Convenient test for screening metallo-beta-lactamase-producing gram-negative bacteria by using thiol compounds

Chemical sensors for the early diagnosis of bacterial resistance to β-lactam antibiotics

β-Lactamases are bacterial enzymes that inactivate β-lactam antibiotics and, as such, are the most prevalent cause of antibiotic resistance in Gram-negative bacteria. The ever-increasing production and worldwide dissemination of bacterial strains producing carbapenemases is currently a global health concern. These enzymes catalyze the hydrolysis of carbapenems - the β-lactam antibiotics with the broadest spectrum of activity that are often considered as drugs of last resort. The incidence of carbapenem-resistant pathogens such as Pseudomonas aeruginosa, Acinetobacter baumannii and carbapenemase or extended spectrum beta-lactamase (ESBL)-producing Enterobacterales, which are frequent in clinical settings, is worrisome since, in some cases, no therapies are available. These include all metallo-β-lactamases (VIM, IMP, NDM, SMP, and L1), and serine-carbapenemases of classes A (KPC, SME, IMI, and GES), and of classes D (OXA-23, OXA-24/40, OXA-48 and OXA-58). Consequently, the early diagnosis of bacterial strains harboring carbapenemases is a pivotal task in clinical microbiology in order to track antibiotic bacterial resistance and to improve the worldwide management of infectious diseases. Recent research efforts on the development of chromogenic and fluorescent chemical sensors for the specific and sensitive detection and quantification of β-lactamase production in multidrug-resistant pathogens are summarized herein. Studies to circumvent the main limitations of the phenotypic and molecular methods are discussed. Recently reported chromogenic and fluorogenic cephalosporin- and carbapenem-based β-lactamase substrates will be reviewed as alternative options to the currently available nitrocefin and related compounds, a chromogenic cephalosporin-based reagent widely used in clinical microbiology laboratories. The scope of these new chemical sensors, along with the synthetic approaches to synthesize them, is also summarized.

Clinical and Microbiological Characteristics of Bacteremia Caused by Carbapenemase-producing Enterobacterales in Minami Ibaraki Area, Japan

Although recent propagation of carbapenemase-producing Enterobacterales (CPE) has become a problem worldwide, the picture of CPE infection in Japan has not fully been elucidated. In this study, we examined clinical and microbiological characteristics of invasive CPE infection occurring at 8 hospitals in Minami Ibaraki Area between July 2001 to June 2017. Of 7294 Enterobacterales strains isolated from independent cases of bacteremia and/or meningitis, 10 (0.14%) were CPE (8 Enterobacter cloacae-complex, 1 Escherichia coli, and 1 Edwardsiella tarda）, all of which had the blaIMP-1 gene and susceptible to gentamicin and trimethoprim/sulfamethoxazole. These strains were isolated from 7 adult and 2 infant bacteremia (1 infant patient developed CPE bacteremia twice) after 2007. The most common portal of entry was intravenous catheters. All of the adult patients were recovered, while the infant patients eventually died. Genomic analyses showed that the 8 E. cloacae-complex strains were classified into 5 groups, each of which was exclusively detected in specific facilities at intervals of up to 3 years, suggesting persistent colonization in the facilities. This study showed that invasive CPE infection in the area was rare, caused by IMP-1-type CPE having susceptibility to various antibiotics, and nonfatal among adult patients.

The First Swedish Outbreak with VIM-2-Producing Pseudomonas aeruginosa, Occurring between 2006 and 2007, Was Probably Due to Contaminated Hospital Sinks

Multidrug-resistant Pseudomonas aeruginosa is an increasing clinical problem worldwide. The aim of this study was to describe the first outbreak of a Verona integron-borne metallo-ß-lactamase (VIM)-2-producing P. aeruginosa strain in Sweden and its expansion in the region. A cluster of multidrug-resistant P. aeruginosa appeared at two neighbouring hospitals in 2006. The isolates were characterized by PCR, pulsed-field gel electrophoresis (PFGE), and whole-genome sequencing. Patient charts, laboratory records, and hygiene routines were reviewed, and patients, staff, and the environment were screened. The investigation revealed a clonal outbreak of a VIM-2-producing P. aeruginosa strain belonging to the high-risk clonal complex 111, susceptible only to gentamicin and colistin. No direct contact between patients could be established, but most of them had stayed in certain rooms/wards weeks to months apart. Cultures from two sinks yielded growth of the same strain. The outbreak ended when control measures against the sinks were taken, but new cases occurred in a tertiary care hospital in the region. In conclusion, when facing prolonged outbreaks with this bacterium, sinks and other water sources in the hospital environment should be considered. By implementing proactive control measures to limit the bacterial load in sinks, the waterborne transmission of P. aeruginosa may be reduced.

Genetic and phenotypic analyses of mcr-harboring extended-spectrum β-lactamase-producing Escherichia coli isolates from companion dogs and cats in Japan

The emergence of mcr plasmid-mediated colistin-resistant extended-spectrum β-lactamase (ESBL)-producing Enterobacterales among companion dogs and cats poses a risk of the animals acting as reservoirs for cross-species transmission. However, current knowledge of mcr-harboring ESBL-producing Enterobacterales in companion dogs and cats is still limited; thus, the genetic and phenotypic characteristics of the bacterial isolates and plasmids, in companion dogs and cats, remain to be elucidated. Here, we identified mcr gene-harboring ESBL-producing Escherichia coli isolates during whole-genome sequencing of ESBL-producing E. coli isolates from a dog and a cat in Osaka, Japan. Colistin-resistant MY732 isolate from a dog carried two plasmids: mcr-1.1-harboring IncI2 plasmid and bla_CTX-M-14-harboring IncFIB plasmid. Conjugation assays revealed that both plasmids can be co-transferred even though the IncFIB plasmid lacked a conjugal transfer gene cassette. The other isolate MY504 from a cat harbored two bla genes and mcr-9 on the identical IncHI2 plasmid. This isolate was not resistant to colistin, which is likely to be due to deletion of the regulatory two-component QseBC system associated with the mcr-9 expression. To the best of our knowledge, this is the first report of a colistin-resistant ESBL-producing E. coli isolate harboring mcr-1 from a companion dog in Japan. Given that the mcr gene-harboring IncI2 and IncHI2 plasmids in this study shared high homology with plasmids from human or animal-derived Enterobacterales, companion dogs and cats may act as important reservoirs for cross-species transmission of the mcr gene in the community, in Japan.

Correlation between Antimicrobial Resistance and the Hospital-Wide Diverse Use of Broad-Spectrum Antibiotics by the Antimicrobial Stewardship Program in Japan

Increased antibiotic use and antibiotic homogeneity cause selective pressure. This study investigated the correlation between antibiotic diversity and antimicrobial resistance (AMR) in Gram-negative organisms. The days of therapy/100 patient-days (DOT) for four broad-spectrum antibiotic classes were evaluated for 2015-2022. The antibiotic heterogeneity index (AHI) for the equal use of four classes (25%) and the modified AHI for the equal use of three classes (30%), excluding fluoroquinolones (10%), were measured (target: 1.0). Quarterly antibiotic use markers and the resistance rates against ≥2 anti-Pseudomonas antibiotics were compared. The DOT value was 9.94, and the relative DOT were 34.8% for carbapenems, 32.1% for piperacillin/tazobactam, 24.3% for fourth generation cephalosporins/ceftazidime/aztreonam, and 8.9% for fluoroquinolones. Although no correlation was found between the total DOT and the resistance rate for any bacterium, a significant negative correlation was found between the heterogeneity indices and resistance rates for Pseudomonas aeruginosa and Klebsiella pneumoniae. The significant cutoffs that discriminate the risk of resistance were 0.756 for the AHI and 0.889 for the modified AHI for K. pneumoniae. Antibiotic diversity is more important in preventing AMR than overall antibiotic use. The ideal ratio of broad-spectrum antibiotics should be studied for diversified use to prevent AMR.

Performance of Phenotypic Tests to Detect β-Lactamases in a Population of β-Lactamase Coproducing Enterobacteriaceae Isolates

Objectives This study aimed to evaluate the performance of routinely used phenotypic tests to detect β-lactamase production in isolates coproducing multiple β-lactamase types.

Methods Commonly used phenotypic tests for the detection of extended spectrum β-lactamases (ESBL), AmpC β-lactamase, and carbapenemases were compared with detection and sequencing of β-lactamase genes (as the reference test) in 176 uropathogenic Enterobacteriaceae coproducing multiple β-lactamases from two hospitals in the Western Province of Sri Lanka.

Results Majority of the isolates (147/176, 83.5%) carried β-lactamase genes with (90/147, 61%) harboring multiple genes. The Clinical and Laboratory Standards Institute screening method using cefotaxime (sensitivity [Se], 97; specificity [Sp], 93; accuracy [Ac], 94) and ceftriaxone (Se, 97; Sp, 91; Ac, 93) was the most effective to detect ESBLs. The modified double disc synergy test (Se, 98; Sp, 98; Ac, 97) and combined disc test (Se, 94; Sp, 98; Ac, 96) showed good specificity for confirmation of ESBLs. Cefoxitin resistance (Se, 97; Sp, 73; Ac, 85) and the AmpC disc test (Se, 96; Sp, 82; Ac, 86) were sensitive to detect AmpC β-lactamase producers coproducing other β-lactamases but showed low specificity, probably due to coproduction of carbapenemases. Meropenem was useful to screen for New Delhi metallo β-lactamases and OXA-48-like carbapenemases (Se, 97; Sp, 96; Ac, 96). The modified carbapenem inactivation method showed excellent performance (Se, 97; Sp, 98; Ac, 97) in identifying production of both types of carbapenemases and was able to distinguish this from carbapenem resistance due to potential mutations in the porin gene.

Conclusions Microbiology laboratories that are still depend on phenotypic tests should utilize tests that are compatible with the types of β-lactamase prevalent in the region and those that are least affected by coexisting resistance mechanisms.

Clinical characteristics and treatment of IMP-type carbapenemase-producing Enterobacteriaceae bacteremia: Case series and literature review

BACKGROUND

Several carbapenemases have been identified globally in Enterobacteriaceae. In Japan, IMP-type carbapenemase is the most prevalent, although cases of carbapenemase-producing Enterobacteriaceae (CPE) bacteremia are still scarce. The present case series and literature review aimed to elucidate the clinical characteristics and treatment strategies for IMP-type CPE bacteremia.

METHODS

Clinical data on pediatric cases of IMP-type CPE bacteremia at the Tokyo Metropolitan Children's Medical Center between 2010 and 2020 were collected, and a review of past studies of IMP-type CPE bacteremia has been provided.

RESULTS

Five pediatric episodes of IMP-type CPE bacteremia were identified. Our review of previous literature on IMP-type CPE bacteremia revealed 24 adult patients, but no pediatric patients. All 29 cases had underlying diseases, and 23 (79%) received combination therapy. The median duration of antibiotic therapy was 14 days (interquartile range: 9-14 days). The overall mortality rate was 38% (11/29). The mortality rates associated with monotherapy and combination therapy were 67% (4/6) and 30% (7/23), respectively.

CONCLUSIONS

We report the first case series of IMP-type CPE bacteremia in children. Our review of past studies suggests that combination therapy might lead to better survival outcomes in patients with IMP-type CPE bacteremia. Further research is needed to establish an optimal treatment strategy for IMP-type CPE bacteremia.

Clinical characteristics and risk factors for multidrug-resistant bacterial isolation in patients with international travel history

BACKGROUND

International travelers are at risk of carrying resistant bacteria. It is critical to identify risk factors associated with multidrug-resistant organism (MDRO) colonization in travelers.

METHODS

A retrospective chart review observational study was conducted at two tertiary centers in Japan for inpatients who had been hospitalized or visited an outpatient clinic overseas within the previous 12 months. These patients underwent MDRO screening upon admission. To identify independent predictors for the isolation of MDROs, multivariable analyses were performed using logistic regression.

RESULTS

In total, 76 (35%) of the 216 patients were positive for MDROs at admission. The majority of bacteria detected in stool samples were extended-spectrum beta-lactamase-producing Escherichia coli (ESBLEC) (n = 67 [89%]). ESBLEC was detected in nearly 40% of patients who traveled to Asia. Travel to Asia was an independent risk factor for any MDRO and ESBLEC isolation. For non-ESBLEC MDRO isolation, a history of surgery abroad was an independent risk factor for detection.

DISCUSSION AND CONCLUSIONS

A history of hospitalization abroad has previously been found to be associated with MDRO colonization in travelers, which was not identified as a risk factor in this study. The risk factors for MDRO colonization were different between ESBLEC and non-ESBL MDROs.

Prevalence and Molecular Characterization of Metallo β-Lactamase Producing Gram-Negative Pathogens Causing Eye Infections

Purpose:

Metallo β-lactamases (MβL) production is a worldwide problem, particularly in gram-negative bacteria. As scanty data is available on the prevalence of MBL, the present study is being undertaken to determine the prevalence, antibacterial sensitivity patterns, and molecular characterization of MβL associated resistant genes in gram-negative bacteria isolated from ocular infections.

Material and Methods

At a tertiary eye care center in south India, 359 gram-negative pathogens, 200 isolates from eye infections, and 159 isolates from normal flora of the eye were studied. A gold standard microbiology method was used to identify the isolates. An antibiotic double disc synergy test and a combination disc test were used to detect MβL production. Multiplex PCR was used to investigate the molecular characteristics of the MβL encoding genes blaVIM, blaIMP, and blaNDM.

Results

Of the 359 gram-negative bacterial pathogens, Pseudomonas aeruginosa 108 (30.1%) and Enterobacter agglomerans 46 (12.8%) were commonly isolated. High prevalence of P. aeruginosa 81% (17 strains) was detected as an MβL producer and it shows 100% resistance to 2nd and 3rd generation cephalosporins and meropenem. Multiplex PCR detected only the blaVIM gene in 56 (28%) of various eye infections and 27 (17%) of normal flora of the gram-negative bacteria (GNB). The blaVIM gene is detected predominantly in 51.8% of keratitis and 21.4% of postoperative endophthalmitis. High prevalence of the gene was detected in P. aeruginosa 42.9% (24 of 56) and Alcaligens denitrificans 10.7% (6 of 56) from eye infections. Whereas, in the control group, P. aeruginosa and E. coli each had 14.8% (4 of 27) that were shown positive.

Conclusion

The emerging MβLs mediated resistance among P. aeruginosa is a challenging task for ophthalmologists, especially in patients with endophthalmitis and bacterial keratitis. This local knowledge will aid in advising appropriate antibiotic use and avoiding unnecessary antibiotic prescriptions, which are highly warranted.

Whole-Genome Sequencing Analysis of blaNDM-5/IncX3 Plasmid Estimated to be Conjugative-Transferred in the Gut

We characterized plasmids carrying bla_NDM-5 detected in Escherichia coli isolated from the infection site and stool sample of a Japanese patient, with no international travel history, by whole-genome sequencing (WGS). WGS was performed using MiSeq and MinlON sequencer followed by hybrid de novo assembly. bla_NDM-5 was detected on IncX3 (bla_NDM-5/IncX3) plasmids; pMTY18530-4_IncX3 in E. coli TUM18530 isolated from a wound above the pubis; pMTY18780-5_IncX3 and pMTY18781-1_IncX3 in E. coli TUM18780 and TUM18781, respectively, isolated from stool. These three plasmids resembled each other and pGSH8M-2-4, previously detected in E. coli isolated from a Tokyo Bay water sample. E. coli TUM18530 and TUM18780 belonged to sequence type (ST) 1011 and had only two single nucleotide polymorphisms on the core-genome, whereas TUM18781 belonged to ST2040. Three bla_NDM-5/IncX3 plasmids (pMTY18530-4_IncX3, pMTY18780-5_IncX3, and pMTY18781-1_IncX3) exhibited conjugative transfer in vitro at an average frequency of 1.71 × 10^-3 per donor cell. The transconjugant was resistant to only β-lactams, including carbapenem, except aztreonam. Similarity of the bla_NDM-5/IncX3 plasmids isolated from our patient compared with that isolated from the Tokyo bay water sample suggested that the plasmids may have already spread throughout the Japanese community. The bla_NDM-5/IncX3 plasmid exhibited potential for easy transmission to different strains in the patient's intestine.

Epidemiology and molecular characterization of fecal carriage of third-generation cephalosporin-resistant enterobacterales among elderly residents in Japan

INTRODUCTION

The spread of third-generation cephalosporin-resistant Gram-negative bacteria is a serious concern in acute and post-acute care settings. This study aimed to understand the epidemiology and molecular background of fecal colonization of resistant Enterobacterales in elderly people.

METHODS

In December 2015-December 2017, stool or rectal swab samples were collected from 101 elderly patients receiving home care, using long-term care facilities (LTCF), and living in nursing homes repeatedly at 3-9-month intervals. Patient clinical background data were collected from medical records. After phenotypic screening for extended-spectrum β-lactamase (ESBL), AmpC-type β-lactamase or carbapenemase production, drug resistance genes of isolates were analyzed using polymerase chain reaction (PCR). ESBL-producing Escherichia coli isolates obtained from the same patients in repetitive screenings were analyzed using PCR-based ORF typing. Risk factors for persistent carriage of resistant Enterobacterales were analyzed using multivariate analysis.

RESULTS

Resistant Enterobacterales isolates were detected in 37 of 101 (36.6%) and 29 of 80 (36.3%) residents in first and second screenings, respectively. ESBL-producing E. coli accounted for 80% isolates, the most common being CTX-M-9-group β-lactamase producers. Molecular epidemiological analysis revealed probable transmissions of ESBL-producing E. coli; 58% of ESBL-producing E. coli colonizers were persistent colonizers at least after 3 -month intervals. Age > 87 years and LTCF residence were independent risk factors for persistent carriage of ESBL-producing E. coli.

CONCLUSIONS

We showed, for the first time, high persistent colonization rate of ESBL-producing E. coli among elderly people in post-acute care settings with probable horizontal transmission. We also identified significant risk factors for persistent colonization.

Novel approach for rapid detection of extended spectrum β-lactamase and metalloid-β-lactamase using drug susceptibility testing microfluidic device (DSTM)

BACKGROUND/PURPOSE

Rapid detection of β-lactamases is important in a recent situation where resistant bacteria are increasing. By using the drug susceptibility testing microfluidic device (DSTM), rapid screening of extended spectrum β-lactamases (ESBLs) and metallo-β-lactamases (MBLs) has become possible.

METHODS

β-lactams and β-lactamase inhibitors were pre-fixed in the DSTM for use. A bacterial suspension in Mueller-Hinton broth (McF 0.25) was introduced into the device, and the effects of β-lactamase inhibitor on morphological changes caused by β-lactam were evaluated after 3 h incubation.

RESULTS

Clinical isolates genetically confirmed to produce β-lactamase were used. Of the 84 ESBL-producing strains, 80 strains (95%) turned to be ESBL positive, and five strains (6%) of them MBL were positive as well as ESBL. Four strains (5%) were negative for both ESBL and MBL. Of the 24 MBL-producing strains, 23 strains (96%) were positive for MBL. All the 43 AmpC-producing strains were negative for both ESBL and MBL. Of the 156 ESBL- and MBL-nonproducing strains, 155 strains (99%) were negative for both ESBL and MBL, and one strain was positive for ESBL. With this method, the detection sensitivity was 95% and the specificity was 100% for ESBL, whereas the detection sensitivity was 96% and the specificity was 98% for MBL. These results were not significantly different from the results of the disc diffusion method.

CONCLUSION

The DSTM method allows rapid detection of β-lactamases in 3 h and may be a useful replacement for the disc diffusion method.

Practical agar-based disk-diffusion tests using sulfamoyl heteroarylcarboxylic acids for identification of subclass B1 metallo-β-lactamase-producing Enterobacterales

The worldwide distribution of carbapenemase-producing Enterobacterales (CPE) is a serious public health concern as they exhibit carbapenem resistance, thus limiting the choice of antimicrobials for treating CPE infections. The combination treatment with a β-lactam and one of the newly approved β-lactamase inhibitors, such as avibactam, relebactam, or vaborbactam, provides a valuable tool to cope with CPE; however, these inhibitors are active only against serine-type carbapenemases, and not against metallo-β-lactamases (MβLs). Therefore, it is important to readily differentiate carbapenemases produced by CPE by using simple and reliable methods in order to choose an appropriate treatment. Here, we developed three practical agar-based disk-diffusion tests (double-disk synergy test [DDST], disk potentiation test, and modified carbapenem inactivation method [mCIM]) to discriminate the production of subclass B1 MβLs, such as IMP-, NDM-, and VIM-type MβLs, from the other carbapenemases, especially serine-type carbapenemases. This was accomplished using B1 MβL-specific sulfamoyl heteroarylcarboxylic acid inhibitors, 2,5-dimethyl-4-sulfamoylfuran-3-carboxylic acid (SFC) and 2,5-diethyl-1-methyl-4-sulfamoylpyrrole-3-carboxylic acid (SPC), originally developed by us. The DDST and mCIM using SFC and SPC revealed high sensitivity (95.3%) and specificity (100%) in detecting B1 MβL-producing Enterobacterales. In disk potentiation test, the sensitivities using SFC and SPC were 89.1% and 93.8%, respectively, whereas the specificities for both were 100%. These methods are simple and inexpensive, and have a high accuracy rate. These methods would, therefore, be of immense assistance in the specific detection and discrimination of B1 MβL-producing Enterobacterales in clinical microbiology laboratories, and would lead to better prevention against infection with such multidrug-resistant bacteria in clinical settings.

On-Site Genomic Epidemiological Analysis of Antimicrobial-Resistant Bacteria in Cambodia With Portable Laboratory Equipment

The rapid emergence of carbapenemase-producing gram-negative bacteria (CPGNB) is a global threat due to the high mortality of infection and limited treatment options. Although there have been many reports of CPGNB isolated from Southeast Asian countries, to date there has been no genetic analysis of CPGNB isolated from Cambodia. Sequence-based molecular epidemiological analysis enables a better understanding of the genotypic characteristics and epidemiological significance of antimicrobial-resistant (AMR) bacteria in each country, and allows countries to enact measures related to AMR issues. In this study, we performed on-site genomic epidemiological analysis of CPGNB isolated in Cambodia using a portable laboratory equipment called Bento Lab, which combines a PCR thermal cycler, microcentrifuge, gel electrophoresis apparatus, and LED transilluminator, along with the MinION nanopore sequencer. PCR targeting of major carbapenemase genes using Bento Lab revealed that two Escherichia coli isolates and one Acinetobacter baumannii isolate harbored carbapenemase genes: bla_NDM, bla_OXA–48, and bla_OXA–23, respectively. The results of phenotypic diagnostic tests for CPGNB, such as the carbapenem inactivation method and double-disk diffusion test using a specific inhibitor of metallo-β-lactamases, were consistent with their AMR genotypes. Whole-genome sequencing analysis using MinION revealed that bla_NDM–5 gene was carried on a 93.9-kb plasmid with IncFIA/IncFIB/IncFII/IncQ1 replicons, and bla_OXA–181 gene was carried on a 51.5-kb plasmid with the IncX3 replicon in E. coli isolates. bla_OXA–23 was encoded in two locations on the chromosome of A. baumannii. Plasmids carrying bla_NDM–5 or bla_OXA–181 in E. coli were highly structurally identical to plasmids prevalent in Enterobacterales in China and other countries, suggesting that they disseminated from a common evolutionary origin. Our findings demonstrate the potential impact of portable laboratory equipment on AMR bacteria research in hospitals and research centers with limited research facilities, and provide the first glimpse into the genomic epidemiology of CPGNB in Cambodia.

Institutional outbreak involving multiple clades of IMP-producing Enterobacter cloacae complex sequence type 78 at a cancer center in Tokyo, Japan

Background

Information about the clinical and microbiological characteristics of IMP-producing Enterobacterales has been limited. Here, we describe an institutional outbreak of IMP-producing Enterobacter cloacae complex (ECC) involving multiple clades of ECC sequence type (ST) 78 strains.

Methods

Antimicrobial susceptibility testing, whole-genome sequencing, and conjugation experiments of 18 IMP-producing ECC strains isolated during four-year study period were performed. Species and subspecies were determined by average nucleotide identity analysis and clonal relatedness of the isolates was analyzed with multilocus sequence typing and core-genome single nucleotide polymorphism (SNP) analysis. Relevant clinical information was extracted from medical records.

Results

Fourteen of 18 IMP-producing ECC isolates were determined as Enterobacter hormaechei ST78. Sixteen isolates, including 13 isolates belonging to ST78, carried bla_IMP-1 in In316-like class 1 integron and also carried IncHI2 plasmids. Conjugation experiments were successful for 12 isolates carrying bla_IMP-1 on IncHI2 plasmids and for an isolate carrying bla_IMP-11 on an IncL/M plasmid. Although isolation of ST78 strains was clustered in a 14-months period suggesting nosocomial transmission, these strains were subdivided into three clades by SNP analysis: clade A (n = 10), clade B (n = 1), clade C (n = 3). A part of clonal relatedness was unexpected by the epidemiological information at the time of isolation of the strains. Most of the IMP-producing ECC strains were susceptible to non-β-lactam antibiotics and had relatively low minimum inhibitory concentrations to carbapenems (≤4 μg/mL). Five of six infections caused by IMP-producing ECC were treated successfully.

Conclusions

Whole-genome sequencing analysis revealed the outbreak was caused by three different clades of ST78 strains, where patients had favorable treatment outcome of the infections compared with that caused by Enterobacterales producing other carbapenemases, possibly due to their non-multidrug-resistant phenotype.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-05952-9.

Comparison of ertapenem non-susceptibility with 2-mercaptopropionic acid phenotypic tests in predicting NDM-1 and IMP-1 production in clinical isolates of Escherichia coli

Background:

A routine phenotypic test has not been recommended for the detection of metallo-β-lactamases (MBLs) producing Enterobacteriaceae species such as Escherichia coli. The current study was conducted to compare the 2-mercaptopropionic acid (2-MPA) phenotypic method and ertapenem non-susceptibility test with polymerase chain reaction in predicting the production of MBLs in clinical isolates of E. coli.

Methods:

Antimicrobial susceptibility test for beta-lactam antibiotics were performed by disk diffusion method. All isolates which showed inhibition zones of ≤ 22 mm for CAZ and ≤ 27 mm for CTX were considered potential MBLs producing isolates. The production of MBLs was confirmed using 2-MPA compound. Also, susceptibility to ertapenem was evaluated in all isolates. Conventional PCR was performed to detect blaIMP-1 and/or blaNDM-1 genes in all potential MBLs producing E. coli isolates.

Results:

Of 259, 138 (53.3%) isolates were potential MBLs producing bacteria. One hundred and fifteen out of 138 (83.3%) isolates were susceptible to ertapenem. MBLs production was confirmed in 75/138 (54.4%) isolates by 2-MPA phenotypic method. The blaNDM-1 or/and blaIMP-1 genes were found in 30/75(40%) and 39/115(33.9%) isolates which were confirmed by 2-MPA and were susceptible to ertapenem, respectively. The sensitivity of 2-MPA method and ertapenem non-susceptibility test compared with PCR were 65.2% and 15.2%, and the specificity was 52.1% versus 82.6%, respectively.

Conclusion:

This study demonstrated that the 2-MPA phenotypic method does not have acceptable sensitivity and specificity in comparison with PCR, but its results are more reliable for the detection of MBL producing E. coli isolates compared with non-susceptibility to ertapenem.

Whole-genome analyses of extended-spectrum or AmpC β-lactamase-producing Escherichia coli isolates from companion dogs in Japan

The emergence and global spread of extended-spectrum or AmpC β-lactamase (ESBL/AmpC)-producing Enterobacteriaceae in companion animals have led to the hypothesis that companion animals might be reservoirs for cross-species transmission because of their close contact with humans. However, current knowledge in this field is limited; therefore, the role of companion animals in cross-species transmission remains to be elucidated. Herein, we studied ESBL/AmpC-producing Enterobacteriaceae, Escherichia coli in particular, isolated from extraintestinal sites and feces of companion dogs. Whole-genome sequencing analysis revealed that (i) extraintestinal E. coli isolates were most closely related to those isolated from feces from the same dog, (ii) chromosomal sequences in the ST131/C1-M27 clade isolated from companion dogs were highly similar to those in the ST131/C1-M27 clade of human origin, (iii) certain plasmids, such as IncFII/pMLST F1:A2:B20/bla_CTX-M-27, IncI1/pMLST16/bla_CTX-M-15, or IncI1/bla_CMY-2 from dog-derived E. coli isolates, shared high homology with those from several human-derived Enterobacteriaceae, (iv) chromosomal bla_CTX-M-14 was identified in the ST38 isolate from a companion dog, and (v) eight out of 14 tested ESBL/AmpC-producing E. coli isolates (i.e., ST131, ST68, ST405, and ST998) belonged to the human extraintestinal pathogenic E. coli (ExPEC) group. All of the bla-coding plasmids that were sequenced genome-wide were capable of horizontal transfer. These results suggest that companion dogs can spread ESBL/AmpC-producing ExPEC via their feces. Furthermore, at least some ESBL/AmpC-producing ExPECs and bla-coding plasmids can be transmitted between humans and companion dogs. Thus, companion dogs can act as an important reservoir for ESBL/AmpC-producing E. coli in the community.

Emergence of Enterobacter cloacae Complex Co-Producing IMP-10 and CTX-M, and Klebsiella pneumoniae Producing VIM-1 in Clinical Isolates in Japan

BACKGROUND

Carbapenemase-producing Enterobacteriaceae (CPE) are an emerging threat in healthcare settings worldwide.

OBJECTIVES

We evaluated the presence of carbapenemase genes in CPE in a tertiary care university hospital in Tokyo, Japan.

METHODS

Carbapenem-resistant clinical isolates were collected in 2018 at Teikyo University Hospital (Tokyo, Japan). Bacterial species were identified using MALDI-TOF MS. Carbapenemase production was evaluated using a carbapenemase inactivation method. The presence of carbapenemase genes was confirmed by multiplex PCR and DNA sequencing.

RESULTS

Four CPE isolates were identified: two Enterobacter cloacae complex strains and Klebsiella oxytoca and Klebsiella pneumoniae strains. Three of the isolates (E. cloacae complex and K. oxytoca) were IMP-1-type producers, including IMP-10 in their produced metallo-β-lactamase, and are epidemic in East Japan. The IMP-10-producing E. cloacae complex strain also produced CTX-M ESBL. The other CPE isolate (K. pneumoniae) is a VIM-1 producer. VIM-1-producing K. pneumoniae is epidemic in Europe, especially in Greece. Accordingly, the VIM-1 producer was isolated from a patient with a medical history in Greece.

CONCLUSIONS

This study revealed the emergence of E. cloacae complex co-producing IMP-1-type carbapenemase and CTX-M ESBL, and K. pneumoniae producing VIM-1 carbapenemase in clinical isolates in Japan. Metallo-β-lactamase was the most prevalent type of carbapenemase at Teikyo University Hospital, especially IMP-1-type carbapenemase. The detection of VIM-1-producing K. pneumoniae suggests that epidemic CPE from overseas can spread to countries with low CPE prevalence, such as Japan, highlighting the need for active surveillance.

Multidrug-Resistant Bacteria Isolated from Different Aquatic Environments in the North of Spain and South of France

Due to the global progress of antimicrobial resistance, the World Health Organization (WHO) published the list of the antibiotic-resistant "priority pathogens" in order to promote research and development of new antibiotics to the families of bacteria that cause severe and often deadly infections. In the framework of the One Health approach, the surveillance of these pathogens in different environments should be implemented in order to analyze their spread and the potential risk of transmission of antibiotic resistances by food and water. Therefore, the objective of this work was to determine the presence of high and critical priority pathogens included in the aforementioned list in different aquatic environments in the POCTEFA area (North Spain-South France). In addition to these pathogens, detection of colistin-resistant Enterobacteriaceae was included due its relevance as being the antibiotic of choice to treat infections caused by multidrug resistant bacteria (MDR). From the total of 80 analyzed samples, 100% of the wastewater treatment plants (WWTPs) and collectors (from hospitals and slaughterhouses) and 96.4% of the rivers, carried antibiotic resistant bacteria (ARB) against the tested antibiotics. Fifty-five (17.7%) of the isolates were identified as target microorganisms (high and critical priority pathogens of WHO list) and 58.2% (n = 32) of them came from WWTPs and collectors. Phenotypic and genotypic characterization showed that 96.4% were MDR and resistance to penicillins/cephalosporins was the most widespread. The presence of bla genes, KPC-type carbapenemases, mcr-1 and vanB genes has been confirmed. In summary, the presence of clinically relevant MDR bacteria in the studied aquatic environments demonstrates the need to improve surveillance and treatments of wastewaters from slaughterhouses, hospitals and WWTPs, in order to minimize the dispersion of resistance through the effluents of these areas.

Review of phenotypic assays for detection of extended-spectrum β-lactamases and carbapenemases: a microbiology laboratory bench guide

Background

Infections caused by gram-negative antibiotic-resistant bacteria continue to increase. Despite recommendations by the Clinical Laboratory Standards Institute (CLSI) and the European Committee on Antimicrobial Susceptibility Testing (EUCAST) with regards to detection of antibiotic degrading enzymes secreted by these bacteria, the true prevalence of extended-spectrum β-lactamase (ESBL) and carbapenemase producers remains a difficult task to resolve. Describing of previously designed phenotypic detection assays for ESBLs and carbapenemases in a single document avails a summary that allows for multiple testing which increases the sensitivity and specificity of detection.

Methods and aims

This review, therefore, defined and classified ESBLs and carbapenemases, and also briefly described how the several previously designed phenotypic detection assays for the same should be performed.

Conclusion

Extended-spectrum β-lactamase and carbapenemase detection assays, once performed correctly, can precisely discriminate between bacteria producing these enzymes and those with other mechanisms of resistance to β-lactam antibiotics.

Prevalence of plasmid-encoded carbapenemases in multi-drug resistant Escherichia coli from patients with urinary tract infection in northern Iran

OBJECTIVES

Resistance to carbapenems as the last line for controlling resistant bacteria is increasing due to production of carbapenemase. The aim of this study was to detect the plasmid-encoded carbapenemases using phenotypic methods and multiplex PCR among the multi-drug resistant (MDR) isolates from patients with urinary tract infection (UTI) in northern Iran.

MATERIALS AND METHODS

Antimicrobial susceptibility testing and extended spectrum β-lactamase (ESBL) production test were performed for 91 MDR Escherichia coli strains by disc diffusion and double disk synergy tests (DDST), respectively. Carbapenemases production was confirmed using Hodge test, EDTA double disk synergy test (EDST) and combined disk test (CDT). The isolates were subjected to PCR targeting bla IMP, bla VIM, bla KPC and bla OXA-48 β-Lactamase genes.

RESULTS

Resistance of isolates to 1st, 2nd, 3rd, and 4th generations of cephalosporins, carbapenems, and penicillins were 73%, 84.5%, 62%, 37.5%, 17.5%, and 76%, respectively. Based on CDT and Hodge test, 1 (3%) and based on EDST, 2 (6%) of 33 ESBL producers synthesize a type of carbapenemase. The frequency of bla IMP, bla VIM, bla KPC, and bla OXA-48 genes was 8.7%, 9.8%, 2.1%, and 15.3%, respectively. Existence of bla IMP conferred more resistance to cephalotin, fosfomycin, and piperacillin (P≤0.01) and carrying bla VIM caused more resistance to cephalotin, cefepime, and ceftazidime (P≤0.01). The presence of bla KPC conferred more resistance to cephalotin and presence of bla OXA-48 caused more resistance to chloramphenicol and piperacillin (P≤0.05).

CONCLUSION

Identification and controlling of this nearly low frequent ESBL and carbapenemase producing strains are important due to the presence of plasmid genes encoding carbapenemase.

A prolonged multispecies outbreak of IMP-6 carbapenemase-producing Enterobacterales due to horizontal transmission of the IncN plasmid

A multispecies outbreak of IMP-6 carbapenemase-producing Enterobacterales (IMP-6-CPE) occurred at an acute care hospital in Japan. This study was conducted to understand the mechanisms of IMP-6-CPE transmission by pulsed-field gel electrophoresis (PFGE), multilocus sequence typing and whole-genome sequencing (WGS), and identify risk factors for IMP-6-CPE acquisition in patients who underwent abdominal surgery. Between July 2013 and March 2014, 22 hospitalized patients infected or colonized with IMP-6-CPE (Escherichia coli [n = 8], Klebsiella oxytoca [n = 5], Enterobacter cloacae [n = 5], Klebsiella pneumoniae [n = 3] and Klebsiella aerogenes [n = 1]) were identified. There were diverse PFGE profiles and sequence types (STs) in most of the species except for K. oxytoca. All isolates of K. oxytoca belonged to ST29 with similar PFGE profiles, suggesting their clonal transmission. Plasmid analysis by WGS revealed that all 22 isolates but one shared a ca. 50-kb IncN plasmid backbone with bla_IMP-6 suggesting interspecies gene transmission, and typing of plasmids explained epidemiological links among cases. A case-control study showed pancreatoduodenectomy, changing drains in fluoroscopy room, continuous peritoneal lavage and enteric fistula were associated with IMP-6-CPE acquisition among the patients. Plasmid analysis of isolates in an outbreak of IMP-6-CPE suggested interspecies gene transmission and helped to clarify hidden epidemiological links between cases.

FALSE POSITIVE PHENOTYPIC DETECTION OF METALLO-BETA-LACTAMASES IN ACINETOBACTER BAUMANNII

Phenotypic detection of metallo-β-lactamases (MBLs) in Acinetobacter (A.) baumannii is a serious challenge to clinical microbiologists. MBLs are inhibited by metal chelators such as ethylenediaminetetraacetic acid) (EDTA). Production of MBLs cannot be recognized based on resistance phenotype. Therefore, phenotypic tests using EDTA are recommended. The aim of this study was to investigate the sensitivity and specificity of inhibitor based tests (EDTA) for detection of MBL. A total of 172 A. baumannii strains (123 carbapenemase positive and 49 carbapenemase negative) were analyzed. Phenotypic detection of MBLs was performed by the combined disk test with EDTA (CDT-EDTA) and EPI-dilution test (EPI-DT). Both tests were positive in all 11 isolates possessing VIM-1 MBL, showing 100% sensitivity. However, false positive results were observed in strains with class D carbapenemases using both tests, i.e. all OXA-23 and OXA-24/40 producing organisms and most OXA-58 positive strains (77% with CDT-EDTA vs. 65% with EPI-DT). False positive results can occur because oxacillinases are converted to a less active state in the presence of EDTA, leading to augmentation of the inhibition zone around the carbapenem disk or reduction of carbapenem minimum inhibitory concentrations. This study showed high sensitivity but low specificity of phenotypic methods in the detection of MBLs.

A novel disk-based detection method with superior sensitivity for β-lactamase production in third-generation cephalosporin-resistant Enterobacteriaceae

OBJECTIVE

Current phenotypic methods for extended-spectrum β-lactamase (ESBL), AmpC β-lactamase (AmpC), and carbapenemases fail to detect isolates that co-produce other classes of β-lactamases. In this study, we have developed a novel assay (Applied Multiplex Disk Method: AMU-DM) for the phenotypic detection and identification of β-lactamases produced by Enterobacteriaceae.

METHODS

We evaluated the performance of the method by comparison with PCR results for 78 Enterobacteriaceae clinical isolates that were positive by the ESBL screening test and negative by the ESBL confirmation test. Additionally, one NCTC strain and four ATCC strains were also included in the test population for the study as reference.

RESULTS

For 79/83 (95%) isolates tested, the AMU-DM results matched those obtained by PCR. The concordance rates were 31/31 (100%), 11/11 (100%), 3/3 (100%), 0/1 (0%), 15/15 (100%), 16/19 (84%), and 3/3 (100%) for AmpC, ESBL and AmpC co-production, Klebsiella pneumoniae carbapenemase (KPC), KPC and ESBL co-production, metallo β-lactamase (MBL), MBL and ESBL co-production, and MBL and AmpC co-production, respectively.

CONCLUSION

The AMU-DM is convenient to perform, economical, and highly sensitive in identifying ESBLs, AmpCs, and carbapenemases. Our method may be useful in clinical settings for the implementation of relevant infection control measures and for surveillance purposes.

Diversity and metallo-β-lactamase-producing genes in Pseudomonas aeruginosa strains isolated from filters of household water treatment systems

The microbiological quality of drinking water has long been a critical element in public health. Considering the high clinical relevance of Pseudomonas aeruginosa, we examined the filters of household water treatment systems for its presence and characteristics to determine the systems' efficiency in eliminating the bacteria. In total, filters of 50 household water treatment systems were examined. Microbiological and molecular methods were used for the detection and confirmation of P. aeruginosa isolates. Random Amplification of Polymorphic DNA-polymerase chain reaction (RAPD-PCR) was performed to detect similarities and differences among P. aeruginosa isolates. Combined disk (CD) method and double disk synergy test (DDST) were performed to detect metallo-beta-lactamase (MBL)-producing P. aeruginosa isolates. Finally, PCR was performed to detect MBL genes in MBL-producing strains. From the 50 analyzed systems, 76 colonies of P. aeruginosa were identified. In some systems, isolated bacteria from different filters harbored similar genetic profiles, indicating that these isolates may be able to pass through the filter and reach higher filters of the system. Phenotypic tests revealed 7 (9.2%) MBL-producing strains. Two isolates were positive for bla_VIM-1, whereas one isolate was positive for bla_NDM and bla_IMP-1. The wide distribution of resistant phenotypes and genetic plasticity of these bacteria in household water treatment systems indicate that resistance mechanisms circulate among P. aeruginosa isolates in the environment of the filtration systems. The presence of MBL-producing genes in these systems and P. aeruginosa as a potential reservoir of these resistance genes can be a major concern for public health.

Role of TEM-1 β-Lactamase in the Predominance of Ampicillin-Sulbactam-Nonsusceptible Escherichia coli in Japan

We investigated the epidemiology and resistance mechanisms of ampicillin-sulbactam-nonsusceptible Escherichia coli, focusing on the role of the TEM-1 β-lactamase. We collected all nonduplicate E. coli clinical isolates at 10 Japanese hospitals during December 2014 and examined their antimicrobial susceptibility, β-lactamases, TEM-1 transferability, TEM-1 β-lactamase activity, outer membrane protein profile, membrane permeability, and clonal genotypes. Among the 329 isolates collected, 95 were ampicillin-sulbactam nonsusceptible. Of these ampicillin-sulbactam-nonsusceptible isolates, β-lactamases conferring resistance to sulbactam, such as AmpC, were present in 33%. Hyperproduction of sulbactam-susceptible β-lactamases, TEMs with a strong promoter, were rare (5%). The remaining 59 isolates (62%) had only sulbactam-susceptible β-lactamases, including TEM-1 with a wild-type promoter (n = 28), CTX-Ms (n = 13), or both (n = 17). All 45 transconjugants from 96 donors with TEM-1 had higher ampicillin-sulbactam MICs (4 to 96 mg/liter) than the recipient (2 mg/liter). In donors with only TEM-1, TEM-1 activity correlated with the 50% inhibitory concentration of sulbactam and ampicillin-sulbactam MICs. The decreased membrane permeation of sulbactam was associated with an increased ampicillin-sulbactam MIC. The reduced permeation was partly attributable to deficient outer membrane proteins, which were observed in 57% of the ampicillin-sulbactam-nonsusceptible isolates with only TEM-1 and a wild-type promoter. Sequence type 131 (ST131) was the most common clonal type (52%). TEM-1 with a wild-type promoter primarily contributed to ampicillin-sulbactam nonsusceptibility in E. coli, with the partial support of other mechanisms, such as reduced permeation. Conjugative TEM-1 and the clonal spread of ST131 may contribute to the prevalence of Japanese ampicillin-sulbactam-nonsusceptible isolates.

A metallo-beta-lactamase producing Enterobacteriaceae outbreak from a contaminated tea dispenser at a children's hospital in Japan

An outbreak of metallo-β-lactamase (MBL) producing Klebsiella pneumoniae occurred at a children's hospital in Japan. MBL-producing K. pneumoniae was detected in tea dispenser in the hospital, the use of which was associated with the acquisition of the MBL-producing Enterobacteriaceae. The outbreak ceased after use of the tea dispenser was banned.

Epidemiology and risk factors for mortality in bloodstream infections: A single-center retrospective study in Japan

BACKGROUND

Few published data are available on the morbidity and mortality of bloodstream infections (BSIs) in Japan. We sought to investigate the epidemiology of BSIs, the involvement of antimicrobial resistance, and the factors that influence patient prognosis.

METHODS

This single-center study retrospectively evaluated patients who were found to have positive blood cultures at a tertiary teaching hospital between January 2012 and December 2016.

RESULTS

A total of 2,105 patients with BSIs were included; 1,786 survived and 319 died, and the 30-day mortality rate was 15.2% over the 5-year study period. BSIs caused by yeasts were independently associated with 30-day mortality. The 30-day mortality rate of BSIs caused by extended-spectrum beta lactamase-producing gram-negative bacteria was significantly higher than that of BSIs caused by nonproducing bacteria.

DISCUSSION

The differences in mortality may be caused by differences in the distribution of pathogens and in the delivery of health care.

CONCLUSIONS

This study reported epidemiology and antimicrobial resistance data of BSIs in Japan and identified several risk factors associated with 30-day mortality. National surveillance of BSIs is required in Japan for comparison with other countries.

Molecular characteristics of carbapenem-resistant Pseudomonas aeruginosa isolated from urine in Hyogo, Japan

OBJECTIVES

To investigate the molecular characteristics and epidemiology of metallo-β-lactamase-producing Pseudomonas aeruginosa from urine of urinary tract infection patients in Hyogo Prefecture, Japan.

METHODS

Carbapenem-resistant P. aeruginosa isolated from the urine of 21 urinary tract infection patients in three general hospitals in Hyogo Prefecture (Japan) were collected between 2007 and 2014. Their antibiotic susceptibilities, metallo-β-lactamase screening test, metallo-β-lactamase gene sequencing, multilocus sequence typing and repetitive-sequence-based polymerase chain reaction were determined for epidemiological analyses to investigate the genetic characteristics.

RESULTS

Out of 21 isolates, 13 (61.9%) were positive for metallo-β-lactamase. There were 11 (52.4%) isolates with IMP-1 in them, one (4.5%) isolate with IMP-7 and one (4.5%) isolate with VIM-1. Metallo-β-lactamase-positive isolates were mainly identified as ST235, and metallo-β-lactamase-negative isolates were STs 357, 277, 234, 439 and 639. Repetitive-sequence-based polymerase chain reaction showed metallo-β-lactamase-positive isolates were grouped in eight clusters, and ST235 isolates with IMP-1 from three hospitals belonging to the identical group I, the other ST235 isolates with IMP-7 and VIM-1 were from two hospitals belonging to group II.

CONCLUSIONS

Metallo-β-lactamase-positive P. aeruginosa of ST235 isolates with IPM-1 were mainly identified from the urine of urinary tract infection patients in Hyogo, Japan. A ST235 isolate with VIM-1 was found for the first time. Further investigation is necessary to follow the spread of metallo-β-lactamase-positive isolates.

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.

Spread of Clonally Related Escherichia coli Strains Harboring an IncA/C1 Plasmid Encoding IMP-8 and Its Recruitment into an Unrelated MCR-1-Containing Isolate

Ten IMP-8-producing Escherichia coli isolates were recovered from surveillance cultures of a neonatal intensive care unit; eight of the isolates were clonally related. A 168.2-kb bla_IMP-8 plasmid was fully sequenced, and it corresponded to the recently described IncA/C1-ST13 plasmid. This plasmid was detected in all isolates, even in those that were not clonally related. One unrelated isolate was also resistant to colistin and positive for mcr-1 This marker was located in a 62.7-kb IncI2 plasmid, which was also fully sequenced.

An outbreak of fluoroquinolone-resistant Pseudomonas aeruginosa ST357 harboring the exoU gene

Antimicrobial-resistant isolates of Pseudomonas aeruginosa collected from 2005 to 2014 in a university hospital in Kyoto, Japan, were retrospectively analyzed by multilocus sequence typing (MLST), exoenzyme genotype determination, integron characterization, and clinical associations. During the study, 1573 P. aeruginosa isolates were detected, and 41 of these were resistant to more than two classes of antimicrobial agents. Twenty-five (61.0%) isolates were collected from urine. All isolates were resistant to ciprofloxacin, 8 (19.5%) isolates showed resistance to imipenem/cilastatin, and 8 (19.5%) isolates showed resistance to meropenem. None of the isolates fulfilled the clinical criteria for multidrug-resistant P. aeruginosa. All isolates were negative in the metallo-β lactamase test. Thirty-six (87.8%) isolates were of the exoS^-exoU⁺ genotype and 5 (12.2%) isolates were of the exoS⁺exoU^- genotype. Among 36 exoS^-exoU⁺ isolates, 33 (80.5%) were ST357, and 3 (7.3%) were ST235. Five isolates of exoS⁺exoU^- were ST186, ST244, ST314, ST508, and ST512. Thirty-three isolates were positive for class 1 integrons and four different class 1 integrons were detected: aminoglycoside (2') adenyltransferase and chloramphenicol transporter (AadB+CmlA6), OXA-4 β-lactamase and aminoglycoside 3'-adenyltransferase (OXA4+AadA2), AadB alone, and aminoglycoside acetyltransferase alone (AacA31). Among the 41 patients from which the isolates originated, the most common underlying disease was cancer in 16 patients (39%), and 9 patients (22.0%) died during the hospitalization period. There was no statistical correlation between MLST, exoenzyme genotype, and patient mortality. The results indicated outbreaks of fluoroquinolone-resistant P. aeruginosa in immunocompromised patients mainly due to the propagation of potentially virulent ST357 isolates possessing the exoU⁺ genotype.

Thiol-Containing Metallo-β-Lactamase Inhibitors Resensitize Resistant Gram-Negative Bacteria to Meropenem

The prevalence of infections caused by metallo-β-lactamase (MBL) expressing Gram-negative bacteria has grown at an alarming rate in recent years. Despite the fact that MBLs can deactivate virtually all β-lactam antibiotics, there are as of yet no approved drugs available that inhibit their activity. We here examine the ability of previously reported thiol-based MBL inhibitors to synergize with meropenem and cefoperazone against a panel of Gram-negative carbapenem-resistant isolates expressing different β-lactamases. Among the compounds tested, thiomandelic acid 3 and 2-mercapto-3-phenylpropionic acid 4 were found to efficiently potentiate the activity of meropenem, especially against an imipenemase (IMP) producing strain of K. pneumoniae. In light of the zinc-dependent hydrolytic mechanism employed by MBLs, biophysical studies using isothermal titration calorimetry were also performed, revealing a correlation between the synergistic activity of thiols 3 and 4 and their zinc-binding ability with measured K_d values of 9.8 and 20.0 μM, respectively.

Occurrence of antimicrobial resistance bacteria in the Yodo River basin, Japan and determination of beta-lactamases producing bacteria

Antimicrobial resistant bacteria are widespread in aquatic environments. The aim of the present study was to obtain information on the occurrence of bacteria with antimicrobial resistance and their multiple antimicrobial resistance (MAR) patterns in a river basin in Japan. In addition, the occurrence of fecal bacteria producing extended-spectrum beta-lactamases (ESBLs) and metallo-beta-lactamase (MBL) in the aquatic environment was determined. Among the Escherichia coli isolates recovered from river samples upstream, 55% isolates were resistant to at least one antimicrobial and 18% were MAR. Among the E. coli isolates recovered from wastewater treatment plant (WWTP) effluent samples, 74% isolates were resistant to at least one antimicrobial and 46% were MAR. These findings suggest that the presence of WWTP effluent will increase the degree of contamination with MAR in the aquatic environment. Among the ampicillin-resistant isolates recovered from river samples, 21% isolates were judged as ESBL-producing and none (0%) was judged as MBL-producing. Among the ampicillin-resistant isolates recovered from WWTP effluent samples, 21% were judged as ESBL-producing and 1% was judged as MBL-producing. As for the hospital wastewater samples, 48% were judged as ESBL-producing and 3% were judged as MBL-producing. The percentage of ESBLs and MBL production was highest in hospital wastewater samples. All of the ESBL-producing isolates detected had resistance to ampicillin, cephazolin, and cefpodoxime and many ESBL-producers had resistance not only to beta-lactams but also to other kinds of antimicrobials such as aminoglycosides and quinolones. The frequency of detection of MBL-producers was much lower than that of ESBL-producers and MBL-producers were not detected in the river samples. However, the detection in WWTP effluent samples indicated that bacteria with MBL were present downstream of the WWTP at low concentrations. Thus, ESBLs and MBL have already been spread around aquatic environments.

Inhibition of New Delhi Metallo-β-Lactamase 1 (NDM-1) Producing Escherichia coli IR-6 by Selected Plant Extracts and Their Synergistic Actions with Antibiotics

Improper use of antibiotics has led to a great concern in the development of pathogenic microbial resistance. New Delhi metallo-β-lactamase 1 (NDM-1) producing bacteria are resistant to most of the β-lactam antibiotics, and so far, no new compounds have been clinically tested against these bacteria. In this study, ethanol extracts from the leaves of 240 medicinal plant species were screened for antibacterial activity against an NDM-1 Escherichia coli strain. The extracts that showed antibacterial activity were then tested for minimum inhibitory concentrations (MICs) and zones of inhibition. The extract from Combretum albidum G. Don, Hibiscus acetosella Welw. ex Hiern, Hibiscus cannabinus L., Hibiscus furcatus Willd., Punica granatum L., and Tamarindus indica L. showed bactericidal activity between 5 and 15 mg/ml and the MIC was between 2.56 and 5.12 mg/ml. All six plant extracts inhibited activity of the NDM-1 enzyme in vitro, and the IC50 value ranged between 0.50 and 1.2 ng/μl. Disruption of bacterial cell wall integrity by the plant extracts was clearly visible with scanning electron microscopy. Increases in membrane permeability caused 79.4–89.7% bacterial cell deaths as investigated by fluorescence-activated cell sorting. All the plant extracts showed synergistic effects when combined with colistin [fractional inhibitory concentration (ΣFIC) = 0.125–0.375], meropenem (ΣFIC = 0.09–0.313), and tetracycline (ΣFIC = 0.125–0.313). Thus, the plant extracts can be fractionated for the identification of active compounds, which could be used as new antibacterial compounds for the development of drugs against NDM-1 E. coli in addition to their use in combination therapy.

Molecular epidemiological survey of bacteremia by multidrug resistant Pseudomonas aeruginosa: the relevance of intrinsic resistance mechanisms

The bacterial factors associated with bacteremia by multidrug-resistant and extensively drug-resistant P. aeruginosa, including overexpression of efflux pumps, AmpC overproduction, and loss/alteration of the OprD porin in isolates that are non-Metallo-β-Lactamase producing were analyzed in a retrospective study. Molecular analyses included strain typing by Pulsed Field Gel Electrophoresis and identification of key genes via qualitative and quantitative PCR-based assays. Previous use of carbapenems and tracheostomy was independently associated with the development of bacteremia by extensively drug-resistant and multidrug-resistant strains of P. aeruginosa. A high consumption of antimicrobials was observed, and 75.0% of the isolates contained amplicons with the blaSPM-1 and blaVIM genes. Of the 47 non-Metallo-β-Lactamase isolates, none had another type of carbapenemase. However, the isolates exhibited high rates of hyperproduction of AmpC, loss of the OprD porin (71.4%) and the presence of MexABOprM (57.1%) and MexXY (64.3%). This study suggests that in non-Metallo-β-Lactamase isolates, the association of intrinsic resistance mechanisms could contributes to the expression of multidrug-resistant/extensively drug-resistant phenotypes.

Evaluation of commercial phenotypic assays for the detection of IMP- or New Delhi metallo-β-lactamase-producing Enterobacteriaceae isolates in Japan

OBJECTIVES

This study was designed to evaluate the sodium mercaptoacetic acid double disk synergy test (SMA-DDST), the Etest metallo-β-lactamase (MBL) MP/MPI (Etest MP/MPI), and the Mastdiscs ID Carbapenemase Detection Disc Set (MAST-CDS) for the detection of MBL-producing Enterobacteriaceae isolates in Japan.

METHODS

Fifty-one clinical isolates and four reference strains were tested. These isolates included 40, 4, and 11 IMP-, New Delhi MBL (NDM)-, and non-MBL-producers, respectively. SMA-DDST was performed with meropenem (MEPM)-containing disks.

RESULTS

Sensitivities were 38/44 (86%), 40/44 (91%), and 15/44 (34%), and the cost ratio was 1:9.4:3.8 for MEPM-SMA-DDST:Etest MP/MPI:MAST-CDS, respectively. The specificity was 11/11 (100%) for all assays. MEPM-SMA-DDST detected IMP-producing isolates with high sensitivity (38/40; 95%), but the assay was inadequate for NDM-producing isolates (0/4; 0%). The Etest MP/MPI detected both IMP- (36/40; 90%) and NDM-producing isolates (4/4; 100%), but was the most expensive. MAST-CDS detected IMP-producing isolates with low sensitivity (11/40; 28%), but the assay worked well for NDM-producing isolates (4/4; 100%).

CONCLUSIONS

Our results indicated that MEPM-SMA-DDST was the most cost-effective assay for the detection of IMP-producing isolates. Therefore, we conclude that MEPM-SMA-DDST is the optimal available assay for clinical first-line screening in IMP-endemic areas such as Japan. However, this assay could not detect NDM-producing isolates, whereas the Etest MP/MPI and MAST-CDS could. When MEPM-SMA-DDST is negative, the Etest MP/MPI and MAST-CDS could be used to obtain supportive data and prevent detection failure for NDM-producing isolates.

Antimicrobial Resistance of Pseudomonas aeruginosa Isolated from Dogs and Cats in Primary Veterinary Hospitals in Japan

We collected 200 Pseudomonas aeruginosa isolates from dogs and cats in primary veterinary hospitals in Japan to investigate their antimicrobial resistance. Resistance rates against ciprofloxacin, cefotaxime, gentamicin, amikacin, and fosfomycin were 9%, 12.5%, 4.5%, 2.5%, and 35.5%, respectively. One strain displayed resistance (0.5%) to ceftazidime. We did not detect any imipenem-resistant or multidrug-resistant P. aeruginosa strains as defined by the Japanese Ministry of Health, Labour, and Welfare Law Concerning the Prevention of Infections and Medical Care for Patients with Infections. In addition, we did not find any P. aeruginosa isolates that produced metallo-β-lactamase, the aminoglycoside 6'-N-acetyltransferase AAC(6')-Iae, or the aminoglycoside acetyltransferase AAC(6')-Ib.

Carbapenem-Resistant Enterobacteriaceae

Carbapenem-resistant Enterobacteriaceae (CRE) have emerged as a major threat. Commonly used antibiotics are generally inactive against CRE. Therefore, timely detection of CRE is of paramount importance. Among CRE, those producing carbapenem-hydrolyzing β-lactamase enzymes (carbapenemase-producing Enterobacteriaceae) are particularly of concern because they tend to spread, and treatment is difficult. The carbapenemase groups most commonly encountered include KPC, NDM, and OXA-48. Treatment options are limited and include combinations of polymyxins, tigecycline, aminoglycosides, or carbapenems; newer agents with activity against CRE and better safety profiles are becoming available and will likely emerge as the preferred therapy.

Sensitivity to Antimicrobial Drugs of Pseudomonas Aeruginosa Extreme-Resistant Strains Isolated in the Major Hospitals of Central Kazakhstan

AIM:

The article presents the current data on the sensitivity of the main 37 strains of eXtremaly Drugs Resistance (XDR) category to anti-pseudomonas drugs.

MATERIAL AND METHODS:

The strains were collected during the prospective multicenter study in large multidisciplinary hospitals of Central Kazakhstan. Susceptibility to antimicrobial drugs was carried out by disk method and the serial dilution method with the interpretation of the results according to EUCAST criteria. Detection of carbapenemases gene of VIM, IMP, NDM and GES classes was carried out by PCR method using the commercial kits.

RESULTS:

All identified carbapenemases were sorted to VIM class and accounted for 63.64%. Resistance to aminoglycoside drugs exceeded 80%. All the strains were susceptible to polymyxin.

CONCLUSION:

Thus, at the present stage the circulation of P. aeruginosa strains of XDR category continues in major hospitals in Kazakhstan. The strains remain sensitiveness only to polymyxin.

Fatal sepsis caused by multidrug-resistant Bacteroides fragilis, harboring a cfiA gene and an upstream insertion sequence element, in Japan

Here, we report a case of fatal sepsis resulting from an intra-abdominal infection caused by a Bacteroides fragilis strain containing a CfiA4 metallo-β-lactamase and an upstream insertion sequence (IS) element. Meropenem was used as empiric therapy for septic shock as a result of the intra-abdominal infection, although two rounds of carbapenem treatment had been administered previously. B. fragilis was isolated from two anaerobic blood culture bottles 4 days after the onset of septic shock. Susceptibility testing revealed that the isolate was non-susceptible to all tested agents except metronidazole and tigecycline. The isolate gave a positive result in ethylenediaminetetraacetic acid and carbapenem inactivation tests, but a negative result in a double-disk synergy test using sodium mercaptoacetate. Next-generation whole-genome sequencing indicated the presence of the cfiA4, emrG and emrF genes. PCR indicated the presence of an IS element upstream of the cifA4 gene. Although carbapenem-resistant B. fragilis isolates have previously been reported, clinical sepsis by this organism is considered rare. In Japan, as in most countries worldwide, routine susceptibility testing and the detection of metallo-β-lactamases is not carried out in anaerobic organisms, including B. fragilis. The emergence of carbapenem resistance during therapy should be monitored, as B. fragilis strains containing the cfiA gene show decreased sensitivity during carbapenem therapy. Therefore, susceptibility testing and appropriate antibiotic stewardship are required in cases of anaerobic bacterial infections.

Carbapenem-resistant Pseudomonas aeruginosa: association with virulence genes and biofilm formation

Pseudomonas aeruginosa is an opportunistic pathogen that causes frequently nosocomial infections, currently becoming more difficult to treat due to the various resistance mechanisms and different virulence factors. The purpose of this study was to determine the risk factors independently associated with the development of bacteremia by carbapenem-resistant P. aeruginosa, the frequency of virulence genes in metallo-β-lactamases producers and to evaluate their ability to produce biofilm. We conducted a case–control study in the Uberlândia Federal University – Hospital Clinic, Brazil. Polymerase Chain Reaction was performed for metallo-β-lactamases and virulence genes. Adhesion and biofilm assays were done by quantitative tests. Among the 157 strains analyzed, 73.9% were multidrug-resistant, 43.9% were resistant to carbapenems, 16.1% were phenotypically positive for metallo-β-lactamases, and of these, 10.7% were positive for bla_SPM gene and 5.3% positive for bla_VIM. The multivariable analysis showed that mechanical ventilation, enteral/nasogastric tubes, primary bacteremia with unknown focus, and inappropriate therapy were independent risk factors associated with bacteremia. All tested strains were characterized as strongly biofilm producers. A higher mortality was found among patients with bacteremia by carbapenem-resistant P. aeruginosa strains, associated independently with extrinsic risk factors, however it was not evident the association with the presence of virulence and metallo-β-lactamases genes.

Carbapenem Susceptibility and Multidrug-Resistance in Pseudomonas aeruginosa Isolates in Egypt

Background

Resistant Pseudomonas aeruginosa is a serious concern for antimicrobial therapy, as the common isolates exhibit variable grades of resistance, involving beta-lactamase enzymes, beside native defense mechanisms.

Objectives

The present study was designed to determine the occurrence of Metallo-β- Lactamases (MBL) and Amp C harboring P. aeruginosa isolates from Suez Canal university hospital in Ismailia, Egypt.

Methods

A total of 147 P. aeruginosa isolates, recovered from 311 patients during a 10-month period, were collected between May 2013 and February 2014; the isolates were collected from urine, wound and sputum. Minimum inhibitory concentration (MIC) determined by agar dilution methods was ≥2 μg/mL for meropenem and imipenem. Identification of P. aeruginosa was confirmed using API 20NE. Metallo-β- Lactamases and Amp C were detected based on different phenotypic methods.

Results

Overall, 26.5% of P. aeruginosa isolates (39/147) were carbapenem resistant isolates. Furthermore, 64.1% (25/39) were MBL producers, these isolates were screened by the combined disc and disc diffusion methods to determine the ability of MBL production. Both MBL and Amp C harbored P. aeruginosa isolates were 28% (7/25). Sixty-four percent of P. aeruginosa isolates were multidrug resistant (MDR) (16/25). The sensitivity toward polymyxin, imipenem, norfloxacin, piperacillin-tazobactam and gentamicin was 99%, 91%, 88%, 82% and 78%, respectively. The resistance rate towards cefotaxime, ceftazidime, cefepime, aztreonam and meropenem was 98.6%, 86%, 71.4%, 34% and 30%, respectively.

Conclusions

Multidrug resistance was significantly associated with MBL production in P. aeruginosa. Early detection of MBL-producing P. aeruginosa and hospital antibiotic policy prescription helps proper antimicrobial therapy and avoidance of dissemination of these multidrug resistance isolates.