NEISSERIA MENINGITIDIS CARRIER RATE AMONG MILITARY RECRUITS IN KERMAN, SOUTH-EAST OF IRAN

Background: Meningococcal diseases have been recognized as an important problem in military population. Most patients with meningococcal diseases have not had a direct contact with other similar patients. Thus, asymptomatic carrier is presumably the major source of transmission of pathogenic strains. Objective: To determine the carrier rate of the newly-arrived recruits to a military center and to find out the sensitivity pattern of the isolated strains. Methods: One thousand four hundred and fifty-six tonsilopharyngeal samples were collected during a 15-month period from 2002 through 2003. All the samples were plated on chocolate agar supplemented with 3 mg/L vancomycin and 2 mg/L amphotericin B. Meningococci were identified by a standard method. Sero-grouping of part of isolated strains was carried out by the slide agglutination test. The antibiotic resistance was measured by the broth macrodilution method with penicillin, rifampicin, and ciprofloxacin. Sensitivity of part of isolated strains against two antiseptic solutions, chlorhexidine and eucalyptus inhaler, were also tested. Results: The mean of meningococcal carrier rate in 4+1 seasons was 11.4% for the newlyarrived recruits. After 1 ½ – 2 months, it raised to 33%. Increases observed in cold seasons were considerable. During the second sampling stage, the mean carrier rate was 38% for smokers and 28% for nonsmokers. Strains isolated from carriers were phenotypically heterogeneous, with a dominance of group B (~27%). All the invasive strains recovered concurrently from the patients with meningococcal diseases also belonged to this sero-group. The median of minimum inhibitory concentrations (MICs) for penicillin and rifampicin were 0.06 and 0.03 μg/mL, respectively. The MIC50 of ciprofloxacin was 0.004. Thirteen percent of the isolates were partially resistant to penicillin. It was 8% for rifampicin. More than 60% of the isolated strains were sensitive to 1/600 dilution of chlorhexidine. It was negligible against the eucalyptus inhaler. Conclusion: Our results indicate that the transmission rate is strongly associated with the season. Furthermore, there is a correlation between the carrier state and smoking habit. Domination of B sero-group among the carriers and patients could be due to the lack of B antigen in the available vaccines. The resistance pattern of tested strains was similar to that of other studies.