LEFT - Word Related Documents




#
Rank
Similarity
Title + Abs.
Year
PMID
012345
540800.9941Identification and pathogenicity of an XDR Streptococcus suis isolate that harbours the phenicol-oxazolidinone resistance genes optrA and cfr, and the bacitracin resistance locus bcrABDR. One hundred and seven Streptococcus suis isolates were collected from healthy pigs or asymptomatic carriers in Jiangsu, China in 2016-2017. Thirty-eight percent of the isolates were linezolid-resistant and all carried the optrA gene. Among them, one isolate, SFJ44, was resistant to all 20 of the antibiotics tested, except for ceftiofur, and thus exhibited an extensively-drug-resistant phenotype. This isolate carried the optrA gene and the bacitracin resistance locus bcrABDR on an antibiotic-resistance-associated genomic island (ARGI1), and harboured the resistance genes cfr, aadE, sat4, spw-like, aphA3, mef(A), msr(D), erm(A)-like, erm(B), tetAB(P)', tet(M) and catQ on ARGI2∼4. The IS1216E-bcrABDR-ISEnfa1 segment showed >99.9% sequence identity to corresponding sequences from other species. The cfr gene was located on ARGI4, and two IS6 family insertion sequences, IS1216E and ISTeha2, were found upstream and downstream of cfr-ΔISEnfa5, respectively. A circular intermediate of bcrABDR-ISEnfa1 was detected, suggesting the role of ISEnfa1 in dissemination of bcrABDR. Other antibiotic resistance genes might be acquired from different Gram-positive pathogens. Infection of zebrafish showed that SFJ44 exhibited a virulence level comparable to serotype 2 hypervirulent strain SC070731, highlighting the need for surveillance of the pathogenicity of multi-drug-resistant S. suis isolates. This is the first report of the co-existence of optrA and cfr, and of the bcrABDR locus in streptococci. As it has been suggested that S. suis may act as an antibiotic resistance reservoir contributing to the spread of resistance genes to major streptococcal pathogens, the potential dissemination of these resistance genes among Gram-positive bacteria is of concern and routine surveillance should be strengthened.201930981924
545210.9938Multidrug Resistance Plasmid pTZC1 Could Be Pooled among Cutibacterium Strains on the Skin Surface. Acne vulgaris is a chronic inflammatory skin disease that is exacerbated by Cutibacterium acnes. Although antimicrobials such as macrolides, clindamycin, and tetracyclines are used to treat acne caused by C. acnes, the increasing prevalence of antimicrobial-resistant C. acnes strains has become a global concern. In this study, we investigated the mechanism by which interspecies transfer of multidrug-resistant genes can lead to antimicrobial resistance. Specifically, the transfer of pTZC1 between C. acnes and C. granulosum isolated from specimens of patients with acne was investigated. Among the C. acnes and C. granulosum isolated from 10 patients with acne vulgaris, 60.0% and 70.0% of the isolates showed resistance to macrolides and clindamycin, respectively. The multidrug resistance plasmid pTZC1, which codes for macrolide-clindamycin resistance gene erm(50) and tetracycline resistance gene tet(W), was identified in both C. acnes and C. granulosum isolated from the same patient. In addition, whole-genome sequencing revealed that the pTZC1 sequences of C. acnes and C. granulosum showed 100% identity using comparative whole-genome sequencing analysis. Therefore, we hypothesize that the horizontal transfer of pTZC1 between C. acnes and C. granulosum strains may occur on the skin surface. The plasmid transfer test revealed a bidirectional transfer of pTZC1 between C. acnes and C. granulosum, and transconjugants that obtained pTZC1 exhibited multidrug resistance. In conclusion, our results revealed that the multidrug resistance plasmid pTZC1 could be transferred between C. acnes and C. granulosum. Furthermore, since pTZC1 transfer among different species may aid in the prevalence of multidrug resistant strains, antimicrobial resistance genes may have been pooled on the skin surface. IMPORTANCE The emergence of antimicrobial resistance not only in Cutibacterium acnes strain but also other skin bacteria such as Staphylococcus epidermidis is a big concern due to antimicrobial use for the treatment of acne vulgaris. Increased prevalence of macrolides-clindamycin resistant C. acnes relates to the acquisition of exogenous antimicrobial resistance genes. erm(50) is harbored by the multidrug resistance plasmid pTZC1, which has been found in C. acnes and C. granulosum strains isolated from patients with acne vulgaris. In this study, C. acnes and C. granulosum with pTZC1 were found in the same patient, and plasmid transfer between C. acnes and C. granulosum was proved by transconjugation assay. This study showed plasmid transfer between other species and the possibility of further prevalence antimicrobial resistance between Cutibacterium species.202336847559
366920.9937Detection of clinically relevant antimicrobial resistance determinants in warm-blooded marine animals in Livingston Island (South Shetland Islands, Antarctica): A field-based molecular genetics study. Molecular genetic studies of stools were performed to assess the spread of some clinically relevant antimicrobial resistance determinants (ARD) in a gentoo penguin (Pygoscelis papua) and an Antarctic fur seal (Arctocephalus gazella) on Livingston Island. Glycopeptide resistance genes (vanA/vanD and vanB) were detected in both fecal samples, while the penguin's one was also mecA-positive and bla(NDM)-positive. Because of the remoteness and the isolation of the sampling locations, the carriage of vancomycin-resistant Enterococcus spp., methicillin-resistant Staphylococcus aureus, and NDM-producing Enterobacterales or other gram-negative bacilli suggested an ocean pollution with antibiotic resistant bacteria (ARB). Additionally, due to the type of ARD we detected, our results are alarming, and they cannot be explained only with agricultural and/or aquacultural pollution. Even though the current study is a preliminary one, it also demonstrates the potential of the field genetics analyses carried out with minimal equipment as a reliable monitoring tool for pollution with ARB.202235597002
548030.9936Small Antimicrobial Resistance Plasmids in Livestock-Associated Methicillin-Resistant Staphylococcus aureus CC398. Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) isolates of the clonal complex 398 are often resistant to a number of antimicrobial agents. Studies on the genetic basis of antimicrobial resistance in these bacteria identified SCCmec cassettes, various transposons and plasmids of different sizes that harbor antimicrobial resistance genes. While large plasmids that carry multiple antimicrobial resistance genes - occasionally together with heavy metal resistance genes and/or virulence genes - are frequently seen in LA-MRSA ST398, certain resistance genes are also associated with small plasmids of up to 15 kb in size. These small resistance plasmids usually carry only one, but in rare cases also two or three antimicrobial resistance genes. In the current review, we focus on small plasmids that carry the macrolide-lincosamide-streptogramin B resistance genes erm(C) or erm(T), the lincosamide resistance gene lnu(A), the pleuromutilin-lincosamide-streptogramin A resistance genes vga(A) or vga(C), the spectinomycin resistance gene spd, the apramycin resistance gene apmA, or the trimethoprim resistance gene dfrK. The detailed analysis of the structure of these plasmids allows comparisons with similar plasmids found in other staphylococci and underlines in many cases an exchange of such plasmids between LA-MRSA ST398 and other staphylococci including also coagulase-negative staphylococci.201830283407
376340.9935Staphylococcus epidermidis MSCRAMM SesJ Is Encoded in Composite Islands. Staphylococcus epidermidis is a leading cause of nosocomial infections in patients with a compromised immune system and/or an implanted medical device. Seventy to 90% of S. epidermidis clinical isolates are methicillin resistant and carry the mecA gene, present in a mobile genetic element (MGE) called the staphylococcal cassette chromosome mec (SCCmec) element. Along with the presence of antibiotic and heavy metal resistance genes, MGEs can also contain genes encoding secreted or cell wall-anchored virulence factors. In our earlier studies of S. epidermidis clinical isolates, we discovered S. epidermidis surface protein J (SesJ), a prototype of a recently discovered subfamily of the microbial surface component recognizing adhesive matrix molecule (MSCRAMM) group. MSCRAMMs are major virulence factors of pathogenic Gram-positive bacteria. Here, we report that the sesJ gene is always accompanied by two glycosyltransferase genes, gtfA and gtfB, and is present in two MGEs, called the arginine catabolic mobile element (ACME) and the staphylococcal cassette chromosome (SCC) element. The presence of the sesJ gene was associated with the left-hand direct repeat DR_B or DR_E. When inserted via DR_E, the sesJ gene was encoded in the SCC element. When inserted via DR_B, the sesJ gene was accompanied by the genes for the type 1 restriction modification system and was encoded in the ACME. Additionally, the SCC element and ACME carry different isoforms of the SesJ protein. To date, the genes encoding MSCRAMMs have been seen to be located in the bacterial core genome. Here, we report the presence of an MSCRAMM in an MGE in S. epidermidis clinical isolates.IMPORTANCES. epidermidis is an opportunistic bacterium that has established itself as a successful nosocomial pathogen. The modern era of novel therapeutics and medical devices has extended the longevity of human life, but at the same time, we also witness the evolution of pathogens to adapt to newly available niches in the host. Increasing antibiotic resistance among pathogens provides an example of such pathogen adaptation. With limited opportunities to modify the core genome, most of the adaptation occurs by acquiring new genes, such as virulence factors and antibiotic resistance determinants present in MGEs. In this study, we describe that the sesJ gene, encoding a recently discovered cell wall-anchored protein in S. epidermidis, is present in both ACME and the SCC element. The presence of virulence factors in MGEs can influence the virulence potential of a specific strain. Therefore, it is critical to study the virulence factors found in MGEs in emerging pathogenic bacteria or strains to understand the mechanisms used by these bacteria to cause infections.202032071265
598350.9935Analysis of mutational patterns in quinolone resistance-determining regions of GyrA and ParC of clinical isolates. Fluoroquinolone (FQ)-resistant bacteria pose a major global health threat. Unanalysed genomic data from thousands of sequenced microbes likely contain important hints regarding the evolution of FQ resistance, yet this information lies fallow. Here we analysed the co-occurrence patterns of quinolone resistance mutations in genes encoding the FQ drug targets DNA gyrase (gyrase) and topoisomerase IV (topo-IV) from 36,402 bacterial genomes, representing 10 Gram-positive and 10 Gram-negative species. For 19 species, the likeliest routes toward resistance mutations in both targets were determined, and for 5 species those mutations necessary and sufficient to predict FQ resistance were also determined. Target mutation hierarchy was fixed in all examined Gram-negative species, with gyrase being the primary and topo-IV the secondary quinolone target, as well as in six of nine Gram-positive species, with topo-IV being the primary and gyrase the secondary target. By contrast, in three Gram-positive species (Staphylococcus haemolyticus, Streptococcus pneumoniae and Streptococcus suis), under some conditions gyrase became the primary and topo-IV the secondary target. The path through individual resistance mutations varied by species. Both linear and branched paths were identified in Gram-positive and Gram-negative organisms alike. Finally, FQ resistance could be predicted based solely on target gene quinolone resistance mutations for Acinetobacter baumannii, Escherichia coli and Staphylococcus aureus, but not Klebsiella pneumoniae or Pseudomonas aeruginosa. These findings have important implications both for sequence-based diagnostics and for understanding the emergence of FQ resistance.201930582984
580760.9935ST8-t008-SCC (mec) IV methicillin-resistant Staphylococcus aureus in retail fresh cheese. This study reports the finding of 3 ST8-t008-SCC (mec) IVa (2B) methicillin-resistant Staphylococcus aureus (MRSA) strains in fresh cheese purchased within a single market in Costa Rica. In line with the finding of the resistance genes mecA, blaZ, mph(C), and msr(A) in their genomes, these bacteria showed phenotypic resistance to multiple β-lactams and erythromycin. In addition, they carry genes for acquired resistance to aminoglycosides (aph(3')-III) and fosfomycin (fosD), and genes for a myriad of virulence factors, including adhesins, hemolysins, and exotoxins. Our strains share multiple genomic features with MRSA from the USA300 lineage, which is a widely distributed and highly virulent strain implicated in community infections. As a result, consuming these or similar products could lead to multidrug infections in susceptible individuals. These results highlight safety deficiencies in cheese production practices and emphasize the risk of foodborne transmission of hard-to-treat ST8 MRSA strains.202439650008
599170.9935Transferable plasmid-mediated antibiotic resistance in Listeria monocytogenes. A strain of Listeria monocytogenes, isolated from a patient with meningoencephalitis, was resistant to chloramphenicol, erythromycin, streptomycin, and tetracycline. The genes conferring resistance to these antibiotics were carried by a 37-kb plasmid, pIP811, that was self-transferable to other L monocytogenes cells, to enterococci-streptococci, and to Staphylococcus aureus. The efficacy of transfer and the stability of pIP811 were higher in enterococci-streptococci than in the other gram-positive bacteria. As indicated by nucleic acid hybridisation, the genes in pIP811 conferring resistance to chloramphenicol, erythromycin, and streptomycin were closely related to plasmid-borne determinants that are common in enterococci-streptococci. Plasmid pIP811 shared extensive sequence homology with pAM beta 1, the prototype broad host range resistance plasmid in these two groups of gram-positive cocci. These results suggest that emergence of multiple antibiotic resistance in Listeria spp is due to acquisition of a replicon originating in enterococci-streptococci. The dissemination of resistance to other strains of L monocytogenes is likely.19901972210
625880.9935Alterations in GyrA and ParC associated with fluoroquinolone resistance in Enterococcus faecium. High-level quinolone resistance in Enterococcus faecium was associated with mutations in both gyrA and parC genes in 10 of 11 resistant strains. On low-level resistant strain without such mutations may instead possess an efflux mechanism or alterations in the other subunits of the gyrase or topoisomerase IV genes. These findings are similar to those for other gram-positive bacteria, such as Enterococcus faecalis.199910103206
476290.9935The Impact of Harsh Stratospheric Conditions on Survival and Antibiotic Resistance Profile of Non-Spore Forming Multidrug Resistant Human Pathogenic Bacteria Causing Hospital-Associated Infections. Bacteria are constantly being lifted to the stratosphere due to air movements caused by weather phenomena, volcanic eruptions, or human activity. In the upper parts of the atmosphere, they are exposed to extremely harsh and mutagenic conditions such as UV and space radiation or ozone. Most bacteria cannot withstand that stress, but for a fraction of them, it can act as a trigger for selective pressure and rapid evolution. We assessed the impact of stratospheric conditions on the survival and antibiotic resistance profile of common non-spore-forming human pathogenic bacteria, both sensitive and extremely dangerous multidrug-resistant variants, with plasmid-mediated mechanisms of resistance. Pseudomonas aeruginosa did not survive the exposure. In the case of strains that were recovered alive, the survival was extremely low: From 0.00001% of Klebsiella pneumoniae carrying the ndm-1 gene and methicillin-resistant Staphylococcus aureus mecA-positive with reduced susceptibility to vancomycin (MRSA/VISA), to a maximum of 0.001% of K. pneumoniae sensitive to all common antibiotics and S. aureus sensitive to vancomycin (MRSA/VSSA). We noticed a tendency towards increased antibiotic susceptibility after the stratospheric flight. Antimicrobial resistance is a current real, global, and increasing problem, and our results can inform current understandings of antibiotic resistance mechanisms and development in bacteria.202336833485
4749100.9934Transient Silencing of Antibiotic Resistance by Mutation Represents a Significant Potential Source of Unanticipated Therapeutic Failure. Sporadic literature reports describe isolates of pathogenic bacteria that harbor an antibiotic resistance determinant but remain susceptible to the corresponding antibiotic as a consequence of a genetic defect. Such strains represent a source from which antibiotic resistance may reemerge to cause treatment failure in patients. Here, we report a systematic investigation into the prevalence and nature of this phenomenon, which we term silencing of antibiotic resistance by mutation (SARM). Instances of SARM were detected among 1,470 Staphylococcus aureus isolates through side-by-side comparison of antibiotic resistance genotype (as determined by whole-genome sequencing) versus phenotype (as assessed through susceptibility testing). Of the isolates analyzed, 152 (10.3%) harbored a silenced resistance gene, including 46 (3.1%) that exhibited SARM to currently deployed antistaphylococcal drugs. SARM resulted from diverse mutational events but most commonly through frameshift mutation of resistance determinants as a result of point deletion in poly(A) tracts. The majority (∼90%) of SARM strains reverted to antibiotic resistance at frequencies of ≥10(-9); thus, while appearing antibiotic sensitive in the clinical microbiology laboratory, most S. aureus isolates exhibiting SARM will revert to antibiotic resistance at frequencies achievable in patients. In view of its prevalence in a major pathogen, SARM represents a significant potential threat to the therapeutic efficacy of antibiotics.IMPORTANCE Antibiotic resistance hinders the treatment of bacterial infection. To guide effective therapy, clinical microbiology laboratories routinely perform susceptibility testing to determine the antibiotic sensitivity of an infecting pathogen. This approach relies on the assumption that it can reliably distinguish bacteria capable of expressing antibiotic resistance in patients, an idea challenged by the present study. We report that the important human pathogen Staphylococcus aureus frequently carries antibiotic resistance genes that have become inactivated ("silenced") by mutation, leading strains to appear antibiotic sensitive. However, resistance can rapidly reemerge in most such cases, at frequencies readily achievable in infected patients. Silent antibiotic resistance is therefore prevalent, transient, and evades routine detection, rendering it a significant potential threat to antibacterial chemotherapy.201931662453
5476110.9934Bile Carriage of optrA-Positive Enterococcus faecium in a Patient with Choledocholith. We isolated one Enterococcus faecium isolate SZ21B15 from a bile sample of a patient with choledocholith in Shenzhen, China in 2021. It was positive for oxazolidinone resistance gene optrA and was intermediate to linezolid. The whole genome of E. faecium SZ21B15 was sequenced by Illumina Hiseq. It belonged to ST533 within the clonal complex 17. The optrA gene and additional two resistance genes fexA and erm(A) were located within a 25,777-bp multiresistance region, which was inserted into the chromosomal radC gene, being chromosomal intrinsic resistance genes. The chromosomal optrA gene cluster found in E. faecium SZ21B15 was closely related to the corresponding regions of multiple optrA-carrying plasmids or chromosomes from Enterococcus, Listeria, Staphylococcus, and Lactococcus strains. It further highlights the ability of the optrA cluster that transfers between plasmids and chromosomes and evolves by a series of molecular recombination events. IMPORTANCE Oxazolidinone are effective antimicrobial agents for the treatment of infections caused by multidrug-resistant Gram-positive bacteria, including vancomycin-resistant enterococci. The emergence and global spread of transferable oxazolidinone resistance genes such as optrA is worrisome. Enterococcus spp. can become causes of hospital-associated infections and are also widely distributed in the gastrointestinal tracts of animals and the natural environment. In this study, one E. faecium isolate from bile sample carried chromosomal optrA, being intrinsic resistance gene. optrA-positive E. faecium in bile not only makes the treatment of gallstones difficult, but also may become a reservoir of resistance genes in the body.202336976027
4599120.9934Global acquisition of genetic material from different bacteria into the staphylococcal cassette chromosome elements of a Staphylococcus epidermidis isolate. Staphylococcus epidermidis has been suggested as a main reservoir of methicillin resistance and virulence genes facilitating the evolution of Staphylococcus aureus as a successful pathogen. However, it remains a mystery where and how S. epidermidis obtains these numerous genes to serve as the reservoir. In this study, methicillin-resistant S. epidermidis isolate NW32 from a mastitic milk sample was sequenced and its staphylococcal cassette chromosome (SCC) elements were characterised. The SCC composite island covered 3.5% of the genome and consisted of three intact SCC elements carrying resistance genes against β-lactam antibiotics, several heavy metals and polyamines as well as genes for utilisation of sorbitol as a carbon source. Analysis of the postulated evolutionary route suggested that the three SCC elements were assembled from genetic material from various bacterial species (staphylococci, streptococci, salinicocci and Lysinibacillus) from three habitats (human, soil and cow) in different countries (Asia, North America, South America and Europe). We propose that the hsdS restriction-modification profile and the lack of CRISPR (clustered regularly interspaced short palindromic repeat) sequences in this bacterium may facilitate the genetic exchange of SCC elements among different staphylococcal species.201728705673
5436130.9934Plasmid-Encoded Transferable mecB-Mediated Methicillin Resistance in Staphylococcus aureus. During cefoxitin-based nasal screening, phenotypically categorized methicillin-resistant Staphylococcus aureus (MRSA) was isolated and tested negative for the presence of the mecA and mecC genes as well as for the SCCmec-orfX junction region. The isolate was found to carry a mecB gene previously described for Macrococcus caseolyticus but not for staphylococcal species. The gene is flanked by β-lactam regulatory genes similar to mecR, mecI, and blaZ and is part of an 84.6-kb multidrug-resistance plasmid that harbors genes encoding additional resistances to aminoglycosides (aacA-aphD, aphA, and aadK) as well as macrolides (ermB) and tetracyclines (tetS). This further plasmidborne β-lactam resistance mechanism harbors the putative risk of acceleration or reacceleration of MRSA spread, resulting in broad ineffectiveness of β-lactams as a main therapeutic application against staphylococcal infections.201829350135
5832140.9934New quadriplex PCR assay for detection of methicillin and mupirocin resistance and simultaneous discrimination of Staphylococcus aureus from coagulase-negative staphylococci. Major challenges in diagnostic molecular microbiology are to develop a simple assay to distinguish Staphylococcus aureus from the less virulent but clinically important coagulase-negative staphylococci (CoNS) and to simultaneously determine their antibiotic resistance profiles. Multiplex PCR assays have been developed for the detection of methicillin- and mupirocin-resistant S. aureus and CoNS but not for the simultaneous discrimination of S. aureus from CoNS. We designed a new set of Staphylococcus genus-specific primers and developed a novel quadriplex PCR assay targeting the 16S rRNA (Staphylococcus genus specific), nuc (S. aureus species specific), mecA (a determinant of methicillin resistance), and mupA (a determinant of mupirocin resistance) genes to identify most staphylococci, to discriminate S. aureus from CoNS and other bacteria, and to simultaneously detect methicillin and mupirocin resistance. Validation of the assay with 96 ATCC control strains and 323 previously characterized clinical isolates, including methicillin- and mupirocin-sensitive and -resistant S. aureus and CoNS isolates and other bacteria, demonstrated 100% sensitivity, specificity, and accuracy. This assay represents a simple, rapid, accurate, and reliable approach for the detection of methicillin- and mupirocin-resistant staphylococci and offers the hope of preventing their widespread dissemination through early and reliable detection.200415528678
3739150.9934Survey of drug resistance associated gene mutations in Mycobacterium tuberculosis, ESKAPE and other bacterial species. Tuberculosis treatment includes broad-spectrum antibiotics such as rifampicin, streptomycin and fluoroquinolones, which are also used against other pathogenic bacteria. We developed Drug Resistance Associated Genes database (DRAGdb), a manually curated repository of mutational data of drug resistance associated genes (DRAGs) across ESKAPE (i.e. Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp.) pathogens, and other bacteria with a special focus on Mycobacterium tuberculosis (MTB). Analysis of mutations in drug-resistant genes listed in DRAGdb suggested both homoplasy and pleiotropy to be associated with resistance. Homoplasy was observed in six genes namely gidB, gyrA, gyrB, rpoB, rpsL and rrs. For these genes, drug resistance-associated mutations at codon level were conserved in MTB, ESKAPE and many other bacteria. Pleiotropy was exemplified by a single nucleotide mutation that was associated with resistance to amikacin, gentamycin, rifampicin and vancomycin in Staphylococcus aureus. DRAGdb data also revealed that mutations in some genes such as pncA, inhA, katG and embA,B,C were specific to Mycobacterium species. For inhA and pncA, the mutations in the promoter region along with those in coding regions were associated with resistance to isoniazid and pyrazinamide respectively. In summary, the DRAGdb database is a compilation of all the major MTB drug resistance genes across bacterial species, which allows identification of homoplasy and pleiotropy phenomena of DRAGs.202032488120
4752160.9934Antibiotic resistance in gram-positive bacteria: epidemiological aspects. The emergence and spread of antibiotic resistance in gram-positive bacterial pathogens has become an increasing problem. There has been a dramatic increase in the prevalence of methicillin-resistant Staphylococcus aureus (MRSA), coagulase-negative staphylococci and enterococci. This is mainly due to the clonal dissemination of certain epidemic multiply-resistant strains, for example, those of MRSA and S. pneumoniae, as well as to the spread of resistance genes as exemplified by those causing glycopeptide resistance in enterococci.199910511391
5981170.9934Alterations in the DNA topoisomerase IV grlA gene responsible for quinolone resistance in Staphylococcus aureus. A 4.2-kb DNA fragment conferring quinolone resistance was cloned from a quinolone-resistant clinical isolate of Staphylococcus aureus and was shown to possess a part of the grlB gene and a mutated grlA gene. S-80-->F and E-84-->K mutations in the grlA gene product were responsible for the quinolone resistance. The mutated grlA genes responsible for quinolone resistance were dominant over the wild-type allele, irrespective of gene dosage in a transformation experiment with the grlA gene alone. However, dominance by mutated grlA genes depended on gene dosage when bacteria were transformed with the grlA and grlB genes in combination. Quinolone-resistant gyrA mutants were easily isolated from a strain, S. aureus RN4220, carrying a plasmid with the mutated grlA gene, though this was not the case for other S. aureus strains lacking the plasmid. The elimination of this plasmid from such quinolone-resistant gyrA mutants resulted in marked increases in quinolone susceptibility. These results suggest that both DNA gyrase and DNA topoisomerase IV may be targets of quinolones and that the quinolone susceptibility of organisms may be determined by which of these enzymes is most quinolone sensitive.19968723458
5653180.9934Coagulase-Negative Staphylococci Determined as Blood Culture Contamination Have High Virulence Characteristic Including Transfer of Antibiotic Resistance Determinants to Staphylococcus aureus and Escherichia coli. This study aimed to evaluate the virulence of 36 clinical isolates estimated as blood culture contaminants (BCCs). MALDI-TOF MS classified all isolates as coagulase-negative staphylococci (CoNS) with the highest percentage of S. epidermidis (77.78%). All tested strains formed biofilms with greater ability at room temperature than 37 °C. CoNS were sensitive to vancomycin (0% resistance) and had relatively low resistance to linezolid and rifampicin (8.33 and 22.22% resistance). The highest resistance was observed for penicillin (94.44%). Moreover, we observed the transfer of antibiotic resistance genes from the tested CoNS to S. aureus and even to E. coli, although with lower efficiency. CoNS in planktonic form were completely combated by antiseptics after 10 and 60 s exposition, and activity against biofilms was time-dependent. The complete elimination of biofilms was observed after a 180 s exposure to Kodan and CITROclorex, and this exposure to Rivanol and Octenidyne showed still viable cells (>0.9 log CFU/mL). Our findings showed that a careful selection of antiseptics and extending the exposure time before blood collection can reduce the occurrence of blood culture contamination. However, our most important finding is the indication that CoNS naturally occurring on human skin and mucous membranes exhibit antibiotic resistance, and what is more, determinants of antibiotic resistance are transferred to both closely related Gram-positive bacteria and phylogenetically distant Gram-negative bacteria. Thus, our findings shed new light on CoNS-they indicate the necessity of their control due to the effective transfer of mobile genetic elements harboring antibiotic resistance genes, which may contribute to the spread of resistance genes and deepening the antibiotic crisis.202540362661
4595190.9933Transfer of mupirocin resistance from Staphylococcus haemolyticus clinical strains to Staphylococcus aureus through conjugative and mobilizable plasmids. Coagulase-negative staphylococci are thought to act as reservoirs of antibiotic resistance genes that can be transferred to Staphylococcus aureus, thus hindering the combat of this bacterium. In this work, we analyzed the presence of plasmids conferring resistance to the antibiotic mupirocin-widely used to treat and prevent S. aureus infections in hospital environments-in nosocomial S. haemolyticus strains. About 12% of the 75 strains tested were resistant to mupirocin, and this phenotype was correlated with the presence of plasmids. These plasmids were shown to be diverse, being either conjugative or mobilizable, and capable of transferring mupirocin resistance to S. aureus Our findings reinforce that S. haemolyticus, historically and mistakenly considered as a less important pathogen, is a reservoir of resistance genes which can be transferred to other bacteria, such as S. aureus, emphasizing the necessity of more effective strategies to detect and combat this emergent opportunistic pathogen.201627190144