Staphylococci Lecture 11 Flashcards
Enterococcus
Normal flora of the large bowel and feces;
antibiotic resistance is common;
fourth leading cause of nosocomial infections
E. Faecium, and E faecalis
Physiology and structure of Enterococcus
Gram positive cocci in pairs or short chain
grow both aerobic and anerobic in a broad in a broad range of temps (10-45 C)
catalase negative
bacitricin resistant
variable hemolysis
can grow in presence of 6.5 NaCl
can tolerate 40% bile salt
can hydrolyze esculin
source and transmission of enterococcus
enteric bacteria
found in large intestine and genitourinary tract
human infection orginate from patients bowel flora
virulence factors: entercoccus
aggregation substance
carbohydrate adhesins
cytolysin: inhibits gram positive bacter and induce local tissue damage
gelatinase
antibiotic resistant: resistant to aminoglycoside, beta lactams, and vancomycin
lab diagnosis of entercocus
biochemical test: resistant to optochin
do not dissolve when exposed to bile
TX of entercoccus
ampicillin can be used for senstive strains
combination of an aminoglycoside and vancomycin for resistant strains: Vanc resistant enterococci (VRE) have a substititue for the D ala D ala in peptidoglycan that is the target for vancomycin
Viridans streptococci
a major part of tnormal flora of the mouth and teeth
identification: Alpha hemolytic, resistance to optochin and no lancefield antigens
Groups C and G streptococci: non rheumatogenic but otherwise specture of infections like group A
viridans streptococci: sub actue endocarditis (#1 causative agents), central role in dental carries
TX of streptococcal endocarditis: penicillin and antibiotic prophylaxis
Summary of strep infections
GAS: Gram +, catalase -, doesn’t like oxygen, capsule, M proteins, C5a peptidase; GBS: capsule
suppartive: pharyngitis, scarlet fever, impetigo, cellulitis, erysipelas
non supparative: PSGN, acute rheumatic fever
GBS: neonatal meningitis and sepsis, CAMP testing
strep pneumo: polysaccharide, bile, IgA protease, vaccine, pneumonia, meningitis, sinusitis, otitis media
entercoccous, resistance to antibiotics, normal flora, VRA, hospital acquired UTI
Staphylcocci
gram positive cocci in bunches
Abscesses, systemic diseases, food poisoning, and toxic shock syndrome
General characteristics of Staphylcocci
gram +: most resistant of the non spore formers to adverse conditions
non motile
facultatively anaerobic
catalase +; coagulase +/-
can grow: medium containing 10% NaCl
genus: 40 species; 16 are found on humans
S. aureus (coagulase +)
CNS: S. Epidermidis, and S. Saprophyticus
Properties of S. Aureus
frequency of disease: common
Coagulase +
color of colonies: Bronze
Mannitol fermentation: +
Novobiocin resistance: -
Properties of S. Epidermidis
frequency of disease: common
Coagulase -
Color of colony: White
Mannitol fermentation: -
Novobiocin resistance -
Properties of S Saprophyticus
Frequency: Occasional
Coagulase -
color of colonies: White
Mannitol fermentation -
novobiocin resistance +
Physiology and structure of Staphylococci
capsule: more common in vivo. Helps in adherence, inhibiting chemotaxis, phagocytosis. More important in coagulase negative strains
protein A: S aureus only
Techoic acid: glycerol TA (SE), Ribitol TA (SA)
Coagulase (clumping factor): S. Aureus
Enzyme: lipase, hyaluronidase
staphylococcus aureus
gram positive cluster forming coccus
non motile, non spore forming facultative anaerobe
fermentation of glucose produces mainly lactic acid
ferments mannitol (distinguishes from S. Epidermidis)
catalse positive; coagulase positive
golden yellow colny on agar
normal flora of humans found on nasal passages, skin and mucous membranes
pathogen of humans, causes a wide range of suppurative infection as well as food poisoning and toxic shock syndrome