WK 5 - Entero Flashcards
all ENTEROBACTERIACEAE are
Cytochrome oxidase negative, except
Plesiomonas
all ENTEROBACTERIACEAE are
All reduce nitrate to nitrite, except for
Photorhabdus and
Xenorhabdus
all ENTEROBACTERIACEAE are
All are motile at body temperature, except for
Klebsiella, Shigella, and Yersinia
In ENTEROBACTERIACEAE,
None has remarkable colony morphology on supportive
media, appearing large, moist, and gray on SBA, CHOC,
and most non-selective media;
except Klebsiella, Proteus,
and some Enterobacter species
characteristics of entero
- Often referred as enterics
- Gram-negative bacilli/coccobacilli
- Non-spore forming, facultatively anaerobic bacilli
- Cytochrome oxidase negative, except Plesiomonas
- All are glucose-fermenting
- All reduce nitrate to nitrite, except for Photorhabdus and
Xenorhabdus - All are motile at body temperature, except for
Klebsiella, Shigella, and Yersinia - None has remarkable colony morphology on supportive
media, appearing large, moist, and gray on SBA, CHOC,
and most non-selective media; except Klebsiella, Proteus,
and some Enterobacter species
what media should be used for entero
- Colony morphology on non-selective media, such as SBA
and CHOC are of little value in their identification - A wide variety of differential and selective media such as
MAC and EMB (Eosine Methylene Blue), highly selective media such as HE and XLD are available for presumptive identification of enteric pathogens
what does entero ferment
lactose and sucrose
Species that produce H2S may be readily distinguished
when placed on
HE or XLD agar
_______ contain _____________ which produce
blackening of H2S-producing colonies
HE and XLD agars contain sodium thiosulfate and
ferric ammonium citrate, which produce
blackening of H2S-producing colonies
can
inactivate extended-spectrum cephalosporins (e.g.,
cefotaxime), penicillins, and aztreonam
plasmid-mediated
extended-spectrum β-lactamases (ESBLs)
Increasing numbers of ______________ clinical strains produce plasmid-mediated
extended-spectrum β-lactamases (ESBLs)
Increasing numbers of E. coli, K. pneumoniae, and K.
oxytoca clinical strains produce plasmid-mediated
extended-spectrum β-lactamases (ESBLs)
Antigens used in the identification of different serologic
groups
o O antigen (somatic) – heat-stable, located on the cell
wall
o H antigen (flagellar) – heat-labile, surface of flagella,
responsible for motility
o K antigen (capsular) – heat–labile polysaccharide
found only in certain encapsulated species
o K1 antigen of E. coli
o Vi antigen of Salmonella enterica subsp. enterica
serotype Typhi
Most enteric reside in the GI tract except for
Salmonella,
Shigella, and Yersinia
Initially considered a harmless member of colon resident
biota
e coli
Primary marker of fecal contamination in water
purification or water quality testing
e coli
vf of e coli
Most strains are motile and generally possess adhesive
fimbriae and sex pili, and O, H, & K antigens
is often useful in
identification of strains, particularly those associated with
serious enteric disease
Serotyping for O and H antigens
often masks the O antigen during bacterial
agglutination testing with specific antiserum
K antigen
– identical to capsular antigen found in
Neisseria meningitides group B
K1 antigen
how does e coli appear in agar
- Appears as a lactose-positive (pink) colony with a
surrounding area of precipitated bile salts on MAC agar - Appears with a green metallic sheen on EMB agar with the
propoerties of e coli in emb agar
following properties:
o Glucose, lactose, trehalose, and xylose fermentation
o Indole production from tryptophan
o Glucose fermentation by mixed acid pathway:
o methyl red positive, Voges-Proskauer negative
o Does not produce H2S, DNase, Urease or
phenylalanine deaminase
o Can’t use citrase as sole carbon source
- Most common cause of UTI in humans
Uropathogenic E. Coli
Causes acute pyelonephritis in immunocompetent hosts
are dominant resident in colon
Uropathogenic E. Coli
Uropathogenic E. Coli
vf
- Resistant to antibacterial activity of human serum
- Pili – adhesion to epithelial cells - Cytolysins (hemolysins) – kill immune factor
cells and inhibit phagocytosis and chemotaxis of
certain WBCs - Aerobactin – chelates iron
kill immune factor
cells and inhibit phagocytosis and chemotaxis of
certain WBCs
Cytolysins (hemolysins)
Associated with diarrhea of infants and adults in tropical
and subtropical climates, especially in developing
countries
Enterotoxigenic E. coli (ETEC)
- Major causes of infant bacterial diarrhea
Enterotoxigenic E. coli (ETEC)
etec
- High infective dose (106-1010 organisms) to initiate
disease in an immunocompetent host - Stomach acidity inhibits colonization and initiation of
disease - Colonization on proximal small intestine is mediated by
fimbriae that permits binding on intestinal microvilli - Heat-labile toxin (LT) – similar in action and amino acid
sequence to cholera toxin from V. cholera - LT fragment A – enzymatically active portion
- Lt fragment B – moiety, binding portion, confers specificity, binds to the mucosa and providing entry for A portion
detect ETEC in
fecal specimens
Enzyme-labeled oligonucleotide probes
Produce dysentery with direct penetration, invasion,
and destruction of the intestinal mucosa
Enteroinvasive E. coli (EIEC)
Diarrheal illness is similar to that of Shigella spp.
although infective dose of EIEC is much higher
eiec
entericthat cause Fever, severe abdominal cramps, malaise, and watery
diarrhea
eiec
eiec
- Strains can be non-motile and generally don’t ferment
glucose - Don’t decarboxylate lysine
- Sereny test – ability to produce keratoconjunctivitis in the
guinea pig - It is also possible to detect invasiveness using monolayer
cell cultures with HEp-2 cells (human epithelial-2 cells)
- Causes infantile diarrhea
Enteropathogenic E. coli (EPEC)
epec
- Adhesive property
- Only certain H antigenic types within each O serogroup are
connected to intestinal infections - O serogrouping can’t differentiate this E. coli strain from strains of normal biota
- Low-grade fever, malaise, vomiting, diarrhea
- Stool contains mucus, no blood present
- identify EPEC
Serologic typing with pooled antisera
strain associated with hemorrhagic diarrhea,
colitis, and hemolytic uremic syndrome (HUS)
O157:H7 eec
eec
- Stool has NO leukocytes
- HUS is characterized by low platelet count, hemolytic
anemia, and kidney failure - Watery diarrhea that progresses to bloody diarrhea
with abdominal cramps, low-grade fever or absence of
fever, no WBCs, distinguishing it from dysentery caused by
Shigella spp. or EIEC infections
biologically similar to, immunologically
different from, both Stx and verotoxin I. Not neutralized
by antibody to Stx
verotoxin ii
Verotoxin I
phage-encoded cytotoxin identical to
Shiga toxin (Stx) produced by S. dysenteriae type I
- Produces damage to Vero cells(African green
monkey kidney cells) - Reacts with and is neutralized by the antibody
against Stx
Verotoxin producing E. coli may be identified by one of
three methods
o Stool culture on highly different medium, with subsequent
serotyping
o Detecting verotoxin in stool filtrates
o Demonstration of a fourfold or greater increase in verotoxin
neutralizing antibody titer
verotoxin is associated with
eec
Stool culture for O157:H7 may be performed using
MAC
agar containing sorbitol (SMAC) instead of lactose.
O157:H7 does not ferment sorbitol in 48 hours, and
appears colorle
Generally associated with two kinds of human disease:
diarrheal syndromes and UTIs
Enteroadherent E. coli (EAEC)
- Two types of EAEC
o DAEC
– associated with both UTIs and diarrheal
disease
- Uropathogenic strains are closely associated with
cystitis in children and acute pyelonephritis in
pregnant women - Chronic or recurring UTI
o EAEC
– causes diarrhea by adhering to the surface
of the intestinal mucosa
- Adheres to HEp2 cells, packed in an aggregative
“stacked-brick” pattern on the cells and between
the cells by means of fimbriae - Watery diarrhea, vomiting, dehydration,
occasional abdominal pain, mostly in children
extraintestinal infection of e coli
- Newborn usually acquires infection in the birth canal just
before or during delivery, when the mother’s vagina is
heavily colonized. Infection may also result if contamination
of the amniotic fluid takes place - Septicemia and meningitis
- Capsular antigen K1 is the most documented virulence
factor associated with neonatal meningeal infections - E. coli bacteremia in adults may result primarily from a
urogenital tract infection or from a GI source
Other Escherichia Species
- E. hermanii (formerly E. coli atypical/enteric group II) –
yellow-pigmented organism isolated from CSF, wounds,
and blood - E. vulneris – infected wounds, more than half the strains
also produce yellow colonies - E. albertii – diarrheal disease in children
Usually found in the intestinal tract of humans and animals
or free-living in soil, water, and on plants
KLEBSIELLA
Associated with a number of opportunistic and nosocomial
infections (e.g. pneumonia, wound, UTI)
KLEBSIELLA
KLEBSIELLA
- Most grow on Simmons citrate and in potassium cyanide broth
- None produce H2S
- Few hydrolyze urea slowly
- Negative reaction with methyl red test
- Positive reaction with Voges-Proskauer test
- With few exceptions, indole is not produced from tryptophan
- Motility varies
- Hospital acquired outbreaks of Klebsiella resistant to
multiple antimicrobial agents (due to plasmid transfers)
K. pneumoniae
- Most commonly isolated species
- Distinct feature of possessing a polysaccharide capsule,
protecting against phagocytosis and antimicrobial
absorption, also responsible for moist, mucoid colony
appearance - Capsule is sometimes helpful in providing presumptive
identification - Colonization in respiratory tracts of hospitalized patients
increases with the length of stay - Frequent cause of lower respiratory tract infections among hospitalized patients and in immunocompromised hosts
- Antimicrobial resistance is most severe with K. pneumoniae
because of presence of K. pneumoniae carbapenemase
k neumoniae can also cause
- Wound infections, UTIs, bacteremia, liver abscesses
Identical to K. pneumoniae except for its production of
indole and ornithine-positive isolates
K. oxytoca
K. pneumoniae subsp. ozenae
- Isolated from nasal secretions and cerebral abscesses
- Causes atrophic rhinitis
- Highly associated with the presence of plasmid mediated
ESBLs, contributing to large numbers of nosocomial
infections seen today
K. pneumoniae subsp. rhinoscleromatis
Isolates from patients with rhinoscleroma, an infection of
the nasal cavity, manifesting as an intense swelling and
malformation of the entire face and neck
K. ornithinolytica (Raoultella)
- Indole positive
- Ornithine decarboxylase positive
- Isolated from urine, respiratory tracts, and blood along with
K. planticola
K. planticola (Raoultella)
- Isolated from urine, respiratory tracts, and blood
- Difficult to distinguish from K. pneumoniae
- Isolated from sterile sites
K. variicola
ENTEROBACTER, CRONOBACTER, PANTOEA
*motile
- Enterobacter – composed of 12 species
- Colony morphology resembles that of Klebsiella when
growing on MAC - Grow on Simmons citrate medium and in potassium
cyanide broth - Methyl red = negative
- Voges-Proskauer = positive
- Usually produce ornithine decarboxylase, unlike
Klebsiella - Lysine decarboxylase is produced by most species but not by E. gergoviae or E. cloacae
o Most common isolates
o Wounds, urine, blood, CSF
in enteric
- E. cloacae and E. aerogenes
Gained notoriety with a nationwide outbreak of
septicemia resulting from contaminated IV fluids
Pantoea agglomerans
Includes species that are lysine, ornitihine, and arginine
negative or “triple decarboxylases negative”
Pantoea agglomerans
Pantoea agglomerans HG XII
- May produce a yellow pigment
- Primarily a plant pathogen
Found in respiratory samples and is rarely isolated from
blood cultures
E. gergoviae
Cronobacter sakazaki
- Typically produces a yellow pigment
- Pathogen in neonates causing meningitis and bacteremia,
often coming from powdered infant formula - Isolated from cultures taken from brain abscesses and
respiratory wound infections
- Isolated from blood, wounds, and sputum
E. hormaechei
E. asburiae
- Biochemically similar to E. cloacae
- Isolated from blood, urine, feces, sputum, and wounds
- Associated with osteomyelitis following traumatic wounds
E. cancerogenus (formerly E. taylorae)
E.dissolvens and E. nimipressuralis
- Newly recognized species with unknown clinical
significance
SERRATIA
- Opportunistic pathogens associated with nosocomial
outbreaks - Ferments lactose slowly and positive for orthonitrophenyl galactoside (ONPG) test, except S. fonticola
- Differentiate from other members of the tribe by their
ability to produce extracellular DNase - Resistance to a wide range of antimicrobials
- Ferments lactose slowly and positive for orthonitrophenyl galactoside (ONPG) test, except
serratia
S. fonticuli
Often produce pink to red pigment, prodigiosin, especially
when isolates are incubated at room temperature
S. marcescens, S. rubidaea, S. plymuthica
most clniicaly sig serratia
- S. marcescens is the most clinically significant
Frequently found in nosocomial infections of the urinary
and respiratory tract and in bacteremia outbreaks in
nurseries and cardiac surgery and burn units
serattia
Contamination of antiseptic solution used for joint injections
has resulted in an epidemic of septic arthritis
serattia
S. odorifera
- Contains two biogroups
- Emits a dirty, musty odor resembling that of potatoes
o Biogroup 1 – isolated predominantly from respiratory
tract and is positive for sucrose, raffinose, and
ornithine, may be indole positive (60%)
o Biogroup 2 – negative for sucrose, raffinose and
ornithine and has been isolated from blood and CSF,
may also be indole positive (50%)
Isolated from a number of anatomic sites in humans and in
the environment
HAFNIA
grows in the beer wort of breweries
and has not been isolated clinicallyE
H. alvei biotype 1
Delayed positive citrate reaction is a major
characteristic
HAFNIA
Not known to cause gastroenteritis but is occasionally
isolated from stool cultures
HAFNIA
distinguished from other members of
Enterobacteriaceae by virtue of the ability to deaminate
phenylalanine
Tribe Proteeae
does proteus ferment lactose
noooo
proteus spp
- Four species: P. mirabilis, P. vulgaris, P. penneri and P.
myxofaciens - P. mirabilis and P. vulgaris – human pathogens
Ascend the urinary tract, causing infections in both lower
and upper urinary tract
proteus
Can infect proximal kidney tubules and can cause acute
glomerulonephritis, particularly patients with urinary tract
defects or catheterization
proteus
Produce “swarming” colonies on nonselective media
such as SBA
P. mirabilis and P.vulgaris
is a result of regulated cycle of differentiation
from standard vegetative cells (swimmers) to
hyperflagellated, elongated, polyploidy cells
(swarmers) capable of coordinated surface movement
Swarming
P. mirabilis and P.vulgaris
Swarmer cells produce distinct odor described as “burnt
chocolate” and plays a role in the ascending nature of
Proteus-associated UTIs
P. mirabilis and P.vulgaris
proteus characteristics
- Produces H2S and hydrolyzes urea
- P. mirabilis doesn’t produce indole from tryptophan and is
ornithine positive - P. vulgaris produces indole and is ornithine negative, and
ferments sucrose, therefore giving an acid/acid reaction
in TSI agar (triple sugar iron agar)
P. penneri
- Can also swarm on nonselective media
- Isolated from patients with diarrhea, although the role of
organism in disease hasn’t been proven
P. myxofaciens
- Isolated only from gypsy moths
- Large amount of slime it produces
morganella
- A documented cause of UTI and has been isolated from
other human body sites - Neither species have been implicated in diarrheal illness
two subspecies
o M. morganii subsp. morganii
o M. morganii subsp. Sibonii
P. rettgeri
- Documented pathogen of the urinary tract and has
caused occasional nosocomial outbreaks - Implicated in diarrheal disease among travelers
P. stuartii
- Implicated in nosocomial outbreaks in burn units and has
been isolated from urine cultures - Infections caused by P. rettgeri and P. stuartii, especially
in immunocompromised patients, are particularly difficult
to treat because of their resistance to antimicrobials
P. alcalifaciens
- Most commonly found in feces of children with diarrhea
- Role as cause of diarrhea hasn’t been proven
- Formerly identified as a strain of P. alcalifaciens
p rustgiani
Rarely isolated
* Pathogenicity also remains unproven
P. heimbachae
- Yet to be isolated from any clinical specimens
edwardsiella
- Negative for urea
- Positive for lysine decarboxylase, H2S, and indole
- Don’t grow on Simmons citrate
e. tarda
- Only recognized human pathogen
- Opportunist, causing bacteremia and wound infections
- Pathogenic role in cases of diarrhea remains controversial
e. hoshinae
- Isolated from snakes, birds, and water
e. ictalurid
- Causes enteric septicemia in fish
ERWINIA AND PECTOBACTERIUM
- Plant pathogens
- Not significant in human infections
- Erwinia grows poorly at body temperature and fails to grow
in selective media such as EMB and MAC - Identification is more for academic interest than evaluation
of their significance as causative agents of infection
CITROBACTER
- Most hydrolyze urea slowly and ferment lactose,
producing colonies on MAC agar that resemble those of E.
coli - All grow on Simmons citrate medium and give positive
reactions in the methyl red test
C. freundii
- Isolated in diarrheal stool cultures
- Pathogenic role remains unestablished
- Associated with infectious diseases acquired in hospital
settings - UTI, pneumonias, intra-abdominal abcesses have been
reported - Associated with endocarditis in IV drug abusers
- Most (70%) hydrolyze urea, but all fail to decarboxylase
lysine, whereas Salmonella fails to hydrolyze urea and most
isolates decarboxylate lysine - Pathogen documented as the cause of nursery
outbreaks of neonatal meningitis and brain abscesses
how to diff c freundi from salmonella
- Because most (80%) C. freundii produce H2S, and some strains (50%) fail to ferment lactose, the colony morphology
on primary selective media can be easily mistaken for that
of Salmonella when isolated from stool cultures - Differentiation can be done through urea hydrolysis and
lysine decarboxylase
c freundi most (70%) hydrolyze urea, but all fail to decarboxylase
lysine, whereas Salmonella fails to hydrolyze urea and most
isolates decarboxylate lysine
C. koseri
Frequently found in feces, but no evidence has been found
that it is a causative agent of diarrhea
C. amalonaticus
Isolated from sites of extraintestinal infections, such as
blood and wounds
Humans acquire the infection by ingesting the
organisms in contaminated animal food products or
insufficiently cooked poultry, milk, eggs and dairy
products
salmonella
inhabit gi tract of animals
salmonella
shigella
o Human carriers
o No animal reservoir
o Shigella dysentery usually indicates improper sanitary
conditions and poor personal hygiene
o Transmitted by wild and domestic animals
yersinia
Infections range from GI disease to mediastinal
lymphadenitis and fulminant septicemia and
pneumonia
shigella
salmonella
- Gram-negative, facultatively anaerobic bacilli that
morphologically resemble other enteric bacteria - On selective and differential media used primarily to isolate
enteric pathogens (e.g. MAC), salmonellae produce clear,
colorless, non-lactose fermenting colonies - Colonies with black centers are seen if the media (e.g. HE
or XLD) contain indicators for H2S production - In almost every case, they don’t ferment lactose
salmonella vf
o Still remains uncertain
o Fimbriated strains appear more virulent than
nonfimbriated stains
o Ability to traverse intestinal mucosa
o Enterotoxin produced by certain strains that cause
gastroenteritis is a significant virulence factor.
salmonella antigen structure
o Somatic O antigens and flagellar H antigens are the
primary antigenic structures used in serologic grouping
of Salmonellae
o Few strains may possess capsular K antigens,
designated Vi antigen
o Serologic identification of Vi antigen is important in
identifying Salmonella serotype Typhi
o Heat-stable O antigen of salmonella is the
liposaccharide (LPS) located in the outer membrane of
the cell wall.
a surface polysaccharide capsular
antigen found in Salmonella serotype Typhi and a few
strains of Salmonella serotype Choleraesuis
Heat-labile Vi antigen
often blocks the O antigen during serologic
typing but may be removed by heating
Vi antigen
2 phase of h antigen in salmonella
H antigens occur in one of two phases:
o Phase 1 flagellar antigens occur only in a small
number of serotype and determine the immunologic
identity of the particular serotype: agglutinate only with
homologous antisera
o Phase 2 flagellar antigens occur among several
strains; reacts with heterologous antisera
, also referred to as food
poisoning, occurs when a sufficient number of
organisms contaminate food that is maintained underinadequate refrigeration, thus allowing growth and
multiplication of the organisms.
most are zself limiting
salmonella gastroenteritis is
The antimicrobials of choice for salmonella include
chloramphenicol,
ampicillin, and trimethoprim-sulfamethoxazole
typhoid and enteric fever is caused by
Typhoid fever, most severe of enteric fever, caused by
Salmonella serotype Typhi; and enteric fevers caused by
other Salmonella serotypes (e.g. Salmonella Paratyphi
and Choleraesuis)
disease caysed by salmonella
o Prolonged fever
o Bacteremia
o Involvement of the reticuloendothelial system
o Dissemination to multiple organs
o A febrile disease
whatcauses typhoid fever
Improper disposal of sewage, poor sanitation, and lack
of a modern water system have caused outbreaks of
typhoid fever when the organisms reach a water
source.
With the exception of ______ salmonellae organisms infect various animals
that serve as reservoirs and sources of human infections
With the exception of Salmonella Typhi and Salmonella
Paratyphi, salmonellae organisms infect various animals
that serve as reservoirs and sources of human infections
causes parathypoid fever
Salmonella serotypes Paratyphi A, B,
and C, and Salmonella serotype Cholerasuis
“Rose spots” (blanching, rose-colored papules around
the periumbilical region) appear during the second
week of fever
parathyphoid fever
was responsible for a
nationwide outbreak linked to peanut buttercontaining
products
Salmonella Typhimurium
symptoms of gastroenteritis
o Nausea, vomiting, fever, chills, watery diarrhea and
abdominal pain
o Symptoms usually appear within a few days, with few
or no complications
With and without extraintestinal foci of infection caused
by nontyphoidal Salmonella, is characterized primarily
by prolonged fever and intermittent bacteremia
- Nontyphoidal Bacteremia
nonthypoidal bacteremia (serotype and treatment)
Serotypes most commonly associated are
Typhimurium, Paratyphi, and Cholerasuis
o May be terminated by antimicrobial therapy if
gallbladder infection is not evident
o Cholecystectomy might be a solution
nonthypoidal bacteremia in adults and kids
o Young children – experience fever and gastroenteritis
with brief episodes of bacteremia
o Adults – experience transient bacteremia during
episodes of gastroenteritis or develop symptoms of
septicemia without gastroenteritis
shigella
- Not members of normal GI microbiota and can cause
bacillary dysentery - S. dysenteriae
- Cause bacillary dysentery
- Presence of blood, mucus, and pus in stool 1
shigella characteristics
- Non-motile
- Except for certain types of S. flexneri, they do not
produce gas from glucose - Urease negative – do not hydrolyze urea
- H2S negative – do not produce hydrogen sulfide
- No lysine decarboxylation – do not decarboxylate lysine
- Unlike Escherichia spp., Shigella spp. do not utilize
acetate or mucate as carbon source - Fragile organism
s sonnei characterisics
o Decarboxylates ornithine
o Slowly ferments lactose – delayed positive
fermentation of lactose with formation of pink
colonies only after 48 hours of incubation
o ONPG positive
