Abstract

1. P 2029 Emergence of carbapenem resistant Acinetobacterbaumannii producing OXA-23 gene in a major Saudi Arabian hospitalsAbdulrahman. A. AlsultanKing Faisal University, College of Medicine, Department of Biomedical SciencesAlahsa 31982, Alhafouf P.O. Box 400 Kingdome of Saudi Arabia Materials and Methods Abstract • A total of 29 non-repetitive, strains collected between January 2011 and April 2011 from different specimens from King Faisal Specialist Hospital and Research Centre (KFSHRC) in Riyadh. All isolates were identified presumptively by the Vitek compact II system. The similarity of the genospecies group 1 (A. calcoaceticus), 2 (A. baumannii), 3 and 13TU makes the differentiation between them complex. Therefore, DNA groups 1, 2, 3, and 13TU are referred to as the A.calcoaceticus-A. baumannii complex. The 29 clinical isolates of A. baumannii were confirmed by the intrinsic gene of OXA-51-like b-lactamase by matching the appropriate size of 352bp. PCR was also used to identify the genes encoding the blaOXA-23. The MIC of antibiotics was determined by dilution test according to BSAC guidelines. • Bacterial isolates: 29 isolates of A. baumannii were collected from different specimens from King Faisal Specialist Hospital and Research Centre (KFSHRC) in Riyadh between January 2011 and April 2011. • Idintification: The identity of A. baumannii was done presumptively by the Vitek compact II system (5) and confirmed by the presence of blaOXA-51-Like allels (6). • Susceptibility testing: Minimum inhibitory concentration (MICs) were determined for imipenem, meropinem, Tigecycline and colistin (Table 1) based on the British Society for Antimicrobial Chemotherapy (BSAC) (7). • Polymerase chain reaction (PCR) for blaOXA-23, genes. Objectives: Acinetobacter baumannii is an important and opportunisticpathogen associated with immuno-compromised patients in intensive care units (ICUs) worldwide. The increase of carbapenem resistance in Acinetobacter baumannii is a global concern since it limits the range of therapeutic alternatives. Carbapenem resistance in Acinetobacter baumannii is largely manifested by class D β-lactamases,comprising OXA-23-like, OXA-40-like, OXA-51-likeand OXA-58-like β-lactamases. Some of these enzymes are able to hydrolyze carbapenems and responsible in multi-drug resistance. OXA-51-like β-lactamases are present in all isolates of A. baumanniiand carbapenem resistance has sometimes been associated with this gene. The emergence of MDR A. baumannii has been reported in several hospitals in Kingdom of Saudi Arabia, the aim of this work is to investigate the disseminations of carbapenem resistance in A. baumannii in a major Saudi Arabian hospital. Materials and Methods: A total of 29 non-repetitive, strains collected between January 2011 and April 2011 from different specimens from King Faisal Specialist Hospital and Research Centre (KFSHRC) in Riyadh. All isolates were identified presumptively by the Vitek compact II system. PCR was used to identify not only the intrinsic blaOXA-51-like gene but also the genes encoding the blaOXA-23. The MIC of antibiotics was determined by dilution test according to BSAC guidelines. Results: Twenty-nine clinical isolates were identified as A. baumannii by having the intrinsic of blaOXA-51-like gene. All isolates except one were resistant to imipenem (MIC > 16), three of which were highly resistant (MIC > 32mg/L). The sensitive strain had an MIC ≤ 1mg/L. All isolates were also resistant to meropenem, 25 of which had MICs > 32mg/L, two isolates had MICs = 16 mg/L. One strain was intermediate (MIC > 4 mg/L) and another sensitive (MIC MIC ≤ 0.5 mg/L). The OXA-23 β‑lactamase was the cause of imipenem and meropenem-resistance in 14 strains, which were resistant to carbapenems because they carried this gene of β-lactamase and no other; there was one strain harbouring the OXA-23 β‑lactamase which was sensitive to both carbapenems. Conclusion: The high level of multi-resistance in carbapenems in A. baumannii responsible for infection in those patients due to the dissimination of the OXA-23 β‑lactamases in this Saudi Arabian hospital. Results Introduction Acinetobacter baumannii has become an important pathogen emerged in the recent years associated with a range of infections causing a significant health problems particularly in immunocompromised patients (1). Carbapenems are often used as the last drugs for treating sever A. baumannii infections but are being compromised due to the emergence of β-lactamase and carbapenemase of molecular class B and D (2). OXA carbapenemases are more reported in Europe (3). Moreover the genes encoding OXA-23-like and OXA-51-like enzymes (4) have been found to be linked with the mobile element ISAba1, while the OXA-58-like encoding gene adjacent to ISAba2, ISAba3 and IS18 (3). • Twenty-nine isolates of A. baumannii-A.calcoaceticus complex were identified by Vitek II compact system as a presumptive identification of the genomic species possessing 14 different profiles (Table 2). • The 29 isolates of A. baumannii were confirmed by the intrinsic gene of OXA-51-like b-lactamase by matching the appropriate size of 352bp (Figure 1). • The allele encoding OXA-23-like enzymes was located on a 501bp fragment was detected in 14 clinical isolate (Figure 2). • Twenty-eight isolates were resistant to imipenem (MIC > 16mg/L) and twenty-seven of which were meropenem-resistant (MIC 16-32 mg/L) (Table 2). • Thirteen imipenem and meropenem-resistant isolates (MIC 16 - 64 mg/L) had blaOXA-23 gene. • One isolate was sensitive to imipenem, meropenem, colistin, tigecycline (MIC ≤ 0.5-1mg/L) had positive OXA-23(Table 2). • All isolates were sensitive to colistin and tigecycline except 4 were resistant and another 4 intermediate to tigecycline, only one isolate was intermediate to colistin. Aim The purpose of this study is to investigate the prevalence of carbapenem resistant in A. baumannii in Saudi Arabian hospital Conclusion References • The high level of multi-resistance in carbapenems in A. baumannii responsible for infection in patients due to the circulation of the OXA-23 β‑lactamases, in comparable numbers, in Saudi Arabian hospitals. • Furthermore, the emergence of tigecycline plus colistin resistance is causing a treatment shortfall for these patients. • Identification of A. baumannii using both phenotypic VITEK II and genotypic methods is very useful, especially in the presence of the intrinsic gene of OXA-51. • The gene encoding OXA-23-like has been shown to be connected with insertion sequence ISAba1. • Further investigation would be needed to verify the genome content in such isolates. 1.Steven J. Nigro and Ruth M. Hall. Tn6167, an antibiotic resistance island in an Australian carbapenem-resistant Acinetobacter baumannii GC2, ST92 isolate. J Antimicrob Chemother 2012; 10.1093. 2. Brown S, and S. Amyes. OXA β-lactamases in Acinetobacter: the story so far. J Antimicrob Chemother 2006; 57:1-3. 3. Turton J F, M E Ward, N Woodfordet al. The role of ISAba1 in expression of OXA carbapenemase genes in Acinetobacter baumannii. FEMS Microbiol Lett 2006; 258:72-7. 4. Ellington M J, J Kistler, D M Livermore et al. Multiplex PCR for rapid detection of genes encoding acquired metallo-beta-lactamases. J Antimicrob Chemother 2007; 59:321-2. 5.Thomask, K. Ling, and P. Tam, et al(2001).Evaluation of VITEK 2 rapid identification and susceptibility testing system against Gram-negative clinical isolates. Journal of Clinical Microbiology. vol. 39, No. 8, 2964-2966. 6. Woodford N, M J Ellington, J M Coelhoet al. Multiplex PCR for genes encoding prevalent OXA carbapenemases in Acinetobacter spp. Int J Antimicrob Agents 2006; 27:351-3. 7. Andrews J M. Determination of minimum inhibitory concentrations. J Antimicrob Chemother 2001; 48: 5-16. 8. A. Al-Sultan, A. Hamouda, B. A. Evans and S. G. B. Amyes (2009) Acinetobacter baumannii: the emergence of four strains with novel blaOXA-51- like genes in patients with diabetes mellitus. The Journal of Chemotherapy, 21, 290 - 295. Acknowledgments King Abdulaziz City for Science and Technology (KACST), King Faisal University (KFU), Professor Sebastian Amyes, Dr. Elsayed Aboemajd, Dr. Sahar Althawadi, Abdulqader Abouli, Hani Alrasasi, Hani Alfarhan, Hajar Aldohilan, Nof Alhomaini, Fatemah Alnajar.