Repeated Medical PG Question- 90

#MICROBIOLOGY (INI-CET)

In a completely and adequately immunized child against Diphtheria, the throat swab was collected. It showed the presence of Corynebacterium diphtheriae like organisms on Albert staining. These organisms can have one of the following properties on further laboratory processing 

A. It can grow on Potassium tellurite medium

B. It would show a positive Elek's gel precipitation test

C. It can be pathogenic to experimental guinea pigs

D. It can produce cytotoxicity in tissue cultures

Correct Answer is A. 

▪️It can grow on Potassium tellurite medium 

▪️This child is a carrier of Diphtheria.

▪️Remember, adequate immunization does not prevent the carrier state because the vaccine is active against the toxin (not against the organism).

▪️Tellurite medium is particularly important in the isolation of diphtheria bacilli from convalescent contacts and carriers as in these cases they may be outnumbered by the other bacteria.

▪️The other three options are about the virulence testing of the isolated bacilli. (see above explanation)

▪️These tests will be positive only if the isolated diphtheria like organism is virulent. Otherwise all of them will be negative.

Q- A person is HBsAg positive, but Anti-HBc Antibody is negative. What should be the next step?

     A. Repeat test after 6 months

     B. Check HBV DNA load

     C. Check HBeAg, if positive start interferon

      D. Reassure patient that he does not have any disease

Answer: B. Check HBV DNA load

Chronic Hepatitis B – Parameters:

🔹HBsAg positive; Anti- HBc Ab negative.

🔹Presence or absence of serum hepatitis Be antigen (HBeAg)

🔹HBeAg-reactive & HbeAg negative

🔹HBV DNA level correlate with liver injury level & has progression risk

Treatment pre-requisites:

HBV-DNA load should be done before initiating treatment.

Q- Action of Papain on an IgG molecule produces?

       A. 2 Fc fragments & 1 Fab fragment

       B. 1 Fc fragment & 2 Fab fragments

       C. 2 Fc fragments & 2 Fab fragments

       D. 1 Fc fragment & 1 Fab fragment

Answer is B. 1 Fc fragment & 2 Fab fragments 

If an antibody molecule is treated with a proteolytic enzyme (eg, Papain), peptide bonds in the hinge region are broken. This breakage produces two identical Fab fragments, which carry the antigen-binding sites, and one Fc fragment, which is involved in placental transfer, complement fixation, attachment for various cells, and other biologic activities.