MLT GlobeBacteriology: Neisseria & fastidious – page 2
68 Bacteriology MCQs on Neisseria & fastidious with answers and explanations.
A rapidly spreading non-blanching petechial or purpuric rash in a febrile child suggests septicaemia due to:
Meningococcal septicaemia causes a petechial-purpuric rash from vascular damage and DIC.
Purulent conjunctivitis in a newborn within the first days of life (ophthalmia neonatorum) can be caused by which organism acquired during birth?
Babies born to infected mothers can acquire gonococcal eye infection in the birth canal, which can cause blindness.
Acute epiglottitis in an unvaccinated young child is classically caused by:
Hib was the classic cause of epiglottitis and meningitis in young children before routine vaccination.
Neisseria gonorrhoeae attaches to mucosal epithelial cells mainly by means of:
Gonococcal pili mediate adherence to urethral and cervical cells; Neisseria have no flagella and form no spores.
Healthy carriers harbour Neisseria meningitidis mainly in the:
Meningococci colonise the nasopharynx of carriers and spread by respiratory droplets.
Fulminant meningococcal septicaemia with shock and bleeding into the adrenal glands is known as:
Waterhouse-Friderichsen syndrome is adrenal haemorrhage with shock, classically in meningococcaemia.
Gonococcal infection of the cervix in women is important to screen for because it is often:
Many women with gonorrhoea have few or no symptoms, yet can develop pelvic inflammatory disease and infertility.
In vaccinated adult populations, which two bacteria cause most community-acquired bacterial meningitis?
Since Hib vaccination, H. influenzae is uncommon; pneumococcus and meningococcus dominate adult meningitis. E. coli and group B streptococci are neonatal causes.
Which non-culture method is recommended for diagnosing gonorrhoea in a woman using a vaginal or endocervical swab?
NAATs are the most sensitive and specific tests for N. gonorrhoeae in women. Cervical Gram stain is insensitive because of commensal Gram-negative flora; MALDI-TOF requires a cultured isolate.
Which infection is usually diagnosed by serology rather than culture or microscopy?
Coxiella is hazardous and hard to culture, so diagnosis relies on antibodies to phase I and II antigens. The other infections are diagnosed by culture, microscopy or NAAT.
A blood culture from a farmer grows small, slow-growing Gram-negative coccobacilli suspected to be Brucella. At what containment level should further culture work be done?
Brucella is among the commonest causes of laboratory-acquired infection through aerosols; suspected isolates require BSL-3 practices in a biosafety cabinet.
A CSF isolate forms grey, smooth colonies on chocolate agar in 5% CO2 at 37 °C. It is an oxidase-positive Gram-negative diplococcus carried in the nasopharynx of 5-15% of adults. It is:
N. meningitidis colonises the nasopharynx asymptomatically and causes meningitis. N. gonorrhoeae is a genital pathogen; Listeria is a Gram-positive rod.
Chocolate agar is made by heating blood agar to about what temperature, lysing red cells to release X and V factors?
Heating to 75-80 °C lyses erythrocytes and releases haemin and NAD while inactivating NADase, supporting Haemophilus and Neisseria.
Neisseria meningitidis is least likely to cause which condition?
Meningococci cause meningitis, septicaemia and occasionally conjunctivitis, but they are not urinary tract pathogens.
Neisseria gonorrhoeae is least commonly associated with which condition?
Gonococci commonly cause urethritis/cervicitis, disseminated infection with arthritis and ophthalmia neonatorum; endocarditis is rare.
The Koch–Weeks bacillus, a cause of epidemic purulent conjunctivitis, is now classified as:
Koch–Weeks bacillus (formerly H. aegyptius) is now considered a biogroup of H. influenzae. H. ducreyi causes chancroid; K. granulomatis causes donovanosis.
Mycoplasmas lack a cell wall; their plasma membrane is stabilised by incorporating:
Mycoplasmas take up cholesterol from the host or medium into their membrane, which is why serum is added to culture media. They have no peptidoglycan or teichoic acid.
A farm worker develops jaundice, renal failure and haemorrhage after exposure to rat-urine-contaminated water. Which organism is most likely?
Weil's disease is severe leptospirosis (e.g. serovar Icterohaemorrhagiae) acquired from rodent urine. Borrelia causes relapsing fever or Lyme disease.
Moraxella lacunata, a cause of angular blepharoconjunctivitis, appears on Gram stain as:
M. lacunata is a short, broad gram-negative rod typically in pairs (Morax–Axenfeld diplobacillus). Comma shapes suggest Vibrio.
A Neisseria isolate from a urethral discharge produces acid from glucose only, not from maltose, lactose or sucrose. Identify it.
N. gonorrhoeae utilises glucose only. N. meningitidis uses glucose and maltose; N. lactamica also uses lactose.