Bordetella Species
Overview of Bordetella
Bordetella species are small, Gram-negative rods, measuring approximately 0.2-0.5 × 0.5-1.0 μm.
Morphologically, they tend to appear coccobacillary.
These bacteria are strict aerobes and do not metabolize carbohydrates, relying instead on the oxidation of amino acids for energy.
Motility
B. avium and B. bronchiseptica are motile, possessing peritrichous flagella.
B. pertussis and B. parapertussis are non-motile.
All Bordetella species are catalase-positive and oxidase-positive.
B. bronchiseptica and B. avium can grow on MacConkey agar, which is significant for laboratory identification.
Change in Nomenclature
Previous Name: Alcaligenes faecalis (strains causing turkey coryza)
Present Name: Bordetella aviumBordetella species can promote infection and disease severity when combining with other pathogens, such as Pasteurella multocida, through mechanisms like establishing piliated and toxigenic strains.
Pathogenicity
B. avium: Infectivity linked to a plasmid; can inhibit cell-mediated immune responses; produces a histamine-sensitizing factor similar to B. pertussis toxin; involved in cytotoxin production, haemagglutinin, and dermonecrotising toxin.
B. bronchiseptica: Produces proteases, hemolysins, and hemagglutinins, which may contribute to its pathogenicity, leading to diseases like atrophic rhinitis and pneumonia, especially in young pigs under three weeks of age.
Natural Habitat
Bordetella species primarily inhabit the upper respiratory tracts of healthy and diseased humans and animals (including birds).
Pathogens:
B. pertussis: causes whooping cough in humans.
B. parapertussis: causes a milder form of whooping cough.
B. bronchiseptica: present in pigs, dogs, cats, rabbits, among others.
B. avium: colonizes the respiratory tracts of poultry, particularly turkeys.
Transmission can occur through aerosols or, in the case of turkeys, through contaminated water and litter.
Pathogenesis of Bordetella Infections
Adherence: B. bronchiseptica adheres to ciliated respiratory epithelium, leading to ciliary paralysis and inflammation.
Enzymes: Virulent strains produce pili and adenylate cyclase, aiding adherence and offering protection against phagocytosis, while harming respiratory clearance mechanisms.
The dermonecrotising toxin mainly causes nasal turbinate atrophy, crucial in young pigs.
The development of atrophic rhinitis is transient with B. bronchiseptica but may become chronic when other pathogens are involved.
Laboratory Diagnosis of Bordetella Infections
Specimens:
Nasal swabs, tracheal washings, and lungs of affected animals.
Special swabs for small-nosed animals such as piglets are needed.
Direct Microscopy:
Gram stains are not particularly useful; fluorescent antibody techniques are recommended.
Culture Media:
Routine media include sheep blood agar and MacConkey agar; selective media like Smith-Baskerville (SB) medium are essential for isolating Bordetella species from contaminated samples. The SB medium is especially adapted for B. bronchiseptica growth in pigs.
Identification of Colonies:
On blood agar, B. bronchiseptica produces small, convex, and smooth colonies that may be hemolytic after 24 hours.
On MacConkey agar, colonies appear small and pale, often with a pinkish hue.
Differentiation of Bordetella Species
Biochemical Reactions:
B. bronchiseptica is oxidase-positive, catalase-positive, citrate-positive, urease and nitrate-reducing.
B. avium has similar reactions but is urease-negative.
Haemagglutination Test for B. bronchiseptica:
It can agglutinate washed sheep erythrocytes; best done with younger cultures.
Moraxella Species
Overview of Moraxella
Morphology: Short, plump Gram-negative rods, measuring 1.0-1.5 × 1.5-2.5 μm; often occur in pairs, with some strains nearing a coccal shape.
Characteristics: Strict aerobes, non-motile, catalase-positive, oxidase-positive, and do not metabolize carbohydrates.
They can grow on non-enriched media but prefer blood or serum additives to enhance growth, with optimal temperatures around 33-35°C. M. phenylpyruvica grows on MacConkey agar, while M. bovis and M. lacunata do not.
Pathogenicity and Disease
M. bovis: Major pathogen causing infectious bovine keratoconjunctivitis; produces hemolysin, pili, and a cytotoxin damaging neutrophils, contributing to its virulence.
Environmental Factors: Injury from sunlight, dust, long vegetation, and insect bites increases risk, more common in summer and younger cattle.
In outbreaks: 60% of young animals affected compared to only 20% of older cattle.
Laboratory Diagnosis of Moraxella
Specimens: Lacrimal secretions from the inner canthus of the eye are collected. Samples should be rapidly inoculated onto blood agar.
Isolation: Blood agar and MacConkey plates should be inoculated quickly; due to their sensitivity to desiccation, care must be taken in handling.
Identification: On blood agar, M. bovis colonies appear small and greyish with a surrounding zone of complete hemolysis. Microscopic examination of colonial growth reveals rod-shaped or coccoid forms and should ideally avoid typical contamination from other bacteria.
Glucose-Non-Fermenting Gram-Negative Bacteria
Overview
This group includes important pathogens like Pseudomonas, Bordetella, and Moraxella, which do not ferment glucose but use it oxidatively or not at all.
Most can be isolated from clinical specimens and require specialized identification techniques.
Identification Techniques
Gram-stained smears for morphology, with the addition of biochemical and automated systems for detailed analysis; significant alpha and beta-hemolytic organisms are included in the evaluation.
Laboratory Diagnosis of Glucose-Non-Fermenting Bacteria
Specimens cultured under aerobic conditions at optimal temperatures, most typically at 37°C even when above their peak growth temperature.
Bacterial identification can be achieved through various modern techniques including automated systems and biochemical tests; pigment-producing species in the Pseudomonas and Flavobacterium genera are crucial for examination.
Miscellaneous Gram-Negative Bacterial Pathogens
Overview
This category encompasses various less frequently encountered pathogens important for animal or human health, including zoonotic infections.
Relevant Pathogens
Streptobacillus moniliformis: Associated with rat-bite fever in humans; identified through pleomorphic, fastidious, Gram-negative rods found in the Nasopharynx of rats.
Chromobacterium violaceum: Emerging pathogen associated with sporadic human infections, primarily found in tropical environments.
Noted for its violet pigment production under aerobic conditions, giving it significance in clinical settings.
Capnocytophaga species: Linked with infections from dog and cat bites, resulting in severe septicemia in predisposed individuals (immunocompromised patients).
Laboratory Diagnosis Techniques
Culture techniques involve inoculating specialized media conducive to specific growth needs and conducting biochemical reactions for identification.
Conclusion
These notes provide detailed insights into Bordetella, Moraxella, glucose-non-fermenting bacteria, and miscellaneous Gram-negative pathogens, highlighting their characteristics, pathogenicity, and laboratory diagnosis methodologies. Further exploration of the serology, virulence factors, and ecological impacts is suggested for comprehensive understanding in veterinary and medical microbiology settings.
Glucose-Non-Fermenting Gram-Negative Bacteria
Overview
This group includes important pathogens like Pseudomonas, Bordetella, and Moraxella, which do not ferment glucose but use it oxidatively or not at all. Most can be isolated from clinical specimens and require specialized identification techniques.
Identification Techniques
Gram-stained smears for morphology, with the addition of biochemical and automated systems for detailed analysis; significant alpha and beta-hemolytic organisms are included in the evaluation.
Laboratory Diagnosis of Glucose-Non-Fermenting Bacteria
Specimens cultured under aerobic conditions at optimal temperatures, most typically at 37°C even when above their peak growth temperature.
Bacterial identification can be achieved through various modern techniques including automated systems and biochemical tests; pigment-producing species in the Pseudomonas and Flavobacterium genera are crucial for examination.
Spirochaete
Overview
Spirochaetes are a group of spiral-shaped, Gram-negative bacteria, characterized by their unique corkscrew motility. They usually range from 0.1 to 3.0 μm in diameter and can be quite long, often several micrometers.
Pathogenicity
Key pathogens in this group include Treponema, Borrelia, and Leptospira, responsible for diseases such as syphilis, Lyme disease, and leptospirosis, respectively.
Laboratory Diagnosis
Diagnosis typically involves dark-field microscopy, serological tests, and specific culture conditions that may vary based on species.
Natural Habitat
These organisms typically reside in aquatic environments or as commensals in animal hosts. They can be found in soil, water, or as pathogens in their specific hosts, making them part of the broader ecosystem and important to animal and human health.
Treatment
Antibiotics, such as penicillin for Treponema, are effective against many spirochaete infections, while prevention through rodent control and sanitation is critical for zoonotic infections like leptospirosis.
Conclusion
Both spirochaetes and glucose-non-fermenting Gram-negative bacteria represent significant areas of study in microbiology due to their impact on health, necessitating ongoing research for effective diagnostics and treatments.
Glucose-Non-Fermenting Gram-Negative Bacteria
Overview
This group includes important pathogens like Pseudomonas, Bordetella, and Moraxella, which do not ferment glucose but use it oxidatively or not at all.
Identification Techniques
Gram-stained smears for morphology, with biochemical and automated systems for detailed analysis.
Laboratory Diagnosis
Cultured under aerobic conditions at optimal temperatures, typically at 37°C.
Spirochaete
Overview
Spiral-shaped, Gram-negative bacteria known for corkscrew motility, ranging from 0.1 to 3.0 μm in diameter.
Pathogenicity
Key pathogens include Treponema, Borrelia, and Leptospira, associated with diseases like syphilis and Lyme disease.
Laboratory Diagnosis
Involves dark-field microscopy and serological tests.
Natural Habitat
Found in aquatic environments or as commensals in animal hosts.
Treatment
Antibiotics such as penicillin for Treponema are effective; prevention is key for zoonotic infections.
Conclusion
Spirochaetes represent an important area of microbiological study due to their health impact.