Emergence of Non-Ceftriaxone-Susceptible Neisseria meningitidis in India

V. Manchanda and P. Bhalla reported eight serogroup A Neisseria meningitidis non-ceftriaxone-susceptible isolates in India showing MICs ranging from 0.25 to 8 μg/ml (5). This is of great concern, as ceftriaxone is used for treatment of bacterial meningitis. In the meningitis belt of Africa, where outbreaks are caused mostly by serogroup A meningococci, ceftriaxone is scheduled to be an alternative to oily chloramphenicol for treatment of patients. As five of eight isolates are also resistant to chloramphenicol, I hope that such strains never reach Africa: it would be a catastrophe. Increasing numbers of N. meningitidis strains with decreased susceptibility to penicillin G (MICs of >0.064 μg/ml to ≤1 μg/ml) have been reported in recent years from many countries, due to the presence of mosaic structures in the penA gene (3); these isolates are susceptible to ceftriaxone. Only a few isolates of N. meningitidis resistant to penicillin via plasmid-encoded β-lactamase production have been found in Spain, Canada, and South Africa (2, 4, 7). The two isolates from Spain showed good susceptibility to ceftriaxone (1). As this is the first time that non-ceftriaxone-susceptible meningococci have been identified showing such high MICs, in my opinion, Gram staining and latex agglutination are not sufficient for their characterization. The authors should give us the results of culture of these strains on Trypticase soy agar, chocolate agar, and chocolate plus antibiotics (vancomycin, nystatin, and colistin); utilization of glucose, maltose, lactose, and sucrose; oxidase, catalase, and tributyrin tests; reduction of nitrate; and the presence or not of gamma glutamyl transferase (6) and β-lactamase. For determination of serogroup on culture, I think that serum is better than latex. At least to show the clonality of these strains, it is important to characterize them using typing, subtyping, and multilocus sequence typing.

I hope that the authors will give these data in their response. If they don't have reagents to achieve the characterization of these strains and to identify the mechanisms of resistance, I propose the authors send such isolates to Dr. P. Nicolas, Head of the Meningococcus Unit, WHO Collaborating Center for Reference and Research on Meningococci, IMTSSA, BP 46, 13998 Marseille Armees, France.