Vibrios, Pseudomonas, Campylobacter, Helicobacter

Other gram-negative bacilli

VIBRIOS

• Among the most common bacteria in surface waters worldwide

• Curved, aerobic rods; motile with polar flagella

• oxidase (+)

• grow best on alkaline media

• Often found in brackish water

Vibrio cholerae

• Classified based on somatic O antigen:1. V. cholerae O1 – most common cause of

epidemic & pandemic cholera2. V. cholerae O139 (Bengal strain) –

epidemic3. Non-O1 group

• Two biotypes (based on differences in biochemical reactions):1. El Tor – most common cause of

epidemics and cause of 7th pandemic2. Cholerae or classical

• Three serotypes (based on antigenic differences):Ogawa, Inaba, Hikojima

Vibrio cholerae

• MOT: fecal-oral

• Sources of infection: humans, marine shellfish (shrimp and oysters)

• Sensitive to gastric acid high infective dose

• Virulence factors:1. Mucinase – cause adherence to

cells of the brush border of the gut2. Choleragen – stimulate adenylyl

cyclase

Vibrio cholerae

Vibrio choleraeCholera

ToxinB subunit A subunit

Binds GM1 ganglioside (surface of

epithelial cells)

Carried to ER (retrograde transport)

Endocytosis

Reduced by protein disulfide isomerase

in ER

Cytosol

Unfolding

Refolding

Interact with cytosolic ADP

ribosylation factors

Activate G protein

Stimulate adenylate

cyclase

Inc. cAMP

Open CFTR

Cl released in lumen; secretion of HCO3 , Na+ &

water

Vibrio cholerae

• Clinical findings:

Voluminous watery diarrhea – hallmark; “rice water” stool

Loss of fluid and electrolytes – marked dehydration “washerwoman” hands Cardiac and renal failure Hypovolemic shock

Vibrio cholerae

• Diagnosis: Culture on MacConkey’s agar (slow

lactose fermenter) or TCBS (Thiosulfate citrate bile salt sucrose) agar plate for selective isolation

Oxidase (+) – distinguished from the family Enterobacteriaceae

Serology

• Treatment: Prompt and rapid fluid and

electrolyte replacement Tetracycline – shorten duration

Growth on TCBS agar plate

Vibrio parahaemolyticus

• Halophilic – grows on 8% NaCl solution

• MOT: ingestion of raw or undercooked seafood, especially shellfish such as oysters

• Mild to severe watery diarrhea, nausea and vomiting, abdominal cramps, fever self-limited

• No specific treatment indicated

Vibrio vulnificus

• Found in warm salt waters

• Causes severe skin and soft tissue infections (cellulitis), especially in shellfish handlers

• Rapid, fatal septicemia in immunocompromised people who have eaten raw shellfish

• Treatment: doxycycline

Pseudomonas aeruginosa

• Gram-negative rods that resemble the Enterobacteriaceae but are strict aerobes

• Derive energy by oxidation of sugars rather than fermentation

• Oxidase (+)

• Able to grow in water containing only traces of nutrients

Pseudomonas aeruginosa

• Produce two pigments: Pyocyanin (blue) Pyoverdin (fluorescein) – yellow

green pigments that fluoresce under UVL

• Found chiefly in soil and water

• Found on the skin in moist areas

• Primarily opportunistic

Pseudomonas aeruginosa

• Virulence factors:

1. Endotoxins – cause sepsis and shock

2. Exotoxin A – cause tissue necrosis; inhibits eukaryotic protein synthesis similar to diphtheria exotoxin

3. Enzymes Elastases and proteases

4. Pyocyanin – damages the cilia and mucosal cells of respiratory tract

Pseudomonas aeruginosa

• Clinical:

1. Urinary tract infections2. Pneumonia in cystic fibrosis patients3. Burn wound infection4. Sepsis5. Ecthyma gangrenosum – black

necrotic lesions on skin6. Malignant external otitis7. Folliculitis 8. Osteochondritis of the foot due to

punctured wounds through the soles of gym shoes - most common cause

Ecthyma gangrenosum

Osteochondritis of foot

Pseudomonas aeruginosa

• Diagnosis:

1. Culture – non-lactose fermenting2. Oxidase production3. Biochemical reactions – confirmatory

• Treatment: Resistant to many antibiotics Ticarcillin or piperacillin +

aminoglycoside (gentamicin or amikacin)

Production of pyocyanin, water-soluble green pigment of Pseudomonas

aeruginosa. (left tube)

Campylobacter jejuni

• Comma- or S-shaped rods

• Microaerophilic (5% oxygen)

• Grows well at 420C

• Sources of infection: domestic animals

• MOT: fecal-oral (poultry, meat, unpasteurized milk common sources)

Campylobacter jejuni

• Clinical:

Enterocolitis – begins as watery, foul-smelling diarrhea bloody stools

Associated with 1. Guillain-Barre syndrome

Most common cause of acute neuro-muscular paralysis

Autoimmune disease2. Reactive arthritis3. Reiter’s syndrome

Campylobacter jejuni

• Diagnosis:

Culture Oxidase (+); sensitive to

nalidixic acid

• Treatment: erythromycin or ciprofloxacin

Helicobacter pylori

• Curved; gram-negative; similar in appearance to Campylobacter

• Strongly urease positive convert urea to ammonia neutralize gastric acid

• Rapidly motile – allow organism to penetrate protective mucus layer

Helicobacter pylori

• Most common cause of chronic gastritis

• Most common cause of duodenal ulcers

• Second most common cause of gastric ulcer

• Associated with development of gastric CA and gastric lymphoma

Helicobacter pylori

• Diagnosis:

Culture Urease production urea

breath test

Helicobacter pylori

Treatment:

Proton pump inhibitors (Omeprazole)

Antibiotics – amoxicillin, metronidazole, tetracycline

Bismuth salts

HAEMOPHILUS

• Family Pasteurellaceae

• Small, gram negative, pleomorphic

• Require enriched media containing blood or its derivatives

• Facultative anaerobes

• Obligate parasites

Haemophilus influenzae (Pfeiffer’s Bacilli)

• Found on mucus membrane of URT in humans (non-capsular form) encapsulated species uncommon members of normal flora

• Short, coccoid bacilli in pairs or chains

Haemophilus influenzae

Classification:

1.Serotype – based on capsular antigen

2.Biotype – based on biochemical properties

a. indole production

b. urease activity

c. ornithine decarboxylase activity

3.Biogroup – useful for clinical purposes

Haemophilus influenzae: Culture

• Chocolate agar – flat, grayish brown colonies after 24 hrs incubation

• Does not grow on sheep blood agar except around colonies of Staphylococci “satellite phenomenon”

Haemophilus influenzae

Growth Characteristics:

• Requires X factor (hemin) and V factor (NAD)

• Ferments carbohydrates poorly and irregularly

Haemophilus influenzaeCharacteristics & Growth

Requirements:Species X

FactorV

FactorHemolysis

H. influenzae

H. parainfluenzae

H. ducreyi

H. haemolyticus

H. parahaemolyticus

H. aprophilus

+

-

+

+

-

-

+

+

-

+

+

-

-

-

-

+

+

-

Haemophilus influenzae: Virulence Factors

Capsule

• Antiphagocytic; impair ciliary function

• Main virulence factor

• With capsular polysaccharides (a to f)

Type b – polyribose-ribitol phosphate (PRP)

Somatic antigen

• Outer membrane proteins lipooligo-saccharides (endotoxin)

IgA1 proteases

Haemophilus influenzae: Virulence Factors

Haemophilus influenzae: Clinical Features

H. influenzae type b

• Most common serotype causing systemic disease

1.Meningitis2.Pneumonia & empyema3.Epiglottitis4.Cellulitis5.Septic arthritis

Non-typable (non-encapsulated) H. influenzae

• opportunistic

1.Chronic bronchitis

2.Otitis media

3.Sinusitis

4.Conjunctivitis

Haemophilus influenzae: Clinical Features

Meningitis

• 20 to bacteremic spread from nasopharynx

• Peak incidence: 3 – 18 mos. old

Epiglottitis

• Cellulitis & swelling of supraglottic tissues

• Pharyngitis, fever & dyspnea complete airway obstruction death

Cellulitis

• Reddish blue patches on cheeks or periorbital areas

Arthritis• Infection of a single large joint• Children < 2 y/o or

immunocompromised patients or those with previously damaged joints

Conjunctivitis• Epidemic and endemic• H. influenzae biogroup

aegypticus

Haemophilus influenzae

Clinical Features:Sepsis with gangrene

Haemophilus influenzae: Prevention

1.Chemoprophylaxis with Rifampicin for non-immune children < 4 y/o who are close contacts

2.Hib conjugate vaccine

• > 2 mos. old Hib conjugated with C. diphtheriae toxin protein or N. meningitidis outer membrane complex

• > 15 mos. old Hib conjugated with diphtheria toxoid

Haemophilus aegypticus

• H. influenzae biotype III

• Koch-Weeks bacillus

• Resembles H. influenzae closely

• Diseases:1.Conjunctivitis – highly

communicable2.Brazilian purpuric fever – fever,

purpura, shock and death

Haemophilus ducreyi

• Causes chancroid (soft chancre)

• Ragged ulcer on genitalia with marked swelling and tenderness

• Lymph nodes enlarged and painful

• Organism grows best on chocolate agar incubated in 10% CO2

• No permanent immunity

Haemophilus ducreyi

Bordetella pertussis

• Small, coccobacillary, encapsulated, gram (-)

• With bipolar metachromatic granules (toluidine blue stain)

• Non-motile; strict aerobe

• Forms acid from glucose and lactose

Bordetella pertussis

• Requires enriched mediaBordet-Gengou medium

(potato-blood-glycerol agar)Contains Pen G 0.5 ug/mL

• Virulence genes – bvgA and bvgS

Bordetella pertussis

Gram stain

Culture on chocolate agar

Bordetella pertussis: Virulence Factors

a)Filamentous hemagglutinin• Protein on pili; adhesion to ciliated

epithelial cells

b)Pertussis toxina)promote lymphocytosis via

inhibition of signal transduction by chemokine receptors lymphocytes do not enter lymphoid tissues

b)promote sensitization to histaminec)enhance insulin secretiond)stimulate adenylate cyclase via

ADP-ribosylation

3.Adenylyl cyclase toxin – inhibit phagocytosis

4.Tracheal cytotoxin• Fragment of bacterial

peptidoglycan• Induce nitric oxide destroy

ciliated epithelium

5.Dermonecrotic toxin

6.Hemolysin

Bordetella pertussis: Virulence Factors

• Adheres to and multiplies rapidly on epithelial surface of trachea and bronchi interfere with ciliary action

• No invasion of blood

Bordetella pertussis: Pathogenesis

• MOT: airborne droplets

• Source of infection: patients in early catarrhal stage

• Disease: Pertussis or Whooping Cough acute tracheobronchitis

• Incubation period: approx. 2 weeks

Bordetella pertussis: Pathogenesis

Clinical: Stages of Disease

1.Catarrhal• Mild coughing and sneezing• Highly infectious but not very ill

2.Paroxysmal (1-4 weeks)• Series of hacking coughs,

accompanied by copious amts. of mucus, ending with inspiratory “whoop” exhaustion, vomiting, cyanosis and convulsions

• High wbc count (16,000-30,000/uL) with absolute lymphocytosis

3.Convalescence - slow

Specimen: saline nasal wash (preferred) or nasopharyngeal swab

1.Direct fluorescence antibody test – 50% sensitivity

2.Culture of saline nasal wash fluid

3.PCR – most sensitive4.Serology – (+) only on third

week of illness of little diagnostic value

Bordetella pertussis: Diagnosis

• First defense is antibody that prevents attachment

• Recovery from disease or immunization is followed by immunity

• Second infection may occur but is mild

• Re-infection occurring years later in adults may be severe

• Vaccine-induced immunity not completely protective

1.Chemoprophylaxis – Erythromycin for exposed, unimmunized individuals OR exposed, immunized children < 4 years old

2.Vaccine – two vaccines available:a) acellular vaccine – contains 5

purified antigens main immunogen is inactivated pertussis toxin; first vaccine to contain a genetically inactivated toxoid ADP-ribosylating activity removed

b) DPT x 3 doses

BRUCELLA

• Zoonotic obligate parasite of animals & humans

• Intracellular organism

• Gram negative coccobacilli

• Aerobic; non-motile; non-spore-forming

BRUCELLA

• Catalase (+); oxidase (+)

• Produces H2S

• Culture: trypticase soy agar OR blood culture media; B. abortus requires 5-10% CO2 for growth

• Route of infection in humans:1.Intestinal tract – ingestion of

infected milk & contaminated dairy products (cheese from unpasteurized goat’s milk)

2.Mucous membranes – droplets3.Skin – contact with infected

tissues of animals

• Pathogenesis: endotoxin – O antigen polysaccharide

Species Animal Pathology

B. melitensis

Goats Acute and severe infection

B. suis Swine Chronic with suppurative lesions; caseating granulomas

B. abortus Cattle Mild disease without suppuration;Non-caseating granulomas of the RES (LN, liver, spleen, BM)

B. canis Dogs Mild disease

Clinical: Brucellosis (Undulant or Malta Fever)

1.Acute• Malaise, fever, weakness, aches &

sweats• Fever rises in the afternoon fall

during the night with drenching sweats

• (+) lymphadenopathy w/ palpable spleen; + hepatitis with jaundice

2.Chronic• With psychoneurotic symptoms• Weakness, aches & pains, low

grade fever

Diagnosis:

1.Culture• BM & blood – commonly used

specimen• Brucella agar, trypticase soy

medium, brain heart infusion medium, chocolate agar

2.Serology – inc. IgM during 1st week of illness; peak at 3 months