Transcript lecture6 pseudo vibrio

Objectives
• By the end of this lecture the student must be:
 A) Identify the genus Pseudomonadaceae &
Vibrionaceae
• B) describe the chemical tests for this genus
• C) Differentiate between different sps.
• D) List and match the symptoms, diagnosis
and treatment for different sps.
Pseudomonas aeruginosa
Gram-negative bacilli belonging to Pseudomonadaceae
Motile by single polar flagellum, non spore
Non fastidious- Minimal nutritional requirements
Produces grape-like odor and blue-green pus and colonies
Two types of soluble pigments:
1. Pyoverdin : Yellow-green pigment & fluorescent
2. Pyocyanin: Blue-green pigment and non-fluorescent
 Strict aerobic, O+/F-, Oxidase and catalase positive
 Optimum temperature is 37 0C & able to grow at 42 0C
 Resistant to dyes, weak antiseptics and many antibiotics





2
Epidemiology







The most important pathogenic is Ps. aeruginosa
Opportunistic pathogen
Important agent in causing nosocomial infections
Ubiquitous in moist environment, hospital, in soil and water
Colonized in the intestine in10% of human
Represents 10-20% of hospital-acquired infections
Transiently colonize respiratory & GIT of hospitalized
patients:
1. Treated with broad-spectrum antibiotics
2. Exposed to respiratory therapy equipment
3. Hospitalized for long periods
3
Pathogenesis
1. Adhesins

Fimbriae, Pilli, Alginate (mucoid exo-polysaccharide)

Alginate slim forms biofilm that protect from antibodies, complement,
phagocytosis & antibiotic
2. Invasins
a. Proteases - Inactivate IFN and TNF
i. Elastase



Break down of elastin-containing tissues e.g. blood vessels, lung tissue, skin
Cleaves collagen, IgG, IgA and complement)
Produce hemorrhagic lesions associated with disseminated infection
ii.
Alkaline protease (lyses fibrin)
b.
Hemolysins
(phospholipase
&
lecithinase)
&
Leukocidin
4
3. Toxins
Pathogenesis
 Exotoxin A & S
 Inhibit protein synthesis (Like diphtheria toxin)
 Immunosuppressive
 Causes dermatonecrosis in burn wounds, corneal damage in
ocular infections, and tissue damage in chronic pulmonary
infections
 Pyocyanin – inhibits mitochondrial enzymes, impairs
ciliary function, mediates tissue damage
 LPS (endotoxin)
5
Clinical Finding
1. UTIs (Catheterized patients)
2. Wound, burn & other skin & soft tissues infections
 Echtyma Gangrenosum
3. Pneumonia (Cystic Fibrosis)
4. Eye infection- Contaminated contact lens clearing fluids
5. Chronic otitis media & otitis externa (swimming pool)
6. Meningitis- following lumbar puncture
7. Systemic infections- Septicemia in debilitated patients
8. Pseudomonal Endocarditis
6
Echtyma Gangrenosum
• Causative agent: Ps. aeruginosa
• Under risk: immunocompromised, burn patients, and
other critically ill patients
• Round or oval (1-15cm) severe invasive cutaneous
ulceritic single or multiple lesion with halo of erthryma
• Pseudomonas exotoxin: Tissue destruction
• Elastase degrades elastin in blood vessels wall
• Phospholipase C degrades phospholipids in cell
membranes
• Pyocyanin generates reactive oxygen species
7
Typing methods
1. Bacteriocin typing
 Three types of bacteriocins are produced-R,F,S
 Pyocin produced by test strain is employed to assess the
growth inhibition of 13 indicators strains
 Depending upon the growth inhibition of 13 indicators
strains,105 types are recognized
 Most popular method used
2. Phage typing
3. Serotyping-based on O & H,17 serotypes are recognized
8
Laboratory diagnosis
 Specimen
 Urine, pus, sputum, CSF, blood, skin swap
 Microscopical Examination
 Gram-negative rods and motile
 Cultural Characteristics
 On Nutrient agar:
 Colonies are surrounded by bluish green coloration
 On selective media "Cetermide"
 Pigments are more obvious
 On Blood agar: -hemolytic colonies
 On MacConkey agar
 Pale yellow colonies i.e. non lactose fermenters
 Ps. aeruginosa able to grow at 42 0C for 3 days
 Pyocin typing: Identification for epidemiological purpose
9
Vibrionaceae
•
•
•
•
•
•
•
•
General characteristics
Gram negative, curved, comma shaped bacilli
Motile by single polar flagella
Non spore, Non capsulated
Facultative anaerobes, Fermentative
Oxidase and catalase positive
Most vibrios have relatively simple growth factor
requirements and grow well in alkaline pH
Natural inhabitants : Aquatic environment
10
Vibrio cholerae
• >200 serogroups based on O-antigen
• V. cholerae O1 (classical and El Tor biotypes) and
O139 are primarily responsible for cholera outbreaks
– V. El Tor biotype causes cholera-like but milder
• Recently, V. cholerae O75 and O141 strains has
been associated with cholera-like diarrhea
• Some O1 strains do not produce cholera enterotoxin
(atypical or nontoxigenic O1 V. cholerae)
• Cholera is endemic in southern Asia (India, Pakistan
and Bangladesh), Latin America
11
Pathogenesis
• Mode of Transmission
– Consumption of contaminated water or food
• Incubation period:1-4 days
 High infectious dose: >108 CFU
 V. cholerae attach to mucosa of small intestine
 V. cholerae multiply & secrete enterotoxin (cholargen)
 Toxin binds to specific receptor on the intestinal
mucosal cell
 Toxin stimulates activity of cAMP, resulting in active
secretion of chloride & secondary loss of Na and H2O
 The patient loss 20 Litre fluids/day
 V. cholerae cause same disease as ETEC but more severe
12
Diagnosis of V. cholerae
 Specimen: Rice watery stool or rectal swab
 Culture on Alkaline Peptone Water (APW) then
subculture on selective differential medium
Thiosulfate Citrate Bile Salts Sucrose agar
 Selective due to alkalinity pH9 & contains bile salts
 Differential because contains sucrose
 Sucrose fermenting V. cholerae yellow colonies
 Sucrose non fermenting V. parahemolyticus appears
as blue to green colonies
 Sucrose fermentation is gold standard in identification
13
Diagnosis of V. cholerae
• Any sucrose fermenting colonies were subjected to Gram stain and oxidase test
• Gram stain
– Gram negative short rods, comma shaped, motile
• Biochemical reactions:
– Oxidase positive
– O+/F+
– Cholera red reaction
– TCBS agar (Figure) (Thiosulfate-citrate-bile salts-sucrose agar)
• Serology:
– Diagnosis confirmed & serotyping done by agglutination with specific antisera (O1,
O139)
14
V. parahaemolyticus
 It is the cause of acute gastroenteritis following
ingestion of contaminated sea-food such as raw fish
 Marine organism which live in high salt conc.
 So it requires 2% Na Cl in the isolation medium
◦ It is invasive affecting the colon
◦ V. cholerae is noninvasive, affecting the small
intestine through secretion of an enterotoxin
Allied Vibrios are large group of organisms; some are
saprophytic while others cause disease in animals
15