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ENTEROBACTERIACEAE. B.A.Fontanilla , MD Department of Microbiology and Parasitology. GENERAL CHARACTERISTICS. Taxonomy Morphology Physiology Antigenic Structure Determinants of Pathogenicity Clinical Infection. ENTEROBACTERIACEAE. Large number of closely related species

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enterobacteriaceae

ENTEROBACTERIACEAE

B.A.Fontanilla, MD

Department of Microbiology and Parasitology

general characteristics
GENERAL CHARACTERISTICS
  • Taxonomy
  • Morphology
  • Physiology
  • Antigenic Structure
  • Determinants of Pathogenicity
  • Clinical Infection
enterobacteriaceae1
ENTEROBACTERIACEAE
  • Large number of closely related species

- found in soil, water, decaying matter

- found in large intestines of human, animals and

insects ----”enterics” or “enteric bacilli”

- includes causative agents of gastrointestinal

diseases

- causative agents of nosocomial infections

enterobacteriaeceae taxonomy
ENTEROBACTERIAECEAETAXONOMY
  • Cedecea
  • Citrobacter
  • Edwardsiella
  • Enterobacter
  • Escherichia
  • Ewingella
  • Hafnia
  • Klebsiella
  • Kluyvera
  • Morganella
  • Proteus
  • Providencia
  • Rhanella
  • Salmonella
  • Serratia
  • Shigella
  • Yersinia
  • Enteric group
enterobacteriaceae morphology
ENTEROBACTERIACEAEMORPHOLOGY
  • Small 0.5 x 3.0 µ
  • Gram-negative
  • non-spore-forming bacilli
  • May be motile or non-motile

If motile – peritrichous flagella

nonmotile – Shigella and Klebsiella

enterobacteriaceae2
ENTEROBACTERIACEAE
  • Biochemically diverse
  • Facultative organisms
  • When grown in anaerobic or low O2

- ferment carbohydrates

  • When grown in sufficient O2

- utilize the TCA cycle and the electron transport system for energy production

enterobacteriaceae physiology
ENTEROBACTERIACEAEPHYSIOLOGY
  • Ferment glucose
  • Reduce nitrates to nitrite
  • Do not liquify alginate
  • Oxidase negative
  • Basis for speciation within a family

- differences in carbohydrate they ferment

- variations in end-product production

- variation in substrate utilization

enterobacteriaceae cultural characteristics
ENTEROBACTERIACEAECULTURAL CHARACTERISTICS
  • On non differential or nonselective media

blood agar or infusion agar

- no species distinction

- appear as moist, smooth, gray colonies

  • Selective media -To isolate Shigella and salmonella from fecal matter
  • Differential media – selectively inhibit gram-positive organisms and to separate enterics in broad categories
enterobacteriaceae antigenic structure
ENTEROBACTERIACEAEANTIGENIC STRUCTURE
  • In serologic typing, antigenic structures are used for classification and epidemiologic studies

- Capsular (K) antigens

- Flagellar (H) antigens

- Somatic (O) antigens

enterobacteriaceae antigenic structure1
ENTEROBACTERIACEAEANTIGENIC STRUCTURE
  • Capsular (K) antigens

- Klebsiella species has a well defined

polysaccharide capsule

- in other genera, amorphous slime layer

surrounding the bacterial cell

- in E.coli – proteins and form fimbriae not

capsules

- Vi antigen of Salmonellatyphi

enterobacteriaceae antigenic structure2
ENTEROBACTERIACEAEANTIGENIC STRUCTURE
  • Flagellar antigens

- proteins

-antigenic variation is due fo differences in amino acid sequences

-antigenic typing of Salmonella is based on serologic typing of flagellar antigens

enterobacteriaceae antigenic structure3
ENTEROBACTERIACEAEANTIGENIC STRUCTURE
  • Somatic antigens

- O antigens is the most external part of the cell wall lipopolysaccharide (LPS)

- may enhance the establishment of the organism in the host.

enterobacteriaceae antigenic structure4
ENTEROBACTERIACEAEANTIGENIC STRUCTURE
  • Flagellar (H) antigens

- proteins

- antigenic variation of various flagellar

types due to differences in amino acid

sequences

- serologic typing of flagellar antigens –

basis for antigenic typing of Salmonella

typhi

enterobacteriaceae determinants of pathogenicity
ENTEROBACTERIACEAEDETERMINANTSOFPATHOGENICITY

1. ENDOTOXIN

- LPS (review structure p. 26 Jawetz)

- resides in the lipid A portion of the LPS

- produces, fever, fatal shock, leukocytic

alterations, regression of tumors, alteration

in host response to infection

- pooling of blood in the microcirculation - causing cellular hypoxia and metabolic failure due to inadequacy of blood in vital organs

enterobacteriaceae determinant of pathogenicity
ENTEROBACTERIACEAEDETERMINANT OF PATHOGENICITY

2. ENTEROTOXIN

-Toxins that affect the small intestines

- transduction of fluid in the lumen –diarrhea

3. SHIGA TOXINS AND SHIGALIKE TOXINS

(Verotoxins) – actions on Vero (African green monkey) tissue culture cells

- Shigella – toxin that interferes with protein synthesis of cells

- E.coli – hemolytic diarrhea

enterobacteriaceae determinants of pathogenicity1
ENTEROBACTERIACEAEDETERMINANTS OF PATHOGENICITY

4. COLONIZATION FACTORS

- cellular surface factors:

capsule – Klebsiellapneumoniae

“Vi” antigen – S. typhi

5. Other Factors

- ability to penetrate epithelial lining – E.coli

- Shigella

- Salmonella

escherichia1
ESCHERICHIA
  • Includes 6 species
  • 5 species associated with human disease

Escherichiablattae

Escherichiacoli

Escherichiafergusonii

Escherichia hermanii

Escherichia vulneris

escherichia coli
ESCHERICHIA COLI
  • Grows well on commonly used media
  • On enteric isolation media

– lactose fermenting colonies

  • On blood agar – β-hemolytic (assoc with UTI)
  • Majority – non-pigmented, motile
    • Produce lysine decarboxylase, use acetate as carbon source, hydrolysis of tryptophan to indole
escherichia coli1
ESCHERICHIA COLI
  • Serologic typing is based on the determination of the O antigen type, the H antigen type and when applicable the K antigen type.

- 164 O antigens

- 100 K antigens

- 50 H antigens

Example: Serotype O157:H7 – hemorrhagic colitis

Serotype O124:H30 –enteroinvasive;

bacillary dysentery

escherichia coli determinants of pathogenicity
ESCHERICHIA COLIDETERMINANTS OF PATHOGENICITY
  • Surface Factors

a. K1 capsule – E.coli with K1 capsule cause neonatal meningitis

b. O antigen

c. S fimbriae

2. Enterotoxins –produces watery diarrhea caused by the outpouring of fluids and electrolytes

- plasmid mediated

escherichia coli determinants of pathogenicity1
ESCHERICHIA COLIDETERMINANTS OF PATHOGENICITY

2. Enterotoxin – produces watery diarrhea

- plasmid mediated

a. LT enterotoxin - similar to enterotoxin of

Vibrio cholera

- stimulates adenylate cyclase in the

epithelial cells of the small intestines,

increasing perrmeability of the intestinal

lining, resulting to loss of fluids and

electrolytes

escherichia coli determinants of pathogenicity2
ESCHERICHIA COLIDETERMINANTS OF PATHOGENICITY

2. Enterotoxin

b. ST enterotoxin – ST producing E.coli do not cause diarrhea

  • Verotoxins (Shigalike Toxins)

- associated with 3 human syndrome:

- diarrhea, hemorrhagic colitis, hemolytic

uremic syndrome

- inhibit protein synthesis similar to Shigatoxin

escherichia coli determinant of pathogenicity
ESCHERICHIA COLIDETERMINANT OF PATHOGENICITY

4. Other factors

a. Enteroinvasiveness – strains have large plasmids that encode for O antigens

b. Hemolytic – strains are nephropathogenic

escherichia coli clinical manifestation
ESCHERICHIA COLICLINICAL MANIFESTATION
  • Pulmonary infections – nosocomial pneumonia

- most patients are 50 yrs or oldeer

- with underlying chronic disease

- main source: endogenous aspiration of oral secretions containing E.coli

2. Neonatal meningitis – with subsequent neurologic or developmental abnormalities

escherichia coli clinical manifestation1
ESCHERICHIA COLICLINICAL MANIFESTATION

3. Wound infections – especially occurring in the abdomen

4. Sepsis – can invade the bloodstream from any of the primary infection sites

escherichia coli clinical manifestations
ESCHERICHIA COLICLINICAL MANIFESTATIONS

5. Diarrheal disease

a. Enteropathogenic E.coli (EPEC)

- cause of infantile diarrhea

- adhere to mucosal cells of small bowell

- loss of microvilli

- produce watery diarrhea

escherichia coli clinical manifestation2
ESCHERICHIA COLICLINICAL MANIFESTATION

5. Diarrheal disease

b. Enterotoxigenic E.coli – common cause of travelers diarrhea

- some strains produce LT, plasmid mediated

- toxin activates adenylyl cyclase

- intense and prolonged hypersecretion of water and chlorides and inhibits reabsorption of sodium

escherichia coli clinical manifestation3
ESCHERICHIA COLICLINICAL MANIFESTATION

5. Diarrheal disease

c. Enterohemorrhagic E. coli (EHEC)

- produces verotoxin

- associated with hemorrhagic colitis

and hemolytic uremic syndrome

- serotype O157:H7 – most common

escherichia coli clinical manifestation4
ESCHERICHIA COLICLINICAL MANIFESTATION

5. Diarrheal diseases

d. Enteroinvasive E. coli (EIEC)

- cause bacillary dysentery in all age groups

- disease is very similar to shigellosis

- occurs most commonly in children

- invade intestinal mucosal cells

escherichia coli clinical manifestation5
ESCHERICHIA COLICLINICAL MANIFESTATION

5. Diarrheal diseases

f. Enteroaggregative E.coli (EAEC)

- causes acute and chronic diarrhea in

persons in developing countries

- produce ST-like toxins

klebsiella taxonomy
KLEBSIELLATAXONOMY

Klebsiella pneumoniae (Friedlander’s bacillus)

Klebsiella oxytoca –

Klebsiella ozeana –

Klebsiella rhinoscleromatis

klebsiella biochemical and cultural characteristics
KLEBSIELLABIOCHEMICAL AND CULTURAL CHARACTERISTICS
  • Appear as lactose fermenting colonies on differential enteric media
  • Non-motile
  • Large capsule – colonies appear large, moist and mucoid
klebsiella antigenic structure
KLEBSIELLAANTIGENIC STRUCTURE
  • Possess O and K antigens
  • K antigens are most useful in serologic typing
klebsiella determinants of pathogenicity
KLEBSIELLADETERMINANTS OF PATHOGENICITY
  • Capsule – resist phagocytosis

- encapsulated strains are more virulent

2. Endotoxin

3. Enterotoxin – isolated in patients with tropical sprue

- similar to E.coli ST and LT

- plasmid mediated

klebsiella clinical infection
KLEBSIELLACLINICAL INFECTION
  • Klebsiella pneumoniae

- cause primary community-acquired

pneumonia

- typical patient: middle or older aged with underlying medical problems – alcoholism, chronic bronchopulmonary disease, diabetes mellitus

- most patients – thick, non-putrid bloody sputum – necrosis and abscess formation

klebsiella clinical infection1
KLEBSIELLACLINICAL INFECTION
  • Klebsiella pneumonia

- can cause urinary tract infection

-wound infections, bacteremia, meningitis

2. Klebsiella oxytoca – causes chronic atrophic rhinitis – fetid odor

3. Klebsiella rhinoscleromatis – infects nose and pharynx; produces granulomatous inflammation

enterobacter1
ENTEROBACTER

Enterobacter cloaca

Enterobacter aerogenes

  • Non motile
  • Isolated less frequently than Klebsiella and E.coli

- Capable of infecting any tissue in the body

- Frequently associated with urinary tract infection

enterobacter2
ENTEROBACTER
  • Most infections occur in patients with underlying problems
  • Usually nosocomial
  • Among elderly
  • Risks for development of Enterobacter bacteremia

- long hospitalization, placement of intravenous catheters, respiratory colonization, use of antibiotics

enterobacter3
ENTEROBACTER

Enterobacter cloaca

Enterobacter aerogenes

enterobacter biochemical and cultural characteristics
ENTEROBACTERBIOCHEMICAL AND CULTURAL CHARACTERISTICS
  • Motile
  • Grows on media used for the isolation of enterics
  • Rapid lactose fermenters and produce pigmented colonies
enterobacter antigenic structure
ENTEROBACTERANTIGENIC STRUCTURE

- Antigenic subgrouping not as developed as E.coli and Klebsiella

enterobacter clinical infection
ENTEROBACTERCLINICAL INFECTION
  • Isolated less frequently than E. coli and Klebsiella
  • Capable of infecting any tissue
  • Most frequently associated with urinary tract infection
  • Most infections occur in patients with underlying problems – nosocomial
  • Risks: long term hospitalization, plac ement of intravenous catheters, respiratory colonization; prior use of antibiotics,
serratia1
SERRATIA

Serratia marcescens

Serratia liquifaciens

  • Can be differentiated from other members of the Enterobacteriaceae by:

- ability to produce extracellular deoxyribonuclease (Dnase),

lipase and gelatinase

- resistance to colistin and cephalosporin

serratia2
SERRATIA
  • O and A antigens are important epidemiologic markers
  • All Serratia infections – associated with underlying disease, changing physiologic patterns, immunosuppressive therapy or mechanical manipulations

- 90% are hospital acquired: UTI, wound infections, pneumonia, septicemia

proteus1
PROTEUS
  • Proteus mirabilis
  • Proteus vulgaris
proteus cultural characteristics
PROTEUSCULTURAL CHARACTERISTICS
  • Produce a translucent sheet of growth on non-selective media such as blood agar

- swarming

proteus biochemical characteristics
PROTEUSBIOCHEMICAL CHARACTERISTICS

- Distinguished from other enterics – produce phenylalanine deaminase

- All species produce urease:

urea = ammonia + CO2

  • Proteusmirabilis does not hydrolyze tryptophan to indole – basis of grouping into indole-positive and indole-negative
proteus antigenic structure
PROTEUSANTIGENIC STRUCTURE
  • All members possess O, H and K antigens
  • certain P. vulgaris strains share antigens with Rickettsia – used as -antigens for the detection of rickettsial antibodies in Weil_Felix test
  • ( OX-19, OX-K, OX-2)
proteus clinical infection
PROTEUSCLINICAL INFECTION

Proteus mirabilis

-2nd leading cause of community acquired UTI

- major cause of nosocomial infection

- urease formation causes urine to become alkaline – stone formation

- rapid motility – invasion of urinary tract

providencia1
PROVIDENCIA

Providencia rettgeri – previously Proteus

Providencia alcalifaciens

Providencia stuartii

  • Members of the normal intestinal flora
  • All cause urinary tract infections
  • Often resistant to antimicrobial therapy
citrobacter1
CITROBACTER

Citrobacter freundii – isolated from patients with diarrhea

Citrobacter diversus- neonatal meningitis and brain abscesses

shigella taxonomy
SHIGELLATAXONOMY

Shigella – genetically indistinguishable from

E.coli

- divided into 4 serogroups given species name

serogroup A – Shigella dysenteriae

serogroup B – Shigella flexneri

serogroup C – Shigella boydii

serogroup D – Shigella sonnei

shigella biochemical properties and cultural characteristics
SHIGELLABIOCHEMICAL PROPERTIES AND CULTURAL CHARACTERISTICS

Factors that distinguish from Salmonella

  • Appear as non-lactose fermenting colonies
  • Non-motile
  • Do not produce H2S
  • Do not produce gas from glucose (except S. flexneri)
shigella resistance to physical and chemical agents
SHIGELLARESISTANCE TO PHYSICAL AND CHEMICAL AGENTS
  • Less resistant than most enterics to physical and chemical agents
  • Susceptible to most common disinfectants
  • Can tolerate low temperatures if adequate moisture is present
  • Can survive for more than 6 months in water and room temperature
shigella antigenic structure
SHIGELLAANTIGENIC STRUCTURE

-Shigella are divided into 4 major O antigenic groups – A, B, C, D

subgrouping – based on minor O antigens

ex: 12 serologic types of group A

6 serologic types of group B

18 serologic types of group C

- No H antigens - nonmotile

shigella determinants of pathogenesis
SHIGELLADETERMINANTS OF PATHOGENESIS

1. Surface properties – due to O antigens

  • Survive the passage through upper GIT,

2. Invasiveness - attach to colonic cells and penetrate the epithelial cells by induced phagocytosis, escape from phagocytic vacuole, multiply and spread inside the cytoplasm and passage to adjacent cells.

shigella determinants of pathogenicity
SHIGELLADETERMINANTS OF PATHOGENICITY

3. Toxins

-Shiga toxin interferes with protein synthesis

- inactivates the 60S ribosomal unit

bacillary dysentery is a 2-stage disease

Shigella multiply in a noninvasive manner in the jejunum- and produce the toxin which is taken up by small bowel receptors- result in an activated secretory process

second phase – involve the large intestines

shigella toxins
SHIGELLATOXINS
  • Endotoxin

- from the LPS

- causes irritation of the bowel wall

2. Shigella dysenteriae exotoxin

- neurotoxic –meningisimus, coma

- enterotoxic – produces diarrhea

shigella pathogenesis
SHIGELLAPATHOGENESIS

Spectrum of disease

asymptomatic infection to severe bacillary dysentery with high fever, chills, convulsions, abdominal cramps, tenesmus and frequent bloody stools

Organisms rarely penetrate the intestinal wall and spread to other parts of the body

For children and elderly - dehydration