A child presented with a history of fever, cough, and purulent sputum production.The culture examination shows the following(growth of the pathogenic organism is marked by yellow arrow).Regarding the pathogenic organism for this condition,which of the following statement is true?
A. Requires Factors X and V for growth
B. Capsule in type B is a major factor for virulence
C. Resistant to Penicillin
D. All of the above
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Correct Answer » D
Explanation
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Ans:D. All of the above.
The patient is suffering from H.Influenza pneumonia.
On culture examination on Blood agar,Satellite phenomenon is see.
Haemophilus influenzae
- It is a Gram-negative, coccobacillary, facultatively anaerobic pathogenic bacterium .
- Types:: the unencapsulated strains and the encapsulated strains.
There are six generally recognized types of encapsulated H. influenzae: a, b, c, d, e, and f.
The presence of the capsule in encapsulated type b (Hib) is known to be a major factor in virulence.
Vaccination with Hib conjugate vaccine is effective in preventing Hib infection.
- Most strains of H. influenzae are opportunistic pathogens.
In infants and young children, H. influenzae type b (Hib) causes bacteremia, pneumonia, epiglottitis and acute bacterial meningitis.
- Clinical features:May include initial symptoms of an upper respiratory tract infection.
Clinical diagnosis :
By bacterial culture or latex particle agglutinations.
- Diagnosis is considered confirmed when the organism is isolated from a sterile body site. In this respect, H. influenzae cultured from the nasopharyngeal cavity or sputum would not indicate H. influenzae disease, because these sites are colonized in disease-free individuals.
- Bacterial culture of H. influenzae is performed on agar plates, the preferable one being chocolate agar, with added X (hemin) and V (nicotinamide adenine dinucleotide) factors.
- Blood agar growth is only achieved as a satellite phenomenon around other bacteria.
- H. influenzae will grow in the hemolytic zone of Staphylococcus aureus on blood agar plates; the hemolysis of cells by S. aureus releases factor V which is needed for its growth. H. influenzae will not grow outside the hemolytic zone of S. aureus.
Treatment:
Antibiotics:mainstay of treatment:
- In severe cases, cefotaxime and ceftriaxone delivered directly into the bloodstream are the elected antibiotics, and, for the less severe cases, an association of ampicillin and sulbactam, cephalosporins of the second and third generation, or fluoroquinolones are preferred.
- Macrolide antibiotics (e.g., clarithromycin) may be used in patients
- Haemophilus influenzae produces beta-lactamases, and it is also able to modify its penicillin-binding proteins, so it has gained resistance to the penicillin family of antibiotics.
