Bug Parade: Gram-Positives

staphylococcus aureus reservoir

anterior nares, skin, axillae. intestine, throat, perineum

staphylococcus aureus virulence

adhesins

small colony variants (don't get detected on plate)

antimicrobial resistance (MRSA)

toxins (toxic shock syndrome, food poisoning, scalded skin syndrome)

staphylococcus aureus diseases

skin and soft tissue: impetigo, folliculitis, furuncle, carbuncle, pyoderma, abscess, cellulitis

organ and systemic: bacteremia, osteomyelitis, empyema, arthritis, endocarditis, pneumonia

Foreign body-related infections: stick to plastics or prosthetics

staphylococcus aureus growth/screens

-beta hemolytic

-white, goldish pigment

-mid-large colony

-cocci in clusters

staphylococcus aureus identification

-catalase positive

-coagulase positive

-latex agglutination

coagulase-negative staphylococci

Staphylococcus epidermidis

Staphylococcus lugdunensis

Staphylococcus saprophyticus

Staphylococcus hominis

Staphylococcus warneri

Staphylococcus haemolyticus

coagulase-negative staphylococcus reservoir

skin, axillae, inguinal, perineal, nares

S. saprophyticus (coagulase-negative staphylococcus) reservoir

rectum, genitourinary tract

coagulase-negative staphylococcus virulence

urease

glycocalyx (biofilm): decreases opsonization, antibiotic penetration, phagocytosis, and lymphocyte proliferation

coagulase-negative staphylococcus disease

catheter - UTI

device infection - prosthetic valve endocarditis, right-sided endocarditis

coagulase-negative staphylococcus growth/screens

-non-hemolytic

-white pigment (S. lugdunensis is "yellow")

-mid-large colony

-cocci in clusters

coagulase-negative staphylococcus identification

-catalase-positive

-coagulase-negative

-S. lugdunensis: pan-susceptible

-S. saprophyticus: resistant to novobiocin

Streptococcus pneumoniae reservoir

upper respiratory tract, particularly sinus and oropharynx

more colonization in young kids (30-70% rate)

household transmission between kids and adults

Streptococcus pneumoniae virulence

antiphagocytic capsule

Streptococcus pneumoniae diseases

30% of community-acquired pneumonia (bacteremia)

meningitis (sequelae)

#1 in otitis media

sinusitis, peritonitis, rare endocarditis

Streptococcus pneumoniae growth/screen

alpha-hemolytic

mucoid or cheerio/checker colony

lancet-shaped gram-positive diplococci

Streptococcus pneumoniae identification

alpha hemolysis (leaves green remnant)

catalase-negative

bile solubility-positive

susceptible to optochin

viridans group streptococcus reservoir

oral cavity, lower GI tract, skin, female genital tract

viridans group streptococcus virulence

none - part of normal flora

can be virulent if immunocompromised

viridans group streptococcus diseases

#1 in native valve endocarditis

#1 infectious disease worldwide = cavities

bacteremia (can also be a blood culture contaminant)

viridans group streptococcus groth/screens

alpha-hemolytic

cocci in chains

viridans group streptococcus identification

alpha hemolysis

bile solubility-negative

resistant to optochin

streptococcus pyogenes reservoir

throat, skin

streptococcus pyogenes virulence

M protein: resistant to phagocytosis

erythrogenic exotoxin: scarlet fever

immune-mediated superantigen: toxic shock syndrome

streptococcus pyogenes diseases

#1 in bacterial pharyngitis

#1 in impetigo

deep soft tissue infections (erysipelas, cellulitis, flesh-eating virus)

non-suppurative sequelae: glomerulonephritis, acute rheumatic fever

streptococcus pyogenes growth/screens

beta hemolytic (large zone)

grey pigment

small colony

cocci in chains

streptococcus pyogenes identification

catalase-negative

Lancefield group A

PYR-positive

streptococcus agalactiae reservoir

lower GI tract, urogenital tract (especially female)

streptococcus agalactiae virulence

lack of antibody developed versus capsular antigens

sialic acid: inhibits activation of alternative complement cascade and prevents phagocytosis

streptococcus agalactiae diseases

early-onset neonatal disease (sepsis, pneumonia 7 days)

late-onset neonatal disease (sepsis, meningitis 3 months)

adult (invasive, SST, pneumonia, bacteremia, UTI)

streptococcus agalactiae growth/screens

beta hemolytic (small zone)

grey pigment

smallish colony

cocci in pairs

streptococcus agalactiae identification

catalase negative

Lancefield group B

hippurate hydrolysis-positive

Streptococcus groups C, F, and G

can also cause pharyngitis but do not cause sequelling or glomerular nephritis

Milleri-group streptococci

identified by the scent of butterscotch

enterococcus reservoir

lower gastrointestinal tract, less common genitourinary tract, oral, cavity, skin (perineal)

enterococcus virulence

wimpy pathogen

biofilm

antibiotic resistance

aggregation substance

enterococcus diseases

10% of UTIs

bloodstream infection

endocarditis (20% of native valve, 5% of prosthetic valve)

surgical site infection (especially abdominal)

device infection

trend toward nosocomial infection

enterococcus growth/screens

non-hemolytic

VRE often alpha-hemolytic

grey pigment

smallish colony

cocci in pairs

enterococcus identification

catalase negative

esculin positive

PYR positive

growth in 6.5% NaCl

streptococcus bovis group growth/screens

non-hemolytic

grey, small colonies

group D streptococcus, not enterococcus

"D not E"

streptococcus bovis group identification

catalase negative

esculin positive

PYR-negative

no growth in 6.5% NaCl

listeria monocytogenes reservoir

typically environmental, some animals

several opportunities to enter food production (poultry, meat, veggies, raw milk, soft cheese)

listeria monocytogenes virulence

persistence in macrophages (intracellular)

Escape host vacuole

Internalin has tropism for fetal trophoblasts

listeria monocytogenes diseases

adult sepsis, CNS disease (CLL, cancer, transplant, EtOH, age >60)

pregnancy: milkd, self-limiting, influenza-like; transplacental

listeria monocytogenes growth/screens

beta hemolytic (small zone)

grey pigment

smallish colony, bacilli in stacks

listeria monocytogenes identification

catalase positive

umbrella-like motility

esculin hydrolysis-positive

hippurate hydrolysis-positive

Bacillus reservoir

ubiquitous

spore-producer - can survive anywhere

opportunities to enter food supply

Bacillus virulence

emetic toxin

enterotoxin

bacillus diseases

anthrax (B. anthracis; cutaneous, ingestion, inhalation injection)

food-borne illness (B. cereus)

right-sided endocarditis (IVDA; can be non-cereus, non-anthracis,)

covert bioterrorism agent

bacillus growth/screens

beta hemolytic and motile is ok!

non beta hemolytic and nonmotile should be watched out for

spreading colony

spore-forming bacilli

bacillus identification

catalase positive

colony morphology helpful; B. anthracis can be tenacious

if cannot rule out B. anthracis, send to public health lab

corynebacterium reservoir

largely skin and mucous membrane

some environmental

often "along for the ride"

corynebacterium virulence

exotoxin

nasopharyngeal-adherent membrane may cause obstruction

corynebacterium diseases

diphtheria (C. diphtheriae - can also be cutaneous; vaccine-preventable)

UTI (C. urealyticum)

nosocomial, antibiotic resistant (C. jeikeium)

corynebacterium growth/screens

non-hemolytic

club, palisading bacilli (Chinese letters)

corynebacterium identification

catalase positive

often identified to genus level (catalase and gram stain)

C. diphtheriae ID at reference laboratory; + toxin testing