Showing the limitations of available phenotypic assays to detect Burkholderia pseudomallei from clinical specimens in Nigeria.

The genus Burkholderia comprises Gram-negative bacteria that are metabolically complex and versatile, often thriving in hostile settings. Burkholderia pseudomallei , the causative agent of melioidosis, is a prominent member of the genus and a clinical pathogen in tropical and sub-tropical regions. This pathogen is well known for its multidrug resistance and possible bioweapon potential. There is currently no report of the pathogen from clinical specimens in Nigeria, which might be due to misdiagnosis with phenotypic assays. This study aims to explore the accuracy of the use of phenotypic assays to diagnose B. pseudomallei in Nigeria. Two hundred and seventeen clinical samples and 28 Gram-negative clinical isolates were collected and analysed using Ashdown's selective agar and monoclonal antibody-based latex agglutination. Species-level identification was achieved using the analytical profile index (API) 20NE system. The susceptibility of the isolates to nine different antimicrobial agents was determined using the disc diffusion method. A total of seventy-four culture-positive isolates were obtained using Ashdown's selective agar. Twenty-two of these isolates were believed to be B. pseudomallei through the monoclonal antibody-based latex agglutination test and the API 20NE system subsequently identified 14 isolates as Burkholderia . The predominant Burkholderia species was B. cepacia with an isolation rate of 30.8 % (8/26). No isolate was distinctively identified as B. pseudomallei but five isolates were strongly suspected to be B. pseudomallei with similarity indices ranging from 81.9-91.3 %. Other bacterial species with definitive identity include Aeromonas sp., Sphingomonas sp. and Pseudomonas aeruginosa . The antibiotic susceptibility results revealed an overall resistance to amoxicillin-clavullanic acid of 71.4 %, to cefepime of 33.3 %, to trimethoprim-sulfamethoxazole of 38.1 %, to piperacillin-tazobactam of 33.3 %, to imipenem of 66.7 %, to doxycycline of 57.1% and to ceftazidime of 66.7 %. The highest intermediate resistance was observed for cefepime and piperacillin-tazobactam with a value of 66.7 % each, while there was no intermediate resistance for gentamicin, colistin and imipenem. Our findings, therefore, show that phenotypic assays alone are not sufficient in the diagnosis of melioidosis. Additionally, they provide robust support for present and future decisions to expand diagnostic capability for melioidosis beyond phenotypic assays in low-resource settings.

Genetics of bi-component leukocidin and drug resistance in nasal and clinical Staphylococcus aureus in Lagos, Nigeria.

BACKGROUND: Resistant and virulent Staphylococcus aureus is a global public health challenge. Staphylococcal Bi-component leukotoxins are cytolytic to immune cells and evolve to disarm the innate immunity during infections, hence the severity of the disease. OBJECTIVE: We studied drug resistance profile and the occurrence of bi-component leukocidin in clinical and nasal S. aureus in Lagos, Nigeria. METHOD: Ninety-two S. aureus (70 clinical and 22 nasal) strains were characterized by conventional and molecular methods. RESULT: Of the resistance profiles generated, no isolate was resistant to fosfomycin, fusidic acid, teicoplanin, vancomycin, linezolid, mupirocin, nitrofurantoin and tigecycline. Twelve MRSA carrying staphylococcal cassette chromosome mecA gene types I, III, and IV elements were identified only in the clinical samples and type I dominated. High rates of lukE/D (100% among MRSA) and lukPV (dominated MSSA) were recorded among the nasal and clinical isolates. Staphylococcus aureus harboring only lukE/D (from clinical & colonizing MSSA) and combined lukE/D and lukPV (mostly from clinical MSSA, colonizing MSSA and clinical MRSA) toxins were found. CONCLUSION: Although, mecA resistant genes were found only among clinical MRSA, the occurrence of other bi-component leukocidin genes in a large proportion among the isolates from both community and clinical settings is a major concern. The need for effective resistance and virulence factor surveillance, re-enforcement of antibiotic stewardship and good infection control policy, to prevent dissemination of epidemic strains is highlighted.

CARRIAGE OF MULTIDRUG RESISTANT ENTEROCOCCUS FAECIUM AND ENTEROCOCCUS FAECALIS AMONG APPARENTLY HEALTHY HUMANS.

BACKGROUND: Enterococci are indigenous flora of the gastro-intestinal tracts of animals and humans. Recently, interest in two major species, E. faecium and E. faecalis, has heightened because of their ability to cause serious infections and their intrinsic resistance to antimicrobials. This study was aimed at determining the prevalence of E. faecium and E. faecalis in human faecal samples and evaluating the susceptibility of the isolates to antibiotics. MATERIALS AND METHODS: One hundred faecal samples were collected from apparently healthy individuals and analysed using conventionalbacteriological methods. The susceptibility profile of the isolates to nine antibiotics were determined using disk diffusion method. RESULTS: Seventy-three (73) Enterococcus were phenotypically identified and 65 of the isolates were differentiated into 36 (55.4%) E. faecium and 29 (44.6%) E. faecalis. Eight (8) isolates could not be identified by the conventional biochemical methods employed. No dual colonization by the E. faecalis and E. faecium was observed and isolation rate was not dependent on sex of the participants. All the isolates were resistant to ceftriaxone, cefuroxime and ceftizoxime. Enterococcus faecium exhibited resistance toerythromycin (88.9%), gentamicin (77.8%), amoxicillin-clavulanate (63.9%), ofloxacin (44.4%), teicoplanin (19.4%) and vancomycin (16.7%). Enterococcus faecalis showed the least resistance to vancomycin (13.8%) and teicoplanin (27.7%). Remarkable multiple antibiotic resistances to the classes of antibiotic tested were observed among the two species. CONCLUSION: The high carriage rate of antibiotic resistant E. faecium and E. faecalis in this study provides information on the local antibiotic patterns of our enterococci isolates thereby suggesting that they could present as important reservoir and vehicle for dissemination of resistant genes in our community.

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% 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% 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%) harboured resistant determinants to penicillin and tetracycline. None of the strains was resistant to methicillin. 44% 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.

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.

Resistotyping of Campylobacter jejuni.

The principal objective of typing in epidemiology is to trace a strain as it passes from one individual to another. Resistotyping is a phenotypic method that consists of testing bacterial strains against a set of arbitrarily chosen chemical agents, whereby, a resistance pattern that is characteristic of a strain is generated and, is believed to describe the isolates for epidemiological purposes. This simple typing system is described for campylobacter isolated in Lagos, Nigeria. Resistotyping was performed with twenty chemical agents incorporated into disc. The resistotyping results revealed that the twenty isolates from human and chickens belonged to 14 different resistotypes with the largest group comprising 25% of the isolates. The human strains were distinctly differentiated into eight resistotypes. All the Campylobacter Jejuni isolates were resistant to potassium chloride (A), Boric acid (B), Sodium biselenite (C), potassium dischromate (F), potassium permanganate (I) ferrous sulphate (N), magnesium sulphate (O), sodium hydrogen phosphate (P), sodium sulphate (Q), and magnesium chloride (R). Only one strain was resistant to mercuric chloride (M) while three of the strains were sensitive to disodium orthophosphate (H), sodium azide (J), and metronidazole (T). The method seems to be adequate for defining the relatedness of our isolates in epidemiologic situation and has proven promising for Campylobacter jejuni in our environment.