Clinical Resistant Strains of Enterococci and Their Correlation to Reduced Susceptibility to Biocides: Phenotypic and Genotypic Analysis of Macrolides, Lincosamides, and Streptogramins. - Related Documents




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593001.0000Clinical Resistant Strains of Enterococci and Their Correlation to Reduced Susceptibility to Biocides: Phenotypic and Genotypic Analysis of Macrolides, Lincosamides, and Streptogramins. Enterococci are troublesome nosocomial, opportunistic Gram-positive cocci bacteria showing enhanced resistance to many commonly used antibiotics. This study aims to investigate the prevalence and genetic basis of antibiotic resistance to macrolides, lincosamides, and streptogramins (MLS) in Enterococci, as well as the correlation between MLS resistance and biocide resistance. From 913 clinical isolates collected from King Khalid Hospital, Hail, Saudi Arabia, 131 isolates were identified as Enterococci spp. The susceptibility of the clinical enterococcal isolates to several MLS antibiotics was determined, and the resistance phenotype was detected by the triple disk method. The MLS-involved resistance genes were screened in the resistant isolates. The current results showed high resistance rates to MLS antibiotics, and the constitutive resistance to all MLS (cMLS) was the most prevalent phenotype, observed in 76.8% of resistant isolates. By screening the MLS resistance-encoding genes in the resistant isolates, the erythromycin ribosome methylase (erm) genes that are responsible for methylation of bacterial 23S rRNA were the most detected genes, in particular, ermB. The ereA esterase-encoding gene was the most detected MLS modifying-encoding genes, more than lnuA (adenylation) and mphC (phosphorylation). The minimum inhibitory concentrations (MICs) of commonly used biocides were detected in resistant isolates and correlated with the MICs of MLS antibiotics. The present findings showed a significant correlation between MLS resistance and reduced susceptibility to biocides. In compliance with the high incidence of the efflux-encoding genes, especially mefA and mefE genes in the tolerant isolates with higher MICs to both MLS antibiotics and biocides, the efflux of resistant isolates was quantified, and there was a significant increase in the efflux of resistant isolates with higher MICs as compared to those with lower MICs. This could explain the crucial role of efflux in developing cross-resistance to both MLS antibiotics and biocides.202336978327
549810.9998The prevalence of multidrug resistance in Staphylococcus hominis isolated from clinical materials. The treatment of infections caused by Staphylococcus hominis remains a challenge, mainly due to the increasing resistance of these bacteria to antibiotics. The aim of the study was to determine antibiotic resistance in 62 strains S. hominis isolated from clinical materials, and to identify the molecular basis of resistance to antibiotics. Forty-six strains were both methicillin-resistant and harbored the mecA gene. Twenty-three of these strains had mec complex A and ccr complex AB1. Such a combination of the mec and ccr complexes does not correspond to any cassettes that have been demonstrated so far. However, over 80% of the tested strains were multidrug-resistant, of which as many as 12 were resistant to at least seven antibiotics. More than a half of strains harbored the tetK, acc(6')-Ie aph(2''), and ant(4')-I genes. erm(C) was the most common resistant gene to antibiotics from the MLS group. Two strains had as many as five antibiotic resistance genes from the tested groups (erm(C), msr(A), msr(B), mph(C), lnu(A)). The presence of the vga gene encoding resistance to streptogramins A was detected in one strain. All of strains were sensitive to vancomycin. However, 11 of them had reduced sensitivity to this antibiotic and eight of them were characterized by a heterogeneous resistance profile to this antibiotic. Our results clearly shows increasing threat of S. hominis caused by their multi-resistance. Moreover, these bacteria can constitute a reservoir of resistance genes for more pathogenic bacteria.202539747570
244220.9998Macrolide, lincosamide, and streptogramin B resistance in lipophilic Corynebacteria inhabiting healthy human skin. Corynebacteria exist as part of human skin microbiota. However, under some circumstances, they can cause opportunistic infections. The subject of the study was to examine the macrolide-lincosamide-streptogramin B (MLSB) antibiotic resistance in 99 lipophilic strains of Corynebacterium genus isolated from the skin of healthy men. Over 70% of the tested strains were resistant to erythromycin and clindamycin. All of which demonstrated a constitutive type of MLSB resistance mechanism. In all strains, there were being investigated the erm(A), erm(B), erm(C), erm(X), lin(A), msr(A), and mph(C) genes that could be responsible for the different types of resistance to marcolides, lincosamides, and streptogramin B. In all strains with the MLSB resistance phenotype, the erm(X) gene was detected. None of the other tested genes were discovered. Strains harboring the erm(X) gene were identified using a phenotypic method based on numerous biological and biochemical tests. Identification of the chosen strains was compared with the results of API Coryne, MALDI-TOF MS, and 16S rDNA sequencing methods. Only 7 out of the 23 investigated resistant strains provided successful results in all the used methods, showing that identification of this group of bacteria is still a great challenge. The MLSB resistance mechanism was common in most frequently isolated from healthy human skin Corynebacterium tuberculostearicum and Corynebacterium jeikeium strains. This represents a threat as these species are also commonly described as etiological factors of opportunistic infections.201424735183
286830.9998Detection and Analysis of Drug and Disinfectant Resistance Genes in the Sewage of a Center for Disease Control and Prevention. PURPOSE: Sewage is a significant reservoir for drug and disinfectant resistance genes and a medium for dissemination. This study aimed to evaluate the presence of drug and disinfectant resistance genes in the sewage of a Center for Disease Control and Prevention (CDC) and to assess the risks of their dissemination. METHODS: Sewage from a CDC in Hangzhou was collected, filtered, and enriched, and its microorganisms were cultured. The isolated bacteria were identified, and the minimum inhibitory concentration (MIC) was determined. The drug and disinfectant resistance genes in the sewage and bacteria were detected through polymerase chain reaction amplification. RESULTS: Three kinds of bacteria were isolated from the sewage sample. The MIC for Sphingomonas and Staphylococcus xylosus against chlorine-containing disinfectants was 250 mg/L, whereas the MIC for Bacillus firmus was 500 mg/L. The β-lactam resistance gene TEM and the disinfectant resistance gene qacA were positive in the bacteria, whereas the β-lactam resistance genes TEM, SHV, and VIM-1, the tetracycline resistance gene tetM, the aminoglycoside resistance genes aac(6')/aph(2') and aph3'-III, and the disinfectant resistance genes qacA, qacE, and qacEΔ1 were positive in the sewage. CONCLUSION: Drug and disinfectant resistance genes were found in the sewage of a CDC and were associated with bacteria. Thus, optimizing the monitoring and treatment of sewage is crucial.202540303605
593840.9998Characterization of Mechanisms Lowering Susceptibility to Flumequine among Bacteria Isolated from Chilean Salmonid Farms. Despite their great importance for human therapy, quinolones are still used in Chilean salmon farming, with flumequine and oxolinic acid currently approved for use in this industry. The aim of this study was to improve our knowledge of the mechanisms conferring low susceptibility or resistance to quinolones among bacteria recovered from Chilean salmon farms. Sixty-five isolates exhibiting resistance, reduced susceptibility, or susceptibility to flumequine recovered from salmon farms were identified by their 16S rRNA genes, detecting a high predominance of species belonging to the Pseudomonas genus (52%). The minimum inhibitory concentrations (MIC) of flumequine in the absence and presence of the efflux pump inhibitor (EPI) Phe-Arg-β-naphthylamide and resistance patterns of isolates were determined by a microdilution broth and disk diffusion assays, respectively, observing MIC values ranging from 0.25 to >64 µg/mL and a high level of multi-resistance (96%), mostly showing resistance to florfenicol and oxytetracycline. Furthermore, mechanisms conferring low susceptibility to quinolones mediated by efflux pump activity, quinolone target mutations, or horizontally acquired resistance genes (qepA, oqxA, aac(6')-lb-cr, qnr) were investigated. Among isolates exhibiting resistance to flumequine (≥16 µg/mL), the occurrence of chromosomal mutations in target protein GyrA appears to be unusual (three out of 15), contrasting with the high incidence of mutations in GyrB (14 out of 17). Bacterial isolates showing resistance or reduced susceptibility to quinolones mediated by efflux pumps appear to be highly prevalent (49 isolates, 75%), thus suggesting a major role of intrinsic resistance mediated by active efflux.201931847389
549950.9998Antibiotic 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
559760.9998Prevalence of macrolide-lincosamide-streptogramin resistant lactic acid bacteria isolated from food samples. Lactic acid bacteria (LAB) being a reservoir of antibiotic resistance genes, tend to disseminate antibiotic resistance that possibly pose a threat to human and animal health. Therefore, the study focuses on the prevalence of macrolide-lincosamide-streptogramin- (MLS) resistance among LAB isolated from various food samples. Diverse phenotypic and genotypic MLS resistance were determined among the LAB species (n = 146) isolated from fermented food products (n = 6) and intestine of food-producing animals (n = 4). Double disc, triple disc diffusion and standard minimum inhibitory concentration (MIC) tests were evaluated for phenotypic MLS resistance. Specific primers for MLS resistance genes were used for the evaluation of genotypic MLS resistance and gene expressions using total RNA of each isolate at different antibiotic concentrations. The isolates identified are Levilactobacillus brevis (n = 1), Enterococcus hirae (n = 1), Limosilactobacillus fermentum (n = 2), Pediococcus acidilactici (n = 3), Enterococcus faecalis (n = 1). The MIC tests along with induction studies displayed cMLS(b), L phenotype, M phenotype, KH phenotype, I phenotype resistance among MLS antibiotics. Genotypic evaluation tests revealed the presence of ermB, mefA/E, msrA/B and msrC genes. Also, gene expression studies displayed increased level of gene expression to the twofold increased antibiotic concentrations. In the view of global health concern, this study identified that food samples and food-producing animals represent source of antibiotic resistant LAB that can disseminate resistance through food chain. This suggests the implementation of awareness in the use of antibiotics as growth promoters and judicious use of antibiotics in veterinary sectors in order to prevent the spread of antibiotic resistance.202336712199
554970.9997Analysis of Antibiotic Resistance and Biofilm-Forming Capacity in Tetracycline-Resistant Bacteria from a Coastal Lagoon. Concerns have been raised regarding co-selection for antibiotic resistance among bacteria exposed to antibiotics used as growth promoters for some livestock and poultry species. Tetracycline had been commonly used for this purpose worldwide, and its residue has been associated with selection of resistant bacteria in aquatic biofilms. This study aimed to determine the resistance profile, the existence of some beta-lactamases genes and the capacity to form biofilm of bacteria isolated from water samples previously exposed to tetracycline (20 mg/L). Thirty-seven tetracycline-resistant bacterial strains were identified as Serratia marcescens, Escherichia coli, Morganella morganii, Pseudomonas aeruginosa, Citrobacter freundii, Providencia alcalifaciens, and Enterococcus faecium. The highest percentage of resistance was for ampicillin (75.75%) and amoxicillin/clavulanic acid (66.66%) in the Gram-negative bacteria and an E. faecium strain showed high resistance to vancomycin (minimum inhibitory concentration 250 μg/mL). Among the strains analyzed, 81.09% had multidrug resistance and eight Gram-negatives carried the bla(OXA-48) gene. All strains were able to form biofilm and 43.23% were strong biofilm formers. This study suggests that resistant bacteria can be selected under selection pressure of tetracycline, and that these bacteria could contribute to the maintenance and spread of antimicrobial resistance in this environment.202235325574
281980.9997Prevalence of Antibiotic-Resistant Lactobacilli in Sepsis Patients with Long-Term Antibiotic Therapy. Lactobacilli are the most common probiotic bacteria found in the human gut microbiota, and the presence of acquired antibiotic resistance determinants carried on mobile genetic elements must be screened due to safety concerns. Unnecessary and inappropriate antibiotic therapy, as well as ingested antibiotic resistance bacteria (originating from food or food products), influence the abundance of antibiotic resistance genes in human guts, with serious clinical consequences. The current study looked into the antibiotic resistance of lactobacilli isolated from the guts of sepsis patients on long-term antibiotic therapy. The broth microdilution method was used to investigate the minimum inhibitory concentrations (MICs) of antibiotics such as imipenem, meropenem, erythromycin, tetracycline, cefepime, ciprofloxacin, and gentamycin, and the molecular genetic basis of resistance was studied based on the MIC values. The isolates were phenotypically resistant to tetracycline (20%), fluoroquinolone (20%), and macrolide (5%). Following that, resistance genes for tetracycline [tet(L), tet(O), tet(K), and tet(M)], macrolide [erm(B) and erm(C)], and beta-lactams [bla(CMY)] were investigated. Tetracycline or macrolide resistance genes were not found in the isolates, and only one isolate possessed the bla(CMY) resistance gene. The findings suggested that tetracycline and macrolide resistance may be linked to other resistance genes that were not investigated in this study. Because tetracyclines, fluoroquinolones, and macrolides are commonly used in clinics and animals, there has been concern about the spread of resistance in humans. If acquired antibiotic resistance is passed down through mobile genetic elements, it may serve as a reservoir of resistance for gut pathogens and other microbiome environments.202236088413
243990.9997Differences in distribution of MLS antibiotics resistance genes in clinical isolates of staphylococci belonging to species: S. epidermidis, S. hominis, S. haemolyticus, S. simulans and S. warneri. BACKGROUND: Macrolides and lincosamides are two leading types of antibiotics commonly used in therapies. The study examines the differences in resistance to these antibiotics and their molecular bases in S. epidermidis as well as in rarely isolated species of coagulase-negative staphylococci such as S. hominis, S. haemolyticus, S. warneri and S. simulans. The isolates were tested for the presence of the erm(A), erm(B), erm(C), lnu(A), msr(A), msr(B), mph(C), ere(A) and ere(B) genes. Phenotypic resistance to methicillin and mecA presence were also determined. RESULTS: The MLS(B) resistance mechanism was phenotypically found in isolates of species included in the study. The most prevalent MLS(B) resistance mechanism was observed in S. hominis, S. haemolyticus and S. epidermidis isolates mainly of the MLS(B) resistance constitutive type. Macrolide, lincosamide and streptogramin B resistance genes were rarely detected in isolates individually. The erm(B), ere(A) and ere(B) genes were not found in any of the strains. The erm(A) gene was determined only in four strains of S. epidermidis and S. hominis while lnu(A) was seen in eight strains (mainly in S. hominis). The erm(C) gene was present in most of S. epidermidis strains and predominant in S. hominis and S. simulans isolates. The examined species clearly differed between one another in the repertoire of accumulated genes. CONCLUSIONS: The presence of genes encoding the MLS(B) resistance among CoNS strains demonstrates these genes' widespread prevalence and accumulation in opportunistic pathogens that might become gene reservoir for bacteria with superior pathogenic potential.201931182020
5538100.9997Phenotypic and genotypic antimicrobial susceptibility pattern of Streptococcus spp. isolated from cases of clinical mastitis in dairy cattle in Poland. Mastitis of dairy cattle is one of the most frequently diagnosed diseases worldwide. The main etiological agents of mastitis are bacteria of the genus Streptococcus spp., in which several antibiotic resistance mechanisms have been identified. However, detailed studies addressing this problem have not been conducted in northeastern Poland. Therefore, the aim of our study was to analyze, on phenotypic and genotypic levels, the antibiotic resistance pattern of Streptococcus spp. isolated from clinical cases of mastitis from dairy cattle in this region of Poland. The research was conducted using 135 strains of Streptococcus (Streptococcus uberis, n = 53; Streptococcus dysgalactiae, n = 41; Streptococcus agalactiae, n = 27; other streptococci, n = 14). The investigation of the antimicrobial susceptibility to 8 active substances applied in therapy in the analyzed region, as well as a selected bacteriocin (nisin), was performed using the minimum inhibitory concentration method. The presence of selected resistance genes (n = 14) was determined via PCR. We also investigated the correlation between the presence of resistance genes and the antimicrobial susceptibility of the examined strains in vitro. The highest observed resistance of Streptococcus spp. was toward gentamicin, kanamycin, and tetracycline, whereas the highest susceptibility occurred toward penicillin, enrofloxacin, and marbofloxacin. Additionally, the tested bacteriocin showed high efficacy. The presence of 13 analyzed resistance genes was observed in the examined strains [gene mef(A) was not detected]. In most strains, at least one resistance gene, mainly responsible for resistance to tetracyclines [tet(M), tet(K), tet(L)], was observed. However, a relationship between the presence of a given resistance gene and antimicrobial susceptibility on the phenotypic level was not always observed.201728601447
5646110.9997Dispersion and persistence of antimicrobial resistance genes among Staphylococcus spp. and Mammaliicoccus spp. isolated along a swine manure treatment plant. Staphylococcus spp. and Mammaliicoccus spp. colonize the skin and mucosa of humans and other animals and are responsible for several opportunistic infections. Staphylococci antibiotic resistance may be present in the environment due to the spread of treated and untreated manure from the livestock industry due to antibiotic use to disease control or growth promoter. In this work, we analyzed the species distribution and antimicrobial susceptibility of Staphylococcus and Mammaliicoccus species along different sites of a swine manure treatment plant from Southeastern Brazil. Bacterial colonies were obtained on mannitol salt agar, selected after catalase test and Gram staining, and finally identified by mass spectrometry and sequencing of the tuf gene. According to the results, S.cohnii and S. simulans were the most prevalent species. Antibiotic resistance test revealed that several strains were resistant to multiple drugs, with high levels of chloramphenicol resistance (98%), followed by erythromycin (79%), tetracycline (73%), gentamicin (46%), ciprofloxacin (42%), cefoxitin (18%), sulfamethoxazole + trimethoprim (12%), and linezolid (4%). In addition, gene detection by PCR showed that all strains carried at least 2 resistance genes and one of them carried all 11 genes investigated. Using the GTG(5)-PCR approach, a high genetic similarity was observed between some strains that were isolated from different points of the treatment plant. Although some were seemingly identical, differences in their resistance phenotype and genotype suggest horizontal gene transfer. The presence of resistant bacteria and resistance genes along the treatment system highlights the potential risk of contamination by people in direct contact with these animals and the soil since the effluent is used as a biofertilizer in the surrounding environment.202336515883
5642120.9997Identification and antimicrobial susceptibility of obligate anaerobic bacteria from clinical samples of animal origin. The etiology of veterinary infectious diseases has been the focus of considerable research, yet relatively little is known about the causative agents of anaerobic infections. Susceptibility studies have documented the emergence of antimicrobial resistance and indicate distinct differences in resistance patterns related to veterinary hospitals, geographic regions, and antibiotic-prescribing regimens. The aim of the present study was to identify the obligate anaerobic bacteria from veterinary clinical samples and to determinate the in vitro susceptibility to eight antimicrobials and their resistance-associated genes. 81 clinical specimens obtained from food-producing animals, pets and wild animals were examined to determine the relative prevalence of obligate anaerobic bacteria, and the species represented. Bacteroides spp, Prevotella spp and Clostridium spp represented approximately 80% of all anaerobic isolates. Resistance to metronidazole, clindamycin, tetracycline and fluoroquinolones was found in strains isolated from food-producing animals. Ciprofloxacin, enrofloxacin and cephalotin showed the highest resistance in all isolates. In 17%, 4% and 14% of tetracycline-resistant isolates, the resistance genes tetL, tetM and tetW were respectively amplified by PCR whereas in 4% of clindamycin-resistant strains the ermG gene was detected. 26% of the isolates were positive for cepA, while only 6% harbored the cfxA (resistance-conferring genes to beta-lactams). In this study, the obligate anaerobic bacteria from Costa Rica showed a high degree of resistance to most antimicrobials tested. Nevertheless, in the majority of cases this resistance was not related to the resistance acquired genes usually described in anaerobes. It is important to address and regulate the use of antimicrobials in the agricultural industry and the empirical therapy in anaerobic bacterial infections in veterinary medicine, especially since antibiotics and resistant bacteria can persist in the environment.201526385434
2440130.9997Molecular basis of resistance to macrolides, lincosamides and streptogramins in Staphylococcus hominis strains isolated from clinical specimens. Coagulase-negative staphylococci (CoNS) are the most frequently isolated bacteria from the blood and the predominant cause of nosocomial infections. Macrolides, lincosamides and streptogramin B (MLSB) antibiotics, especially erythromycin and clindamycin, are important therapeutic agents in the treatment of methicillin-resistant staphylococci infections. Among CoNS, Staphylococcus hominis represents the third most common organism. In spite of its clinical significance, very little is known about its mechanisms of resistance to antibiotics, especially MLSB. Fifty-five S. hominis isolates from the blood and the surgical wounds of hospitalized patients were studied. The erm(C) gene was predominant in erythromycin-resistant S. hominis isolates. The methylase genes, erm(A) and erm(B), were present in 15 and 25% of clinical isolates, respectively. A combination of various erythromycin resistance methylase (erm) genes was detected in 15% S. hominis isolates. The efflux gene msr(A) was detected in 18% of isolates, alone in four isolates, and in different combinations in a further six. The lnu(A) gene, responsible for enzymatic inactivation of lincosamides was carried by 31% of the isolates. No erythromycin resistance that could not be attributed to the genes erm(A), erm(B), erm(C) and msr(A) was detected. In S. hominis, 75 and 84%, respectively, were erythromycin resistant and clindamycin susceptible. Among erythromycin-resistant S. hominis isolates, 68% of these strains showed the inducible MLSB phenotype. Four isolates harbouring the msr(A) genes alone displayed the MSB phenotype. These studies indicated that resistance to MLSB in S. hominis is mostly based on the ribosomal target modification mechanism mediated by erm genes, mainly the erm(C), and enzymatic drug inactivation mediated by lnu(A).201626253583
5643140.9997Antibiotic resistance gene profiling of faecal and oral anaerobes collected during an antibiotic challenge trial. Here we describe a study examining the antibiotic resistance gene carriage in anaerobes collected during a clinical study. The results demonstrated that genes normally associated with anaerobes were most prevalent such as tetQ, cepA and cblA although several genes associated with Enterobacteriaceae including sul2, blaSHV and strB were also detected.201323933434
5639150.9997Disinfectant 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
5544160.9997Assessing the Effect of Oxytetracycline on the Selection of Resistant Escherichia coli in Treated and Untreated Broiler Chickens. Oxytetracycline (OTC) is administered in the poultry industry for the treatment of digestive and respiratory diseases. The use of OTC may contribute to the selection of resistant bacteria in the gastrointestinal tract of birds or in the environment. To determine the effect of OTC on the selection of resistant Escherichia coli strains post-treatment, bacteria were isolated from droppings and litter sampled from untreated and treated birds. Bacterial susceptibility to tetracyclines was determined by the Kirby-Bauer test. A total of 187 resistant isolates were analyzed for the presence of tet(A), (B), (C), (D), (E), and (M) genes by PCR. Fifty-four strains were analyzed by PFGE for subtyping. The proportion of tetracycline-resistant E. coli strains isolated was 42.88%. The susceptibility of the strains was treatment-dependent. A high clonal diversity was observed, with the tet(A) gene being the most prevalent, followed by tet(C). Even at therapeutic doses, there is selection pressure on resistant E. coli strains. The most prevalent resistance genes were tet(A) and tet(C), which could suggest that one of the main mechanisms of resistance of E. coli to tetracyclines is through active efflux pumps.202338136686
5932170.9997Detection of the florfenicol resistance gene floR in Chryseobacterium isolates from rainbow trout. Exception to the general rule? Bacteria from the family Flavobacteriaceae often show low susceptibility to antibiotics. With the exception of two Chryseobacterium spp. isolates that were positive for the florfenicol resistance gene floR, no clinical resistance genes were identified by microarray in 36 Flavobacteriaceae isolates from salmonid fish that could grow in ≥ 4 mg/L florfenicol. Whole genome sequence analysis of the floR positive isolates revealed the presence of a region that contained the antimicrobial resistance genes floR, a tet(X) tetracycline resistance gene, a streptothricin resistance gene and a chloramphenicol acetyltransferase gene. In silico analysis of 377 published genomes for Flavobacteriaceae isolates from a range of sources confirmed that well-characterised resistance gene cassettes were not widely distributed in bacteria from this group. Efflux pump-mediated decreased susceptibility to a range of antimicrobials was confirmed in both floR positive isolates using an efflux pump inhibitor (phenylalanine-arginine β-naphthylamide) assay. The floR isolates possessed putative virulence factors, including production of siderophores and haemolysins, and were mildly pathogenic in rainbow trout. Results support the suggestion that, despite the detection of floR, susceptibility to antimicrobials in Flavobacteriaceae is mostly mediated via intrinsic mechanisms rather than the horizontally acquired resistance genes more normally associated with Gram-negative bacterial pathogens such as Enterobacteriaceae.201728199699
4591180.9997Phenotypic and Genotypic Characterization of Antimicrobial Resistance in Streptococci Isolated from Human and Animal Clinical Specimens. Recently, the phenomenon of infection of humans as hosts by animal pathogens has been increasing. Streptococcus is an example of a genus in which bacteria overcome the species barrier. Therefore, monitoring infections caused by new species of human pathogens is critical to their spread. Seventy-five isolates belonging to streptococcal species that have recently been reported as a cause of human infections with varying frequency, were tested. The aim of the study was to determine the drug resistance profiles of the tested strains, the occurrence of resistance genes and genes encoding the most important streptococcal virulence factors. All tested isolates retained sensitivity to β-lactam antibiotics. Resistance to tetracyclines occurred in 56% of the tested strains. We have detected the MLS(B) type resistance (cross-resistance to macrolide, lincosamide, and streptogramin B) in 20% of the tested strains. 99% of the strains had tetracycline resistance genes. The erm class genes encoding MLS(B) resistance were present in 47% of strains. Among the strains with MLS(B) resistance, 92% had the streptokinase gene, 58% the streptolysin O gene and 33% the streptolysin S gene. The most extensive resistance concerned isolates that accumulated the most traits and genes, both resistance genes and virulence genes, increasing their pathogenic potential. Among the tested strains, the gene encoding streptokinase was the most common. The results of the prove that bacteria of the species S. uberis, S. dysgalactiae and S. gallolyticus are characterized by a high pathogenic potential and can pose a significant threat in case of infection of the human body.202337256427
5915190.9997Characterization of Two Macrolide Resistance-Related Genes in Multidrug-Resistant Pseudomonas aeruginosa Isolates. In analyzing the drug resistance phenotype and mechanism of resistance to macrolide antibiotics of clinical Pseudomonas aeruginosa isolates, the agar dilution method was used to determine the minimum inhibitory concentrations (MICs), and PCR (polymerase chain reaction) was applied to screen for macrolide antibiotics resistance genes. The macrolide antibiotics resistance genes were cloned, and their functions were identified. Of the 13 antibiotics tested, P. aeruginosa strains showed high resistance rates (ranging from 69.5-82.1%), and MIC levels (MIC90 > 256 μg/ml) to macrolide antibiotics. Of the 131 known macrolide resistance genes, only two genes, mphE and msrE, were identified in 262 clinical P. aeruginosa isolates. Four strains (1.53%, 4/262) carried both the msrE and mphE genes, and an additional three strains (1.15%, 3/262) harbored the mphE gene alone. The cloned msrE and mphE genes conferred higher resistance levels to three second-generation macrolides compared to two first-generation ones. Analysis of MsrE and MphE protein polymorphisms revealed that they are highly conserved, with only 1-3 amino acids differences between the proteins of the same type. It can be concluded that even though the strains showed high resistance levels to macrolides, known macrolide resistance genes are seldom present in clinical P. aeruginosa strains, demonstrating that a mechanism other than this warranted by the mphE and msrE genes may play a more critical role in the bacteria's resistance to macrolides.202033574864