Cloned from: USMLE Microbiology



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-RNA viruses
Arenaviruses, bunyaviruses, paramyxoviruses, orthomyxoviruses, filoviruses, rhabdoviruses, and hepatitis delta virus (Always Bring a Polymerase or Fail Replication Horribly)
1st generation Cephalosporins- names (2) and use
Cefazolin, cephalexin, and any other with PH in its name. Good for gram-positive cocci (best for G+, except 4th gen) so use for staph and strep when penicillin cannot be tolerated; also for proteus mirabilis, E coli, Klebsielle, and surgery prophylaxis
2 forms of Chlamydia bacteria
Elementary Bodies- infectious, enter cell via endocytosis. Reticular bodies- replicate in endosome via fusion.
2 forms of leprosy
Lepromatous (Failed CMI, lethal), and tuberculoid (self-limited)
2 types of infections caused by C perfringens
1. Cellulitis/wound infection- palpitation reveals moist, spongy crackling consistency to the skin due to pockets of gas (crepitus). 2. Clostridial myonecrosis (inoculation with trauma into muscle- c perfringens secretes a toxin that destroys adjacent muscle; pockets of gas formation seen within muscle and a thin, blackish fluid exuding from the skin.
2nd generation Cephalosporins- names (3) and use
Cefoxitin, cefaclor, cefuroxime. Better G- coverage than 1st generation: Haemophilus, Enterobacter aerogenes, Neisseria spp, Proteus mirabilis, E coli, Klebsiella pneumoniae, Serratia marcescens (HEN PEcKS). Good for empiric coverage of CAPs bc of action against both strep and haemophilus
3 most comon causes of diarrhea in the world
Campylobacter jejuni, ETEC, and rotaviruses
3 Rickettsial diseases and etiologic agents
RMSF- Rickettsia ricketsi. Endemic typhus (fleas)- R typhi. Epidemic typhi (body louse)- R prowazekii
3 types of chlamydia and infections each causes
Chlamydia trachomatis (reactive arthritis, conjunctivitis, NGU, PID). C pneumoniae and C psittaci cause atypical pneumonias
3 types of infections caused by strep pyogenes
Pyrogenic (pharyngitis, cellulitis, impetigo), Toxogenic (scarlet fever, TSS), Immunologic (Rhematic fever, glomerulonephritis)
3rd generation Cephalosporins- names (3) and use
Ceftriaxone, cefotaxime, ceftazidime, most have T in their names though cefotetan is 2nd gen. Serious G- infections resistant to other beta-lactams: meningitis (most penetrate BBB). Good for nosocomial pneumonias, meningitis, sepsis, and UTIs
4 bacteria/toxins that induce cAMP
Cholera toxin, pertussis toxin, E. coli LT, anthracis toxin (first 3 act via ADP ribasylation to permanently activate AC, while anthrax EF is an AC itself)
4th generation Cephalosporins- name (1) and use
Cefepime. Increased activity against Pseudomonas and G+ organisms
5 classes of penicillins
Penicillins, aminopenicillins (better G- coverage), penicillinase-resistant pens (good for Staph aureus), anti-pseudomonal pens, and cephalosporins
99% of intestinal flora
Family bacteroidaceae, esp B fragilis (G- obligate anaerobes)
Acid-fast staining organisms
Mycobacteria and Nocardia
Actinomyces israelli- infections and treatment
Gram-positive filamentous anaerobe, causes oral/facial abscesses that may drain through sinus tracts in skin (yellow sulfur granules in sinus tracts). Treat with penicillin
Agar for Neisseria
Thayer-Martin VCN or chocolate agar
Aminoglycosides- kinetics
Concentration-dependent killing action; also exert a postantibiotic effect (killing action continues when plasma levels have declined below measurable levels). Thus have a greater efficacy when administered as a single large dose. Toxicity depends on a critical plasma concentration and on the time that such a level is exceeded (time above that concentration will be shorter with a single large dose than multiple small doses).
Aminoglycosides- mechanism, use, toxicity
Inhibit formation of initiation complex (by binding to 30S) and cause misreading of mRNA. Require O2 for uptake so ineffective against anaerobes. Used for severe gram-negative rod infections; synergistic with beta-lactams. Streptococci and enterococci are relatively resistant owing to failure of the drug to penetrate the cell. Toxicity: nephrotoxicity (esp in combo with cephalosporins), ototoxicity (esp with loop diuretics), and teratogenic
Aminoglycosides- names (5)
Gentamicin, Neomycin, Amikacin, Tobramycin, Streptomycin
Aminopenicillins- names (2), uses, and toxicity
Ampicillin (IV) and amoxicillin (oral). Use for Haemophilus influenzae, E coli, Listeria, P mirabilis, Salmonella, (HELPS) and enterococci (one of few drugs effective against enterococcus). Toxicity is hypersensitivity reactions, ampicillin rash, and pseudomembranous colitis
Antibiotics prone to causing pseudomembranous colitis
Clindamycin and ampicillin
Antibiotics that block protein synthesis at the 30S subunit (and static vs cidal)
Aminoglycosides (cidal), tetracyclines (static)
Antibiotics that Gram negatives are resistant to
Penicillin G and vancomycin (G- outer membrane inhibits entry)
Antipseudomonals- names (3), use, and toxicity
Piperacillin, ticarcillin, and carbenicillin. Still sensitive to penicillinase so use with clauvulanic acid. Use for pseudomonas; also active against anaerobes (B fragilis), enterobacter, and some Klebsiella. Causes hypersensitivity reactions.
Appearance of coccidioides immitis on microscope
Spherules packed with endospores
Appearance of histoplasma in lung specimens
Ovoid cells within macrophages
B cereus features that distinguish it from B anthracis
Motile, non-encapsulated, and resistant to penicillin
B cereus toxins
Heat labile toxin (similar to cholera toxin and LT from E coli) causes nausea, ab pain, and diarrhea lasting 12-24 hours. Stable toxin (similar to staph auerus enterotoxin) has a short incubation followed by severe nausea and vomiting with limited diarrhea
B pertussis attachment
Attaches to ciliated epithelial cells of resp tract via filamentous hemagluttinin
Babesiosis
Intraerythrocytic protozoal disease due to Babesia microti, commonly a secondary infection with borrelia (also transmitted by Ixodes) and presents concurrently with Lyme disease. Fever, headache, hemolytic anemia.
Bacillary angiomatosis
Bartonella spp- causes vascular proliferative disease involving skin, bone, and subC tissue in immunocompromised patients
Bacteria associated with colon cancer
Strep bovis
Bacteria in unpasteurized milk and cheese
Listeria
Bacteria that asplenic pts are susceptible to
Mostly capsulated bacteria: strep pneumoniae (major one), H influenzae, Neisseria meningitidis, and Salmonella typhi
Bacterial types sensitive to Penicillin G
Gram+ cocci and G- rods and cocci. Mainly used for strep pneumoniae (though now there are many resistant strains bc of PBP alterations), GAS, meningococcus, and syphilis
Bacteriocidal Antibiotics (6)
Penicillin, Vancomycin, Metronidazole, Cephalosporins, Fluoroquinolones, aminoglycosides
Bacteriostatic Antibiotics (6)
Chloramphenicol, sulfamethoxazole, trimethoprim, erythromycin, clindamycin, tetracycline
Beta-hemolytic organisms other than GAS, GBS
Staph and Listeria
Botulism presentaiton (infants)
Constpiation for 2-3 days, followed by difficulty swallowing and mm weakness (floppy baby). Must be hospitalized and given supportive therapy; prognosis is good and antitoxin is not necessary
Botulism presentation (adults)
First develop bilateral CN palsies (diplopia and dysphagia). Followed by general muscle weakness and eventual sudden respiratory paralysis and death.
Branching, septate hyphae with arthrocondia
Dermatophytes
Brucellosis symptoms
Systemic sypmtoms after brucella penetrates, same as Yersinia or Francisella. However, the fever usually peaks in the evening and returns to normal by hte morning- undulant fever- can last from months to years but is rarely fatal
Bubonic plague- cause and syptoms
Yersinia pestis. During interepidemic times, bacteria invade the skin via the bite of an infected flea, and are eaten by macrophages. They reproduce intracellularly, then move to the nearest lymph nodes, which swell like eggs and become inflamed. Fever and headache set in. Bacteria then invade the bloodstream, liver, lungs, and other organs. Hemorrhages under the skin lead to blackish discoloration. Death w/out treatment can occur in a few days.
Budding yeasts
Sporotrichosis (cultured)
Bugs that cause bloody diarrhea (7)
Campylobacter, salmonella, shigella, EHEC, EIEC, yersinia enterocolitica, C difficile (can be watery or bloody), and entamoeba histolytica
Bugs that cause watery diarrhea (6)
ETEC, EPEC, vibrio cholerae, C perfringens, protozoa (giardia cryptosporidium), and viruses
Bugs that contaminate sea food
Vibrio parahaemolyticus and V. vulnificus
C. difficile toxins
Toxin A- diarrhea. Toxin B- cytotoxic to colonic cells
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