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Questions and Answers
Which factor attributed to the virulence of Haemophilus influenzae is responsible for its antiphagocytic properties?
Which factor attributed to the virulence of Haemophilus influenzae is responsible for its antiphagocytic properties?
What is the primary reservoir for Haemophilus influenzae infections?
What is the primary reservoir for Haemophilus influenzae infections?
Which of the following species is included in the genus Bordetella?
Which of the following species is included in the genus Bordetella?
What type of growth medium is specifically required for culturing Haemophilus influenzae?
What type of growth medium is specifically required for culturing Haemophilus influenzae?
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Which clinical condition is commonly associated with the spread of Haemophilus influenzae?
Which clinical condition is commonly associated with the spread of Haemophilus influenzae?
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What factor primarily facilitates the attachment of Haemophilus influenzae to the respiratory epithelial cells?
What factor primarily facilitates the attachment of Haemophilus influenzae to the respiratory epithelial cells?
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Which of the following describes the shape and gram characterization of Haemophilus influenzae?
Which of the following describes the shape and gram characterization of Haemophilus influenzae?
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Which virulence factor of Haemophilus influenzae is involved in causing fever and inflammation?
Which virulence factor of Haemophilus influenzae is involved in causing fever and inflammation?
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What is the main route of transmission for Haemophilus influenzae?
What is the main route of transmission for Haemophilus influenzae?
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Which subtype of Haemophilus influenzae is most notorious for infecting children and immunocompromised individuals?
Which subtype of Haemophilus influenzae is most notorious for infecting children and immunocompromised individuals?
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What is the primary source of transmission of Brucella to humans?
What is the primary source of transmission of Brucella to humans?
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Which of the following conditions is NOT associated with unencapsulated strains of Haemophilus influenzae?
Which of the following conditions is NOT associated with unencapsulated strains of Haemophilus influenzae?
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Which of the following is NOT a characteristic of brucellosis?
Which of the following is NOT a characteristic of brucellosis?
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What is the most common serological test used for diagnosing brucellosis?
What is the most common serological test used for diagnosing brucellosis?
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What type of pathogen is Brucella, and what is its primary mode of transmission?
What type of pathogen is Brucella, and what is its primary mode of transmission?
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Which of the following is true regarding Bordetella pertussis culture?
Which of the following is true regarding Bordetella pertussis culture?
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How often should blood cultures be carried out when diagnosing brucellosis in its acute phase?
How often should blood cultures be carried out when diagnosing brucellosis in its acute phase?
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Which drug combination is considered the treatment of choice for brucellosis?
Which drug combination is considered the treatment of choice for brucellosis?
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Haemophilus influenzae type b septicemia can lead to which of the following severe complications?
Haemophilus influenzae type b septicemia can lead to which of the following severe complications?
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Which clinical manifestation is most characteristic of human brucellosis?
Which clinical manifestation is most characteristic of human brucellosis?
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What percentage of blood cultures are positive in the early weeks of brucellosis infection?
What percentage of blood cultures are positive in the early weeks of brucellosis infection?
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Which method is used to demonstrate the presence of Brucella organisms in clinical specimens?
Which method is used to demonstrate the presence of Brucella organisms in clinical specimens?
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What is the typical morphology of Brucella species?
What is the typical morphology of Brucella species?
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Which population is primarily affected by whooping cough caused by Bordetella pertussis?
Which population is primarily affected by whooping cough caused by Bordetella pertussis?
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Which population is least likely to be affected by brucellosis due to occupational exposure?
Which population is least likely to be affected by brucellosis due to occupational exposure?
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What distinguishes Brucella colonies during culture from standard laboratory bacteria?
What distinguishes Brucella colonies during culture from standard laboratory bacteria?
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What is a rare mode of transmission for Brucella infection?
What is a rare mode of transmission for Brucella infection?
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What is an effective prophylactic treatment for Bordetella pertussis exposure?
What is an effective prophylactic treatment for Bordetella pertussis exposure?
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What is the significant titer value in the Rose Bengal Test for diagnosing brucellosis?
What is the significant titer value in the Rose Bengal Test for diagnosing brucellosis?
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Which of the following infections is associated with encapsulated strains of Haemophilus influenzae?
Which of the following infections is associated with encapsulated strains of Haemophilus influenzae?
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Study Notes
Gram-Negative Coccobacilli
- Gram-negative coccobacilli include Haemophilus, Bordetella, and Brucella.
- They share similar bacterial shape and Gram stain.
- However, they differ in the diseases they cause, populations they affect, virulence factors, pathogenesis, and ability to infect animals and humans.
- There are different species present within each genus.
- Haemophilus influenzae is a common species (blood lover), with subtypes like H. parainfluenzae
Haemophilus influenzae
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Morphology: Gram-negative coccobacillus, measuring 1 μm.
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Cultivation: Requires growth factors (X = Haem, V = NAD) on chocolate agar. A characteristic feature is satellitism, where Haemophilus colonies grow around other bacteria.
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Virulence factors: PRP (polyribitol phosphate) capsule (antiphagocytic), LPS (endotoxin – causes fever and inflammation, impairs respiratory epithelial cell ciliary function), IgA1 protease (colonization), pili and non-pilus adhesins (colonization of oropharynx), survival in respiratory epithelial cells.
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Reservoir and Transmission: Humans (mostly endogenous/exogenous), via close contact with respiratory droplets.
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Infection involves attachment to cells in the upper respiratory tract (via fimbriae and IgA1 protease), endotoxin disabling respiratory cilia from cleaning the bacteria, leading to local spread (ears, sinuses, lungs, soft tissues) or systemic spread (blood and brain).
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Classified in encapsulated and non-encapsulated types.
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Encapsulated H. influenzae type b (Hib) is a significant cause of infections like bacteremia, meningitis, epiglottitis, and cellulitis in children.
Bordetella pertussis
- Morphology: Gram-negative coccobacillus.
- Cultivation: Requires special media (Bordet-Gengou agar)
- Adhesins (colonisation): Filamentous hemagglutinin (FHA), Pertactin, Fimbriae, Pertussis toxin.
- Toxins: Pertussis toxin, Adenylate cyclase toxin, Dermonecrotic toxin (DNT), Tracheal cytotoxin, and LPS (endotoxin).
- Whooping cough: Primarily affects non-immune children, adults with waning immunity can have milder forms.
- Clinical Course: Incubation (5-10 days, max 21), catarrhal (1-2 weeks – common cold-like symptoms), paroxysmal (1-6 weeks – severe coughing fits), and convalescent (weeks to months).
Brucella & Brucellosis
- Zoonosis: Animal disease transmittable to humans. Brucella species are the causative agents of brucellosis.
- Medically important species: B. abortus (cattle), B. melitensis (goats/sheep), B. suis (pigs), B. canis (dogs).
- Morphology: Gram-negative coccobacilli, non-motile, non-capsulated.
- Cultivation: Requires nutrient-rich agar (e.g., serum, glycerin) with CO2 and aerobic to microaerophilic conditions.
- Incubation periods: Days to weeks.
- Colony characteristics: Fastidious, slow-growing; pinpoint, smooth; visible after 3–5 days incubation at 37°C. Non-hemolytic.
- Virulence factors: LPS (intracellular multiplication in reticuloendothelial system and macrophages), toxic enzymes (catalase, superoxide dismutase).
- Transmission: Primarily through contact with infected animals or consuming animal products; person-to-person is rare.
- Diagnosis: Demonstration by fluorescent antibody, blood culture (not always positive), and serological tests (Rose Bengal test, STAT, ELISA).
- Treatment: Tetracycline + Rifampin.
- Complications: acute febrile illness; potentially affect any organ system; may persist as relapse, chronic localized infections, or delayed convalescence.
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Description
Explore the characteristics and significance of Gram-negative coccobacilli, including key genera such as Haemophilus, Bordetella, and Brucella. This quiz covers their morphology, cultivation requirements, and virulence factors, as well as the specific features of Haemophilus influenzae.
