Microbiology Flashcards
Gram positive bacteria appear…
Blue from crystal violet stain
Gram negative bacteria appear…
red by absorbing safranin stain
7 classic disease-causing GP bugs
3 are cocci: streptococcus + enterococcus form strips of cocci. Staphylococcus forms clusters of cocci.
2 of 4 GP rods produce spores: bacillus and clostridium
Corynebacterium and listeria do not form spores
Which gram negative bacteria is a cocci?
Neisseria is a diplococci (kissing coffee beans)
What is the GN group of spiral shaped rods called? Example?
Spirochetes, treponema pallidum
What classification do most GN fall under?
rods or pleomorphic
Is mycobacteria GP or GN?
Weakly GP but stained much better with acid-fast stain
How are spirochetes visualized?
darkfield microscopy. They are too small to be seen with the light microscope
Are mycoplasma GN or GP?
Neither. They do not have a cell wall. They only have a simple cell membrane.
Please name the GP cocci.
Streptococcus, enterococcus and staphylococcus
Please name the GN cocci.
Neisseria
Please name the GP rods (bacilli)
Corynebacterium, listeria, bacillus, clostridium
Please name the GN rods (bacilli)
Enterics:
- Escherichia coli
- Shigella
- Salmonella
- Yersinia
- Klebsiella
- Proteus
- Enterobacter
- Serratia
- Vibrio
- Campylobacter
- Helicobacter
- Pseudomonas
- Bacteroides (anaerobic)
Others: Haemophylus, bordetella, legionella, Yersinia, Francisella, Brucella, Pasteurella, Gardnerella.
Please name the GN spirochetes.
Treponema, Borrelia, Leptospira
Please name the gram positives with branching filamentous growth.
Actinomyces (anaerobic)
Nocardia (partially acid-fast)
Which bacteria is neither GP or GN and has no cell wall?
Mycoplasma
Name two GN diplococci
N. meningitidis
N. gonorrhoeae
Name the GN “coccoid” rods
Haemophilus influenzae
Pasteurella (animal bites)
Brucella (brucellosis)
Bordetella pertussis
Name the GN rods that are lactose fermenters
Fast
- Klebsiella
- E. coli
- Enterobacter
Slow
- Citrobacter
- Serrate
- Others
Name the GN rods that are lactose nonfermenters
Oxidase +
- Pseudomonas
Oxidase - Shigella Salmonella Proteus Yersinia
Name the gram positive cocci and their common sites of invasion.
Staphylococcus and streptococcus.
Staph inhabits skin and is likely to infect wounds, surgical sites, and indwelling catheters (infective endocarditis).
Strep can cause CAP, adult bacterial meningitis, strep throat, rheumatic fever.
Name common anaerobes and their common sites of invasion.
Bactericides fragilis, Clostridium difficile, fusobacterium, C. botulinum and C tetani.
Anaerobes colonize the mouth, GI tract and skin. Infections develop when anaerobes penetrate poorly oxygenated tissues (diabetic foot) or tissues that are normally sterile (peritoneum)
Name common gram negative pathogens and their common sites of invasion.
Enterics: Escherichia, Shigella, Salmonella, Klebsiella, Enterobacter, Serratia, Proteus.
Others: Haemophilus influenza, Neisseria, pseudomonas
Enterics are responsible for many UTIs and aspiration pneumonia. Neisseria = gonorrhea. N. meningitides + H. influenza = meningitis. H. influenzae can cause pneumonia. Pseudomonas can occur at any site, particularly in immunocompromised. Its sticky.
What does vancomycin cover?
PCN-resistant/MRSA. Bacteriostatic against enterococcus. Oral: C. difficile
What does bacitracin cover?
GPs infecting skin. Eye infections.
What do the carbapenems cover?
Acinetobacter. Excellent coverage of most GPs and GNs and pseudomonas.
What does aztreonam cover?
Excellent GN, including pseudomonas. No GP coverage.
What does daptomycin cover?
Skin infections caused by S. aureus, MRSA, strep species, Vanco-sensitive enterococcus
What does penicillin cover?
Narrow spectrum. Covers GP cocci, Neisseria, most mouth anaerobes. NOT effective against GN aerobes or B-lactamase-producing organisms.
What does nafcillin, oxacillin and dicloxacillin cover?
Narrow spectrum. GP cocci (including B-lactamase producers), some streptococci. NOT effective against GN aerobes.
What does ampicillin and amoxicillin cover?
Broad spectrum. Some GN and GP. DOC for listeria and enterococcus. NOT effective against B-lactamases.
What does Augmentin (amox/clav) cover?
GN and GP and B-lactamases. DOC for moraxella and H influenzae.
What does Ticaracillin cover?
Extended spectrum. GN infections (especially pseudomonas) and amino penicillin-resistant proteus infections. Less effective against GP penicillinases.
What does piperacillin cover?
Extended spectrum. Good for Enterobacteria and GP cocci.
What does piperacillin/tazobactam cover?
Extended spectrum. GN infections (especially pseudomonas) and amino penicillin-resistant proteus infections. Less effective against GP penicillinases. Similar to ticaracillin but covers piperacillin-resistant GNs and GP penicillinase-producers.
Name the first generation cephalosporins and their activity.
Cephalexin, cefadroxil, cefazolin. GP cocci except enterococci and MRSA. Some GN enteric. Not effective against anaerobes.
Name the second generation cephalosporins and their activity.
Cofactor, cefprozil, cefuroxime, cefoxitin, cefotetan.
GP cocci. Extended GN activity (H. flu, Enterobacter, Proteus, Neisseria sp.) NONE are effective against pseudomonas.
Name the third generation cephalosporins and their activity.
Ceftriaxone, cefotaxime, deftazidime, ceftizoxime, cefepime, ceftibuten, cefpodoxime, cefdinir, cefditorin. GN bacilli. Pseudomonas best covered by ceftazidime, cefepime). GP cocci.
