Neisseria meningitidis Intermediately Resistant to Penicillin and Causing Invasive Disease in South Africa in 2001 to 2005

Abstract

ABSTRACT Neisseria meningitidis strains (meningococci) with decreased susceptibility to penicillin (MICs, >0.06 μg/ml) have been reported in several parts of the world, but the prevalence of such isolates in Africa is poorly described. Data from an active national laboratory-based surveillance program from January 2001 through December 2005 were analyzed. A total of 1,897 cases of invasive meningococcal disease were reported, with an average annual incidence of 0.83/100,000 population. Of these cases, 1,381 (73%) had viable isolates available for further testing; 87 (6%) of these isolates tested intermediately resistant to penicillin (Pen i ). Pen i meningococcal isolates were distributed throughout all provinces and age groups, and there was no association with outcome or human immunodeficiency virus infection. The prevalence of Pen i was lower in serogroup A (7/295; 2%) than in serogroup B (24/314; 8%), serogroup C (9/117; 8%), serogroup Y (22/248; 9%), or serogroup W135 (25/396; 6%) ( P = 0.02). Pulsed-field gel electrophoresis grouped 63/82 Pen i isolates into nine clusters, mostly according to serogroup. The clustering of patterns from Pen i isolates was not different from that of penicillin-susceptible isolates. Twelve sequence types were identified among 18 isolates arbitrarily selected for multilocus sequence typing. DNA sequence analysis of the penA gene identified 26 different alleles among the Pen i isolates. Intermediate penicillin resistance is thus widespread among meningococcal serogroups, has been selected in a variety of lineages, and, to date, does not appear to be associated with increased mortality. This is the first report describing the prevalence and molecular epidemiology of Pen i meningococcal isolates from sub-Saharan Africa.