Enterobacterales

serotyping is mostly used in classifiying

E. coli, klebsiella, shigella, and salmonella

O (somatic) antigen

found in the outer cell wall (part of LPS)

heats stable endotoxin

k (envelope) antigen

makes up the capsule

heat liable (must heat to get to k antigen)

H (flagellar) antigen

only in motile organisms

heat liable

used to serotype salmonella

gram negative bacilli and coccobacilli

found naturally in the environment and GI tract of most mammals

enterobacterales

frequent pathogens (strict or opportunistic)

seen in bed sores

enterobacterales

ferments glucose

oxidase negative (except Plesiomonas)

reduce nitrate to nitrite

most are motile

enterobacterales

principle of oxidase test

cytochrome oxidase present in an organism will oxidize the oxidase reagent (tetramethyl-para-phenylenediamine dihydrochloride) in the prescence of oxygen and form colored compound indophenol

positive vs negative result for oxidase test

positive: purple

negative: no color

enterobacterales are _______________ for the oxidase test with the exception of plesiomonas

negative

isolation of enterobacterales proteus on BAP exhibits

swarming (but doesn’t have to)

isolation of klebsiella pneumoniae on BAP is

mucoid

isolation of e. coli on BAP may be

beta hemolytic

for a stool culture we’ll use what media to culture

XLD or HE to visualize carbohydrate fermentation and H₂S production

to enhance the recovery of salmonella and shigella what media do we use

enrichment broth which will inhibit gram-positive organisms

for early identification of E. coli what media do we use

tergitol 7 which is selectice and differential

MacConkey agar (MAC) inhibits

gram-positive organisms

gram negative lactose fermenters appear

pink

gram negative lactose-nonfermenters appear

clear/colorless

what media contains ferric ammonium citrate

hektoen (HE) and xylose-lysine-deoxycholate(XLD) which allows for visualization of H₂S production

hektoen inhibits

gram positive organisms

xylose-lysine-deoxycholate inhibits

gram positive organisms

if hektoen is alkaline it’ll stay ___________ and if there’s a change in acidity the color will change to ___________________

green, yellow-salmon

what does shigella do on xylose-lysine-deoxycholate (XLD)

this bacteria doesn’t ferment sugars in the media so it’ll keep the media red (because it’s not fermenting, no pH change occurs)

what does salmonella do on xylose-lysine-deoxycholate (XLD)

this bacteria ferments xylose but not lactose and sucrose and decarboxylases lysine (removes a carboxyl group) so it’ll keep the media red (fermentation makes it acidic but decarboxylase turns it back to alkaline)

organisms that ferment xylose, lactose, and/or sucrose do what to xylose-lysine-deoxycholate

cause it to turn yellow from being acidic

for triple sugar agar (TSI) the indicator phenol red is _______________ in acidic environments and ______________ in alkaline environments

yellow, red

if only glucose is fermented on triple sugar iron agar (TSI) then the tube shows

K/A (red, alkaline/yellow, acidic)

if glucose and lactose and/or sucrose fermented on triple sugar iron agar (TSI) then the tube shows

A/(A) (yellow, acidic/yellow, acidic with gas produced)

if H₂S is produced on triple sugar iron agar (TSI) it will

react with iron salts causing blackening in media

tube 1 shows

A/(A) (yellow, acidic/yellow, acidic with gas production)

tube 2 shows

K/A (red, alkaline/yellow acidic)

tube 3 shows

K/A (red, alkaline/yellow, acidic with H₂S production)

tube 4 shows

K/K (red, alkaline/red, alkaline)

for the triple sugar iron agar (TSI) what special step do you have to do with the lid

leave it lose to allow oxygen in

to test for H₂S production you need

a source of sulfer

an H₂S indicator (iron salt)

testing for H₂S production is useful in differentiating

salmonella (+) and shigella (-)

principle of motility test

semisolid media with a small amount of agar allows motile bacteria to grow out from the line of inoculation

positive vs negative motility

positive: diffuse growth extending from stab line

negative: growth only at line of inoculation

positive vs negative result for tube indole

positive: red

negative: yellow/clear

__________ reagent is recommended for enteribacterales for tube indole

kovac’s

__________ reagent is recommended for nonfermenters for tube indole

ehrlich’s

principle for tube indole

tryptophanase converts tryptophan to indole which reacts with kovac’s or ehrlichs reagent to form a red product

principle for rapid indole

tryptophanase converts tryptophan to indole which reacts with DMACA to form a blue green color

methyl red test is used to

see if organisms is undergoing mixed acid fermentation (converts glucose into various stable acids)

methyl red indicator is __________ in acidic pH if they’re producing stable acids

red

for the voges-proskauer a positive result is

a pink red color

citrate test principle

if organism can use citrate then ammonium hydroxide will be formed which is visualized by a blue color

positive vs negative result for citrate test

positive: blue

negative: green

positive vs negative result for ONPG test

positive: yellow

negative: clear

positive vs negative decarboxylase test

positive: red-purple

nagative: orange-yellow

for a decarboxylase test we are testing for

the enzymatic removal of carboxyl group from specific amino acids

principle of decarboxylase test

if amino acid can be decarboxylated, alkaline amines build up and increase the pH which gives off a red-purple color

for the decarboxylase test alkaline is ____________ and acidic is ______________

purple-red, orange-yellow

deaminase positive vs negative results

positibe: dark green

negative: no color change

principle of deaminase test

enzymatic removal of amino group results in a color compound with addition of ferric chloride

phenylalanine deamination turns what color

green

tryptophan deamination turns what color

brown

urease test positive vs negative

positive: pink (alkaline)

negative: yellow (acidic)

principle of urease test

urease splits urea into NH₃, CO₂, and water leading to an alkaline environment which causes a shift to pink color

what bacteria have rapid urease production

proteus and providentia

what bacteria have slow urease production

klebsiella and some enerobacter

what bacteria is a frequent isolate in clinical lab

escherichia coli

normal flora of lower gastrointestinal tract

shows flat pink colonies on MAC

indole positive

escherichia coli

infections include UTIs, appendicitis, peritonitis, wound infections, pneumonia, sepsis (usually because a UTI causes bacteria to get into bloodstream), neonatal meningitis (labor process), and gastrointestinal syndromes

escherichia coli

citrate negative

indole positive

pink on MAC

A/A on TS1 tube

escherichia coli

causes traveler’s diarrhea

enterotoxigenic escherichia coli

most important escherichia coli strain

shiga toxin-producing escherichia coli

shiga toxin producing escherichia coli is also known as

verotoxigenic escherichia coli (VTEC) or enterohemmorrhagic escherichia coli (EHEC)

produces shiga toxin 1 and 2

this strain causes bloody diarrhea and hemolytic uremic syndrome (HUS)

enterohemorrhagic escherichia coli

most associated with the strain O157:H7 which is sorbitol negative

shiga toxin-producing escherichia coli

has longer incubation

acquired from contaminated food/water or from person to person (fecal to oral route)

S/S: abdominal cramps, diarrhea that turns bloody, low grade fever, and 6% of people develop HUS

shiga toxin-producing escherichia coli

treatment for escherichia coli

oral rehydration

not normal flora, always a pathogen

most communicable of bacterial diarrheas (low dose infective)

under 100 organisms can cause an infection

self-limiting, treat with hydration

shigella

S/S: abdominal cramps, fever and pain

causes watery diarrhea for 3 days which is followed by a dysenteric phase that causes tool to contain mucous and red and white blood cells due to an endotoxin

shigella

four serogroups of shigella

shigella dysenteriae, flexneri, boydii, and sonnei

produces a neuroteoxin (more severe)

shigella dysenteriae

most frequent worldwide (most common worldwide)

shigella flexner

most common in the US (spread through daycares commonly)

shigella sonnei

nonmotile

non-lactose fermenter

biochemically inert (doesn’t do much biochemically)

K/A

shigella

two species of salmonella

salmonella enterica and bongori

motile

non-lactose fermenter

H₂S positive

citrate positive

indole negative

urease negative

deaminase negative

K/A with H₂S

salmonella

many animals carry what bacteria

nontyphoid salmonella

S/S: vomiting, diarrhea, fever, chils after ingestion of oraganism

can be a carrier

not normal flora, always pathogenic

salmonella

serotyping on this bacteria is generally done by state health labs

salmonella

most cases are associated with travel outside of the US

S/S: high sustained fever, stomach pain, constipation or diarrhea, malaise

diagnosis made by blood culture

treat with antibiotics

salmonella serotype typhi

LDC positive and ONPG negative

salmonella

does shigella ferment lactose

no, it’s clear on MAC

found in soil, fresh water, and animals

infection caused by contaminated food or water or occuational hazard

self-limiting gastroenteritis (particularly in kids)

plesiomonas shigelloides

oxidase positive

ferments glucose

non-lactose fermenter

plesiomonas shigelloides

found in soil, water, plants, but also the GI tract and upper respiratory tract

common in hospitalized patients

klebsiella

klebsiella pneumoniae ssp. pneumoniae is indole

negative

klebsiella oxytoca is indole

positive

primary bacterual pneumonia

typically in immunocompromised, elderly, and newborns

spreads person-person or contaminated equipment

klebsiella pneumoniae ssp. pneumoniae

has a prominent capsule

suspect if isolate is mucoid, large, and colonies have diffused red pigment on MAC

klebsiella pneumoniae ssp. pneumoniae

nonmotile

pink, mucoid on MAC

urease positive

produce large amounts of gas in TSI

klebsiella

found in soil, water, and the GI tract

causes UTIs, respiratory tract infections, and wound infections

enterobacter

motile

urease variable

citrate positive

lactose fermenter

indole negative

A/A

enterobacter

yellow pigment seen on BAP

ubiquitous environmental organisms, survive in dry environments

biochemically similar to enterobacter

cronobacter sakazakii

infections are associated with powdered infant formula

causes bacteremia, septicemia, meningitis, and necrotizing colitis in newborns

cronobacter sakazakii