Dr. Abdulaziz Alkhattaf
Non-spore forming, gram negative bacilli.
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
1. Lactose fermentation:
McConkey agar contains lactose and pH
indicator + pink colonies.
CLED agar changes from blue-green to
2. Biochemical tests:
(a)- Reduce nitrate to nitrite.
(b)- Ferment glucose with acid (sometimes gas
(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
4. Bacteriophage typing (using viruses to identify
5. Bacteriocine typing (pigments produced by
6. Plasmid analysis (extra-chromosomal DNA).
7. Polypeptide analysis (polyacrylamide gel
1. Virulence Factors:
i. Endotoxin: Lipopolysaccharide
Lipid A: toxin
ii. Capsule – antiphagocytic.
iii. Pili -for attachment ( K88 of
iv. Enterotoxins→ e.g E.coli causing diarrhoea.
i. Intestinal Salmonella } Primary
Shigella } intestinal
E.coli: some strains are
UTI –Coliforms contribute up to 80% UTI.
Wound infections/ post operative.
Respiratory tract infection.
Meningitis→neonates (E.coli) /or with trauma
i. Enterobacteria are resistant to multiple
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.
Cephalosporins (2nd,3rd generations)
Nitrofurantoin, Nalidixic acid/ UTI only.
Serology of E.coli:
According to the cell wall (O antigen) over 160
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
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)
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)
Enteroinvasive EIEC Invade colonic Dysentery;fever,
E.coli mucosa colitis,diarrhoea with
dysenteric-like blood, mucus, Leukocytes
Enterohaemorr EHEC Production of Bloody diarrhoea,WBCs,
hagic E.coli cytotoxin →Haemorrhagic.colitis
serotype &Haemolytic uraemic
0157;H7 syndrome (HUS)/Acute renal
Pathogenicity of E.coli
i. Urinary tract infection (UTI)/ causes
80% of UTI in pregnant females.
ii. Wound infection/ Surgery of lower
v. Neonatal meningitis.
KLEBSIELLA l ENTEROBACTER/ SERRATIA
Widely spread in the environment/ in the intestine
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
Β-lactamases producing/ resistant to ampicillin,1st
and 2nd generation of cephalosporins→ therefore we
resort to using Aminoglycosides.
1. Urinary tract infection (chronic, complicated
2. Wounds, skin lesions and respiratory infections in
4. Abscesses, endocarditis, chronic nasal and
5. Meningitis (neonates).
PROTEUS /MORGANELLA / PROVIDENCIA
Habitat: Human and animal intestine//soil/
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
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
Ear ,wound and burn infections (mixed infection).
Septicaemia and brain abcesses.
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
clinical isolates produce a characteristic green or
blue-green pigment called Pyocyanin. Also produce
Pyoverdin (fluorescein) a yellow-green
pigment↔fluoresces under UV light .
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
Severe external otitis (malignant otitis externa).
other skin lesions (folliculitis)↔ inadequate chlorinated
swimming pool users.
Corneal infections↔ contact lens users.
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.
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-
Airborne pseudomonas is hazardous to burned and ICU
Ear infection and irritating folliculitis (jacuzzi rash) occur due
to poorly maintained swimming pools or jacuzzis.
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
3. Using typing system to identify cross-infection of
one strain (epidemic strains).
Gram negative coccobacilli resemble
Enterobacteriaceae in growth pattern and
Incapable of fermenting carbohydrates or
Appear frequently as skin and respiratory
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
Gram negative coccobacilli in pairs.
Fastidious growth (required enriched media-
Due to similarity in morphology and positive
oxidase reaction Moraxella is some times
confused with Neisseria.
Causes otitis media, sinusitis and lower
Free living saprophyte that causes melioidosis,
a devastating tropical infection of animal and
humans that is endemic in eastern Asia and
Laboratory-acquired infection is a serious risk;
the species is included in hazard group 3
(together with plague).
Human infection is mainly acquired cutaneously
through skin abrasions or by inhalation of
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
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.
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.
Major opportunistic cause of respiratory infection in
patients with chronic granulomatous (cystic
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
Commensal of mucosal surface may cause
range of infections such as endocarditis,
meningitis, pneumonia and infections of
wounds and various soft tissues.
Meningitis with F.meningosepticum is
responsible for high mortality in epidemic
Is a saprophyte that could cause
opportunistic nosocomial infections in