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Meningococcal disease in Malawi: studies on the genetic relatedness of the bacteria
B Bellete1, L E Cuevas, P Kazembe
1Tropical Medical Microbiology Centre, University of Liverpool, U.K.
Abstract:
Seventy-seven meningococci, isolated from patients and carriers during a large epidemic of meningococcal meningitis in Malawi, were characterized in terms of antimicrobial susceptibility, plasmid content and multi-locus enzyme electrophoresis (MLEE). All the isolates were sensitive to chloramphenicol but six had high enough minimum inhibitory concentrations of penicillin (> or = 2 mg/litre) to render them clinically resistant. Only one isolate was sensitive to sulphonamides but all the isolates were sensitive to rifampicin and ciprofloxacin, two drugs that would be suitable alternatives in prophylaxis. None of the isolates carried plasmids. MLEE indicated that 32 (80%) of the cerebrospinal fluid isolates and 22 (69%) of those from carriers were closely related genetically (in two electropherotypes that differed at only one allele). The Malawian group A meningococci differed from three Ethiopian isolates by two or three alleles, indicating that direct spread from the sub-Saharan meningitis belt to Malawi was unlikely.
Insights
This study analyzed 77 meningococci from a Malawi epidemic. Most strains were susceptible to common antibiotics, but genetic analysis suggests limited direct spread from other regions.
Area of Science:
- Microbiology
- Epidemiology
- Genetics
Background:
- Neisseria meningitidis causes epidemic meningitis globally.
- Understanding antimicrobial resistance and genetic relatedness is crucial for controlling outbreaks.
Purpose of the Study:
- To characterize meningococcal isolates from a Malawi epidemic.
- To assess antimicrobial susceptibility, plasmid carriage, and genetic diversity.
Main Methods:
- Antimicrobial susceptibility testing.
- Plasmid analysis.
- Multi-locus enzyme electrophoresis (MLEE) for genetic typing.
Main Results:
- All isolates were sensitive to chloramphenicol; six showed penicillin resistance.
- High resistance to sulphonamides, but sensitivity to rifampicin and ciprofloxacin.
- No plasmids were detected in any isolates.
- MLEE revealed significant genetic relatedness among Malawi isolates, suggesting local evolution or a common source.
- Genetic divergence from Ethiopian isolates indicated limited direct spread from the sub-Saharan meningitis belt.
Conclusions:
- Meningococci in Malawi during the epidemic showed specific resistance patterns.
- Genetic data suggest limited direct introduction from other known endemic areas.
- Rifampicin and ciprofloxacin are potential prophylactic agents.