The bacillus haemophilus influenza causes

Question

UnlockIAS · Accepted Answer

Correct — C, Whooping cough. That is what the Uttar Pradesh Public Service Commission's official key sheet for Booklet A marks for this question, and the official key is what decides marks, so it is stated first and without qualification. It is also, on the medical record, wrong — and a student is far better served by being told so than by being taught a falsehood. Haemophilus influenzae, particularly the encapsulated type b (Hib), is a Gram-negative coccobacillus that causes acute bacterial meningitis, epiglottitis, pneumonia, bacteraemia and infections of the ear, eye and sinuses, with young children the classic victims. Whooping cough is caused by an entirely different bacterium, Bordetella pertussis. The most likely origin of the examiner's error is a naming accident: Bordetella pertussis was formerly classified in the genus Haemophilus, as Haemophilus pertussis (and Bordetella parapertussis as Haemophilus parapertussis), and that obsolete name survives in older textbook lineages, where it makes 'Haemophilus' and 'whooping cough' look connected. On the four options printed here, the scientifically correct choice is (a), a form of meningitis in young children — Hib meningitis is precisely the disease the Hib component of India's pentavalent vaccine exists to prevent. The species name is a second historical accident of the same kind: Richard Pfeiffer, working in 1893, isolated the organism from influenza patients and took it to be the cause of influenza, and the name stuck even after influenza was shown to be viral. Note also that the stem's own wording is loose — the organism is a coccobacillus, not a member of the genus Bacillus.

Why the other options are wrong — (a) This is the medically correct statement, and it is important to say so rather than to invent a reason against it. Haemophilus influenzae type b was, before mass vaccination, a leading cause of acute bacterial meningitis in children under five, alongside epiglottitis and pneumonia. The commission's key nonetheless marks (c), and this card follows the key because the key governs the marks for this paper. Carry (a) as the microbiology you will need in every other examination and in the Hib-vaccine questions that follow from it, and carry (c) as what this particular paper rewarded.  (b) Genuinely wrong, and the trap the species name sets. Influenza is caused by influenza viruses — orthomyxoviruses, of which types A, B and C infect humans — not by any bacterium. The organism carries the epithet 'influenzae' only because Richard Pfeiffer isolated it from influenza patients in 1893 and wrongly concluded that it was the causative agent; the misnomer survived the correction. Bacteria such as H. influenzae can, however, cause secondary infections on top of viral influenza, which is part of why the mistake persisted so long.  (d) Not wrong as biology, but not the disease this organism is defined by. Haemophilus influenzae genuinely is a cause of pneumonia, especially in children and in adults with chronic lung disease; the commonest bacterial cause of community-acquired pneumonia, however, is Streptococcus pneumoniae. Among the four options, the presentation classically attributed to Hib in young children is meningitis, which is why (a) rather than (d) is the medically best answer here.

Concept: Two separate ideas are being tested, and only one of them is microbiology. The first is that a bacterium's name is a historical artefact and not a description of what it does: Haemophilus influenzae is named for influenza it does not cause, and Bordetella pertussis once sat inside the genus Haemophilus as Haemophilus pertussis before being moved out. The second is the actual disease map. Haemophilus influenzae type b, an encapsulated Gram-negative coccobacillus, colonises the nasopharynx and can invade to produce meningitis, epiglottitis, pneumonia and septicaemia in unvaccinated young children. Bordetella pertussis, by contrast, attaches to the ciliated epithelium of the respiratory tract and produces pertussis toxin, giving the long paroxysmal cough with its characteristic inspiratory whoop. The vaccines follow the same split: in India Hib is delivered through the pentavalent vaccine under the Universal Immunisation Programme, while pertussis is the 'P' of DPT.

State PCS 2022 Q64 — Science & Technology PYQ with Answer

State PCS 2022 Q64 — Science & Technology PYQ with Answer