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Investigation of carbapenem-resistant Acinetobacter baumannii isolates in a district hospital in Taiwan
Available online at www.sciencedirect.com
Diagnostic Microbiology and Infectious Disease 63 (2009) 394 – 397 www.elsevier.com/locate/diagmicrobio
Notes
Investigation of carbapenem-resistant Acinetobacter baumannii isolates in a district hospital in Taiwan☆ Chih-Ming Chena,b , Po-Yen Liuc , Se-Chin Ked , Hwa-Jen Wue , Lii-Tzu Wuc,⁎ a
Division of Infectious Disease, Department of Internal Medicine, TungsT Taichung MetroHarbor Hospital, Taiwan b The Graduate Institute of Clinical Medical Science, China Medical University, Taiwan c The Institute of Medical Science and Department of Microbiology, China Medical University, 404 Taichung, Taiwan, R.O.C. d Infection control committee TungsT Taichung MetroHarbor Hospital, Taiwan e Department of Clinical Laboratory, Jen-Ai Hospital, Tali City, Taichung, Taiwan Received 31 July 2008; accepted 15 December 2008
Abstract A total of 34 Acinetobacter baumannii isolates from a district hospital in Taiwan were identified with carbapenem-hydrolyzing oxacillinase OXA-66/OXA-51-like. In addition, 26 of 28 carbapenem-resistant isolates harbored plasmid-encoded bla OXA-23-like genes. Twenty of 28 carbapenem-resistant isolates mapped to the major genotype cluster A of carbapenemase producer by pulsed-field gel electrophoresis. © 2009 Elsevier Inc. All rights reserved. Keywords: Acinetobacter baumannii; Carbapenem-hydrolyzing oxacillinase; Carbapenem resistant; OXA-66/OXA-51-like; bla
Acinetobacter baumannii is a cause of nosocomial infections worldwide. Recently, bloodstream infections with a high mortality rate and caused by multidrug-resistant A. baumannii (MDRAB) are becoming more prevalent (Cisneros et al., 1996; Sunenshine et al., 2007). Carbapenemase production is the most described mechanism of resistance to carbapenems. The carbapenemases in A. baumannii have belonged to the OXA-23-, OXA-24-, and OXA-58-type class D family of serine β-lactamases and IMP/VIM class B metallo-β-lactamase (Perez et al., 2007; Poirel and Nordmann, 2006). The most common carbapenemase gene in the Far East has been found in A. baumannii blaOXA-23 from Japan, Korea, and China (Jeon et al., 2005; Koh et al., 2007; Lim et al., 2007; Wang et al., 2007). The upstream of OXAtype class D carbapenemases in Acinetobacter is often associated with ISAba1 and may modulate the expression
☆
This work was supported in part by research grants CMU95-074 from China Medical University. ⁎ Corresponding author. Tel.: +886-4-22053366-2169; fax: +886-422053764. E-mail address: [email protected] (L.-T. Wu). 0732-8893/$ – see front matter © 2009 Elsevier Inc. All rights reserved. doi:10.1016/j.diagmicrobio.2008.12.011
OXA-23-like
genes
and transfer of OXA-type carbapenemase genes (Corvec et al., 2007; Heritier et al., 2006). Since 1998, the prevalence of MDRAB has risen from 0% to 15% in Taiwan (Chang et al., 2007; Hsueh et al., 2002; Kuo et al., 2004). Moreover, an OXA-66/OXA-51-like carbapenemase associated with resistance to imipenem in A. baumannii has been recovered from northern Taiwan (Hu et al., 2007). Recently, the frequency of carbapenem-resistant A. baumannii (CRAB) in our hospital has increased from 2.2% in 2002 to 29.6% in 2006 (unpublished data). However, the mechanism remains uncertain. The present study was conducted to determine the prevalence and types of carbapenemases among A. baumannii in the central part of Taiwan. Between January and September 2007, 34 nonrepetitive A. baumannii isolates from in-patients were identified by routine microbiologic methods, Phoenix Automated Microbiology System (BD Diagnostic Systems, Sparks, MD) and one-tube multiplex polymerase chain reaction (PCR) method (Chen et al., 2007). The sources of 34 isolates included sputum (12), urine (6), pus (8), central venous line tip (3), ascites (3), blood (1), and drainage tube (1). Most isolates were collected from intensive care units (56%, 19/34). The antibiotic susceptibility tests were performed by disk
C.-M. Chen et al. / Diagnostic Microbiology and Infectious Disease 63 (2009) 394–397
diffusion method and agar dilution method, according to the criteria of the Clinical and Laboratory Standards Institute (CLSI). Minimal inhibitory concentrations (MICs) for isolates were determined by the Phoenix Automated Microbiology System, and confirmed by E-test strips (AB BIODISK, Solna, Sweden). The susceptibilities of tigecycline and colistin were determined according to the criteria provided by U.S. FDA and CLSI. The β-lactamases of A. baumannii and standard strains were analyzed as previously described (Mathew et al., 1975) using their isoelectric points (pI's). Electroporation experiments were performed with A. baumannii 19606 as the recipient. Electrotransformants were selected on plates with ticarcillin (50 μg/mL). The primers used to amplify blaIMP, blaVIM, blaSIM-1 blaOXA-23-like, blaOXA-24-like, blaOXA-58-like, and blaOXA-51-like were described previously (Afzal-Shah et al., 2001; Ellington et al., 2007; Poirel et al., 2005; Turton et al., 2006b). PCR mapping experiments used combinations of the ISAba1 primers and reverse primers designed against the OXA-23-like, and OXA-51-like genes were carried out as described (Turton et al., 2006a).
395
Among 34 A. baumannii, 28 were carbapenem-resistant and also co-resistant to ceftazidime, cefepime, aztreonam, gentamicin, amikacin, ciprofloxacin, trimethoprim/sulfamethoxazole, piperacillin/tazobactam, and ampicillin/sulbactam. Imipenem MICs had a broader range of 8–64 μg/mL as determined by agar dilution method. The characteristics of 28 CRAB isolates were summarized in Table 1. These results showed that the CRAB isolates were resistant to a wide range of antimicrobials but remained susceptible to colistin (100%) and tigecycline (82.2%). Isoelectric focusing analysis and PCRs were performed on the 34 isolates for detection of the different β-lactamase genes. The blaOXA-51-like gene was detected in 100% (34/34) of the isolates. Sequencing of the entire blaOXA-51-like gene confirmed the presence of the blaOXA-66 gene (pI N9.0). The blaOXA-23-like genes were found in 26 isolates, with full sequence homology (100%) to OXA-23 gene (pI, 6.5). The OXA-24-like, OXA-58-like, SIM-1, IMP-type, or VIM-type genes were not detected in any of the 34 isolates (Table 1). PCR mapping yielded a band of ca. 1.5 kb, indicating that ISAba1 was associated with the intrinsic blaOXA-51-like
Table 1 Demographic and characteristics of OXA-23-like and OXA-51-like of 28 carbapenem-resistant A. baumannii isolates Strain no.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
Collection ward Month
Unit
May 07 Jun 07 Feb 07 Mar 07 Apr 07 Aug 07 Jul 07 Jun 07 Sep 07 Aug 07 Apr 07 Jun 07 Feb 07 Sep 07 Aug 07 Apr 07 Jan 07 Jan 07 Dec 06 Feb 07 Mar 07 Jun 07 Apr 07 Jun 07 Apr 07 Sep 07 Mar 07 Mar 07
ICU ICU General ICU ICU ICU General General ICU ICU ICU ICU RCW ICU General General ICU ER RCW ICU ICU General ICU ICU ICU General OPD RCW
Specimen
MICs (mg/L) a
Tip Sputum Sputum Sputum Pus Ascites Sputum Urine Sputum Ascites Sputum Tube Blood Sputum Pus Urine Tip Urine Urine Sputum Pus Urine Sputum Sputum Pus Sputum Pus Urine
PFGE b
c
a
TZP
IPM
TGC
CS
Group
Subgroup
N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4
64 64 64 64 64 64 64 16 8 32 32 64 32 8 32 32 64 32 64 32 32 32 16 16 32 32 32 32
4 16 1 2 2 1 2 2 1 2 4 2 1 1 0.5 1 1 4 4 2 2 2 2 2 2 1 1 0.5
1 ≤0.5 ≤0.5 ≤0.5 ≤0.5 1 ≤0.5 ≤0.5 1 ≤0.5 ≤0.5 ≤0.5 ≤0.5 ≤0.5 ≤0.5 ≤0.5 ≤0.5 ≤0.5 1 ≤0.5 ≤0.5 ≤0.5 ≤0.5 ≤0.5 ≤0.5 ≤0.5 ≤0.5 ≤0.5
A A A A A A A A A A A A A A A A A A A A B B B B B C D D
A1 A1 A1 A2 A2 A3 A4 A5 A6 A7 A8 A9 A9 A9 A9 A10 A11 A11 A11 A12 B B B B B C D1 D2
OXA-23-liked
OXA-51-liked
+ + + + + + + + − + + + + − + + + + + + + + + + + + + +
+ + + + + + + + + + + + + + + + + + + + + + + + + + + +
TZP = piperacillin/tazobactam; IPM = imipenem; TGC = tigecycline; CS = colistin; ICU = intensive care unit; OPD = out-patient department; RCW = respiratory-care ward. a Determined by Phoenix Automated Microbiology System (BD Diagnostic Systems). b Determined by agar-dilution method. c Determined by E-test strips. d + = detection of DNA; − = no detection of DNA.
396
C.-M. Chen et al. / Diagnostic Microbiology and Infectious Disease 63 (2009) 394–397
alleles. All of 26 isolates with blaOXA-23-like, except isolate no. 27, produced a PCR amplicon of ca. 1.8 kb with use of the ISAba1 forward primer and the blaOXA-23-like reverse primer. The 2 CRAB isolates (nos. 9 and 14) without blaOXA-23-like fragment had a low MIC of 8 μg/mL for imipenem. Electroporation experiments were used to locate the βlactamase gene on the plasmid. Only the transformants from 26 isolates with blaOXA-23-like genes expressed β-lactamase OXA-23. No additional resistance marker was identified by routine antibiograms performed with the transformants and the same antibiotics as for the parental strains. The results suggested that ISAba1/blaOXA-23-like and ISAba1/blaOXA-51-like genes were widespread in A. baumannii in our hospital. In contrast with a previous study (Zong et al., 2008), all of our isolates had the ISAba1 upstream of the blaOXA-51-like gene, similar to Taiwan (Hu et al., 2007). The effect of A. baumannii with both ISAba1/blaOXA-51-like and ISAba1/blaOXA-23-like on carbapenem MICs had not been well investigated. This initial report describes 2 class D carbapenemases, OXA-23-like and OXA-51-like enzymes, that contribute to imipenem resistance in clinical strains of A. baumannii isolated from Taiwan. Genotyping of 28 CRAB strains was conducted by pulsedfield gel electrophoresis (PFGE) with AscI-digested. PFGE patterns were compared using standard published criteria (Tenover et al., 1995). PFGE analysis of these 28 isolates revealed 16 distinct genotypes that were classified into 4 clusters (A–D). The results were summarized in Table 1. Cluster A had 20 isolates, cluster B 5 isolates, cluster C 1 isolate, and cluster D 2 isolates. In conclusion, the present study suggested that an epidemiologic strain of cluster A A. baumannii was spreading in our hospital. The OXA-23-like gene was identified as the most prevalent carbapenemases among CRAB isolated from our hospital. The ISAba1 was not only associated with blaOXA-23-like but also with the blaOXA-51-like. This 1st report of CRAB with OXA-23-like gene in Taiwan suggests the importance of identifying and tracing resistant pathogens and the notification of carbapenem-resistant Acinetobacter spp. infection in Taiwan. Acknowledgments We wish to thank Chien-Shun Chiou of the 3rd branch office of Centers for Diseases Control of Taiwan for his assistance in PFGE analysis and Pi-Teh Huang for editing the manuscript. References Afzal-Shah M, Woodford N, Livermore DM (2001) Characterization of OXA-25, OXA-26, and OXA-27, molecular class D beta-lactamases associated with carbapenem resistance in clinical isolates of Acinetobacter baumannii. Antimicrob Agents Chemother 45:583–588. Chang PY, Hsueh PR, Wu PS, Chan PC, Yang TT, Lu CY, Chang LY, Chen JM, Lee PI, Lee CY, Huang LM (2007) Multidrug-resistant Acineto-
bacter baumannii isolates in pediatric patients of a university hospital in Taiwan. J Microbiol Immunol Infect 40:406–410. Chen TL, Siu LK, Wu RC, Shaio MF, Huang LY, Fung CP, Lee CM, Cho WL (2007) Comparison of one-tube multiplex PCR, automated ribotyping and intergenic spacer (ITS) sequencing for rapid identification of Acinetobacter baumannii. Clin Microbiol Infect 13: 801–806. Cisneros JM, Reyes MJ, Pachon J, Becerril B, Caballero FJ, GarciaGarmendia JL, Ortiz C, Cobacho AR (1996) Bacteremia due to Acinetobacter baumannii: epidemiology, clinical findings, and prognostic features. Clin Infect Dis 22:1026–1032. Corvec S, Poirel L, Naas T, Drugeon H, Nordmann P (2007) Genetics and expression of the carbapenem-hydrolyzing oxacillinase gene blaOXA-23 in Acinetobacter baumannii. Antimicrob Agents Chemother 51: 1530–1533. Ellington MJ, Kistler J, Livermore DM, Woodford N (2007) Multiplex PCR for rapid detection of genes encoding acquired metallo-beta-lactamases. J Antimicrob Chemother 59:321–322. Heritier C, Poirel L, Nordmann P (2006) Cephalosporinase over-expression resulting from insertion of ISAba1 in Acinetobacter baumannii. Clin Microbiol Infect 12:123–130. Hsueh PR, Teng LJ, Chen CY, Chen WH, Yu CJ, Ho SW, Luh KT (2002) Pandrug-resistant Acinetobacter baumannii causing nosocomial infections in a university hospital, Taiwan. Emerg Infect Dis 8:827–832. Hu WS, Yao SM, Fung CP, Hsieh YP, Liu CP, Lin JF (2007) An OXA-66/ OXA-51-like carbapenemase and possibly an efflux pump are associated with resistance to imipenem in Acinetobacter baumannii. Antimicrob Agents Chemother 51:3844–3852. Jeon BC, Jeong SH, Bae IK, Kwon SB, Lee K, Young D, Lee JH, Song JS, Lee SH (2005) Investigation of a nosocomial outbreak of imipenemresistant Acinetobacter baumannii producing the OXA-23 betalactamase in Korea. J Clin Microbiol 43:2241–2245. Koh TH, Sng LH, Wang GC, Hsu LY, Zhao Y (2007) IMP-4 and OXA betalactamases in Acinetobacter baumannii from Singapore. J Antimicrob Chemother 59:627–632. Kuo LC, Teng LJ, Yu CJ, Ho SW, Hsueh PR (2004) Dissemination of a clone of unusual phenotype of pandrug-resistant Acinetobacter baumannii at a university hospital in Taiwan. J Clin Microbiol 42:1759–1763. Lim YM, Shin KS, Kim J (2007) Distinct antimicrobial resistance patterns and antimicrobial resistance-harboring genes according to genomic species of Acinetobacter isolates. J Clin Microbiol 45:902–905. Mathew A, Harris AM, Marshall MJ, Ross GW (1975) The use of analytical isoelectric focusing for detection and identification of beta-lactamases. J Gen Microbiol 88:169–178. Perez F, Hujer AM, Hujer KM, Decker BK, Rather PN, Bonomo RA (2007) Global challenge of multidrug-resistant Acinetobacter baumannii. Antimicrob Agents Chemother 51:3471–3484. Poirel L, Nordmann P (2006) Carbapenem resistance in Acinetobacter baumannii: mechanisms and epidemiology. Clin Microbiol Infect 12: 826–836. Poirel L, Marque S, Heritier C, Segonds C, Chabanon G, Nordmann P (2005) OXA-58, a novel class D {beta}-lactamase involved in resistance to carbapenems in Acinetobacter baumannii. Antimicrob Agents Chemother 49:202–208. Sunenshine RH, Wright MO, Maragakis LL, Harris AD, Song X, Hebden J, Cosgrove SE, Anderson A, Carnell J, Jernigan DB, Kleinbaum DG, Perl TM, Standiford HC, Srinivasan A (2007) Multidrug-resistant Acinetobacter infection mortality rate and length of hospitalization. Emerg Infect Dis 13:97–103. Tenover FC, Arbeit RD, Goering RV, Mickelsen PA, Murray BE, Persing DH, Swaminathan B (1995) Interpreting chromosomal DNA restriction patterns produced by pulsed-field gel electrophoresis: criteria for bacterial strain typing. J Clin Microbiol 33:2233–2239. Turton JF, Ward ME, Woodford N, Kaufmann ME, Pike R, Livermore DM, Pitt TL (2006a) The role of ISAba1 in expression of OXA carbapenemase genes in Acinetobacter baumannii. FEMS Microbiol Lett 258: 72–77.
C.-M. Chen et al. / Diagnostic Microbiology and Infectious Disease 63 (2009) 394–397 Turton JF, Woodford N, Glover J, Yarde S, Kaufmann ME, Pitt TL (2006b) Identification of Acinetobacter baumannii by detection of the blaOXA-51-like carbapenemase gene intrinsic to this species. J Clin Microbiol 44:2974–2976. Wang H, Guo P, Sun H, Yang Q, Chen M, Xu Y, Zhu Y (2007) Molecular epidemiology of clinical isolates of carbapenem-resistant Acinetobacter
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spp. from. Chinese. hospitals. Antimicrob Agents Chemother 51: 4022–4028. Zong Z, Lu X, Valenzuela JK, Partridge SR, Iredell J (2008) An outbreak of carbapenem-resistant Acinetobacter baumannii producing OXA-23 carbapenemase in western China. Int J Antimicrob Agents 31:50–54.
Diagnostic Microbiology and Infectious Disease 63 (2009) 394 – 397 www.elsevier.com/locate/diagmicrobio
Notes
Investigation of carbapenem-resistant Acinetobacter baumannii isolates in a district hospital in Taiwan☆ Chih-Ming Chena,b , Po-Yen Liuc , Se-Chin Ked , Hwa-Jen Wue , Lii-Tzu Wuc,⁎ a
Division of Infectious Disease, Department of Internal Medicine, TungsT Taichung MetroHarbor Hospital, Taiwan b The Graduate Institute of Clinical Medical Science, China Medical University, Taiwan c The Institute of Medical Science and Department of Microbiology, China Medical University, 404 Taichung, Taiwan, R.O.C. d Infection control committee TungsT Taichung MetroHarbor Hospital, Taiwan e Department of Clinical Laboratory, Jen-Ai Hospital, Tali City, Taichung, Taiwan Received 31 July 2008; accepted 15 December 2008
Abstract A total of 34 Acinetobacter baumannii isolates from a district hospital in Taiwan were identified with carbapenem-hydrolyzing oxacillinase OXA-66/OXA-51-like. In addition, 26 of 28 carbapenem-resistant isolates harbored plasmid-encoded bla OXA-23-like genes. Twenty of 28 carbapenem-resistant isolates mapped to the major genotype cluster A of carbapenemase producer by pulsed-field gel electrophoresis. © 2009 Elsevier Inc. All rights reserved. Keywords: Acinetobacter baumannii; Carbapenem-hydrolyzing oxacillinase; Carbapenem resistant; OXA-66/OXA-51-like; bla
Acinetobacter baumannii is a cause of nosocomial infections worldwide. Recently, bloodstream infections with a high mortality rate and caused by multidrug-resistant A. baumannii (MDRAB) are becoming more prevalent (Cisneros et al., 1996; Sunenshine et al., 2007). Carbapenemase production is the most described mechanism of resistance to carbapenems. The carbapenemases in A. baumannii have belonged to the OXA-23-, OXA-24-, and OXA-58-type class D family of serine β-lactamases and IMP/VIM class B metallo-β-lactamase (Perez et al., 2007; Poirel and Nordmann, 2006). The most common carbapenemase gene in the Far East has been found in A. baumannii blaOXA-23 from Japan, Korea, and China (Jeon et al., 2005; Koh et al., 2007; Lim et al., 2007; Wang et al., 2007). The upstream of OXAtype class D carbapenemases in Acinetobacter is often associated with ISAba1 and may modulate the expression
☆
This work was supported in part by research grants CMU95-074 from China Medical University. ⁎ Corresponding author. Tel.: +886-4-22053366-2169; fax: +886-422053764. E-mail address: [email protected] (L.-T. Wu). 0732-8893/$ – see front matter © 2009 Elsevier Inc. All rights reserved. doi:10.1016/j.diagmicrobio.2008.12.011
OXA-23-like
genes
and transfer of OXA-type carbapenemase genes (Corvec et al., 2007; Heritier et al., 2006). Since 1998, the prevalence of MDRAB has risen from 0% to 15% in Taiwan (Chang et al., 2007; Hsueh et al., 2002; Kuo et al., 2004). Moreover, an OXA-66/OXA-51-like carbapenemase associated with resistance to imipenem in A. baumannii has been recovered from northern Taiwan (Hu et al., 2007). Recently, the frequency of carbapenem-resistant A. baumannii (CRAB) in our hospital has increased from 2.2% in 2002 to 29.6% in 2006 (unpublished data). However, the mechanism remains uncertain. The present study was conducted to determine the prevalence and types of carbapenemases among A. baumannii in the central part of Taiwan. Between January and September 2007, 34 nonrepetitive A. baumannii isolates from in-patients were identified by routine microbiologic methods, Phoenix Automated Microbiology System (BD Diagnostic Systems, Sparks, MD) and one-tube multiplex polymerase chain reaction (PCR) method (Chen et al., 2007). The sources of 34 isolates included sputum (12), urine (6), pus (8), central venous line tip (3), ascites (3), blood (1), and drainage tube (1). Most isolates were collected from intensive care units (56%, 19/34). The antibiotic susceptibility tests were performed by disk
C.-M. Chen et al. / Diagnostic Microbiology and Infectious Disease 63 (2009) 394–397
diffusion method and agar dilution method, according to the criteria of the Clinical and Laboratory Standards Institute (CLSI). Minimal inhibitory concentrations (MICs) for isolates were determined by the Phoenix Automated Microbiology System, and confirmed by E-test strips (AB BIODISK, Solna, Sweden). The susceptibilities of tigecycline and colistin were determined according to the criteria provided by U.S. FDA and CLSI. The β-lactamases of A. baumannii and standard strains were analyzed as previously described (Mathew et al., 1975) using their isoelectric points (pI's). Electroporation experiments were performed with A. baumannii 19606 as the recipient. Electrotransformants were selected on plates with ticarcillin (50 μg/mL). The primers used to amplify blaIMP, blaVIM, blaSIM-1 blaOXA-23-like, blaOXA-24-like, blaOXA-58-like, and blaOXA-51-like were described previously (Afzal-Shah et al., 2001; Ellington et al., 2007; Poirel et al., 2005; Turton et al., 2006b). PCR mapping experiments used combinations of the ISAba1 primers and reverse primers designed against the OXA-23-like, and OXA-51-like genes were carried out as described (Turton et al., 2006a).
395
Among 34 A. baumannii, 28 were carbapenem-resistant and also co-resistant to ceftazidime, cefepime, aztreonam, gentamicin, amikacin, ciprofloxacin, trimethoprim/sulfamethoxazole, piperacillin/tazobactam, and ampicillin/sulbactam. Imipenem MICs had a broader range of 8–64 μg/mL as determined by agar dilution method. The characteristics of 28 CRAB isolates were summarized in Table 1. These results showed that the CRAB isolates were resistant to a wide range of antimicrobials but remained susceptible to colistin (100%) and tigecycline (82.2%). Isoelectric focusing analysis and PCRs were performed on the 34 isolates for detection of the different β-lactamase genes. The blaOXA-51-like gene was detected in 100% (34/34) of the isolates. Sequencing of the entire blaOXA-51-like gene confirmed the presence of the blaOXA-66 gene (pI N9.0). The blaOXA-23-like genes were found in 26 isolates, with full sequence homology (100%) to OXA-23 gene (pI, 6.5). The OXA-24-like, OXA-58-like, SIM-1, IMP-type, or VIM-type genes were not detected in any of the 34 isolates (Table 1). PCR mapping yielded a band of ca. 1.5 kb, indicating that ISAba1 was associated with the intrinsic blaOXA-51-like
Table 1 Demographic and characteristics of OXA-23-like and OXA-51-like of 28 carbapenem-resistant A. baumannii isolates Strain no.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
Collection ward Month
Unit
May 07 Jun 07 Feb 07 Mar 07 Apr 07 Aug 07 Jul 07 Jun 07 Sep 07 Aug 07 Apr 07 Jun 07 Feb 07 Sep 07 Aug 07 Apr 07 Jan 07 Jan 07 Dec 06 Feb 07 Mar 07 Jun 07 Apr 07 Jun 07 Apr 07 Sep 07 Mar 07 Mar 07
ICU ICU General ICU ICU ICU General General ICU ICU ICU ICU RCW ICU General General ICU ER RCW ICU ICU General ICU ICU ICU General OPD RCW
Specimen
MICs (mg/L) a
Tip Sputum Sputum Sputum Pus Ascites Sputum Urine Sputum Ascites Sputum Tube Blood Sputum Pus Urine Tip Urine Urine Sputum Pus Urine Sputum Sputum Pus Sputum Pus Urine
PFGE b
c
a
TZP
IPM
TGC
CS
Group
Subgroup
N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4 N64/4
64 64 64 64 64 64 64 16 8 32 32 64 32 8 32 32 64 32 64 32 32 32 16 16 32 32 32 32
4 16 1 2 2 1 2 2 1 2 4 2 1 1 0.5 1 1 4 4 2 2 2 2 2 2 1 1 0.5
1 ≤0.5 ≤0.5 ≤0.5 ≤0.5 1 ≤0.5 ≤0.5 1 ≤0.5 ≤0.5 ≤0.5 ≤0.5 ≤0.5 ≤0.5 ≤0.5 ≤0.5 ≤0.5 1 ≤0.5 ≤0.5 ≤0.5 ≤0.5 ≤0.5 ≤0.5 ≤0.5 ≤0.5 ≤0.5
A A A A A A A A A A A A A A A A A A A A B B B B B C D D
A1 A1 A1 A2 A2 A3 A4 A5 A6 A7 A8 A9 A9 A9 A9 A10 A11 A11 A11 A12 B B B B B C D1 D2
OXA-23-liked
OXA-51-liked
+ + + + + + + + − + + + + − + + + + + + + + + + + + + +
+ + + + + + + + + + + + + + + + + + + + + + + + + + + +
TZP = piperacillin/tazobactam; IPM = imipenem; TGC = tigecycline; CS = colistin; ICU = intensive care unit; OPD = out-patient department; RCW = respiratory-care ward. a Determined by Phoenix Automated Microbiology System (BD Diagnostic Systems). b Determined by agar-dilution method. c Determined by E-test strips. d + = detection of DNA; − = no detection of DNA.
396
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alleles. All of 26 isolates with blaOXA-23-like, except isolate no. 27, produced a PCR amplicon of ca. 1.8 kb with use of the ISAba1 forward primer and the blaOXA-23-like reverse primer. The 2 CRAB isolates (nos. 9 and 14) without blaOXA-23-like fragment had a low MIC of 8 μg/mL for imipenem. Electroporation experiments were used to locate the βlactamase gene on the plasmid. Only the transformants from 26 isolates with blaOXA-23-like genes expressed β-lactamase OXA-23. No additional resistance marker was identified by routine antibiograms performed with the transformants and the same antibiotics as for the parental strains. The results suggested that ISAba1/blaOXA-23-like and ISAba1/blaOXA-51-like genes were widespread in A. baumannii in our hospital. In contrast with a previous study (Zong et al., 2008), all of our isolates had the ISAba1 upstream of the blaOXA-51-like gene, similar to Taiwan (Hu et al., 2007). The effect of A. baumannii with both ISAba1/blaOXA-51-like and ISAba1/blaOXA-23-like on carbapenem MICs had not been well investigated. This initial report describes 2 class D carbapenemases, OXA-23-like and OXA-51-like enzymes, that contribute to imipenem resistance in clinical strains of A. baumannii isolated from Taiwan. Genotyping of 28 CRAB strains was conducted by pulsedfield gel electrophoresis (PFGE) with AscI-digested. PFGE patterns were compared using standard published criteria (Tenover et al., 1995). PFGE analysis of these 28 isolates revealed 16 distinct genotypes that were classified into 4 clusters (A–D). The results were summarized in Table 1. Cluster A had 20 isolates, cluster B 5 isolates, cluster C 1 isolate, and cluster D 2 isolates. In conclusion, the present study suggested that an epidemiologic strain of cluster A A. baumannii was spreading in our hospital. The OXA-23-like gene was identified as the most prevalent carbapenemases among CRAB isolated from our hospital. The ISAba1 was not only associated with blaOXA-23-like but also with the blaOXA-51-like. This 1st report of CRAB with OXA-23-like gene in Taiwan suggests the importance of identifying and tracing resistant pathogens and the notification of carbapenem-resistant Acinetobacter spp. infection in Taiwan. Acknowledgments We wish to thank Chien-Shun Chiou of the 3rd branch office of Centers for Diseases Control of Taiwan for his assistance in PFGE analysis and Pi-Teh Huang for editing the manuscript. References Afzal-Shah M, Woodford N, Livermore DM (2001) Characterization of OXA-25, OXA-26, and OXA-27, molecular class D beta-lactamases associated with carbapenem resistance in clinical isolates of Acinetobacter baumannii. Antimicrob Agents Chemother 45:583–588. Chang PY, Hsueh PR, Wu PS, Chan PC, Yang TT, Lu CY, Chang LY, Chen JM, Lee PI, Lee CY, Huang LM (2007) Multidrug-resistant Acineto-
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