MLSB ANTIBIOTIC RESISTANT GENES ENCODING FOR ANTIBIOTIC-INACTIVATING ENZYMES ARE FOUND IN ENVIRONMENTAL STRAINS OF STAPHYLOCOCCUS
Marisol Zuniga, Andrey Tatarenkov, Luis Mota-Bravo.
University of California, Irvine, Irvine, CA.
Staphylococci cause approximately 30% of hospital-acquired bacterial infections. Macrolide, lincosamide, and streptograminB (MLSB) antibiotics are commonly used against staphylococcal infections. However, application of MLSB drugs is hampered by the emergence of antibiotic resistance. Our objective was to determine the incidence and diversity of antibiotic inactivating genes in strains of Staphylococcus isolated from public areas. The bacteria were collected from beaches of Southern California, filtered, grown on selective media, and identified using MALDI-TOF. PCR was used to screen for ereA, vgbA, vgbB, lnuA, lnuB, mphC, vatA, vatB, and vatC genes. PCR products were sequenced and analyzed through Mega5 and DNAsp programs. Genes lnuA and mphC were detected in 13% and 34% of isolates, respectively; other genes were not detected. Most Staphylococcus strains with mphC had nearly identical alleles, but one strain was highly divergent (7.7%). The identical alleles were observed in diverse Staphylococci species. Three moderately divergent lnuA alleles were uncovered in our samples that corresponded to lnuA lineages known worldwide. Combined analysis of our data and Genbank data revealed that European farms harbored the highest lnuA diversity, probably a result of regular use of lincosamide antibiotics. The worldwide distribution of lnuA and mphC alleles suggests high gene flow, whereas their occurrence in diverse bacteria species indicates extensive horizontal gene transfer. The high incidence of lnuA and mphC genes in Southern California far from agricultural areas suggests that the natural environment is important in accumulating, harboring, and reshuffling antibiotic resistant genes, resulting in new combinations that may later emerge in clinical settings.