In vitro activity of macrolides against Bordetella pertussis strains isolated in 1968 and 30 years later in Poland

Abstract

Bordetella pertussis causes whooping cough, a severe respiratorytract infection. The disease affects all age groups of people, but its severity is greatest in young children. In spite of vaccination programmes, whooping cough epidemics continue to occur [1,2]. Erythromycin (main component, erythromycin A) is regarded as the antibiotic of choice for treatment and postexposure prophylaxis of B. pertussis infection. Widespread use of macrolides may lead to changes in susceptibility patterns and the emergence of resistance in earlier susceptible bacteria. Resistance of B. pertussis to erythromycin had not previously been reported until recently,when two B. pertussis isolates that were resistant to this antibiotic were found in the United States [3,4]. The data may indicate a necessity to evaluate the activity of new antimicrobial agents against B. pertussis. The aim of this study was to compare the susceptibility to macrolides of B. pertussis strains isolated in 1968 and 30 years later in Poland. The analysed strains of B. pertussis were isolated from the nasopharynx of children with whooping cough in 1968 (n = 21) and in the years 1997–98 (n = 34). The B. pertussis isolates from 1968 were collected at the Pertussis Laboratory, National Institute of Hygiene and the strains isolated in the years 1997– 98 were collected at Warsaw Sanitary and Epidemiological Station. Macrolide standards of known potency were applied as follows: erythromycin (USP, Rockville, DC, USA, 945 U/mg), azithromycin (Pliva, Zagreb, Croatia, 96.9%), clarithromycin (Abbott Laboratories, Rungis Cedex, France, 992 U/mg), dirithromycin (Eli Lilly, Indiana, IN, USA, 96.9%), oleandomycin (Sigma, St. Louis, MI, USA, 95%), roxithromycin (Hoechst Marion Roussel, Paris La Defense Cedex, France, 100%), spiramycin (Rhone Poulenc Rorer, Antony Cedex, France, 4375 U/mg) and josamycin (Virbac, Carros, France, 999 U/mg). All B. pertussis isolates were stored in a freeze-dried form. The antibiotic agar dilution method was used. Before analysis the strains were subcultured twice on Bordet-Gengou agar supplemented with 30% sheep blood and