Chloramphenicol-resistant Neisseria meningitidis containing catP isolated in Australia.

Earlier workers have described chloramphenicol resistance in meningococci isolated from cerebrospinal fluid sampled in patients in Vietnam (11 cases) and France (one case) during 1987-1996. Here we describe two distinct serogroup B strains isolated in Australia in 1994 and 1997, and found among approximately 1400 invasive meningococcal isolates examined in Australia over a 9 year period. Both were phenotypically chloramphenicol resistant on disc, Etest and agar inclusion MIC and acetylated chloramphenicol examination. DNA amplification and sequencing confirmed the presence of catP and the 3' end of tnpV from Tn4451, a mobilizable element from Clostridium perfringens, although other sequences were not present. Tn4451 has inserted into a gene designated TIGR locus NMB1350 in both isolates with no loss of DNA and no apparent interruption of virulence genes. This second report of chloramphenicol-resistant meningococci is in a setting with a very low volume of systemic chloramphenicol use, but where the high topical use may contribute to recombination events in vivo. Methods for screening for chloramphenicol resistance in meningococci and the in vitro parameters that define this resistance are ill defined.