Flashcards in Microbiology Bacteria - First Aid Deck (357)
Function of Peptidoglycan
gives rigid support, protects against osmotic pressure
Composition of Peptidoglycan
sugar backbone with peptide side chains cross-linked by transpeptidase
Cell wall/cell membrane (gram positives) function
major surface antigen
Cell wall/cell membrane composition
peptidoglycan for support; lipoteichoic acid that induces TNF and IL-1
Outer membrane (gram negatives) function
site of endotoxin (lipopolysaccharide (LPS)): major surface antigen
Lipid A induces TNF and IL-1; O polysaccharide is the antigen.
Plasma membrane function
site of oxidative and transport enzymes
Plasma membrane composition
50S and 30S subunits
space between the cytoplasmic membrane and outer membrane in gram negative bacteria
contains many hydrolytic enzymes, including beta-lactamases
protects against phagocytosis
polysaccharide (except Bacillus anthracis which contains D-glutamate)
mediate adherence of bacteria to cell surface; sex pilus forms attachment between 2 bacteria during conjugation
resistant to dehydration, heat and chemicals
keratin-like coat; dipicolinic acid; peptidoglycan
consists of a variety of genes for antibiotic resistance, enzymes and toxins
mediates adherence to surfaces, especially foreign surfaces (indwelling catheters)
Circular (coccus) gram positives
Circular (coccus) gram negatives
Rod (bacillus) gram positives
Mycobacterium (acid fast)
Gardnerella (gram variable)
Rod (bacillus) gram negative enterics
Rod (bacillus) gram negative respiratory
Rod (bacillus) gram negative zoonotics
Branching filamentous gram positive
Nocardia (weakly acid fast)
Pleomorphic gram negatives
Spiral gram negatives
No cell wall
Mycoplasma (does not gram stain)
sterols and has no cell wall.
mycolic acid and has a high lipid content.
These bugs do not gram stain well:
Treponema does not gram stain well becasue...
it is too thin to be visualized.
Mycobacteria does not gram stain well but its...
high lipid content in cell wall is detected by carbolfuchsin in acid-fast stain.
Mycoplasma does not gram stain well because...
it has no cell wall.
Legionella pneumophila does not gram stain well because...
it is primarily intracellular.
Rickettsia does not gram stain well because...
it is an intracellular parasite.
Chlamydia does not gram stain well becasue....
it is an intracellular parasite and lacks muramic acid in the cell wall.
Treponemes can be visualized with...
dark-field microscopy and fluorescent antibody staining.
Legionella can be visualized with...
(Certain Bugs Really Try my Patience)
PAS (periodic acid-Schiff) stain
stains glycogen, mucopolysaccharides
PAS stain is used to diagnose...
Whipple disease (Tropheryma whipplei).
Ziehl-Neelson (carbol fuchsin) stain
acid-fast organisms (Nocardia, Mycobacterium)
India Ink Stain
Cryptococcus neoformans (mucicarmine can also be used to stain the thick polysaccharide capsule red)
Media used for H. influenzae
chocolate agar w/ factors V (NAD+) and X (hematin)
Media used for N. gonorrhea and N. meningitidis
Thayer-Martin (VPN) with Vancomycin, Polymyxin and Nystatin
In the VPN media, Vancomycin acts to...
inhibit gram-postitive organism. Polymyxin inhibits gram-negative except for Neisseria. And Nystatin inhibits fungi.
Media used for Bordetella pertussis
Bordet-Gengou (potato) agar
Media used for C. diptheriae
Media used for M. tuberculosis
Media used for M. pneumoniae
-Eaton agar, requires cholesterol
Media used for lactose fermenting enterics
pink colonies on MacConkey agar
(fermentation produces acid, turning the colony pink)
E. coli is also grown on...
eosin-methylene blue (EMB) agar as colonies with green metallic sheen.
Media used for Legionella
Charcoal yeast extract agar buffered with cysteine and iron
Media for fungi
Obligate aerobes use...
O2-dependent system to generate ATP.
Examples include Nocardia, Pseudomonas aeruginosa and Mycobacterium tuberculosis.
Reactivation of M. tuberculosis (after immune compromise or TNF-alpha inhibitor use) has a predilection for...
the apices of the lung, which have the highest PO2.
P. aeruginosa is an aerobe seen in...
burn wounds, diabetes complications, nosocomial pneumonia and pneumonias in CF pts.
Examples of Obligate Anaerobes
Obligate Anaerobes lack...
catalase and/or superoxide dismutase and are thus susceptible to oxidative damage.
Obligate Anaerobe general features
-foul smelling (short-chain fatty acids)
-difficult to culture
-produce gas in tissue (CO2 and H2)
Anaerobes are normal...
flora in the GI tract and pathogenic elsewhere.
The antibiotic that is ineffective against anaerobes is...
aminoglycosides because this antibiotic requires O2 to enter the bacterial cell.
Obligate intracellualar bugs are...
Rickettsia and Chlamydia because they can't make their own ATP.
Facultative intracellular bugs are...
(Some Nasty Bugs May Live FacultativeLY)
Encapsulated Bacteria Examples
group B Strep
Capsule + protein conjugate serves as...
an antigen in vaccines.
Encapsulated bacteria are normally...
opsonized and then cleared by the spleen. Asplenics have decreased opsonizing ability and are at risk for severe infection.
All asplenics should receive...
s. pneumoniae, H. influenzae and N. meningitidis vaccines.
Catalase acts to...
degrade H2O2 before it can be converted to microbicidal products by myeloperoxidase.
People with chronic granulomatous disease (NADPH oxidase deficiency) have...
recurrent infections with catalase + organisms.
Examples of Catalase + organisms
(You need PLACESS for your cat.)
Some vaccines containing polysaccharide capsule antigens are conjugated to a carrier protein, which....
enhances immunogenicity by promoting T-cell activation and subsequent class switching.
A polysaccharide antigen alone cannot be presented to...
pneumococcal conjugate vaccine (Prevnar)
pneumococcal polysaccharide vaccine with no conjugated protein (Pneumovax)
Hib and meningococcal vaccines are both...
Urease positive bugs
(CHuck Norris hates PUNKSS)
Pigment producing bacteria
Actinomyces produces pigment that is...
yellow "sulfur" granules whcih are composed of filaments of bacteria
S. aureaus produces a...
Pseudomonas aeruginosa produces a...
Serratia marcescens produces a...
binds Fc region of IgG; prevents opsonization and phagocytosis
Protein A is expressed by...
IgA protease is...
an enzyme that cleaves IgA.
IgA protease is secreted by...
S. pneumoniae, Hib, and Neisseria in order to colonize respiratory mucosa.
M protein helps...
prevent phagocytosis and is expressed by group A strep.
Source of exotoxin
certain species of some gram-postivive and gram-negative bacteria
Source of endotoxin
outer cell membrane of most gram-negative bacteria
Chemistry of exotoxins
Chemistry of endotoxins
Lipopolysaccharide (structural part of bacteria, released when lysed)
location of genes of exotoxins
plasmid or bacteriophage
location of genes of endotoxins
toxicity of exotoxin
toxicity of endotoxin
clinical effects of endotoxin
fever, shock, DIC
Mode of action of endotoxin
induces TNF, IL-1 and IL-6
Antigenicity of Exotoxin
induces high-titer antibodies called antitoxins
Antigenicity of Endotoxin
Vaccines of exotoxins
toxoids used as vaccines
Vaccines of endotoxins
no toxoids formed and no vaccines available
Heat stability of exotoxins
destroyed rapidly at 60 C (except staph enterotoxin)
Heat stability of endotoxins
stable at 100 C for 1 hr
Typical diseases of exotoxins
Typical diseases of endotoxins
Sepsis by gram-negative rodsCory
Corynebacterium diphtheriae exotoxin
Diphtheria toxin inactives elongationg factor 2 (EF-2) causing pharyngitis with pseudomembranes in the throat and severe lymphadenopathy (bull neck).
Pseudomonas aeruginosa exotoxin
Exotoxin A inactivates EF-2 leading to host cell death.
Shiga toxin inactivates 60S ribosome by removing adenine from rRNA leading to GI mucosal damage (dysentery); ST also enhances cytokine release (HUS).
Shiga-like toxin inactivate 60S ribosome by removing adening from rRNA leading to cytokine release (HUS).
EHEC is different from Shigella because...
it does not invade host cells.
Heat-labile toxin (LT)
Heat-stable toxin (ST)
ETEC LT toxin
overactivates adenylate cyclase (increase cAMP) leading to increaesd chloride secretion in the gut and H2O efflux
ETEC ST toxin
overactivates guanylate cyclase (increases cGMP) leading to decreased resorption of NaCl and H2O in the gut
Manifestation of ETEC exotoxins
Bacillus anthracis exotoxin
Edema factor mimics the adenylate cyclase enzyme (increases cAMP). This is likely responsible for edematous borders of black eschar in cutaneous anthrax.
Vibrio cholerae exotoxin
Cholera toxin overactivates adenylate cyclase by permanently activating Gs leading to increased chloride secretion in the gut and H2O efflux. Manifestation is voluminous "rice-water" diarrhea.
Bordetella pertussis exotoxin
Pertussis toxin overactivates adenylate cyclase (increased cAMP) by disabling Gi, impairing phagocytosis to permit survival of the microbe.
Manifestation of the pertussis toxin
whooping cough: child coughs on expiration and "whoops" on inspiration
Clostridium tetani exotoxin
Tetanospasmin cleaves SNARE proteins required for NT release. Toxin prevents release of inhibitory (GABA and glycine) from Renshaw cells in the spinal cord.
Manifestation of the Tetanospasmin toxin
Clostridium botulinum exotoxin
Botulinum toxin cleaves SNARE proteins required for NT release. Prevents release of stimulatory (ACh) signals at NMJs leading to flaccid paralysis.
Manifestations of Botulinum toxin
Diptheria toxin, Exotoxin A, Shiga toxin, Shiga-like toxin, Heat-labile toxin, Cholera toxin and Pertussis toxin are all...
ADP ribosylating A-B toxins. The B component binds to host cell surface receptor enabling endocytosis. The A component attaches ADP-ribosyl to disrupt host cell prtoeins.
Clostridium perfringens exotoxin
Alpha toxin is a phospholipse (lecithinase) that degrades tissue and cell membranes.
Manifestation of Clostridium perfringens alpha toxin
degradation of phospholipids leads to myonecrosis ("gas gangrene") and hemolysis ("dobule zone" of hemolysis on blood agar)
Streptococcus pyogenes exotoxin
Streptolysin O is a protein that degrades cell membranes
Manifestation of Streptolysin O
contributes to beta-hemolysis
host antibodies against toxin (ASO) are used to diagnose rheumatic fever
Staphylococcus aureus exotoxin
Toxic shock syndrome toxin (TSST-1) brings MHC II and TCR in proximity to the outside of an antigen binding site to cause an overwhelming release of IFN-gamma and IL-2 leading to shock.
Manifestation of TSST-1 and Exotoxin A
Toxic shock syndrome: fever, rash, shock
Other toxins of Staph aureus cause...
scalded skin syndrome (exfoliative toxin) and food poisoning (enterotoxin).
Strep pyogenes exotoxin
Exotoxin A brings MHC II and TCR in proximity to the outside of an antigen binding site to cause overwhelming release of IFN-gamma and IL-2 leading to shock.
ability to take up DNA from the environment; seen in S. pneumoniae, Hib and Neisseria
F+ x F- Conjugation
F+ plasmid contains genes required for sex pilus and conjugation. Bacteria without this plasmid are termed F-. Plasmid (dsDNA) is replicated and transferred through the pilus from the F+ cell. There is no transfer of chromosomal genes.
Hfr x F- conjugation
F+ plasmid can become incorporated into bacterial chromosomal DNA, termed high-frequency recombination (Hfr) cell. Replication of incorporated plasmid DNA may include some flanking chromosomal DNA. Transfer of plasmid and chromosomal genes.
Segment of DNA (transposon) that can "jump" can transfer genes from plasmid to chromosome and vice versa.
Examples of transposition include...
antibiotic resistance gene on R plasmid.
Lytic phage infects bacterium leading to cleavage of bacterial DNA. Parts of bacterial chromosomal DNA becom packaged in viral capsid. Then the phage infects another bacterium, transferring the genes.
Lysogenic phage infects bacterium; viral DNA incorporates into bacterial chromosome. When phage DNA is excised, flanking bacterial genes may be excised with it. DNA is then packaged into phage viral capsid and can infect another bacterium.
Genes for the following 5 bacterial toxins are encoded in a lysogenic phage:
1. ShigA-like toxin
2. Botulinum toxin
3. Cholera toxin
4. Diphtheria toxin
5. Erythrogenic toxin of S. pyogenes
Staph saprophyticus is resistant.
Staph epidermidis is sensitive.
Strep viridans is resistant.
Strep pneumoniae is sensitive.
group B strep are resistant
group A strep are sensitive
Alpha-hemolytic bacteria form...
a green ring around colonies on blood agar
Alpha-hemolytic bacteria include:
Beta-hemolytic bacteria form...
a clear area of hemolysis on blood agar.
Beta-hemolytic bacteria include...
Staphylococcus aureus features
-gram positive cocci in clusters
-Protein A (binds Fc-IgG, inhibiting complement activation and phagocytosis)
-commonly colonizes the nose
Staph aureus causes (3):
1. inflammatory disease
2. Toxin-mediated disease
3. MRSA infection
Inflammatory diseases of Staph aureus
-pneumonia (often after virus infxn)
MRSA infection is an important cause of...
serious nosocomial and community acquired infections; resistant to methicillin and nafacillin because of altered penicillin binding protein (PBP).
Use of vaginal or nasal tampons predisposes to...
toxic shock syndrome.
S. aureus food poisonin is due to...
ingestion of a preformed toxin (that is not destroyed by cooking). Short incubation (2-6 hrs).
S. aureus is able to form a...
fibrin clot around itself leading to abscess.
Staphylococcus epidermidis infects...
prosthetic devices and IV catheters by producing adherrent biofilms
S. epidermidis is a normal part of...
skin flora and can contaminate blood cultures.
Staphylococcus saprophyticus is the second most common cause of...
uncomplicated UTI in young women.
Streptococcus pneumoniase is the most common casue of:
2. Otitis media
Strep pneumoniae features
-lancet-shpaed, gram-positive diplococci
Pneumococcus is associated with...
sepsis in sickle cell anemia
Strep pneumoniae has no virulence without..
Viridans strep features
-normal flora of the oropharynx
Viridans group strep causes...
dental caries (S. mutans)
bacterial endocarditis (S. sanguinis)
S. sanguinis makes...
dextrans which bind to fibrin-platelet aggregates on damaged heart valves.
Streptococcus pyogenes (Group A) causes...
pyogenic, toxigenic and immunologic diseases.
Pyogenic diseases of S. pyogenes
Toxigenic diseases of S. pyogenes
-toxic shock-like syndrome
Immunologic diseases of S. pyogenes
Antibodies to M protein enhance...
host defenses against S. pyogenes but can give rise to rheumatic fever.
Recent S. pyogenes infection is detected by...
JONES criteria for Rheumatic Fever
Impetigo more commonly precedes...
glomerulonephritis than pharyngitis.
scarlet rash w/ sandpaper-like texture; strawberry tongue, circumoral pallor
(caused by S. pyogenes)
Streptococcus agalactiae (group B) features
-colonizes the vagina
-causes pneumonia, meningitis and sepsis mainly in babies
-Hippurate test +
S. agalactiae produces...
CAMP factor which enlarges the area of hemolysis formed by S. aureus.
Pregnant pts with a positive screen for S. agalactiae at...
35-37 wks should receive intrapartum penicillin prophylaxis.
Enterococci (group D strep) features
-normal colonic flora
-penicillin G resistant
-cause UTI, biliary tract infections and subacute endocarditis
Lancefield grouping of streptococci is based on...
differences in the C carbohydrate on the bacterial cell wall.
VRE (vancomycin-resistant enterococci) are an important cause of...
Lab test for enterococci
can grow in 6.5% NaCl and bile
Streptococcus bovis (group D streptococci)
colonizes the gut; can cause bacteremia and endocarditis in colon cancer pts
Bovis in the blood =
cancer in the colon
Corynebacterium diphtheriae causes...
diphtheria via exotoxin encoded by Beta-prophage.
Symtpoms of diptheria
-pseudomembranous pharyngitis (grayish-white membrane)
Lab diagnosis of C. diphtheriae is based on...
gram-positive rods with metachromatic (blue and red) granules and Elek test for toxin.
(shaped like a club)
Diphtheria can be prevented with...
a toxoid vaccine.
C. diphtheriae show black colonies on...
Some bacteria can form spores at the end of the...
stationary phase when nutrients are limited.
Spores features (3)
-highly resistant to heat and chemicals
-have dipicolinic acid in their core
-no metabolic activity
To kill spores, you must...
autoclave them by steaming at 121 C for 15 min.
Spore forming gram positive bacteria found in soil (3)
1. Bacillus anthracis
2. Clostridium perfringens
3. Clostridium tetani
Other spore formers inlcude (3):
1. B. cereus
2. C. botulinism
3. Coxiella burnetii
Clostridia features (3)
-obligate anaerobic bacteria
C. tetani produces...
tetanospasmin, an exotoxin causing tetanus.
tetanic paralysis (blocks glycine and GABA release from Renshaw cells in the spinal cord). Causes spastic paralysis, trismus (lockjaw) and risus sardonicus.
C. botulinism causes disease in adults by...
ingestion of a preformed toxin. In babies, ingestion of spores in honey causes the disease.
C. difficile produces...
1. Toxin A (enterotoxin) binds to the brush border of the gut.
2. Toxin B (cytotoxin) causes cytoskeletal disruption via actin depolymerization leading to pseudomembranous colitis and diarrhea.
C. diff often occurs secondary to...
antibiotic use (esp. clindamycin and ampicillin).
C. diff is diagnosed by...
detection of one or both of the toxins in the stool.
Tretment for C. diff
Metronidazole or Oral Vancomycin
(fecal transplant may prevent relapse in recurring infxns)
Bacillus anthracis features (4):
1. gram positive
2. spore-forming rod
3. produces anthrax toxin (causing anthrax)
4. only bacterium with a polypeptide capsule (contains D-glutamate)
A boil like lesion leads to an ulcer with black eschar (painless, necrotic). This can but rarely leads to bacteremia and death.
Inhalation of spores leads to flu-like symptoms that rapidly progress to fever, pulmonary hemorrhage, mediastinitis and shock.
inhalation of anthrax spores from contaminated wool
Bacillus cereus causes...
food poisoning. Spores survive cooking in rice (and pasta). Keeping rice warm results in germination of spores and enterotoxin formation.
2 Types of B. cereus food poisoning
1. Emetic type (nausea/vomiting within 1-5 hrs, caused by cereulide (a preformed toxin))
2. Diarrheal type (watery, nonbloody diarrhea and GI pain w/i 8-18 hrs)
Listeria monocytogenes is a...
facultative intracellular microbe. It is the only gram-positive bacteria to produce LPS.
Listeria monocytogenes forms...
"rocket tails" via actin polymerization that allow them to move through the cytoplasm and into the cell membrane, thereby avoiding abtibody. Characteristic tumbling motility.
Listeria monocytogenes is acquired by...
ingestion of unpasteurized dairy products an deli meats, via transplacental transmission or vaginal transmission during birth.
Listeria monocytogenes causes:
3. spontaneous abortion
4. granulomatosis infantiseptica
5. neonatal meningitis
6. meningitis in immunocompromised pts
7. mild gastroenteritis
Treatment for Listeria
Ampicillin in infants, immunocompromised pts and the elderly in empiric tx of meningitis.
Both Actinomyces and Nocardia form...
long, branching filaments resembling fungi.
1. gram positive anaerobe
2. normal oral flora
3. causes oral/facial abcesses that drain through sinus tracts and form yellow "sulfur granules"
4. treat with penicillin
1. gram positive aerobe
2. acid fast (weak)
3. found in soil
4. causes pulmonary infxns in immunocompromised and cutaneous infections after trauma in immunocompetent
5. treat with sulfonamides
Pts will be PPD+ for TB if...
they have a current infxn, past exposure or BCG vaccinated.
Pts will be PPD- for TB if...
they have no infxn or are anergic (steroids, malnutrition, immunocompromised) and in sarcoidosis.
A more specific test for TB is...
an interferon gamma release assay (IGRA) which has fewer false positives from the BCG vaccine.
Mycobacterium kansasii causes...
pulmonary TB-like symptoms.
Mycobacterium avium-intracellulare causes...
disseminated, non-TB disease in AIDS pts; give prophylactic treatment with Azithromycin.
TB symptoms include...
fever, night sweats, weight loss and hemoptysis.
Virulent strains of mycobacterium have...
cord factor which inhibits macrophage maturation and induces release of TNF-alpha.
Sulfatides (surface glycolipids) inhibit phagolysosomal fusion.
Leprosy (Hansen Disease) is caused by...
Mycobacterium leprae, an acid-fast bacillus that likes cool temperatures (infects skin and superficial nerves).
Lepromatous form of Hansen Disease
presents diffusely over the skin with leonine facies and is communicable; characterized by low cell-mediated immunity with a humoral Th2 response.
Tuberculoid form of Hansen Disease
limited to a few hypoesthetic, hairless skin plaques; characterized by high cell-mediated immunity w/ a largely Th1 immune response
Treatment for Leprosy
Tuberculoid form: Dapsone and Rifampin for 6 months
Lepromatous form: Dapsone, Rifampin, Clofazimine for 2-5 yrs
Examples of Lactose-fermenting enteric bacteria (5)
3. E. coli
5. Serratia (weak fermenter)
Beta-galactosidase, which breaks down lactose into glucose and galactose.
On EMB agar, lactose fermenters grow as...
purple/black colonies. E.coli also has a green sheen.
Gram-negative bacilli are resistant to...
penicillin G but may be susceptible to penicillin derivatives such as ampicillin and amoxicillin.
Gram-negative bacilli are resistant to penicllin G and vancomycin because...
the outer membrane layer inhibits entry of the drugs.
-gram negative diplococci
-produce IgA protease
-N. gonorrhea is often intracellular (w/i neutrophils)
Neisseria gonococci features
-causes gonorrhea, septic arthritis, neonatal conjuctivitis, PID and Fitz-Hugh-Curtis syndrome
Neonatal transmission of N. gonorrhae can be prevented with...
Treatment for N. gonorrhae
Ceftriaxone + (azithromycin or doxycycline) for possible chlamydia coinfection
Neisseria menigococci features
-respiratory and oral secretions
-causes meningococcemia and meningitis and waterhouse-friderichsen syndrome
N. meningitidis can be prevented in close contacts with...
rifampin, ciprofloxacin or ceftriaxone prophylaxis.
Treatment for N. meningitidis
Ceftriaxone or Penicillin G
Haemophilus influenzae features
-small, gram negative rod
-produces IgA protease A
Haemophilus influenzae causes...
Epiglottitis (cherry red/thumbprint sign)
H. influenzae mucosal infections can be treated with...
Amoxicillin +/- Clavulanate.
Hib meningitis can be treated with...
ceftriaxone. And Rifampin can be given to close contacts for prophylaxis.
The H. influenzae vaccine contains...
type B capsular polysaccharide (polyribosylribitol phosphate) conjugated to diphtheria toxoid. Given between 2 and 18 months of age.
H. influenzae does not cause...
the flu. The influenza virus does.
Legionella pneumophila features
-use silver stain
-grow on charcoal yeast extract culture with iron and cysteine
Transmission of Legionella pneumophila
Aerosol transmission from environmental water source habitat (air conditioning, hot water tanks). No person-to-person transmission.
Legionella pneumophila is detected clinically by...
presence of antigen in the urine.
Treatment for Legionella
Macrolide or Quinolone
Labs for Legionella show...
Legionnaires' disease and Pontiac fever.
Pontiac Fever is...
a mild flu-like syndrome.
Legionnaire's disease is...
severe pneumonia, fever, GI and CNS symptoms
Pseudomonas aeruginosa features
-aerobic, gram-negative rod
-non lactose fermenting
-produces pyocyanin (blue-green pigment)
-produces endotoxin and exotoxin A
Pseudomonas is associated with:
wound and burn infections
pneumonia (esp. CF)
external otitis (swimmer's ear)
hot tub folliculitis
Ecthyma gangrenosum is...
a rapidly progressive, necrotic cutaneous lesion caused by Pseudomonas bacteremia. Typically in immunocompromised pts.
Treatment for pseudomonas aeruginosa
aminoglycoside plus extended spectrum penicillin
Chronic pneumonia in CF pts is associated with...
biofilm from pseudomonas.
E. coli virulence factors (and what they cause)
1. fimbrae - cystitis and pyelonephritis
2. K capsule - pneumonia and neonatal meningitis
3. LPS endotoxin - septic shock
microbe invades intestinal mucosa and causes necrosis and inflammation (similar manifestations to Shigella)
produces heat-labile and heat-stable enterotoxins. no inflammation or invasion
travelere's diarrhea (watery)
no toxin produced; adheres to apical surface, flattens villi, prevents absorption
diarrhea (usually in children)
O157:H7 is the most common serotype. produces shiga-like toxin that causes HUS (triad of anemia, thrombocytopenia and acute renal failure). Microthrombi form on the endothelium damaged by the toxin leading to mechanical hemolysis (schistocytes) and decreased renal blood flow.; microthrombi consume platelets leading to thrombocytopenia.
EHEC is distinguished from other forms of E. coli because...
it does not ferment sorbitol.
-mucoid colonies caused by abundant polysaccharide capsules
-red "currant jelly" sputum
lobar pneumonia in alcoholics and diabetics when aspirated. (abscesses in lungs and liver)
Can also cause nosocomial UTIs.
-many animal reservoirs
-produces hydrogen sulfide
-does not ferment lactose
Antibiotics for salmonella may...
prolong fecal excretion of the organism.
Salmonella acts by...
invading intestinal mucosa and causing a monocytic response sometimes leading to bloody diarrhea.
-cell to cell transmission
-human and primate reservoirs
-does not ferment lactose
Abitibotics for shigella may...
shorten the duration of fecal excretion of the organism.
Shigella acts by...
invading intestinal mucosa and causing PMN infiltration often leading to bloody diarrhea.
Salmonella typhi causes...
typhoid fever characterized by red spots on the abdomen, fever, HA and diarrhea.
Salmonella typhi can remain in the...
gallbladder and cause a carrier state.
Campylobacter jejuni is a major cause...
of bloody diarrhea.
Campylobacter is transmitted...
fecal-orally through foods such as poultry, meat and unpasteurized milk.
Features of Campylobacter jejuni
-comma or S-shaped
-grows at 42 C
Campylobacter is a common antecedant to...
Guillain-Barre Syndrome and reactive arthritis.
Vibrio cholerae produces...
rice-water diarrhea via enterotoxin that permanently activates Gs (increasing cAMP). Prompt oral rehydration is necessary.
Vibrio cholerae features
-grows in alkaline media
-endemic to developing countries
Yersinia enterocolitica is usually transmitted from...
pet feces, contaminated milk or pork.
Yersinia enterocolitica causes...
mesenteric adenitis that can mimic Chron's or appendicitis.
Helicobacter pylori causes...
gastritis and peptic ulcer (esp. duodenal).
H. pylori is a risk factor for...
peptic ulcer, gastric adenocarcinoma and lymphoma.
H. pylori features
-curved, gram negative rod
-creates an alkaline environment
Most common initial treatment for H. pylori is...
proton pump inhibitor + Clarithromycin + either amoxicillin or metronidazole
spiral-sharped bacteria with axial filaments and include Borrelia, Leptospira and Treponema.
Of the spirochetes, only Borrelia can be visualized using...
aniline dyes (Wright or Giemsa stain) in light microscopy.
Treponema is visualized by...
Leptospira interrogans is found in...
water contaminated with animal urine and causes leptospirosis: flu-like symptoms, jaundice, photophobia with conjunctival suffusion (erythema without exudate).
Leptospira interrogans is prevalent among...
surfers and in the tropics (Hawaii).
severe form of leptospirosis with jaundice and azotemia from liver and kidney dysfunction; fever, hemorrhage and anemia
Lyme disease is caused by..
Borrelia burgdorferi which is transmitted by the tick Ixodes. Natural reservoir is the mouse.
Initial symptoms of lyme disease
-erythema chronicum migrans
-flu like symptoms
+/- facial nerve palsy
Later symptoms of lyme disease
-AV nodal block
-facial nerve palsy
Treatment for Lyme Disease
Syphlis is caused by...
the spirochete Treponema pallidum.
a localized diseae presenting with painless chancre
Serologic testing for primary and secondary syphilis
Confirm w/ specific test (FTA-ABS).
disseminated disease with constitutional symptoms, maculopapular rash (palms and soles), condylomata lata
Gummas (chronic granulmoas), aortitis (vasa vasorum destruction), neurosyphilis (tabes dorsalis "general paresis"), Argyll Robertson pupil
Signs of Tertiary syphilis
-stroke w/o HTN
To diagnose tertiary syphilis, test...
spinal fluid with VDRL or RPR.
Congenital syphilis signs
-CN VIII deafness
To prevent congenital syphilis:
treat mother early in pregnancy bc transmission usually occurs after the 1st trimester
Argyll Robertson pupil
constricts with accommodation but is not reactive to light
(associated with tertiary syphilis)
nonspecific antibody that reacts with beef cardiolipin; it is sensitive for syphilis but not specific.
VDRL has many false positives due to...
viral infection (mono, hepatitis)
flu-like syndrome after antibiotics are started - due to killed bacteria releasing pyrogens
Anaplasma is a zoonotic bacteria that causes...
anaplasmosis from ixodes ticks.
Bartonella is a zoonotic bacteria that causes...
cat scratch disease, bacillary angiomatosis from cat scratches.
Borrelia recurrentis is a zoonotic bacteria that casues...
relapsing fever from louse.
Brucella is a zoonotic bacteria that causes...
Brucellosis/undulant fever from unpasteruized dairy.
Chlamydophila psittaci is a zoonotic bacteria that causes...
Psittacosis from parrots and other birds.
Coxiella burnetii is a zoonotic bacteria that causes...
Q fever from aerosols of cattle/sheep amniotic fluid.
Ehrlichia chaffeensis is a zoonotic bacteria that causes..
Ehrlichiosis from Lone Star ticks.
Francisella tularensis is a zoonotic bacteria that causes...
Tularemia from ticks, rabbits and deer fly.
Pasteurella multocida is a zoonotic bacteria that causes...
cellulitis and osteomyelitis from animal bites, cats and dogs.
Rickettsia prowazekii is a zoonotic bacteria that causes...
epidemic typhus from louse.
Rickettsia rickettsii is a zoonotic bacteria that causes...
Rocky Mountain spotted fever from dermacentor ticks.
Rickettsia typhi is a zoonotic bacteria that causes...
endemic typhus from fleas.
Yersinia pestis is a zoonotic bacteria that causes....
plague from fleas.
Gardnerella vaginalis is a...
pleomorphic rod that presents with vaginosis as a gray vaginal discharge with a fishy smell; nonpainful.
Gardnerella is associated with...
sexual activity but is not sexually transmitted.
Bacterial vaginosis is also characterized by....
overgrowth of certain anaerobic bacteria in the vagina.
In bacterial vaginosis, under the microscope....
clue cells, or vaginal epithelial cells covered with the Gardnerella bacteria are visible.
Treatment for Gardnerella vaginalis
Metronidazole (or Clindamycin to treat anaerobic bacteria).
Treatment for all Rickettsial disease and vector-borne illnesses is...
Rocky Mountain Spotted Fever occurs primarily in...
the South Atlantic States (esp. North Carolina). Rash starts at wrists and ankles and spreads to trunk, palms, soles.
(caused by Rickettsia rickettsii)
-need CoA and NAD+ because they cannot synthesize ATP
Classic Triad of Rocky Mountain Spotted Fever
Typhus rash starts...
centrally and then spreads out, sparing the palms and soles.
-monocytes with moulae (berry-like inclusions) in cytoplasm
-rash is rare
-granulocytes with morulae in cytoplasm
-rash is rare
-presents as pneumonia
-rash is rare
-no arthropod vector
-cannot make their own ATP
-cause mucosal infections
2 forms of Chlamydiae:
1. Elementary body (small, dense): infectious, enters cell via endoctyosis and transforms into reticulate body
2. Reticulate body: replicates in cell by fission; reorganizes into elementary body
Chlaymdia trachomatis causes...
reactive arthritis (Reiter syndrome), follicular conjunctivitis, urethritis and PID.
C. pneumoniae and C. psittaci cause...
atypical pneumonia; transmitted by aerosol.
Treatment for Chlamydiae
Aziththromycin or Doxycycline
The chlamydial cell wall is unusal in that it...
lack muramic acid.
Chlamydia trachomatis types A, B and C
chronic infection, cause blindness due to follicular conjunctivitis in Africa
Chlamydia trachomatis types D-K
urethritis/PID, ectopic pregnancy, neonatal pneumonia (staccato cough), neonatal conjunctivitis
Chlamydia trachomatis typse L1, L2 and L3
Lymphogranuloma venereum - small, painless ulcers on genitals; swollen, painful inguinal LNs that ulcerate
Mycoplasma pneumoniae is the classic cause of...
atypical "walking" pneumonia (insidious onset, HA, nonproductive cough, patchy or diffuse interstital infiltrate).
Atypical pneumonia findings
-X-ray looks worse than pt
-high titer of cold agglutinins (IgM)
-grown on Eaton agar
-more common in pts less than 30
-frequent outbreaks in miliatry recruits and prisons
Treatment for Mycoplasma pneumoniae