True statement regarding diptheria is :

Diagnosis of Diptheria i. Isolation by culture : Swabs are inoculated on : – Loeffler’s serum slope (growth is rapid) : for rapid diagnosis. – Tellurite blood agar (growth is delayed but it is particularly important in isolation of bacilli from convalescent, contacts, carriers) : Selective media. – Blood agar (for differentiating staphylococcal and streptococal pharyngitis). convalescent, contacts, carriers) : Selective media. – Blood agar (for differentiating staphylococcal and streptococal pharyngitis). ii. Demonstration of toxicity of isolated strain : In vivo test – done by infected broth emulsion of culture subacutaneously and intracutaneously into guinea pigs. In vitro test – Elek’s gel precipitation test and tissue culture test on agar overlay of cell culture monolayer. Control of Diptheria i. Cases – Antitoxin + penicillin or erythromycin Park 19/e, p 137 ii. Carriers – Erythromycin iii. Contacts – a. When primary immunization or booster dose was received within the previous 2 years. No further treatment. b. When primary immunization or booster dose was received more than 2 years ago. Only a booster dose of diphtheria toxoid. c. Non immunized close contacts : Prophylatic penicillin or erythromycin 1000 - 2000 units of diphtheria antitoxin Active immunization against diphtheria. iv. Community – Only effective control is by active immunization with diphtheria toxoid of all infants with subsequent booster doses every 10 years thereafter. Remember : Vaccine ‘being a toxoid’ is not directed against organism and hence immunization does not prevent carrier state which is due to organism not due to toxin.