Molecular detection of DHA-1 AmpC beta-lactamase gene in Enterobacteriaceae clinical isolates in Indonesia
B. Diela
Faculty of Medicine, Universitas Padjadjaran, Bandung, Indonesia
S. Sudigdoadi,A.I. Cahyadi,B.A.P. Wilopo & I.M.W. Dewi
Department of Microbiology and Parasitology, Faculty of Medicine, Universitas Padjadjaran, Bandung, Indonesia
C.B. Kartasasmita
Department of Pediatrics, Faculty of Medicine, Universitas Padjadjaran, Bandung, Indonesia Dr. Hasan Sadikin Hospital, Bandung, Indonesia
ABSTRACT: Dhahran (DHA)-1 is an inducible plasmid-mediated AmpC beta-lactamase gene, which was reported as the most frequent cause of escalating morbidity and mortality rate among patients with infectious diseases. The aim of this study was to determine the prevalence of blaDHA-1 gene in Enterobacteriaceae clinical isolates in Indonesia. A total of 85 Enterobacteriaceae clinical isolates, including E. coli, Klebsiella. pneumoniae, E. cloacae, K. oxytoca, E. aerogenes, and Proteus mirabilis, were included in this study. The samples were collected from several private hospitals and clinical laboratories in Bandung, Indonesia, during a period between July 2014 and April 2015. The molecular detection of blaDHA-1 gene was carried out by PCR assay. We found that 32.9% of Enterobacteriaceae clinical isolates carried blaDHA-1 gene, which was predominantly found in K. pneumoniae (75%) followed by K. oxytoca (50%), E. cloacae (28.6%), and E.coli (14%). These results revealed a higher frequency of blaDHA-1 gene detected in Enterobacteriaceae clinical isolates in Indonesia compared with those in surveillance studies conducted worldwide. To our knowledge, this is the first molecular epidemiology report from Indonesia that showed the high prevalence of blaDHA-1 gene in Enterobacteriaceae clinical isolates.
Keywords: AmpC Beta-Lactamase; DHA-1; Enterobacteriaceae; PCR; Indonesia
1 INTRODUCTION
Inadequate regulation of antibiotic therapy for many infectious diseases in most Asian countries, including Indonesia, may increase resistance spectrum of gram-negative bacteria to beta-lactam antibiotics.4 With the increasing use of beta-lactam antibiotics and various inhibitor combinations, such as amoxicillin-clavulanic acid or sulbactam, production of AmpC beta-lactamase enzyme by gram-negative bacteria have emerged.4 This enzyme can hydrolyze and inactivate the third generation of beta-lactam antibiotics, including oxyimino-cephalosporins (cefotaxime, ceftazidime, and ceftriaxone), monobactam (aztreonam), and cephamycins (cefoxitin and cefotetan).4 AmpC beta-lactamase enzyme has been mainly detected in Enterobacteriaceae family of gram-negative bacteria and frequently causes severe infection cases in hospitalized patients.4 This enzyme is poorly inhibited by many common beta-lactamase inhibitors, such as clavulanic acid and sulbactam, but can only be inhibited by AmpC inhibitors, such as cloxacillin or 3-aminophenylboronic acid.2,3
Detection of AmpC beta-lactamase enzyme is important to improve the clinical treatment for patients with infection due to Enterobacteriaceae. Recently, several phenotypic tests for detection of this enzyme are being developed with varying degrees of success, such as AmpC Disk Test, 3-Aminophenylboronic Acid Disk Test, and Three-Dimensional Test.5,6 However, there is no specific phenotypic test to confirm the presence of AmpC beta-lactamases in clinical isolates which has been validated by Clinical Laboratory Standards Institute (CLSI).4 Therefore, there is a need to conduct an examination using PCR (Polymerase Chain Reaction) as the gold standard method to detect the presence of AmpC beta-lactamase gene in Enterobacteriaceae clinical isolates.2,7
The AmpC beta-lactamase gene (blaAmpC) consists of 6 families: ACC, FOX, MOX, DHA, CIT and EBC. These are encoded either in chromosome or plasmid.3,8 The expression of blaAmpC chromosomal gene can be triggered by the presence of beta-lactam antibiotics, especially cefoxitin.3,7 The plasmid-mediated blaAmpC gene is derived from the blaAmpC chromosomal gene or can be transferred horizontally between plasmids of Enterobacteriaceae.3,5,9 DHA-1 is a subfamily of DHA, an inducible plasmid-mediated blaAmpC gene, which has been reported as the most frequent cause of escalating morbidity and mortality rate among infected patients compared with other families of plasmid-mediated blaAmpC gene.10,12 BlaDHA-1 gene was originated from the chromosomal blaAmpC gene of Morganella morganii, which the expression can be induced by the presence of beta-lactam antibiotics. Thus, the increasing use of beta-lactam antibiotics in many of infection cases may induce the expression of blaDHA-1 gene among Enterobacteriaceae clinical isolates.3,10,11
At present, there has not been any molecular epidemiological data in Indonesia that report the prevalence of blaDHA-1 gene in Enterobacteriaceae. Therefore, this study was designed to detect the presence of blaDHA-1 gene in Enterobacteriaceae clinical isolates in Indonesia by using PCR assay. The results will make health care providers to be more careful in administering antimicrobial therapy for infected patients to decrease the occurrence of antimicrobial resistance and the expansion of resistance spectrum of Enterobacteriaceae to beta-lactam antibiotics.
2 MATERIALS AND METHODS
2.1 Bacterial isolates
Ninety two Enterobacteriaceae clinical isolates were collected from several private hospitals and clinical laboratories in Bandung, Indonesia, during a period between Juli 2014 and April 2015.
These isolates were taken from patientās specimens, including blood, urine, abdominal pus, vaginal swab, etc. The organisms were grown on nutrient agar plates and biochemical tests were carried out to identify the bacterial species of the Enterobacteriaceae clinical isolates. Eighty five Enterobacteriaceae clinical isolates were included in this study, including Escherichia coli (n = 50), Klebsiella pneumoniae (n = 24), E. cloacae (n = 7), K. oxytoca (n = 2), E. aerogenes (n = 1), and Proteus mirabilis (n = 1). Seven unknown or non-specific isolates were, such as Klebsiella sp., Serratia sp., or rod-shaped gram-negative bacteria, were excluded from the study.
2.2 Plasmid DNA isolation
Plasmid DNA from Enterobacteriaceae clinical isolates were isolated using the Xprep Plasmid DNA Mini Kit (PhileKorea Technology Inc., Seoul, Korea) according to the manufacturerās instructions.
2.3 PCR amplification of blaDHA-1 gene
The oligonucleotide primers used for PCR assay were DHAM-forward (F) (5ā-AAC TTT CAC AGG TGT GCT GGG T-3ā) and DHAM-reverse (R) (5ā-CCG TAC GCA TAC TGG CTT TGC-3ā), which were designed by PĆ©rez-PĆ©rez FJ4 and synthesized by Integrated DNA Technology, Inc., Lowa, USA. Reactions were carried out in a MasterCycler Gradient⢠(Eppendorf Inc., Hamburg, Germany) in 12.5 μL of mixtures containing 6.25 μL of DreamTaq Green PCR Master Mix⢠(Thermo Fisher Scientific Inc., MA, USA), which consists of DreamTaq DNA polymerase, 2X DreamTaq Green Buffer, dNTPs, and 4 mM MgCl2; 0.125 μL of 10 μM DHAM-F Primer; 0.125 μL of 10 μM DHAM-R Primer; 5.5 μL of nuclease-free water; and 0.5 μL of isolated plasmid DNA.
The PCR condition used in this study was; 1 cycle of initial denaturation at 95°C for 2 minutes, followed by 30 cycles of 95°C for 30 seconds, 58°C for 1 minute and t72°C for 1 minute and then a final extension at 72°C for 10 minutes.
2.4 Electrophoresis
12 μL of PCR products were resolved on 1% agarose gels, which was made by 3 mg of TopVision⢠Agarose Gel (Thermo Fisher Scientific Inc., MA, USA). For negative control, 12 μL of PCR product without isolated plasmid DNA was added to the well. The ladder used containing 8 μL of nuclease-free water, 2 μL of loading dye, and 2 μL of GeneRuler⢠1kb molecular size DNA Ladder (Thermo Fisher Scientific Inc., MA, USA). The electrophoresis process runs at 80 V for 30 minutes using PowerPac⢠Basic Power Supply (Bio-Rad Laboratories, Inc., USA). The gel was then visualized with Ultraviolet Trans illuminator (UVDI, Major Science Inc., USA). The positive result of blaDHA-1 gene detection was shown by presence of 405 bp b...