Clinical Carbapenem-Resistant Acinetobacter baylyi Strain Coharboring bla _SIM-1 and bla _OXA-23 from China

Abstract

bla SIM-1 and bla OXA-23 were codetected in clinical carbapenem-resistant Acinetobacter baylyi strain NB09A30. Both of carbapenemase genes were located on a large plasmid (ca. 360 kb). bla SIM-1 was found as a gene cassette inserted into a class 1 integron identical to that determined in Acinetobacter sp. isolates from South Korea. The genetic structure of bla OXA-23 in NB09A30 was different from that in the prevalent Acinetobacter baumannii of clonal complex 92 (CC92) from the same hospital.Carbapenem-resistant Acinetobacter spp. are one of the most frightening threats in the current antibiotic era (14). The mechanisms of Acinetobacter sp. resistance to carbapenem are production of carbapenemases (the main mechanism), overexpression of efflux pumps, and reduced expression or loss of outer membrane proteins (8). The metallo-␤-lactamase (MBL) gene, bla SIM-1 , was first identified in Acinetobacter spp. from South Korea in 2005 (11) and then in Acinetobacter genomic species 10 from two hospitals of South Korea in 2010 (10) but, as far as we know, has not yet been detected in other countries. Here, we report the emergence of Acinetobacter baylyi coharboring bla SIM-1 and bla in China.A 59-year-old male was admitted for cerebral hemorrhage at the Affiliated Hospital of Ningbo University in June 2009. After surgery to remove the intracerebral hematoma, he was transferred to the intensive care unit and received antibiotic therapy with cefminox, which was later replaced with cefodizime plus amikacin. Imipenem-resistant Acinetobacter sp. NB09A30 was isolated from the cloudy secretion of the surgical incision 10 days after the operation. MICs were determined by Etest and interpreted according to the CLSI 2011 recommendation (7). The strain was resistant to almost all ␤-lactams, including imipenem (MIC Ն 32 g/ml) and meropenem (MIC Ն 32 g/ml), but remained susceptible to minocycline, tigecycline, ciprofloxacin, levofloxacin, and colistin. The MICs of gentamicin and amikacin were Ն256 g/ml and 16 g/ml, respectively. Etest MBL strip testing against NB09A30 indicated the presence of metallo-␤-lactamase (imipenem/imipenem plus EDTA MIC of Ͼ16 g/ml). Surgical site infection was suspected, and the antibiotic regimen was changed to levofloxacin. The man was cured finally, and NB09A30 was no longer recovered.PCR detection of the bla OXA-51 -like gene in NB09A30 was negative, implying that NB09A30 is not an Acinetobacter baumannii strain (15). The 16S-23S rRNA intergenic spacer region (ISR) of NB09A30 was amplified and cloned into the pGEM-T Easy vector for sequencing (5). This showed that NB09A30 possessed ISRs with different lengths (long ISR, 650 bp; short ISR, 611 bp), a unique organization of the 16S-23S rRNA ISRs of A. baylyi (12). The ISR sequences were 94% identical to those of A. baylyi strain 93A2 (GenBank accession no. EU042163) and A. baylyi ADP1 (GenBank accession no. CR543861); they were less than 85% identical to those of the other genomic species, which indicated that NB09A30 is an A. baylyi strain (12). PCR was p...

Dissemination of bla OXA-23 in Acinetobacter spp. in China: Main Roles of Conjugative Plasmid pAZJ221 and Transposon Tn 2009

“…Besides sharing a common region (OXA-23-⌬ATPase), all the transposons have ISAba1 upstream from bla OXA-23 except Tn2007, which is correlated with ISAba4 (5, 9-11). Tn2006 and Tn2009 were also identified in non-baumannii species of Acinetobacter (7,8). Furthermore, the expression of bla OXA-23 has probably been enhanced by the strong promoters provided on the upstream insertion sequences of the transposons (12,13).…”

“…Moreover, the bla OXA-23 gene has also been detected in non-baumannii Acinetobacter spp. (7,8). Transposable elements have played an essential role in the dissemination of the bla gene between different genomic locations within one bacterium or between different isolates (5).…”

AbaR4-Type Resistance Island Including the bla OXA-23 Gene in Acinetobacter nosocomialis Isolates

“…In our recent study, two carbapenem-resistant A. nosocomialis isolates from South Korea contained the bla SIM-1 gene, which has been identified in other Acinetobacter species, including A. baumannii (3,4,7,12). Although bla OXA-23 has been identified in A. radioresistens and Acinetobacter baylyi (9,12), it was first identified in A. nosocomialis. Thus, our findings in this study suggest that interspecies transfer of the resistance island may occur, which could contribute to the dissemination of the antimicrobial-resistant isolates of Acinetobacter species.…”

“…A. nosocomialis is the second-most-frequent species isolated from blood among the genus Acinetobacter in South Korea and displays a low carbapenem resistance rate but a high polymyxin resistance rate, unlike A. baumannii (6). In our recent study, two carbapenem-resistant A. nosocomialis isolates from South Korea contained the bla SIM-1 gene, which has been identified in other Acinetobacter species, including A. baumannii (3,4,7,12). Although bla OXA-23 has been identified in A. radioresistens and Acinetobacter baylyi (9,12), it was first identified in A. nosocomialis.…”

Evaluation of Double-Disk Potentiation and Disk Potentiation Tests Using Dipicolinic Acid for Detection of Metallo-β-Lactamase-Producing Pseudomonas spp. and Acinetobacter spp

“…(17), but the study did not include SIM-1-producing Acinetobacter spp. isolates, which are present in Korea (13) and China (21).…”