| Summary: | <p>Abstract</p> <p>Background</p> <p><it>Staphylococcus aureus </it>is an important pathogen causing a wide range of infections in the hospital and community setting. In order to have adequate information for treatment of <it>S. aureus </it>infections, it is crucial to understand the trends in the antibiotic-resistance patterns. In addition, the occurrence and changes in types of <it>S. aureus</it>, clonal identities, and their geographic spread is essential for the establishment of adequate infection control programmes. In this study, 68 <it>S. aureus </it>isolates obtained from clinical and non-clinical sources in Nigeria between January and April 2009 were characterized using phenotypic and molecular methods.</p> <p>Results</p> <p>All the <it>S. aureus </it>isolates were susceptible to teicoplanin, vancomycin, phosphomycin, fusidic acid, rifampicin, daptomycin, mupirocin, linezolid and tigecycline. Sixteen percent of the isolates were resistant to oxacillin, while 55% and 72% of isolates were resistant to tetracycline and trimethoprim/sulphamethoxazole (cotrimoxazole), respectively (Table <tblr tid="T1">1</tblr>). There was excellent correlation between the broth microdilution assay and detection of antibiotic resistance genes by the multiplex PCR, in the determination of <it>S. aureus </it>resistance to erythromycin, gentamicin, methicillin and tetracycline. A total of 28 <it>spa </it>types were identified in the study, and the predominant <it>spa </it>type among the methicillin-susceptible <it>S. aureus </it>(MSSA) isolates was t084 (13 isolates). The t037-ST241-SCC<it>mec</it>III type was the only clone identified in Maiduguri (North-East Nigeria) while in South-West Nigeria, diversity among the MRSA isolates (t451-ST8-SCC<it>mec</it>V; t008-ST94-SCC<it>mec</it>IV; t002-ST5-SCC<it>mec</it>V; t064-ST8-SCC<it>mec</it>V) was observed. The toxin genes <it>seh </it>and <it>etd </it>were detected in isolates affiliated with clonal complexes CC1, CC80 and sequence type ST25, respectively. The proportion of PVL-positive isolates among MSSA was high (40%). Most of the PVL-positive MSSA isolates were obtained from wound infections and associated with clonal complexes CC1, CC30, CC121 and with sequence type ST152.</p> <tbl id="T1"> <title> <p>Table 1</p> </title> <caption> <p>Antibiotic resistance profile of <it>S. aureu</it><it>s </it>(MSSA and MRSA) from Nigeria</p> </caption> <tblbdy cols="4"> <r> <c> <p/> </c> <c cspan="3" ca="left"> <p><b>Number (%) of resistant isolates among</b>:</p> </c> </r> <r> <c ca="left"> <p><b>Antibiotic</b></p> </c> <c ca="left"> <p><b>MSSA</b></p> <p><b>(n = 57)</b></p> </c> <c ca="left"> <p><b>MRSA</b></p> <p><b>(n = 11)</b></p> </c> <c ca="left"> <p><b>Total</b></p> <p><b>(n = 68)</b></p> </c> </r> <r> <c cspan="4"> <hr/> </c> </r> <r> <c ca="left"> <p>Penicillin</p> </c> <c ca="left"> <p>49 (86)</p> </c> <c ca="left"> <p>11 (100)</p> </c> <c ca="left"> <p>60 (88.2)</p> </c> </r> <r> <c ca="left"> <p>Oxacillin</p> </c> <c ca="left"> <p>0 (0)</p> </c> <c ca="left"> <p>11 (100)</p> </c> <c ca="left"> <p>11 (16.2)</p> </c> </r> <r> <c ca="left"> <p>Teicoplanin</p> </c> <c ca="left"> <p>0 (0)</p> </c> <c ca="left"> <p>0 (0)</p> </c> <c ca="left"> <p>0 (0)</p> </c> </r> <r> <c ca="left"> <p>Vancomycin</p> </c> <c ca="left"> <p>0 (0)</p> </c> <c ca="left"> <p>0 (0)</p> </c> <c ca="left"> <p>0 (0)</p> </c> </r> <r> <c ca="left"> <p>Gentamicin</p> </c> <c ca="left"> <p>1 (1.8)</p> </c> <c ca="left"> <p>9 (81.8)</p> </c> <c ca="left"> <p>10 (14.7)</p> </c> </r> <r> <c ca="left"> <p>Tetracycline</p> </c> <c ca="left"> <p>27 (47.4)</p> </c> <c ca="left"> <p>11 (100)</p> </c> <c ca="left"> <p>38 (55.9)</p> </c> </r> <r> <c ca="left"> <p>Ciprofloxacin</p> </c> <c ca="left"> <p>12 (21.1)</p> </c> <c ca="left"> <p>8 (72.7)</p> </c> <c ca="left"> <p>20 (29.4)</p> </c> </r> <r> <c ca="left"> <p>Moxifloxacin</p> </c> <c ca="left"> <p>0 (0)</p> </c> <c ca="left"> <p>7 (63.6)</p> </c> <c ca="left"> <p>7 (10.3)</p> </c> </r> <r> <c ca="left"> <p>Trimethoprim/sulfamethoxazole</p> </c> <c ca="left"> <p>39 (68.4)</p> </c> <c ca="left"> <p>10 (90.9)</p> </c> <c ca="left"> <p>49 (72.1)</p> </c> </r> <r> <c ca="left"> <p>Phosphomycin</p> </c> <c ca="left"> <p>0 (0)</p> </c> <c ca="left"> <p>0 (0)</p> </c> <c ca="left"> <p>0 (0)</p> </c> </r> <r> <c ca="left"> <p>Fusidic acid</p> </c> <c ca="left"> <p>0 (0)</p> </c> <c ca="left"> <p>0 (0)</p> </c> <c ca="left"> <p>0 (0)</p> </c> </r> <r> <c ca="left"> <p>Erythromycin</p> </c> <c ca="left"> <p>2 (3.5)</p> </c> <c ca="left"> <p>6 (54.5)</p> </c> <c ca="left"> <p>8 (11.8)</p> </c> </r> <r> <c ca="left"> <p>Clindamycin</p> </c> <c ca="left"> <p>0 (0)</p> </c> <c ca="left"> <p>6 (54.5)</p> </c> <c ca="left"> <p>6 (8.8)</p> </c> </r> <r> <c ca="left"> <p>Rifampicin</p> </c> <c ca="left"> <p>0 (0)</p> </c> <c ca="left"> <p>0 (0)</p> </c> <c ca="left"> <p>0 (0)</p> </c> </r> <r> <c ca="left"> <p>Daptomycin</p> </c> <c ca="left"> <p>0 (0)</p> </c> <c ca="left"> <p>0 (0)</p> </c> <c ca="left"> <p>0 (0)</p> </c> </r> <r> <c ca="left"> <p>Mupirocin</p> </c> <c ca="left"> <p>0 (0)</p> </c> <c ca="left"> <p>0 (0)</p> </c> <c ca="left"> <p>0 (0)</p> </c> </r> <r> <c ca="left"> <p>Linezolid</p> </c> <c ca="left"> <p>0 (0)</p> </c> <c ca="left"> <p>0 (0)</p> </c> <c ca="left"> <p>0 (0)</p> </c> </r> <r> <c ca="left"> <p>Tigecycline</p> </c> <c ca="left"> <p>0 (0)</p> </c> <c ca="left"> <p>0 (0)</p> </c> <c ca="left"> <p>0 (0)</p> </c> </r> </tblbdy> </tbl> <p>Conclusions</p> <p>The use of phenotypic and molecular methods provided useful information on antibiotic resistance and molecular diversity of <it>S. aureus </it>in Nigeria. The high proportion of PVL-positive MSSA isolates affiliated to various clonal complexes and detected in all the health institutions is a major concern, both as a source of severe infections and as a potential reservoir that could lead to the emergence of PVL-positive MRSA. This study presents the first baseline information on the nature of the antibiotic resistance genes from <it>S. aureus </it>isolates in Nigeria. There is the need to curtail the spread and establishment of MRSA and PVL-positive MSSA clones in Nigerian health care institutions.</p>
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