Diversity in VIM-2-encoding class 1 integrons and occasional blaSHV2a carriage in isolates of a persistent, multidrug-resistant Pseudomonas aeruginosa clone from Tunis

High Prevalence of GES-5 Variant and Co-Expression of VIM-2 and GES-45 among Clinical Pseudomonas aeruginosa Strains in Tunisia

Carbapenem-resistant Pseudomonas aeruginosa (CRPA) are a global health concern. The antimicrobial resistance, virulence, and molecular typing of 57 CRPA isolated from 43 patients who attended a specific Tunisian hospital from September 2018 to July 2019 were analyzed. All but one were multidrug-resistant CRPA, and 77% were difficult-to-treat-resistant (DTR) isolates. The blaVIM-2 gene was detected in four strains (6.9%), and among the 36 blaGES-positive CRPA (62%), the blaGES-5 gene was the predominant variant (86%). Three strains co-harbored the blaVIM-2 and blaGES-45 genes, and seven CRPA carried the blaSHV-2a gene (14%). OprD alterations, including truncations by insertion sequences, were observed in 18 strains. Regarding the 46 class 1 integron-positive CRPA (81%), the blaGES-5 gene was located in integron In717, while the blaGES-29 and blaGES-45 genes were found in two new integrons (In2122 and In4879), and the blaVIM-2 gene was found in In1183 and the new integron In2142. Twenty-four PFGE patterns and thirteen sequence types (three new ones) were identified. The predominant serotype O:11 and exoU (81%) were mostly associated with ST235 and the new ST3385 clones. The seven blaSHV-2a-CRPA from different patients belonged to ST3385 and the same PFGE pattern. The blaGES-5- and blaVIM-2 + blaGES-45-positive CRPA recovered mostly from ICU patients belonged to the high-risk clone ST235. Our results highlight the alarming prevalence of blaGES-5- and ST235-CRPA, the co-existence of blaGES-45 and blaVIM-2, and their location within integrons favoring their dissemination.

Genetic support of carbapenemases: a One Health systematic review and meta-analysis of current trends in Africa

Antimicrobial resistance (AMR) is a public health threat globally. Carbapenems are β-lactam antibiotics used as last-resort agents for treating antibiotic-resistant infections. Mobile genetic elements (MGEs) play an important role in the dissemination and expression of antimicrobial resistance genes (ARGs), including the mobilization of ARGs within and between species. The presence of MGEs around carbapenem-hydrolyzing enzymes, called carbapenemases, in bacterial isolates in Africa is concerning. The association between MGEs and carbapenemases is described herein. Specific plasmid replicons, integrons, transposons, and insertion sequences were found flanking specific and different carbapenemases across the same and different clones and species isolated from humans, animals, and the environment. Notably, similar genetic contexts have been reported in non-African countries, supporting the importance of MGEs in driving the intra- and interclonal and species transmission of carbapenemases in Africa and globally. Technical and budgetary limitations remain challenges for epidemiological analysis of carbapenemases in Africa, as studies undertaken with whole-genome sequencing remained relatively few. Characterization of MGEs in antibiotic-resistant infections can deepen our understanding of carbapenemase epidemiology and facilitate the control of AMR in Africa. Investment in genomic epidemiology will facilitate faster clinical interventions and containment of outbreaks.

Detection of diverse carbapenem and multidrug resistance genes and high-risk strain types among carbapenem non-susceptible clinical isolates of target gram-negative bacteria in Kenya

Carbapenem-resistant gram-negative bacteria are an increasingly significant clinical threat globally. This risk may be underestimated in Kenya as only four carbapenemase genes in three bacterial species have been described. The study aimed to understand the antibiotic resistance profiles, genes, sequence types, and distribution of carbapenem-resistant gram-negative bacteria from patients in six hospitals across five Kenyan counties by bacterial culture, antibiotic susceptibility testing, and whole-genome sequence analysis. Forty-eight, non-duplicate, carbapenem non-susceptible, clinical isolates were identified across the five counties (predominantly in Nairobi and Kisii): twenty-seven Acinetobacter baumannii, fourteen Pseudomonas aeruginosa, three Escherichia coli, two Enterobacter cloacae, and two Klebsiella pneumoniae. All isolates were non-susceptible to β-lactam drugs with variable susceptibility to tigecycline (66%), minocycline (52.9%), tetracycline (29.4%), and levofloxacin (22.9%). Thirteen P. aeruginosa isolates were resistant to all antibiotics tested. Eleven carbapenemase genes were identified: blaNDM-1, blaOXA-23, -58, -66, -69, and -91 in A. baumannii (STs 1, 2, 164 and a novel ST1475), blaNDM-1 in E. cloacae (STs 25,182), blaNDM-1, blaVIM-1and -6, blaOXA-50 in P. aeruginosa (STs 316, 357, 654, and1203), blaOXA-181, blaNDM-1 in K. pneumoniae (STs 147 and 219), and blaNDM-5 in E. coli (ST164). Five A. baumannii isolates had two carbapenemases, blaNDM-1, and either blaOXA-23 (4) or blaOXA-58 (1). AmpC genes were detected in A. baumannii (blaADC-25), E. cloacae (blaDHA-1 and blaACT-6, 16), and K. pneumoniae (blaCMY). Significant multiple-drug resistant genes were the pan-aminoglycoside resistance16srRNA methyltransferase armA, rmtB, rmtC, and rmtF genes. This study is the first to report blaOXA-420, -58, -181, VIM-6, and blaNDM-5 in Kenyan isolates. High-risk STs of A. baumannii (ST1475, ST2), E. cloacae ST182, K. pneumoniae ST147, P. aeruginosa (ST357, 654), and E. coli ST167, ST648 were identified which present considerable therapeutic danger. The study recommends urgent carbapenem use regulation and containment of high-risk carbapenem-resistant bacteria.

Carbapenemase Producing Gram-Negative Bacteria in Tunisia: History of Thirteen Years of Challenge

The wide spread of multidrug-resistant bacteria, particularly carbapenem-resistant Gram-negative bacteria (CR-GNB), constitutes a major public health threat worldwide, owing to the limited therapeutic options. This review will describe and uncover the Tunisian experience in the challenge against carbapenem resistance. Indeed, we illuminate on the dissemination of CR-GNB in different hospitals, animals, and other natural environments in this country. We resumed the different carbapenemase variants detected from various bacterial species and mapped their regional distribution, basing on Tunisian published data during a period extended from 2006, the date of its first description in Tunisia, to February 2019. We also resumed the different mobile genetic elements implicated in their dissemination. This review shows that the majority of the research reports focused in the north and the coastal cities in spite of the fact that KPC and IMP carbapenemases were uncommonly detected in our country. However, VIM, NDM-1, and OXA-48 enzymes were usually reported with the predominance of OXA-48 among Enterobacteriaceae. Furthermore, OXA-23, OXA-51, and OXA-58 carbapenemases constituted the main mechanism conferring carbapenem resistance among Acinetobacter baumannii in Tunisia. Collaborative efforts and raising awareness of the threat of antibiotic resistance are required in order to minimize the spread of multidrug-resistant bacteria.

Prevalence of metallo-β-lactamase-producing Pseudomonas aeruginosa isolated from diabetic foot infections in Iraq

Metallo-β-lactamase (MBL)-producing Pseudomonas aeruginosa is a major cause of nosocomial infections. However, there is little information in Iraq regarding its prevalence in patients with diabetic foot ulcer. Carbapenems are efficient antibiotics against extended-spectrum β-lactamase–producing P. aeruginosa. However, there are many potential health risks associated with carbapenem-resistant P. aeruginosa. We aimed to determine MBL-producing P. aeruginosa isolated from diabetic foot ulcer infections. A total of 97 P. aeruginosa isolates were isolated from pus and deep tissue swabs of 282 patients admitted to Al-Sader hospital, Najaf City, Iraq, with diabetic foot infections from October 2017 to January 2018. All P. aeruginosa isolates were tested by the Kirby-Bauer disc diffusion method for evaluating 13 antibiotics. Phenotypic carbapenem resistance was confirmed by the combined disc test, double-disc synergy test, modified Hodge test and CHROMagar KPC agar. All phenotypic MBL-producing P. aeruginosa isolates were screened for bla_IMP, bla_NDM, bla_SIM, bla_SPM and bla_VIM genes by multiplex PCR. Of the 97 P. aeruginosa isolates, combined disc test and modified Hodge test revealed 12 isolates (12.4%) to be MBL producers, and ten (10.3%) displayed MBL production as accessed by CHROMagar KPC agar test. Nine isolates (9.3%) were carbapenemase producers by the imipenem and ceftizoxime double-disc synergy test. Of 12 phenotypic MBL-producing P. aeruginosa, PCR amplification confirmed 4 (33.3%) and 3 (25%) isolates harbouring bla_VIM and bla_IMP gene respectively, but none carried the bla_NDM, bla_SIM or bla_SPM genes. The steady and rapid increase of MBL production is worrisome and needs to be controlled through extensive studies and more judicious selection of antibiotics, especially carbapenems.

Characterization of O25b-ST131 Escherichia coli Clone Producing CTX-M-15, DHA-4, and CMY-42 in Urinary Tract Infections in a Tunisian Island

The dissemination of extended-spectrum β-lactamases encoding genes in Escherichia coli, especially in the uropathogenic O25b-ST131 E. coli clone, constitutes a real concern. We aimed to identify the molecular mechanisms of resistance to cephalosporins among E. coli clinical isolates and to estimate the prevalence of the uropathogenic O25b-ST131 clone in our study. Forty-two cephalosporin-resistant E. coli implicated in urinary tract infections were collected from the Regional Hospital of a southeastern Tunisian Island from April 2015 to August 2016. Molecular screening of β-lactamases encoding genes by PCR and sequencing showed that the majority of our isolates harbored bla_CTX-M gene (bla_CTX-M-15 [n = 36], bla_CTX-M-14 [n = 2]). Nevertheless, the bla_SHV, bla_TEM, and bla_OXA-1 genes were not detected. Various class C β-lactamases encoding genes were observed in association or not with bla_CTX-M genes and were as follows: bla_ampC (n = 14), bla_CMY-42 (n = 7), bla_CMY-2 (n = 1), and bla_DHA-4 (n = 1). The research of O25b-ST131 clone was carried out by duplex PCR (pabB and trpA genes) and revealed that most of our isolates (n = 30) belonged to this clone. We also noted that the majority of our isolates belonged to the B2 phylogenetic group (n = 32), five isolates to the B1 phylogenetic group, three isolates to the D phylogenetic group, and only two isolates belonged to the A phylogenetic group. Our study provides new epidemiological information about E. coli clinical isolates in this area. Indeed, this is the first report of CTX-M-14 producing O25b-ST131 E. coli in our country and the first report of DHA-4 and CMY-42 producing E. coli in Tunisia.

Local outbreak of extended-spectrum β-lactamase SHV2a-producing Pseudomonas aeruginosa reveals the emergence of a new specific sub-lineage of the international ST235 high-risk clone

BACKGROUND

Pseudomonas aeruginosa is a major bacterial pathogen responsible for hospital-acquired infections. Although its epidemiology is considered as non-clonal, certain international high-risk multidrug-resistant clones have been recognized.

AIM

From the first report of an intra-hospital outbreak due to an SHV2a-producing P. aeruginosa strain, to describe the emergence of a new ST235-specific lineage harbouring this rare extended-spectrum β-lactamase (ESBL).

METHODS

Between May and October 2018, four patients hospitalized in the cardiovascular intensive care unit of a French teaching hospital were infected by a multidrug-resistant P. aeruginosa isolate. Serotype and antimicrobial susceptibility were tested; multi-locus sequence type (MLST), core genome MLST, and resistome were determined through whole genome sequencing. A phylogenetic analysis based on single nucleotide polymorphism was performed using available ST235 genomes.

FINDINGS

The four strains were susceptible to colistin, ciprofloxacin, ceftazidime-avibactam, and ceftolozane-tazobactam. bla_SHV2a was identified in each genome of this ST235-O11 serotype cluster that showed an identical cgMLST profile (0-2 out of 4162 different alleles). The phylogenic analysis of 162 ST235 genomes showed that only four other strains harboured a bla_SHV2a, originating from France and USA, clustering together although being different from the outbreak strains.

CONCLUSIONS

Among the ST235 P. aeruginosa strains, a sub-lineage sharing a common genetic background and harbouring the bla_SHV2a ESBL seems to emerge from different locations, yielding secondary local outbreaks.

First report of VIM-2 metallo-β-lactamases producing Pseudomonas aeruginosa isolates in Morocco

The emergence and the rapid spread of Pseudomonas aeruginosa carrying carbapenemases represent a serious threat to public health due to their delicate therapy. This work was performed to establish the resistance profile and to detect carbapenemases producing in 123 P. aeruginosa isolates. Among these 55 are environmental isolates and 68 are from the two major hospitals of Meknes-Tafilalet region in Morocco. All strains were tested against 14 antipseudomonal drugs by disc diffusion method. On carbapenem resistant strains minimum inhibitory concentrations of imipenem were determined by the E-test method. The modified Hodge test and EDTA tests were used for the detection of carbapenemases and metallo-β-lactamases (MBLs), respectively. PCR and DNA sequencing were conducted to detect carbapenemase-encoding genes and the enzyme types. 12% of isolates was susceptible to all antibiotics tested and Carbapenem resistance was observed in 33 P. aeruginosa isolates, 33.3% of them were multi-drug resistant. Among carbapenem resistant strains only two (6.1%) were positive for carbapenemases and also for MBLs. In addition to their resistance to almost all β-lactams tested, the MBLs producing strains were resistant to aminoglycosides. Molecular biology techniques confirmed the phenotypic results obtained for the two strains carbapenemase producers and demonstrated that each one of them carried blaVIM-2. The present study reports the first isolation of blaVIM genes in clinical isolates of P. aeruginosa in Morocco. Such isolates represent a serious emerging threat requiring strict hygiene measures to better control their spread.

Identification of VIM-2-producing Pseudomonas aeruginosa from Tanzania is associated with sequence types 244 and 640 and the location of blaVIM-2 in a TniC integron

Epidemiological data on carbapenemase-producing Gram-negative bacteria on the African continent are limited. Here, we report the identification of VIM-2-producing Pseudomonas aeruginosa isolates in Tanzania. Eight out of 90 clinical isolates of P. aeruginosa from a tertiary care hospital in Dar es Salaam were shown to harbor bla(VIM-2). The bla(VIM-2)-positive isolates belonged to two different sequence types (ST), ST244 and ST640, with bla(VIM-2) located in an unusual integron structure lacking the 3' conserved region of qacΔE1-sul1.

The spread of carbapenemase-producing bacteria in Africa: a systematic review

BACKGROUND

Carbapenems are the last line of defence against ever more prevalent MDR Gram-negative bacteria, but their efficacy is threatened worldwide by bacteria that produce carbapenemase enzymes. The epidemiology of bacteria producing carbapenemases has been described in considerable detail in Europe, North America and Asia; however, little is known about their spread and clinical relevance in Africa.

METHODS

We systematically searched in PubMed, EBSCOhost, Web of Science, Scopus, Elsevier Masson Consulte and African Journals Online, international conference proceedings, published theses and dissertations for studies reporting on carbapenemase-producing bacteria in Africa. We included articles published in English or French up to 28 February 2014. We calculated the prevalence of carbapenemase producers only including studies where the total number of isolates tested was at least 30.

RESULTS

Eighty-three studies were included and analysed. Most studies were conducted in North Africa (74%, 61/83), followed by Southern Africa (12%, 10/83), especially South Africa (90%, 9/10), West Africa (8%, 7/83) and East Africa (6%, 6/83). Carbapenemase-producing bacteria were isolated from humans, the hospital environment and community environmental water samples, but not from animals. The prevalence of carbapenemase-producing isolates in hospital settings ranged from 2.3% to 67.7% in North Africa and from 9% to 60% in sub-Saharan Africa.

CONCLUSIONS

Carbapenemase-producing bacteria have been described in many African countries; however, their prevalence is poorly defined and has not been systematically studied. Antibiotic stewardship and surveillance systems, including molecular detection and genotyping of resistant isolates, should be implemented to monitor and reduce the spread of carbapenemase-producing bacteria.

Dissemination of IMP-6-producing Pseudomonas aeruginosa ST244 in multiple cities in China

Pseudomonas aeruginosa is an important opportunistic pathogen responsible for nosocomial infections and is currently reported to be a worldwide nosocomial menace. The aim of this study was to investigate the epidemiological traits and the distribution of metallo-β-lactamases (MBLs)-producing P. aeruginosa clinical isolates in ten cities in China between January 2010 and May 2012. Antimicrobial susceptibility was determined by disc diffusion assay and the minimum inhibitory concentrations (MICs) of imipenem and meropenem were also determined by the Etest according to Clinical and Laboratory Standards Institute (CLSI) guidelines. In addition, polymerase chain reaction (PCR) and DNA sequencing were applied to detect bla MBL genes, and their epidemiological relationships were investigated by multilocus sequence typing (MLST). Of 368 P. aeruginosa isolates, MLST analysis identified 138 sequence types (STs), including 122 known and 16 novel STs, and the most frequently detected clone was ST244, followed by ST235. Besides, our study revealed that 25 isolates carried the bla IMP-6 gene and three isolates carried the bla VIM-2 gene, and a probe specific for both genes could be hybridised to an ~1,125-kb fragment in all isolates. Interestingly, all of the bla IMP-6-producing isolates shared an identical ST, ST244, and exhibited a higher level of resistance to several antibiotics. Overall, these observations suggest that P. aeruginosa ST244 carrying the chromosomally located bla IMP-6 gene is widely disseminated in multiple cites in China.

Molecular epidemiology of carbapenem-resistant Pseudomonas aeruginosa clinical strains isolated from western Algeria between 2009 and 2012

Infections caused by carbapenem-resistant Pseudomonas aeruginosa strains represent a major therapeutic and epidemiological problem. The aim of this study was to characterize carbapenem resistance in 89 clinical strains of P. aeruginosa isolated from three hospitals in western Algeria between October 2009 and November 2012. Minimum inhibitory concentrations (MICs) of imipenem were determined by the Etest method. Screening for metallo-β-lactamase (MβL) was performed using Etest MβL strips, and a PCR was conducted to detect carbapenemase-encoding genes. The amplification of the oprD gene followed by a sequencing reaction was performed for all strains resistant to imipenem. The clonality of 53 P. aeruginosa strains was demonstrated using multilocus sequence typing (MLST). Among the 89 isolates, 35 (39.33%) were found to be resistant to IMP (MICs ≥16 μg/ml). The blaVIM-2 gene was detected in two strains. The remaining imipenem-resistant isolates showed the presence of oprD mutations. The MLST analysis differentiated strains into various clones and the strains from the same clone had an identical sequence of the oprD gene. We report the second detection in 2010 of blaVIM-2 in Algerian P. aeruginosa strains. We also found that oprD mutations were the major determinant of high-level imipenem resistance. We demonstrate that these oprD mutations can be used as a tool to study the clonality in P. aeruginosa isolates.

Analysis of integrons and associated gene cassettes in clinical isolates of multidrug resistant Pseudomonas aeruginosa from Southwest Nigeria

Background

Multidrug resistant Pseudomonas aeruginosa harbours integrons and other mobile genetic elements such as plasmids and transposons, which easily disseminate antibiotic resistance genes among clinical strains of P. aeruginosa.

Methodology

Plasmid extraction of 54 clinical isolates of P. aeruginosa was carried out by alkaline lysis method; and plasmid size estimation was done by using E. coli V517 standard plasmid marker. Fifty-four clinical strains of P. aeruginosa were isolated from 5 hospitals in 3 Southwestern states of Nigeria between March and September 2010. Plasmid extraction of isolates was carried out by alkaline lysis method; and plasmid size estimation was done by using E. coli V517 standard plasmid marker. PCR amplification for the 3 classes of resistance integrons, and gene cassette characterization were carried out using specific primers and by sequencing of PCR products. Conjugal mating of the integron positive P. aeruginosa strains with E. coli DH5α was performed to demonstrate transferability of integrons and gene cassettes.

Result

Agarose gel electrophoresis of plasmid DNA revealed that all the 54 P. aeruginosa harboured 1–4 plasmids with sizes ranging from 2.2 – >58 kb. Class 1 integron was identified in 31 (57%) strains; but none of them carried class 2 and class 3 integrons. High prevalence of aadA gene conferring resistance to streptomycin/spectinomycin was detected in the strains positive for class 1 integron. Sequencing of the 1.6 kb and 1.2 kb amplified band of gene cassettes revealed the presence of aadA6-orfD and aadA13 respectively.

Conclusion

This study demonstrates the presence of plasmids and integrons harbouring resistance gene cassettes, which may collectively constitute an efficient system for dissemination of resistance genes in P. aeruginosa. Disturbingly, the rapid and unabated spread of class 1 integron-associated multidrug resistant P. aeruginosa in Southwest Nigeria may greatly hamper successful treatment of infections caused by such strains. This necessitates the establishment of functional antimicrobial resistance surveillance programmes in Nigeria.

Nosocomial outbreak of imipenem-resistant Pseudomonas aeruginosa producing VIM-2 metallo-β-lactamase in a kidney transplantation unit

Background

Twenty four non replicate imipenem resistant P. aeruginosa were isolated between January and November 2008, in the kidney transplantation unit of Charles Nicolle Hospital of Tunis (Tunisia). This study was conducted in order to establish epidemiological relationship among them and to identify the enzymatic mechanism involved in imipenem resistance.

Methods

Analysis included antimicrobial susceptibility profile, phenotypic (imipenem-EDTA synergy test) and genotypic detection of metallo-β-lactamase (MBL) (PCR), O-serotyping and pulsed-field gel electrophoresis.

Results

All strains showed a high level of resistance to all antimicrobials tested except to colistin. The presence of MBL showed concordance between phenotypic and genotypic methods. Sixteen isolates were identified as VIM-2 MBL-producers and 13 of them were serotype O4 and belonged to a single pulsotype (A).

Conclusions

This study describes an outbreak of VIM-2-producing P. aeruginosa in a kidney transplantation unit. Clinical spread of bla_VIM-2 gene is a matter of great concern for carbapenem resistance in Tunisia.

Functional characterization of Tn4401, a Tn3-based transposon involved in blaKPC gene mobilization

The carbapenemase gene bla(KPC), which is rapidly spreading worldwide, is located on a Tn3-based transposon, Tn4401. In a transposition-conjugation assay, Tn4401 was able to mobilize bla(KPC-2) gene at a frequency of 4.4 × 10(-6)/recipient cell. A 5-bp target site duplication was evidenced upon each insertion without target site specificity. This study demonstrated that Tn4401 is an active transposon capable of mobilizing bla(KPC) genes at high frequency.

Evolution of β-lactams resistance in Gram-negative bacteria in Tunisia

Antimicrobial resistance is a major health problem worldwide, but marked variations in the resistance profiles of bacterial pathogens are found between countries and in different patient settings. In Tunisia, the strikingly high prevalence of resistance of bacteria to penicillins and cephalorosporins drugs including fourth generation in clinical isolates of Gram negative bacteria has been reported. During 30 years, the emerging problem of extended-spectrum β-lactamase-producing Escherichia coli and Klebsiella pneumoniae isolates is substantial, and some unique enzymes have been found. Recently, evidence that Gram-negative bacteria are resistant to nearly all available antimicrobial agents, including carbapenems, have emerged.

Analysis of integrons and associated gene cassettes of metallo-β-lactamase-positive Pseudomonas aeruginosa in Malaysia

In this study, 90 non-replicate imipenem-resistant Pseudomonas aeruginosa (IRPA) Malaysian isolates collected between October 2005 and March 2008 were subjected to a screening test for detection of the integron and the gene cassette. Class 1 integrons were detected in 54 IRPA clinical isolates, whilst three isolates contained class 2 integrons. Analysis of the gene cassettes associated with the class 1 integrons showed the detection of accC1 in isolates carrying bla(IMP-7) and aacA7 in isolates carrying bla(VIM-2). aadA6 was detected in two isolates carrying bla(IMP-4). Using random amplification of polymorphic DNA analysis, 14 PCR fingerprint patterns were generated from the 32 isolates carrying metallo-β-lactamase (MBL) genes (35.5 %), whilst 20 patterns were generated from the 58 non-MBL gene isolates (64.4 %). Based on the differences in the fingerprinting patterns, two clusters (A and B) were identified among the MBL-producing isolates. Cluster A comprised 18 isolates (56 %) carrying the bla(VIM) gene, whereas cluster B comprised 14 (44 %) isolates carrying the bla(IMP) gene. The non-MBL isolates were divided into clusters C and D. Cluster C comprised 22 non-MBL isolates harbouring class 1 integrons, whilst cluster D consisted of three isolates carrying class 2 integrons. These findings suggest that the class 1 integron is widespread among P. aeruginosa isolated in Malaysia and that characterization of cassette arrays of integrons will be a useful epidemiological tool to study the evolution of multidrug resistance and the dissemination of antibiotic resistance genes.