Test 1: lecture 4 gram + Flashcards
what are the three main types of gram positive cocci
staphylococcus
streptococcus
enterococcus (formerly group D strep)
what does staphylococcus look like under the microscope
purple cocci in clusters
what does streptococcus look like under the microscope
purple cocci in chains
what does enterococcus look like under the microscope
oblong cocci to coccobacilli
often in pairs or chains
catalase test can be used the tell the difference between what gram + cocci?
staphylococcus → +
streptococcus → negative
enterococcus → negative/ pseudocatalase
which gram + cocci will sometimes have positive coagulase test
enterococcus
what kind of hemolysis will streptococcus have?
alpha, beta and gamma
what kind of hemolysis will enterococcus have?
gamma → not hemolytic
gram + cocci in cluster is
staphylococcus
Staphylococcus in clusters
gram +
Streptococcus in chains
gram +
Enterococcus → gram + cocci
cocci → coccobacilli
can form chains
How do bacteria use catalase to survive?
Catalase is an extracellular enzyme.
It functions to inactivate hydrogen peroxide (producing oxygen) and free radicals in macrophages leading to intracellular survival
allows staphylococcus to travel around inside macrophages without being eaten
how does catalase test work?
catalase produced by the bacteria will cause bubbles
staphylococcus is catalase + → catalase is also used to deactivate macrophages to allow staph to use them for movement
a positive catalase test for a gram + cocci means ___
staphylococcus bacteria
hydrogen peroxide will react with catalase and produce O2 (bubbles)
When you think skin infections… THINK ___
staphylococcus
___ causes opportunistic infections of almost all body system
staphylococcus
gram + cocci
___ causes canine pyoderma, greasy pig disease and bovine mastitis
staphylococcus
gram + cocci
coagulase test
a staphylococcus test only!
coagulase binds to prothrombin and causes conversion of fibrinogen to fibrin → creates a clot
staphylococci aureus cause what 3 diseases?
gram + cocci
equine SSTI, bovine contagious mastitis and avian bumblefoot
equine SSTI, bovine cont. mastitis and avian bumblefoot is caused by ___
staphylococcus aureus
Staphylococcus pseudintermedius (& S. schleiferi) cause what diseases ___
staph pseud
- pyoderma> otitis
- Canine & feline SSTI
- struvite urolithiasis (also proteus a gram -)
staph. schleiferi
- otitis> pyoderma
- Canine & feline SSTI
staphylococci hyicus cause what diseases?
Greasy pig disease
Greasy pig disease is causes by ___
staphylococcus hyicus
Canine & feline SSTI, pyoderma, struvite urolithiasis and otitis is caused by __
Staphylococci pseudintermedius → gram + cocci that is coagulase +
- pyoderma> otitis
- Canine & feline SSTI
- struvite urolithiasis (also proteus a gram -)
Staphylococci schleiferi → gram + cocci that is variable coagulase +
- otitis> pyoderma
- Canine & feline SSTI
transmission of staphylococcus aureus to cats and dogs is by ___
anthropozoonotic transmission → from person to animal
staphylococcus aureus is a pathogen of ___
people, rare to find on cats and dogs
very common in horses
staphylococcus aureus in horses
cause SSTI → mostly post op infections
septic arthritis and osteomyelitis
horses are common carriers of nasal ___
MRSA
Methicillin-resistant Staphylococcus aureus
(gram + cocci that is coagulase +)
___ is the bacteria usually found in post op infections in horses
staphylococcus aureus (gram +)
skin → think staph
Staphylococcus aureus will cause ____ in cattle
contagious mastitis
spread from cow to milking equipment to cow
___ causes contagious mastitis in cows
staphylococcus aureus (gram + cocci, coagulase +)
strep. agalactiae
strep. dysgalactiae
bumblefoot is caused by ___
staphylococcus aureus (gram + cocci, coagulase +)
___ is a chronic granulomatous process in the subcutaneous tissues of the foot caused by S. aureus
bumble foot
staphylococcus aureus (gram + cocci, coagulase +)
does S. pseudo or S. sch cause pyoderma
Staphylococcus pseudintermedius > S. schleiferi
does S. pseudo or S. sch cause otitis
S. schleiferi > S. pseudintermedius
gram + cocci, S. sch → variable coagulase, S. pseud → + coagulase
what causes struvite urolithiasis
Staphylococcus pseudintermedius
S. felis in cats
proteus (gram -)
___ produce urease
Staphylococcus pseudintermedius and Staphylococcus felis → (gram + cocci)
proteus (gram -)
cause struvite urolithiasis
explain how urease works
enzyme that changes ammonia into ammonium
→ cause a urine pH increase → leads to crystal formation → stone(urolith) formation → bacteria will form on stones and form biofilm which makes them very hard to kill and cause a persistent infection
(Staphylococcus pseudintermedius and S. felis and proteus → produce urease cause struvite urolithiasis)
how does struvite urolithiasis form
(Staphylococcus pseudintermedius and S. felis produce urease which is an enzyme that changes ammonia into ammonium → cause a urine pH increase → leads to crystal formation → stone(urolith) formation → bacteria will form on stones and form biofilm which makes them very hard to kill and cause a persistent infection
cause struvite urolithiasis
these are gram + cocci
another name for greasy pig disease
exudative epidermitis (caused by staphylococcus hyicus)
greasy pig disease is caused by ___
staphylococcus hyicus (gram + cocci)
young 7 week old pigs secondary to fighting/biting
Often systemic and rapidly fatal, affects lungs, lymph nodes,
kidneys and brain.
Skin lesions characterized by a thick grey-brown exudate around face and ears.
staphylococcus hyicus cause ___
exudative epidermitis (greasy pig disease)
how to test for methicillin resistance
broth micro dilution to find MIC (minimum inhibitory concentration) using Oxacillin
(beta lactam→ bactericidal and time dependent→ target cell wall synthesis by inhibiting PBP which cause NAG and NAM crosslinking in peptidoglycan)
what are the sensitivity ranges for MRSP
< 0.25 ng/ul = Sensitive
> 0.5 ng/ul = Resistant
use oxacillin (type of beta lactam)
methicillin resistance is cause by the bacterial production of ___ that causes ___
PBP2a
will allow cross linking of NAG and NAM to build peptidoglycan even in the presence of antibiotic
encoded by the mecA gene (SCC)
what gene produces the enzyme PBP2a
mecA gene (SCC)
resistant to beta lactams → cause methicillin resistance → allow for NAG and NAM cross linking to make peptidoglycan
MRSA vs MRSP
methicillin resistance staphylococcus aureus
methicillin resistance staphylococcus pseudintermedius