PARVO BACTERIA

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Dan Freeman

(PARVO) BACTERIA

• These are a group of SMALL, Gram negative coccoid bacilli which require blood or blood products for growth.

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• Include the genera:

 Haemophilus

 Bordetella

 Brucella

 Pasteurella

 Francisella

 Actinobacillus

 Gardnerella

Haemophilus species

• Haemophilus influenzae type b is an important human pathogen; while Haemophilus ducreyi causes the STI chancroid.

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• They are gram negative coccobacilli, showing pleomorphism - different shapes in clinical specimens e.g. CSF

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Habitat:

• Haemophilus influenzae are usually found in upper respiratory tract of man.

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Culture:

• All species need blood or blood products for growth
• Haemophilus influenzae can grow on Chocolate agar or Blood agar.

Haemophilus Influenzae �

Exhibits Satellite Phenomenon near colonies of Staphyloccocus aureus on Blood agar.

Large colonies of

H. influenzae grow near Staph aureus colonies

Colonies of Staph aureus

produce V factor

Small colonies of H. influenzae away from colonies of Staph. aureus

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Blood Agar Provides X Factor

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Diseases Caused by Haemophilus species

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Species Disease

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H. influenzae capsulated Meningitis, arthritis, osteomyelitis,

(mainly type a, b) cellulitis, epiglottitis, bacteraemia

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H. influenzae non- Exacerbations of chronic bronchitis,

capsulated sinusitis, otitis media, others.

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H. aegyptius Conjunctivitis

H. ducreyi Chancroid (Sexually Transmitted)

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H. parainfluenzae Commensals of the upper respiratory tract;

H. haemolytic can cause disease in immunocompromised

H. parahaemolyticus patients

Laboratory Diagnosis

Specimens depend on the type of diseases

• CSF – in meningitis
• Blood – in meningitis and bacteraemia and all types of invasive disease.
• Sputum – in pneumonia
• Swab – in cellulitis
• Synovial fluid – in arthritis

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• Direct smear shows pus cell + pleomorphic gram –ve coccobacilli
• CSF Culture, on chocolate agar
• CSF detection for presence of antigens by agglutination

Epidemiology of Invasive �H. influenzae Infection

• More common in winter after episodes of viral infections.
• More common in crowded families with poor status.
• Family members can infect each other.
• Mortality about 5%
• In meningitis, neurological lesions - 10-15 %
• Conjugate vaccine (Hib) reduces the morbidity and mortality.

Treatment

• Ampicillin (Amoxycillin) if not β lactamase producer

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• Chloramphenicol

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• Ceftriaxone, Cefuroxime

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• Chemoprophylaxis: Contacts of patient with H. influenzae type b infection can be given Rifampicin for 4 days as prophylaxis.

Bordetella pertussis and �Bordetella parapertussis

B. pertussis – causes Whooping Cough

B. parapertussis – causes a milder form of whooping cough.

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• Live mainly in the human respiratory tract.
• Morphology: short, gram - negative coccobacilli.
• Pathogenicity – Humans are the only natural hosts. Causes whooping cough due to production of endotoxin which affect the respiratory mucosa.

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Clinical Features

• Affect pre-school children, severe in under 1 year olds. Presents as an acute tracheobronchitis

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Divided into 3 Stages

• Catarrhal stage 2/52: Fever, rhinorrhoea, sneezing, anorexia, malaise.
• Paroxysmal cough 2/52: Violent cough followed by inspiratory whoop, vomiting, convulsions
• Convalescent stage 4/52: Lymphocytosis which can mimic lymphocytic leukaemia.

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Diagnosis

• Clinical

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• Per-nasal swab

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• Cough plate

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• Swab by Immunofluorescence - Rapid Method

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• Media: enriched blood agar - Bordet-Gengou medium (potato-blood-glycerol agar) with added antibiotics.

Treatment��Erythromycin which is effective in early stage disease.��Vaccination��1. Whole killed bacterium vaccine given IM as part of the triple vaccine DPT (DIPTHERIA, PERTUSSIS, TETANUS). It is safe, but some cases of CNS involvement have been reported.��2. A cellular vaccine formed from Pertussis toxin��

Brucella

• The brucellae are obligate parasites of animals and humans and are characteristically located intracellularly.

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• Brucella melitensis typically infects goats; Brucella suis - swine; Brucella abortus - cattle; and Brucella canis - dogs.

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• Human disease is brucellosis (undulant fever, Malta fever). It is characterized by an acute bacteraemic phase followed by a chronic stage that may extend over many years and may involve many tissues and organs.

Brucella - contd

• Common routes of infection are the intestinal tract (ingestion of infected milk), mucous membranes (droplets), and skin (contact with infected tissues of animals).

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• Incubation period ranges from 1–4 weeks. Onset is insidious, with malaise, fever, weakness, aches, and sweats.

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• Brucellae may be susceptible to tetracyclines, rifampin, trimethoprim–sulfamethoxazole, aminoglycosides, and some quinolones.

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• Control rests on limitation of spread and possible eradication of animal infection, pasteurization of milk and milk products.

Pasteurella

• Pasteurella species are primarily animal pathogens, but they can produce a range of human diseases.

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• Pasteurellae are non-motile gram-negative coccobacilli with a bipolar appearance on stained smears.

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• Pasteurella multocida – the most important specie - occurs worldwide in the respiratory and gastrointestinal tracts of many domestic and wild animals.

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• It is perhaps the most common organism in human wounds inflicted by bites from cats and dogs.

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• Clinical Findings: The most common presentation is a history of animal bite followed within hours by an acute onset of redness, swelling, and pain.

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• Penicillin G is considered the drug of choice. Tetracyclines and fluoroquinolones are alternative drugs.

Francisella tularensis

• An obligate aerobe, pleomorphic, G-ve rods. Encapsulated in vivo.

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• It causes Tulaeramia; essentially a disease of rodents.

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• Man gets infected by direct contact with the animal or indirectly through blood sucking insects.

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• It grows only on Francis medium.

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• Antibiosis is carried out with streptomycin or gentamicin.

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