Antimicrobial Susceptibility of Staphylococcus aureus Isolated from Recreational Waters and Beach Sand in Eastern Cape Province of South Africa

Abstract

<i>Background</i>: Resistance of <i>Staphylococcus aureus</i> to commonly used antibiotics is linked to their ability to acquire and disseminate antimicrobial-resistant determinants in nature, and the marine environment may serve as a reservoir for antibiotic-resistant bacteria. This study determined the antibiotic sensitivity profile of <i>S.</i><i>aureus</i> isolated from selected beach water and intertidal beach sand in the Eastern Cape Province of South Africa. <i>Methods</i>: Two hundred and forty-nine beach sand and water samples were obtained from 10 beaches from April 2015 to April 2016. <i>Staphylococcus aureus</i> was isolated from the samples using standard microbiological methods and subjected to susceptibility testing to 15 antibiotics. Methicillin-resistant <i>Staphylococcus aureus</i> (MRSA) was detected by susceptibility to oxacillin and growth on Brilliance MRSA II agar. Antibiotic resistance genes including <i>mec</i>A, <i>fem</i>A <i>rpo</i>B, <i>bla</i>Z, <i>erm</i>B, <i>erm</i>A, <i>erm</i>C, <i>van</i>A, <i>van</i>B, <i>tet</i>K and <i>tet</i>M were screened. <i>Results</i>: Thirty isolates (12.3%) were positive for <i>S. aureus</i> by PCR with over 50% showing phenotypic resistance to methicillin. Resistance of <i>S. aureus</i> to antibiotics varied considerably with the highest resistance recorded to ampicillin and penicillin (96.7%), rifampicin and clindamycin (80%), oxacillin (73.3%) and erythromycin (70%). <i>S.</i><i>aureus</i> revealed varying susceptibility to imipenem (96.7%), levofloxacin (86.7%), chloramphenicol (83.3%), cefoxitin (76.7%), ciprofloxacin (66.7%), gentamycin (63.3%), tetracycline and sulfamethoxazole-trimethoprim (56.7%), and vancomycin and doxycycline (50%). All 30 (100%) <i>S. aureus</i> isolates showed multiple antibiotic-resistant patterns (resistant to three or more antibiotics). The <i>mec</i>A, <i>fem</i>A, <i>rpo</i>B, <i>bla</i>Z, <i>erm</i>B and <i>tet</i>M genes were detected in 5 (22.7%), 16 (53.3%), 11 (45.8%), 16 (55.2%), 15 (71.4%), and 8 (72.7%) isolates respectively; <i>Conclusion</i><i>s</i>: Results from this study indicate that beach water and sand from the Eastern Cape Province of South Africa may be potential reservoirs of antibiotic-resistant <i>S. aureus</i> which could be transmitted to exposed humans and animals.