Three cases of IMP-type metallo-β-lactamase-producing Enterobacter cloacae bloodstream infection in Japan

We report three cases of IMP-type metallo-β-lactamase-producing Enterobacter cloacae bloodstream infection, which showed minimum inhibitory concentration values for imipenem with 2 μg/ml in all isolates. Although carbapenems were initiated empirically in all cases, two of three cases died. The Clinical and Laboratory Standards Institute lowered the breakpoints of carbapenems for Enterobacteriaceae in 2010. However, the previous breakpoints are still used in many clinical laboratories, which can result in failure to detect carbapenem-resistant Enterobacteriaceae. Therefore, lower breakpoints of carbapenems should be used in clinical settings, and alternative tests for detecting metallo-β-lactamase such as polymerase chain reaction and immunochromatographic assays may contribute to better detection of carbapenem-resistant isolates.     

Molecular and epidemiological analysis of IMP-1 metallo-β-lactamase-producing Klebsiella pneumoniae in a tertiary care hospital in Japan

This study investigated the molecular and phenotypic characteristics of carbapenemase-producing Klebsiella pneumoniae, and identified the risk factors underlying its acquisition. We evaluated K. pneumoniae isolated in Nagasaki University Hospital between January 2009 and June 2015. The presence of carbapenemase genes and plasmid characteristics were investigated. We performed multilocus sequence typing (MLST), and generated a dendrogram based on the results of pulsed-field gel electrophoresis (PFGE) for carbapenemase-producing strains. We also performed a case-control study of patients. Of the 88 K. pneumoniae strains that showed minimum inhibitory concentration ≥1 μg/mL for imipenem and/or meropenem, and that were available from our bacterial collection, 18 had the IMP-type carbapenemase gene, all of which were IMP-1 according to sequencing analysis. Strains included seven different sequence types (STs), of which the most common was ST1471. A dendrogram showed the significant similarity of some strains with relationships in PFGE patterns, STs, and the wards in which they were isolated. Plasmid incompatibility group was similar among the IMP-1 producers. Regarding risk factors, multivariate analysis showed that liver disease and previous uses of carbapenems and anti-fungal drugs were significant factors for the acquisition of IMP-1-producing strains. Our results demonstrate that IMP-1 is a major carbapenemase produced by K. pneumoniae. The PFGE results indicated the possibility of transmission in the hospital. The identified risk factors should be considered for appropriate antibiotic therapy and infection-control measures.     

Dissemination of New Delhi metallo-β-lactamase-1-producing Acinetobacter baumannii in Europe

Clin Microbiol Infect 2012; 18: E362-E365 ABSTRACT: Multidrug-resistant and New Delhi metallo-β-lactamase 1 (NDM-1) -producing Acinetobacter baumannii are increasingly reported. A collection of five NDM-1-positive A.?baumannii isolates recovered in four European countries were analysed. Genotyping was performed by pulsed-field gel electrophoresis, multiplex PCR sequence typing, Diversilab and multilocus sequence typing. Three distinct sequence types were identified. All isolates harboured a chromosomally located bla(NDM-1) gene within a Tn125-like transposon. One isolate co-expressed another unrelated carbapenemase OXA-23. This report constitutes the first epidemiological study of NDM-1-producing A.?baumannii from four countries.     

Dissemination in Japan of multidrug-resistant Pseudomonas aeruginosa isolates producing IMP-type metallo-β-lactamases and AAC(6′)-Iae/AAC(6′)-Ib

The spread throughout Japan of antibiotic-resistance factors in multidrug-resistant (MDR) Pseudomonas aeruginosa isolates was investigated epidemiologically, using immunochromatographic assays specific for IMP-type metallo-β-lactamases (IMPs) and aminoglycoside 6′-N-acetyltransferase [AAC(6′)]-Iae and -Ib. Three hundred MDR P. aeruginosa isolates were obtained during each of two years, 2011 and 2012, from 190 hospitals in 39 prefectures in Japan. The percentage of P. aeruginosa isolates producing IMPs, AAC(6′)-Iae or AAC(6′)-Ib increased significantly from 170/300 (56.7%) in 2011 to 230/300 (76.7%) in 2012, with 134/170 (78.8%) in 2011 and 179/230 (77.8%) in 2012 producing both IMP and either AAC(6′)-Iae or AAC(6′)-Ib. The MICs of antibiotics, including cephalosporins and carbapenems, were markedly higher for isolates that did than did not produce these resistance factors. These results indicated that MDR P. aeruginosa producing IMPs, AAC(6′)-Iae or AAC(6′)-Ib have spread throughout Japan and that these antibiotic-resistance factors are useful markers for monitoring MDR P. aeruginosa in Japan.     

Clinical and molecular analyses of bloodstream infections caused by IMP metallo-β-lactamase-producing Enterobacteriaceae in a tertiary hospital in Japan

Carbapenemase-producing Enterobacteriaceae infection has been reported worldwide and is a major threat to public health. However, reports of bloodstream infection (BSI) caused by metallo-β-lactamase (MBL), especially the IMP-type, are limited. Therefore, we aimed to investigate the clinical and microbial characteristics of patients with BSI caused by IMP-type MBL-producing Enterobacteriaceae (MBL-E) in a tertiary care hospital in Japan. The clinical data were collected from medical charts for all the patients. A next-generation sequencing approach and multilocus sequence typing were used to identify antimicrobial resistance genes. Six patients were enrolled and had severe conditions on admission. The sources of MBL-E BSI were as follows: catheter-related BSI, pyelonephritis, cholangitis, and bacterial peritonitis. No isolate was resistant to levofloxacin or aminoglycoside. Microbiological response rates were 100%. The all-cause 30-day mortality rate was 50%. Of the six isolates, three were Enterobacter hormaechei sequence type 78, one was Enterobacter cloacae Hoffman cluster IV ST997, and two were Klebsiella pneumoniae (ST134 and ST252). All isolates produced IMP-1 and carried bla_IMP-1 gene and various antimicrobial resistance genes. The results of this study showed that MBL-E BSI was fatal, although rare, in patients with severe diseases and long-term hospitalization. Further research is necessary to determine the appropriate treatment strategies for MBL-producing BSI.     

Molecular characterization of extended-spectrum-β-lactamase-producing and plasmid-mediated AmpC β-lactamase-producing Escherichia coli isolated from stray dogs in South Korea

A total of 47 extended-spectrum-cephalosporin-resistant Escherichia coli strains isolated from stray dogs in 2006 and 2007 in the Republic of Korea were investigated using molecular methods. Extended-spectrum β-lactamase (ESBL) and AmpC β-lactamase phenotypes were identified in 12 and 23 E. coli isolates, respectively. All 12 ESBL-producing isolates carried bla(CTX-M) genes. The most common CTX-M types were CTX-M-14 (n = 5) and CTX-M-24 (n = 3). Isolates producing CTX-M-3, CTX-M-55, CTX-M-27, and CTX-M-65 were also identified. Twenty-one of 23 AmpC β-lactamase-producing isolates were found to carry bla(CMY-2) genes. TEM-1 was associated with CTX-M and CMY-2 β-lactamases in 4 and 15 isolates, respectively. In addition to bla(TEM-1), two isolates carried bla(DHA-1), and one of them cocarried bla(CMY-2). Both CTX-M and CMY-2 genes were located on large (40 to 170 kb) conjugative plasmids that contained the insertion sequence ISEcp1 upstream of the bla genes. Only in the case of CTX-M genes was there an IS903 sequence downstream of the gene. The spread of ESBLs and AmpC β-lactamases occurred via both horizontal gene transfer, accounting for much of the CTX-M gene dissemination, and clonal spread, accounting for CMY-2 gene dissemination. The horizontal dissemination of bla(CTX-M) and bla(CMY-2) genes was mediated by IncF and IncI1-Iγ plasmids, respectively. The clonal spread of bla(CMY-2) was driven mainly by E. coli strains of virulent phylogroup D lineage ST648. To our knowledge, this is the first report of bla(DHA-1) in E. coli strains isolated from companion animals. This study also represents the first report of CMY-2 β-lactamase-producing E. coli isolates from dogs in the Republic of Korea.     

First report of 16S rRNA methylase ArmA-producing Acinetobacter baumannii and rapid spread of metallo-β-lactamase NDM-1 in Algerian hospitals

PurposeThe aim of the present study was to characterize the molecular support of resistance to carbapenems, aminoglycosides and fluoroquinolones in carbapenem-resistant Acinetobacter baumannii clinical isolates recovered between January 2011 and April 2013 from Algerian hospitals.MethodsAntibiotic susceptibility testing was performed using disk diffusion and Etest methods. Carbapenemase activity was detected using both MALDI-TOF mass spectrometry assay and via microbiological tests. Carbapenem, aminoglycoside and fluoroquinolone resistance determinants were studied by PCR and sequencing. Clonal relationships between strains were determined using Multi Locus Sequence Typing (MLST).ResultsA total of 47 imipenem-resistant A. baumannii were isolated and identified by MALDI-TOF mass spectrometry. All imipenem-resistant strains were positive in the modified Hodge test, and EDTA inhibited the activity of metallo-β-lactamases enzymes in 11 strains. The bla_OXA-23 gene was detected in 33 strains and the bla_OXA-24 gene in 10 strains. The metallo-β-lactamase bla_NDM-1 gene was detected in 11 isolates (23.4%) from Algiers and Sétif, including 7 that co-expressed a bla_OXA-23 gene. Resistance to aminoglycosides was due to the production of aminoglycoside-modifying enzymes, AAC(3)-Ia, AADA, ANT(2″)-I, APH(3′)-VI, and 16S rRNA methylases, ArmA. The fluoroquinolone resistance was mainly associated with mutations at Ser83Leu and Ser80Leu of the gyrA and parC genes, respectively. MLST revealed five sequence types (STs), 1, 2, 19, 25, and 85. The imipenem-resistant A. baumannii ST2 was the predominant clone (35/47).ConclusionsHere we report for the first time clinical multidrug-resistant A. baumannii isolates harboring 16S rRNA methylase gene, armA, and rapid spread of metallo-β-lactamase NDM-1 isolated from patients in Algeria.     

Molecular characteristics of extended-spectrum β-lactamase-producing Escherichia coli in Japan: emergence of CTX-M-15-producing E. coli ST131

We investigated the molecular characteristics of ESBL-producing Escherichia coli in Japan. A total of 101 clinical isolates of ESBL-positive E. coli collected in Japan between June 2008 and November 2009 were studied. Among the 101 strains, 97 were positive for CTX-M, while 47 and two were positive for TEM and SHV, respectively. Sequencing revealed that CTX-M-14 was most common (49/101), followed by CTX-M-27 (22/101) and CTX-M-15 (8/101). Based on MLST data, seven of eight CTX-M-15 producers belonged to ST131. This is the first report about clinical isolates of E. coli ST131 possessing CTX-M-15 in Japan.     

Identification of 50 Class D β-Lactamases and 65 Acinetobacter-Derived Cephalosporinases in Acinetobacter spp.

Whole-genome sequencing of a collection of 103 Acinetobacter strains belonging to 22 validly named species and another 16 putative species allowed detection of genes for 50 new class D β-lactamases and 65 new Acinetobacter-derived cephalosporinases (ADC). All oxacillinases (OXA) contained the three typical motifs of class D β-lactamases, STFK, (F/Y)GN, and K(S/T)G. The phylogenetic tree drawn from the OXA sequences led to an increase in the number of OXA groups from 7 to 18. The topologies of the OXA and RpoB phylogenetic trees were similar, supporting the ancient acquisition of bla_OXA genes by Acinetobacter species. The class D β-lactamase genes appeared to be intrinsic to several species, such as Acinetobacter baumannii, Acinetobacter pittii, Acinetobacter calcoaceticus, and Acinetobacter lwoffii. Neither bla_OXA-40/143- nor bla_OXA-58-like genes were detected, and their origin remains therefore unknown. The phylogenetic tree analysis based on the alignment of the sequences deduced from bla_ADC revealed five main clusters, one containing ADC belonging to species closely related to A. baumannii and the others composed of cephalosporinases from the remaining species. No indication of bla_OXA or bla_ADC transfer was observed between distantly related species, except for bla_OXA-279, possibly transferred from Acinetobacter genomic species 6 to Acinetobacter parvus. Analysis of β-lactam susceptibility of seven strains harboring new oxacillinases and cloning of the corresponding genes in Escherichia coli and in a susceptible A. baumannii strain indicated very weak hydrolysis of carbapenems. Overall, this study reveals a large pool of β-lactamases in different Acinetobacter spp., potentially transferable to pathogenic strains of the genus.     

Use of high-dose IV and aerosolized colistin for the treatment of multidrug-resistant Acinetobacter baumannii ventilator-associated pneumonia: do we really need this treatment?

In this study we aimed to assess the safety and efficacy of high-dose IV colistin (COL) and aerosolized COL for the treatment of Acinetobacter baumannii ventilator-associated pneumonia (VAP). Critically ill adult patients who received IV COL for multidrug-resistant A. baumannii VAP were evaluated retrospectively. A total of 45 patients were evaluated [15 patients with high-dose COL (2.5 mg/kg every 6 h), 20 patients with normal dose (2.5 mg/kg every 12 h), and 10 patients with low dose, determined according to creatine clearance]. Aerosolized COL was used in 29 patients treated with parenteral COL and 16 patients received only parenteral COL. The clinical response rates on the fifth day were 50, 30, and 27 % with the normal, low, and high doses, respectively. However, the clinical response rates at the end of the therapy had declined to 30, 30, and 7 % with the normal, low, and high doses, respectively. The bacteriological clearance rates at the end of the therapy were 65, 75, and 64 %, with the normal, low, and high doses, respectively. With the aerosolized COL, the clinical response rates on the fifth day and at the end of the therapy were 35 and 14 %, whereas these rates were 44 and 38 % without the aerosolized COL. Bacteriological clearance rates with and without the aerosolized COL were 76 and 69 %, respectively. The nephrotoxicity rate was 40 % for the high-dose COL, whereas it was 35 % for the normal dose, and 20 % for the low-dose COL. In conclusion, higher doses of COL and aerosolized COL had no advantages over lower doses in alleviating multidrug-resistant A. baumannii VAP. Moreover, the higher doses and the aerosolized COL increased the nephrotoxicity risk and seemed not to be safe.     

Molecular and Epidemiological Characterization of IMP-Type Metallo-β-Lactamase-Producing Enterobacter cloacae in a Large Tertiary Care Hospital in Japan

IMP-type metallo-β-lactamase enzymes have been reported in different geographical areas and in various Gram-negative bacteria. However, the risk factors and epidemiology pertaining to IMP-type metallo-β-lactamase-producing Enterobacter cloacae (IMP-producing E. cloacae) have not been systematically evaluated. We conducted a retrospective, matched case-control study of patients from whom IMP-producing E. cloacae isolates were obtained, in addition to performing thorough molecular analyses of the clinically obtained IMP-producing E. cloacae isolates. Unique cases with IMP-producing E. cloacae isolation were included. Patients with IMP-producing E. cloacae were matched to uninfected controls at a ratio of 1 to 3. Fifteen IMP-producing E. cloacae cases were identified, with five of the isolates being obtained from blood, and they were matched to 45 uninfected controls. All (100%) patients from whom IMP-producing E. cloacae isolates were obtained had indwelling devices at the time of isolation, compared with one (2.2%) uninfected control. Independent predictors for isolation of IMP-producing E. cloacae were identified as cephalosporin exposure and invasive procedures within 3 months. Although in-hospital mortality rates were similar between cases and controls (14.3% versus 13.3%), the in-hospital mortality of patients with IMP-producing E. cloacae-caused bacteremia was significantly higher (40%) than the rate in controls. IMP-producing E. cloacae isolates were frequently positive for other resistance determinants. The MICs of meropenem and imipenem were not elevated; 10 (67%) and 12 (80%) of the 15 IMP-producing E. cloacae isolates had a MIC of ≤1 μg/ml. A phylogenetic tree showed a close relationship among the IMP-producing E. cloacae samples. Indwelling devices, exposure to cephalosporin, and a history of invasive procedures were associated with isolation of IMP-producing E. cloacae. Screening for carbapenemase production is important in order to apply appropriate clinical management and infection control measures.     

Effect of sodium mercaptoacetic acid on different antimicrobial disks in the sodium mercaptoacetic acid double disk synergy test for detection of IMP-1 metallo-β-lactamase-producing Pseudomonas aeruginosa isolates in Japan

We determined the optimal antimicrobial in the sodium mercaptoacetic acid double disk synergy test (SMA-DDST) for the detection of IMP-1-producing Pseudomonas aeruginosa isolates in Japan and evaluated the performance of the test.Fifty-four P. aeruginosa clinical isolates were tested, including 39 IMP-1 producers and 15 non-metallo-β-lactamase (MBL)-producing carbapenem- and ceftazidime (CAZ)-resistant isolates. The SMA-DDST was performed with CAZ, cefepime (CFPM), imipenem (IPM), meropenem (MEPM), doripenem (DRPM), or biapenem (BIPM)-containing disks. The sensitivity of the SMA-DDST with CAZ, CFPM, IPM, MEPM, DRPM, and BIPM was 39/39 (100%), 36/39 (92%), 18/39 (46%), 8/39 (21%), 19/39 (49%), and 36/39 (92%), respectively. The specificity was 15/15 (100%) for all SMA-DDSTs. This suggests that the isolates may have a resistance mechanism other than MBL production for IPM, MEPM, or DRPM. Since the CAZ resistance mechanism in P. aeruginosa is the same as that of CFPM, but differs from that of carbapenems, we conclude that combining CAZ with BIPM SMA-DDSTs can prevent any failure in the detection of IMP-1-producing P. aeruginosa.