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ENTEROBACTERIACEAE

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					ENTEROBACTERIACEAE

   Dr. Abdulaziz Alkhattaf
                     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.
                Identification
1.   Lactose fermentation:
    McConkey agar contains lactose and pH
     indicator       + pink colonies.
    CLED agar changes from blue-green to
     yellow colonies.

2.  Biochemical tests:
(a)- Reduce nitrate to nitrite.
(b)- Ferment glucose with acid (sometimes gas
    production).
(c)- The use of API 20E biochemical kit tests.
Identification tools used in the lab
           Identification of coliforms
3.   Serological tests:

    Based on the somatic (O) antigen and the flagellar
     antigen (H) for the identification of Salmonella and
     Shigella species.

4.   Bacteriophage typing (using viruses to identify
     bacteria).

5.   Bacteriocine typing (pigments produced by
     bacteria).

6.   Plasmid analysis (extra-chromosomal DNA).

7.   Polypeptide analysis (polyacrylamide gel
Antigenic structure

                 Enterobacteria possess
                  variety of
                  heterogeneous
                  antigens:

                   Somatic/cell wall
                    (O)

                   Flagella (H)

                   Capsular (K)
                       Pathogenicity
1.          Virulence Factors:

     i.      Endotoxin:   Lipopolysaccharide

                          Lipid A: toxin

                          Polysaccharide: antigenic

     ii.     Capsule – antiphagocytic.

     iii.    Pili    -for attachment ( K88 of

                    E.coli→dirrhoea/infant pigs)
     iv.      Enterotoxins→ e.g E.coli causing diarrhoea.
                         Pathogenicity
2.    Diseases:
i.    Intestinal         Salmonella } Primary
                           Shigella } intestinal
      Pathogens.
                             E.coli: some strains are
      intestinal
                                           Pathogens.
ii.   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
                Antibiotic sensitivity
i.     Enterobacteria are resistant to multiple
       antibiotics.
ii.    In vitro sensitivity testing is required to
       monitor the trend and to assess based on
       case by case.
iii.   The most common antibiotic used are:
      Ampicillin/ amoxycillin and mezlocillin.
      Aminoglycosides.
      Trimethoprim.
      Chloramphenicol.
      Ciprofloxacin.
      Cephalosporins (2nd,3rd generations)
      Nitrofurantoin, Nalidixic acid/ UTI only.
                 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
                  Pathogenicity of E.coli
i.    Intestinal:
      Term        Abbrevia    Pathogenic                 Signs&
                    tion      Phenotype                 Symptoms
Enterotoxigenic               Secretion of:     Traveler’s diarrhoea
                    ETEC       heat-Labile        Watery, mild abdominal
      E.coli                      (LT)/           cramp ,(small intestine)
                               heat-stable
                                  (ST)/            dehydration,vomiting

Enteroaggregati                 Adhere to        Watery diarrhoea, vomit,
                  EaggEC       epith.cells        dehydration, abdominal
     ve E.coli                                             pain
Enteropathogen      EPEC        Adhere to       Infants (18-24month); low
                             epithelial cells     fever,malaise,vomiting,
    ic E.coli                (pilli)/effacing    diarrhoea→ (duodenum)
                                  lesions
 Enteroinvasive     EIEC     Invade colonic         Dysentery;fever,
      E.coli                     mucosa           colitis,diarrhoea with
                                ;Causing
                             dysenteric-like    blood, mucus, Leukocytes
                                diarrhoea
 Enterohaemorr      EHEC      Production of       Bloody diarrhoea,WBCs,
   hagic E.coli                 cytotoxin          →Haemorrhagic.colitis
                                 serotype          &Haemolytic uraemic
                                0157;H7         syndrome (HUS)/Acute renal
                                                          failure
                Pathogenicity of E.coli
2.        Extra-intestinal

     i.     Urinary tract infection (UTI)/ causes
            80% of UTI in pregnant females.
     ii.    Wound infection/ Surgery of lower
            intestinal tract.

     iii.   Peritonitis.

     iv.    Septicemia.

     v.     Neonatal meningitis.
     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).
   Β-lactamases producing/ resistant to ampicillin,1st
    and 2nd generation of cephalosporins→ therefore we

    resort to using Aminoglycosides.
                    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).
    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.
                   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.
                    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 .
                      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.
                         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 β-lactam compounds such as zlocillin,
    ticarcillin, imipenem and ceftazidime are commonly used.

   Aminoglycosides such as gentamicin and tobramycin are
    also used and some times with combination β-lactams.

   Fluoroquinolones (ciprofloxacin) can be given orally.
                        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.
                Pseudomonal control
    Prevention is easier than cure:

1.   Immunocompromised and patient with high risk of
     acquiring Ps. aeruginosa should not be admitted to
     a ward with cases of such infection are present.

2.   Therapeutic substances must be free from Ps
     especially multi-dose ointments, creams or eye
     drops.

3.   Using typing system to identify cross-infection of
     one strain (epidemic strains).
                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
   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.
                   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.
          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).
   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.
   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.
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.
               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
    cabapenem, meropenem.
              Eikenella corrodens


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

				
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posted:3/19/2013
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