Prevalence Of Colistin Resistance Research Articles

Susceptibility analysis of various bacteria towards colistin and other antibiotics in clinical isolates

This study aimed to determine the susceptibility of Gram-negative bacilli isolated from various clinical samples of patients admitted to ICUs of hospitals in Telangana region against colistin and compared with other antibiotics. In the present study clinical pathogen isolates were used for the susceptibility test. A total of 1852 consecutive Gram-negative isolates were tested for Colistin susceptibility. All the bacterial isolates of (e.g., , ), and were included. All Colistin resistant isolates were processed to detect the minimum inhibitory concentration (MIC) of antibiotics by the broth micro-dilution method. It was observed that in . and the susceptibility was quite significant whereas it was not much significant for other species of bacteria studied namely, , , , and . . and resistance indicated that there is an argent need to get the current situation under control by implementing appropriate measures to slow down the progression of antibiotic resistance in gram-negative bacteria in Telangana. and showed significant resistance to Colistin compared with other antibiotics than other gram-negative bacilli isolated from various clinical samples. There is a shortage of clinical data available in South India regarding the prevalence of colistin resistance. This study is one of the few studies that indicate the current scenario of resistance of gram-negative bacteria in this particular area.

Prevalence of colistin resistance and antibacterial resistance in commensal Escherichia coli from chickens: An assessment of the impact of regulatory intervention in South Africa.

Antimicrobial resistance (AMR) is a global health problem largely due to the overuse of antimicrobials. In recognition of this, the World Health Assembly in 2015 agreed on a global action plan to tackle AMR. Following the global emergence of the mcr-1-associated colistin resistance gene in the livestock industry in 2016, several countries including South Africa restricted the veterinary use of colistin as the gene threatens the clinical utility of the drug. This study is a follow-up to the restriction in place in order to evaluate the impact of such policy adoption. To assess the prevalence of antibacterial resistance (ABR), and the mcr-1 colistin resistance gene in broiler chicken over a 2-year period, as a follow-up to the veterinary ban on colistin use in South Africa. A total of 520 swab samples were obtained during 2019 (March-April) and 2020 (February-March), from healthy broiler chicken carcasses (n=20) and chicken droppings in transport crates (n=20) at various poultry abattoirs (N=7) in the Gauteng province of South Africa. Escherichia coli organisms were isolated and subjected to a panel of 24 antibacterials using the MicroScan machine. Screening for mcr-1 colistin resistance gene was undertaken using PCR. Four hundred and thirty-eight (438) E. coli strains were recovered and none demonstrated phenotypic resistance towards colistin, amikacin, carbapenems, tigecycline and piperacillin/tazobactam. The mcr-1 gene was not detected in any of the isolates tested. Resistances to the aminoglycosides (0%-9.8%) and fluoroquinolones (0%-18.9%) were generally low. Resistances to ampicillin (32%-39.3%) and trimethoprim/sulphamethoxazole (30.6%-3.6%) were fairly high. A significant (p<0.05) increase in cephalosporins and cephamycin resistance was noted in the year 2020 (February-March) when compared with the year 2019 (March-April). The absence of mcr-1 gene and colistin resistance suggests that mitigation strategies adopted were effective and clearly demonstrated the significance of regulatory interventions in reducing resistance to critical drugs. Despite the drawback in regulatory framework such as free farmers access to antimicrobials OTC and a dual registration system in place, there is a general decline in the prevalence of ABR when the present data are compared with the last national veterinary surveillance on AMR (SANVAD 2007). To further drive resistance down, mitigation strategies should focus on strengthening regulatory framework, the withdrawal of OTC dispensing of antimicrobials, capping volumes of antimicrobials, banning growth promoters and investing on routine surveillance/monitoring of AMR and antimicrobial consumption.

Prevalence and molecular epidemiology of mcr-mediated colistin-resistance Escherichia coli from healthy poultry in France after national plan to reduce exposure to colistin in farm.

Within the 2007-2014 programme for the surveillance of antimicrobial resistance (AMR) in livestock in France, mcr-1 prevalence average in commensal Escherichia coli was found to be 5.9% in turkeys and 1.8% in broilers, indicating that mobile colistin resistance had spread in farm animals. In 2017, the French national Ecoantibio2 plan was established to tackle AMR in veterinary medicine, with the objective of a 50% reduction in exposure to colistin in farm animals within 5 years (from 2014-2015 to 2020). Our objective was to update data concerning the prevalence and molecular epidemiology of colistin resistance, in consideration of colistin sales in poultry production in France. Antimicrobial susceptibility of commensal E. coli isolated from broilers and turkeys at slaughterhouse was determined by broth micro-dilution. The mcr genes were screened by polymerase chain reaction (PCR). Whole genome sequencing (WGS) was used to investigate the genetic diversity of colistin-resistant isolates. Transformation experiments enabled identification of the mcr-bearing plasmid replicon types. The correlation between prevalence of colistin resistance and colistin usage data was explored statistically. In 2020, in France, the resistance prevalence to colistin in poultry production was 3% in turkeys and 1% in broilers, showing a significant highly positive correlation with a -68% decrease of poultry exposure to colistin since 2014. Only the mcr-1 gene was detected among the colistin-resistant E. coli. More than 80% of isolates are multi-drug resistant with 40% of isolates originating from turkeys and 44% originating from broilers co-resistant to the critically important antimicrobial ciprofloxacin. Most of the strains had no clonal relationship. The mcr gene was located in different plasmid types, carrying various other AMR genes. The decrease in colistin resistance among poultry in France can be considered a positive outcome of the national action plans for reduced colistin usage.

Tunisian Multicenter Study on the Prevalence of Colistin Resistance in Clinical Isolates of Gram Negative Bacilli: Emergence of Escherichia coli Harbouring the mcr-1 Gene.

Background: Actually, no data on the prevalence of plasmid colistin resistance in Tunisia are available among clinical bacteria. Objectives: This study aimed to investigate the current epidemiology of colistin resistance and the spread of the mcr gene in clinical Gram-negative bacteria (GNB) isolated from six Tunisian university hospitals. Methods: A total of 836 GNB strains were inoculated on COL-R agar plates with selective screening agar for the isolation of GNB resistant to colistin. For the selected isolates, mcr genes, beta-lactamases associated-resistance genes and molecular characterisation were screened by PCRs and sequencing. Results: Colistin-resistance was detected in 5.02% (42/836) of the isolates and colistin-resistant isolates harboured an ESBL (blaCTX-M-15) and/or a carbapenemase (blaOXA-48, blaVIM) encoding gene in 45.2% of the cases. The mcr-1 gene was detected in four E. coli isolates (0.59%) causing urinary tract infections and all these isolates also contained the blaTEM-1 gene. The blaCTX-M-15 gene was detected in three isolates that also carried the IncY and IncFIB replicons. The genetic environment surrounding the mcr-carrying plasmid indicated the presence of pap-2 gene upstream mcr-1 resistance marker with unusual missing of ISApl1 insertion sequence. The Conclusions: This study reports the first description of the mcr-1 gene among clinical E. coli isolates in Tunisia and provides an incentive to conduct routine colistin susceptibility testing in GNB clinical isolates.

Genetic and drug susceptibility profiles of mcr-1-bearing foodborne Salmonella strains collected in Shenzhen, China during the period 2014–2017

Colistin resistance mediated by mcr-1-bearing plasmids poses a new challenge to treatment of Salmonella infections. To probe the scale of the problem that colistin resistance mediated by mcr-1 plasmids among Salmonella, the prevalence of mcr-1 in foodborne Salmonella recovered from 2014 to 2017 in Shenzhen, China and genetic profile of mcr-1 positive isolates were investigated. All mcr-1 positives Salmonella strains were collected from food products, characterized by PCR and MALDI-TOF, and subjected to antimicrobial susceptibility testing, whole-genome sequencing, bioinformatics analysis, and conjugation. Twenty-eight mcr-1-positive Salmonella strains were recovered from pork. The rate of recovery displayed an increasing trend and was often accompanied by multidrug resistance. Salmonella Typhimurium was the most prevalent serotypes. Comparative genomic analysis indicated that the mcr-1 gene was located on the transferable IncX4 plasmids, as well as the IncHI2 plasmids, in which the gene was associated with ISApl1. All two types of plasmids were often detected in zoonotic pathogen. Transferable 251K mcr-1-bearing IncHI2 type plasmids were frequently reported in human and food-producing animals, but this is first time to detect a certain number in food. These findings show that dissemination of these two types of plasmids is responsible for the increase in the prevalence of colistin resistance in Salmonella strains in recent years, leading to rapid emergence of MDR Salmonella upon acquisition of these two mcr-1-bearing plasmids. Transmission of IncX4 and IncHI2 plasmids in Salmonella would cause huge public health concerns in controlling foodborne infections caused by Salmonella.

Colistin A Last Resort Antibiotic

Colistin is an antibiotic of last resort, works as a last line of defense against illness caused by the multiple drug resistant (MDR) gram negative bacteria. Polimixins consist of aqua phobic acyl tail, linear tripeptide part, and heptapeptide ring. Chemical formula of colistin is C52H98N16O13. Colistin is given in two forms, colistin methane sulfonate (CMS) and colistin sulfate.&#x0D; Findings: Colistin disturbs or destroys the outer membrane of bacteria, or stops the respiratory enzymes of the inner membrane of bacteria. Colistin also works as an antiendotoxin. Colistin has great bactericidal activity against gram negative rods. Colistin resistance is a serious concern of present time. High rate of the spread of MDR gram negative bacterial infections is leading to high use of colistin for treatment, due to which prevalence of colistin resistance is increasing worldwide. As bacterial outer membrane is the main target of colistin, resistance against it develop by modification of outer membrane LPS. There are several mechanisms of colistin resistance. Intrinsic mechanism involves expression of arnBCADTEF operon and eptB gene. Acquired non-transferable resistance involves pmrAB, PhoPQ, and CrrAB two component systems (TCSs), mgrB gene and ramA. Transferable resistance is more serious concern as it can be spread in population by horizontal gene transfer. Mcr genes are responsible for transferable or plasmid-mediated colistin resistance.&#x0D; Conclusion: This review focuses on the chemistry of colistin, mechanism of action, spectrum of action, colistin resistance and different mechanisms behind it.

Molecular Mechanisms of Colistin Resistance in Klebsiella pneumoniae in a Tertiary Care Teaching Hospital.

BackgroundOver the last two decades, the prevalence of colistin resistance among the members of Enterobacteriaceae has been increasing, particularly among Klebsiella pneumoniae isolates; this limits the potential use of colistin and leads to worsened clinical outcomes.MethodsWe investigated the prevalence and genetic characteristics of colistin-resistant K. pneumoniae (COLR-KP) in clinical isolates using genomic sequencing.ResultsIn total, 53 K. pneumoniae isolates (4.5%, 53/1,171) were confirmed as COLR-KP, of which eight isolates carried mobile colistin-resistant (mcr) gene. Although the overall prevalence rate (0.7%, 8/1,171) of mcr-like genes in clinical K. pneumoniae remained relatively low, the presence of mcr (15.1%, 8/53) among the COLR-KP isolates indicated that the mobile resistance gene was already widespread among K. pneumoniae isolates in hospital setting. We randomly selected 13 COLR-KP isolates (four mcr-bearing and nine non-mcr-bearing isolates) for whole-genome sequencing, including two pandrug-resistant and four sequence type 11 (ST11) isolates. Phylogenetic analysis revealed that all COLR-KP isolates were genetically diverse. Among the four mcr-bearing isolates, three (KP4, KP18, and KP30) were positive for mcr-1 and one (KP23) for mcr-8; none of the other mcr genes were detected. The mcr-1 in the KP4 and KP30 isolates were located in an IncX4 plasmid (approximately 33 kb) and could be successfully transferred to Escherichia coli J53AZR. In contrast, for the mcr-8-bearing plasmid in KP23 (IncFII), colistin resistance could not be transferred by conjugation. The mcr-1-producing isolate KP18 coexists a novel plasmid-carried tigecycline resistance gene tmexCD1-toprJ1. The most common chromosomal mutation associated with colistin resistance was a T246A amino acid substitution in PmrB, which was identified in most COLR-KP isolates (11/13, 84.6%). All ST11 isolates additionally had an R256G amino acid substitution. Critical virulence factors associated with hypervirulent K. pneumoniae were detected in four COLR-KP isolates; these virulence factors included aerobactin, salmochelin, and yersiniabactin.ConclusionWe found that mcr-bearing COLR-KP emerged in our hospital and was growing at an increasing rate. Simultaneous emergence of hypervirulence and colistin–tigecycline–carbapenem resistance in the epidemic clone ST11 K. pneumoniae was also observed; this highlights the significance of active and continuous surveillance.

Colistin Resistance among Human Clinical Isolates from a Tertiary Care Hospital in Nepal

Background Colistin is increasingly being used for treatment of multidrug resistant (MDR) bacterial infections in human. The plasmid mediated mcr-1 gene was detected recently among the poultry in Nepal. Plasmid mediated colistin resistance among human isolates would severely compromise the treatment of MDR bacterial infections.&#x0D; Objective To find out the prevalence of colistin resistance among the gram-negative bacteria isolated from clinical specimen.&#x0D; Method A descriptive cross-sectional study was conducted in a tertiary care hospital in Kathmandu. Colistin resistance among all the gram negative bacilli (GNB), isolated in a year, from all clinical specimen subjected for aerobic bacterial isolation, was detected by disc diffusion and agar dilution methods. Those with a minimum inhibitory concentration (MIC) &gt; 2 mcg/ml were subjected to polymerase chain reaction for detection of mcr-1 gene.&#x0D; Result A total of 1993 aerobic GNB were isolated from clinical samples received from February 2018 to January 2019. By the agar dilution screening method, 2.1% of the GNBs isolated had MIC of colistin &gt; 2 mcg/ml. None of these possessed the mcr-1 gene.&#x0D; Conclusion Given the occurrence of increased MIC of colistin in the clinical isolates in our set up, nationwide active surveillance would generate data for Nepal. The study for the presence of other genes (chromosomal or plasmid mediated) responsible for the increased MIC of colistin would further guide the control measures.

Prevalence of Colistin Resistance in Cancer Patients in a tertiary health care centre

Prevalence of Colistin Resistance in Cancer Patients in a tertiary health care centre

Antibiotic resistance and detection of plasmid mediated colistin resistance mcr-1 gene among Escherichia coli and Klebsiella pneumoniae isolated from clinical samples

BackgroundThe prevalence of antimicrobial resistance (AMR) among Gram-negative bacteria is alarmingly high. Reintroduction of colistin as last resort treatment in the infections caused by drug-resistant Gram-negative bacteria has led to the emergence and spread of colistin resistance. This study was designed to determine the prevalence of drug-resistance among beta-lactamase-producing strains of Escherichia coli and Klebsiella pneumoniae, isolated from the clinical specimens received at a tertiary care centre of Kathmandu, Nepal during the period of March to August, 2019.MethodsA total of 3216 different clinical samples were processed in the Microbiology laboratory of Kathmandu Model Hospital. Gram-negative isolates (E. coli and K. pneumoniae) were processed for antimicrobial susceptibility test (AST) by using modified Kirby-Bauer disc diffusion method. Drug-resistant isolates were further screened for extended-spectrum beta-lactamase (ESBL), metallo-beta-lactamase (MBL), carbapenemase and K. pneumoniae carbapenemase (KPC) production tests. All the suspected enzyme producers were processed for phenotypic confirmatory tests. Colistin resistance was determined by minimum inhibitory concentration (MIC) using agar dilution method. Colistin resistant strains were further screened for plasmid-mediated mcr-1 gene using conventional polymerase chain reaction (PCR).ResultsAmong the total samples processed, 16.4% (529/3216) samples had bacterial growth. A total of 583 bacterial isolates were recovered from 529 clinical samples. Among the total isolates, 78.0% (455/583) isolates were Gram-negative bacteria. The most predominant isolate among Gram-negatives was E. coli (66.4%; 302/455) and K. pneumoniae isolates were 9% (41/455). In AST, colistin, polymyxin B and tigecycline were the most effective antibiotics. The overall prevalence of multidrug-resistance (MDR) among both of the isolates was 58.0% (199/343). In the ESBL testing, 41.1% (n = 141) isolates were confirmed as ESBL-producers. The prevalence of ESBL-producing E. coli was 43% (130/302) whereas that of K. pneumoniae was 26.8% (11/41). Similarly, 12.5% (43/343) of the total isolates, 10.9% (33/302) of E. coli and 24.3% of (10/41) K. pneumoniae were resistant to carbapenem. Among 43 carbapenem resistant isolates, 30.2% (13/43) and 60.5% (26/43) were KPC and MBL-producers respectively. KPC-producers isolates of E. coli and K. pneumoniae were 33.3% (11/33) and 20% (2/10) respectively. Similarly, 63.6% (21/33) of the E. coli and 50% (5/10) of the K. pneumoniae were MBL-producers. In MIC assay, 2.2% (4/179) of E. coli and 10% (2/20) of K. pneumoniae isolates were confirmed as colistin resistant (MIC ≥ 4 µg/ml). Overall, the prevalence of colistin resistance was 3.1% (6/199) and acquisition of mcr-1 was 16.6% (3/18) among the E. coli isolates.ConclusionHigh prevalence of drug-resistance in our study is indicative of a deteriorating situation of AMR. Moreover, significant prevalence of resistant enzymes in our study reinforces their roles in the emergence of drug resistance. Resistance to last resort drug (colistin) and the isolation of mcr-1 indicate further urgency in infection management. Therefore, extensive surveillance, formulation and implementation of effective policies, augmentation of diagnostic facilities and incorporation of antibiotic stewardship programs can be some remedies to cope with this global crisis.

Detection of plasmid-mediated colistin resistance in carbapenem-resistant Escherichia coli and Klebsiella pneumoniae isolates in Suez Canal University Hospitals

Background: The polymyxins including colistin are the “last resort” antibiotics for treatment of infections with carbapenem resistant Enterobacteriaceae. Recently, transferable colistin resistance mediated by the mcr-genes has been described in Enterobacteriaceae. The Testing of colistin susceptibility is challenging. The aim of the work is to detect the occurence of mcr-1 and mcr-2 genes in phenotypically colistin-resistant carbapenem resistant Escherichia coli and Klebsiella pneumoniae isolates using conventional PCR. Methods: One hundred and sixteen carbapenem-resistant E.coli and K.pneumoniae isolates were collected from patients admitted to different wards of Suez Canal University Hospitals in Ismailia. Urine, endotracheal aspirates, blood, pus and sputum specimens were collected from different patients. Minimal inhibitory concentration by broth microdiluton method was done to assess phenotypic colistin resistance. The colistin resistant E.coli and K.pneumoniae isolates were tested by conventional PCR to detect plasmid mediated mcr-1 and mcr-2 genes. Chi-square test was applied and p -value < 0.05 was considered statistically significant. Results: Forty three isolates out of 116 carbapenem resistant isolates (37.1%) were colistin resistant as shown by MIC by broth microdiluton method. The 43 colistin resistant E.coli and K.pneumoniae isolates were tested by conventional PCR to detect plasmid mediated mcr-1 and mcr-2 genes. Two mcr-2 genes and one mcr-1 gene were detected. Conclusion: Results revealed that the prevalence of colistin resistance among carbapenem-resistant E.coli and K.pneumoniae in SCUHs is concerning; further limiting potential therapeutic options. Plasmid mediated colistin resistance genes mcr-1 and mcr-2 is emerging in SCUHs which refer to a problem in the hospital as by horizontal transfer of this plasmid, the resistance can spread to many isolates in the hospital.

A comparative evaluation of mikrolatest kit broth microdilution and VITEK2 in assessing colistin susceptibility to Gram-negative bacterial isolates

Introduction and Aim: The increasing resistance in colistin is a major concern. The aim of the study was to compare the methods to identify the prevalence of colistin resistance and antibiotic susceptibility patterns of colistin resistant strains isolates from blood, urine and sputum samples at all ICUs including NICU and PICU and wards.&#x0D; &#x0D; Materials and Methods: A total of 1458 consecutive Gram-negative isolates were tested for colistin susceptibility by standard broth microdilution method, Mikrolatest method and VITEK 2 automation system. Intrinsically colistin resistant organisms including Proteus sps, Providencia sps, Serratia sps., and Morganella morganii were excluded. Enterobacteriaceae (e.g., Escherichia coli, Klebsiella), Pseudomonas aeruginosa and Acinetobacter baumanii were included. The sensitivity, specificity, positive predictive value, negative predictive value of Vitek-2, BMD and Mikrolatest methods were compared. &#x0D; &#x0D; Results: Sixteen (1.09%) colistin?resistant isolates were reported over 24 months. K. pneumoniae constituted 8(50%), E. coli 6 (37.5%) and Enterobacter cloacae 2 (12.5%) of the 16 resistant isolates. The sensitivity, specificity, positive predictive value, negative predictive value of Mikrolatest compared with that of VITEK2 were 87.5% vs 56.25%, 90.84% vs 82.65%, 9.58% vs 3.47%and 99.8% vs 99.3%, respectively for resistant isolates. Mikrolatest shared good Category agreement of 1.24% with BMD Essential agreement was 1.5%. Comparing MICs of BMD with other tests, essential agreement was the lowest for the VITEK2, while the Mikrolatest MIC showed essential agreement greater than 1.5%. No errors and 100% categorical agreement (for E. coli, K. pneumoniae) were observed while comparing colistin susceptibility test results of the Mikrolatest MIC and BMD tests. The difference between the two methods in assessing colistin resistance were not statistically significant (P=0.89). Blood[37.5%] and pus[37.5%] samples recorded as the common sources of the isolate, followed by Urine [12.5%], and respiratory [12.5%) samples.&#x0D; &#x0D; Conclusion: Automated VITEK, Mikrolatest MIC methods give variable susceptibility results and colistin should be prescribed only after Mikrolatest and BMD. K. pneumoniae and E. coli, the Mikrolatest showed better performance for isolates with ? 0.5 or ? 16 µg/mL MICs. For P. aeruginosa isolates, colistin resistant isolates must be confirmed Colistin resistance among Gram-negative bacteria, especially K. pneumoniae, is emerging in Indian hospitals. Re-evaluation is required of the methods available to address the numerous technical challenges associated with colistin susceptibility testing, and to determine which method yields the most meaningful results. These studies will provide critical information on the appropriate selection of colistin therapy, as well as evaluating novel and upcoming compounds with structure and properties similar to the Polymyxin.

Prevalence of Colistin-resistant Gram-negative Isolates Carrying the mcr-1 Gene among Patients Visiting a Tertiary Care Center.

Gram-negative isolates harboring mobilized colistin resistance (mcr-1) gene are a great threat to human health. They have been reported worldwide among various bacterial isolates. This work aimed to study the prevalence of colistin resistance among Gram-negative bacteria and the incidence of mcr-1 gene among these isolates. A descriptive cross-sectional study was done at a tertiary care center from June 2016 to February 2017. An ethical approval was taken from review board of the Nepal Health Research Council (Reg. no: 274/2016). Convenience sampling was used. The data was collected and analyzed using Microsoft Excel 2010 and Statistical Package for Social Sciences (SPSS) Version 16 . Point estimate at 95% Confidence Interval was calculated along with frequency and proportion for binary data. Among 485 gram-negative isolates, only 13 (2.68%) (1.26-6.62 at 95% Confidence Interval) isolates were colistin-resistant and mcr-1 was present in two isolates. Predominant colistin-resistant isolates were E. coli 6 (4.1%), Enterobacter spp 2 (2.81%), and Acinetobacter spp 2 (2.81%). A high level of colistin-resistance was noted in 4 (30.7%) isolates as indicated by the very high value of colistin MIC (>256 μg/ml). ICU was the major site of isolation of colistin-resistant and mcr-1 positive pathogens. The majority of colistin-resistant isolates were highly drug-resistant and were sensitive only to polymyxin B. Antibiotics like imipenem, amikacin, gentamicin, aztreonam, ciprofloxacin, and piperacillin-tazobactam were effective for few of these isolates. Though the prevalence of mcr-1 gene was low among colistin-resistant gram-negative isolates, the resistant pattern was quite alarming as these isolates were highly drug-resistant.

Prevalence of Colistin Resistance in Escherichia coli in Eastern Turkey and Genomic Characterization of an mcr-1 Positive Strain from Retail Chicken Meat.

Colistin is one of the most effective antibiotics against multidrug resistant Gram-negative bacteria. However, the recent emergence of plasmid-borne mobilized colistin resistance (mcr) genes is considered a serious antimicrobial resistance challenge worldwide. In this study, we report detection of an mcr-1 carrying Escherichia coli isolate (named ATAVET mcr-1 Turkey) from retail raw chicken meat in Turkey. Of the 11 (from 500 total tested) phenotypically colistin-resistant isolates, 1 was shown to carry the mcr-1 gene by PCR. Whole-genome sequencing indicated that mcr-1 was located on a ∼13 kb-long contig that was almost identical to the corresponding part in pZJ1635, an IncI2 plasmid encoding mcr-1 in the same genetic context in another E. coli strain. In addition, ATAVET mcr-1 Turkey harbored blaCTX-M-8, qnrB19, mdf(A), tet(A), sul2, aph(3″)-Ib, aph(6)-Id, and floR resistance genes. Phylogenetic analysis based on whole genome and multilocus sequence typing indicated that ATAVET mcr-1 Turkey was more closely related to mcr-1 carrying E. coli isolates from food and human clinical samples previously reported from different parts of the world than to those from Turkey. These findings further emphasize the worldwide emergence and spread of mcr meditated colistin resistance in bacteria with zoonotic potential within animals and the food chain.

Colistin resistance in Gram-negative ocular infections: prevalence, clinical outcome and antibiotic susceptibility patterns.

To study the prevalence, antibiotic susceptibility profile, clinical outcomes and plasmid-mediated transfer of colistin resistance (CLR) among Gram-negative bacilli (GNB) isolates from different ocular infections. Prospective case-control study in eastern India. Consecutive ocular samples with GNB isolates from clinically diagnosed cases of microbial keratitis, infectious endophthalmitis and orbital infections were included. Inclusion criteria were significant GNB growth from ocular samples and > 6weeks follow-up. Clinical outcomes were determined by disease-specific criteria for each clinical group. Antibiotic susceptibility was tested by broth microdilution for colistin and Kirby-Bauer disc diffusion method for others. Plasmid detection for CLR genes mcr-1 and mcr-2 genes was done by standard protocols. Sixty GNB isolates were studied. Overall prevalence of CLR (intrinsic plus acquired) was 40% (n = 24), acquired being 37.5% of CLR isolates (n = 9). The prevalence varied from 45.5% (10/22) and 45% (9/20) in microbial keratitis and infectious endophthalmitis, respectively, to 26.3% (5/19) in orbital infections. Clinical outcomes in CLR patients were significantly worse in microbial keratitis (p = 0.018) and orbital infections (p = 0.018), and comparable to colistin-susceptible ones (p = 0.77) in infectious endophthalmitis. CLR isolates had significantly higher resistance to Amikacin, Gentamicin and Ceftazidime but were susceptible to Piperacillin, Carbapenems and fluoroquinolones. Plasmids mcr-1 and mcr-2 were detected in 6.25% (n = 1) and 25%(n = 4), respectively, of the 16 tested isolates. CLR is highly prevalent in ocular isolates and affects clinical outcomes. CLR isolates may still remain susceptible to Carbapenems, Piperacillin and fluoroquinolones. Plasmid mcr-1- and mcr-2-mediated CLR remains low in ocular infections.

Rapid detection of polymyxin resistance among carbapenem-resistant enterobacteriaceae

Background Colistin is used currently as a last-line antibiotic for the treatment of infections caused by carbapenem-resistant Enterobacteriaceae (CRE). For colistin-susceptibility testing, the conventional methods are not reliable, and the standard broth microdilution (BMD) method is both laborious and time consuming. Therefore, there is an urgent need for a rapid diagnostic technique for identification of colistin resistance. Aim The aim was to report the prevalence of CRE among hospitalized patients, to evaluate the performance of the rapid polymyxin Nordmann/Poirel (NP) test for detection of polymyxin resistance among CRE, and to detect the mcr-1 gene among these isolates. Patients and methods A total of 300 samples were included. CRE isolates were isolated and subjected to BMD test, disk diffusion test, E-test, and rapid polymyxin NP test to detect colistin resistance. In addition, PCR assay was done to detect mcr-1 gene. Results Out of 300 different clinical samples, 132 Enterobacteriaceae isolates were obtained. The prevalence of CRE was 41.7% (55/132). The prevalence of colistin resistance among CRE isolates was 7.3% (4/55). Of the four colistin resistant isolates detected by the standard BMD, disk diffusion test and E-test detected 2 and 3 isolates as colistin resistant, respectively, giving low sensitivity (50 and 75%, respectively) and unacceptably high rates of very major errors (3.6 and 1.8%, respectively), whereas all four isolates were recorded as colistin-unsusceptible by the rapid polymyxin NP test, giving 100% sensitivity and specificity, with no very major errors. Only one isolate was detected as mcr-1 positive by PCR assay. Conclusion There is a high prevalence of CRE. Rapid polymyxin NP test is an accurate and rapid method for detection of colistin resistance. This research confirms the alarming spread of the plasmid-mediated mcr-1 gene among CRE.

Prevalence and molecular determinants of colistin resistance among commensal Enterobacteriaceae isolated from poultry in northwest of Iran

BackgroundThe emergence of colistin-resistant Enterobacteriaceae from human and animal sources is a public health concern as this antibiotic is considered to be the last line therapeutic option for infections caused by multidrug-resistant Gram-negative bacteria. Here we aimed to determine the prevalence of colistin resistance, among enterobacteria isolated from poultry and the possible underlying colistin resistance mechanisms.MethodsA collection of 944 cloacal samples were obtained from poultry and screened for colistin resistance. To uncover the molecular mechanism behind colistin resistance, the presence of plasmid encoded colistin resistance genes mcr-1, mcr-2, mcr-3 and mcr-4 was examined by PCR. The nucleotide sequences of the mgrB, pmrA, pmrB, phoP, phoQ, crrA and crrB genes were determined. The genetic relatedness of the colistin resistant (ColR) isolates was evaluated by Multilocus sequence typing. Three ColR mutants were generated in vitro by repetitive drug exposure.ResultsOverall from 931 enteric bacteria isolated from poultry samples obtained from 131 farms, nine ColR bacteria (0.96%) with high level colistin resistance (MICs ≥ 64 mg/L) were detected all being identified as K. pneumoniae. The 9 ColR bacteria originated from different farms and belonged to 7 distinct Sequence types including ST11 (22.2%) and ST726 (22.2%) being the most prevalent STs followed by ST37, ST74, ST485, ST525 and novel sequence type 3380 (11.1% each). mcr-type genes were not detected in any isolate. In 88.8% of the isolates (n = 8), MgrB was inactivated by Insertion of IS elements (IS1-like, IS3-like, IS5-like families, positions + 75, + 113, + 117, + 135) and nonsense mutations at codons 8, 16, 30. All ColR isolates harboured wild type PmrA, PhoP, PhoQ or polymorphic variants of PmrB. Sequence analysis of the CrrB revealed a familiar S195N and 4 novel I27V, T150R, F303S and K325R substitutions. PmrB T93N substitution and mgrB locus deletion were identified in two laboratory induced ColR mutants and one mutant lacked alteration in the studied loci. In one ColR isolate with wild type MgrB an A83V substitution was detected in CrrA.ConclusionIt is concluded from our results that colistin resistance in the studied avian K. pneumoniae isolates was mostly linked to alterations identified within the mgrB gene.

Performance of CHROMID® Colistin R agar, a new chromogenic medium for screening of colistin-resistant Enterobacterales

Recent emergence of transferable plasmid-borne colistin resistance (mcr genes) raised fear for pan-resistance. We evaluated the performance of a new chromogenic medium [CHROMID® Colistin R agar (COLR)] for the screening of colistin-resistant Enterobacterales. Specificity was evaluated using 89 rectal swabs and 89 stools prospectively collected. COLR sensitivity was evaluated by seeding 59 negative clinical samples artificially contaminated (105 CFU/mL) with 59 colistin-resistant Enterobacterales, including 20 mcr-1–positive strains. Twelve samples with an Enterobacterales with nonintrinsic resistance to colistin were recovered during the specificity study, including one mcr-1–positive Escherichia coli, representing a 6.7% prevalence of colistin resistance in fecal carriage. Overall, specificity was 100.0% [95% CI: 97.8–100.0] and sensitivity yielded 88.1% [95% CI: 77.5–94.1]. False negatives corresponded to 3 Enterobacter spp. (MIC>64 mg/L), 2 Salmonella spp. (MIC = 16 mg/L), 1 E. coli (MIC = 4 mg/L), and 1 K. pneumoniae (MIC = 8 mg/L). COLR appears to be a sensitive and specific chromogenic agar for screening colistin-resistant Enterobacterales, including those carrying mcr-1 gene.

Dynamics of colistin and tobramycin resistance among Enterobacter cloacae during prolonged use of selective decontamination of the digestive tract

BackgroundA high prevalence of colistin resistance among E. cloacae isolates in two intensive care units (ICU) (of 16 and 6 beds) using selective digestive decontamination (SDD) since 1990 instigated a retrospective and prospective investigation to quantify the role of clonal transmission. SDD is topical application of colistin and tobramycin and systemic use of cefotaxime during the first days of ICU-admission.MethodsMulti-resistant E. cloacae (MREb) was defined as ESBL production and/or tobramycin non-susceptibility and/or colistin non-susceptibility. Incidence of acquisition and prevalence of carriage with MREb was determined from microbiological culture results.ResultsColistin-resistant E. cloacae was first detected in November 2009 and carriage was demonstrated in 141 patients until October 2014. Mean incidence of MREb acquisition was 4.61 and 1.86 per 1000 days at risk in ICUs 1 and 2, respectively, and the mean monthly prevalence of MREb in both ICUs was 7.0 and 3.1%, respectively, without a discernible trend in time. Conversion rates from carriage of colistin-susceptible to resistant E. cloacae were 0.20 and 0.13 per 1000 patient days, respectively. Whole genome sequencing of 149 isolates revealed eight clusters, with the number of SNPs of the largest two clusters ranging between 0 and 116 for cluster 1 (n = 49 isolates), and 0 and 27 for cluster 2 (n = 36 isolates), among isolates derived between 2009 and 2014.ConclusionsThis study demonstrates a stable low-level endemicity of MREb in two Dutch ICUs with prolonged use of SDD, which was characterized by the persistent presence of two clusters, suggesting incidental clonal transmission.

Multicenter prospective study on the prevalence of colistin resistance in Escherichia coli: relevance of mcr-1-positive clinical isolates in Lombardy, Northern Italy.

BackgroundThe emergence of the plasmid-mediated colistin resistance mechanism in Escherichia coli has raised concern among public health experts as colistin is a last-line antimicrobial resort. The primary aim of the study was to investigate the prevalence of this resistance trait in E. coli isolates circulating in the Lombardy region, Northern Italy. The presence of mcr-type genes and their genetic relationship were also studied.Materials and methodsA prospective study was performed during a 4-month period (May to August, 2016) in six acute care Hospitals. Consecutive nonduplicate clinical isolates of E. coli from any type of clinical specimen, with the exception of rectal swabs, were included in the study. Isolates that exhibited MIC values for colistin >2 mg/L were further investigated. Bacterial identification was obtained by matrix-assisted laser desorption ionization-time of flight mass spectrometry. Amplification of mcr-type genes (−1 to −5 variants) and microarray analysis were accomplished. Repetitive sequence-based PCR (Rep-PCR) and multilocus sequence typing (MLST) analysis were used for genotyping.ResultsOverall, 3,902 consecutive E. coli isolates (2,342 from outpatients, 1,560 from inpatients) were evaluated during the study period. Of them, 18/3,902 (0.5%), collected from 4/6 centers, showed resistance to colistin. These isolates were mostly obtained from urine of both outpatients (n=12) and inpatients (n=6). Colistin MIC values ranged from 4 to 8 mg/L. The mcr-1 gene was detected in 10/18 isolates (7 from outpatients, 3 from inpatients). Rep-PCR and MLST analysis revealed the presence of nine different clusters. Further mcr-type genes were not detected.ConclusionResistance to colistin in E. coli clinical isolates appears low in our geographic area. With regard to mcr-1-positive isolates, they accounted for approximately 50% of colistin-resistant E. coli isolates, thus representing a relevant resistance mechanism in this context. Although overall limited, the presence of mcr-1 determinant in our region should not be ignored and great concern should be given to the continuous surveillance.