Characterization of erythromycin-resistant methylase genes from multiple antibiotic resistant Staphylococcus spp isolated from milk samples of lactating cows.
OBJECTIVE
To isolate and characterize erythromycin-resistant methylase genes in multiple-antibiotic resistant staphylococci isolated from milk samples.


METHODS
300 lactating cows.


METHODS
23 erythromycin-resistant staphylococci were isolated from milk samples of 300 lactating cows. The prevalence of erythromycin-resistant methylase (erm) genes, ermC and ermA genes, and the multicomponent macrolide efflux pump in staphylococci msrA genes were identified and characterized by use of multiplex polymerase chain reaction (PCR), Southern hybridization, restricted fragment length polymorphism (RFLP) analysis, and dot-blot hybridization.


RESULTS
Biochemical characterization indicated that 3 of 23 (13%) isolates were coagulase-positive Staphylococcus aureus, and the rest were coagulase-negative. Multiplex PCR resulted in amplification of a 520-base pair (bp) region of the ermC gene from the cell lysates of a strain of S simulans M-21 and S sciuri M-28. The ermC gene in both isolates was found on a 3-kilobase plasmid. The ermA gene was found on the chromosome of 21 isolates, and 6 RFLP patterns were observed. None of the isolates harbored the msrA gene.


CONCLUSIONS
Erythromycin-resistant Staphylococcus spp isolated from milk samples of lactating cows may serve as reservoirs of erm genes homologous to those described in human isolates. However, the chromosomal insert patterns and prevalence of these genes, the sizes of plasmids harboring the genes, and the number of inserts of the genes (copy number) may differ from that of human isolates.
Khan
S A
SA
Division of Microbiology, The National Center for Toxicological Research, United States Food and Drug Administration, Jefferson, AR 72079, USA.
Nawaz
M S
MS
Khan
A A
AA
Steele
R S
RS
Cerniglia
C E
CE
D000818:Animals; D002417:Cattle / Q000235:genetics*; D003612:Dairying / Q000379:methods; D004352:Drug Resistance, Microbial / Q000235:genetics*; D018432:Drug Resistance, Multiple / Q000235:genetics*; D004917:Erythromycin; D005260:Female; D006801:Humans; D007774:Lactation; D008414:Mastitis, Bovine / Q000188:drug therapy / Q000382:microbiology; D008780:Methyltransferases / Q000235:genetics*; D008826:Microbial Sensitivity Tests; D008892:Milk / Q000382:microbiology*; D010957:Plasmids; D012150:Polymorphism, Restriction Fragment Length; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000662:veterinary; D013210:Staphylococcus / Q000187:drug effects / Q000201:enzymology / Q000235:genetics* / Q000302:isolation & purification
D004917:Erythromycin; D008780:Methyltransferases; C035181:rRNA (adenosine-O-2'-)methyltransferase