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Flashcards in Micro 1 Deck (145):
0

What organisms naturally colonize the skin?

Yeast and gram + organisms

1

What organisms naturally colonize the large intestine?

Anaerobes - bacteroides (10^11 /g fecal mater)

2

What organisms naturally colonize the mouth?

anaerobes - density sim to lg. intestine

3

What organisms colonize the nose and pharynx?

Gram + and - cocci (Neisseriae and Moraxella)
Gram + rods (Corynebacterium)

The rest of the respiratory tract is sterile

4

What organisms normally colonize the urogenital tract?

Urethra - transiently colonized
Vagina - changes w/ age: gram + cocci (staph, strep) before puberty; Lactobacillus Acidophilus after puberty (reduces pH and maintains uniform flora)

5

What is the procedure for gram staining?

Heat fix
Crystal Violet - then rinse
Iodine - then rinse
Acetone or Isopropyl alcohol - then rinse
Safranin - rinse then dry

6

What is the mechanism of Gram staining?

Iodine - crystal violet complex is too large to wash out of gram +

7

Describe acid fast bacteria

Mycobacterium (TB)
Cell walls contain long chain fatty (mycolic) acids, do not gram stain well.
Stain w/ carbol fuchsin, decolorize w/ 3% HCl and ETOH - acid fast will remain red

8

What is lipoteichoic acid and where is it found?

Part of gram + cell wall - strengthens
Endotoxin - can evoke immune response from humans

9

Where are gram - toxins housed?

Periplasmic space - between inner cell membrane and peptidoglycan cell wall
ex: cholera toxin

10

Cell wall components

Disaccharide-pentapeptide subunits
N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM)
Peptide bridges between NAM cross link subunits (determine thickness of wall)
Gram +: pentaglycine links D-ala and lysine
Gram -: direct link between D-ala and diaminopimelic acid

11

What is mycolic acid?

Component of Acid Fast Bacteria cell wall
resistant to phagocyte killing and drying

12

What are components of gram - outer membrane?

Lipopolysaccharides (LPS) and phospholipids
LPS: virulence factor (endotoxin), mediates inflammation, septic shock
LPS composed of
-O antigen: repeating sugars - used for typing bacteria
-core sugars
-fatty acid moieties - bioactive portion of LPS

13

What is a bacterial capsule?

Both Gram + and - bacteria
High MW polysaccharides or amino acids
production depends on enviro and growth conditions
Virulence factor
Protection from complement mediated killing

14

What are pili and what are they made of?

proteinaceous structures extending from cell membrane
made of pilin, tipped w/ adhesins which bind host tissue (receptors) - virulence factor- antigenic
1. common type: mediate adhesion to host eukaryotic cells
2. sex type: join conjugating bacteria

15

What are flagella made of? Are they antigenic?

Flagellin
highly antigenic - H antigen

16

3 spore forming bacteria and assoc. diseases

clostridium tetani - tetanus
bacillus anthracis - anthrax
clostridium botulinum - botulism

17

How do Beta-Lactams work?

Inhibit final step of cell wall synthesis - transpeptidation by Penicillin Binding Proteins (PBPs)

18

What is the mechanism of penicillinase resistance in resistant penicillins?

Bulky side chains - sterically hinder B-lactamase binding

19

What coverage do beta-lactam / beta-lactamase inhibitor combo drugs offer?

Improved gram (-) and anaerobe
MSSA

20

What classes of bacteria are highly resistant to pecinillins?

aerobic gram - bacilli
anaerobes

21

What are beta-lactamase inhibitors?

Suicide inhibitors
Bind beta-lactamase -> inactive compound

22

What are common side-effects of Penicillin drugs?

Allergic reaction - from a rash to anaphylaxis
-may be due to B-lactam ring or to side chains

Acute Interstitial Nephritis - allergic rxn in kidney
-fever, rash, eosinophilia
-non-oliguric renal failure, may progress to anuria and kidney failure
-eosinophilic cells and tubular damage seen on biopsy

23

Probenecid

Gout medication given to prolong effect of Penecillin - blocks renal elimination
Used for persistent infections - syphillis

24

What do cephalosporins NOT have activity against?

Enterococcus

25

What drugs would most likely be used to treat community acquired intra-abdominal infections or for surgical prophylaxis?

2nd gen cephalosporins - cephamycins
Cefotetan or Cefoxitin

26

What is the drug of choice for community acquired pneumonia (s.pneumo)?

Cephtriaxone - 3rd gen cephalosporin

27

What are the SPICE organisms?

Serratia, Providencia, Indole (+) Proteus, Citrobacter, Enterobacter
-all have B-lactamase
-lab may say susceptible to 3rd gen Cephalosporin, but use may select resistant strain
-usually use cefepime or carbapenems

28

What cephalosporins have activity against anaerobic bacteria?

Cefotetan, Cefoxitin - 2nd gen (2B or GI) cephamycins

29

Ceftaroline

Advanced generation cephalosporin
Binds PBP2A and 2X
MRSA - first B-lactam w/ activity against.
Gram (-) activity between 2nd and 3rd gen

30

Cephalosporin / Penicillin cross-reactivity

Chance of those w/ penicillin allergy having allergy to cephalosporin
5-15% according to book, actually much lower (0-2%)
-may be due to lactam ring (unlikely) or side chains
--Ceftazadime and Aztreonam: identical side chains. Az billed as having no x-reactivity w/ Penicillins. If Cef allergic, probably Az allergic

31

What organisms are most commonly associated with ESBL?

ESBL - extended spectrum beta-lactamase
E.coli K.pneumoniae
Carbapenem is drug of choice

32

B-lactams and renal dosing

Almost all renally eliminated and need renal dosing adjustments
exceptions:
-Ceftriaxone
-Penicillinase resistant Penicillins

33

1st generation cephalosporins and what used for

Cephalexin, Cefazolin, Cefadroxil
Skin, lower UTI
Good gram +, Staph, MSSA, Strep (variable S.pneumoniae)
Bad gram -, no anaerobic activity
Not for use in neonates - bind Ca++ -> gallstones, biliary sludging

34

2nd Generation cephalosporins and what for

2A: Cephlacor, Cefuroxime - Respiratory infections
good gram(+), better S.pneumoniae,
2B: Cefotetan, Cefoxitin - cephamycins - GI infections *excellent for anaerobes*
community acquired intra-abdominal infections and surgical prophylaxis.

35

3rd generation cephalosporins and what used for

Ceftriaxone(IV), Cefotaxime, Cefixime, cefpodoxime(PO)
Ceftriaxone - *DOC for CAP*, *DOC for CAM* unless B-lactone resistant
Ceftazadime - Pseudomonas aeruginosa (PSA)
Excellent nosocomial gram(-)
Not great staph - quesionable MSSA
No PSA, no anaerobes
SPICE organisms - tendency to induce resistance

36

4th generation cephalosporins and what used for

Cefepime
Good gram (+): Strep, staph, MSSA
Good gram (-): excellent against nosocomial infections
SPICE organsism (Serratia, Providencia, indole (+) proteus, citrobacter, enterobacter)

37

Advanced generation cephalosporin and what used for

Ceftaroline
Binds PBP2A and PBP2X
MRSA coverage
better S.pneumoniae, ampicillin-sensitive E.faecalis
Gram(-) is between 2nd and 3rd gen. ability

38

What is ESBL and what are most common organisms encountered?

Extended Spectrum Beta-Lactamase
E.coli and K.pneumoniae - can be transferred to other enterobacteria
Renders resistance to all penicillins, cephalosporins and aztreonam
***Carbapenems are DOC*****

39

What are the carbapenems and what do they cover?

group 1: Ertapenem - DOC for ESBL organisms
good gram (+)
great gram (-) except APE: acinetobacter, PSA, enterobacter

group 2: Imipenem, Meropenem, Doripenem
good gram (+)
great gram (-): ESBL, PSA, A.Baumanii (decreasing effectiveness)
anaerobes: excellent, but no c.diff
**in general - used for multi-drug resistant organisms***

40

What do carbapenems not cover?

MRSA
ampicillin resistant enterobacteria
stenotrophomonasmaltophilia
KPC (carbapenemase)
C.diff (can cause c.diff)

41

What is the biggest side effect of carbapenems?

Seizures
Not likely, though.
Prob related to cilastatin (added to increase half-life)
More likely w/ high dose.
Cross-reactivity w/ penicillins 1-50%

42

Aztreonam

Used for empiric treatment of gram (-) organisms in patients w/ Penicillin allergy
PSA activity, but not great
No ESBL, no x-reactivity w/ penicillins

43

What drugs are useful against Acinetobacter baumannii?

DOC: ampicillin/sulbactam - given for sulbactam alone
Imipenem, Meropenem, Doripenem - decreasing effectiveness

44

How do aminoglycosides work?

Bind 30s ribosomal subunit - inhibit protein synthesis
BacterioCIDAL, concentration dependent killing (high dose preferred)
Oxygen dependent transport - so no activity vs. anaerobes
Note: no oral absorption, high conc. in urine - good for UTI

45

What are the individual aminoglycosides and what are they used for?

Gentamycin: staph and enterococcus in comb. w/ B-lactam
-also eye ointment
Tobramycin / Amikacin: Empiric nosocomial (double coverage)
-sometimes definitive as well. Ami: mycobacterial
Neomycin: Oral - GI decontam pre-op. Topical - neosporin
Streptomycin: enterococcal infection when gentamycin resistant.
-mycobacterial infection

46

Mechanisms of aminoglycoside resistance

1. Addition of side chains by Transferase enzymes - prevent drug binding
2. 30s modification
3. Efflux pumps / decreased porin production -> decreased intracellular concentration

47

Aminoglycoside adverse events

Nephrotoxicity - most common. Minimize trough concentrations
Vestibular/ Ototoxicity - assoc. w/ total drug exposure (irreversible)
Neuromuscular Blockade - additive w/ other drugs (myasthenia gravis)

48

What are the floroquinalone drugs and what are they used for?

Moxifloxacin, Levofloxacin, Ciprofloxacin, Gemifloxacin and Norfloxacin
Respiratory: Levo and Moxi: Excellent against all CAP
PSA: Cipro and Levo: also enteric gram (-)
Anaerobes: Moxi (some B.fragilis activity)

49

Floroquinolone side effects

CNS toxicity: headache, dizziness, insomnia, seizures
Damage to growing cartilage: no use w/ peds
Dysglycemia
Cardiac arrhythmia / torsades (min risk unless prone to arr. or on QT prolonging drugs - Moxi highest risk

50

What drug interactions are floroquinalones prone to

Chelation effect: Reduced absorption when taken w/ divalent cations (Ca++, Mg++, Fe++)

51

What is Red Man Syndrome?

Histamine response to rapid infusion of vancomycin - not a true allergic reaction
non-specific mast cell degranulation

infusion should not exceed 1g/hr. pretreatment w/ diphenhydramine

52

What are the treatment options for VRE?

Linezolid
Daptomycin
Quinupristin / dalfopristin (E. faecium only)
Tigecyclin (other tetracyclines maybe)

53

What is the mechanism of Vancomycin resistance in Enterococci and Staph A?

D-ala D-ala becomes D-ala D-lac or D-ser
Vancomycin can't bind

54

What is the "erm" gene?

Confers MLS resistance to S.aureus (Macroside, Lincosamide, Streptogramin)
- all 3 work at same ribosome site
If isolate says erythromycin resistant and clindamycin susceptible
D test to check for MLS before using clindamycin

55

How do you deal with yeast in the blood?

Confirm not at risk for Cryptococcus (immunosuppressed, HIV)
Is almost always Candida
-Albicans > Glabrata
Risk for fluconazole resistance?
-recent exposure or known colonizer of C.glabrata
Critically ill?
Yes -> Echinocandin
No -> Fluconazole

56

What mechanisms do microorganisms employ to avoid ciliary action of the respiratory system?

Development of strong adhesins
-Rhinovirus: capsid protein attaches to ICAM-1
-Mycoplasma pneumonia attaches to neuraminic acid on host respiratory epithelium
Paralysis of ciliary action
-Bordatella pertussis - tracheal cytotoxin
-Influenza virus -> ciliated cell disfunction

57

What organisms are most associated with skin infections?

S. aureus
S. pyogenes

58

What is impetigo?

Skin infection commonly caused by S.aureus or S.pyogenes
More common in children
Intraepithelial vesicles w/ surrounding erythema - weeping yellow crusty lesions.
Patients irritable, uncomfortable, afebrile
S.pyogenes infections can lead to glomerulonephritis

59

What is Erysipelas?

Skin infection usually caused by Streptococcus pyogenes - involves epidermis and dermis
Bright red, inflamed w/ sharp borders, painful. Usually face and lower limbs. Patients often febrile

60

What is cellulitis?

Skin infection usually caused by S.aureus involving epidermis, dermis, and subcutaneous tissue
Patients often febrile, involved skin is edematous, erythmatous, warm, tender, and painful with bullae common. Ecchymosis

61

What is a carbuncle?

Multiple furuncles in a confined area forming a large confluent, suppurative infection.
Patients are often acutely ill and require surgery and systemic antibiotics

62

What organisms are involved in fasciitis and myonecrosis?

Strep pyogenes, Staph aureus, Vibrio vulnificus (if seawater exposure), Clostridia (gas gangrene)

63

What causes Scarlet Fever?

Strep pyogenes - primary infection in pharynx - sore throat
Streptococcal pyrogenic exotoxins produced
strawberry tongue, diffuse rough red rash, desquamation of skin on recovery

64

What is the cause of Toxic Shock Syndrome?

S. aureus produces TSST-1 (toxin) during infection on minor skin wound, female genital tract (tampon), post-influenza pneumonia.
Hematogenous spread of toxin -> very high fever, hypotension, multi-organ damage, diffuse erythmatous rash

65

What usually causes hot tub folliculitis?

Psuedomonas infect dilated pores in under-chlorinated hot tub.

66

What organism is associated with animal bites?

Pasturella multocida
Penicillin works well.

67

What causes Whitlow?

Herpes symplex virus - finger infection assoc. with healthcare workers, esp. dentists.

68

What organism causes gangrene?

Clostridium spp

69

Cowdry Type A nuclear Inclusion - suggestive of what?

Herpes Symplex Virus - if seen in a cervical smear
or
Cytomegalovirus - if seen in respiratory cell

70

binucleate epithelial cells with perinuclear halo is suggestive of what?

papilloma virus

71

Staphylococcus virulence factors

alpha toxin: Complement like pore forming cytolysin - kills erythrocytes and leukocytes.
TSST-1: exotoxin. super-antigen cross-links Tcell receptor to MHC class II of host -> cytokine release.
Exfoliative toxins (scalded skin syndrome): intercellular splitting at desmosome
Exoproteins - allow spreading: hyaluronidase (hydrolyzes CT) staphylokinase (fibrinolysis)
Antiphagocytics: Protein A (binds Fc), Coagulase (surface polymerization of fibrin - resist phagocytosis), Catalase (resist H2O2)

72

What is quorum sensing?

Alteration of gene expression according to density of local cell population
Staph a.
- upreg. coagulase at low cell density - colonization
- upreg. staphylokinase at high density - spread

73

Scalded skin syndrome

Caused by staph a. exfoliative toxin in neonates and children.
Bullous impetigo is localized SSS

74

Staph aureus identification

gram + cocci in clusters
positive catalase (diff. from strep)
positive coagulase (diff staph epidermidis and staph saprophyticus)

75

Virulence factors of strep pyogenes

M protein: mediates binding to epidermis. anti-phagocytic. variable. cross-reactive Ab -> glomerulonephritis
Protein F: adhesin - mediates fibronectin binding at wound site
Streptolysins O and S - cause B- hemolysis on blood agar
SLO: oxygen labile, sulfhydryl activated cytolysin. Antibodies against -> self immunity
Streptococcal pyrogenic exotoxins (Spe A-C): Superantigens
-Spe A produced by bacteriophage carrying Grp. A Strep
-induce cytokine release -> fever, rash, Tcell stim, endotoxin sensitivity -TSST like
Hydrolytic enzymes - responsible for thin runny pus
streptokinase dissolves fibrin,

76

What is post-streptococcal glomerulonephritis?

Caused by cross-reaction with M-protein
-M-protein / Ab immune complexes deposit in glomerulus
Edema, hypertension, hematuria, proteinurina about 3 weeks post-infection
Rare in US. More in developing countries

77

What causes Toxic Shock-like syndrome?

Group A strep
Streptococcal pyrogenic exotoxin A is responsible - SUPERANTIGEN
Fever, hypotension, rash, renal impairment, respiratory failure, diarrhea

78

Streptococcus pyogenes identification

gram + cocci in chains
B-hemolytic on blood agar (SLO, SLS)
Pyogenic
Catalase negative
Lancefield group A antigen

79

What is propionibacterium?

Causes acne
predominant anaerobe of normal skin flora
breaks down lipids in sebum
Acne vulgaris - inflammation of hair follicle associated with sebaceous glands
keratin + sebum + bacteria -> blackhead
can cause infections in severely immunocompromised
endocarditis, contam prosthetic valves, cerebrospinal shunts
can contam blood cultures - must diff. from true pathogen

80

Pasteurella multocida

animal bite bacteria
gram - rod

81

Clostridium perfringens

Gram + rod, anaerobic, spore producing
gas gangrene

82

Clostridium Tetani

Gram + rod, spore producing, anaerobic
Tetanus

83

What is indicated by chronic candidiasis

Tcell deficiency

84

Sporothrix shenckii

Causes sporotrichosis - subQ infection
Fungal infection after thorn prick or gardening injury - causes pyogenic and granulomatous reaction

85

What are Dermatophytes?

Fungi that commonly infect skin -> tinea
-epidermophyton, trichophyton, microsporum
->ringworm, athlete's foot, jock itch
Invasion of nail bed -> malformed growth

86

What are the alphaherpesviruses?

HSV1,2 and Varicella-Zoster Virus

87

What are the betaherpesviruses?

Human Herpes Virus 6 (A and B),7 and Cytomegalovirus

88

What are the gammaherpesviruses?

Epstein-Barr Virus, Human Herpes Virus 8 (Karposi's Sarcoma assoc. Herpesvirus)

89

What is the structure of Herpes Symplex Virus?

Large encapsulated (icosahedral) DNA virus (dsDNA)
152k BPs, 70-80 genes

90

3 phases of viral gene expression

Immediate gene expression : adapt cell for virus replication
Early gene expression: vDNA replication
Late gene expresson: structural proteins

91

What do antiherpes virus drugs require for activation? What is method of action?

Phosphorylation by virus encoded thymodine kinase
acyclovir -> acyclovir monophosphate
cellular kinases -> acyclovir triphosphate -> inhibition of virus encoded DNA polymerase
- triphosphorylated drug embeds in viral DNA acting as chain terminators.

92

Where are latent VZV infections established?

Dorsal Root Ganglion

93

What cells are infected by beta herpesviruses?

HHV 6A and B: Tcell tropic. Also monocytes and macrophages
Cytomegalovirus: myeloid cells.

94

Exanthm subitem

Roseola - common childhood infection
Caused by HHV 6B, sometimes 7.
Fever and rash on trunk and face spreading to legs.
Complications: fever >40C, neurological involvement - seizures, aseptic meningitis, hepatitis, mono-like symptoms

95

What disease is HHV 8 associated with?

Kaposi's sarcoma
usually older men of mediterranean ancestry and HIV patients

96

Papillomavirus morphology

Non-enveloped icosahedral - small
circular dsDNA (8-10 genes)

97

HPV-16 transforming genes and major capsular protein

E6: p53 tumor suppressor protein destruction
E7: Inactivation of Rb tumor suppressor protein

L1 protein: major surface marker - target for antiviral Ab and component of Gardasil HPV vaccine

98

What HPV viruses are most closely associated with cervical cancer?

HPV 16 and 18
-relatively uncommon

99

2 HPV vaccines and approved ages for admin.

Gardasil - age 9 - 26 (types 6,11, 16, 18)
Cervarix - age 10-15 (types 16, 18)

100

Picornaviurs - description and example

Small, non-enveloped, single strand +RNA
Coxsackievirus: tends to occur in outbreaks
-hand, foot and mouth
-most common source of aseptic meningitis

101

What is coxsackie virus?

Picornavirus
Prone to occur in outbreaks - most common in infants and children
Hand food and mouth disease, aseptic meningitis
- fever, sore throat, headache, anorexia
- vomiting and convulsions - usually in children
- w/in 2 days - lesions of mouth, tonsils, soft palate
- healing in 1-5 days
faster resolution than HSV

102

Necotizing fasciitis is most commonly associated with what organism?

S.pyogenes
also - CA-MRSA (does not respond to methacillin or cefazolin normally given for skin infections)

103

In presentation of scalded skin syndrome there is the presence of large vessicles or bullae. What organism is likely? What is less likely?

More likely: S.aureus
Less likely: S. pyogenes

104

If a person develops blistering dermatitis after swimming in the ocean, what organism would be of concern?

Vibrio
-also assoc. w/ raw or undercooked oysters
-high mortality rate

105

What is the treatment for impetigo?

Topical abx (mupirocin) or oral abx

106

What is dermatitis/arthritis syndrome?

Dermatitic lesions with accompanying joint pain
-in sexually active young adult - Think Neisseria gonorrhoeae
-spreads through lymph and blood

107

What antibacterials are known for false elevation of creatinine, elevated INR (w/ warfarin), and hyperkalemia?

Sulfamethoxazole
Trimethoprim - hyperkalemia

SMX/TMP = Bactrim

108

How is Viridians Strep identified?

Blood culture
Gram +
Lacks lancefield group and any specific surface markers
Biochemical testing for definitive identification

109

How are Group D strep and enterococci clinically identified?

Blood culture
Gram +, catalase -
Serologic test for group D antigen
Enterococci grow in 6.5% NaCl, hydrolyze esculin in 40% bile

110

How is candida identified in the lab in the setting of a systemic or blood stream infection?

Blood culture
KOH or Gram stain - budding round oval yeast cells w/ hyphae

111

How is aspergillus identified in the setting of a systemic or bloodstream infection?

Blood culture returned negative
Biopsy of infected tissue
Aspergillus cultured in lab - branched septate hyphae

112

Describe the plasmodium lifecycle

Anopheles mosquito bites host
Sporozoite -> blood -> Liver - form schizont - asexual reproduction -> merozoite -> blood
Merozoite enters RBC: Trophozoite -> schizont -> merozoite -> cell ruptures
Some cells for gametocytes -> mosquito for sexual reprod.

113

What is a hypnozoite?

Dormant form of Plasmodium
-P.vivax, P.ovale only
-responsible for long term relapses.

114

What are the erythrocyte receptors for P.vivax and P.falciparum?

P.vivax: Duffy receptor on reticulocyte
P.falciparum: glycophorin A on all red cell types.

115

How is malarial fever induced?

Produced by asexual blood schizont. RBC ruptures -> release of:
-malarial metabolites, hemozoin (from hemoglobin): pyrogenic, antigenic,
-cytokines: IL-1, TNF
Fever is initially sporadic, then cyclical corresponding w/ parasitic replication cycles (48-72 hour bouts)

116

What is the effect of HbS on the spleen?

Person can become functionally asplenic -> increased susceptibility to encapsulated bacteria

117

What provides natural resistance to malaria?

Lack of Duffy receptor (P.vivax)
HbS heterozygous
HbC
- cells prevent parasite from rearranging actin to form adhesin -> decreased 'stickiness' of infected erythrocyte.

118

How are plasmodia organisms identified in clinical practice?

Blood smears
-thick smear: diagnose parasitemia
-thin smear: identify Plasmodia species
ELISA: Ab detection
gene probes, PCR for P.falciparum

119

How is Babesia microti spread?

Tick-bourne.

1-4 week incubation. Usually flu-like: Fever, myalgia, hepatosplenomegaly, hemolytic anemia,renal dysfunction
Spontaneous resolution in a few weeks.
Can be life threatening in asplenic patients.

120

What organism is the main cause of eye infections?

S. aureus

121

Infection of eyelid margin / sebaceous gland

Blepharitis

122

Inflamation of lacrimal sac

Dacrocystitis

123

Infection of aqueous or vitreous humor

Endophthalmitis

Requires ulceration or penetrating injury to compromise cornea and sclera

124

How is S.pneumoniae identified clinically?

Gram stain: gram +, lancet shaped diplococci
No Lancefield grouping
Capsular serotyping
Quelling reaction - anti-capsule Ab -> capsular swelling
Optochin (P disk) susceptibility

125

Hib vaccine

for Haemophilus influenzae b - most virulent strain
-given to infants (@2 mos) since 1990

126

How is H.influenzae identified in a clinical setting?

Gram (-) rod - very small
Requires blood products for growth (grows on chocolate, but not blood agar)
Hematin (X factor) and/ or NAD (V factor) needed for growth

127

How does Pseudomonas aeruginosa Exotoxin A work?

ADP-ribosylation of Elongation Factor 2
NAD + EF2 ADPribose-EF2 (inactive) + nicotinamide + H+
**same activity as diphtheria toxin**

Inactivates protein synthesis - promotes tissue invasion and evasion of immune response.

128

What is the primary cause of corneal penetration in a Pseudomonal eye infection?

Elastase
protease works on elastin, IgG, IgA, collagen, complement

129

How is pseudomonas identified in a clinical setting?

Gram - rod, motile on wet mount
Mostly aerobic, but facultative anaerobe
Fruity odor on solid media
Blue-green fluorescence under UV light (phyocyanin, pyoverdin)
High levels of cytochrome oxidase - pos. oxidase test

130

Trachoma

caused by Chlamydia trachomatis - chronic follicular conjunctivitis
Usually passed mother - child, mostly in less developed african/asian countries
Trichiasis - inward growth of eyelashes - corneal scraping
Recurrent infection, roughening of inner eyelid, can produce blindness

131

Diseases caused by Histoplasma capsulatum

Chorioretinitis - disseminated disease from primary respiratory infection
Presumed Ocular Histoplasmosis Syndrome - small areas of inflamation and scarring of retina - circular - if affects macula may produce blind spot

132

How is Histoplasma capsulatum identified?

Very slow growth on blood agar or Sabouraud agar from blood culture
Usually via biopsy- culture and identify bimorphic fungus

133

What is the drug of choice for Lyme disease?

Doxycycline

134

What valve of the heart is most frequently involved in endocarditis?

Mitral - L. side of heart: more pressure -> more turbulence
M - 28-45%
Aortic - 5-36%
M&A combined - 0-35%
Tricuspid - 0-6%
Pulmonic - <1%

135

What organisms are most frequently involved in bacterial endocarditis?

80% aerobic gram (+): S.viridians, S.aureus, enterococcus, etc.
20% unusual others: E.coli, yeast

136

What is mycotic aneurism?

Aneurysm due to infection - complication of infective endocarditis.
-occur at bifurcation points
-bacteria from IE - direct invation, embolic occlusion, or immune complex deposition

137

What are conjunctive petechiae?

Marker of acute endocarditis
small pieces of vegetation break off - embolize in small vessels of conjunctiva

138

What are Osler's Nodes and Janeway's Lesions?

Both appear on hands and feet of individuals w/ infective endocarditis
Osler's: caused by immune complex deposition -> inflamation / necrosis. Painful.
Janeway: caused by septic emboli - microembolism - flat, necrotic, painless.

139

What abnormal lab results are associated with infective endocarditis?

Anemia - 70-90%
Thrombocytopenia - 5-15%
Leukocytosis - may be absent
Elevated sedimentation rate -almost always (70-90%)

140

How are blood cultures ordered in the setting of suspected infective endocarditis?

3 sets over the course of 24 hours - each a separate venopuncture

141

What is HACEK group endocarditis?

infective endocarditis caused by: Haemophilus aphrophilus, Actinobacillus actinomycetemcomitans, Cardiobacterium hominus, Eikinella corrodens, Kingella kingae

Sub-acute course. Fastidious - req. 2-3 weeks to grow.
If suspected, give lab special instructions - suppliment media and hold cultures longer

142

What is the most common cause of osteomyelitis?

S. Aureus

143

What is the preferred therapy for an animal bite? IV and PO
What about penicillin allergic patient?

IV: ticarcillin / clavulanic acid
PO: Amoxicillin/clavulanic acid

Penicillin allergic: Doxycycline, Moxifloxacin

144

What is the treatment for bone/joint pseudomonal infection. How long?

IV B-lactam, 4 weeks joint, 6 weeks bone
Use Aminoglycoside (G,T, A) or FQ (Cip, Lev) for 2 weeks