Multidrug-resistant Bacilli Research Articles

The impacts of ginger and olive oils on competing multidrug resistant Bacillus cereus in beef mince, luncheon, sausage, and pasterma

The impacts of ginger and olive oils on competing multidrug resistant Bacillus cereus in beef mince, luncheon, sausage, and pasterma

Screening the efficacy of platinum-based nanomaterial synthesized from Allium sativum to control plant pathogens

Emerging challenge posed by multidrug-resistant Bacillus spp. phytopathogens on agriculture and their commodities exerts pressure on global food security. This mandates the search for other alternatives to existing antibiotics. This study reports a novel method of green synthesis of platinum nanoparticles (PtHGNM) using aqueous extract of Himalayan garlic (Allium sativum). Physicochemical characterization techniques including UV-visible spectrometry, FT-IR, XRD, DLS, zeta potential, and FESEM-EDAX disclosed the biogenic fabrication of a stable and amorphic nano platinum material. This nanoparticle exhibited high bactericidal efficacy and effectively inhibited biofilm formation by the model plant-borne pathogens used in this study. We estimated the membrane integrity, oxidative enzymes and stress parameters of bacteria to elucidate the underlying mechanism of action of PtHGNM. This research uncovered the potential of biogenic nanoparticles for sustainable plant disease management and paved the way for further analysis of its properties and mechanism of its action.

Influence of essential oil galangal and yellow mustard on multidrug resistant Bacillus cereus in chicken meat products

Influence of essential oil galangal and yellow mustard on multidrug resistant Bacillus cereus in chicken meat products

Multi-Drug Resistant Bacillus cereus: A Growing Concern for Powdered Infant Formula and Baby Foods (Cereals) in Bangladesh

Multi-Drug Resistant Bacillus cereus: A Growing Concern for Powdered Infant Formula and Baby Foods (Cereals) in Bangladesh

Applications of bacteriophage in combination with nisin for controlling multidrug-resistant Bacillus cereus in broth and various food matrices

This study focused on the isolation and characterization of bacteriophages with specific activity against toxin-producing and multidrug-resistant strains of Bacillus cereus sensu stricto (B. cereus s. s.). Ten different samples yielded six bacteriophages by utilizing the double-layer agar technique. The most promising phage, vB_BceS-M2, was selected based on its broad host range and robust lytic activity against various B. cereus s. s. strains. The phage vB_BceS-M2 had a circular double-stranded DNA genome of 56,482 bp. This phage exhibited stability over a wide range of temperatures and pH values, which is crucial for its potential application in food matrices. The combined effect of phage vB_BceS-M2 and nisin, a widely used antimicrobial peptide, was investigated to enhance antimicrobial efficacy against B. cereus in food. The results suggested that nisin showed synergy and combined effect with the phage, potentially overcoming the growth of phage-resistant bacteria in the broth. Furthermore, practical applications were conducted in various liquid and solid food matrices, including whole and skimmed milk, boiled rice, cheese, and frozen meatballs, both at 4 and 25 °C. Phage vB_BceS-M2, either alone or in combination with nisin, reduced the growth rate of B. cereus in foods other than whole milk. The combination of bacteriophage and nisin showed promise for the development of effective antimicrobial interventions to counteract toxigenic and antibiotic-resistant B. cereus in food.

STUDY OF MULTIDRUG-RESISTANT GRAM-NEGATIVE BACILLI IN URINARY TRACT INFECTIONS AND THEIR ANTIBIOGRAM AT A TERTIARY CARE HOSPITAL

Objective: To study the frequency of multidrug-resistant Gram-negative bacilli in urinary tract infections and antibiotic susceptibility pattern of multidrug-resistant Gram-negative bacilli in urinary tract infections.
 Methods: This study was conducted on urine samples received at the Department of Microbiology, Andhra Medical College, for a period of six months from August 2022 to January 2023. During the study period, a total of 3361 urine samples were processed and conventional microbiological techniques were used to isolate uropathogens. Antibiotic susceptibility was tested by the Kirby-Bauer Disc diffusion method and interpreted according to Central Laboratory Standard Institute (CLSI) guidelines 2022. Multidrug-resistant bacilli in this study were defined as Gram-negative bacilli that were resistant to at least one agent in three or more antibiotic classes.
 Results: Out of 3361 urine samples received from outpatient and inpatient departments of our hospital, 858 samples were culture positive-839 were Gram-negative isolates and 19 were Gram-positive isolates. Mean age was 40-60 y. Urinary tract infections were more common in females than males. Among Gram-negative bacilli isolated, Escherichia coli was the most common organism isolated-435(50.69%), followed by Klebsiella species-232(27.03%), Acinetobacter species-105(12.25%), Pseudomonas species-55(6.41%), Proteus species-10(1.16%), Citrobacter species-2(0.23%). Among Gram-positive cocci, Staphylococci-17(1.98%) and Enterococci-2(0.23%) were isolated. Out of 858 isolates, 177 (20.62%) were identified as multidrug-resistant bacilli and all were resistant to the drug groups Cephalosporins, Carbapenems and Quinolones. Most of the Multidrug-resistant gram-negative bacilli were sensitive to Fosfomycin and Nitrofurantoin.
 Conclusion: Multidrug-resistant Gram-negative bacilli in urinary tract infections have become a major health problem. Assessment of Risk factors, Surveillance of Resistance patterns and policies for proper use of antibiotics are urgently needed.

Emergence of multidrug-resistant Bacillus spp. derived from animal feed, food and human diarrhea in South-Eastern Bangladesh

BackgroundAntimicrobial resistance poses a huge risk to human health worldwide, while Bangladesh is confronting the most severe challenge between the food supply and the huge consumption of antibiotics annually. More importantly, probiotics containing Bacillus spp. are claimed to be an alternative to antimicrobial stewardship programs. However, their antibiotic resistance remains elusive. Thus, we employed the antimicrobial susceptibility test and PCR to assess the prevalence of resistance, including multidrug resistance (MDR) and resito-genotyping of isolated Bacillus spp.ResultsThe phenotypic profile showed that Bacillus spp. were 100% sensitive to gentamicin (2 µg/mL), whereas lowered sensitivity to levofloxacin (67.8%, 0.5–1 µg/mL), ciprofloxacin (62.3%, 0.5–1 µg/mL), clindamycin (52.2%, 0.25–0.5 µg/mL), amoxicillin-clavulanic acid (37.6%, 0.06 µg/mL), azithromycin (33.4%, 1–2 µg/mL), tetracycline (25.6%, 2–4 µg/mL), nitrofurantoin (21.1%, 16–32 µg/mL), co-trimoxazole (19.2%, 2 µg/mL), and erythromycin (18.8%, 0.25–0.5 µg/mL). The strains were completely resistant to penicillin, amoxicillin-clavulanic acid, cefixime, ceftriaxone, vancomycin, and co-trimoxazole, and a species-specific trend was seen in both phenotypic and genotypic resistance patterns. Genotypic resistance indicated prevalence of the bla1 (71.5%), tetA (33%), erm1 (27%), blaTEM (13.1%), blaCTX-M-1/blaCTX-M-2 /sul1 (10.1%), blaSHV (9.6%), and qnrS (4.1%) genes. The β-lactamase resistance gene bla1 was found in all penicillin-resistant (MIC ≥ 32 µg/mL) Bacillus spp. One hundred ninety-one isolates (89.6%) were MDR, with 100% from diarrhea, 90.3% from food, and 88.7% from animal feed.ConclusionBased on the MIC value and profile analysis of antibiotic resistance genes, this is the first study that Bacillus spp. antimicrobial susceptibilities have been identified in Bangladesh, and our study will shed light on the adverse effects of feed-borne Bacillus spp. emerging from animal feed to the food chain. A comprehensive investigation is urgently needed by policymakers on tolerance limits and harmful effects in the animal industry.

Meat and meat products as potential sources of emerging MDR Bacillus cereus: groEL gene sequencing, toxigenic and antimicrobial resistance

BackgroundBacillus cereus is implicated in severe foodborne infection in humans. This study intended to assess the occurrence, groEL gene sequencing, biofilm production, and resistance profiles of emerged multidrug resistant (MDR) B. cereus in meat and meat product samples. Moreover, this work highlights the virulence and toxigenic genes (hblABCD complex, nheABC complex, cytK, ces, and pc-plc) and antimicrobial resistance genes (bla1, tetA, bla2, tetB, and ermA).MethodsConsequently, 200 samples (sausage, minced meat, luncheon, beef meat, and liver; n = 40 for each) were indiscriminately collected from commercial supermarkets in Port Said Province, Egypt, from March to May 2021. Subsequently, food samples were bacteriologically examined. The obtained isolates were tested for groEL gene sequence analysis, antibiotic susceptibility, biofilm production, and PCR screening of toxigenic and resistance genes.ResultsThe overall prevalence of B. cereus among the inspected food samples was 21%, where the highest predominance was detected in minced meat (42.5%), followed by beef meat (30%). The phylogenetic analysis of the groEL gene exposed that the examined B. cereus strain disclosed a notable genetic identity with other strains from the USA and China. Moreover, the obtained B. cereus strains revealed β-hemolytic activity, and 88.1% of the recovered strains tested positive for biofilm production. PCR evidenced that the obtained B. cereus strains usually inherited the nhe complex genes (nheA and nheC: 100%, and nheB: 83.3%), followed by cytK (76.2%), hbl complex (hblC and hblD: 59.5%, hblB: 16.6%, and hblA: 11.9%), ces (54.7%), and pc-plc (30.9%) virulence genes. Likewise, 42.9% of the examined B. cereus strains were MDR to six antimicrobial classes and encoded bla1, bla2, ermA, and tetA genes.ConclusionIn summary, this study highlights the presence of MDR B. cereus in meat and meat products, posing a significant public health risk. The contamination by B. cereus is common in minced meat and beef meat. The molecular assay is a reliable fundamental tool for screening emerging MDR B. cereus strains in meat and meat products.

Multidrug-resistant Bacillus species isolated from hospital soil environment is controlled by nanobiotics incorporated nanoformulation

Multidrug resistance is a serious hazard to the environment, it claims a large number of lives every year. Lack of drug options and easy transmission of these organisms remain the biggest threat in treating the relative infections whose causative systems have evolved and become stronger in due course of time. Hospitals serve as one of the largest breeding grounds for harbouring these organisms. This study aims to isolate and characterize multidrug-resistant microorganisms from soil samples collected from hospital waste dumping premises. Polyherbal nanoformulation was synthesized from ethno-medicinal source Triphala (three berries) and characterized using various physico-chemical characterization techniques. The antibacterial efficacy of the polyherbal nanoformulation was evaluated by employing various assays to determine MIC, MBC, and biofilm inhibition potential in isolated strains. Bacterial colonies were isolated and the DNA was sequenced. The isolated organisms were identified as Bacillus cereus, Bacillus licheniformis, and Bacillus pumilus and they were subjected to antibiotic susceptibility by using various antibiotics. It was found that all the microorganisms were multidrug-resistant and possessed resistance to various classes of antibiotics. The various antibacterial assays showed that the polyherbal nanoformulation was highly effective in controlling growth and biofilm formation even at lower concentrations when compared with commercial antibiotics. The novelty of this research work lies in combining the beneficial effects of silver and polyherbal drugs into a single Polyherbal nanoformulation. This is the first novel report to utilize polyherbal nanoformulation to control the multidrug-resistant microorganisms thriving in hospital waste dumping sites. Hence, this nanobiotics incorporated polyherbal nanoformulation can be developed into a commercial product to treat the hospital waste material before dumping it into the environment.

Apple cider vinegar exhibits promising antibiofilm activity against multidrug-resistant Bacillus cereus isolated from meat and their products.

Bacillus cereus (B. cereus) biofilm is grown not only on medical devices but also on different substrata and is considered a potential hazard in the food industry. Quorum sensing plays a serious role in the synthesis of biofilm with its surrounding extracellular matrix enabling irreversible connection of the bacteria. The goal of the current investigation was to ascertain the prevalence, patterns of antimicrobial resistance, and capacity for B. cereus biofilm formation in meat and meat products in Egypt. In all, 150 meat and meat product samples were used in this study. For additional bacteriological analysis, the samples were moved to the Bacteriology Laboratory. Thereafter, the antimicrobial, antiquorum sensing, and antibiofilm potential of apple cider vinegar (ACV) on B. cereus were evaluated. Out of 150 samples, 34 (22.67%) tested positive for B. cereus. According to tests for antimicrobial susceptibility, every B. cereus isolates tested positive for colistin and ampicillin but negative for ciprofloxacin and imipenem. The ability to form biofilms was present in all 12 multidrug-resistant B. cereus isolates (n = 12); of these, 6 (50%), 3 (25%), and 3 (25%) isolates were weak, moderate, and strong biofilm producers, respectively. It is noteworthy that the ACV demonstrated significant inhibitory effects on B. cereus isolates, with minimum inhibitory concentrations varying between 2 and 8 μg/ml. Furthermore, after exposing biofilm-producing B. cereus isolates to the minimum biofilm inhibitory concentrations 50 of 4 μg/ml, it demonstrated good antibiofilm activity (>50% reduction of biofilm formation). Strong biofilm producers had down-regulated biofilm genes (tasA and sipW) and their regulator (plcR) compared to the control group, according to reverse transcriptase quantitative polymerase chain reaction analysis. Our study is the first report, that spotlights the ACV activity against B. cereus biofilm and its consequence as a strong antibacterial and antibiofilm agent in the food industry and human health risk.

Expression profiles of sporulation genes in multidrug-resistant Bacillus species isolated from intensive care units of Ghanaian hospital.

Sporulating bacteria such as Bacillus spp. have contributed to severity of opportunistic hospital acquired infections, including postoperative wounds and respiratory tract infections. This study determines the expression profiles of sporulation markers in multidrug-resistant Bacillus spp. isolated from Ghanaian hospital environments. Antimicrobial resistance (AMR) profiles of the bacteria were determined with disk diffusion and broth microdilution. Primer-specific polymerase chain reaction (PCR) amplification was used to profile the sporulation markers, and quantitative reverse transcription polymerase chain reaction (RT-qPCR) was used for the expression of the sporulation markers at different antibiotic concentrations. The strains are multidrug resistant (70-100%) to at least two of the eight classes of the antibiotics tested including cephalosporins, penicillin, aminoglycosides, and glycopeptide. The strains showed different resistance patterns to all the tested antibiotics, which might indicate diverse resistance mechanisms. Common (spoVK spoVE, spoJ, and sigF) and not commonly (sigJ, soJ, yrbC, and yjcE) reported sporulation markers were detected in the strains. The study showed an association of the sporulation markers with AMR as indicated by their expression profiles.

New treatments for multidrug-resistant non-fermenting Gram-negative bacilli Infections.

Ceftolozane/tazobactam, ceftazidime/avibactam and cefiderocol belong to a novel generation of antibiotics that correspond with the β-lactam family. It is necessary to having new options in treating infections caused by Gram-negative, non-fermenting multidrug-resistant bacilli due to the significant increase in multidrug resistance in the last decades. Knowing the main characteristics of each drug is key for correct use.

Mechanism and management of antibiotic drug resistance tuberculosis

Drug resistance in tuberculosis has been shown to result from spontaneous mutation in several chromosomal genes of M.Tuberculosis. Mutation may reduce the medications' capacity to bind to the target genes. In many patients polydrug resistance, multidrug resistance, rifampicin resistance (RR) and extensive drug resistance (XDR) were seen. The diagnosis of drug-resistant TB in HIV-positive persons is more difficult and may be confused with other pulmonary or systemic infections. Management of patients with mono- or poly-resistant TB will be done with standard first line chemotherapy. Treatment of latent infection for people suffering from multidrug resistant bacilli is problematic because the only cure by isoniazid and rifampicin. In the recent cases of severe hepatotoxicity associated with preventive treatment comprising either pyrazinamide and rifampicin or pyrazinamide and fluoroquinolone. The use of dilatory fluoroquinolones, such as moxifloxacin, remarkable improved treatment outcomes of XDR-TB.

Genetic and genomic characterization of multidrug resistant Bacillus subtilis M3 isolated from an activated sludge reactor treating wastewater

Genetic and genomic characterization of multidrug resistant Bacillus subtilis M3 isolated from an activated sludge reactor treating wastewater

Genomic characterisation of multidrug-resistant Bacillus toyonensis strain 4HC1 isolated from marine plastic in Norway

Bacillus toyonensis is widespread in nature. Multidrug-resistant B. toyonensis strain 4HC1 was isolated from polyethylene submerged in the water column near a beach in Øygarden, Norway. We analysed the whole genome sequence of strain 4HC1 in order to understand the genetic basis of the observed phenotypic antibiotic resistance. Whole-genome sequencing of B. toyonensis strain 4HC1 was performed on Illumina MiSeq platform using 2×300 bp chemistry. The genome sequence was assembled using SPAdes v.3.13.0 and was annotated using the NCBI Prokaryotic Genome Annotation Pipeline (PGAP). The draft genome of strain 4HC1 is 6 156 259 bp (133 contigs) in size with a GC content of 34.95%. The genome comprises 6089 protein-coding genes, 86 tRNAs and 24 rRNAs. Strain 4HC1 is resistant to cefotaxime, trimethoprim and ampicillin and carries various antibiotic resistance genes (ARGs), including several β-lactamases, aminoglycoside 6-adenylyltransferase, a TetM family tetracycline resistance gene, two different tetracycline efflux pumps, and a bleomycin resistance gene. Several virulence genes including genes involved in immune evasion, iron acquisition and toxins were also detected in strain 4HC1. The draft genome sequence of B. toyonensis strain 4HC1 released here shows the presence of various ARGs and virulence genes in a multidrug-resistant strain isolated from marine plastic.

UNPRECEDENTED ANTIMICROBIAL PROPERTIES OF PROSOPIS CINERARIA LEAVES

The antibacterial effect of Prosopis cineraria leaves was evaluated on multidrug resistant (MDR) strains of Bacillus subtilis (ATCC 6633), E. coli (ATCC 8739), Salmonella enterica (ATCC 14028), Staphylococcus aureus (ATCC 6538), Pseudomonas aeruginosa (ATCC 27853). Powdered leaves of the tree were treated with methanol for the extraction. Crude methanol extracts of the leaves of P. cineraria was investigated for their antibacterial activity against a wide range of bacteria (both gram-positive and gram-negative) by agar well diffusion method. Ciprofloxacin was used as standard. The methanolic leaves extracts of P. cineraria showed a remarkable inhibition of the microorganisms. The potency shown by these extracts recommends their use against multidrug resistant microorganisms. The present study suggests that the methanol extract of the leaves of P. cineraria exhibited a potential antibacterial activity against the tested microorganisms and could be a potential source of new antimicrobial agents.

Surgical Site Infections in General Surgery at the Regional Hospital of Thies (Senegal): Epidemiological, Bacteriological Aspects and Risk Factors

Introduction: Surgical Site Infections (SSIs) are frequent and lead to serious consequences and in terms of morbidity and mortality, with an increase in the length of hospitalization and health costs. Developing countries are the most affected. The aim of our study was to describe the epidemiological, clinical, and bacteriological aspects of SSIs in general surgery at the RH of Thies. Methods: This is a prospective study over a period of seven months (7 months) from September 1, 2018 to March 31, 2019 at the level of the general surgery department of the Regional Hospital of Thies. Bacteriological studies were carried out at the level of the Bacteriology unit of the National Public Health Laboratory of Senegal. Results: The incidence of SSIs in our study was 9.9%. The SSIs rate was 15.3% among resident surgeons, 10% among junior surgeons, 6.8% among senior ones. The surgical intervention was classified as Altemeier stage 1 in 3.4% of cases (n = 1), stage 2 in 27.6% of cases (n = 8), stage 3 in 24.1% of cases (n = 7) and stage 4 in 44.8% of cases (n = 13). Twenty-two of the isolated stems (73.3% of cases) were multidrug-resistant bacilli. The extended spectrum beta lactamase (ESBL) phenotype was found in 22 isolates and 1 stem of K. pneumoniae was resistant to all antibiotics. Conclusion: SSIs constitute a challenge because of their high frequency and the high resistance of germs to common antibiotics. Currently, the main mode of resistance of bacteria in SSIs is the secretion of ESBL. This phenomenon seems to be major in our regions where it is urgent to review the therapeutic protocols in practice in the services.

PCR in tuberculosis: An extremely useful tool?

Introduction: Tuberculosis is a global air borne infectious disease with significant increase in incidence and prevalence. Conventional methods take longer time for diagnosis and drug susceptibility with less sensitivity and specificity. So rapid diagnosis and detection of multi, extensive and total drug resistant bacilli are of up most importance for therapeutic purpose. Materials and Methods: It was a retrospective study in tertiary care. All clinical samples suspected for tuberculosis received by laboratory were included in the study. The samples were processed for microscopy by ZN stain, culture by LJ media and RT-PCR. Results: Total 566 sample were tested out of 177 (31%) were positive for tuberculosis. 62% samples were PCR positive, 51% were culture positive and 49% were smear positive. The most common sample received with maximum positivity rate was pleural fluid (34%). Male predominance was seen with young adults as the predominant group affected. Conclusion: The present study shows good specificity of PCR with sensitivity of 50%. It detects 50% times more cases in relation to conventional results where they fail to produce correct results. More such comparative studies are needed to establish importance of PCR in early diagnosis and treatment. Keywords: Mycobacteria, RT-PCR, Diagnosis, Detection, Infection.

Characteristics of Microbial Factors of Healthcare-Associated Infections Including Multidrug-Resistant Pathogens and Antibiotic Consumption at the University Intensive Care Unit in Poland in the Years 2011-2018.

Introduction: In recent years, an increase in healthcare-associated infections (HAIs) caused by resistant pathogens, which is a clinically troublesome trend, has been observed. The aim of the study was to analyze the microbial factors of HAIs and the drug resistance of microorganisms to selected antibiotics and their consumption. Material and Methods: The retrospective study included 3708 patients hospitalized in the intensive care unit (ICU) of the University Teaching Hospital in Wroclaw, who were diagnosed with 742 HAIs in the period from 1 January 2011 to 31 December 2018. The aim of the study was the analysis of microorganisms isolated in the respective clinical forms of HAIs, including the occurrence of “alert pathogens”, presence of multidrug-resistant (MDR) strains, and consumption of selected antibiotics. Findings: During the study period, 846 microorganisms were cultured in patients with HAIs, and among them, Acinetobacter baumannii MDR represented 31.8%; Klebsiella pneumoniae ESBLs, 11.3%; Pseudomonas aeruginosa MDR, 4.1% and MRSA, 2.2%; and Enterococcus spp. vancomycin-resistant enterococci (VRE), 1.3%. Among all the pathogens, Gram-negative bacteria (GNB) were dominant (71.6%). Gram-positive bacteria and fungi accounted for 21.6% and 7%, respectively. The total number of strains responsible for ventilator-associated pneumonia (VAP), urinary tract infection (UTI), and central line-associated blood stream infection (CLA-BSI) was as follows: 458 (54.1%), 274 (32.4%), and 114 (13.5%), respectively. Among the etiological factors of VAP, there was a prevalence of A. baumannii MDR (41.9%), as well as in the case of UTI (21.9%). With regards to CLA-BSI, MRCNS (29.8%) was the dominant pathogen. The “alert pathogens” accounted for 54.7% of all the analyzed strains. The MDR strains represented 72.6% and 9.7% among A. baumannii and P. aeruginosa, respectively. In the years 2011 vs. 2018, an increase in infections with MDR bacilli was observed, 34.6% vs. 61.0% (p = 0.0008), respectively, including A. baumannii MDR 16.54% vs. 34.56 % (p = 0.0009) and Enterobacterales ESBL+/AMPC 11.8% vs. 15.44 % (p = 0.3921). Resistance to methicillin was confirmed in 35.2% of S. aureus strains. Resistance to vancomycin was found among 30.9% of Enterococcus spp. The observed period was marked by an increase in the consumption of carbapenems: 197.7 vs. 235.9 defined daily dose (DDD)/1000 patients-days. Conclusions: Gram-negative bacteria were found to be dominant pathogens in healthcare-associated infections. The most frequently cultured pathogens were multidrug-resistant A. baumannii, K. pneumoniae ESBL(+), and P. aeruginosa. The study showed an increase in the incidence of “alert pathogens” and MDR bacilli, as well as the tendency of a growing resistance to antibiotics during the observed period. Microbiological analysis of HAIs and the consumption of antibiotics is the necessary element of the proper antibiotic policy in hospitals.

High frequency of colonization by diverse clones of beta-lactam-resistant Gram-negative bacilli in haemodialysis: different sources of transmission outside the renal unit?

Introduction. While colonization by Staphylococcus aureus in haemodialysis patients has been assessed, knowledge about colonization by beta-lactam-resistant Gram-negative bacilli is still limited.Aim. To describe clinical and molecular characteristics in haemodialysis patients colonized by S. aureus (MSSA-MRSA) and beta-lactam-resistant Gram-negative bacilli in an ambulatory renal unit.Methodology. The study included patients with central venous catheters in an outpatient haemodialysis facility in Medellín, Colombia (October 2017-October 2018). Swab specimens were collected from the nostrils and skin around vascular access to assess colonization by S. aureus (MSSA-MRSA). Stool samples were collected from each patient to evaluate beta-lactam-resistant Gram-negative bacilli colonization. Molecular typing included PFGE, multilocus sequence typing (MLST), spa typing and enterobacterial repetitive intergenic consensus-PCR (ERIC). Clinical information was obtained from medical records and personal interview.Results. A total of 210 patients were included in the study. S. aureus colonization was observed in 33.8 % (n=71) of the patients, 4.8 % (n=10) of which were colonized by methicillin-resistant S. aureus. Stool samples were collected from 165 patients and of these 41.2 % (n=68) and 11.5 % (n=19) were colonized by extended-spectrum-beta-lactamase-producing (ESBL) and carbapenem-resistant bacilli, respectively. Typing methods revealed high genetic diversity among S. aureus and ESBL-producing Gram-negative bacilli (ESBL-GNB). Antibiotic use and hospitalization in the previous 6 months were observed in more than half of the studied population.Conclusion. The high colonization by ESBL-GNB in haemodialysis patients shows evidence for the need for stronger surveillance, not only for S. aureus but also for multidrug-resistant bacilli in order to avoid their spread. Additionally, the high genetic diversity suggests other sources of transmission outside the renal unit instead of horizontal transmission between patients.