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.
Subject(s)
Aminoglycosides/pharmacology , Methicillin Resistance/genetics , Staphylococcus/drug effects , Staphylococcus/enzymology , Acetyltransferases/chemistry , Acetyltransferases/genetics , Acetyltransferases/metabolism , Bacterial Proteins/genetics , DNA, Bacterial/chemistry , DNA, Bacterial/genetics , Genotype , Humans , Penicillin-Binding Proteins , Phosphotransferases (Alcohol Group Acceptor)/chemistry , Phosphotransferases (Alcohol Group Acceptor)/genetics , Phosphotransferases (Alcohol Group Acceptor)/metabolism , Polymerase Chain Reaction , Staphylococcal Infections/microbiology , Staphylococcus/genetics , Staphylococcus/growth & developmentABSTRACT
This study was conducted to investigate the presence of methicillin and aminoglycoside resistance encoding genes by multiplex-polymerase chain reaction (PCR) and by phenotypic methods in staphylococci isolated from inpatients' clinical specimens. The presence of aac(6')1aph(2"), aph(3')-IIIa and ant(4)-Ia genes encoding aminoglycoside modifying enzymes (AME) and mecA gene encoding methicillin resistance were genotypically investigated. A total of 19 S. aureus and 30 coagulase negative staphylococci (CNS) were tested. Thirty four (69.4%) of the isolates were found to be resistant to oxacillin with disk diffusion test, 33 (97%) of which were found to harbour mecA gene. The correspondance between oxacillin resistance and presence of mecA gene was found to be 100% in S. aureus isolates, while it was 95.7% in CNS. Twenty two (44.9%), 7 (14.3%) and 2 (4.1%) isolates were found to harbour aac(6')/aph(2"), aph(3')-IIIa and ant(4)-/a AME genes, respectively. At least one or more AME genes were detected in 72.7% of mecA positive isolates.
Subject(s)
Methicillin Resistance/genetics , Staphylococcal Infections/microbiology , Staphylococcus/genetics , Acetyltransferases/genetics , Aminoglycosides/pharmacology , Bacterial Proteins/genetics , Coagulase , DNA, Bacterial/isolation & purification , Humans , Kanamycin Kinase/genetics , Microbial Sensitivity Tests , Nucleotidyltransferases/genetics , Oxacillin/pharmacology , Penicillin-Binding Proteins , Phenotype , Phosphotransferases (Alcohol Group Acceptor)/genetics , Polymerase Chain Reaction , Staphylococcus/drug effects , Staphylococcus/enzymology , Staphylococcus/isolation & purificationABSTRACT
Automatized blood culture systems are used widely due to the characteristics such as lower contamination risks, shorter incubation periods and higher isolation rates. In this study, BACTEC 9050 (Becton Dickinson, Ireland) and BacT/ALERT 120 (Organon Teknika Corp, USA) systems were compared for the evaluation of blood cultures obtained from 222 hospitalized patients in intensive care units between September and December 2003. For this purpose, two blood samples obtained from each arms of patients, were inoculated into BACTEC plus aerobic/F (Becton Dickinson, Ireland) and BacT/ALERT FA/aerobic (BioMeriéux, USA) media, respectively, and incubated. The first bacterial growth time has been recorded for each system and the bacteria were identified by conventional methods. As a result, both of the systems detected bacterial growth in 42 (91.3%) of a total of 46 (20.7%) positive blood samples obtained from 222 patients. The distribution of microorganisms grown in BACTEC and BacT/ALERT were found as follows, respectively; 24 and 20 coagulase negative staphylococci, 8 and 8 Acinetobacter sp., 6 and 10 Escherichia coli, 1 and 1 Staphylococcus aureus, 1 and 1 Pseudomonas sp., 1 and 1 Klebsiella sp., 1 and 1 Candida sp. False positivity and false negativity were not observed in either of the systems. Positive results were obtained in an average time of 20.6 (7.5-35.5) hours and 22.49 (1.5-35.5) hours with BACTEC and BacT/ALERT, respectively. Since there was no statistically significant difference between the systems concerning bacterial isolation rates and periods (p=1.00), it may be concluded that both of these systems would be used in clinical microbiology laboratories for the evaluation of blood cultures.
