Investigation of aminoglycoside modifying enzyme genes in methicillin-resistant staphylococci

Abstract

Methicillin-resistant staphylococci may also be resistant to some other antibiotics as well as beta-lactams. In this study, co-existence of resistance to methicillin and aminoglycosides was genetically investigated in staphylococci. A total of 50 staphylococci from in-patients, 17 Staphylococcus aureus and 33 coagulase negative staphylococci (CNS) that contained mecA (gene encoding PBP 2a, an altered penicillin-binding protein) determined by polymerase chain reaction (PCR) were included in the study. Aminoglycoside modifying enzyme (AME) genes were investigated using multiplex-PCR. Aminocyclitol-6'-acetyltransferase-aminocyclitol-2''-phosphotransferase [aac(6')/aph(2'')] gene (encoding bifunctional acetyltransferases/phosphotransferases) was determined in 66% of the isolates, aminocyclitol-4'-adenylytransferase (ant(4')-Ia) gene (encoding phosphotransferases) in 24%, and aminocyclitol-3'-phosphotransferase (aph(3')-IIIa) gene (encoding nucleotidyltransferases) in 8%. Two isolates contained all these three genes. Thirty-six (72%) isolates had at least one of these genes. Three CNS and one S. aureus isolates sensitive to oxacillin had the mecA gene. In conclusion, a high rate of aminoglycoside resistance was determined in methicillin-resistant staphylococci. The aac(6')/aph(2'') was the most frequently detected.

Molecular Characterization and Resistance Profile of Methicillin Resistant Staphylococcus aureus Strains Isolated from Hospitalized Patients in Intensive Care Unit, Tehran-Iran

“…These results are inconsistent with a previous study by Rahimi et al which reported that the prevalence of aac(6 )/aph(2 ) gene was higher than that of the two other AME genes, ant(4 )-Ia and aph(3 )-IIIa in MRSA isolates (23). Furthermore, the frequency rate of the ant(4')-Ia gene was higher than in the previous study performed in Iran (23) (42.2%), Japan (84.5%) (24) and Turkey (24%) (10). The rate of aph(3´)-IIIa gene in this study was 31.6%, which is in accordance with the results of a study in Iran by Rahimi (23), and was higher than Japan (8.9%) (24) and lower than Turkey (66%) (10).…”

“…All the strains were identified by standard microbiological procedures such as colony morphology, Gram staining, growth on mannitol salt agar and production of catalase, coagulase, and DNase. All the isolates were confirmed using polymerase chain reaction (PCR) for the femA and nucA genes (10,11). S. aureus isolates were stored in Tryptic Soy Broth (TSB; Merck, Germany) containing 20% glycerol at -70°C for further investigations.…”

“…The most commonly detected antibiotic resistance genes in clinical S. aureus strains are mecA (methicillin), ermA, ermB and ermC (macrolide, lincosamide, streptogramin B), mupA (mupirocin), msrA and msrB (macrolides), tet (tetracycline), ant(4´)-Ia, aac(6´)-Ie/aph(2˝), and aph(3´)-IIIa (AMEs, aminoglycoside modifying enzymes) (9)(10)(11)(12)(13)(14). MRSA strains are usually resistant to many antibiotics and may carry virulence factors that have a significant role in the pathogenicity of the diseases such as panton-valentine leukocidin (PVL), toxic shock syndrome toxin-1 (TST-1), and exfoliative toxins (eta, etb) (9,15,16).…”

Clonality, virulence and the occurrence of genes encoding antibiotic resistance among Staphylococcus warneri isolates from bloodstream infections

“…genes, PCR assays were performed as described by Geha et al (1994), Ardic et al (2006) and Le Bouter et al (2011).…”

“…The aac (6¢)/aph(2¢¢) genes that code for bifunctional enzymes, which inactivate a broad spectrum of aminoglycoside antibiotics, are located on transposon Tn4001. The aph(3¢)-IIIa gene codes for a phosphotransferase, which mediates resistance to kanamycin, neomycin and amikacin, naturally occurring on plasmids and in transposons (Ardic et al, 2006;Woegerbauer et al, 2014). The ant(4¢)-Ia gene codes for adenyltransferase, which covers resistance to kanamycin, neomycin and tobramycin and is located on plasmid pUB110 (Wendlandt et al, 2013).…”