Coexistence of blaOXA-48 and aac(6')-Ib-cr genes in Klebsiella pneumoniae isolates from Istanbul, Turkey

This study evaluated the presence of carbapenem hydrolysing β-lactamase genes and plasmid-mediated quinolone resistance (PMQR) determinants in 22 Klebsiella pneumoniae isolates collected from the Istanbul Medical Faculty, Turkey, which reduced the susceptibility or resistance to carbapenem. The VITEK(?) 2 system and E-tests were used to determine the minimum inhibitory concentrations needed to inhibit bacterial growth. Genes were screened by polymerase chain reaction, and gene transferability was evaluated by transconjugation. Strain clonality was investigated by pulsed-field gel electrophoresis (PFGE). All strains were OXA-48 β-lactamase producers and three (13.6%) were also positive for the aac(6')-Ib-cr gene. Most of the strains harboured other β-lactamase (bla) genes such as bla(TEM), bla(SHV), bla(CTX-M) and bla(VEB-1). The transconjugants mostly harboured bla(OXA-48) and other β-lactamases separately. PFGE revealed eight pulsotypes among the isolates. The coexistence of bla(OXA-48) and PMQR in K. pneumoniae isolates may present a significant threat to health, especially in the nosocomial setting.     

Functional and structural characterization of the genetic environment of an extended-spectrum beta-lactamase blaVEB gene from a Pseudomonas aeruginosa isolate obtained in India

A Pseudomonas aeruginosa clinical strain isolated from a patient hospitalized in a New Delhi, India, hospital was resistant to expanded-spectrum cephalosporins, imipenem, and aztreonam. A bla(VEB-1)-like gene named bla(VEB-1a), which codes for the extended-spectrum beta-lactamase VEB-1a, was identified. The genetic environment of bla(VEB-1a) was peculiar: (i) no 5' conserved sequence (5'-CS) region was present upstream of the beta-lactamase gene, whereas bla(VEB-1)-like genes are usually associated with class 1 integrons; (ii) bla(VEB-1a) was inserted between two truncated 3'-CS regions in a direct repeat; and (iii) four 135-bp repeated DNA sequences (repeated elements) were located on each side of the bla(VEB-1a) gene. Expression of the bla(VEB-1a) gene was driven by a strong promoter located in one of these repeated sequences. In addition, cloning of the beta-lactamase content of this P. aeruginosa isolate followed by expression in Escherichia coli identified the naturally occurring AmpC beta-lactamase and a gene encoding an OXA-2-like beta-lactamase located in a class 1 integron, In78, in which an insertion sequence, ISpa7, was inserted within its 5'-CS region.     

Nosocomial outbreak by Proteus mirabilis producing extended-spectrum beta-lactamase VEB-1 in a Korean university hospital

OBJECTIVES: To examine the molecular mechanisms involved in the beta-lactam resistance of multidrug-resistant Proteus mirabilis isolates that showed an unusual synergy between imipenem and ceftazidime in a Korean hospital. METHODS: Over an 11 month period, a total of 12 P. mirabilis isolates showing resistance to ampicillin, gentamicin, ceftazidime, cefotaxime, cefuroxime, cefalothin, cefepime, piperacillin, trimethoprim/sulfamethoxazole and ciprofloxacin, were recovered from the sputum and urine specimens of nine patients who were hospitalized in the neurosurgery ward. The extended-spectrum beta-lactamases were screened with a double disc synergy test using ceftazidime, cefotaxime, aztreonam, cefepime and clavulanate. The ESBL types were determined by PCR using specific primers for bla(TEM-1), bla(SHV-1), bla(CTX-M-1), bla(CTX-M-2), bla(CTX-M-8), bla(CTX-M-9), bla(PER-1), bla(GES-1), bla(VEB-1), bla(OXA-10) and bla(OXA-13) followed by sequencing. All the isolates underwent molecular typing by PFGE. The transferability was examined by conjugation. RESULTS AND CONCLUSIONS: All the isolates showed a marked synergy between the extended-spectrum cephalosporins and clavulanate together with an unusual synergy between cefoxitin and the cephalosporins (cefalothin, cefuroxime, ceftazidime, cefotaxime) and between imipenem, and ceftazidime and cefotaxime. Isoelectric focusing of the crude bacterial extracts showed a beta-lactamase band with a pI value of 5.4, which was inhibited by clavulanate. PCR and sequencing identified the gene to be bla(VEB-1). In addition, the aadB gene was detected, conferring aminoglycoside resistance. The resistance was not transferred by conjugation. The outbreak was of a clonal origin as shown by PFGE demonstrating an identical banding pattern. This is the first report of VEB-1-producing Enterobacteriaceae in Korea.     

SHV-12, SHV-5, SHV-2a and VEB-1 extended-spectrum beta-lactamases in Gram-negative bacteria isolated in a university hospital in Thailand.

Sixty-one extended-spectrum beta-lactamase (ESBL)-producing isolates were collected from Srinagarind Hospital, Thailand. These included 43 Enterobacteriaceae and 18 Pseudomonadaceae. The 43 Enterobacteriaceae were found to produce the following ESBLs: 26 (60.5%) SHV-12, 13 (30.2%) SHV-5, two (4.7%) SHV-2a, one (2.3%) VEB-1 and one (2.3%) unidentified. Twenty-four isolates (55.8%) also carried bla(TEM-1B), as well as bla(SHV) or bla(VEB-1). Plasmid DNA from transconjugants carrying the bla(SHV-12) gene showed various restriction patterns, indicating the distribution of the bla(SHV-12) gene among different antibiotic resistance plasmids. In contrast, bla(SHV-5) in 13 isolates was found on a single plasmid of c. 130 kb. Pulsed-field gel electrophoresis (PFGE) analysis of genomic DNA from these isolates revealed that nine of 11 Klebsiella pneumoniae gave the same pattern, indicating clonal spread of the strain within the hospital, together with the occasional spread of the plasmid to other strains. Among the pseudomonad isolates, 16 Pseudomonas aeruginosa and one Pseudomonas putida had bla(VEB-like) and one P. aeruginosa had bla(SHV-12). Nine of the 16 isolates carrying bla(VEB-like) (56.3%) had identical PFGE patterns, suggesting the dissemination of this gene, also by clonal spread. At least six different bla(VEB-like-)containing integrons were found among the 18 isolates. This is the first report of bacteria producing SHV-12 and SHV-2a in Thailand and the first report of SHV-12 in P. aeruginosa, of VEB-1 in Citrobacter freundii and a VEB-1-like beta-lactamase in P. putida. These findings indicate that ESBL genes in the Far East are part of a gene pool capable of broad horizontal gene transfer, in that these genes can transfer between different families of Gram-negative bacilli.     

Complex genetic structures with repeated elements, a sul-type class 1 integron, and the blaVEB extended-spectrum beta-lactamase gene

Two clinical isolates of Pseudomonas aeruginosa, TL-1 and TL-2, were isolated from a patient transferred from Bangladesh and hospitalized for osteomyelitis in Paris, France. P. aeruginosa TL-1 expressed the extended-spectrum beta-lactamase VEB-1a and was susceptible only to imipenem and colistin, while P. aeruginosa TL-2 expressed only the naturally occurring bla(AmpC) gene at a basal level and exhibited a wild-type beta-lactam resistance phenotype. In TL-1, the typical 5'-end conserved sequence (5'-CS) region of class 1 integrons usually present upstream of the bla(VEB-1a) gene was replaced by a truncated 3'-CS and a 135-bp repeated element (Re). Downstream of the bla(VEB-1a) gene, an insertion sequence, ISPa31 disrupted by ISPa30, and an orf513 sequence, belonging to a common region (conserved region 1 [CR1]) immediately upstream of the aphA-6 gene, were present. Further downstream, a second truncated 3'-CS region in direct repeat belonged to In51, an integron containing two gene cassettes (aadA6 and the OrfD cassette). Thus, the overall structure corresponded to a sul-type class 1 integron termed In121. Genetic analyses revealed that both isolates were clonally related and differed by a ca. 100-kb fragment that contained In121. Both isolates contained another integron, In122, that carried three gene cassettes: aadB, dfrA1, and the OrfX cassette. This work identifies for the first time the spread of Re-associated bla(VEB) genes located on a sul-type integron. It also reports for the first time a CR1 element in P. aeruginosa that is associated with an aminoglycoside resistance aphA-6 gene that is expressed from a composite promoter.     

Distribution of extended-spectrum beta-lactamases in clinical isolates of Enterobacteriaceae in Vietnam

Among 730 Escherichia coli, 438 Klebsiella pneumoniae, and 141 Proteus mirabilis isolates obtained between September 2000 and September 2001 in seven hospitals in Ho Chi Minh City, Vietnam, 26.6% were resistant to ceftazidime, 30% were resistant to cefotaxime, 31.5% were resistant to ceftriaxone, 15.9% were resistant to cefoperazone, and 6% were resistant to cefepime. Resistance to imipenem was found in 5.6% of the isolates. In 55 strains producing extended-spectrum beta-lactamases (32 E. coli isolates, 13 K. pneumoniae isolates, and 10 P. mirabilis isolates), structural genes for VEB-1 (25.5%), CTX-M (25.5%), SHV (38.1%), and TEM (76.3%) enzymes were detected alone or in combination. Sequencing of the PCR products obtained from the K. pneumoniae isolates revealed the presence of bla(VEB-1), bla(CTX-M-14), bla(CTX-M-17), bla(SHV-2), and bla(TEM-1). Molecular typing of the strains with a similar resistance phenotype to broad-spectrum cephalosporins indicated polyclonal spread. ISEcp1 was presumably responsible for dissemination of the bla(CTX-M-like) gene.     

Prevalence of Ambler class A and D beta-lactamases among clinical isolates of Pseudomonas aeruginosa in Korea

OBJECTIVES: Recently, resistance to extended-spectrum cephalosporins due to acquired beta-lactamases has been reported in Pseudomonas aeruginosa. The aim of this study was to investigate the prevalence of Ambler class A and D beta-lactamases and their extended-spectrum derivatives and antimicrobial susceptibilities of P. aeruginosa isolated from various parts of Korea. METHODS: A total of 252 consecutive, non-duplicate isolates of P. aeruginosa were studied for the presence of class A or D beta-lactamase. Antibiotic susceptibility tests and PCR amplification of genes encoding class A (bla(PSE-1), bla(PER-1), bla(VEB-1), bla(TEM), bla(SHV), bla(CTX-M) and bla(GES-1)) and class D beta-lactamases (bla(OXA-groupI), bla(OXA-groupII) and bla(OXA-groupIII)) were performed. For PCR-positive isolates, isoelectric focusing (IEF) analysis, sequencing and pulsed-field gel electrophoresis (PFGE) were performed. RESULTS: In 64 (25.4%) isolates, structural genes for PSE-1 (6.3%), OXA-10 (13.1%), OXA-4 (4.3%), OXA-30 (2.0%), OXA-2 (2.3%) and OXA-17 (0.4%) were found; their distribution varied between provinces. None harboured bla(PER-1), bla(VEB-1), bla(TEM), bla(SHV), bla(CTX-M) and bla(GES-1). The cross-class resistance rates to other antibiotics was significantly higher in class A and D beta-lactamase producers than in non-producers (P < 0.001 for aminoglycosides, ciprofloxacin and meropenem). CONCLUSIONS: OXA-type beta-lactamases are widespread, but their extended-spectrum derivatives are rare among P. aeruginosa in Korea. To our knowledge, this is the first report of OXA-17, an extended-spectrum derivative of OXA-10, outside the Middle East. In addition, combined resistance to ticarcillin and aminoglycosides was a useful indicator for P. aeruginosa producing PSE- or OXA-type beta-lactamases in this study.     

Diversity of clavulanic acid-inhibited extended-spectrum β-lactamases in Aeromonas spp. from the Seine River, Paris, France

Environmental Aeromonas sp. isolates resistant to ceftazidime were recovered during an environmental survey performed with water samples from the Seine River, in Paris, France, in November 2009. Selected isolates were identified by sequencing of the 16S rRNA and rpoB genes. PCR and cloning experiments were used to identify broad-spectrum-β-lactamase-encoding genes and their genetic context. Clavulanic acid-inhibited extended-spectrum-β-lactamase (ESBL) genes were identified in 71% of the Aeromonas sp. isolates. A variety of ESBL genes were detected, including bla(VEB-1a), bla(SHV-12), bla(PER-1), bla(PER-6), bla(TLA-2), and bla(GES-7), suggesting an aquatic reservoir of those ESBL genes. Moreover, the repeated elements and different insertion sequences were identified in association with the bla(PER-6) and the bla(VEB-1a) genes, respectively, indicating a wide diversity of mobilization events, making Aeromonas spp. a vehicle for ESBL dissemination.     

Prevalence and genetic analysis of plasmid-mediated quinolone resistance determinants QnrA and QnrS in Enterobacteriaceae isolates from a French university hospital

The spread of plasmid-mediated quinolone resistance determinants QnrA and QnrS was evaluated in a collection of 186 extended-spectrum beta-lactamase (ESBL)-positive enterobacterial isolates from 2002 to 2005 and 185 nalidixic acid-resistant strains isolated during the first 6 months of 2005 at the Bicêtre hospital, France. Out of these 186 ESBL-positive isolates, 2.2 and 1.6% carried a QnrA1 and a QnrS1 determinant, respectively. The ESBLs associated with QnrA1 were VEB-1, SHV-12, and CTX-M-1, whereas those associated with QnrS1 were TEM-52, SHV-12, and CTX-M-1. Among the 185 nalidixic acid-resistant strains isolated in 2005, 0.5 and 2.7% had a QnrA1 determinant and a QnrS1 determinant, respectively. The genetic environments of the qnrA1 gene differed but were always associated with sul1 type integrons. In contrast, qnrS1 genes were not embedded in class 1 integrons but located often (but not systematically) downstream of the insertion sequence ISEcl2 on plasmids that often carried a novel beta-lactamase gene, bla(LAP-1). This is the first study identifying the QnrS resistance determinant in Europe and indicating that this determinant might also be widespread.     

Novel genetic structure associated with an extended-spectrum beta-lactamase blaVEB gene in a Providencia stuartii clinical isolate from Algeria

A ceftazidime-resistant Providencia stuartii isolate from Algeria harbored a ca. 160-kb conjugative plasmid that contained a truncated bla(VEB-1b) gene flanked by three 135-bp repeated elements. This work gives further evidence of the worldwide spread of bla(VEB) genes that are associated with genetic structures other than class 1 integrons.     

Identification of the novel narrow-spectrum beta-lactamase SCO-1 in Acinetobacter spp. from Argentina

By studying the beta-lactamase content of several Acinetobacter spp. isolates from Argentina, producing the expanded-spectrum beta-lactamases (ESBL) VEB-1a or PER-2, a novel Ambler class A beta-lactamase gene was identified. It encoded the narrow-spectrum beta-lactamase SCO-1, whose activity was inhibited by clavulanic acid. SCO-1 hydrolyzes penicillins at a high level and cephalosporins and carbapenems at a very low level. beta-Lactamase SCO-1 was identified from unrelated VEB-1a-positive or PER-2-positive Acinetobacter spp. isolates recovered from three hospitals. The bla(SCO-1) gene was apparently located on a plasmid of ca. 150 kb from all cases but was not associated with any ESBL-encoding gene. The G+C content of the bla(SCO) gene was 52%, a value that does not correspond to that of the A. baumannii genome (39%). beta-Lactamase SCO-1 shares 47% amino acid identity with CARB-5 and ca. 40% with the enzymes TEM, SHV, and CTX-M. A gene encoding a putative resolvase was identified downstream of the bla(SCO-1) gene, but its precise way of acquisition remains to be determined.     

Presence of plasmid-mediated quinolone resistance in Klebsiella pneumoniae isolates possessing blaKPC in the United States

The presence of plasmid-mediated quinolone resistance genes [i.e., qnrA, qnrB, qnrS, aac(6')-Ib-cr, and qepA] was evaluated among 42 bla(KPC)-containing Klebsiella pneumoniae isolates collected in the eastern United States. One isolate carried the bla(KPC-3) and qnrB19 genes on the same conjugative plasmid, whereas another carried the bla(KPC-3) and qnrA1 genes on separate plasmids.     

Genetic features of blaNDM-1-positive Enterobacteriaceae

Genetic features associated with the bla(NDM-1) gene were investigated in 6 Escherichia coli, 7 Klebsiella pneumoniae, 1 Citrobacter freundii, 1 Proteus mirabilis, and 1 Providencia stuartii isolate of worldwide origin. Clonal diversity was observed for both E. coli and K. pneumoniae. The bla(NDM-1) gene was carried by different plasmid types (IncA/C, IncF, IncL/M, or untypeable) and was likely chromosome borne in two isolates. The bla(NDM-1) plasmids coharbored a variety of resistance determinants, including β-lactamase genes, quinolone resistance genes, and 16S RNA methylase genes.     

Plasmid-mediated quinolone resistance conferred by qnrS1 in Salmonella enterica serovar Virchow isolated from Turkish food of avian origin

OBJECTIVES: To study the molecular characteristics of the quinolone and associated ampicillin resistance mechanisms present in Salmonella enterica serovar Virchow isolated from Turkish foods. METHODS: Nine epidemiologically unrelated Salmonella Virchow strains isolated from foods (chicken and minced meat) sold in different markets in Ankara were analysed for their susceptibility to 17 antimicrobials. The strains were typed by PFGE and plasmid profiling and investigated by molecular methods (PCR/sequencing) for the presence of several resistance genes, class 1 integrons and mutations in the quinolone resistance-determining regions. Plasmids conferring quinolone resistance were analysed by restriction fragment length polymorphism (RFLP) analysis, DNA hybridization, sequencing, replicon-typing PCR and mating experiments. RESULTS: All strains showed nalidixic acid resistance (MIC >or= 128 mg/L) together with a decreased susceptibility to ciprofloxacin (three strains with an MIC of 1 mg/L and six with an MIC of 0.25 mg/L), associated with mutations within the gyrA gene (Asp-87 --> Tyr-87). In three strains, qnrS1 genes were detected. Ampicillin resistance encoded by a bla(CTX-M3) gene and/or bla(TEM-1-like) gene was found in four strains. Three of these strains carried an approximately 45 kb conjugative plasmid, designated pRQ2006, harbouring qnrS1 and a Tn3-like transposon. Partial sequencing and RFLP of pRQ2006 indicated its similarity to the qnrS1 plasmid pAH03786 found in a Japanese Shigella flexneri 2b isolate. CONCLUSIONS: This is the first study describing the presence of qnrS1 genes in bacterial isolates from Turkey. The pRQ2006 plasmid seems to be more related to the S. flexneri 2b qnrS1 plasmid pAH0376 than to the Salmonella qnrS1-carrying plasmids pINF5 and TPqnrS-2.     

Emergence of plasmid-mediated quinolone resistance in Escherichia coli in Europe

Although quinolone resistance results mostly from chromosomal mutations, it may also be mediated by a plasmid-encoded qnr gene in members of the family Enterobacteriaceae. Thus, 297 nalidixic-acid resistant strains of 2,700 Escherichia coli strains that had been isolated at the Bicetre Hospital (Le Kremlin-Bicetre, France) in 2003 were screened for qnr by PCR. A single E. coli isolate that carried a ca. 180-kb conjugative plasmid encoding a qnr determinant was identified. It conferred low-level resistance to quinolones and was associated with a chromosomal mutation in subunit A of the topoisomerase II gene. The qnr gene was located on a sul1-type class 1 integron just downstream of a conserved region (CR) element (CR1) comprising the Orf513 recombinase. Promoter sequences for qnr expression overlapped the extremity of CR1, indicating the role of CR1 in the expression of antibiotic resistance genes. This integron was different from other qnr-positive sul1-type integrons identified in American and Chinese enterobacterial isolates. In addition, plasmid pQR1 carried another class 1 integron that was identical to In53 from E. coli. The latter integron possessed a series of gene cassettes, including those coding for the extended-spectrum beta-lactamase VEB-1, the rifampin ADP ribosyltransferase ARR-2, and several aminoglycoside resistance markers. This is the first report of plasmid-mediated quinolone resistance in Europe associated with an unknown level of plasmid-mediated multidrug resistance in Enterobacteriaceae.     

Complex class 1 integrons with diverse variable regions, including aac(6')-Ib-cr, and a novel allele, qnrB10, associated with ISCR1 in clinical enterobacterial isolates from Argentina

Transferable quinolone resistance has not previously been reported in Argentina. Here we describe three complex class 1 integrons harboring the novel allele qnrB10 in a unique region downstream of orf513, one of them also containing aac(6')-Ib-cr within the variable region of integrons. The three arrays differed from bla(CTX-M-2)-bearing integrons, which are broadly distributed in Argentina.     

Complete sequence of a novel 178-kilobase plasmid carrying bla(NDM-1) in a Providencia stuartii strain isolated in Afghanistan

In response to global concerns over the spread of the New Delhi metallo-β-lactamase gene 1, bla(NDM-1), a monthly surveillance program was initiated in September 2010. All carbapenem-resistant Gram-negative strains forwarded to our facility are screened for this gene. To date, 321 carbapenem-resistant isolates, encompassing 11 bacterial species, have been tested. In February 2011, two strains of Providencia stuartii, submitted from a military hospital in Afghanistan, tested positive for bla(NDM-1). Both strains were identical by pulsed-field gel electrophoresis (PFGE). bla(NDM-1) was carried on a large plasmid, pMR0211, which was sequenced by emulsion PCR and pyrosequencing. pMR0211 is 178,277 bp in size and belongs to incompatibility group A/C. The plasmid consists of a backbone with considerable homology to pAR060302 from Escherichia coli, and it retains many of the antibiotic resistance genes associated with it. The plasmid also shares common elements with the pNDM-HK plasmid, including bla(NDM-1), armA, and sul1. However, gene orientation is reversed, and a 3-kb fragment from this region is absent from pMR0211. pMR0211 also contains additional genes, including the aminoglycoside-modifying enzyme loci aadA and aac(6'), the quinolone resistance gene qnrA, a gene with highest homology to a U32 family peptidase from Shewanella amazonensis, and the bla(OXA-10) gene. The finding of this gene in an intrinsically colistin-resistant species such as Providencia stuartii is especially worrisome, as it renders the organism resistant to nearly every available antibiotic. The presence of multiple insertion sequences and transposons flanking the region containing the bla(NDM-1) gene further highlights the potential mobility associated with this gene.     

Biochemical sequence analyses of GES-1, a novel class A extended-spectrum beta-lactamase, and the class 1 integron In52 from Klebsiella pneumoniae

Klebsiella pneumoniae ORI-1 was isolated in 1998 in France from a rectal swab of a 1-month-old girl who was previously hospitalized in Cayenne Hospital, Cayenne, French Guiana. This strain harbored a ca. 140-kb nontransferable plasmid, pTK1, that conferred an extended-spectrum cephalosporin resistance profile antagonized by the addition of clavulanic acid, tazobactam, or imipenem. The gene for GES-1 (Guiana extended-spectrum beta-lactamase) was cloned, and its protein was expressed in Escherichia coli DH10B, where this pI-5. 8 beta-lactamase of a ca. 31-kDa molecular mass conferred resistance to oxyimino cephalosporins (mostly to ceftazidime). GES-1 is weakly related to the other plasmid-located Ambler class A extended-spectrum beta-lactamases (ESBLs). The highest percentage of amino acid identity was obtained with the carbenicillinase GN79 from Proteus mirabilis; with YENT, a chromosome-borne penicillinase from Yersinia enterocolitica; and with L-2, a chromosome-borne class A cephalosporinase from Stenotrophomonas maltophilia (36% amino acid identity each). However, a dendrogram analysis showed that GES-1 clustered within a class A ESBL subgroup together with ESBLs VEB-1 and PER-1. Sequencing of a 7,098-bp DNA fragment from plasmid pTK1 revealed that the GES-1 gene was located on a novel class 1 integron named In52 that was characterized by (i) a 5' conserved segment containing an intI1 gene possessing two putative promoters, P(1) and P(2), for coordinated expression of the downstream antibiotic resistance genes and an attI1 recombination site; (ii) five antibiotic gene cassettes, bla(GES-1), aac(6')Ib' (gentamicin resistance and amikacin susceptibility), dfrXVb (trimethoprim resistance), a novel chloramphenicol resistance gene (cmlA4), and aadA2 (streptomycin-spectinomycin resistance); and (iii) a 3' conserved segment consisting of qacEDelta1 and sulI. The bla(GES-1) and aadA2 gene cassettes were peculiar, since they lacked a typical 59-base element. This work identified the second class A ESBL gene of a non-TEM, non-SHV series which was located in the plasmid and integron, thus providing it additional means for its spread and its expression.     

Emergence of Proteus mirabilis harboring blaKPC-2 and qnrD in a Chinese Hospital

Nineteen carbapenem-nonsusceptible Proteus mirabilis isolates were recovered from intensive care units in the Second Affiliated Hospital of Zhejiang University during a 3-month period. The isolates showed a high level of resistance against ciprofloxacin, in addition to their resistance against the carbapenems. Pulsed-field gel electrophoresis (PFGE) analysis showed that these isolates belonged to three clonal strains. PCRs and DNA sequence analysis of the carbapenemase and other β-lactamase genes indicated that all the isolates harbored the bla(KPC-2) gene. Twelve of 19 isolates harbored the plasmid-mediated quinolone resistance (PMQR) genes, both the qnrD and aac(6')-Ib-cr genes. Eight representative isolates with high levels of quinolone resistance carried the similar mutation profiles of S83I in gyrA, E466D in gyrB, and S80I in parC. Reduced carbapenem susceptibility was transferred to Escherichia coli (EC600) in a conjugation experiment, while the quinolone resistance was not. DNA hybridization showed that qnrD was located on a plasmid of approximately 4.5 kb. In summary, large clonally related isolates of KPC-2-producing P. mirabilis emerged in a Chinese hospital, and qnrD was detected in KPC-producing P. mirabilis for the first time.     

Plasmid-mediated quinolone resistance determinant qnrS1 found in Salmonella enterica strains isolated in the UK

OBJECTIVES: To determine the prevalence of qnr genes in selected Salmonella enterica and Escherichia coli isolated in the UK. METHODS: One hundred and eighteen S. enterica and 103 E. coli were screened for qnrA, qnrB and qnrS by PCR. Transferability of qnr plasmids was assessed and isolated plasmids compared with previously identified qnr plasmids by restriction fragment length polymorphism analysis and hybridization experiments. PCRs and sequencing identified co-transferred beta-lactamase genes and mutations in the quinolone resistance-determining region of gyrA. RESULTS: Only six S. enterica strains belonging to four serotypes (Stanley, Typhimurium, Virchow and Virginia) were positive for qnrS1. qnrS1 was present on plasmids of 13.5 kb (TPqnrS-1a and -1b) in Typhimurium and Virginia isolates, 44 kb (TPqnrS-2) in two Virchow isolates and >148 kb (TPqnrS-3a and -3b) in two Stanley isolates. bla(TEM-1) and a group 9 bla(CTX-M) were co-transferred on TPqnrS-2 and TPqnrS-3b. Hybridization of a qnrS1 probe to digested qnrS1 plasmids suggested qnrS1 on TPqnrS-2 may be located in a similar genetic environment to Shigella qnrS plasmid pAH0376, but in a different environment in the other plasmids. CONCLUSIONS: This is the first report of plasmid-mediated quinolone resistance in a Salmonella isolate from the UK; five isolates were associated with foreign travel to, or food imported from, the Far East. The presence of qnrS1 on different plasmid backbones in several Salmonella serotypes suggests successful dissemination of plasmids or qnrS1. It is of concern that qnrS1 is being identified in Salmonella serotypes that are commonly implicated in human infection in the UK. Coupled with beta-lactam resistance, it may compromise treatment of vulnerable patient groups.