Flashcards
(63 cards)
Staphylococcus aureus
Gram (+) cocci (clusters & singly) yellowish, smooth, butyrous, beta hemolytic on BA & CNA Catalase (+) Coagulase (+) very common pyogenic pathogen found on 20-40% normal people virulence factors-enterotoxins, TSST-1, exfoliative toxin, cytolytic toxin, Protein A, Hyaluronidase, associated with: skin & wound infections, pneumonia, UTIs, osteomyelitis, & septic arthritis, food poisoning, & scalded skin syndrome
Methicillin-Resistant Staphylococcus aureus
Approx 50% of Staph aureus isolates are MRSA, has evolved an ability to survive treatment w/ beta-lactam antibiotics, resistance to beta-lactam antibiotics, resistance to beta lactams is provided by the mecA gene, which synthesizes penicillin binding protein (PBP), usually treated with vancomycin, BBL CHROMagar MRSA medium permits the direct detection & ID of MRSA & produces mauve colored colonies, non-MRSA will be white, color-less or blue-green
Staphylococcus epidermidis
Gram (+) cocci (clusters & singly) white, smooth, butyrous, non-hemolytic on BA & CNA, Catalase (+) Coagulase (-) Novobiocin Sensitive (S) CNS-Coagulase Negative Staphylococcus, Formerly always considered non-pathogenic but now its significance must be evaluated on a case by case basis, infectious conditions- normal flora, contaminant, opportunistic, nosocomial UTI, heart valve infections, catheters & shunts, Antibiotic susceptibility-variable
Staphylococcus saphrophyticus
Gram (+) cocci, white smooth non-hemolytic on BA & CNA Catalase (+) Coagulase (-) Novobiocin Resistant (R) common cause of UTI in young women, generally susceptible to antibiotics
Micrococci
Gram (+) cocci in tetrads (larger than Staph) often bright-orange yellow colored colonies, non hemolytic, Catalase (+) Coagulase (-) Bacitracin Sensitive (S) occasional pathogen, usually isolated as normal flora or contaminant
Streptococcus pneumoniae
“Lancet shaped” Gram (+) diplococcic, alpha hemolytic, oily-wet (capsulated) to dry (non-capsulated) colonies, auto-hemolysis causes “cratered” colony, lack Lancefield antigens, susceptible to Optochin (>14mm) Bile soluble (+) common disease conditions: pneumonia, otitis media, meningitis, normal flora Treated with: penicillin, erythromycin, chloramphenicol, antibiotic susceptibility testing required!
Streptococcus pyogenes
Group A, Gram(+) cocci (chains) small, beta hemolytic colonies, Bacitracin (S) SXT (R) PYR (+), direct antigen tests common, infectious conditions- “strep throat”, wounds, pneumonia, glomerular nephritis, scarlet fever, rheumatic fever, necrotizing fasciitis susceptible to penicillin & erythromycin
Streptococcus agalactiae
Group B, Gram(+) cocci (chains) beta/gamma hemolytic colonies, may require 48 hrs for beta hemolysis, Hippurate hydrolysis (+) CAMP(+) direct antigen tests from genital source (female) infectious conditions: neonatal meningitis & sepsis, puerperal fever (post partum infectious), pneumonia, susceptible to penicillin & aminoglycosides
Enterococcus
Group D Gram(+) cocci (pairs & chains) almost always gamma hemolytic Catalase- weakly(+) PYR(+) Bile esculin(+) 6.5% NaCl(+) normal flora in GI tract, infectious conditions, opportunistic UTI, resistant to many antibiotics, including penicillin & vancomycin, VRE- Vancomycin Resistant Enterococcus successful treatment often requires synergistic relationship between penicillin & vancomycin
Streptococcus bovis
Group D, Gram(+) cocci (pairs & chains) heterogenous group, Bile esculin (+) 6.5% NaCl (-) gamma/alpha hemolytic, newborn sepsis/endocarditis susceptible to penicillin
Virdans Streptococci
Oval, Gram(+) cocci (chains) alpha/gamma/beta hemolytic (usually alpha) optochin resistant, rarely pathogenic, lacks Lancefield antigens, normal flora in upper respiratory & GI tract, susceptible to penicillin
Nutritionally Variant Streptococci
Pleomorphic, Gram (+) cocci very small colonies, require Vitamin B6 or cysteine for growth, growth may only occur near Staph aureus (satellitism) PYR(+) normal flora in oral cavity, occasional pathogen (endocarditis/otitis media) susceptible to penicillin
Candida albicans
Normal flora in oral cavity, genitourinary & GI tracts, most common pathogenic yeast: UTI, vaginal infections, respiratory infections, systemic infections in immunocompromised, white, dry, star-shaped colonies, Gram stain-large, oval, budding shapes, wet prep- large oval budding shapes, Germ tube(+) carbohydrate assimilation panels, direct antigen & enzyme tests
Cryptococcus neoformans
Common opportunist in immunocompromised (HIV) & CSF, common in bird droppings, especially pigeons Gram stain: large, oval, budding structures (no branching) India ink test (+) direct antigen tests & carbohydrate assimilation tests
Corynebacterium diptheria
Short, pleomorphic, Gram(+) rods, small, non-hemolytic colonies on BA, Catalase(+) methylene blue stain shows metachromatic granules, diphtheria-oropharyngeal inflammation, toxin production w/damage to heart valves & CNS, diptheroids- non pathogenic susceptible to penicillin
Listeria monocytogenes
Short, Gram(+) rods, small beta hemolytic colonies, Catalase(+) non-spore forming facultative anaerobes “tumbling motility”, grows at low temps (cold enrichment) only pathogenic species pregnant women/fetuses/newborns are susceptible following consumption of contaminated meat products, ampicillin is primary antibiotic
Erysipelothrix rhusiopathiae
Slender, filamentous, Gram(+) rods, alpha hemolytic colonies, facultative anaerobe, non-motile, non-spore former, Catalase(-) H2S gas(+) common animal pathogen, human infectious associated with animal contact, cellulitis on hands/fingers, susceptible to penicillin
Garderella vaginalis
Gram variable coccobacilli, clear, non-hemolytic colonies on BA, beta-hemolytic on V agar & HBT agar, Catalase(-) Oxidase(-) Hippurate(+) normal flora in small amounts, vaginal discharge+clue cells+absence of normal flora whiff test: 10% KOH to vaginal discharage=fishy odor
Lactobacillus
Elongated, slender, Gram(+) rods, small, alpha hemolytic colonies, important component of female genital biota, Catalase(-) non-motile, non-spore forming, 80% facultative anaerobes, 20% obligative anaerobes, susceptible to penicillin (resistant to vancomycin)
Nocardia
Interwining, “string like” filamentous, Gram(+) rods, hard “chalky” colonies, slow growers require >48hrs for visibility, colonies smell like dirt, partially acid fast, associated with deep wound & pulmonary infections, susceptible to sulfonamides
Bacillus
Large heterogenous group of long “chunky” square-ended Gram(+) rods, large flat dry crusty colonies, Catalase(+) most species are non-pathogenic saprophytes usually seen as airborne contaminants, spore formers, resistant to environmental extremes “bamboo appearance”
Bacillus cereus
Large, Gram(+) rods, central spores, large beta-hemolytic “crusty colonies” Catalase(+), food poisoning following ingestion of spores, resistant to beta-lactams
Bacillus anthracis
Large, square-ended “bamboo” Gram(+) rods, central spores, large “crusty” non-hemolytic colonies, facultative anaerobe, causative agent of anthrax, forms of infection: cutaneous, pulmonary, & GI presumptive ID from “string of pearls” test, usually large animal disease, susceptible to penicillin
Neisseria gonorrhoeae
Gram(-) diplococcic, phagocytized by PMNs, major STD, grayish “pearly colored” colonies, fastidious-doesn’t grow on BA or MAC, only on CHOC or CHOC based, capnophilic, sensitive to extreme temp & drying, wooden applicators may be toxic, Oxidase(+) ferments only glucose
