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Background: The frequent use of broad-spectrum antibiotics in ICU leads to increased rates of antimicrobial resistance and occurrence of multidrug-resistant (MDR) micro-organisms. The aim of this study was to evaluate the antimicrobial resistance pattern and colistin susceptibility among bacterial isolates from ICU patients. Method: It is a prospective study with 70 nonrepetitive isolates from ICU samples. The clinical data was obtained from the department records. The gram-negative bacterial isolates were identified by conventional biochemical tests. The antimicrobial susceptibility was determined by Kirby-Bauer disc diffusion method. ESBL producers were detected by double disc diffusion test using ceftazidime, cefotaxime alone and in combination with clavulanic acid. MBL detection was done by imipenem+ EDTA combined disc diffusion test. Colistin sensitivity was determined by broth microdilution according to CLSI guidelines. Results: Out of 70 culture positive specimens. The most common gram-negative bacteria isolated from the samples was Acinetobacter spp. (41%), followed by Klebsiella spp. (20%). Among these 45% were MBL producers, 38.5% were ESBL producers and 14% were both ESBL and MBL producers. Colistin resistance was present among 5.7% isolates in ICU. Conclusions: Non-fermenters were the most common agent causing ICU infections. An alarmingly high rate of resistance to antibiotics especially to colistin in ICU-acquired infections, necessitates new therapeutic strategies to prevent the emergence and control of antimicrobial resistance.
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Background: The frequent use of broad-spectrum antibiotics in ICU leads to increased rates of antimicrobial resistance and occurrence of multidrug-resistant (MDR) micro-organisms. The aim of this study was to evaluate the antimicrobial resistance pattern and colistin susceptibility among bacterial isolates from ICU patients. Method: It is a prospective study with 70 nonrepetitive isolates from ICU samples. The clinical data was obtained from the department records. The gram-negative bacterial isolates were identified by conventional biochemical tests. The antimicrobial susceptibility was determined by Kirby-Bauer disc diffusion method. ESBL producers were detected by double disc diffusion test using ceftazidime, cefotaxime alone and in combination with clavulanic acid. MBL detection was done by imipenem+ EDTA combined disc diffusion test. Colistin sensitivity was determined by broth microdilution according to CLSI guidelines. Results: Out of 70 culture positive specimens. The most common gram-negative bacteria isolated from the samples was Acinetobacter spp. (41%), followed by Klebsiella spp. (20%). Among these 45% were MBL producers, 38.5% were ESBL producers and 14% were both ESBL and MBL producers. Colistin resistance was present among 5.7% isolates in ICU. Conclusions: Non-fermenters were the most common agent causing ICU infections. An alarmingly high rate of resistance to antibiotics especially to colistin in ICU-acquired infections, necessitates new therapeutic strategies to prevent the emergence and control of antimicrobial resistance.
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BACKGROUND Pandrug-resistant (PDR) Klebsiella pneumoniae has been reported sporadically in many countries and remains rare in Brazil. OBJECTIVES This study unravelled the genetic determinants involved with the PDR background of a clinical ST11 K. pneumoniae recovered in the Brazilian Amazon Region, where K. pneumoniae genomic and epidemiological information is scarce. METHODS Kp196 was submitted to the antimicrobial susceptibility test by the disk-diffusion method and minimum inhibitory concentration (MIC) determination. The whole genome sequencing was obtained and the sequence type was determined by core genome multilocus sequence typing (cgMLST). Its intrinsic and acquired resistome was assessed by Comprehensive Antibiotic Resistance Database (CARD) and comparison with wild-type genes. FINDINGS The analyses revealed that Kp196 belonged to the pandemic ST11 and presented the PDR phenotype. Its acquired resistome was composed of a huge set of clinically relevant resistance determinants, including bla CTX-M-15 and bla NDM-1, all found in the vicinity of mobile platforms. Considering its intrinsic resistome, the multidrug resistance, especially to colistin, tigecycline and fluoroquinolones, was multifactorial and attributed to modifications (indels, missense mutations, and gene disruption) in several housekeeping genes (arnT/phoQ/mgrB/ramR/acrB/gyrA/parC/ompK35-36-37). The Kp196 intrinsic resistome was also observed in a ST11 environmental strain, although harbouring distinct acquired resistomes. CONCLUSIONS An accumulation of different resistance mechanisms regarding the intrinsic resistome accounts for a more stable resistome, strongly contributing to the Kp196 PDR phenotype.
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Resumen Utilizando cepas clínicas de bacilos gramnegativos multi-resistentes (MDR), comparamos las CIM obtenidas de la microdilución en caldo, el método de referencia y el método de elución de sensidiscos. Encontramos que, con la excepción de A. baumannii, los resultados fueron muy similares. El método de elución de sensidiscos podría ser una buena alternativa y confiable para la determinación de la resistencia a colistín.
Abstract Using clinical strains of multidrug resistant (MDR) Gram negative bacilli, we compared MICs obtained from both broth microdilution, the reference method, and sensi-disk elution method. We found that, with A. baumannii exception, results were very similar. Sensi-disk elution method could be a good and reliable alternative for colistin resistance determination.
Subject(s)
Microbial Sensitivity Tests/methods , Microbial Sensitivity Tests/standards , Colistin/pharmacology , Gram-Negative Bacteria/drug effects , Anti-Bacterial Agents/pharmacology , Drug Resistance, Multiple, Bacterial , Acinetobacter baumannii/drug effectsABSTRACT
ABSTRACT Global dissemination of mcr-like genes represents a serious threat to public health since it jeopardizes the effectiveness of colistin, an antibiotic used as a last-resort treatment against highly antibiotic-resistant bacteria. In 2017, a mcr-1-positive isolate of Escherichia coli was found in Chile for the first time. Herein we report the genetic features of this strain (UCO-457) by whole-genome sequencing (WGS) and conjugation experiments. The UCO-457 strain belonged to ST4204 and carried a 285 kb IncI2-type plasmid containing the mcr-1 gene. Moreover, this plasmid was transferred by conjugation to an E. coli J53 strain at high frequency. The isolate harbored the cma, iroN, and iss virulence genes and did carry resistance genes to trimethoprim/sulfamethoxazole and fluoroquinolones. Other antibiotic resistance determinants such as β-lactamases-encoding genes were not detected, making the isolate highly susceptible to these antibiotics. Our results revealed that such susceptible isolates could be acting as platforms to disseminate plasmid-mediated colistin resistance. Based on this evidence, we consider that mcr-like prevalence deserves urgent attention and should be examined not only in highly resistant bacteria but also in susceptible isolates.
Subject(s)
Humans , Escherichia coli Proteins/genetics , Escherichia coli/genetics , Escherichia coli Infections/microbiology , Outpatients , Chile , Escherichia coli/drug effects , Disk Diffusion Antimicrobial Tests , Anti-Bacterial Agents/pharmacologyABSTRACT
Colistin resistance can occur by chromosomal mutations and by acquisition of plasmid-carrying determinants, mainly mcr-1. In the recent years, we have observed the out-burst of this resistance gene in our region. Due to the risk of the rapid dissemination of mcr-1, this finding has worried and alerted different actors from the health field and has become one of the most prolific topics. Our review compiles available reports of well-documented mcr-1-positive strains of Enterobacteriaceae, obtained from different samples in Argentina and other countries of Latin America. Furthermore, it addresses the association of mcr-1 with ESBL resistance markers and outlines the platforms involved in their dissemination.
La resistencia a la colistina puede ocurrir por mutaciones cromosómicas o por la adquisición de determinantes localizados en plásmidos, el principal es mcr-1. En los últimos años hemos observado la explosiva aparición de este gen de resistencia en nuestra región. Debido al riesgo que implica la rápida diseminación de mcr-1, este hallazgo ha preocupado y alertado a los diferentes actores del área de la salud, y se ha convertido en uno de los temas de investigación más importantes. La presente revisión compila los informes de aislamientos portadores de mcr-1 debidamente documentados en Enterobacteriaceae, obtenidos de diferentes muestras en Argentina y otros países de América Latina. Además, aborda la asociación de mcr-1 con otros marcadores de resistencia, como las BLEE, y describe las plataformas involucradas en su diseminación.
Subject(s)
Plasmids/agonists , Colistin/antagonists & inhibitors , Association , R Factors/analysis , Biomarkers , Enterobacteriaceae/isolation & purificationABSTRACT
Background & objectives: The increasing prevalence of extended-spectrum ?-lactamases (ESBLs) has abated therapeutic options worldwide. This study was undertaken to investigate the molecular profile and resistance patterns of ESBLs among clinical isolates of Escherichia coli and Klebsiella pneumoniae at four tertiary care centres in India. Methods: Clinical isolates of E. coli and K. pneumoniae were collected from the All India Institute of Medical Sciences (AIIMS), New Delhi; the Jawaharlal Institute of Postgraduate Medical Education & Research (JIPMER), Puducherry; Postgraduate Institute of Medical Education & Research (PGIMER), Chandigarh and Christian Medical College (CMC), Vellore, over one and a half year period. Antimicrobial susceptibility was determined by Kirby-Bauer disc diffusion method. ESBLs were confirmed phenotypically, and multiplex PCR was performed to identify genes for ?-lactamases (blaTEM, blaSHV, blaOXA-1, blaCTXM-1, blaCTXM-2, blaCTXM-9 and blaCTXM-15). Results: Among 341 E. coli isolates collected during the study period, 171 (50%) harboured blaTEM, 145 (43%) blaOXA-1,70 (21%) blaCTXM-1, 19 (6%) blaSHV and four (1%) harboured blaCTXM-2. Phenotypically, combined disc test detected ESBL production in 98/298 (33%) E. coli. Among 304 K. pneumoniae isolates, 115 (38%), 89 (29%), 83 (27%), 64 (21%) and two (0.6%) harboured blaTEM, blaOXA-1, blaCTXM-1, blaSHV and blaCTXM-2, respectively. Combined disc test (CDT) detected ESBL production in 42 per cent K. pneumoniae. Most of the blaCTXM-1positive isolates were also blaCTXM-15 positive. The carbapenem susceptibility ranged from 56 to 88 per cent for E. coli and from 20 to 61 per cent for K. pneumoniae. Antibiotic sensitivity patterns showed that colistin (CST) was the most sensitive drug for both E. coli (271/274, 99%) and K. pneumoniae (229/234, 98%). Interpretation & conclusions: The prevalence of ESBL among four study centres varied, and blaTEM, blaOXA-1 and blaCTXM-15 were the most common genotypes in E. coli and K. pneumoniae isolates in India. The growing carbapenem resistance and emerging colistin resistance warrant the judicious use of these antimicrobials.
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Background & objectives: Klebsiella pneumoniae (KP), a common cause of invasive infections, is often extensively drug resistant in India. At present, studies on resistance mechanism and clonal relationship of KP from India are limited. The present study was undertaken to determine the resistance mechanism and clonal relationship of colistin-resistant isolates obtained from various specimens. Carbapenemases were also determined since the isolates were carbapenem resistant. Methods: Sixty five isolates from blood, exudates and respiratory specimens collected between 2016 and 2017 were studied. Colistin minimum inhibitory concentration (MIC) was performed by broth-micro dilution method. Multiplex PCR was carried out to determine carbapenemases. Targeted sequencing was performed to determine mutations in mgrB, phoP, phoQ and multilocus sequence typing was performed to determine the prevalent clones. Results: Colistin MIC ranged from 4 to 256 ?g/ml. SHV, TEM and CTX-M were co-produced in 60 per cent and OXA48-like in 71 per cent. Thirteen isolates had mutations in mgrB. Mutations included a premature stop codon at 21st amino acid, the presence of insertion sequences such as IS903, IS Kpn 14 and ISK pn 26; and elongation of mgrB. Novel mutations were also observed among phoP and phoQ genes. Colistin resistance due to mcr genes was absent. Fifteen clonal types were seen with ST231, ST14 and ST2096 being predominant. Interpretation & conclusions: This study revealed the changing trend of carbapenem resistance mechanism predominantly to OXA48-like from NDM. Known mgrB mutations and novel mutations in phoP and phoQ were detected. There was no plasmid-mediated colistin resistance. ST14 and ST231 were international clones associated with carbapenem resistance. Colistin-resistant KP was of diverse clones with predominantly ST231, ST14 and ST2096.
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Abstract INTRODUCTION: The increased use of colistin against infections caused by Acinetobacter baumannii and Pseudomonas aeruginosa has resulted in colistin resistance. The purpose of this study was to detect plasmid-mediated mcr-1 gene in colistin-resistant A. baumannii and P. aeruginosa isolates. METHODS: A total of 146 clinical isolates of A. baumannii (n = 62) and P. aeruginosa (n = 84) were collected from the four largest tertiary care hospitals in Peshawar, Pakistan. All bacterial isolates were phenotypically screened for multidrug resistance using the Kirby-Baur disc diffusion method. The minimum inhibitory concentration (MIC) of colistin in all isolates was phenotypically performed using dilution methods. mcr-1 gene was detected through polymerase chain reaction and the nucleotide sequence of amplicon was determined using Sanger sequencing. RESULTS: Approximately 96.7% A. baumannii and 83.3% P. aeruginosa isolates were resistant to multiple antibiotics. Colistin resistance was found in 9.6% (6/62) of A. baumannii and 11.9% (10/84) of P. aeruginosa isolates. Among 16 colistin resistant isolates, the mcr-1 gene was detected in one A. baumannii (1.61% of total isolates; 16.6% of colistin resistant isolates) and one P. aeruginosa strain (1.19% of total isolates; 10% of colistin resistant isolates). Nucleotide BLAST showed 98-99% sequence similarity to sequences of the mcr-1 gene in GenBank. CONCLUSIONS: Our study reports, for the first time, the emergence of plasmid-mediated mcr-1-encoded colistin resistance in multidrug resistant strains of A. baumannii and P. aeruginosa. Further large scales studies are recommended to investigate the prevalence of this mode of resistance in these highly pathogenic bacteria.
Subject(s)
Humans , Pseudomonas aeruginosa/genetics , Pseudomonas Infections/microbiology , Bacterial Proteins/genetics , Acinetobacter Infections/microbiology , Acinetobacter baumannii/genetics , Pakistan , Plasmids/genetics , Pseudomonas aeruginosa , Microbial Sensitivity Tests , Drug Resistance, Bacterial , Acinetobacter baumannii/drug effectsABSTRACT
Recently it was described the plasmidial gene mcr-1 associated with colistin resistance. We screened by PCR and sequencing for gene mcr-1 in thirteen clinical isolates resistant to colistin. We observed amplification in one E. coli. To our knowledge, this is the first report of the presence of mcr-1 gene in Chile.
Subject(s)
Colistin/pharmacology , Escherichia coli Proteins/isolation & purification , Drug Resistance, Bacterial/genetics , Escherichia coli/isolation & purification , Escherichia coli/genetics , Anti-Bacterial Agents/pharmacology , Microbial Sensitivity Tests , Escherichia coli/drug effects , Escherichia coli Infections/microbiologyABSTRACT
BACKGROUND: The emerging mobile colistin resistance gene, mcr-1, is an ongoing worldwide concern and an evaluation of clinical isolates harboring this gene is required in Korea. We investigated mcr-1-possessing Enterobacteriaceae among Enterobacteriaceae strains isolated in Korea, and compared the genetic details of the plasmids with those in Escherichia coli isolates from livestock. METHODS: Among 9,396 Enterobacteriaceae clinical isolates collected between 2010 and 2015, 1,347 (14.3%) strains were resistant to colistin and those were screened for mcr-1 by PCR. Colistin minimum inhibitory concentrations (MICs) were determined by microdilution, and conjugal transfer of the mcr-1-harboring plasmids was assessed by direct mating. Whole genomes of three mcr-1-positive Enterobacteriaceae clinical isolates and 11 livestock-origin mcr-1-positive E. coli isolates were sequenced. RESULTS: Two E. coli and one Enterobacter aerogenes clinical isolates carried carried IncI2 plasmids harboring mcr-1, which conferred colistin resistance (E. coli MIC, 4 mg/L; E. aerogenes MIC, 32 mg/L). The strains possessed the complete conjugal machinery except for E. aerogenes harboring a truncated prepilin peptidase. The E. coli plasmid transferred more efficiently to E. coli than to Klebsiella pneumoniae or Enterobacter cloacae recipients. Among the three bacterial hosts, the colistin MIC was the highest for E. coli owing to the higher mcr-1-plasmid copy number and mcr-1 expression levels. Ten mcr-1-positive chicken-origin E. coli strains also possessed mcr-1-harboring IncI2 plasmids closely related to that in the clinical E. aerogenes isolate, and the remaining one porcine-origin E. coli possessed an mcr-1-harboring IncX4 plasmid. CONCLUSIONS: mcr-1-harboring IncI2 plasmids were identified in clinical Enterobacteriaceae isolates. These plasmids were closely associated with those in chicken-origin E. coli strains in Korea, supporting the concept of mcr-1 dissemination between humans and livestock.
Subject(s)
Humans , Colistin , Enterobacter aerogenes , Enterobacter cloacae , Enterobacteriaceae , Escherichia coli , Escherichia , Genome , Klebsiella pneumoniae , Korea , Livestock , Microbial Sensitivity Tests , Plasmids , Polymerase Chain ReactionABSTRACT
Objective To establish a sensitive real-time quantitative PCR assay with TaqMan probe for rapid detection of mcr-1 gene in clinical isolated strains. Methods According to the mcr-1 gene sequence, a pair of specific primers and a TaqMan probe were designed. Moreover, a recombinant plasmid with mcr-1 gene was constructed as the positive standard. TaqMan probe-based fluorescence quantitative PCR assay was used to detect the colistin resistance gene mcr-1. The sensitivity, repeatability and specificity of the assay were evaluated. Results There was a good linear relationship between the initial template amount and Ct value (R2>0. 999). The lower limit of detection was 10 copies/μL, which was 100 times more sensitive than the conventional PCR. Results of test for specificity showed that only the strains carrying the mcr-1 gene were positive, while the remaining strains were negative. Coefficients of variation of intra-and inter-group repeatability tests were less than 1％. Two out of 150 clinical isolated strains carried mcr-1 re-sistance gene and both of them were identified as Escherichia coli. Conclusion TaqMan probe-based fluo-rescence quantitative PCR for the detection of colistin resistance gene mcr-1 was established with strong spe-cificity, high sensitivity and good repeatability. It could be used for the specific detection of clinical drug-re-sistant strains positive for mcr-1 gene and provide reference for pharmacotherapy.
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OBJECTIVE: We describe an IncX4 pHC891/16mcr plasmid carrying mcr-1 in a colistin-resistant and carbapenem-susceptible E. coli isolate (HC891/16), ST156, which caused a blood infection in a Brazilian patient with gallbladder adenocarcinoma. METHODS: Strain HC891/16 was subjected to whole genome sequencing using the MiSeq Platform (Illumina, Inc., USA). Assembly was performed using Mira and ABACAS. RESULTS: The isolates showed resistance only to ciprofloxacin, ampicillin and cefoxitin, and whole-genome sequencing revealed the presence of aac(6')Ib-cr and blaTEM1. CONCLUSION: Our findings warn of the possible silent dissemination of colistin resistance by carbapenem-susceptible mcr-1 producers, as colistin susceptibility is commonly tested only among carbapenem-resistant isolates.
Subject(s)
Humans , Female , Aged , Carbapenems/pharmacology , Bacteremia/drug therapy , Colistin/pharmacology , Escherichia coli Proteins/drug effects , Escherichia coli/drug effects , Anti-Bacterial Agents/pharmacology , Plasmids/drug effects , Brazil , Microbial Sensitivity Tests , Escherichia coli Proteins/isolation & purification , Escherichia coli Proteins/genetics , Drug Resistance, Multiple, Bacterial , Escherichia coli/isolation & purification , Escherichia coli/genetics , Escherichia coli Infections/drug therapyABSTRACT
Objective To investigate the prevalence of colistin resistance and mcr-1 gene in pa-tients with bloodstream infection caused by Escherichia coli (E.coli) and Klebsiella pneumoniae (K.pneu-moniae) in Zhejiang Province. Methods A total of 869 clinical strains of the Enterobacteriaceae family, including 611 E.coli and 258 K.pneumonia strains, were isolated from patients with bloodstream infection (BSI) in Zhejiang Province from March 2014 to April 2015. Broth microdilution method and PCR were re-spectively performed to detect colistin resistance and mcr-1 gene in those stains. Susceptibilities of mcr-1-positive strains to other antibiotics were assessed by E-test. Pulsed-field gel electrophoresis(PFGE) and multilocus sequence typing(MLST) were used for molecular typing. Location of mcr-1 gene was determined by analysis of PFGE profiles of S1-digested genomic DNA and Southern blot hybridization. Plasmid transfer to E.coli recipients was investigated using filter mating test. Clinical data of the patients infected with mcr-1-positive strains was collected and analyzed. Results The minimum inhibitory concentration (MIC) values of colistin to the 869 Enterobacteriaceae strains ranged from ≤0.06 μg/ml to 16 μg/ml. Six (0.69%) E.coli strains were identified to be colistin-resistant and mcr-1-positive and the MIC values against them ranged from 8 μg/ml to 16 μg/ml. No colistin-resistant or mcr-1-positive K.pneumonia strain was identified. All mcr-1-positive strains were susceptible to carbapenems and most of them(83.33%,5/6) were suscepti-ble to tigecycline and β-lactamase inhibitor combinations tested in this study. The six mcr-1-positive strains were of different sequence types (STs) and the mcr-1 genes carried by them located on three types of plas-mids with the sizes of 33 kb,61 kb and 244.4 kb. Conclusion The prevalence of mcr-1 gene in E.coli and K.pneumonia strains isolated from patients with BSI in Zhejiang Province was relatively low, only ac-counting for 0.69% of all isolated Enterobacteriaceae strains.Those strains carrying mcr-1 gene showed low drug resistance to colistin. The mcr-1-positive strains were usually non-pathogenic clones and remained sus-ceptible to many antimicrobial agents, which was conducive to favorable outcomes. In order to clarify the clinical impact of this novel resistance gene on public health,further studies should be conducted.