Species status of Neisseria gonorrhoeae: evolutionary and epidemiological inferences from multilocus sequence typing

Background

Various typing methods have been developed for Neisseria gonorrhoeae, but none provide the combination of discrimination, reproducibility, portability, and genetic inference that allows the analysis of all aspects of the epidemiology of this pathogen from a single data set. Multilocus sequence typing (MLST) has been used successfully to characterize the related organisms Neisseria meningitidis and Neisseria lactamica. Here, the same seven locus Neisseria scheme was used to characterize a diverse collection of N. gonorrhoeae isolates to investigate whether this method would allow differentiation among isolates, and to distinguish these three species.

Results

A total of 149 gonococcal isolates were typed and submitted to the Neisseria MLST database. Although relatively few (27) polymorphisms were detected among the seven MLST loci, a total of 66 unique allele combinations (sequence types, STs), were observed, a number comparable to that seen among isolate collections of the more diverse meningococcus. Patterns of genetic variation were consistent with high levels of recombination generating this diversity. There was no evidence for geographical structuring among the isolates examined, with isolates collected in Liverpool, UK, showing levels of diversity similar to a global collection of isolates. There was, however, evidence that populations of N. meningitidis, N. gonorrhoeae and N. lactamica were distinct, with little support for frequent genetic recombination among these species, with the sequences from the gdh locus alone grouping the species into distinct clusters.

Conclusion

The seven loci Neisseria MLST scheme was readily adapted to N. gonorrhoeae isolates, providing a highly discriminatory typing method. In addition, these data permitted phylogenetic and population genetic inferences to be made, including direct comparisons with N. meningitidis and N. lactamica. Examination of these data demonstrated that alleles were rarely shared among the three species. Analysis of variation at a single locus, gdh, provided a rapid means of identifying misclassified isolates and determining whether mixed cultures were present.

Molecular characteristics and epidemiology of meningococcal carriage, Burkina Faso, 2003

Meningococcal serogroups are genetically diverse and short-lived in the African meningitis belt.

To describe Neisseria meningitidis strains in the African meningitis belt in 2003, we obtained 2,389 oropharyngeal swabs at 5 monthly visits in a representative population sample (age range 4–29 years) in Bobo-Dioulasso, Burkina Faso. A total of 152 carriage isolates were grouped, serotyped, and genotyped. Most isolates were NG:NT:NST sequence type (ST) 192 (63% of all N. meningitidis), followed by W135:2a:P1.5,2 of ST-11 (16%) and NG:15:P1.6 of ST-198 (12%). We also found ST-2881 (W135:NT:P1.5,2), ST-751 (X:NT:P1.5), and ST-4375 (Y:14:P1.5,2) but not serogroups A or C. Estimated average duration of carriage was 30 days (95% confidence interval 24–36 days). In the context of endemic group W135 and meningococcal A disease, we found substantial diversity in strains carried, including all strains currently involved in meningitis in this population, except for serogroup A. These findings show the need for large samples and a longitudinal design for N. meningitidis serogroup A carriage studies.

Bacteraemic pneumonia caused by Neisseria lactamica with reduced susceptibility to penicillin and ciprofloxacin in an adult with liver cirrhosis

This report presents a case of bacteraemic pneumonia caused by Neisseria lactamica in an adult patient with liver cirrhosis who was successfully treated with ceftriaxone. The isolate was confirmed as N. lactamica by analysis of a partial sequence of the 16S rRNA gene; it had reduced susceptibilities to penicillin (MIC 0.75 μg ml−1) and ciprofloxacin (MIC ⩾0.5 mg l−1).