TRENDS AND SEASONALITY OF ANTIBIOTIC-RESISTANCE OF NEISSERIA-GONORRHOEAE

Over 8400 pretreatment isolates of N. gonorrhoeae collected in the USA between Nov. 1972 and April 1975 were tested for their in vitor resistance to penicillin, ampicillin, tetracycline and spectinomycin. Trends and seasonality of resistance were examined by a harmonic regression technique. During the study period, there was a significant difference among years in mean minimal inhibitory concentrations (MIC) for each antibiotic (P < 0.001 for penicillin, ampicillin and tetracycline; P < 0.05 for spectinomycin), and the mean MIC for each antibiotic decreased. Resistance to tetracycline and penicillin was highest in winter months. Seasonality of resistance, alone or as an interaction with year, approached significance (P < 0.10) or was significant (P < 0.05) for all 4 antibiotics.