IMP-27, a Unique Metallo-β-Lactamase Identified in Geographically Distinct Isolates of Proteus mirabilis

Evolution of β-Lactam Antibiotic Resistance in Proteus Species: From Extended-Spectrum and Plasmid-Mediated AmpC β-Lactamases to Carbapenemases

The management of infectious diseases has proven to be a daunting task for clinicians worldwide, and the rapid development of antibiotic resistance among Gram-negative bacteria is making it even more challenging. The first-line therapy is empirical, and it most often comprises β-lactam antibiotics. Among Gram-negative bacteria, Proteus mirabilis, an important community and hospital pathogen associated primarily with urinary tract and wound infection, holds a special place. This review's aim was to collate and examine recent studies investigating β-lactam resistance phenotypes and mechanisms of Proteus species and the global significance of its β-lactam resistance evolution. Moreover, the genetic background of resistance traits and the role of mobile genetic elements in the dissemination of resistance genes were evaluated. P. mirabilis as the dominant pathogen develops resistance to expanded-spectrum cephalosporins (ESC) by producing extended-spectrum β-lactamases (ESBL) and plasmid-mediated AmpC β-lactamases (p-AmpC). β-lactamase-mediated resistance to carbapenems in Enterobacterales, including Proteus spp., is mostly due to expression of carbapenemases of class A (KPC); class B (metallo-β-lactamases or MBLs of IMP, VIM, or NDM series); or class D or carbapenem-hydrolyzing oxacillinases (CHDL). Previously, a dominant ESBL type in P. mirabilis was TEM-52; yet, lately, it has been replaced by CTX-M variants, particularly CTX-M-14. ESC resistance can also be mediated by p-AmpC, with CMY-16 as the dominant variant. Carbapenem resistance in Proteus spp. is a challenge due to its intrinsic resistance to colistin and tigecyclin. The first carbapenemases reported belonged to class B, most frequently VIM-1 and NDM-5. In Europe, predominantly France and Belgium, a clonal lineage positive for OXA-23 CHDL spreads rapidly undetected, due to its low-level resistance to carbapenems. The amazing capacity of Proteus spp. to accumulate a plethora of various resistance traits is leading to multidrug or extensively drug-resistant phenotypes.

Performance evaluation of the Streck ARM-DⓇ Kit, β-Lactamase for molecular detection of acquired β-lactamase genes

OBJECTIVES

Despite clinical relevance, commercially available molecular tools for accurate β-lactamase detection are limited. In this study, we evaluated the performance of the ARM-DⓇ Kit, β-Lactamase, a commercially available multiplex PCR assay designed to detect nine β-lactamase genes, including the five major plasmid-mediated carbapenemases, ESBL and AmpC genes circulating in the United States.

METHODS

A diverse collection of 113 Gram-negative isolates, including 42 with multiple β-lactamases genes, was selected from the U.S. Centers for Disease Control and Prevention (CDC) & Food and Drug Administration (FDA) Antimicrobial Resistance Isolate Bank, to represent the most frequently detected bacterial species carrying plasmid-mediated β-lactam resistance genes.

RESULTS

Results were compared with whole genome sequence data. Of 164 β-lactamase gene targets with 49 unique variants, all were detected correctly without any cross-reactivity. The sensitivity and specificity were 100% (164/164) and 99.9% (852/853), respectively.

CONCLUSION

The ARM-DⓇ Kit, β-Lactamase detected a wide range of β-lactamase genotypes at a low upfront cost. The Streck assay represents a suitable, comprehensive tool for the detection of key β-lactamase resistance genes of public health concern in the United States.

Functional and structural analyses of IMP-27 metallo-β-lactamase: evolution of IMP-type enzymes to overcome Zn(II) deprivation

IMP-type metallo-β-lactamases are di-Zn(II) enzymes that can inactivate a wide range of bicyclic β-lactam agents used in clinical practice. IMP-27 shares 82% amino acid sequence identity with IMP-1, the first IMP-type enzyme identified. Herein, we conducted structural determination, kinetic, and chelating agent resistance analyses of IMP-27. Once determined, IMP-27 was then compared to its mutant, namely, G262S, and IMP-1. Crystallographic structural analysis of IMP-27 showed an overall structure comparable to that of IMP-1 and other IMP-type enzymes; the positions of the zinc (Zn) ions varied across enzymes. Kinetic analysis showed that IMP-27 had lower catalytic efficiency against penicillins, ceftazidime, cephalexin, and imipenem than IMP-1; however, it had higher affinity and catalytic efficiency against meropenem, especially in the presence of Zn(II). This suggests that the catalytic site of IMP-27 is optimized to hydrolyze meropenem during molecular evolution at the expense of catalytic efficiency against penicillins. However, Zn(II) content analysis after EDTA treatment revealed no significant difference between enzymes. Moreover, analysis of IMP-27 mutants indicated that the differences in kinetic properties and chelator resistance between IMP-1 and IMP-27 were mainly due to an amino acid substitution at position 262.IMPORTANCEThe residue at position 262 has been reported as a key determinant of substrate specificity in IMP-type enzymes. Among more than 80 IMP-type metallo-β-lactamase (MBL) variants, IMP-27 was the first reported IMP-type MBL isolated from Proteus mirabilis. This enzyme has a glycine residue at position 262, which is occupied by serine in IMP-1. Compared with IMP-1, IMP-27 had a significantly higher affinity and catalytic efficiency against meropenem and improved metal-binding capacity, maintaining its activity under Zn(II)-limited conditions better than IMP-1. The analysis of the IMP-27 mutants indicated that differences between IMP-27 and IMP-1 were mainly due to an amino acid substitution at position 262. In the case of IMP-27, the G262S mutation optimized the catalytic site of IMP-27 for meropenem hydrolysis, at the expense of catalytic efficiency against penicillins.

Correlation between the spread of IMP-producing bacteria and the promoter strength of blaIMP genes

The first report of transmissible carbapenem resistance encoded by blaIMP-1 was discovered in Pseudomonas aeruginosa GN17203 in 1988, and blaIMP-1 has since been detected in other bacteria, including Enterobacterales. Currently, many variants of blaIMPs exist, and point mutations in the blaIMP promoter have been shown to alter promoter strength. For example, the promoter (Pc) of blaIMP-1, first reported in P. aeruginosa GN17203, was a weak promoter (PcW) with low-level expression intensity. This study investigates whether point mutations in the promoter region have helped to create strong promoters under antimicrobial selection pressure. Using bioinformatic approaches, we retrieved 115 blaIMPs from 14,529 genome data of Pseudomonadota and performed multiple alignment analyses. The results of promoter analysis of the 115 retrieved blaIMPs showed that most of them used the Pc located in class 1 integrons (n = 112, 97.4%). The promoter analysis by year revealed that the blaIMP population with the strong promoter, PcS, was transient. In contrast, the PcW-TG population, which had acquired a TGn-extended -10 motif in PcW and had an intermediate promoter strength, gradually spread throughout the world. An inverse correlation between Pc promoter strength and Intl1 integrase excision efficiency has been reported previously [1]. Because of this trade-off, it is unlikely that blaIMPs with strong promoters will increase rapidly, but the possibility that promoter strength will increase with the use of other integrons cannot be ruled out. Monitoring of the blaIMP genes, including promoter analysis, is necessary for global surveillance of carbapenem-resistant bacteria.

Worldwide trend discovery of structural and functional relationship of metallo-β-lactamase for structure-based drug design: A bibliometric evaluation and patent analysis

Metallo-β-lactamase (MBL) is an enzyme produced by clinically important bacteria that can inactivate many commonly used antibiotics, making them a significant concern in treating bacterial infections and the risk of having high antibiotic resistance issues among the community. This review presents a bibliometric and patent analysis of MBL worldwide research trend based on the Scopus and World Intellectual Property Organization databases in 2013-2022. Based on the keywords related to MBL in the article title, abstract, and keywords, 592 research articles were retrieved for further analysis using various tools such as Microsoft Excel to determine the frequency analysis, VOSviewer for bibliometric networks visualization, and Harzing's Publish or Perish for citation metrics analysis. Standard bibliometric parameters were analysed to evaluate the field's research trend, such as the growth of publications, topographical distribution, top subject area, most relevant journal, top cited documents, most relevant authors, and keyword trend analysis. Within 10 years, MBL discovery has shown a steady and continuous growth of interest among the community of researchers. United States of America, China, and the United Kingdom are the top 3 countries contribute high productivity to the field. The patent analysis also shows several impactful filed patents, indicating the significance of development research on the structural and functional relationship of MBL for an effective structure-based drug design (SBDD). Developing new MBL inhibitors using SBDD could help address the research gap and provide new successful therapeutic options for treating MBL-producing bacterial infections.

Whole-genome sequencing provides insights into a novel species: Providencia hangzhouensis associated with urinary tract infections

Providencia rettgeri is a clinically significant opportunistic pathogen that is involved in urinary tract infections. Due to the resolution limitations of identification, distinguishing P. rettgeri from closely related species is challenging by commercial biochemical test systems. Here, we first reported a novel species, Providencia hangzhouensis, which had been misidentified as P. rettgeri. Exhibiting ≤91.97% average nucleotide identity (ANI) and ≤46.10% in silico DNA-DNA hybridization values with all known Providencia species, P. hangzhouensis falls well beneath the established species-defining thresholds. We conducted a population genomics analysis of P. hangzhouensis isolates worldwide. Our study revealed that P. hangzhouensis has emerged in many countries and has formed several transmission clusters. We found that P. hangzhouensis shared the highest ANI values (91.54% and 91.97%) with P. rettgeri and P. huaxiensis, respectively. The pan-genome analysis revealed that these three species possessed a similar component of pan-genomes. Two genes associated with metabolism, folE2 and ccmM, were identified to be specific to P. hangzhouensis. Furthermore, we also observed that carbapenem-resistance genes frequently occur in P. hangzhouensis with the blaIMP-27 being the most prevalent (46.15%; 36/78). The emergence of P. hangzhouensis is often accompanied by extended-spectrum β-lactamase and carbapenem-resistance genes, and calls for tailored surveillance of this species as a clinically relevant species in the future. IMPORTANCE Our study has identified and characterized a novel species, Providencia hangzhouensis, which is associated with urinary tract infections and was previously misidentified as Providencia rettgeri. Through this study, we have identified specific genes unique to P. hangzhouensis, which could serve as marker genes for rapid PCR identification. Additionally, our findings suggest that the emergence of P. hangzhouensis is often accompanied by extended-spectrum β-lactamase and carbapenem-resistance genes, emphasizing the need for attention to clinical management and the importance of accurate species identification and proper drug use.

Evaluation of the NG-Test CARBA 5 Lateral Flow Assay with an IMP-27-Producing Morganella morganii and Other Morganellaceae

An isolate of Morganella morganii (MMOR1) that tested susceptible to 3rd/4th-generation cephalosporins and intermediate to meropenem was characterized as positive for NDM and IMP carbapenemases by NG-Test CARBA 5. Our objective was to further investigate this result, given the inconsistent susceptibility profile and unusual epidemiological profile for our region. The MMOR1 isolate was retested for antimicrobial susceptibilities and characterized for carbapenemase production. MMOR1 tested susceptible to ceftazidime, ceftriaxone, cefepime, aztreonam, and ertapenem, and intermediate to meropenem and imipenem. The isolate tested positive by carbapenem inactivation method (CIM) and CIM+EDTA (eCIM) testing, indicating metallo-β-lactamase production. The isolate tested negative for all carbapenemase genes on Xpert Carba-R, but positive for IMP on repeat testing of NG-Test CARBA 5. Whole-genome sequencing revealed MMOR1 contained blaIMP-27, but no other carbapenemase genes. Additional testing with NG-Test CARBA 5 revealed a false-positive NDM band when the assay was overloaded with test inoculum. Supplementary isolates were tested with an overloaded inoculum (n = 6 M. morganii; n = 1 P. mirabilis; n = 1 IMP-27-producing P. rettgeri; n = 1 IMP-1-producing E. coli; n = 1 K. pneumoniae), and two non-carbapenemase-producing carbapenem non-susceptible M. morganii also generated a false-positive NDM band; though, this was not universal among this species. A dual IMP+/NDM+ M. morganii is an unusual result that should prompt additional investigation, especially in nonendemic regions and when the susceptibility profile is incompatible. IMP-27 is not detected by Xpert Carba-R but is variably detected by NG-Test CARBA 5. The microorganism inoculum used for NG-Test CARBA 5 must be carefully controlled for accurate results. IMPORTANCE The detection of carbapenemase-producing carbapenem-resistant Enterobacterales (CP-CRE) is an important function of the clinical microbiology laboratory, where positive identifications have immediate implications for infection control and surveillance strategies in the inpatient setting and can inform appropriate selection of therapy among the various novel anti-CP-CRE agents. NG-Test CARBA 5 is a relatively new lateral flow assay used for detection of carbapenemases in CP-CRE. Here, we describe the characterization of a Morganella morganii isolate that generated a false-positive NDM carbapenemase detection by this assay, and perform bacterial test inoculum experiments with additional isolates to further investigate a cause of false-positive results using the NG-Test CARBA 5. While a lateral flow assay like the NG-Test CARBA 5 is a very desirable test format for clinical laboratories, there are pitfalls to avoid when performing this test and interpreting results, including recognizing an overloaded test assay, which could lead to false-positive results.

Carbapenemase production among less-common Enterobacterales genera: 10 US sites, 2018

Background

Historically, United States’ carbapenem-resistant Enterobacterales (CRE) surveillance and mechanism testing focused on three genera: Escherichia, Klebsiella, and Enterobacter (EsKE); however, other genera can harbour mobile carbapenemases associated with CRE spread.

Objectives

From January through May 2018, we conducted a 10 state evaluation to assess the contribution of less common genera (LCG) to carbapenemase-producing (CP) CRE.

Methods

State public health laboratories (SPHLs) requested participating clinical laboratories submit all Enterobacterales from all specimen sources during the surveillance period that were resistant to any carbapenem (Morganellaceae required resistance to doripenem, ertapenem, or meropenem) or were CP based on phenotypic or genotypic testing at the clinical laboratory. SPHLs performed species identification, phenotypic carbapenemase production testing, and molecular testing for carbapenemases to identify CP-CRE. Isolates were categorized as CP if they demonstrated phenotypic carbapenemase production and ≥1 carbapenemase gene (bla_KPC, bla_NDM, bla_VIM, bla_IMP, or bla_OXA-48-like) was detected.

Results

SPHLs tested 868 CRE isolates, 127 (14.6%) were from eight LCG. Overall, 195 (26.3%) EsKE isolates were CP-CRE, compared with 24 (18.9%) LCG isolates. LCG accounted for 24 (11.0%) of 219 CP-CRE identified. Citrobacter spp. was the most common CP-LCG; the proportion of Citrobacter that were CP (11/42, 26.2%) was similar to the proportion of EsKE that were CP (195/741, 26.3%). Five of 24 (20.8%) CP-LCG had a carbapenemase gene other than bla_KPC.

Conclusions

Participating sites would have missed approximately 1 in 10 CP-CRE if isolate submission had been limited to EsKE genera. Expanding mechanism testing to additional genera could improve detection and prevention efforts.

Introduction of novel putative immunogenic targets against Proteus mirabilis using a reverse vaccinology approach

Multi-drug resistance of Proteus mirabilis, a frequent cause of catheter-associated urinary tract infections, renders ineffective treatment. Therefore, new advanced strategies are needed to overcome it. In the meantime, vaccination may be the most effective and promising method. In this study antigenicity, allergenicity, subcellular localization, human homology, B-cell epitopes and MHC-II binding sites, conserved domains and protein-protein interactions were predicted using different reverse vaccinology methods and bioinformatics databases to find new putative immunogenic targets against P. mirabilis. Finally, 5 putative immunogenic targets against P. mirabilis were identified. Considering all criteria, QKQ94350.1 (Cell envelope opacity-associated protein A), QKQ94681.1 (Porin), QKQ95001.1 (TonB-dependent hemoglobin/ transferrin/ lactoferrin family receptor), QKQ95221.1 (AsmA) and QKQ94335.1 (N-acetylmuramoyl-L-alanine amidase) are excellent putative immunogenic targets. Finally, a multi-epitope vaccine was designed using the conserved linear epitopes of two OMPs (QKQ94681.1 and QKQ95001.1) and N-acetylmuramoyl-L-alanine amidase (QKQ94335.1), which have promising properties for immunization. These findings can simplify the development of efficient vaccines against P. mirabilis.

Metallo-β-lactamases in the Age of Multidrug Resistance: From Structure and Mechanism to Evolution, Dissemination, and Inhibitor Design

Antimicrobial resistance is one of the major problems in current practical medicine. The spread of genes coding for resistance determinants among bacteria challenges the use of approved antibiotics, narrowing the options for treatment. Resistance to carbapenems, last resort antibiotics, is a major concern. Metallo-β-lactamases (MBLs) hydrolyze carbapenems, penicillins, and cephalosporins, becoming central to this problem. These enzymes diverge with respect to serine-β-lactamases by exhibiting a different fold, active site, and catalytic features. Elucidating their catalytic mechanism has been a big challenge in the field that has limited the development of useful inhibitors. This review covers exhaustively the details of the active-site chemistries, the diversity of MBL alleles, the catalytic mechanism against different substrates, and how this information has helped developing inhibitors. We also discuss here different aspects critical to understand the success of MBLs in conferring resistance: the molecular determinants of their dissemination, their cell physiology, from the biogenesis to the processing involved in the transit to the periplasm, and the uptake of the Zn(II) ions upon metal starvation conditions, such as those encountered during an infection. In this regard, the chemical, biochemical and microbiological aspects provide an integrative view of the current knowledge of MBLs.

Emergence of Morganellaceae Harboring bla IMP-27 Metalloenzyme in Canada

In 2018 to 2019, PCR for carbapenemases in routine Gram-negative isolates submitted to the National Microbiology Laboratory revealed an increase in IMP-type metalloenzyme-positive isolates, mostly among Morganellaceae. Whole-genome sequencing revealed that 23 Morganellaceae harbored bla_IMP-27 within a chromosomal Tn7 element. Phylogenomics indicated diversity of isolates but also the presence of a few clonal isolates dispersed geographically. These isolates may be difficult to detect due to carbapenem susceptibility and false-negative results in phenotypic testing.

IMPORTANCE Over the last decade or so, the frequency of isolation of clinical carbapenemase-producing organisms (CPOs) has increased among health care-associated infections. This may seriously compromise antimicrobial therapy, as carbapenems are considered the last line of defense against these organisms. The ability of carbapenemases to hydrolyze most β-lactams in addition to the co-occurrence of mechanisms of resistance to other classes of antimicrobials in CPOs can leave few options for treating infections. The class B metalloenzymes are globally distributed carbapenemases, and the most commonly found include the NDM, VIM, and IMP types. Our study describes a sudden emergence of IMP-27-harboring Morganellaceae during 2018 to 2019 in Canada. There is a paucity of literature on IMP-27 isolates, and our data bolster the information on the genetic context, antimicrobial profiles, and phylogenomics of this group of CPOs.

Abundance of New Delhi Metallo-β-Lactamase-Producing Acinetobacter, Escherichia, Proteus, and Pseudomonas spp. in Mahananda and Karala Rivers of India

In this study, we report a high incidence of New Delhi metallo-β-lactamase (NDM)-producing and ampicillin-catabolizing bacteria within carbapenem-resistant bacterial populations in the waters of two important rivers, Mahananda and Karala, bisecting two most populous towns, Siliguri and Jalpaiguri, respectively, in the northern West Bengal, India. Isolates producing NDM belonged to four genera, Acinetobacter, Escherichia, Proteus, and Pseudomonas; among which few were phylogenetically determined as putatively novel species. Class 1 integrons with the frequent presence of aadA and aac(6')-Ib gene cassettes in 50% of NDM-bearing isolates are indicative of possible selective pressures generated out of unregulated use of streptomycin, in agriculture practiced by the cultivators and tea planters living in locales drained by these two rivers, in their up- and downstream, and amikacin in the most crowded government-sponsored "sadar" and district hospitals of Siliguri and Jalpaiguri. NDM-delivering bacteria in rivers have genuine consequences for city inhabitants who are dependent on public water and sanitation facilities. Standard reconnaissance of antibiotic resistance, consolidating ecological sampling just as the assessment of clinical isolates, should be set up as a need.

Carbapenemase-Producing Gram-Negative Bacteria from American Crows in the United States

Wild corvids were examined for the presence of carbapenemase-producing Gram-negative bacteria in the United States. A total of 13 isolates were detected among 590 fecal samples of American crow; 11 Providencia rettgeri isolates harboring blaIMP-27 on the chromosome as a class 2 integron gene cassette within the Tn7 transposon, 1 Klebsiella pneumoniae ST258 isolate carrying blaKPC-2 on a pKpQIL-like plasmid as a part of Tn4401a, and 1 Enterobacter bugandensis isolate with blaIMI-1 located within EcloIMEX-2.

Profile of Enterobacteria Resistant to Beta-Lactams

A serious emerging problem worldwide is increased antimicrobial resistance. Acquisition of coding genes for evasion methods of antimicrobial drug mechanisms characterizes acquired resistance. This phenomenon has been observed in Enterobacteriaceae family. Treatment for bacterial infections is performed with antibiotics, of which the most used are beta-lactams. The aim of this study was to correlate antimicrobial resistance profiles in Enterobacteriaceae by phenotypic methods and molecular identification of 14 beta-lactamase coding genes. In this study, 70 exclusive isolates from Brazil were used, half of which were collected in veterinary clinics or hospitals Phenotypic methodologies were used and real-time PCR was the molecular methodology used, through the Sybr Green system. Regargding the results found in the tests it was observed that 74.28% were resistant to ampicillin, 62.85% were resistant to amoxicillin associated with clavalunate. The mechanism of resistance that presented the highest expression was ESBL (17.14%). The genes studied that were detected in a greater number of species were blaGIM and blaSIM (66.66% of the samples) and the one that was amplified in a smaller number of samples was blaVIM (16.66%). Therefore, high and worrying levels of antimicrobial resistance have been found in enterobacteria, and a way to minimize the accelerated emergence of their resistance includes developing or improving techniques that generate diagnoses with high efficiency and speed.

Genetics of Acquired Antibiotic Resistance Genes in Proteus spp

Proteus spp. are commensal Enterobacterales of the human digestive tract. At the same time, P. mirabilis is commonly involved in urinary tract infections (UTI). P. mirabilis is naturally resistant to several antibiotics including colistin and shows reduced susceptibility to imipenem. However higher levels of resistance to imipenem commonly occur in P. mirabilis isolates consecutively to the loss of porins, reduced expression of penicillin binding proteins (PBPs) PBP1a, PBP2, or acquisition of several antibiotic resistance genes, including carbapenemase genes. In addition, resistance to non-β-lactams is also frequently reported including molecules used for treating UTI infections (e.g., fluoroquinolones, nitrofurans). Emergence and spread of multidrug resistant P. mirabilis isolates, including those producing ESBLs, AmpC cephalosporinases and carbapenemases, are being more and more frequently reported. This review covers Proteus spp. with a focus on the different genetic mechanisms involved in the acquisition of resistance genes to multiple antibiotic classes turning P. mirabilis into a dreadful pandrug resistant bacteria and resulting in difficult to treat infections.

Incidence of antibiogram, antibiotic resistance genes and class 1 and 2 integrons in tribe Proteeae with IMP27 gene for the first time in Providencia sp. isolated from pet turtles

Proteeae is a tribe which consists of three genera: Proteus, Providencia and Morganella. The objective of this study was to determine antimicrobial resistance profile, virulence genotype and class 1 and 2 integrons in Proteeae isolated from pet turtles and to determine the impact of antibiotic resistance on virulence and antimicrobial resistance genes. Integron-positive isolates were used to detect their gene cassette array. Sixty four Proteeae were isolated and all were resistant to macrolides (100%). Among 64 isolates 56, 52, 36 and 25 were resistant to nitrofurans, β-lactams, tetracycline and aminoglycoside respectively. Sixteen (25%) isolates were positive for intI1 while 14 (21·87%) were positive for integrase 2 (intI2). Eleven (17·18%) isolates were positive for class 1 variable region while 7 (10·93%) were positive for class 2 variable region. IMP27, a novel metallo β-lactamase gene was found in Providencia isolates. Proteus sp. were positive for every tested virulence genes and UreC gene was detected in 48·44% followed by zapA (17·19%), mrpA (17·19%) and hlyA (14·06%) genes. In this study, integron associated-antibiotic resistance genes have been identified in Proteeae isolates in a considerable range representing clear threats to public health. SIGNIFICANCE AND IMPACT OF THE STUDY: In this study, multidrug-resistant Proteeae isolates had several antibiotic resistance genes. Integrons are important contributors to the development and dissemination of antibiotic resistance. We could detect both class 1 and 2 integrons and several gene cassette arrays in class 1 integron. The gene cassette arrays of the Class 2 integrons contained IMP27-dfrA1-aadA1-catB2-ybeA-ybgA in two isolates. To the best of our knowledge this is the first study to report detection of IMP27 in Providencia rettgeri isolates. All results indicate that healthy pet turtles act as potential reservoirs for Proteeae species with zoonotic potential.

Failure of a multiplex polymerase chain reaction assay to detect IMP-27 in a clinical isolate of Morganella morganii

A case of an IMP-27-positive Morganella morganii isolate is reported, where the carbapenemase enzyme was demonstrated by whole genome sequencing. Carbapenemase detection using a multiplex PCR assay was negative due to mutations in the primer binding site. This case serves to illustrate the limitations of multiplex PCR for carbapenemase detection.

blaIMP-27 on transferable plasmids in Proteus mirabilis and Providencia rettgeri

OBJECTIVES

A carbapenem-resistant Providencia rettgeri (PR1) isolate was recovered from a wound infection in Missouri, USA. This isolate possessed an EDTA-inhibitable carbapenemase that was unidentified using the Xpert CARBA-R assay. Our objective was to elucidate the molecular determinant of carbapenem resistance in this isolate. We then sought to test the transmissibility of bla_IMP-27 loci in clinical P. rettgeri and Proteus mirabilis isolates.

METHODS

In October 2016 the novel ambler Class B carbapenemase bla_IMP-27, was reported in two different Proteus mirabilis (PM185 and PM187) isolates. Broth mating assays for transfer of carbapenemase activity were performed for the three clinical isolates with recipient sodium azide-resistant Escherichia coli J53. Antibiotic susceptibility testing and phenotypic carbapenemase activity testing were performed on the clinical isolates, J53 and transconjugants using the Kirby-Bauer disc diffusion method according to CLSI guidelines. Plasmid DNA from PM187, PR1 and their transconjugants were used as input for Nextera Illumina sequencing libraries and sequenced on a NextSeq platform.

RESULTS

PR1 was resistant to both imipenem and meropenem. PM187 and PR1 could transfer resistance to E. coli through plasmid conjugation (pPM187 and pPR1). pPM187 had a virB/virD4 type IV secretion system whereas pPR1 had a traB/traD type IV secretion system.

CONCLUSION

Two of three bla_IMP-27-bearing clinical isolates tested could conjugate resistance into E. coli. The resulting transconjugants became positive for phenotypic carbapenemase production but did not pass clinical resistance breakpoints. bla_IMP-27 can be transmitted on different plasmid replicon types that rely on distinct classes of type IV secretion system for horizontal transfer.

Dissemination of Multidrug-Resistant Proteus mirabilis Clones Carrying a Novel Integron-Borne blaIMP-1 in a Tertiary Hospital

This study aimed to characterize multidrug-resistant Proteus mirabilis clones carrying a novel class 1 integron-borne bla_IMP-1 In1359 was inserted into a large conjugative plasmid that also carried bla_CTX-M-2 The production of carbapenemases in Enterobacteriaceae that are intrinsically resistant to polymyxins and tigecycline is very worrisome, representing a serious challenge to clinicians and infection control teams.

Carbapenemase-Producing Enterobacteriaceae Recovered from the Environment of a Swine Farrow-to-Finish Operation in the United States

Carbapenem-resistant Enterobacteriaceae (CRE) present an urgent threat to public health. While use of carbapenem antimicrobials is restricted for food-producing animals, other β-lactams, such as ceftiofur, are used in livestock. This use may provide selection pressure favoring the amplification of carbapenem resistance, but this relationship has not been established. Previously unreported among U.S. livestock, plasmid-mediated CRE have been reported from livestock in Europe and Asia. In this study, environmental and fecal samples were collected from a 1,500-sow, U.S. farrow-to-finish operation during 4 visits over a 5-month period in 2015. Samples were screened using selective media for the presence of CRE, and the resulting carbapenemase-producing isolates were further characterized. Of 30 environmental samples collected from a nursery room on our initial visit, 2 (7%) samples yielded 3 isolates, 2 sequence type 218 (ST 218) Escherichia coli and 1 Proteus mirabilis, carrying the metallo-β-lactamase gene bla_IMP-27 on IncQ1 plasmids. We recovered on our third visit 15 IMP-27-bearing isolates of multiple Enterobacteriaceae species from 11 of 24 (46%) environmental samples from 2 farrowing rooms. These isolates each also carried bla_IMP-27 on IncQ1 plasmids. No CRE isolates were recovered from fecal swabs or samples in this study. As is common in U.S. swine production, piglets on this farm receive ceftiofur at birth, with males receiving a second dose at castration (≈day 6). This selection pressure may favor the dissemination of bla_IMP-27-bearing Enterobacteriaceae in this farrowing barn. The absence of this selection pressure in the nursery and finisher barns likely resulted in the loss of the ecological niche needed for maintenance of this carbapenem resistance gene.