tropism for placenta and fetus.
Usually fatal - stillbirth, spontaneous abortion, premature labor.
Listeriosis of newborn usually acquired during delivery -> meningitis

116

How is Listeria immunity mediated?

Cell mediated immunity - Listeria is intracellular pathogen
Initial infection: macrophages, then CD8+ Tcells

117

What are Listeria's virulence factors in the setting of fetal/newborn infection?

Internalins - allow cell invasion
Listeriolysin O - escape from vacuoles
ActA - recruits host-cell actin for motility and spread cell to cell w/o exposure to extracellular environment.

118

What is the lifecycle of Toxoplasma gondii?

Oocyst consumed (fecal-oral)
Trophozoite is mature asexual proliferative form - infect cells, replicate, burst cells
Tissue cyst bradyzoite forms once immune response is initiated - cysts can exist in tissue for life of individual.

119

What happens if a woman is infected with T.gondii for the first time during pregnancy?

Often stillbirth or spontaneous abortion.
Live births: microcephaly, hydrocephaly, motor disturbances, convulsion. May appear normal at birth, but develop problems later (retardation, chorioretinitis)
Subsequent births: no risk of transmission to fetus

120

What is a primary histologic marker of chronic hepatitis?

Bridging fibrosis w/in hepatic lobules from central vein to portal triad

121

What are the most common initial symptoms of viral hepatitis?

Malaise, weakness, N/V, anorexia, vague dull RUQ pain, low grade fever - all precede jaundice if it occurs (50-80% of pts do not experience jaundice)
Jaundice and dark urine usher in icteric phase - bring pt. to doctor.
Also - smokers lose appetite for smoking.

122

what is the effect of circumcision on STI transmission? Why?

Reduces risk of acquiring HIV by 51-76% (hetersexual)
Large population of macrophages, CD4+ cells in nonkeratinized inner mucosal cells of foreskin.
Also: decreased incidence of HPV, HSV - 2, syphilis, and trichomonas.
No effect: N.gonorrhoeae, C.trachomatis
Female partners: decreased risk for HSV, BV, trichomonas

123

What symptoms are associated with urethritis?

May be asymptomatic
Urethral discharge - purulent / mucopurulent
Dysuria, burning, pain, pruritus (itching)

124

What are the causes of urethritis?

Most involve N.gonorrhoeae
Often polymicrobial
Chlamydia (if gon, at least 30% likliehood of having Chlamydia)
Mycoplasma genitalium
etc

125

Arthritis-dermatitis is the classic presentation for what?

Disseminated Gonococcal Infection
Bacteremial spread of Gonorrhea

126

What are the symptoms of Neisseria gonorrhoeae infection?

Urethritis - mucopurulent discharge
Mucopurulent cervicitis - vaginal discharge
dysuria
Pelvic Inflammatory disease in 10-20%
Disseminated gonococcal infection
pharyngitis, conjunctivitis

127

How is Gonorrhea diagnosed?

Gram stain of urethral, cervical, or anal swab
-Gram (-) diplococci within or associated w/ PMNs
-sensitive and specific
Culture - Modified Thayer Martin media (2-3 days)
-can test susceptibility
-preferred for pharynx and rectum
DNA probe, PCR, NAAT (nucleic acid amplification test)- best (very highly sensitive and specific - near 100%)

128

What medium is N.gonorrhoeae grown on?

Modified Thayer Martin

129

What is treatment for Gonorrhea?

Cephalosporins - resistant to FQ, Penicillin, tetracycline
Ceftriaxone 250mg IM or
Cefixime 400 mg (single dose PO) or
Cefpodoxime 400mg (single dose PO)
Always include treatment for chlamydia - azithromycin or doxycycline

130

Who is more likely to be an asymptomatic carrier of gonnorhea: male or female?

Female

131

Who is more likely to be an asymptomatic carrier of chlamydia: male or female?

Common in both

132

What can be said about women w/ positive cervical culture for chlamydia?

Probable upper genital tract infection

133

Who should be screened for chlamydia?

All young women, annually (<25) regardless of sexual risk.
Older women w/ risk factors
No routine screening in males

134

How is chlamydia diagnosed?

Women: urine or swab from endocervix or vagina
Men: urine or urethral swab, anal swab
Culture, immunofluorescence EIA - no longer used
Nucleic Acid Hybridization
NAAT - best sensitivity, modern standard

135

What is therapy for chlamydia?

1g single dose of azithromycin - preferred
or - doxycycline 100mg bid 7days

amoxicillin in pregnant patients

136

What is the most likely cause of urethritis if non-gonococcal?

Mycoplasma genitalium - most often (10-25%)
then Chlamydia trachomatis

No identifiable pathogen - frequent finding

137

How is non-gonococcal urethritis treated?

1g single dose azithromycin - preferred
or - doxycycline 100mg bid 7 days

M.genitalium often fails with doxy, and increasing resistance to azithromycin

138

What bacteria are commonly associated with PID?

N.gonorrhoeae 30-50%
C.trachomatis 25-40%
Mixed bacteria 25-50%

Natural vaginal flora also common - reduction in lactobacilli -> overgrowth, infecton

139

What organism is associated with chancroid?

Hemophilus ducreyi

140

What are the symptoms of Syphilis?

Slow development (12-40 days incubation)
Primary painless ulcer at site of inoculation (penis, vagina, vulva, mouth)
No purulence
Painless inguinal lymphadenopathy

141

What are the stages of syphilis?

Primary infection: painless ulcer, painles lymphadenopathy
Secondary (6weeks - 6mos): multiple mucocutaneous lesions, fever, alopecia, lymphadenopathy, meningitis
Tertiary (months - years): gumma (necrotic sores)

142

What is the modern algorithm for identification of Treponema pallidum (syphilis)?

EIA or CIA -> if pos: quantitative RPR -> if pos, syphilis
if neg: TP-PA (treponema pallidum particle agglutination assay) -> if pos: syphilis, if neg: syphillis unlikely

143

How is syphilis treated?

Early: Benzathine Penicillin - IM
Latent / asymptomatic neurosyphilis: Benzathine Penicillin - IM weekly, for 3 weeks
Neurosyphilis: IV Benzyl Penicillin X 10days (IV Cephtriaxone)

144

How do we know if syphilis treatment is working?

4 fold drop in titer in 6mos (early syph) or in 24 mos (latent/ late)

145

What causes gential herpes?

HSV 1 and 2
2 primarily, but 1 is on the rise
2 does not infect mouth

146

What are the symptoms of genital herpes?

Multiple painful, shallow genital ulcers
May be missed
Constitutional changes (F>M)
Fissures (F)
lymphadenopathy, cervicitis, urethritis

147

What is treatment for genital herpes?

7-10 days treatment:
acyclovir
famcyclovir
valacyclovir
can't eradicate virus, but goal to decrease viral shedding and recurrences.

148

How is Herpes diagnosed in the lab?

Direct Fluorescent Antibody test
Culture (specific, not sensitive)
PCR
Type specific IgG serology - commercial kits

149

What is the most frequently reported infectious disease is the US?

Chlamydia
Gonorrhea is #2

150

Lymphogranuloma venereum

Caused by Chlamydia trachomatis (serotypes L1-3)
More common in developing countries
Persistent Chlamydia infection - begins with small papule on genitalia, anus, or rectum - heals in a few days
Regional lymphadenopathy - systemic symptoms (fever, rash, nausea)
No treatment

151

How is chlamydia cultured?

Indirectly. Can't culture the organism itself, but can culture the cells that it inhabits
epithelial or reticular cells

152

Describe Chlamydia's lifecycle

Two stages:
Elementary Body - infectious - enters cell to form RB
Reticulate Body - non-infectious, metabolically active

EB enters epithelial cells, inhabits endosome and converts to RB which multiplies extensively. Under stress, can remain in RB stage. Otherwise, binary fission -> EB which are released.

153

What happens in persistent Chlamydia infection?

Under stressful conditions, remains in cell as RB
Downregulation of major outer membrane protein (MOMP),
Increased production of stress factors (hsp60, hsp10) -> chronic inflammation
Refractory to Abx

154

How is chlamydia treated?

Tetracycline, erythromycin common treatments
Erythromycin and amoxicillin used in pregnant women and infants

155

Are B-lactams effective against Chlamydia?

No - may drive infection into persistent state

156

Are men or women more likely to be asymptomatic Chlamydia carriers?

Women

157

What are Opa genes in Gonorrhea?

Outer membrane proteins -> opaque cell appearance
Involve in binding host cells - close contact, possibly invasion
Several Opa genes - constantly transcribed, only translated if start codon is in frame
CTCTTT segments added/ lost - may shift start codon out of frame - control mechanism of expression

158

Does infection with N.gonorrhoeae confer immunity?

No

159

Describe pathogenesis of Treponema pallidum

Infection: sexual contact w/ active lesion (primary or secondary)
Invasion of mucus membranes - multiplication and spread -> lymphatics
*systemic spread before primary lesion forms*
3-4 weeks: primary chancre forms and heals in 4-6 weeks
2-10 weeks after healing: 2ndary syph: fever, sore throat, rash, lesions on hands and feet and face
Clear infection or latency
Tertiary syph - months later: granulomatous lesions (gumma) of skin, bones, joints. Neurosyphilis, CV syph. organism rare in tertiary lesions.

160

When can a fetus become infected with T.pallidum? How diagnosed?

Infection can occur at any stage of pregnancy.
Fetal anti T.pallidum IgM is diagnostic

161

How does congenital syphilis usually present?

Normal at birth and for 3-8 weeks. then fail to thrive, rhinitis, pneumonia
25% mortality

162

What are P-pili, what do they bind? mannose sensitivity?

Primary virulence factor in Uropathogenic E.coli
Bind globobiose (glycosphingolipids) and P group antigens on RBC -> agglutination in lab
Mannose insensitive
Induces IL6,8, PMN chemoattractive -> inflammation

163

HIV treatment goals

Reduce moridity and improve survival
Restore and maintain immunologic function
Maximal, durable viral load suppression
Prevent vertical transmission (Mother -> child)
Improve quality of life

164

What is first line treatment for HIV?

2 NRTIs
1NNRTI
1 "boosted" PI
Raltegravir - integrase inhibitor

165

What is the preferred NNRTI used in HIV?

Efavirenz
except in 1st trimester of pregnancy or women with high pregnancy potential

Preferred alternative: Nevirapine

166

What is Ritonavir?

Is a protease inhibiting drug, but not used as such. Is a potent inhibitor of CYP3A4, which is used to extend the life of other protease inhibitors.
--BOOSTING

167

What is the preferred NRTI combo used in HIV treatment?

Tenofovir and Emtricitabine
-available as co-formulation

168

Uropathogenic E.coli virulence factors

P-pili
Type-1, Type-S fimbriae
Adhesins (AfaD, AfaE, Dr)
Toxins (Hemolysin, cytotoxic necrotizing factor-1)
K antigen
LPS (endotoxin)

169

What are S.saprophyticus virulence factors?

S.saprophyticus surface-associated protein (Ssp) - adhesin
Hemagglutinin / Fibronectin Binding Protein - adhesin
Hemolysin - not in all strains
Urease - stones

170

What is the etiology/ pathogenesis of S.saprophyticus?

UTI pathogen - cystitis, not pyelonephritis
Natural inhabitant of colon - self infection
More common in females
Sexual activity increases risk of UTI
Increased risk w/ spermicide nonoxynol-9

171

Klebsiella pneumoniae virulence factors in UTI

Type 1 and 3 fimbriae
Capsule
LPS
Urease

172

Proteus mirabilis virulence factors in UTI

MRP - mannose resistant proteus like hemagglutinin
PMF - proteus mirabilis fimbriae
flagella
urease - high concentration of ammonium - alkalinize urine, stones

173

What is Bile esculin used for?

Differentiation of Enterococcus from Streptococcus
Enterococcus grows - blackens medium

174

What are the virulence factors of Enterococcus in UTI?

Aggregation substance (Asa1)- plasmid exchg and adhesion
Cytolysin - lyse RBC -> iron for growth
Sex pheromone - Neutrophil chemoattractant (can enter PMN)

175

What are host defenses against UTI?

normal flora
flushing effect of urine
sloughing epithelium
high osmolality, low pH of urine
insignificant immune defense

176

In what infections should anti-GI motility agents not be used?

In infectious diarrhea w/ the following:
bloody diarrhea, Shiga-toxin producing E.coli, C.diff

177

How is Salmonella treated?

Treatment generally not recommended except extreme cases or certain morbidities
-Cipro, Amp/Amox, TMP/SMX, 3rd gen ceph, Azithro

**check susceptibility!**

178

Treatments for E.coli GI infection?

FQ, TMP/SMX, Cephalosporins
- usually 3 days
- check susceptibilities!!

179

V.cholera treatment?

1 dose - 300mg Doxycycline

180

Giardia treatment

-10 days of Metronidazole

181

Diarrhea in ped patients - avoid what drugs? What is preferred?

Tetracyclines and FQ
- TMP/SMX, penicillins / cephalosporins are better

182

What are the symptoms of CMV infection?

90% asymptomatic
Infectious mononucleosis, hepatitis, thrombocytopenia, myocarditis

183

What is the risk of transmission from pregnant mother to fetus of CMV?

40%

184

How is CMV isolated for testing and how is diagnosis made?

Virus isolated from buffy coat, urine, or cervical secretions
Tests used:
IgG titer (rapid 4x increase in specific titer)
PCR rapid diagnosis
Measurement of specific IgM (persists 4-8 months after infection)

185

What is the treatment for congenital CMV?

gancyclovir (IV)
or valgancyclovir (oral)

Not recommended if asymptomatic!!!

186

How is congenital CMV diagnosed?

virus isolated from saliva or urine in first 2 weeks of life

187

What are the symptoms of congenital CMV? Mortality rate?

10% asymptomatic
Petechiae, jaundice, hepatic and splenic enlargement, thrombocytopenia, conjugated hyperbilirubinemia
Neurologic abnormality: microcephaly, seizures, hypotonia, intracranial calcifications
Sensorineural hearing loss (30%)
Eye abnormalities
Neurodevelopmental delay
Dental abnormalities
15-30% mortality. Survivors: long-term sequelae

188

What are the symptoms of perinatal CMV infection?

Most subclinical / asymptomatic.
Most common illness is self-limited pneumonitis (severe if infant premature)

No long-term deficits

189

What are three ways in which neonatal HSV infections present?

SEM : skin, eyes, mucus membranes (40%)
Localized CNS involvement (w/ or w/o SEM) (34%) - seizures, lethargy, apnea. In CSF: pleocytosis, elevated protein
Disseminated: (22%) - adrenal glands, liver, kidneys, heart, etc. Mortality for disseminated - 55% (80% w/o therapy)

190

Treatment for neonatal HSV infection?

Acyclovir or vidarabine (unusual, but eye-drop formulation available)

191

Fetal Varicella syndrome

Occurs when mother contracts varicella (not shingles) in first 20 weeks of pregnancy (small risk - 1.2%)
- scarring of infant (cutaneous)
-hypoplastic extremities (usually unilateral, usually lower limbs)

192

Neonatal varicella

contracted from mother during last 3 weeks of preg
-If maternal infection occurs w/in 5 days before or 2 days after delivery - lesions at 5-10 days of age.

193

Neonatal varicella treatment

Acyclovir

If mother develops varicella 5 days before or 2 days after delivery - VZV Immunoglobin ASAP

194

What results from Parvovirus B19 infection?

20% asymptomatic
Fifth disease
Erythema infectosum - skin rash - slapped cheek
In adults - flu like, symmetric polyarthropathy
Chronic - anemia, transient aplastic crisis (virus shuts down RBC production - problematic in sickle cell patients)

195

Fetal Parvovirus B19 infecion

Can result in hydrops fetalis or death (risk cardiac dysfunction

196

Toxoplasma gondii infection

80-90% asymptomatic
may be flu-like - muscle aches, lymphadenopathy
responsible for 1-5% mononucleosis cases
Complications - myocarditis, hepatitis, encephalitis, deafness, pneumonia

Tissue bound cysts - latent phase of infection - life long

197

Treatment of maternal toxoplasmosis

spiramycin - attempt to prevent fetal infection

If fetal infection confirmed - folic acid antagonists - pyrimethamine and sulfadiazine

198

What organisms are most commonly responsible for sepsis neonatorum?

Group B strep
Coagulase neg staph
Other strep
E.coli
H.influenzae
C.albicans

199

In early onset GBS sepsis, what is the usual focus of inflammation?

Usually lungs
Meningitis can also occur

200

In late onset GBS sepsis, what is the focus of infection?

No focus of inflammation.
Bacteremia is most common presentation
followed by development of meningitis.

201

Common presentation and cause of mononucleosis

Fever, exudative mononucleosis, lymphadenopathy, hepatosplenomegaly, atypical lymphocytes in peripheral blood

Usually caused by EBV
Also CMV
T.gondii (1-5%)

202

Treatments for infectious mononucleosis

Bed rest in acute phase
Avoid sports until spleen is no longer palpable
Steroids may be used for some symptoms: massive splenomegaly, tonsillar swelling, hemolytic anemia, hemophagocytic syndrome

203

Describe the course of HHV-6

Incubation 9-10 days, transmitted via respiratory secretion
Roseola (exanthem subitem, sixth disease)
Fever >102deg F for 3-7 days then macular or papular rash for 2 days (spread from trunk outward)


204

What organism(s) cause Impetigo?

Usually Group A Strep
Also S.aureus

205

What causes scalded skin syndrome?

soluble exotoxin of S.aureus

206

What antibiotics are used for CA-MRSA?

Vancomycin - doesn't penetrate lungs
Daptomycin - limited lung pen. inactivated by surfactant
Linezolid
TMP/SMX
Clindamycin (~15% resistant)
Doxycycline/minocycline

207

What is Kawasaki disease?

Unknown etiology - vasculitis of all vessels most severely affecting med. sized arteries
Must have 4 of these:
-bilat. non-exudative conjnctival infections
-changes of oral mucosa
-changes of hands and feet
-rash
-cervical lymphadenopathy >1.5cm
AND
disease not explained by any other process
Presents with fever >39C, always cardiac involvement

208

How is Kawasaki disease treated?

IV Immunoglobin - 2/kg over 10-12 hrs.
repeated if fever persists
Aspirin 80-100 mg/kg/day divided q6 hrs.