Colistin Usage Research Articles

Occurrence and Characteristics of Mcrs among Gram-Negative Bacteria Causing Bloodstream Infections of Infant Inpatients between 2006 and 2019 in China.

ABSTRACTThe aim of this study was to determine the occurrence of mobilized colistin resistance (mcr) genes in Gram-negative bacteria causing bloodstream infections of child inpatients in China. Bacteria were collected between 2006 and 2019 in a maternal and child health hospital, and mcr genes were screened by PCR. Five of 252 isolates were mcr-positive, including one mcr-1-positive colistin-resistant Escherichia coli isolate, two mcr-9-positive colistin-susceptible Salmonella enterica isolates, and two mcr-9-positive colistin-susceptible Enterobacter hormaechei isolates. These were obtained from two neonate and three infant patients admitted between 2009 and 2018. The E. coli isolate was obtained from a neonate aged 20 min, suggestive of a possible mother-to-neonate transmission. The five mcr-positive isolates were multidrug resistant, and two S. enterica and one E. hormaechei isolate showed a hypervirulent phenotype compared to a hypervirulent Klebsiella pneumoniae type strain in a Galleria mellonella infection model. The mcr-1 gene was carried by an IncX4-type pA1-like epidemic plasmid, and the mcr-9 gene was detected on IncHI2/2A-type novel plasmids co-carrying multiple resistance genes. The four IncHI2/2A-type plasmids shared a backbone and a high similarity (≥77% coverage and ≥ 90% nucleotide identity), suggesting that they were derived from a common ancestor with cross-species transmission and have circulated locally over a long period. The conjugation assay showed that the mcr-1-encoding plasmid and one mcr-9-encoding plasmid were self-transmissible to E. coli with high conjugation frequencies. Our findings demonstrate that mcr genes have disseminated in the community and/or hospitals, mediated by epidemic/endemic plasmids over a long period. The study shows that continuous monitoring of mcr genes is imperative for understanding and tackling their dissemination.IMPORTANCE Antimicrobial resistance, especially the spread of carbapenemase-producing Enterobacteriaceae (CPE), represents one of the largest challenges to One Health coverage of environmental, animal, and human sectors. Colistin is one of the last-line antibiotics for clinical treatment of CPE. However, the emergence of the mobilized colistin resistance (mcr) gene largely threatens the usage of colistin in the clinical setting. In this study, we investigated the existence of mcr genes in 252 Gram-negative bacteria collected between 2006 and 2019 which caused bloodstream infections of child inpatients in China. We found a high prevalence of mcr carriage among children inpatients in the absence of professional exposure, and mcr might have widely disseminated in the community via different routes. This study emphasizes the importance of rational use of colistin in the One Health frame, and highlights both the urgent need for understanding the prevalence and dissemination of mcr genes in different populations and the importance of effective measures to control their spread.

Evaluation of Vitek2 and Colistin broth disk elution test in comparison with Micro broth dilution for Susceptibility testing of Colistin among Carbapenem Resistant Enterobacterales.

Colistin is the last expedient for treating the infections caused by Carbapenem resistant Enterobacter ales (CRE).Expanding usage of colistin as led to development of Colistin resistance. This urges for a need of reliable and accuratetesting method that can be adopted as routine for susceptibility testing of Colistin. The innate cationic property ofcolistin molecules is associated with complexities. Hence evaluation of testing method is needed for detection of colistinresistance. Present study is done to evaluate the results yielding from Vitek2 and CBDE in comparison with rBMD. About200 CRE isolated from clinical specimens were tested, results of Vitek2, CBDE was compared with rBMD. In comparisonwith BMD Categorical agreement (CA) of Vitec 2 was 83% with major error of 17% .CA of CBDE was 99% with 1% of verymajor error. Since the resistance to colistin is increasing accurate reporting of Colistin MIC by a validated method becomesimportant. So, we would recommend CBDE for routine testing of Colistin susceptibility.

Colistin-Induced Acute Kidney Injury and the Effect on Survival in Patients with Multidrug-Resistant Gram-Negative Infections: Significance of Drug Doses Adjusted to Ideal Body Weight.

Background Colistin is a lifesaving treatment for multidrug-resistant Gram-negative bacterial (MDR-GNB) infections along with its well-known nephrotoxicity. The controversy of colistin-induced acute kidney injury (AKI) on mortality is noted. This study aimed to determine the risk factors and impact of AKI on the survival and significance of colistin dosage. Methods A retrospective cohort study was performed in adult patients who received intravenous colistin for MDR-GNB treatment between June 2015 and June 2017. Factors influencing colistin-induced AKI and survival were evaluated by Cox regression analysis. Cut-off levels of the colistin dose per ideal body weight (IBW) that significantly affected clinical outcomes were assessed with linearity trends and receiver operating characteristic analyses. Results AKI occurred in 68.5% of 412 enrolled patients with an incidence rate of 10.6 per 100 patients-days and a median time was 6 (3–13) days. Stages I–III of AKI were 38.3, 24.5, and 37.2%. Factors associated with colistin-induced AKI were advanced age, high serum bilirubin, AKI presented before colistin administration, increased daily colistin doses per IBW, and concomitant use of nephrotoxic drugs. Colistin-induced AKI was related to mortality (HR 1.74, 95% CI 1.06–2.86, p=0.028). In the non-AKI before colistin usage subgroup, the total dose and total dose/IBW were >1,500–2,000 mg and 30–35 mg/kg to benefit mortality reduction but were <2,500–3,000 mg and 45–50 mg/kg for risk reduction of AKI. A daily colistin dose/IBW >4.5 mg/kg/day also increased the risk of AKI. In the AKI developed before colistin subgroup, the cut-off values of total colistin dose >1250–1350 mg and total dose/IBW >23.5–24 mg/kg demonstrated significant risks of AKI. Conclusion The incidence of AKI after colistin administration was high and impacted mortality. Prevention and early correction of these related factors are mandatory. Careful use of colistin was also both beneficial in mortality and AKI reductions.

Prevalence and zoonotic transmission of colistin-resistant and carbapenemase-producing Enterobacterales on German pig farms

The treatment of infections due to colistin-resistant (Col-E) and carbapenemase-producing (CPE) Enterobacterales challenges clinicians both in human and veterinary medicine. Preventing zoonotic transmission of these multidrug-resistant bacteria is a Public Health priority.This study investigates the prevalence of Col-E and CPE on 81 pig farms in North-West Germany as well as among 138 directly exposed humans working on these farms. Between March 2018 and September 2020, 318 samples of porcine feces were taken using boot swabs. Farm workers provided a stool sample. Both a selective culture-based approach and a molecular detection of colistin (mcr-1 to mcr-5) and carbapenem resistance determinants (blaOXA-48/blaVIM/blaKPC/blaNDM) was used to screen all samples. Isolates from farm workers and farms were compared using core genome multilocus-sequence typing (cgMLST) and plasmid-typing.CPE were cultured neither from porcine feces nor from human stool samples. In one stool sample, blaOXA-48 was detected, but no respective CPE isolate was found. Col-E were found in 18/318 porcine (5.7%) samples from 10/81 (12.3%) farms and 2/138 (1.4%) farmers, respectively. All Col-E isolates were Escherichia coli harboring mcr-1. Both farm workers colonized with Col-E worked on farms where no Col-E were detected in porcine samples.In conclusion, CPE were absent on German pig farms. This supports findings of culture-based national monitoring systems and provides evidence that even when improving the diagnostic sensitivity by using molecular detection techniques in addition to culture, CPE are not prevalent. Col-E were prevalent in porcine feces despite a recent decrease in colistin usage among German livestock and absence of colistin treatments on the sampled farms. Farmers carried Col-E, but zoonotic transmission was not confirmed.

Evaluation of efflux pumps overexpression and β-lactamase genes among colistin resistant Pseudomonas aeruginosa

Pseudomonas aeruginosa (PA) is one of the major factors in severe opportunistic and hospital-acquired infections. Structural mechanisms such as resistance–nodulation–division (RND) efflux pumps and drug resistance genes such as extended-spectrum β-lactamases (ESBLs) and metallo-β-lactamases (MBLs) are factors causing drug resistance. Colistin is the prominent therapeutic strategy with an excellent inhibitory role for combating multidrug-resistant (MDR) and extensively drug-resistant (XDR) isolates. Wide usage of colistin and genetics interactions leads to the emergence of colistin-resistant (CoR) PA isolates which is a dangerous occurrence in XDR-PA isolates. The current study investigates the presence and expression of PA-related RND genes and harboring the antibiotic resistance genes such as ESBL and MBL genes in CoR-PA strains.70 clinical isolates were obtained from different clinical specimens during 2019–2020. The antimicrobial susceptibility testing was performed by the both Kirby-Bauer disk agar diffusion method and the minimum inhibitory concentration (MIC). Presence of blaTEM-1, blaSHV, blaCTX-M, blaIMP, blaVIM and blaNDM was measured in all CoR-PA isolates. Besides, screening of mcr-1, aadA, aadB and efflux pump genes (mexA, mexD, mexE and mexY) was conducted for CoR-PA isolates. To determine the expression level of efflux pump genes, Quantitative real-time PCR (qRT-PCR) reactions were performed.According to the standard antimicrobial susceptibility methods 39 isolates, (55.7%) and 31 isolates (44.3%) were considered as MDR-PA and XDR-PA strains, respectively. 12 isolates (17.1%) displayed resistance to colistin using MIC assessment. All CoR-PA isolates were negative for mcr-1 gene. The blaSHV (n = 11, 91.6%) and blaNDM (n = 7, 58.3%) were the most prevalent ESBL and MBL genes among CoR-PA, respectively. PCR results showed all CoR-PA isolates were positive for all 4 efflux pumps genes. On the other hand, overexpression of MexA, MexD, MexE and MexY genes was observed in 5 (41.6%), 5 (41.6%), 5 (41.6%) and 6 (50%) CoR-PA isolates by qRT-PCR, respectively. 9 (75%) CoR-PA isolates overexpressed at least one of the four efflux pumps and overexpression of altogether 4 efflux pumps was shown in 2 (16.6%) CoR-PA isolates. Overexpression of MexA, MexD, MexE and MexY genes was associated to the resistance toward imipenem, ciprofloxacin, ceftazidime and aminoglycosides, respectively.The current research demonstrated the co-existence of CoR-PA with ESBL and MBL genes besides overexpression of efflux pumps. The distribution of such isolates can lead to a burden on the healthcare system by the incidence of the most crucial situation named pan-drug resistant PA strains.

A retrospective review of colistin utilisation at a tertiary care academic hospital in South Africa.

BackgroundThe use of the antibiotic colistin was increasing as a treatment option for multidrug-resistant (MDR) infections. Standardisation of colistin dosing and more appropriate record-keeping practices were required to fully assess the optimal usage of colistin. The aim of this study was to determine how and why colistin was used in the treatment of MDR infections in a tertiary care public hospital in South Africa (SA).MethodsThis cross-sectional retrospective record review described adult and paediatric patients who received colistin intravenously from 01 May 2016 to 31 April 2017. Information from patient records were captured on a data collection tool and analysed using descriptive statistics. Ethical approval was obtained from the Human Research Ethics Committee of the University of the Witwatersrand.ResultsA total of 43 patient records were reviewed. Acinetobacter baumannii was the most common organism isolated (85.2% adults and 62.5% paediatrics). Colistin was mostly prescribed for sepsis (18 adults and 15 paediatrics). Most adults (66.7%) received loading doses as recommended; however, there was a great variation in maintenance doses. Paediatric patients reviewed also showed varying dosing according to weight. The mean duration of colistin therapy was 10 days. Carbapenems were most commonly co-administered with colistin (58%).ConclusionThe findings suggested that although colistin usage was restricted in the hospital, it was not adequately monitored or controlled. Doses prescribed were made at the discretion of prescribing doctors and differed to currently accepted guidelines. Improved record-keeping practices related to the monitoring of colistin use were required.

WGS Analysis of Clonal and Plasmidic Epidemiology of Colistin-Resistance Mediated by mcr Genes in the Poultry Sector in Lebanon.

Poultry and poultry meat are important contributors to the global antimicrobial burden. Unregulated and illegal use of extended-spectrum cephalosporins (ESC) in this sector has long been identified as a major cause of massive spread of ESC-resistant Escherichia coli, and colistin usage is considered a main driver of plasmid-mediated mcr genes dissemination. In Lebanon, the first mcr-1-positive E. coli found in poultry dates back to 2015, followed by a few reports of mcr-1-positive E. coli in poultry, swine, humans, and the environment. On the contrary, a comprehensive picture of the population structure of mcr-1-positive E. coli and mcr-1-bearing plasmids carrying the mcr-1 gene using whole-genome analysis is largely lacking. This study reports the prevalence of mcr-1-positive E. coli in poultry originating from 32 farms across three Lebanese governorates and slaughtered in the same place. We report 27/32 (84.4%) mcr-1 positive farms, leading to a total of 84 non-duplicate E. coli collected, of which 62 presented the mcr-1 gene. Numerous associated resistances were identified, including to ESC through the presence of blaCTX–M or blaCMY genes. The mcr-1 gene was mostly carried by IncX4 (n = 36) and IncI2 (n = 24) plasmids, which are both known for their efficient transfer capacities. A high genetic diversity was detected, arguing for the lack of contamination during the slaughter process. ST744 and ST1011 were the most widely identified clones, which have been both regularly associated to mcr-1-carrying E. coli and to the poultry sector. The wide dissemination of colistin-resistance, coupled to resistances to ESC and numerous other molecules, should urge authorities to implement efficient guidelines for the use of antibiotics in the poultry sector in Lebanon.

Predictors of Acute Kidney Injury and 28-Day Mortality in Carbapenem-Resistant Acinetobacter baumannii Complex Bacteremia.

Colistin is an, antibiotic used to treat carbapenem-resistant Acinetobacter baumannii complex (CRABC) infection. However, colistin is well known for its nephrotoxicity. To accurately assess the effects of colistin on acute kidney injury (AKI) and 28-day mortality, we investigated the risk factors associated with AKI and mortality in patients with CRABC bacteremia who received or never received colistin. Patients with CRABC bacteremia aged ≥18 years were retrospectively identified for 3 years at five tertiary teaching hospitals. AKI was defined by using the Kidney Disease Improving Global Outcomes criteria. AKI developed in 103 (34.9%) of the 295 patients enrolled patients. AKI developed more frequently in patients who received colistin than in patients who did not (46.7% vs. 29.5%, p = 0.004). Multivariate analysis showed that intravenous colistin usage was an independent risk factor for AKI in these patients. Nonfatal disease, catheter-related bloodstream infection, and administration of colistin were protective factors for 28-day mortality. However, the sequential organ failure assessment score and AKI were associated with poor outcomes. In conclusion, colistin may be a double-edged sword; although it causes AKI, it also reduces 28-day mortality in patients with CRABC bacteremia. Therefore, colistin administration as an appropriate antibiotic may improve CRABC bacteremia prognosis, despite its nephrotoxicity.

Poultry chicken gut-bacteria carry high extent of colistin resistant mcr-1 gene in Bangladesh

Background: The indiscriminate uses of antimicrobials in either human or animal husbandry generate selection pressure to develop resistance in diverse microbial populations. Colistin is a polymyxin group antibiotic used for the treatment of critical human infections by multidrug-resistant (MDR) Gram-negative bacteria (GNB) and veterinary healthcare. In recent years, colistin usage has been expanded considerably in Argo, fishery, and food animal farming in Bangladesh. This study investigated phenotypic colistin-resistance and the prevalence of colistin-resistance mcr-1 gene in bacterial isolates from droppings of poultry chickens and household native chickens. Methods and materials: A cross-sectional study was conducted and colistin usage history to chickens was collected by a structured questionnaire. Bacteria were isolated from chicken droppings by inoculating on different selective culture media. The purified bacterial colonies were identified by conventional biochemical procedures followed by a rapid biochemical-test kit (API 20E, BioMérieux, Durham, NC). A part of bacterial identification was validated further by genotyping using 16S rDNA analyses. The colistin susceptibility of the isolates were determined by disk-diffusion and minimal inhibitory concentration (MIC) measurement. mcr-1 gene was detected by polymerase chain reactions (PCR) and confirmed by sequence blasting. Results: Overall 39.6% (59/159) isolates showed colistin-resistant by disk-diffusion assessment. The resistance prevalence was significantly higher in poultry-chicken isolates (48.5%, 48/99) than in native-chicken isolates (22%, 11/50; p = 002). All the resistant isolates showed MIC level, between >8 μg/mL to >256 μg/mL. Likely, the mcr-1 gene was detected more in poultry gut bacteria (34%) than in native-chicken isolates (14%, p = 0.02). mcr-1 appeared significantly associated with phenotypic colistin-resistance phenomena (p < 0.001). Previous colistin usage yielded a substantially higher proportion of mcr-1 in bacteria (p = 0.06). Conclusion: mcr-1 gene circulates in bacteria isolated from both poultry chicken and native chicken. Higher acquisition of mcr-1 in bacteria was associated with colistin-usage for chickens. The increased mcr-1 prevalence may increase the risk of critical human disease transmission. Specifically, mcr-1 can enter humans via zoonotic infections from poultry-human interface, which poses a big threat to public health.

Understanding of Colistin Usage in Food Animals and Available Detection Techniques: A Review.

Simple SummaryColistin is a last resort drug for the treatment of infection caused by multidrug-resistant Gram-negative bacteria. Different studies have uncovered the negative impact of colistin consumption in animals. Therefore, it has become essential to monitor the dosing regimens of colistin and assess their negative effects. The current review intends to provide brief information of colistin usage and its associated negative impact and discuss available techniques to detect colistin in animal-based food so that effective preventive measures can be taken to minimize the health risks in both animals and humans.Progress in the medical profession is determined by the achievements and effectiveness of new antibiotics in the treatment of microbial infections. However, the development of multiple-drug resistance in numerous bacteria, especially Gram-negative bacteria, has limited the treatment options. Due to this resistance, the resurgence of cyclic polypeptide drugs like colistin remains the only option. The drug, colistin, is a well-known growth inhibitor of Gram-negative bacteria like Acinetobacter baumanni, Enterobacter cloacae, Klebsiella pneumoniae, and Pseudomonas aeruginosa. Technological advancements have uncovered the role of the mcr-1(mobilized colistin resistance) gene, which is responsible for the development of resistance in Gram-negative bacteria, which make them distinct from other bacteria without this gene. Additionally, food animals have been determined to be the reservoir for colistin resistance microbes, from which they spread to other hosts. Due to the adverse effects of colistin, many developed countries have prohibited its usage in animal foods, but developing countries are still using colistin in animal food production, thereby imposing a major risk to the public health. Therefore, there is a need for implementation of sustainable measures in livestock farms to prevent microbial infection. This review highlights the negative effects (increased resistance) of colistin consumption and emphasizes the different approaches used for detecting colistin in animal-based foods as well as the challenges associated with its detection.

High abundance of the colistin resistance gene mcr-1 in chicken gut-bacteria in Bangladesh

Colistin is considered a last-resort reserved drug for the treatment of critical human infections by Gram-negative bacteria. Phenotypic colistin-resistance is strongly associated with plasmid-mediated mobile colistin resistance (mcr) genes. The mcr-bearing Enterobacteriaceae have been detected in many countries from environments, animals, and humans. This study investigated phenotypic colistin-resistance and the distribution of mcr-1, mcr-2, mcr-3, mcr-4, and mcr-5 genes in chicken-gut bacteria in Bangladesh. Bacteria were isolated from poultry- and native-chicken droppings, and their susceptibilities to colistin were determined by agar dilution and E-test minimal inhibitory concentration (MIC) measurements. Multiplex polymerase chain reactions detected mcr-1 to mcr-5 genes. Overall, 61.7% (92/149) of the isolates showed colistin resistance by agar dilution assessment (MIC > 2.0 μg/mL). The phenotypic resistance was observed considerably higher in poultry-chicken isolates (64.6%, 64/99) than in native-chicken isolates (56%, 28/50; p = 0.373). All the resistant isolates showed MIC levels between > 2 and > 128 μg/mL. The mcr-genes (mcr-1and mcr-2 combined) were detected more in poultry gut bacteria (36.4%) than native-chicken isolates (20%, p = 0.06). Despite bacteria sources, mcr-genes appeared to be significantly associated with phenotypic colistin-resistance phenomena (p < 0.001). Prior colistin usage led to a substantial increase in the proportion of bacteria with mcr-genes and phenotypic resistance (p < 0.001).

Analysis of mgrB gene mutations in colistin-resistant Klebsiella pneumoniae in Tehran, Iran

BackgroundThe emergence of multiple drug resistance (MDR) Klebsiella pneumoniae (KP) is a public health concern. Colistin is used as a last-resort treatment option for MDR-KP. The emergence of colistin-resistant isolates is a major public health challenge. The aim of this study was to explore genes and the responsible mechanisms of colistin resistance in MDR-KP isolates in Tehran, Iran. Methods94 KP isolates suspected to be colistin-resistant (by disc diffusion) from urine, sputum, blood collected between 2018 and 2019 were studied. Isolates were tested for antibiotic resistance determinants and their colistin minimum inhibitory concentration (MIC). The presence of β-lactamase and quinolone genes, plasmid-encoded resistance genes, mcr-1 and mcr-2 genes, and nucleotide sequences of mgrB were determined by polymerase chain reaction (PCR). Results20 of 94 isolates were colistin resistance KP (Col-R KP) (21%) with MIC ranged from 4 to 128 μg/ml. Coproduction of β-lactamases, and quinolones was in 18 (90%) Col R KP isolates. Four (20%) isolates had mutations in mgrB. mgrB was inactivated by nonsense mutations at codons 21 and insertion of IS 903B elements (IS5); and elongation of mgrB. 16 (80%) ColR KP isolates harbored wild type of mgrB. There is not any mcr-1, mcr-2 encoding genes on plasmids among all the isolates. ConclusionWe detected a high frequency of both qnr and ESBL resistance genes among colistin-resistant K. pneumoniae. Also, colistin resistance mainly occur with lipopolysaccharide (LPS) modification by different mechanisms. Spread of resistance against colistin resulting in treatment failure the colistin-included therapy regimen which is used as a last line of defense against infection due to MDR Gram-negative pathogens. The control of usage of colistin in hospital is necessary to prevent the spread of resistance among isolates.

Extensively drug-resistant Acinetobacter baumannii carrying blaOXA-23-like and armA in a hospital after an intervention in the intensive care unit which ended a long-standing endemicity

The aim of the study was to evaluate for a long time the effectiveness of an intervention designed to reduce carbapenem-resistant Acinetobacter baumannii (CRAB) and its impact on colistin usage in the ICU of a tertiary hospital in Spain. The rate of carbapenem resistance declined drastically during the period of study (2015 to 2018), from 93.57 to 74.65%, especially in the ICU. A significant decrease in colistin usage, from 1.16 to 0.39 DOTs, was observed. Forty-nine CRAB isolates recovered nearly 1year after starting the intervention were characterized. Most of them were recovered from patients admitted in wards other than ICU and were extensively drug-resistant, carried blaOXA-23-like and armA, and belonged to ST218. Implementation of control measures is crucial to CRAB control in ICUs but must be extended to all wards in order to eradicate CRAB from hospitals.

Colistin-resistance gene mcr in clinical carbapenem-resistant Enterobacteriaceae strains in China, 2014–2019

ABSTRACT To investigate whether introduction of colistin into the clinical settings selected colistin-resistant CRE, we performed molecular epidemiological study of 1868 CRE strains collected from different geographical locales in China during the period 2014–2019. 1755 (96.18%) isolates carried the carbapenemase genes bla KPC and bla NDM; 14 Escherichia coli isolates (0.75%) carrying mcr-1 and bla NDM (MCR-CREC) were also identified. Importantly, the number and relative prevalence of MCR-CREC isolates increased from 5 (0.41%) to 9 (1.38%) after introduction of polymyxin into clinical practice. Consistently, results of genetic analysis indicated that MCR-CREC strains collected before December 2017 were genetically diverse, yet those collected after that date exhibited more closely related genetic profiles, indicating that specific MCR-CREC strains were rapidly selected as a result of increased usage of colistin in clinical settings. The resistance level of MCR-CREC isolates to colistin increased after the introduction of polymyxin into clinical use with the MIC to colistin from <2 mg/L in 80% strains to 2 mg/L in 100% strains. Further dissemination of MCR-CREC strains, which exhibit resistance to the last-line drugs of carbapenems and colistin, is expected to pose a severe threat to human health.

Optimization of the MALDIxin test for the rapid identification of colistin resistance in Klebsiella pneumoniae using MALDI-TOF MS.

BackgroundWith the dissemination of carbapenemase producers, a revival of colistin was observed for the treatment of infections caused by MDR Gram-negatives. Unfortunately, the increasing usage of colistin led to the emergence of resistance. In Klebsiella pneumoniae, colistin resistance arises through addition of 4-amino-l-arabinose (l-Ara4N) or phosphoethanolamine (pEtN) to the native lipid A. The underlying mechanisms involve numerous chromosome-encoded genes or the plasmid-encoded pEtN transferase MCR. Currently, detection of colistin resistance is time-consuming since it still relies on MIC determination by broth microdilution. Recently, a rapid diagnostic test based on MALDI-TOF MS detection of modified lipid A was developed (the MALDIxin test) and tested on Escherichia coli and Acinetobacter baumannii.ObjectivesOptimize the MALDIxin test for the rapid detection of colistin resistance in K. pneumoniae.MethodsThis optimization consists of an additional mild-acid hydrolysis of 15 min in 1% acetic acid. The optimized method was tested on a collection of 81 clinical K. pneumoniae isolates, including 49 colistin-resistant isolates (45 with chromosome-encoded resistance, 3 with MCR-related resistance and 1 with both mechanisms).ResultsThe optimized method allowed the rapid (<30 min) identification of l-Ara4N- and pEtN-modified lipid A of K. pneumoniae, which are known to be the real triggers of polymyxin resistance. At the same time, it discriminates between chromosome-encoded and MCR-related polymyxin resistance.ConclusionsThe MALDIxin test has the potential to become an accurate tool for the rapid determination of colistin resistance in clinically relevant Gram-negative bacteria.

Leading an Antibiotic Stewardship Initiative Through a Quality Improvement Collaborative Among 22 Hospitals in a Lower Middle Income Country

BACKGROUND The emergence of colistin resistant Carbapenem Resistant Enterobacteriaceae (CRE's) within a period of 4 months caused a team of professionals to raise the alarm. In a country lacking standardized microbiological testing, no restriction on antibiotics usage and having basic infection prevention programs, there was a need to address antimicrobial stewardship (AMS) nationally. The success of one tertiary hospital in building an AMS program resulted in a national initiative for 22 hospitals. METHODS The AMS program design included a driver diagram for the hospitals covering a catchment area of approximately 80% of the total population. A multidisciplinary team of 5 members from each hospital was responsible for implementing the activities which included; standardization of microbiological testing through hands-on workshops utilizing the American Society for Microbiology and the Clinical and Laboratory Standard Institute (CLSI) guidelines. Developing evidence based national guidelines for infections and empiric treatment and building the capacity of clinical pharmacists, medical doctors, infection control coordinators through shadowing of the AMS core team at the tertiary hospital. A data collection sheet was developed using Microsoft Access to collect data about antibiotics Days of Therapy (DoT) in line with CDC guidelines to evaluate improvements. RESULTS The effect of the AMS program was noted by a statistically significant drop in the restricted antibiotics DoT ranging between 23-74% in the vancomycin, colistin and carbapenems usage (p CONCLUSIONS The achievements of AMS interventions with minimal resources can be used as a model for regional countries in the fight against the spread of resistant bacteria.

Second-Generation Tryptamine Derivatives Potently Sensitize Colistin Resistant Bacteria to Colistin.

Antibiotic resistance has significantly increased since the beginning of the 21st century. Currently, the polymyxin colistin is typically viewed as the antibiotic of last resort for the treatment of multidrug resistant Gram-negative bacterial infections. However, increased colistin usage has resulted in colistin-resistant bacterial isolates becoming more common. The recent dissemination of plasmid-borne colistin resistance genes (mcr 1-8) into the human pathogen pool is further threatening to render colistin therapy ineffective. New methods to combat antibiotic resistant pathogens are needed. Herein, the utilization of a colistin-adjuvant combination that is effective against colistin-resistant bacteria is described. At 5 μM, the lead adjuvant, which is nontoxic to the bacteria alone, increases colistin efficacy 32-fold against bacteria containing the mcr-1 gene and effects a 1024-fold increase in colistin efficacy against bacteria harboring chromosomally encoded colistin resistance determinants; these combinations lower the colistin minimum inhibitory concentration (MIC) to or below clinical breakpoint levels (≤2 μg/mL).

Can Nebulised Colistin Therapy Improve Outcomes in Critically Ill Children with Multi-Drug Resistant Gram-Negative Bacterial Pneumonia?

In the past decade, multidrug-resistant (MDR) gram-negative bacteria have become a major problem, especially for patients in intensive care units. Recently, colistin became the last resort therapy for MDR gram-negative bacteria infections. However, nebulised colistin use was limited to adult patients. Thus, we investigated the efficacy and safety of nebulised colistin treatment against MDR microorganisms in the paediatric intensive care unit (PICU). Data of all patients admitted for various critical illnesses (January 2016 to January 2019) were reviewed. Differences between groups (with and without a history of nebulised colistin) were compared. Of 330 patients, 23 (6.97%) used nebulised colistin. Significant relationships were found between nebulised colistin usage and several prognostic factors (inotropic drug use (p = 0.009), non-invasive mechanical ventilation (p ≤ 0.001), duration in PICU (p ≤ 0.001), and C-reactive protein level (p = 0.003)). The most common microorganism in tracheal aspirate and sputum cultures was Pseudomonas aeruginosa (13 patients). The most common underlying diagnosis was cystic fibrosis, noted in 6 patients. No serious nephrotoxicity and neurotoxicity occurred. This study showed that colistin can be safely used directly in the airway of critically ill children. However, nebulised colistin use did not have a positive effect on mortality and prognosis.

Risk factors for rectal colonization of carbapenem-resistant Enterobacteriaceae in a tertiary care hospital: a case-control study from Turkey

Background/aim This study aimed to evaluate the risk factors of patients colonized with carbapenem-resistant Enterobacteriaceae (CRE).Materials and methods The study was conducted between January 2010 and March 2016. The colonized group consisted of patients who had a CRE strain in their rectal swab cultures, whereas patients with negative rectal surveillance cultures for CRE who were concurrently hospitalized in the same units with the colonized group patients were included in the control group.Results The number of patients in the colonized and the control group was 71 and 120, respectively. Both groups were evaluated for demographic and healthcare-associated characteristics. Isolated microorganisms in rectal surveillance cultures for CRE were Klebsiella pneumoniae (75.5%), Escherichia coli (15.5%), Enterobacter cloacae (4.2%), Klebsiella oxytoca (1.4%), and Klebsiella terrigena (1.4%). The isolates were resistant to imipenem, meropenem, and ertapenem (52.1%, 73.2%, and 100%, respectively). In multivariate analysis, presence of decubitus, colistin usage, glycopeptide usage, and fluoroquinolone usage were found to be independent risk factors for CRE colonization. There was no significant difference between the two groups with regards to mortality (P = 0.070).Conclusion These results are in agreement with the current literature. The findings of this study could be useful for improvement of infection control strategies related to CRE.

Clinical and laboratory-induced colistin-resistance mechanisms in Acinetobacter baumannii.

The increasing incidence and emergence of multi-drug resistant (MDR) Acinetobacter baumannii has become a major global health concern. Colistin is a historic antimicrobial that has become commonly used as a treatment for MDR A. baumannii infections. The increase in colistin usage has been mirrored by an increase in colistin resistance. We aimed to identify the mechanisms associated with colistin resistance in A. baumannii using multiple high-throughput-sequencing technologies, including transposon-directed insertion site sequencing (TraDIS), RNA sequencing (RNAseq) and whole-genome sequencing (WGS) to investigate the genotypic changes of colistin resistance in A. baumannii. Using TraDIS, we found that genes involved in drug efflux (adeIJK), and phospholipid (mlaC, mlaF and mlaD) and lipooligosaccharide synthesis (lpxC and lpsO) were required for survival in sub-inhibitory concentrations of colistin. Transcriptomic (RNAseq) analysis revealed that expression of genes encoding efflux proteins (adeI, adeC, emrB, mexB and macAB) was enhanced in in vitro generated colistin-resistant strains. WGS of these organisms identified disruptions in genes involved in lipid A (lpxC) and phospholipid synthesis (mlaA), and in the baeS/R two-component system (TCS). We additionally found that mutations in the pmrB TCS genes were the primary colistin-resistance-associated mechanisms in three Vietnamese clinical colistin-resistant A. baumannii strains. Our results outline the entire range of mechanisms employed in A. baumannii for resistance against colistin, including drug extrusion and the loss of lipid A moieties by gene disruption or modification.