Gram Positive Cocci Flashcards
What is catalase?
Enzyme that breaks hydrogen peroxide into water and oxygen.
Gram + cocci in clusters contain catalase
Gram + cocci in chains don’t contain catalse
What common gram + cocci in clusters produces coagulase?
Staphylococcus aureus
Name a coagulase negative staphylococci
Staphylococcus epidermidis
Describe staphylococcus epidermidis
Gram-positive cocci in clusters (stains purple)
Coagulase negative
Catalase positive (contains catalase enzyme)
Facultative Anaerobe (can live with or w/o O2)
Part of the normal skin flora & mucosal flora
Describe Staphylococcus aureus
Gram-positive cocci in clusters (stains purple)
Catalase & coagulase positive
Most common and serious pathogen
Facultative Anaerobe (can live with or w/o O2)
Typically lives in nose
Illnesses caused by staphylococcus epidermidis infection & common treatments
Cellulitis
Bacteremia (e.g. IV insertion)
Name the 4 most common infections caused by Staphylococcus aureus
Wounds
Skin (cellulitis)
Heart valves (endocarditis)
Bone (osteomyelitis)
BoWSH
Which class of antibiotics is MRSA resistant to?
Beta-lactam
When ‘coagulase negative staphylococci’ appears on a lab result, what does this typically indicate?
contamination or colonization
Which infection is often caused by staphylococcus saprophyticus?
UTI in women of reproductive age
Treated with nitrofurantoin (Macrobid)
What are the 3 possible hemolytic patterns?
Alpha - green
Beta - clear
Gamma - non-hemolytic
Characteristics of gram positive cocci in chains
Catalase negative
Categorized by hemolytic pattern (alpha - green; beta - clear; gamma - non-hemolytic)
NO coagulase
Two examples of Gram-positive cocci in chains that are alpha hemolytic
Streptococcus pneumonia
Viridans streptococci
What is an example of gram positive cocci in chains that is beta hemolytic?
Streptococcus pyogenes (Group A streptococcus) NO catalase
What is an example of gram positive cocci in chains that is gamma hemolytic?
Enterococcus spp (species) NO catalase
This alpha hemolytic streptococci is responsible for most community acquired pneumonias and meningitis
Streptococcus pneumoniae (pneumococci)
What are the viridans streptococci?
Grouping of all other alpha hemolytic gram positive cocci.
Part of normal oral and gastrointestinal flora
Can cause endocarditis (heart valve infection)
This is a sub-group of the viridans group that is notorious for forming abscesses throughout the body
streptococcus angionosus group
What is a Lancefield group?
How beta hemolytic gram positive cocci in chains are categorized.
A,B,C,F,G
What are some infections that can be caused by Group A streptococci?
Group A Streptococci can cause
- strep throat (pharyngitis)
- skin infections (cellulitis)
- necrotizing fasciitis (flesh-eating disease)
- bacteremia
- rheumatic fever
- glomerulonephritis (inflammation of small blood vessels in kidneys)
GAS for ToNS BaRG
What part of the body is typically colonized with enterococcus?
Gastrointestinal tract
Often isolated as part of mixed infection with other bowel flora
Can cause UTIs
What are the two most important species of enterococci?
Enterococcus faecalis
Enterococcus faecium
What is the hemolytic pattern of the enterococcus species?
Gamma (non-hemolytic)
What is VRE?
vancomycin resistant enterococci
Peptococcus and peptostreptococcus are…
Anaerobic gram-positive cocci in chains
Part of normal flora in most mucous membranes
Most often isolated as part of mixed infection (e.g. abscesses in mouth, lung, vulva, brain)
Name the 3 multi-drug resistant gram-positive cocci
Vancomycin resistant enterococci
Methicillin resistant streptococcus aureus
Streptococcus pneumoniae
MRSA is typically susceptible to which antibiotic?
Vancomycin
What is a VISA?
Vancomycin intermediate streptococcus aureus (MRSA’s that also show reduced sensitivity to vancomycin)
What is the mecA test?
Molecular testing for the methicillin resistance gene (test for MRSA)
Which parts of the body are typically colonized with MRSA?
nose and skin
Common types of infections caused by hospital acquired (HA) MRSA?
Bacteremia
Wound infections
Respiratory infections
Common types of infections caused by community acquired (CA) MRSA?
Mainly skin and soft tissue infections (cellulitis, abscesses, furuncles)
Risk factors for HA - MRSA?
Indwelling devices, catheters, lines, etc
Modes of transmission for MRSA
person-to-person
environmental (hospital equipment, sports equipment)
Animal-to-patient
Shared facilities (washrooms, changerooms)
Community acquired MRSA tends to be more susceptible to antibiotics, which are:
TMP/SMX
doxycycline
clindamycin
TDC
What is VRE?
Vancomycin resistant enterococci
Prolific in hospitals
What is the ‘van’ gene?
Vancomycin resistance gene.
Transferred by plasmids between organisms
What are the 3 most common types of ‘van’ genes?
A, B and C
Ways to control VRE:
Prevent resistance development (decrease vancomycin use)
Carrier and case detection (admission and lab isolate screening)
Containment of clinical cases (isolation practices, investigation of contacts, education programs, hand hygiene)
LID
What antibiotic can Streptococcus pneumoniae be resistant to?
Penicillin
What are the three subtypes of penicillin resistance in Streptococcus pneumoniae?
Susceptible (MIC of 0.06 mg/ml or less) Intermediate Resistance (MIC of 0.1-1 mg/ml) High level (MIC of > 1 mg/ml)
