USMLE Microbiology Bacteria 1
Terms
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- What is Ritter's Syndrome?
- When S. aureus colonizes the Umbilicus of neonate and releases EXFOLIATIVE TOXIN = Scalded Skin Syndrome
- Novobiocin sensitive
- S. epidermidis
- Treatment for S. epidermidis
-
Vancomycin
*most strains are resistant to penicillins and cephalosporins - Novobiocin resistant
- S. saprophyticus
-
-"Sandpaper" rash that begins on the trunk and spreads outward
-"Strawberry" tongue within first 2 days
-Desquamation of palms and soles after rash subsides - S. pyogenes Scarlet Fever
- Explain Toxic Strep
-
-Cellulitis infection
-systemic release of Exotoxin A = Superantigen
-Polyclonal activation of T cells -
Cause of Necrotizing Fasciitis due to Exotoxin B (a protease)
-rapid necrosis along fascial planes, sparing muscles - S. pyogenes
- Gram + cocci, Catalase - that grows in 40% bile and 6.5% NaCl
- Enterococcus faecalis = highly drug resistant
- All Enterococci strain are resistant to what drug?
- Cephalosporins
-
Gram + coccus which grows in bile but is susceptible to salt
-causes Subacute Bacterial Endocarditis
-associated with Colon Cancer - Strep BOVIS
- Optochin sensitive
- S. pneumo
- Rusty-colored sputum with right lower lob consolidation
- S. pneumo
- 2 deficiencies that would make one susceptible to S. pneumo infections
-
Asplenic
IgG2 - Age group in which S. pneumo is the most common cause of Meningitis
- > 60 years
- Optochin resistant microbe that causes dental caries and Subacute Bacterial Endocarditis
- Strep mutans (Viridians)
- Optochin resistant microbe that causes brain/liver abscesses and Subacute Bacterial Endocarditis
- Strep. Intermedius
- Food poisoning after eating reheated rice
- BAcillus cereus
- What are you ingesting after eating Bacillus Cereus reheated rice?
- Spores = bacteria form protective spores during high temperature cooking
- Has a Poly-D glutamic acid capsule
- B. anthracis
- 3 toxins produced in B. anthracis
-
1. Protective antigen (PA): binds cell membrane and mediates endocytic entry of EF or LF
2. Edema Factor (EF): activates Adenylate Cyclase
3. Lethal Factor (LF): cell death - Non-motile Clostridium species
- Perfringens
- Bacteria with Terminal Spores
- Clostridia
- Clostridia toxin that travels retrogradely on axons of peripheral motor neurons
- Tetanus
- Spastic paralysis
- Tetanus
- Double vision + Ptosis
- C. botulinum
- Toxins present in Canned foods
- C. botulinum
- What does infant ingest in Floppy baby syndrome?
- SPORES of C. botulinum
- What does an adult ingest in Adult Botulism?
- Heat-labile TOXINS
- Inhibits GABA release
- C. tetanus
- Inhibits Acetycholine release
- C. botulinum
- How does C. difficile survive antibiotic treatment?
- forms spores which germinate after antibiotic treatment is over
- How does C. difficile cause Watery diarrhea and Pseudomembranous Colitis?
-
Diarrhea = toxin A alter fluid secretion
PMC = Toxin B is cytotoxic to epithelial cells
*only release toxins in LOG phase - Air bubbles below the skin that generate a crackling sound when touched (crepitus)
- C. perfringens
- Lecithinase (alpha toxin) that causes muscle cell necrosis
- C. perfringens
- Gas gangrene
- C. perfringens
- Gram + rod with tumbling motility
- Listeria
- Only Gram + with endotoxin
- Listeria
- Listeria and B-hemolytic Strep appear similar on blood agar...how do you differentiate?
- Listeria is Catalase +
- Tellurite agar
- C. diphtheria
- Gram + rod with "chinese letter" appearance
- C. diphtheria
- Where is Diphtheria toxin derived?
- Phage
-
Gram + filament
Obligate Anaerobe - Actinomyces israelii
- Yellow Sulfur granules
- Actinomyces
- Draining sinus tracts after dental work
- Actinomyces
- Gram + filament that forms abscesses in mouth, lungs, GI, GU
- Actinomyces
- Gram + filament that is weakly acid fast
- Nocardia
- Caseous granuloma in lung containing Gram + filaments
-
Nocardia
-Obligate Aerobe
**Nagging Pests Must Breathe - Kidney-bean shaped diplococci
- N. meningitidis
- Maltose and Glucose oxidizer
- N. meningitidis
- Most common cause of meningitis in 6-60 year olds
- N. meningitidis
- Thayer-Martin media
- Neisseria
- Meningococcemia with petechial rash
- N. menigitidis
- Site where B-lactamases reside
- periplasmic space
- Most common cause of septic arthritis in sexually active people
- N. gonorrhoeae
- Dysuria + yellow urethral discharge
- N. gonorrhoeae
- Glucose oxidizer only
- N. gonorrhoeae
- What does N. gonorrhoeae specialized Pili provide?
-
1. ANTIGENIC VARIATION
2. mucosal attachment
3. prevents phagocytosis -
Ophthalmia Neonatorum = risk for blindness
How to prevent?
Why is vaccine difficult? -
N. gonorrhoeae
prophylactic Erythromycin eye drops for neonates
pili antigen variation - What is Fitz-Hugh-Curtis Syndrome?
- when N. gonorrhoeae spill into the Peritoneal cavity from the fallopian tubes and infect the Liver Capsule
- Treatment for N. gonorrhoeae
- Ceftriaxone
- When is there a higher incidence of infection with N. gonorrhoeae?
- Menstruation
-
Alcoholic produces bloody "currant-jelly" sputum
CXR shows Right Upper Lobe inflammation with cavities
Rx? -
Klebsiella pneumonia
3rd generation Cephalosporin = Ceftriaxone, Cefotaxime, Ceftazadime -
Gram - rods
Lactose fermenter
large Capsule - Klebsiella
- E. coli LT toxin mode of action
- ADP ribosylates Gs = activates Adenylate Cyclase = high cAMP = watery diarrhea
- E. coli ST toxin mode of action
- activates Guanylate cyclase = high cGMP = low cotransport of NaCl into cells = water remains in lumen = watery diarrhea
- E. coli shiga-like toxin mode of action
- inactivates 60S ribosome = block protein synthesis = cell death
- 2 E.coli species that produce Shiga-like toxin
-
EHEC
EIEC - Gram - rod that is motile and produces H2S
- SalMonella = capital M = motile
- Gram - rod that causes Osteomyelitis in Sickle Cell patients
- Salmonella typhi
- Fever with enlarged spleen and generally tender abdomen with red macules
- Salmonella typhi = Typhoid Fever
- Stored in Gall bladder
- S. typhi
- Vi polysaccharide capsule
- Salmonella
- Diarrhea and vomiting after playing with a turtle
- Salmonella Enteritidis
-
Non-motile Gram - rod
Lactose -
Oxidase - - Shigella
- Microbe whose antigen is used to diagnose Rickettsia in the Weil-Felix reaction
- Proteus vulgaris O antigen
-
Urease +
Gram - rod
"swarming growth" - Proteus Mirabilis
- Most common cause of UTI in nursing home patients with indwelling catheters
- Providencia
-
Urease +
Gram - rod - Proteus Mirabilis
- Rice water diarrhea after eating raw seafood
- V. parahaemolyticus
-
Grows yellow on TCBS agar
Comma-shaped Gram - rod with single flagella - Vibrio cholera
- Cholera toxin mode of action
-
ADP ribosylates Gs = activates AC = high cAMP = cells secrete Cl- = fluid follows = watery diarrhea
**carried on a Bacteriophage
**BCDE
-Botulinum toxin
-Cholera toxin
-Diphtheria toxin
-Erythrogenic toxin of S. pyogenes -
Gram - bacillus
Lactose -
Oxidase +
Glucose + -
Vibrio cholera
*Pseudomonas is Glucose - - P. aeruginosa Exotoxin A MOA
- ADP ribosylates EF-2 = inhibits protein synthesis
-
Endemic in SE Asia and infected Vietnam veterans
-fever
-bloody sputum
-pneumonia - P. pseudomallei
- Osteomyelitis in Diabetic or IV drug user
- P. aeruginosa
- Malignant External Otitis
- P. aeruginosa
- Folliculitis after a night in the hot tub
- P. aeruginosa
- Blue/green colonies with fruity odor
- P. aeruginosa
-
Gram - bacilli
Lactose -
Motile at 25' C, not at 37' C
Blood diarrhea - Y. enterocolitica
- Mesenteric adenitis mimicing Apendicitis
- Yersinia enterocolitica
- Safety-pin bipolar staining appearance
- Y. pestis
-
transmitted to humans from rodents by fleas -> phagocytosed -> transported to regional lymph nodes -> multiplies & stimulates inflammation -> regional lymphadenitis often in groin
within macrophages capsular F1 antigen prevents - y. pestis
- What do vaccines for Y. pestis produce antibodies against?
- F1 capsular antigen