Salmonellosis in Lagos, Nigeria: incidence of Plasmodium falciparum-associated co-infection, patterns of antimicrobial resistance, and emergence of reduced susceptibility to fluoroquinolones.

The present study was undertaken to examine the status of antimicrobial resistance in Salmonella-associated diseases, by verifying possible emergence of reduced susceptibility to fluoroquinolones in Salmonella isolates and determining the incidence of Plasmodium falciparum-associated co-infection with Salmonella serotypes. Antimicrobial resistance in clinical isolates of Salmonellae was examined for a 12-month period. Four hundred and forty-one patients comprising two groups were recruited. Group A comprised 235 patients diagnosed by clinicians of having pyrexia, and group B included stool samples of 206 patients presenting with gastroenteritis. Samples were cultured and isolates identified, and drug susceptibility testing was performed using the standard methods. Of the 235 samples screened in group A, 42 Salmonella isolates and 107 Plasmodium spp. were identified. Of the 42 Salmonella isolates, 19 (45.2%) were Salmonella Typhi, 9 (21.4%) S. Enteritidis, and 7 (16.7%) each of S. Paratyphi and S. Arizonae. Plasmodium spp.-associated co-infection with Salmonellae was observed in 16 patients mostly in complicated typhoidal cases and S. Enteritidis-associated bacteraemia. Fifty-three of the 206 stool samples from group B patients were confirmed positive for bacterial pathogens, made up of 35 Salmonella and 18 Shigella isolates. Of the Salmonella isolates, 18 (51.4%) were S. Enteritidis, 11 (31.4%) S. Arizonae, 4 (11.4%) S. Paratyphi, and 2 (5.7%) S. Typhi. There was no statistically significant difference (p < 0.01) in antimicrobial resistance patterns exhibited among typhoidal Salmonellae isolated in 2000 and 2005. A similar trend in resistance was recorded for non-typhoidal Salmonellae (p < 0.05). For the first time in Lagos, Nigeria, Salmonella isolates (10-18%) with reduced susceptibility to both ciprofloxacin and ofloxacin at MIC50 and MIC90 values of 0.015 and 0.03 microg/mL respectively were found. Despite this development, ciprofloxacin and ofloxacin remain the drug of choice for severe cases of salmonellosis, although caution should be exercised by clinicians in their prescriptions such that fluoroquinolone antibiotic therapy is used only in laboratory-proven cases of typhoid fever and Salmonella-associated bacteraemia to preserve its efficacy.

Associated risk factors and pulsed field gel electrophoresis of nasal isolates of Staphylococcus aureus from medical students in a tertiary hospital in Lagos, Nigeria

Staphylococcus aureus infections are growing problems worldwide with important implications in hospitals. The organism is normally present in the nasal vestibule of about 35 percent of apparently healthy individuals and its carriage varies between different ethnic and age groups. Staphylococcal nasal carriage among health workers is particularly important to establish new clones and track origin of infections during outbreak situations. To determine the carriage rate and compare the pulsed field gel patterns of the strains, nasal swabs were collected from 185 medical students in a teaching hospital in Lagos, Nigeria. Isolates of S. aureus were tested for heamolysin production, methicillin sensitivity and Pulsed Field Gel Electrophoresis (PFGE) was performed. The results showed S.aureus nasal carrier rate of 14 percent with significant rate among males compared to females. All the isolates produced heamolysin. Antibiotic susceptibility pattern revealed that majority of the isolates was susceptible. Five strains (19 percent) harboured resistant determinants to penicillin and tetracycline. None of the strains was resistant to methicillin. 44 percent of the isolates typed by PFGE had type B, the most predominant pulsotype. PFGE A clone exhibited a single resistance phenotype suggesting a strong clonal relationship that could punctual an outbreak in the hospital. The results speculate that nasal carriage among medical personnel could be a function of various risk factors. Personal hygiene and behaviour may however be the means to reducing colonization and spread of S.aureus in our hospitals.