ENTEROBACTERIACEAE

1
ENTEROBACTERIACEAE

• Dr. Abdulaziz Alkhattaf

2
coliforms

• Non-spore forming, gram negative bacilli.
• Facultative anaerobic.
• Catalase ve Oxidase ve.
• Motility some are capsulated.
• Widely dispersed in nature, yet was found to
  inhabit the intestine of mammalians.
• Grow well in ordinary media (blood agar,
  Mc-conkey agar) aerobically or facultative
  anaerobic.

3
Identification

• Lactose fermentation
• McConkey agar contains lactose and pH indicator
  pink colonies.
• CLED agar changes from blue-green to yellow
  colonies.
• Biochemical tests
• (a)- Reduce nitrate to nitrite.
• (b)- Ferment glucose with acid (sometimes gas
  production).
• (c)- The use of API 20E biochemical kit tests.

4
Identification tools used in the lab
5
Identification of coliforms

• Serological tests
• Based on the somatic (O) antigen and the
  flagellar antigen (H) for the identification of
  Salmonella and Shigella species.
• Bacteriophage typing (using viruses to identify
  bacteria).
• Bacteriocine typing (pigments produced by
  bacteria).
• Plasmid analysis (extra-chromosomal DNA).
• Polypeptide analysis (polyacrylamide gel
  electrophoresis).

6
Antigenic structure

• Enterobacteria possess variety of heterogeneous
  antigens
• Somatic/cell wall (O)
• Flagella (H)
• Capsular (K)

7
Pathogenicity

• Virulence Factors
• Endotoxin Lipopolysaccharide
• Lipid A toxin
• Polysaccharide
  antigenic
• Capsule antiphagocytic.
• Pili -for attachment ( K88 of
  
• E.coli?dirrhoea/infant pigs)
• Enterotoxins? e.g E.coli causing diarrhoea.

8
Pathogenicity

• Diseases
• Intestinal Salmonella Primary
• Shigella
  intestinal Pathogens.
• E.coli some
  strains are intestinal
  
• 
  Pathogens.
• Extra-intestinal
• UTI Coliforms contribute up to 80 UTI.
• Wound infections/ post operative.
• Respiratory tract infection.
• Septicaemia.
• Meningitis?neonates (E.coli) /or with trauma
  /surgery

9
Antibiotic sensitivity

• Enterobacteria are resistant to multiple
  antibiotics.
• In vitro sensitivity testing is required to
  monitor the trend and to assess based on case by
  case.
• The most common antibiotic used are
• Ampicillin/ amoxycillin and mezlocillin.
• Aminoglycosides.
• Trimethoprim.
• Chloramphenicol.
• Ciprofloxacin.
• Cephalosporins (2nd,3rd generations)
• Nitrofurantoin, Nalidixic acid/ UTI only.

10
Escherichia coli

• Serology of E.coli
• According to the cell wall (O antigen) over 160
  types recognized.
• According to the flagellar (H antigen) 55 types.
• Making over 8000 possible O-H seotypes.
• Some E.coli types are capsulated

11
Pathogenicity of E.coli

• Intestinal

Signs Symptoms Pathogenic Phenotype Abbreviation Term
Travelers diarrhoea Watery, mild abdominal cramp ,(small intestine) dehydration,vomiting Secretion of heat-Labile (LT)/ heat-stable (ST)/ ETEC Enterotoxigenic E.coli
Watery diarrhoea, vomit, dehydration, abdominal pain Adhere to epith.cells EaggEC Enteroaggregative E.coli
Infants (18-24month) low fever,malaise,vomiting, diarrhoea? (duodenum) Adhere to epithelial cells (pilli)/effacing lesions EPEC Enteropathogenic E.coli
Dysenteryfever, colitis,diarrhoea with blood, mucus, Leukocytes Invade colonic mucosa Causing dysenteric-like diarrhoea EIEC Enteroinvasive E.coli
Bloody diarrhoea,WBCs, ?Haemorrhagic.colitis Haemolytic uraemic syndrome (HUS)/Acute renal failure Production of cytotoxin serotype 0157H7 EHEC Enterohaemorrhagic E.coli
12
Pathogenicity of E.coli

• Extra-intestinal
• Urinary tract infection (UTI)/ causes 80 of UTI
  in pregnant females.
• Wound infection/ Surgery of lower intestinal
  tract.
• Peritonitis.
• Septicemia.
• Neonatal meningitis.

13
KLEBSIELLA l ENTEROBACTER/ SERRATIA

• Widely spread in the environment/ in the
  intestine flora of
• man and animals.
• Survive well in moist environments in hospitals.
• Opportunistic pathogens ? chances of infection
  are increased in long term hospitalization, ICU.
• Grow well on all media /producing large and
  mucoid colonies (capsule).
• ?-lactamases producing/ resistant to
  ampicillin,1st and 2nd generation of
  cephalosporins? therefore we resort to using
  Aminoglycosides.

14
Pathogenicity

1. Urinary tract infection (chronic, complicated
   infections).
2. Wounds, skin lesions and respiratory infections
   in hospitalised patients.
3. Septicemia.
4. Abscesses, endocarditis, chronic nasal and
   oropharyngeal sepsis.
5. Meningitis (neonates).

15
PROTEUS /MORGANELLA / PROVIDENCIA

• Habitat Human and animal intestine//soil/ water.
• Isolation Grow well on ordinary media in a
  swarming type, which cover the plate.
• Identification Swarming, and all species produce
  a potent urease enzyme.
• phage, bacteriocine and serotyping schemes have
  been developed for identification there species.

16
Pathogenesis

• Urinary tract infection / urea is split by the
  Proteus urease to produce ammonia?alkaline
  urinary pH.
• Urease-producing organisms (proteus) may provoke
  the formation of calculi (stones) in urinary
  tract.
• Ear ,wound and burn infections (mixed infection).
• Septicaemia and brain abcesses.

17
PSEUDOMONAS

• Gram Negative Bacilli non-fermentative strictly
  aerobic, motile and oxidase positive.
• Pseudomonas species commonly inhibit soil, water
  and are widely spread. Can use variety of carbon
  and nitrogen sources.
• Difficult to eradicate / especially in hospital
  wards, operating theatres and medical equipments
  (respiratory ventilators) being resistant to many
  disinfectants.
• clinical isolates produce a characteristic green
  or blue-green pigment called Pyocyanin. Also
  produce Pyoverdin (fluorescein) a yellow-green
  pigment?fluoresces under UV light .

18
(No Transcript)
19
Pathogenesis

• Ps.aeruginosa is an important opportunistic
  pathogen.
• causing infection in immunocompromised patients /
  burns, HIV,cancer and cystic fibrosis patients.
• pseudomonas enters blood stream causing sepsis
  with 50 mortality rate.
• spread to skin causing black necrotic lesions
  (ecthyma gangrenosum).
• Severe external otitis (malignant otitis
  externa).
• other skin lesions (folliculitis)? inadequate
  chlorinated swimming pool users.
• Corneal infections? contact lens users.

20
Treatment

• Psedomonas is resistant to many antibiotics /e.g
  penicillin, ampicillin, tetracycline, most
  cephalosporins.
• Psedomonas infections were usually treated with
  polymyxins, now stopped for its high toxicity.
• Antipseudomonal ß-lactam compounds such as
  Azlocillin, ticarcillin, imipenem and ceftazidime
  are commonly used.
• Aminoglycosides such as gentamicin and tobramycin
  are also used and some times with combination
  ß-lactams.
• Fluoroquinolones (ciprofloxacin) can be given
  orally.

21
Epidemiology

• Species have the ability to multiply on moist
  equipments (humidifiers) in hospital wards,
  bathrooms kitchens.
• Resistant to many disinfectants and antiseptics.
• Can contaminate pharmaceutical preparations and
  may cause ophthalmitis to contact lenses users.
• Important cause of nosocomial infections 10-30
  of hospital-acquired infections.
• Airborne pseudomonas is hazardous to burned and
  ICU patients.
• Ear infection and irritating folliculitis
  (jacuzzi rash) occur due to poorly maintained
  swimming pools or jacuzzis.

22
Pseudomonal control

• Prevention is easier than cure
• Immunocompromised and patient with high risk of
  acquiring Ps. aeruginosa should not be admitted
  to a ward with cases of such infection are
  present.
• Therapeutic substances must be free from Ps
  especially multi-dose ointments, creams or eye
  drops.
• Using typing system to identify cross-infection
  of one strain (epidemic strains).

23
Acinetobacter

• Gram negative coccobacilli resemble
  Enterobacteriaceae in growth pattern and colonial
  morphology.
• Incapable of fermenting carbohydrates or reduce
  nitrates.
• Appear frequently as skin and respiratory
  colonizers.
• Frequently contaminate wet objects including
  soaps and disinfectant solutions.
• Pneumonia, urinary tract and soft tissue are the
  most common infections

24

• Nosocomial respiratory infections are traced to
  contaminated inhalation therapy equipments
  whereas bacteremia to infected intravenous
  catheters.
• Due to frequent resistance to penicillins,
  cephalosprins and some aminoglycosides treatment
  is difficult and required prior sensitivity
  testing.
•  

25
Moraxella

• Gram negative coccobacilli in pairs.
• Fastidious growth (required enriched
  media-chocolate agar).
• Due to similarity in morphology and positive
  oxidase reaction Moraxella is some times confused
  with Neisseria.
• Causes otitis media, sinusitis and lower
  respiratory infection.

26
Burkholderia pseudomallei

• Free living saprophyte that causes melioidosis, a
  devastating tropical infection of animal and
  humans that is endemic in eastern Asia and north
  Australia.
• Laboratory-acquired infection is a serious risk
  the species is included in hazard group 3
  (together with plague).

27

• Melioidosis
• Human infection is mainly acquired cutaneously
  through skin abrasions or by inhalation of
  contaminated particles.
• Clinical manifestation range from a sub-clinical
  infection, diagnosed by the presence of specific
  antibodies, to a benign pulmonary infection that
  may resemble tuberculosis or septicemia with
  mortality rate of 80-90.
• In north eastern Thailand, B.pseudomallie is
  responsible for 20 of all community acquired
  septicemia.

28

• Early diagnosis and appropriate antibiotic
  therapy are key factors in the successful
  management of melioidosis.
• Organism may be isolated from sputum, urine, pus
  or blood (gram ve bacilli).
• ELISA is used for detection of IgG anf IgM
  antibodiy to B.pseudomallie as well as indirect
  haemagglutination test.

29
Treatment

• Combination of tetracycline and chloramphenicol
  for long period of time, have been widely used.
• The ability of B.pseudomallie to survive and
  multiply in phagocytic macrophages may explain
  the difficulty to treat the disease.
• Antibiotics that are effective against the
  organism in vitro are not successful in vivo
  unless with prolong period of treatment.
• Ceftazidime is both effective in vitro and in
  vivo.

30
Burkholderia cepacia

• Major opportunistic cause of respiratory
  infection in patients with chronic granulomatous
  (cystic fibrosis) disease.
• The organism is multi-resistance to many
  antibiotics and transport by social contact.
• Cepacia syndrome, an acute fatal necrotizing
  pneumonia, some times accompanied by bacteraemia
  is a risk with B.cepacia.
• For treatment of B.cepacia ceftazidime or
  carbapenem, meropenem.

31
Eikenella corrodens

• Commensal of mucosal surface may cause range of
  infections such as endocarditis, meningitis,
  pneumonia and infections of wounds and various
  soft tissues.

32
Flavobacterium meningosepticum

• Meningitis with F.meningosepticum is responsible
  for high mortality in epidemic outbreaks.
• Is a saprophyte that could cause opportunistic
  nosocomial infections in infants.
•