The Distribution of Eight Antimicrobial Resistance Genes in Streptococcus oralis, Streptococcus sanguinis, and Streptococcus gordonii Strains Isolated from Dental Plaque as Oral Commensals. - Related Documents




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279801.0000The Distribution of Eight Antimicrobial Resistance Genes in Streptococcus oralis, Streptococcus sanguinis, and Streptococcus gordonii Strains Isolated from Dental Plaque as Oral Commensals. It has been proposed that oral commensal bacteria are potential reservoirs of a wide variety of antimicrobial resistance genes (ARGs) and could be the source of pathogenic bacteria; however, there is scarce information regarding this. In this study, three common streptococci of the mitis group (S. oralis, S. sanguinis, and S. gordonii) isolated from dental plaque (DP) were screened to identify if they were frequent reservoirs of specific ARGs (blaTEM, cfxA, tetM, tetW, tetQ, ermA, ermB, and ermC). DP samples were collected from 80 adults; one part of the sample was cultured, and from the other part DNA was obtained for first screening of the three streptococci species and the ARGs of interest. Selected samples were plated and colonies were selected for molecular identification. Thirty identified species were screened for the presence of the ARGs. From those selected, all of the S. sanguinis and S. oralis carried at least three, while only 30% of S. gordonii strains carried three or more. The most prevalent were tetM in 73%, and blaTEM and tetW both in 66.6%. On the other hand, ermA and cfxA were not present. Oral streptococci from the mitis group could be considered frequent reservoirs of specifically tetM, blaTEM, and tetW. In contrast, these three species appear not to be reservoirs of ermA and cfxA.202337999618
592110.9998Prevalence of tetracycline resistance genes in oral bacteria. Tetracycline is a broad-spectrum antibiotic used in humans, animals, and aquaculture; therefore, many bacteria from different ecosystems are exposed to this antibiotic. In order to determine the genetic basis for resistance to tetracycline in bacteria from the oral cavity, saliva and dental plaque samples were obtained from 20 healthy adults who had not taken antibiotics during the previous 3 months. The samples were screened for the presence of bacteria resistant to tetracycline, and the tetracycline resistance genes in these isolates were identified by multiplex PCR and DNA sequencing. Tetracycline-resistant bacteria constituted an average of 11% of the total cultivable oral microflora. A representative 105 tetracycline-resistant isolates from the 20 samples were investigated; most of the isolates carried tetracycline resistance genes encoding a ribosomal protection protein. The most common tet gene identified was tet(M), which was found in 79% of all the isolates. The second most common gene identified was tet(W), which was found in 21% of all the isolates, followed by tet(O) and tet(Q) (10.5 and 9.5% of the isolates, respectively) and then tet(S) (2.8% of the isolates). Tetracycline resistance genes encoding an efflux protein were detected in 4.8% of all the tetracycline-resistant isolates; 2.8% of the isolates had tet(L) and 1% carried tet(A) and tet(K) each. The results have shown that a variety of tetracycline resistance genes are present in the oral microflora of healthy adults. This is the first report of tet(W) in oral bacteria and the first report to show that tet(O), tet(Q), tet(A), and tet(S) can be found in some oral species.200312604515
549820.9998The 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
282830.9998The distribution of antibiotic resistance genes in chicken gut microbiota commensals. Antibiotic resistance in bacterial pathogens or several indicator bacteria is commonly studied but the extent of antibiotic resistance in bacterial commensals colonising the intestinal tract is essentially unknown. In this study, we aimed to investigate the presence of horizontally acquired antibiotic resistance genes among chicken gut microbiota members in 259 isolates with known whole genomic sequences. Altogether 124 isolates contained at least one gene coding for antibiotic resistance. Genes coding for the resistance to tetracyclines (detected in 101 isolates), macrolide-lincosamide-streptogramin B antibiotics (28 isolates) and aminoglycosides (25 isolates) were the most common. The most frequent tetracycline resistance genes were tet(W), tet(32), tet(O) and tet(Q). Lachnospiraceae and Ruminococcaceae frequently encoded tet(W). Lachnospiraceae commonly coded also for tet(32) and tet(O). The tet(44) gene was associated with Erysipelotrichaceae and tet(Q) was detected in the genomes of Bacteroidaceae and Porphyromonadaceae. Without any bias we have shown that antibiotic resistance is quite common in gut commensals. However, a comparison of codon usage showed that the above-mentioned families represent the most common current reservoirs but probably not the original host of the detected resistances.202133558560
282140.9998Antibiotic resistant enterococci and staphylococci isolated from flies collected near confined poultry feeding operations. Use of antibiotics as feed additives in poultry production has been linked to the presence of antibiotic resistant bacteria in farm workers, consumer poultry products and the environs of confined poultry operations. There are concerns that these resistant bacteria may be transferred to communities near these operations; however, environmental pathways of exposure are not well documented. We assessed the prevalence of antibiotic resistant enterococci and staphylococci in stored poultry litter and flies collected near broiler chicken houses. Drug resistant enterococci and staphylococci were isolated from flies caught near confined poultry feeding operations in the summer of 2006. Susceptibility testing was conducted on isolates using antibiotics selected on the basis of their importance to human medicine and use in poultry production. Resistant isolates were then screened for genetic determinants of antibiotic resistance. A total of 142 enterococcal isolates and 144 staphylococcal isolates from both fly and poultry litter samples were identified. Resistance genes erm(B), erm(A), msr(C), msr(A/B) and mobile genetic elements associated with the conjugative transposon Tn916, were found in isolates recovered from both poultry litter and flies. Erm(B) was the most common resistance gene in enterococci, while erm(A) was the most common in staphylococci. We report that flies collected near broiler poultry operations may be involved in the spread of drug resistant bacteria from these operations and may increase the potential for human exposure to drug resistant bacteria.200919157515
279750.9998Widespread distribution of tetracycline resistance genes in a confined animal feeding facility. We sought to determine the distribution of resistance and the tetracycline resistance genes among bacteria isolated from a swine confined animal feeding facility where tetracycline-containing feed had been in use for over 20 years. Samples collected from feed, hogs, hog houses, waste lagoon, soil, surface water and well water were screened for the presence of (a) resistant Escherichia coli and enterococci and (b) tetracycline-resistant strains of all species. Genomic DNA was extracted from the latter strain collection and fragments from 16S rDNA and ten tetracycline resistance genes (tetA, tetB, tetC, tetE, tetH, tetL, tetM, tetS, tetT and rumB) were polymerase chain reaction-amplified and a partial nucleotide sequence was obtained. In this environment, 77% of E. coli and 68% of enterococci isolated were tetracycline resistant. Tetracycline resistance was found in 26 different bacterial genera and in 60 species. Single resistance gene alleles (as defined by nucleotide sequence) were present in multiple species. There was evidence of gene recombination and multiple different tetracycline resistance genes were present in single bacterial isolates. These data provide further evidence for the widespread distribution of resistance genes in microbial populations in settings in which there is ongoing subtherapeutic antimicrobial use.200717287111
282060.9998Direct detection of antibiotic resistance genes in specimens of chicken and pork meat. Antibiotic resistance (AR) in bacteria, a major threat to human health, has emerged in the last few decades as a consequence of the selective pressure exerted by the widespread use of antibiotics in medicine, agriculture and veterinary practice and as growth promoters in animal husbandry. The frequency of 11 genes [tet(M), tet(O), tet(K), erm(A), erm(B), erm(C), vanA, vanB, aac (6')-Ie aph (2'')-Ia, mecA, blaZ] encoding resistance to some antibiotics widely used in clinical practice was analysed in raw pork and chicken meat and in fermented sausages as well as in faecal samples from the relevant farm animals using a molecular approach based on PCR amplification of bacterial DNA directly extracted from specimens. Some of the 11 AR genes were highly prevalent, the largest number being detected in chicken meat and pig faeces. The genes found most frequently in meat were tet(K) and erm(B); vanB and mecA were the least represented. All 11 determinants were detected in faecal samples except mecA, which was found only in chicken faeces. erm(B) and erm(C) were detected in all faecal samples. The frequency of AR genes was not appreciably different in meat compared to faecal specimens of the relevant animal except for vanB, which was more prevalent in faeces. Our findings suggest that AR genes are highly prevalent in food-associated bacteria and that AR contamination is likely related to breeding rather than processing techniques. Finally, the cultivation-independent molecular method used in this work to determine the prevalence of AR genes in foods proved to be a rapid and reliable alternative to traditional tools.200717005283
564670.9998Dispersion 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
564380.9998Antibiotic 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
564290.9998Identification 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
2795100.9998Molecular identification and quantification of tetracycline and erythromycin resistance genes in Spanish and Italian retail cheeses. Large antibiotic resistance gene pools in the microbiota of foods may ultimately pose a risk for human health. This study reports the identification and quantification of tetracycline- and erythromycin-resistant populations, resistance genes, and gene diversity in traditional Spanish and Italian cheeses, via culturing, conventional PCR, real-time quantitative PCR (qPCR), and denaturing gradient gel electrophoresis (DGGE). The numbers of resistant bacteria varied widely among the antibiotics and the different cheese varieties; in some cheeses, all the bacterial populations seemed to be resistant. Up to eight antibiotic resistance genes were sought by gene-specific PCR, six with respect to tetracycline, that is, tet(K), tet(L), tet(M), tet(O), tet(S), and tet(W), and two with respect to erythromycin, that is, erm(B) and erm(F). The most common resistance genes in the analysed cheeses were tet(S), tet(W), tet(M), and erm(B). The copy numbers of these genes, as quantified by qPCR, ranged widely between cheeses (from 4.94 to 10.18log10/g). DGGE analysis revealed distinct banding profiles and two polymorphic nucleotide positions for tet(W)-carrying cheeses, though the similarity of the sequences suggests this tet(W) to have a monophyletic origin. Traditional cheeses would therefore appear to act as reservoirs for large numbers of many types of antibiotic resistance determinants.201425302306
2935110.9998Tetracycline Resistance Genes in Wild Birds from a Wildlife Recovery Centre in Central Italy. Wild animals are less likely to be exposed directly to clinical antimicrobial agents than domestic animals or humans, but they can acquire antimicrobial-resistant bacteria through contact with humans, animals, and the environment. In the present study, 254 dead free-living birds belonging to 23 bird species were examined by PCR for the presence of tetracycline resistance (tet) genes. A fragment of the spleen was collected from each bird carcass. A portion of the intestine was also taken from 73 of the 254 carcasses. Extracted DNA was subjected to PCR amplification targeting the tet(L), tet(M), and tet(X) genes. In total, 114 (45%) of the 254 birds sampled belonging to 17 (74%) of the 23 bird species tested were positive for one or more tet genes. The tet(M) gene showed a higher frequency than the other tested genes, both in the spleen and in the intestine samples. These results confirm the potential role of wild birds as reservoirs, dispersers, or bioindicators of antimicrobial resistance in the environment.202236611686
5647120.9998Resistance of bacterial isolates from poultry products to therapeutic veterinary antibiotics. Bacterial isolates from poultry products were tested for their susceptibility to 10 antibiotics commonly used in the therapeutic treatment of poultry. Bacteria were isolated from fresh whole broiler carcasses or from cut-up meat samples (breast with or without skin, wings, and thighs) that were either fresh or stored at 4 or 13 degrees C (temperatures relevant to poultry-processing facilities). The Biolog system was used to identify isolates, and a broth dilution method was used to determine the antibiotic resistance properties of both these isolates and complementary cultures from the American Type Culture Collection. The antibiotics to which the most resistance was noted were penicillin G, sulfadimethoxine, and erythromycin; the antibiotic to which the least resistance was noted was enrofloxacin. Individual isolates exhibited resistances to as many as six antibiotics, with the most common resistance pattern involving the resistance of gram-negative bacteria to penicillin G, sulfadimethoxine, and erythromycin. Differences in resistance patterns were noted among 18 gram-positive and 7 gram-negative bacteria, and comparisons were made between species within the same genus. The data obtained in this study provide a useful reference for the species and resistance properties of bacteria found on various raw poultry products, either fresh or stored at temperatures and for times relevant to commercial processing, storage, and distribution. The results of this study show that resistance to antibiotics used for the therapeutic treatment of poultry occurs in bacteria in the processing environment.200312540187
2905130.9997Scarce detection of mobile erm genes associated with tetQ in Bacteroides and Parabacteroides from Costa Rica. The frequency of finding of clindamycin-resistant anaerobic bacteria in clinical samples has doubled from 2008 to 2010 in Costa Rica. To determine whether this increase is due to dissemination of erm genes aided by tetQ elements, we analyzed 100 isolates of Bacteroides or Parabacteroides from a regional hospital, a national hospital, and the community. Antimicrobial susceptibilities were recorded with a broth micro-dilution method and erm genes were detected by PCR and Southern blotting. In addition, plasmid isolation and mating experiments were performed to clarify the location and mobility of the detected erm genes. Resistance to clindamycin was by far more frequent in the regional hospital (72%) than in the national hospital (29%) and the community (26%). Resistance to tetracycline was even more common, with the community (85%) outweighing the hospitals (71-72%). While MIC of clindamycin were higher in the hospitals than in the community (P < 0.05), the opposite was seen for tetracycline (P < 0.0001). Of the sought-after genes, only ermG (n = 2), ermA (n = 1), and ermF (n = 1) were detected in the hospitals and ermF in the community (n = 2). In opposition to the low frequency of finding of erm genes, 71% of the isolates were positive for tetQ. None of the detected genes were encoded on plasmids. Only three isolates from the hospitals transferred their erm genes laterally. By contrast, 13 hospital isolates and two community isolates transferred tetQ. Despite the widespread finding of tetracycline-resistant tetQ-positive bacteria, mobile erm genes were rare in our bacterial collection. We conclude that the detected erm genes are likely not included in typical conjugative transposons of Bacteroides and Parabacteroides.201323528984
5935140.9997Antibiotic resistance genes in anaerobic bacteria isolated from primary dental root canal infections. Fourty-one bacterial strains isolated from infected dental root canals and identified by 16S rRNA gene sequence were screened for the presence of 14 genes encoding resistance to beta-lactams, tetracycline and macrolides. Thirteen isolates (32%) were positive for at least one of the target antibiotic resistance genes. These strains carrying at least one antibiotic resistance gene belonged to 11 of the 26 (42%) infected root canals sampled. Two of these positive cases had two strains carrying resistance genes. Six out of 7 Fusobacterium strains harbored at least one of the target resistance genes. One Dialister invisus strain was positive for 3 resistance genes, and 4 other strains carried two of the target genes. Of the 6 antibiotic resistance genes detected in root canal strains, the most prevalent were blaTEM (17% of the strains), tetW (10%), and ermC (10%). Some as-yet-uncharacterized Fusobacterium and Prevotella isolates were positive for blaTEM, cfxA and tetM. Findings demonstrated that an unexpectedly large proportion of dental root canal isolates, including as-yet-uncharacterized strains previously regarded as uncultivated phylotypes, can carry antibiotic resistance genes.201223108290
2896150.9997Resistance gene patterns of tetracycline resistant Escherichia coli of human and porcine origin. Resistance transfer from animals to humans (and vice versa) is a frequently discussed topic in human and veterinary medicine, albeit relevant studies focus mainly on phenotypic antibiotic resistance. In order to get a comparative insight regarding the distribution of selected resistance genes [tet(A/B/C/D/M/K/L/O/S/W/Z), sulI, II, III, str(A/B), aad(A)] in Escherichia coli of different origins, phenotypically tetracycline resistant isolates of porcine and human origin (n=137 and 152) were investigated using PCR. The most common gene was tet(A) in porcine, but tet(B) in human isolates (>55%). Tet(C/M/D) were rare (1-7%); tet(K/L/O/S/W/Z) were not detected. Co-occurrence of tet(A) and tet(B) was more frequent in human strains (11% vs. 2%). 88% of the porcine isolates had one, and 9% had two tet-genes. By contrast, only 69% of the human strains had one tet-gene, whereas 17% were carriers of two tet-determinants. The most common sulfonamide resistance gene was represented by sulII (40% in porcine, 62% in human isolates), followed by sulI. SulIII was present in eight isolates. Streptomycin resistance was mostly mediated by str(A)/str(B) in porcine, and by str(A)/str(B)/aad(A) in human strains (35% each). In one E. coli of human origin, 7 resistance genes were simultaneously detected. Co-occurrence of 5 or 6 resistance genes was more present in human strains, whereas porcine isolates carried more often only 1-4 genes. The huge diversities between gene patterns of bacteria of human and porcine origin indicate that genetic transfers between microorganisms from different sources are less frequent than transfers within populations of the same source.201019939589
5538160.9997Phenotypic 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
5596170.9997Enterotoxigenicity and Antibiotic Resistance of Coagulase-Negative Staphylococci Isolated from Raw Buffalo and Cow Milk. Staphylococcal food poisoning is considered to be one of the most common foodborne illnesses worldwide. Because milk is rich in nutrients and its neutral pH, it leads to the growth of various bacteria. To date, the correlation between enterotoxigenic potential in Staphylococcus species and antimicrobial resistance (AMR), using bioinformatics analysis in buffalo and cow raw milk and the possible health risks from these bacteria, has not been examined in Egypt. A total of 42 Staphylococcus isolates representing 12 coagulase-positive staphylococci (Staphylococcus aureus and Staphylococcus intermedius) and 30 coagulase-negative staphylococci (Staphylococcus capitis, Staphylococcus xylosus, Staphylococcus carnosus, Staphylococcus saccharolyticus, and Staphylococcus auricularis) were isolated. An assay of the antimicrobial resistance phenotypes indicated low resistance against vancomycin (9.5%). The blaZ gene was associated with penicillin G and methicillin resistance and not with sulbactam + ampicillin. The presence of the gene ermB presented the correlation with erythromycin resistance and tetK with tetracycline resistance (correlation index: 0.57 and 0.49, respectively), despite the absence of the same behavior for ermC and tetM, respectively. Interestingly, the gene mecA was not correlated with resistance to methicillin or any other β-lactam. Correlation showed that slime-producing isolates had more resistance to antibiotics than those of nonslime producers. The multiple correlations between antibiotic resistance phenotypes and resistance genes indicate a complex nature of resistance in Staphylococcus species. The antimicrobial resistance could potentially spread to the community and thus, the resistance of Staphylococcus species to various antibiotics does not depend only on the use of a single antimicrobial, but also extends to other unrelated classes of antimicrobials.202031750778
2904180.9997The maintenance in the oral cavity of children of tetracycline-resistant bacteria and the genes encoding such resistance. OBJECTIVES: To investigate the maintenance of tetracycline-resistant oral bacteria and the genes encoding tetracycline resistance in these bacteria in children (aged 4--6 years) over a period of 12 months. METHODS: Plaque and saliva samples were taken from 26 children. Tetracycline-resistant bacteria were isolated and identified. The types of resistance genes and their genetic locations were also determined. RESULTS: Fifteen out of 18 children harboured tetracycline-resistant (defined as having a MIC>or=8 mg/L) oral bacteria at all three time points. The median percentage of tetracycline-resistant bacteria at 0, 6 and 12 months was 1.37, 1.37 and 0.85%, respectively; these were not significantly different. The MIC(50) of the group was 64 mg/L at all three time points compared with the MIC(90), which was 64 mg/L at 0 months, and 128 mg/L at 6 and 12 months. The most prevalent resistant species were streptococci (68%), which were isolated at all three time points in 13 children. The most prevalent gene encoding tetracycline resistance was tet(M) and this was found in different species at all three time points. For the first time, tet(32) was found in Streptococcus parasanguinis and Eubacterium saburreum. PCR and Southern-blot analysis (on isolates from three of the children) showed that the tet(M) gene was located on a Tn916-like element and could be detected at all three time points, in four different genera, Streptococcus, Granulicatella, Veillonella and Neisseria. CONCLUSIONS: The results of this study show that tetracycline-resistant bacteria and tet(M) are maintained within the indigenous oral microbiota of children, even though they are unlikely to have been directly exposed to tetracycline.200516027144
2799190.9997Genetic and physiological characterization of oxytetracycline-resistant bacteria from giant prawn farms. Four hundred and thirteen oxytetracycline-resistant bacteria were recovered from six freshwater giant prawn farms with a history of oxytetracycline use. Most oxytetracyclineresistant isolates were Gram-negative bacteria. Six groups of oxytetracycline-resistant bacteria were classified using cluster analysis based on a comparison of levels of oxytetracycline resistance. Complex fingerprint patterns were obtained for 71 isolates studied. In general, the band patterns of isolates from different ponds were very similar, and the data indicated that the isolates were closely related. The exploration for crossresistance found that most of the 71 oxytetracycline-resistant isolates were also resistant to tetracycline and chlortetracycline, but had a relatively low resistance to doxycycline. Many isolates showed higher chlortetracycline resistance than oxytetracycline resistance. Additionally, the oxytetracyclineresistant isolates were examined for the presence of tetracycline resistance (tet) genes. Fifty percent of the isolates carried one of the 14 known tet genes examined. The most common determinants were TetA and TetD. However, TetB, TetC, TetE, TetK, TetL, and TetM were also found with various frequencies.200818309262