Prevalence of silver resistance genes in bacteria isolated from human and horse wounds. - Related Documents




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577001.0000Prevalence of silver resistance genes in bacteria isolated from human and horse wounds. The aim of this study was to investigate the prevalence of silver resistance genes in 172 bacterial strains which had been isolated from both human and equine wounds. PCR screening for 8 currently named genes in 3 silver resistance transcriptional units, silE, silRS and silP, silCBA and silF was performed on total DNA extracted from all clinical isolates. Plasmids were isolated from sil-positive strains to determine if the genes were present on the chromosome. MICs and zone of inhibition assays were utilised to examine phenotypic resistance to silver nitrate and ionic silver. Evidence of silver resistance genes was demonstrated in six strains of Enterobacter cloacae, an organism rarely implicated as a primary pathogen in chronic wounds. MIC data showed that all strains were inhibited at silver nitrate concentrations > or =5mg/L. When tested against a silver-containing absorbent wound dressing all strains showed inhibition of growth after 24h. In MIC and zone of inhibition studies, inhibition was evident but reduced in strains which contained sil genes. Although sil genes were found in six of the wound isolates studied, the genes were consistently associated with a non-pathogenic bacterium. Furthermore, investigation of phenotypic resistance in sil-positive isolates showed that silver continued to be effective.200919362435
583610.9997Identification of Pseudomonas aeruginosa genes associated with antibiotic susceptibility. Pseudomonas aeruginosa causes acute and chronic infections in humans and these infections are difficult to treat due to the bacteria's high-level of intrinsic and acquired resistance to antibiotics. To address this problem, it is crucial to investigate the molecular mechanisms of antibiotic resistance in this organism. In this study, a P. aeruginosa transposon insertion library of 17000 clones was constructed and screened for altered susceptibility to seven antibiotics. Colonies grown on agar plates containing antibiotics at minimum inhibitory concentrations (MICs) and those unable to grow at 1/2 MIC were collected. The transposon-disrupted genes in 43 confirmed mutants that showed at least a three-fold increase or a two-fold decrease in susceptibility to at least one antibiotic were determined by semi-random PCR and subsequent sequencing analysis. In addition to nine genes known to be associated with antibiotic resistance, including mexI, mexB and mexR, 24 new antibiotic resistance-associated genes were identified, including a fimbrial biogenesis gene pilY1 whose disruption resulted in a 128-fold increase in the MIC of carbenicillin. Twelve of the 43 genes identified were of unknown function. These genes could serve as targets to control or reverse antibiotic resistance in this important human pathogen.201020953948
563920.9997Disinfectant and antibiotic resistance of lactic acid bacteria isolated from the food industry. Quaternary ammonium compounds (QACs) are widely used as disinfectant in medical and food environments. There is a growing concern about the increasing incidence of disinfectant-resistant microorganisms from food. Disinfectant-resistant lactic acid bacteria (LAB) may survive disinfection and cause spoilage problems. Moreover, resistant LAB may potentially act as a reservoir for resistance genes. A total number of 320 LAB from food industry and meat were screened for resistance to the QAC benzalkonium chloride (BC). Out of 320 strains, five strains (1.5%) were considered to be resistant and 56 (17.5%) were tolerant to BC. The resistant strains were isolated from food processing equipment after disinfection. The resistant, tolerant, and some sensitive control bacteria were examined for susceptibility to 18 different antibiotics, disinfectants, and dyes using disc agar diffusion test and microdilution method. Little systematic cross-resistance between BC and any of the antimicrobial agents tested were detected except for gentamycin and chlorhexidine. A BC-tolerant strain was much easier to adapt to higher levels of BC as compared to a BC-sensitive strain. No known gram-positive QAC resistance genes (qacA/B, qacC, qacG, and qacH) were detected in the BC-resistant strains. Identification to species level of the BC-resistant isolates was carried out by comparative analysis of 16S-rDNA sequencing. In conclusion, resistance to BC is not frequent in LAB isolated from food and food environments. Resistance may occur after exposure to BC. The BC resistant isolates showed no cross-resistance with other antimicrobial compounds, except for gentamycin and chlorhexidine. Nevertheless, BC-resistant LAB may be isolated after disinfection and may contribute to the dissemination of resistance.200111310806
551030.9997Investigating possible association between multidrug resistance and isolate origin with some virulence factors of Escherichia coli strains isolated from infant faeces and fresh green vegetables. AIMS: In this study, the association between multidrug resistance (MDR) and the expression of some virulence factors were evaluated in Escherichia coli strains isolated from infant faeces and fresh green vegetables. The effect of isolate origin on associated virulence factors was evaluated. In addition, genetic fingerprinting of a sample of these isolates (10 isolates from each group) was studied in order to detect any genetic relatedness among these isolates. METHODS AND RESULTS: Escherichia coli isolates were divided into four groups based on their origin (human faeces or plant) and their antibiotic resistance (multiresistance or susceptible). PCR was used to investigate heat-labile and heat-stable enterotoxin genes, and four siderophore genes (aerobactin, enterobactin, salmochelin and yersiniabactin). Genetic fingerprinting of the isolates was performed using enterobacterial repetitive intergenic consensus PCR. Siderophore production was measured by a colorimetric method. Biofilm formation was evaluated by a crystal violet assay. The results of the study showed that the expression of MDR is not significantly associated with an increase in these virulence factors or with biofilm formation. However, the origin of isolates had a significant association with siderophore gene availability and consequently on the concentrations of siderophores released. Genetic fingerprinting indicated that human and plant isolates have the same clonal origin, suggesting their circulation among humans and plants. CONCLUSION: Antibiotic-susceptible strains of E. coli may be as virulent as MDR strains. Results also suggest that the environment can play a potential role in selection of strains with specific virulence factors. SIGNIFICANCE AND IMPACT OF THE STUDY: Antibiotic-susceptible isolates of Escherichia coli from plant or human origin can be as virulent as the multidrug resistance (MDR) ones. Genetic relatedness was detected among the isolates of plant and human origin, indicating the circulation of these bacteria among human and plants. This could imply a potential role for environmental antimicrobial resistant bacteria in human infection.201931034123
473940.9997Indirect resistance to several classes of antibiotics in cocultures with resistant bacteria expressing antibiotic-modifying or -degrading enzymes. OBJECTIVES: Indirect resistance (IR), the ability of an antibiotic-resistant population of bacteria to protect a susceptible population, has been previously observed for β-lactamase-producing bacteria and associated with antimicrobial treatment failures. Here, we determined whether other resistance determinants could cause IR in the presence of five other classes of antibiotics. METHODS: A test was designed to detect IR and 14 antibiotic resistance genes were tested in the presence of 13 antibiotics from six classes. A bioassay was used to measure the ability of resistance-causing enzymes to decrease the concentration of active antibiotics in the medium. RESULTS: We confirmed IR in the presence of β-lactam antibiotics (ampicillin and mecillinam) when TEM-1A was expressed. We found that bacteria expressing antibiotic-modifying or -degrading enzymes Ere(A), Tet(X2) or CatA1 caused IR in the presence of macrolides (erythromycin and clarithromycin), tetracyclines (tetracycline and tigecycline) and chloramphenicol, respectively. IR was not observed with resistance determinants that did not modify or destroy antibiotics or with enzymes modifying aminoglycosides or degrading fosfomycin. IR was dependent on the resistance enzymes decreasing the concentration of active antibiotics in the medium, hence allowing nearby susceptible bacteria to resume growth once the antibiotic concentration fell below their MIC. CONCLUSIONS: IR was not limited to β-lactamase-producing bacteria, but was also caused by resistant bacteria carrying cytoplasmic antibiotic-modifying or -degrading enzymes that catalyse energy-consuming reactions requiring complex cellular cofactors. Our results suggest that IR is common and further emphasizes that coinfecting agents and the human microflora can have a negative impact during antimicrobial therapy.201626467993
575950.9997The Relationship between Antibiotic Susceptibility and pH in the Case of Uropathogenic Bacteria. Urinary tract infections (UTIs) are common bacterial infections caused mainly by enteric bacteria. Numerous virulence factors assist bacteria in the colonization of the bladder. Bacterial efflux pumps also contribute to bacterial communication and to biofilm formation. In this study, the phenotypic and genetic antibiotic resistance of clinical UTI pathogens such as Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis were determined by disk diffusion method and polymerase chain reaction (PCR). Following this, different classes of antibiotics were evaluated for their antibacterial activity at pH 5, 6, 7 and 8 by a microdilution method. Gentamicin (GEN) was the most potent antibacterial agent against E. coli strains. The effect of GEN on the relative expression of marR and sdiA genes was evaluated by quantitative PCR. The slightly acidic pH (pH 6) and GEN treatment induced the upregulation of marR antibiotic resistance and sdiA QS activator genes in both E. coli strains. Consequently, bacteria had become more susceptible to GEN. It can be concluded that antibiotic activity is pH dependent and so the artificial manipulation of urinary pH can contribute to a more effective therapy of multidrug resistant bacterial infections.202134943643
565160.9997Class 1 integron causes vulnerability to formaldehyde in Escherichia coli. In this study, the relationships of integron 1 element, formaldehyde dehydrogenase, and orfF genes with the level of formaldehyde resistance of isolated E. coli were investigated. E. coli bacteria were isolated from apparently healthy and colibacillosis-affected broilers of Fars Province, Iran. Formaldehyde resistance level and the presence of genetic markers were measured using MIC, and PCR tests, respectively. The prevalence of integron 1 element, orfF, and formaldehyde dehydrogenase genes in E. coli isolates were 61%, 8%, and 94%, respectively. In addition, according to our cut off definition, 15% and 85% of isolates were resistant and sensitive to formaldehyde, respectively. None of the genes had a statistically significant relationship with the formaldehyde resistance; however, the isolates containing integron 1 were significantly more sensitive to formaldehyde in the MIC test than those without integron 1. Integron 1 gene cassette could carry some bacterial surface proteins and porins with different roles in bacterial cells. Formaldehyde could also interfere with the protein functions by alkylating and cross-linking, and this compound would affect bacterial cell surface proteins in advance. Through an increase in the cell surface proteins, the presence of integron 1 gene cassette might make E. coli more sensitive to formaldehyde. As integron 1 was always involved in increasing bacterial resistance to antibiotics and disinfectants such as QACs, this is the first report of bacterial induction of sensitivity to a disinfectant through integron 1. Finally, integron 1 does not always add an advantage to E. coli bacteria, and it could be assumed as a cause of vulnerability to formaldehyde.202134148112
473870.9996Detection and evaluation of susceptibility to antibiotics in non-hydrogen sulfide-producing antibiotic-resistant soil microbe: Pseudomonas guariconensis. Antimicrobial resistance in bacteria is a global threat that can make antibacterial treatments ineffective. One well-known method of antibiotic resistance and a common defensive mechanism in many harmful bacteria is the synthesis of endogenous hydrogen sulfide (H(2)S) in bacteria. In this study, soil bacteria were screened using the lead acetate agar test and the triple sugar iron test to determine that they were non-endogenous H(2)S producers. This was further validated by full genome analysis of the identified organism against the gene sequences of H(2)S-producing genes. Antibacterial resistance of the bacteria was phenotypically analyzed using the Kirby-Bauer disk diffusion method. Then, the effect of exogenous H(2)S on the antibiotic-resistant bacteria was checked in sodium sulfide, leading to antibiotic re-sensitization.202538767682
565680.9996Prevalence of silver resistance in bacteria isolated from diabetic foot ulcers and efficacy of silver-containing wound dressings. Silver dressings are used to manage wounds at risk of infection or locally infected. This in vitro study was conducted to assess the prevalence of silver resistance genes in 112 bacterial isolates obtained from the diabetic foot ulcers of patients attending the Diabetic Foot Clinic at Tameside General Hospital, UK. Using polymerase chain reaction to screen for three silver-resistance transcriptional units--silE, silS and silP--two silver-resistant bacteria were identified; both are strains of Enterobacter cloacae, an organism rarely implicated as a primary pathogen in chronic wounds. No recognized wound pathogens (Staphylococcus aureus-24 isolates and Pseudomonas aeruginosa-nine isolates) were found to contain silver-resistant genes. Analysis of the efficacy of silver-containing dressings on the silver-resistant strains of Enterobacter cloacae using confocal laser microscopy showed that, despite evidence of genetic resistance to silver, all strains were killed following a maximum of 48 hours of exposure to the dressings. Results suggest that presence of silver resistance genes is rare and that genetic resistance does not necessarily translate to phenotypic resistance to silver. While silver resistance in wound care should be monitored, the threat of widespread resistance is low and silver-containing dressings remain an extremely important tool in managing wound infection.200818382046
280190.9996Principal component analysis exploring the association between antibiotic resistance and heavy metal tolerance of plasmid-bearing sewage wastewater bacteria of clinical relevance. This paper unravels the occurrence of plasmid-mediated antibiotic resistance in association with tolerance to heavy metals among clinically relevant bacteria isolated from sewage wastewater. The bacteria isolated were identified following conventional phenotypic and/or molecular methods, and were subjected to multiple-antibiotic resistance (MAR) profiling. The isolates were tested against the heavy metals Hg(2+), Cd(2+), Cr(2+) and Cu(2+). SDS-PAGE and agarose gel electrophoretic analyses were performed, respectively, for the characterization of heavy metal stress protein and R-plasmid among the isolated bacteria. Principal component analysis was applied in determining bacterial resistance to antibiotics and heavy metals. Both lactose-fermenting ( Escherichia coli ) and non-fermenting ( Acinetobacter baumannii and Pseudomonas putida ) Gram-negative bacterial strains were procured, and showed MAR phenotypes with respect to three or more antibiotics, along with resistance to the heavy metals Hg(2+), Cd(2+), Cr(2+) and Cu(2+). The Gram-positive bacteria, Enterococcus faecalis , isolated had 'ampicillin-kanamycin-nalidixic acid' resistance. The bacterial isolates had MAR indices of 0.3-0.9, indicating their ( E. faecalis , E. coli , A. baumannii and P. putida ) origin from niches with high antibiotic pollution and human faecal contamination. The Gram-negative bacteria isolated contained a single plasmid (≈54 kb) conferring multiple antibiotic resistance, which was linked to heavy metal tolerance; the SDS-PAGE analysis demonstrated the expression of heavy metal stress proteins (≈59 and ≈10 kDa) in wastewater bacteria with a Cd(2+) stressor. The study results grant an insight into the co-occurrence of antibiotic resistance and heavy metal tolerance among clinically relevant bacteria in sewage wastewater, prompting an intense health impact over antibiotic usage.202032974572
3601100.9996R factors mediate resistance to mercury, nickel, and cobalt. Fifty-five clinical isolates and laboratory stocks of Escherichia coli and Salmonella were studied for resistance to each of ten metals. Eleven clinical isolates carrying R factors were resistant to mercury, and, in each case, the resistance was mediated by a previously undefined R-factor gene. The gene was phenotypically expressed within 2 to 4 minutes after entry into sensitive bacteria, but the basis for the resistance remains undefined. Fourteen strains, 12 infected with R factors, were resistant to cobalt and nickel, but these resistances were mediated by R-factor genes in only two strains; separate R-factor genes mediated the resistances to nickel and cobalt. These and other results indicate that the genetic composition of R factors is greater than that originally defined.19675337360
5773110.9996LBJMR medium: a new polyvalent culture medium for isolating and selecting vancomycin and colistin-resistant bacteria. BACKGROUND: Multi-drug resistant bacteria are a phenomenon which is on the increase around the world, particularly with the emergence of colistin-resistant Enterobacteriaceae and vancomycin-resistant enterococci strains. The recent discovery of a plasmid-mediated colistin resistance with the description of the transferable mcr-1 gene raised concerns about the need for an efficient detection method for these pathogens, to isolate infected patients as early as possible. The LBJMR medium was developed to screen for all polymyxin-resistant Gram-negative bacteria, including mcr-1 positive isolates, and vancomycin-resistant Gram-positive bacteria. RESULTS: The LBJMR medium was developed by adding colistin sulfate salt at a low concentration (4 μg/mL) and vancomycin (50 μg/mL), with glucose (7.5 g/L) as a fermentative substrate, to a Purple Agar Base (31 g/L). A total of 143 bacterial strains were used to evaluate this universal culture medium, and the sensitivity and specificity of detection were 100% for the growth of resistant strains. 68 stool samples were cultured on LBJMR, and both colistin-resistant Gram-negative and vancomycin-resistant Gram-positive strains were specifically detected. CONCLUSIONS: The LBJMR medium is a multipurpose selective medium which makes it possible to identify bacteria of interest from clinical samples and to isolate contaminated patients in hospital settings. This is a simple medium that could be easily used for screening in clinical microbiology laboratories.201729169321
5499120.9996Antibiotic Resistance/Susceptibility Profiles of Staphylococcus equorum Strains from Cheese, and Genome Analysis for Antibiotic Resistance Genes. In food, bacteria carrying antibiotic resistance genes could play a prominent role in the spread of resistance. Staphylococcus equorum populations can become large in a number of fermented foods, yet the antibiotic resistance properties of this species have been little studied. In this work, the resistance/susceptibility (R/S) profile of S. equorum strains (n = 30) from cheese to 16 antibiotics was determined by broth microdilution. The minimum inhibitory concentration (MIC) for all antibiotics was low in most strains, although higher MICs compatible with acquired genes were also noted. Genome analysis of 13 strains showed the S. equorum resistome to be composed of intrinsic mechanisms, acquired mutations, and acquired genes. As such, a plasmidic cat gene providing resistance to chloramphenicol was found in one strain; this was able to provide resistance to Staphylococcus aureus after electroporation. An msr(A) polymorphic gene was identified in five strains. The Mrs(A) variants were associated with variable resistance to erythromycin. However, the genetic data did not always correlate with the phenotype. As such, all strains harbored a polymorphic fosB/fosD gene, although only one acquired copy was associated with strong resistance to fosfomycin. Similarly, a plasmid-associated blaR1-blaZI operon encoding a penicillinase system was identified in five ampicillin- and penicillin G-susceptible strains. Identified genes not associated with phenotypic resistance further included mph(C) in two strains and norA in all strains. The antibiotic R/S status and gene content of S. equorum strains intended to be employed in food systems should be carefully determined.202337511416
5772130.9996Molecular evaluation of colistin-resistant gene expression changes in Acinetobacter baumannii with real-time polymerase chain reaction. BACKGROUND: Acinetobacter baumannii is an important human pathogen which has recently gained increased attention due to the occurrence of drug-resistant nosocomial infections in patients suffering from immune system disorders, and those in hospital intensive care units. The aim of this research was to identify and isolate A. baumannii strains resistant to colistin, determine antibiotic resistance pattern of this bacteria, investigate the presence of colistin-resistant genes, and finally assess the effect of expression changes in pmrA and pmrB genes resistant to A. baumannii against colistin via real-time polymerase chain reaction. METHODS: The samples were initially purified and isolated using biochemical tests and Micro-gen kit. Later, the resistance pattern evaluation of validated samples to different antibiotics and colistin was carried out using two methods viz., disc diffusion and E-test. This was followed by the assessment of genes resistant to colistin via polymerase chain reaction besides gene expression changes via real-time polymerase chain reaction. RESULTS: The results of this study indicated that eleven strains of A. baumannii isolated from Shahid Rajaee Trauma Hospital were resistant to colistin. However, in the resistance pattern evaluation of A. baumannii isolated from Ali Asghar Hospital, all the strains were sensitive to colistin. In the evaluation of genes resistant to pmrA and pmrB, most of the strains resistant to colistin were carriers of these genes. Besides, in the expression assessment of these genes, it was demonstrated that expression of pmrA in the strains resistant to colistin significantly increased in relation to sensitive strains, but the expression of pmrB increased at a lower rate in the strains resistant to colistin as compared to the sensitive strains. CONCLUSION: Thus, it can be safely mentioned that increased expression of pmrA was due to the resistance of A. baumannii to colistin.201729225477
5987140.9996Mutations in gyrA and parC QRDRs are not relevant for quinolone resistance in epidemiological unrelated Stenotrophomonas maltophilia clinical isolates. Clinical strains of Stenotrophomonas maltophilia are often highly resistant to multiple antibiotics and this resistance is steadily rising. Quinolones are included in the group of antimicrobial agents to which this microorganism is developing resistance. Therefore, the aim of this study was to analyze the epidemiological relationship among 22 clinical isolates of S. maltophilia as well as the molecular mechanisms responsible for the acquisition of quinolone-resistance in these strains. The results of the pulsed-field gel electrophoresis (PFGE) showed an heterogenicity of 82% among the strains used in the study. On the other hand, no amino acid changes were found in the quinolone resistance-determining region (QRDR) of either gyrA and parC genes among quinolone-susceptible and -resistant S. maltophilia strains. Besides, the amino acid of the GyrA found in the position equivalent to Ser-83 of E. coli was Gln instead of a Ser or Thr, the amino acids usually encountered in this position among Gram-negative bacteria. The results suggest that there is not a relationship between the presence of this Gln and the resistance to quinolones in S. maltophilia. We can conclude that, contrary to what has been described in other microorganisms, in these S. maltophilia isolates, the development of resistance to quinolones was not related to mutations in the QRDR of gyrA and parC genes. Thus, to our knowledge, this is the first report describing this phenomenon.200212523620
5754150.9996Efflux pump inhibitor CCCP to rescue colistin susceptibility in mcr-1 plasmid-mediated colistin-resistant strains and Gram-negative bacteria. OBJECTIVES: Efflux in bacteria is a ubiquitous mechanism associated with resistance to antimicrobials agents. Efflux pump inhibitors (EPIs) have been developed to inhibit efflux mechanisms and could be a good alternative to reverse colistin resistance, but only CCCP has shown good activity. The aim of our study was to identify CCCP activity in a collection of 93 Gram-negative bacteria with known and unknown colistin resistance mechanisms including isolates with mcr-1 plasmid-mediated colistin resistance. METHODS: Colistin MIC was evaluated with and without CCCP and the fold decrease of colistin MIC was calculated for each strain. In order to evaluate the effect of this combination, a time-kill study was performed on five strains carrying different colistin resistance mechanisms. RESULTS: Overall, CCCP was able to reverse colistin resistance for all strains tested. The effect of CCCP was significantly greater on intrinsically colistin-resistant bacteria (i.e. Proteus spp., Serratia marcescens, Morganella morganii and Providencia spp.) than on other Enterobacteriaceae (P < 0.0001). The same was true for bacteria with a heteroresistance mechanism compared to bacteria with other colistin resistance mechanisms (P < 0.0001). A time-kill study showed the combination was bacteriostatic on strains tested. CONCLUSIONS: These results suggest an efflux mechanism, especially on intrinsically resistant bacteria and Enterobacter spp., but further analysis is needed to identify the molecular support of this mechanism. EPIs could be an alternative for restoring colistin activity in Gram-negative bacteria. Further work is necessary to identify new EPIs that could be used in humans.201829718423
5769160.9996Analysis of Nucleotide Sequences Similarity and Protein Prediction of Some Resistance Genes in Escherichia coli Isolated from Iraqi Patients with Urinary Tract Infections. Antibiotic resistance leads to a dramatic increase in the morbidity and mortality caused by infectious diseases. Even though estimates vary widely, the economic cost of antimicrobial-resistant bacteria is on a rise. The current aimed to identify the antimicrobial resistance of Escherichia coli (E. coli). In fact, this study focused on the recent deep-learning methods (sequencing) to investigate E. coli antibiotic resistance and their protein sequences. To evaluate antibiotic resistance, the sequencing method could be considered the method of choice. The E. coli was identified by either specific biochemical tests or polymerase chain reaction (PCR) using the 16S rRNA gene. The results of aadA1 gene sequences demonstrated 10 nucleic acid substitutions throughout, as compared to the reference NCBI database (MG385063). Out of the 10 nucleic acid substitutions, 9 missense effects were observed. While the dfrA1 gene sequences illustrated 20 nucleic acid substitutions throughout, compared to the reference NCBI database (KY706080), out of the 20 nucleic acid substitutions, 8 missense effects were observed. Furthermore, the sul1 gene sequences displayed 20 nucleic acid substitutions throughout, in comparison with the reference NCBI database (CP069561), and out of the 20 nucleic acid substitutions, 12 missense effects were detected. The cat1 gene sequences showed 14 nucleic acid substitutions throughout, compared to the reference NCBI database (NC017660), and out of the 14 nucleic acid substitutions, 8 missense effects were observed. The precise point (Missense) mutation in four genes (aadA1, dfrA1, sul1, and cat1) in the expected sequence is interpreted to be the target site of a site-specific recombination mechanism that led to antibiotics resistance in E. coli isolates.202236618275
3599170.9996Distribution of the pco Gene Cluster and Associated Genetic Determinants among Swine Escherichia coli from a Controlled Feeding Trial. Copper is used as an alternative to antibiotics for growth promotion and disease prevention. However, bacteria developed tolerance mechanisms for elevated copper concentrations, including those encoded by the pco operon in Gram-negative bacteria. Using cohorts of weaned piglets, this study showed that the supplementation of feed with copper concentrations as used in the field did not result in a significant short-term increase in the proportion of pco-positive fecal Escherichia coli. The pco and sil (silver resistance) operons were found concurrently in all screened isolates, and whole-genome sequencing showed that they were distributed among a diversity of unrelated E. coli strains. The presence of pco/sil in E. coli was not associated with elevated copper minimal inhibitory concentrations (MICs) under a variety of conditions. As found in previous studies, the pco/sil operons were part of a Tn7-like structure found both on the chromosome or on plasmids in the E. coli strains investigated. Transfer of a pco/sil IncHI2 plasmid from E. coli to Salmonella enterica resulted in elevated copper MICs in the latter. Escherichia coli may represent a reservoir of pco/sil genes transferable to other organisms such as S. enterica, for which it may represent an advantage in the presence of copper. This, in turn, has the potential for co-selection of resistance to antibiotics.201830340352
5671180.9996Biofilms and antibiotic susceptibility of multidrug-resistant bacteria from wild animals. BACKGROUND: The "One Health" concept recognizes that human health and animal health are interdependent and bound to the health of the ecosystem in which they (co)exist. This interconnection favors the transmission of bacteria and other infectious agents as well as the flow of genetic elements containing antibiotic resistance genes. This problem is worsened when pathogenic bacteria have the ability to establish as biofilms. Therefore, it is important to understand the characteristics and behaviour of microorganisms in both planktonic and biofilms states from the most diverse environmental niches to mitigate the emergence and dissemination of resistance. METHODS: The purpose of this work was to assess the antibiotic susceptibility of four bacteria (Acinetobacter spp., Klebsiella pneumoniae, Pseudomonas fluorescens and Shewanella putrefaciens) isolated from wild animals and their ability to form biofilms. The effect of two antibiotics, imipenem (IPM) and ciprofloxacin (CIP), on biofilm removal was also assessed. Screening of resistance genetic determinants was performed by PCR. Biofilm tests were performed by a modified microtiter plate method. Bacterial surface hydrophobicity was determined by sessile drop contact angles. RESULTS: The susceptibility profile classified the bacteria as multidrug-resistant. Three genes coding for β-lactamases were detected in K. pneumoniae (TEM, SHV, OXA-aer) and one in P. fluorescens (OXA-aer). K. pneumoniae was the microorganism that carried more β-lactamase genes and it was the most proficient biofilm producer, while P. fluorescens demonstrated the highest adhesion ability. Antibiotics at their MIC, 5 × MIC and 10 × MIC were ineffective in total biofilm removal. The highest biomass reductions were found with IPM (54% at 10 × MIC) against K. pneumoniae biofilms and with CIP (40% at 10 × MIC) against P. fluorescens biofilms. DISCUSSION: The results highlight wildlife as important host reservoirs and vectors for the spread of multidrug-resistant bacteria and genetic determinants of resistance. The ability of these bacteria to form biofilms should increase their persistence.201829910986
5838190.9996Alteration in the Morphological and Transcriptomic Profiles of Acinetobacter baumannii after Exposure to Colistin. Acinetobacter baumannii is often highly resistant to multiple antimicrobials, posing a risk of treatment failure, and colistin is a "last resort" for treatment of the bacterial infection. However, colistin resistance is easily developed when the bacteria are exposed to the drug, and a comprehensive analysis of colistin-mediated changes in colistin-susceptible and -resistant A. baumannii is needed. In this study, using an isogenic pair of colistin-susceptible and -resistant A. baumannii isolates, alterations in morphologic and transcriptomic characteristics associated with colistin resistance were revealed. Whole-genome sequencing showed that the resistant isolate harbored a PmrB(L208F) mutation conferring colistin resistance, and all other single-nucleotide alterations were located in intergenic regions. Using scanning electron microscopy, it was determined that the colistin-resistant mutant had a shorter cell length than the parental isolate, and filamented cells were found when both isolates were exposed to the inhibitory concentration of colistin. When the isolates were treated with inhibitory concentrations of colistin, more than 80% of the genes were upregulated, including genes associated with antioxidative stress response pathways. The results elucidate the morphological difference between the colistin-susceptible and -resistant isolates and different colistin-mediated responses in A. baumannii isolates depending on their susceptibility to this drug.202439203486