Antibiotics and Immunity

The intestinal microflora of the young breast fed infants consists mainly of Bifidobacteria, which are Gram-positive. The low pH in the large intestine of the breast fed babies would be unfavorable for the growth of E. coli, and so Bifidobacteria proliferate.

Streptococcus pyogenes secretes a toxin that acts as cardiotoxin (SLO) in rabbits. It disrupts the cardiac pumping in rabbits. This toxin acts as leukocidin in humans, destroying the leukocyte.

Isoniazid acts by blocking pyridoxine and nicotinamide catalyzed reactions. It is a structural analog of pyridoxine and nicotinamide and thus, can block pyridoxine and nicotinamide catalyzed reactions.

Anthramycin is an anti-tumor antibiotic. It works by inhibiting the synthesis of RNA and DNA of carcinoma cells.

Bacterial cells susceptible to penicillin can be protected from destruction if the medium in which they are exposed is of high osmotic pressure. The high osmotic pressure prevents the cells from bursting.

Erythromycin manifests its action by binding to 23S rRNA component of 50S subunit of the ribosome, thereby blocking the tunnel where the polypeptide string is supposed to exist.

Fosfomycin inhibits conversion of UDP-GlcNAc to UDP-MurNAc. This is the first committed step in peptidoglycan biosynthesis, so amenable to selective action.

Lincomycin belongs to lincosamide group of antibiotics. Lincomycin is an antibiotic that fights bacteria.

Quinolones bind to DNA gyrase as a topoisomerase inhibitor, thereby inhibiting synthesis of DNA.

Bacitracin is used to distinguish S. pyogenes from other β-hemolytic streptococci because S. pyogenes is sensitive to bacitracin and other beta hemolytic bacteria are resistant.

Monobactams work only against aerobic gram negative bacteria, e.g. Neisseria, Pseudomonas etc.

This is the correct match. Chlorotetracycline is produced by S. aureofaciens, Streptomycin is produced by S. griseus, Nystatin is produced by S. noursei and Vancomycin is produced by S. orientalis.

Rabies is caused by the rabies virus, which attacks the central nervous system. Therefore, treatment requires antiviral medications. Antibacterial drugs target bacteria, antifungal drugs target fungi, and antibodies are immune proteins produced by the body - none of these are effective against viral infections.

Sulfonamides were the first systematically used antibacterial drugs in humans, introduced in the 1930s before penicillin became widely available. They inhibit bacterial folic acid synthesis. The other options are incorrect - Oxytetracyclines are tetracycline antibiotics, Desonides is a corticosteroid, and Xanthine derivatives are bronchodilators.

Penicillin V (phenoxymethylpenicillin) is the only penicillin listed that can be administered orally because it is acid-stable and survives gastric digestion. Penicillin G, Benzathine penicillin G, and Procaine penicillin G are all parenteral formulations given by injection as they are destroyed by stomach acid.