The mef(A) gene predominates among seven macrolide resistance genes identified in gram-negative strains representing 13 genera, isolated from healthy Portuguese children.
Of the 176 randomly selected, commensal, gram-negative bacteria isolated from healthy children with low exposure to antibiotics, 138 (78%) carried one or more of the seven macrolide resistance genes tested in this study. These isolates included 79 (91%) isolates from the oral cavity and 59 (66%) isolates from urine samples. The mef(A) gene, coding for an efflux protein, was found in 73 isolates (41%) and was the most frequently carried gene. The mef(A) gene could be transferred from the donors into a gram-positive E. faecalis recipient and a gram-negative Escherichia coli recipient. The erm(B) gene transferred and was maintained in the E. coli transconjugants but was found in 0 to 100% of the E. faecalis transconjugants tested, while the other five genes could be transferred only into the E. coli recipient. The individual macrolide resistance genes were identified in 3 to 12 new genera. Eight (10%) of the oral isolates and 30 (34%) of the urine isolates for which the MICs were 2 to >500 microg of erythromycin per ml did not hybridize with any of the seven genes and may carry novel macrolide resistance genes.
Department of Pathobiology, Box 357238, School of Public Health and Community Medicine, University of Washington, Seattle, WA 98195, USA.
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D001426:Bacterial Proteins / Q000235:genetics*; D002648:Child; D003227:Conjugation, Genetic / Q000235:genetics; D003470:Culture Media; D004269:DNA, Bacterial / Q000235:genetics; D024881:Drug Resistance, Bacterial; D004926:Escherichia coli / Q000235:genetics; D006090:Gram-Negative Bacteria / Q000187:drug effects / Q000235:genetics*; D006801:Humans; D018942:Macrolides / Q000494:pharmacology*; D008565:Membrane Proteins / Q000235:genetics*; D008826:Microbial Sensitivity Tests; D009055:Mouth / Q000382:microbiology; D011174:Portugal / Q000453:epidemiology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014556:Urine / Q000382:microbiology
D001426:Bacterial Proteins; D003470:Culture Media; D004269:DNA, Bacterial; D018942:Macrolides; C117866:MefA protein, Streptococcus; D008565:Membrane Proteins