enterics - flashcards

cause primary GI infections

opportunistic: sepsis, pneumonia, meningitis, UTI

responsible for many community-acquired and nosocomial infections

GNRs

ferment glucose

nitrate to nitrite reduction

oxidase neg (except plesiomonas)

all motile (except shig, kleb, yersinia)

facultative anaerobe

large, spready, moist, gray, cream colonies

lactose, CV and bile salts

LF = pink

NLF = colorless

lactose, sucrose, eosin Y, methylene blue

LF = green metallic sheen, blue back

NLF = colorless

lactose, sucrose, salicin, bile salts, sodium thiosulfate

LF = salmon

NLF = green/blue

lactose, sucrose, xylose, bile salts, sodium thiosulfate

LF = yellow

NLF = colorless

adherence: easy colonization

toxins: food poisoning

invasive enzymes: spreading factors

serology

ESBLs

CRE: R to imipenem, meropenem, doripenem, ertapenem OR CPE

CPE: k. pneumonia (KPC); MBL carbapenemases; NDM

automated methods, E-test, kirby bauer

• CLSI breakpoints

• ertapenem testing good for CPE

detection: infection control

• modified hodge test, carbaNP test, neo rapid CARB test

H Ag: heat stable, flagellar (motility)

O Ag: heat stable somatic in cell wall (LPS)

K Ag: heat labile, capsular

• K1 (e. coli), Vi (salmonella)

beta hemolysis

LF

motile sex pili, fimbriae

H, O, K Ags

colon biota

ferm: glucose, lactose, trehalose, xylose

indole pos

MR pos, VP neg

neg H2S, DNase, urease, PAD, citrate

IMVC pos pos neg neg

UTIs

pili: attachment so urine flow doesn’t wash it out

cytolysins: kill immune cells/stops phagocytosis

aerobactin: allows bacteria chelate iron

infantile diarrhea children; nurseries and day cares

adhesin

malaise, low grade fever, vomiting, diarrhea with mucus

traveler’s diarrhea requires large inoculum

• watery diarrhea, abd cramps, nausea

contam food/drink

colonize small intestine via fimbriae

releases toxins:

• heat labile (LT): acts on adenyl cyclase so ATP = cAMP = hypersecretion fluids = diarrhea

• heat stable (ST): guanylate cyclase inc cGMP = hypersecretion

adults/children

dysentery with direct penetration, invasion, destruction of intestinal mucosa

similar to shigella but needs higher inoculum (non motile NLF)

watery diarrhea with scant stool, pus, mucus, blood

shiga toxin producing

O157 H7 associated with HUS

• low plts, HA, kidney failure

watery progressing to bloody diarrhea no pus

• fatal in young kids/elderly

• undercooked meats, unpasteurized milk, apple cider, bean sprouts, spinach

verotoxin I: phage mediated cytotoxin aka shiga toxin (Stx)

• damages vero cells (african green monkey kidney cells)

• neutralized by shiga toxin Abs

verotoxin II

• neutralized by shiga toxin Abs

stool culture on differential media

• serotyping

• O157 H7 on SMAC plate

shiga toxin in stool

4x or greater in STEC Ab titer

MAC containing sorbitol

O157 H7 does not ferment sorbitol = colorless

• send for serotyping if neg

other e. coli = pink

tests ability to produce beta-glucuronidase

• breaks down MUG = 4-methylumbelliferone

  • fluoresces blue in long wave UV

rapid ID non EHEC strains

• EHEC do not produce enzyme

• send for serotyping if neg

diarrhea and UTIs

adheres to surface of small intestine via fimbriae

water diarrhea, dehydration, vomiting, occ abd pain

• lasts 2+ wks

commensals from colon with special adherence = UTIs

• culture with Hep2 cells = aggregative pattern stacked brick

meningitis common in neonates/young children

• infected just before/during delivery or with amniotic fluid

capsule Ag K1: predisposition for meningitis

bacteremia in adults from UTI or GI source

presumptive: oxidase neg, indole pos, GNR

additional tests for definitive ID

• beta hemolytic, lactose pos/PYR neg OR

• MUG pos

additional notes:

• isolate must be large colonies and not from GI specimen

opportunistic/nosocomial infections (pneumonia, UTI, wounds)

citrate pos

neg H2S, phenylalanine deaminase, indole

MR neg VP pos

IMVC: neg neg pos pos

non motile

LF

mucoid

pneumonia, oxytoca, ozaenae

most common isolate

LRT in hospital pts, UTIs, bacteremia, wounds

moist gray mucoid

polysaccharide capsule prevents phagocytosis

KPC is concern from plasmid transfer

similar to k. pneumoniae but indole pos

affects similar sites

isolated from nasal secretions/cerebal abscesses

plasmid mediated ESBLs contribute to resistant seen in nosocomial infections

MR neg VP pos

motile

citrate pos

usually produce ornithine decarboxylase

• lysine decarboxylase not in e. cloacae

infections in wounds, urine, blood, CSF

formerly enterobacter

yellow

formerly enterobacter

yellow

meningitis/bacteremia from powdered infant formula

ONPG pos (SLF)

DNase pos

highly resistant to antimicrobials

adorifera = dirty, musty odor

rubidaea = red at RT

most clinically relevant

red pigment

nosocomia UTI, resp infections

bacteremic outbreaks in nurseries, cardiac surgery, burn units

delayed citrate rxn

environmental and human samples

• gastroenteritis isolated from stool cultures

isolated from urine, wounds, ear, blood infections

swarmers on non selective media

burnt chocolate odor

pos H2S, NLF, PAD, urease

indole neg

ornithine decarboxylase pos

if amp “R”

• maltose neg

• penneri = ornithine neg, maltose pos

indole pos

ornithine decarboxylase neg

ferments sucrose (Y/Y TSI)

UTIs and possible diarrhea

motile

citrate neg

PAD pos

rettgeri: UTI, nosocomial outbreaks

stuartii: nosocomial burn unit outbreaks and isolated in urine cultures

highly resistant to antimicrobials

citrate pos

bacteremia and wound infections

urea neg

lysine decarboxylase pos

H2S pos

indole pos

citrate neg

freundii: most common

• nosocomial UTIs, pneumonias, endocarditis rare, intraabd abscesses

koseri: nursery outbreaks of neonatal meningitis, brain abscesses

weak urease

LF

citrate pos

MR pos

H2S pos

resembles salm on media but neg lysine decarboxylase (salm pos)

specimen collection/transport

isolation/ID (sterile vs non sterile)

• full ID on stools

stools

• looking for NLFs

• XLD, GN, HE, CIN, SS, SMAC

serology for salm/shig