Enterobacterales Overview and Infections

These flashcards cover essential vocabulary and key concepts related to Enterobacterales, their taxonomy, pathogenic mechanisms, and associated infections.

Enterobacteriaceae

A family of bacteria that includes pathogens like Escherichia, Salmonella, and Klebsiella.

Escherichia coli

A common bacterium that can be pathogenic; includes serotypes like ETEC and EHEC.

is enterobacteria a Facultative anaerobe?

yes

Labile toxin (LT)

A toxin produced by Enterotoxigenic E. coli (ETEC) whose action is similar to cholera toxin.

Shiga toxin (Stx)

A cytotoxin produced by certain strains of E. coli (EHEC) that can lead to severe intestinal disease.

Hemolytic uremic syndrome (HUS)

A condition characterized by kidney failure and low platelet count caused by toxin-induced damage.

Typhoid fever

A serious illness caused by Salmonella Typhi, primarily characterized by fever and abdominal pain.

Selective culture media

Media used to isolate specific types of bacteria, such as SMAC or XLD agar for Enterobacteriaceae.

Capsular (K) antigen

An antigen present in some bacteria that aids in the diagnosis and identification of certain species.

Serotyping

A method of identifying and classifying organisms based on their antigens.

CIN agar

A selective medium used for isolating Yersinia species.

Epidemiology of Salmonella

Salmonella infections are commonly transmitted through contaminated food sources, leading to gastrointestinal illness.

E. coli O157:H7

A serotype of E. coli strongly associated with hemorrhagic colitis and other serious health issues.

motility

most are motile generally have peritrichous flagella except KLEBSIELLA and SHIGELLA

enterobacteria characteristics

Gram neg bacilli, oxidase neg except plesiomonas, facul anarobe, ferment glucose, reduce nitrate to nitrite

what are the 3 antigenic expressions?

sOmatic (O) antigen, Flagellar (H) antigen, Capsular (K) antigen

capsular K antigen K1

E.coli meningitis

capsular K antigen Vi

S.Typhi typhoid fever

where is E.coli found and what does it cause? enteroinvasive(EIEC)

primarily found in children in developing countries, most common cause of travelers diarrhea.

E. coli produces 1 or 2 cytotonic toxins which are? enteroinvasive(EIEC)

LT (labile toxin) action identical to CT (cholera toxin, vibrio cholerae)

ST (stable toxin)

symptoms and diagnosis of E.coli enteroinvasive(EIEC)

watery diarrhea and abdominal cramping

multiplex PCR assays to detect toxins, antibiotics not warrented, hydration is key

Enteropathogenic E. coli (EPEC)

attaching and effacing lesions, adheres to enterocytes, symptoms fever, malaise, vomiting, diarrhea with prominent amount of mucus Not grossly bloody

enterohemorrhagic E.coli (EHEC)

shiga toxin producing E. coli (STEC) or verotoxin produing E. coli (VTEC)

causes hemorrhagic diarrhea and colitis

strongly associated with O157:H7 and O157:NM

other more commonly encountered strain O26, O111

infections due to enterobacteriaceae two phage-encoded cytotoxins

shiga toxin 1 (Stx1) verotoxin 1; VT1) indentical to the cytotoxin/neurotoxin/enterotoxin/ of shigella dysenteriae type 1 (shiga toxin, Stx)

can be neutralized by Ab to Stx

A/B subunits

shiga toxin 2 (Stx2, VT2) different phagem but same activity against eukaryotic ribosomes, toxins NOT neutralized by antibody to shiga toxin

what are the symptoms due to shiga toxin 1 and 2

severity related to quantity of tocins produced

1 hemorrhagic diarrhea

2 colitis

3 Hemolytic uremic syndrome (HUS)

due to circulating toxins, microvascular damage, microangiopathic hemolytic anemia, thrombocytopenia, acute renal failure

antimicrobial therapy may increase the risk for HUS

epidemiology of enterobacteriaceae

EHEC can be transmitted in undercooked hamburher meat and produce

processed foods cookie dough and soy nut butter outbreaks

unpasturized dairy products and apple cider

person to person fecal oral route

petting Zoos

diagnosis Enterobacteriaceae

stool culture using selective and differential media

SMAC (maconkey agar with sorbitol)

MUG testing B glucoronidase activity

serotyping for O157

molecular detection of stx1 and stx2

treatment Enterobacteriaceae

supportive only

enteroaggregative E. Coli (EAEC)

associated with persistent diarrhea in children and can last 2 or more weeks

many different serotypes involved

diffusley adhering E coli (DAEC)

UTIs and watery diarrhea associated with chronic or recurring UTIs

extraintestinal infections: many sites includes HAIs; invasive strains can be positive for K1, aerobactin, hemolysin and fimbriae

UTIs #1 cause

septicemia (endotoxic shock LPS)

meningitis (neonates K1 capsular most common)

pneumonia

wounds

Escherichieae - escherichia 6 species

EMB, MacConkey

key reactions: LF+, ONPG + , Indole +, VP-, Cit-

clinical and lab standards institute (CLSI) abbreviated tests

Beta-hemolytic, Oxidase (-), spot indole (+)

what salmonella species is important

S.enterica containing 6 subspecies

Infections Due to Enterobacteriaceae pathogenesis

Gastroenteritis- req. large dose invades intestinal mucosa

virulence LT like toxin

symp: NVD fever chills 8-36 hrs after ingestion self limiting

Infections Due to Enterobacteriaceae Typhoid (enteric) fever

S.Typhi humans only known reservoir

20% fatal without treatment,

sympt; fever lethargy bactermia

later symp. penumonia bowl porforation, meningitis absccesses and endocarditis

Infections Due to Enterobacteriaceae septicemia (not S.Typhi)

S.Typhimurium, S.Choleraesuis, and S.dublin

diagnosis; stool culture then sent to health lab + molecular detection

biochem testing salmonella enterica

culture screen for salmonella: HE or XLD agar

key tests: ONPG (-) H2S (+) LDC (+) Cit (+)

what is different about S. Typhi for biochem testing?

only serotype that does not produce gas from glucose

Shigella is motile or non?

nonmotile

what are the 4 species and serogroups of shigella?

A= S.dysenteriae B=S.flexneri C=S.boydii D=S.sonnei

way to remember (notebook)

shigella infect. causes

symp; variable S.dysenteriae type 1 is the most severe, can cause hemolytic uremic syndrome (HUS)

Yersinia Y. enterocolitica

resembles appendicitis (inflamed)

has been associated with blood transfusions

Yersinia Y. enterocolitica

Mesenteric lymphadenitis

Yersinia Y. pestis

plague/black death

Zoonosis of rats and other rodents

bubonic, septicemic, pneumonic

infections due to yersinia

skin hemorrhage (petechiae), lymphadenopathy, necrosis in extremities

yersinia virulence mechanisms

capsule and F1 antigen

FIP

endotoxin

yersinia ID Pestis, Pseudotuberculosis, enterocolitica

selective and differential medium: cefsulodinirgasan-novobiocin (CIN)

some yersinia strains Enterocolitica and pneudotuberculosis recovery enhanced by?…

cold enrichment

yersinia strains entero, pseudo are

more active at 25 degrees C than 37

motile at room temp

enteric pathogens are?,,,

Urease positive

Y.pestis ID

tier 1 select agent

klebsiella most common species iso, produces Large polysaccharide capsule + clinical manifestations

UTIs pneumoni bactemia, abscesses and wounds (opportunistic and HAIs)

klebsibella gram stain

Negative and bacilli

klebsiella can

produce extended spectrum beta lactamases (ESBLs)

kleb pneu carba (KPC)

kleb variicola

identical to K. pneumoniae emerging human pathogen

kleb oxytoca

Indole + colonies are not usually mucoid

kleb granulomatis causes

Granuloma inguinale (STI) can resemble chancroid

beefy red lesions that are PAINLESS

kleb granuloma inguinale diagnosis

non culturable, examination of stained smears for Donovan bodies

kleb ID

Nonmotile, VP+ mucoid/wet colonies

K. pneu and K. cola

indole (-)

K. oxytoca

Indole +

K. Ozaenae

atrophic rhinitis VP neg

K. rhin

rhinoscleroma

VP neg

K. aerogenes

ODC +

Plesiomonas shigelloides

a pathogenic bacterium associated with gastroenteritis. extraintestinal infections- wounds (exposure to water)commonly on extremities

ID P.Shigelloides

oxidase + o/129 (S)

Morganellaceae

proteus, morganella, and providencia cause

UTIs wounds bacteremia and proteus is an important cause of HAIs (UTIs from indwelling catheters)

morganellaceae is

Phenylalanine deaminase (PDA) positive and non lactose fermenters on Mac

morgan proteus has what on a agar plate?

Swarming motility

morganella single species may appear weakly beta hemo on SBA with age and is

Indole +

providencia

Indole + and H2S -

Edwardsiella only one known to be an opportunistic human pathogen E.tarda

Indole + H2S +

citrobacter

UTIs intraabdominal abscesses HAI- UTI most common pneumonia

Citrobacter 2 most common species

C. freundii H2S +

C. koseri indole + cause of nursery outbreaks of neonatal meninfitis

Clt +

enterobacter most common E.cloacae

UTIs wounds pneumonia bactermia meningitis

enterobacter

colonies resemble klebsiella but not as mucoid and motile

important Serratia species

S. marcescens

clinically sig way of ID seratia

DNase + ONPG +

pantoea

rare human pathogen, all amino neg yellow pigmented colonies

Hafnia

only one species Hafnia alvei rare human pathogen UTIs and wounds

Cronobacter (enterobacter) sakazakii

Infant meningitis and bacteremia

outbreaks due to powdered infant formula

yellow pigment 98%

Vibrio

gram - curved bacilli

ferment glucose

oxidase +

halophilic

Gram neg bacilli with oxidase - is?

enterobacterales

gram - bacilli oxidase + and ferments is?

vibrio, aeromonas, plesiomonas

gram - oxidase + and oxidizer is?

pseudomonas

vibrion

aquatic organisms, temperature sensitive increase in spring-summer

v.cholerae virulence

colonizing human intestines involes chemotaxis mucinase and attatchment pilli

enterotoxin: choleragen cholera toxin

v. cholerae pathogenesis

cholera (severe secretory diarrhea)

numerous “rice water stools”

severe dehydration

v. cholerae ID what agar?

TCBS

v. cholerae characteristics

oxidase +, gluc +, Suc + (yellow on TCBS)

v. cholerae treatment

Fluid replacement and Doxycycline

V. parahaemolyticus

acute gastroenteritis

raw or undercooked seafood

V. parahaemolyticus ID

halophilic growth on TCBS suc - LDC + ADH -

V. vulnificus pathogens

septicemia- consuming raw oysters

wounds- cause necrotizing faciitis

V. alginolyticus

extraintestinal infections eye and ear infections, wounds

V. alginolyticus ID

halophilic growth on TCBS suc + LDC + ADH - VP +

aeromonas

widely distributed in nature

acute diarrhea

cellulitis

septicemia