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216900.9872E-test antibiotics susceptibility of strict anaerobic bacteria. The E-test is convenient for testing susceptibility of anaerobes. From September 1998 to September 1999, 194 strains (105 Gram-positive bacteria, 89 Gram-negative bacteria) of clinically relevant samples were tested against five antibiotics benzylpenicillin, amoxicillin-clavulanic acid, clindamycin, metronidazole and imipenem on blood agar plates. Resistance to benzyl penicillin is widespread and Gram-negative bacteria and resistance to amoxicillin-clavulanic acid is exceptional. Metronidazole is very effective against anaerobes except non-spore-forming aerotolerant Gram-positive rods and Peptostreptococcus micros.200316887712
125610.9864Prevalence of antimicrobial resistant genes in Bacteroides spp. isolated in Oita Prefecture, Japan. INTRODUCTION: Bacteroides spp. are the most common anaerobic bacteria isolated from the human gastrointestinal tract. Several resistant genes are present in Bacteroides spp. However, most studies have focused on the prevalence of the cfiA gene in Bacteroides fragilis alone. We assessed the susceptibility to antimicrobial agents and the prevalence of cepA, cfiA, cfxA, ermF, nim, and tetQ genes in Bacteroides strains isolated from clinical specimens in our hospital. METHODS: We isolated 86 B. fragilis and 58 non-fragilis Bacteroides strains from human clinical specimens collected from January 2011 to November 2021. Resistance against piperacillin (PIPC), cefotaxime (CTX), cefepime (CFPM), meropenem (MEPM), clindamycin, and minocycline was determined. RESULTS: The resistant rates of penicillins and cephalosporins in non-fragilis isolates were significantly higher than those in B. fragilis isolates. In B. fragilis isolates, the resistant rates of PIPC, CTX, and CFPM in cfxA-positive isolates were significantly higher than those in cfxA-negative isolates (71% vs. 16%, 77% vs. 19%, and 77% vs. 30%, respectively). Thirteen B. fragilis isolates harbored the cfiA gene, two of which were resistant to MEPM. Six of the 13 cfiA-positive B. fragilis isolates were heterogeneously resistant to MEPM. CONCLUSION: It is important to evaluate the use of MEPM as empirical therapy for Bacteroides spp. infections, considering the emergence of carbapenem resistance during treatment, existence of MEPM-resistant strains, and heterogeneous resistance.202336473684
542620.9864First Report of Antibiotic Resistance Markers cfiA and nim Among Bacteroides fragilis Group Strains in Ecuadorian Patients. In recent years, increasing resistance of Bacteroides fragilis to several antibiotics has been reported in different countries. The aim of this study was to evaluate the antibiotic resistance profiles of Bacteroides spp. isolated from clinical samples by phenotypic and molecular methods. A total of 40 nonrepetitive isolates of the B. fragilis group were studied from 2018 to 2019. The species was identified by API 20A system. The minimum inhibitory concentrations (MICs) were determined by Sensititre anaerobe MIC plate. The presence of the nim and cfiA genes was checked by conventional PCR. The association between genes and insertion sequence (IS) was performed by whole genome sequencing. Eleven isolates were categorized as metronidazole-resistant and only 2 isolates harbored the nim gene. Five isolates were imipenem-resistant, but cfiA gene was detected in two isolates. cfiA gene was closely related to the cfiA-4 allele and associated with IS614B. The nim gene was not related to any nim gene type and was considered a new variant named nimL. IS612 was found upstream of nimL gene. In view of the scarcity of data on B. fragilis, there is a need to surveil antibiotic resistance levels and molecular mechanisms to implement better antimicrobial therapies against this important group of bacteria.202337733248
538730.9864Assessment of antibiotic susceptibility within lactic acid bacteria strains isolated from wine. Susceptibility to 12 antibiotics was tested in 75 unrelated lactic acid bacteria strains of wine origin of the following species: 38 Lactobacillus plantarum, 3 Lactobacillus hilgardii, 2 Lactobacillus paracasei, 1 Lactobacillus sp, 21 Oenococcus oeni, 4 Pediococcus pentosaceus, 2 Pediococcus parvulus, 1 Pediococcus acidilactici, and 3 Leuconostoc mesenteroides. The Minimal Inhibitory Concentrations of the different antibiotics that inhibited 50% of the strains of the Lactobacillus, Leuconostoc and Pediococcus genera were, respectively, the following ones: penicillin (2, < or =0.5, and < or =0.5 microg/ml), erythromycin (< or =0.5 microg/ml), chloramphenicol (4 microg/ml), ciprofloxacin (64, 8, and 128 microg/ml), vancomycin (> or =128 microg/ml), tetracycline (8, 2, and 8 microg/ml), streptomycin (256, 32, and 512 microg/ml), gentamicin (64, 4, and 128 microg/ml), kanamycin (256, 64, and 512 microg/ml), sulfamethoxazole (> or =1024 microg/ml), and trimethoprim (16 microg/ml). All 21 O. oeni showed susceptibility to erythromycin, tetracycline, rifampicin and chloramphenicol, and exhibited resistance to aminoglycosides, vancomycin, sulfamethoxazole and trimethoprim, that could represent intrinsic resistance. Differences were observed among the O. oeni strains with respect to penicillin or ciprofloxacin susceptibility. Antibiotic resistance genes were studied by PCR and sequencing, and the following genes were detected: erm(B) (one P. acidilactici), tet(M) (one L. plantarum), tet(L) (one P. parvulus), aac(6')-aph(2") (four L. plantarum, one P. parvulus, one P. pentosaceus and two O. oeni), ant(6) (one L. plantarum, and two P. parvulus), and aph(3')-IIIa (one L. plantarum and one O. oeni). This is the first time, to our knowledge, that ant(6), aph(3')-IIIa and tet(L) genes are found in Lactobacillus and Pediococcus strains and antimicrobial resistance genes are reported in O. oeni strains.200616876896
129740.9862Antimicrobial resistance, prevalence of resistance genes, and molecular characterization in intestinal Bacteroides fragilis group isolates. Since the level of antimicrobial resistance in Bacteroides fragilis has increased, monitoring the antimicrobial susceptibility could be necessary. The objectives of this study were to (i) investigate the prevalence of species, the occurrence of reduced antimicrobial susceptibility (E-test method), and antibiotic resistance genes in the B. fragilis group and (ii) evaluate the prevalence of enterotoxigenic B. fragilis and the distribution of bft gene subtypes in hospitalized patients. As many as 475 isolates out of 250 stool samples were detected to be B. fragilis group by using conventional biochemical tests (API-32A system) and multiplex-PCR. In addition, 48.2%, 13.9%, 76.6%, and 1.2% of B. fragilis group isolates were resistant (according to EUCAST breakpoint) to piperacillin-tazobactam, meropenem, clindamycin, and metronidazole, respectively. Six metronidazole-resistant strains were isolated; B. fragilis (n: 3), B. thetaiotaomicron, B. vulgates, and B. ovatus. The presence of the cfiA, cepA, ermF, and nim genes was observed in 3.8%, 15.9%, 34.1%, and 0.7% of the B. fragilis isolates, respectively. One hundred thirty-two B. fragilis isolates (27.8%)and 21 B  fragilis isolates (15.9%) turned out to be bft gene positive by multiplex-PCR; eleven isolates (52.4%) harbored bft-1, eight isolates (38%) harbored bft-2 isotypes, and two isolates (9.5%) harbored bft-3 isotype (16.66%). These bacteria harbor antimicrobial resistance genes that could be transferred to other susceptible intestinal strains. Further investigations on lineage analysis are needed for a better understanding of these bacteria in Iran.201930803024
544850.9862Virulence gene profiles, biofilm formation, and antimicrobial resistance of Vibrio cholerae non-O1/non-O139 bacteria isolated from West Bengal, India. Vibrio cholerae is the causative agent of acute dehydrating diarrhoeal disease cholera. Among 71 V. cholerae non-O1/non-O139 isolates, all yielded negative results for ctxA, ctxB and tcpA genes in PCR assay. Few strains were positive for stn (28.38%), and ompU (31.08%) genes. While all isolates were negative for ace gene, only two were positive for zot gene. All strains expressed toxR and toxT genes. It was also found that all isolates were slime-producer and these were capable of forming moderate to high biofilm. Biofilm formation was controlled positively by the transcriptional regulators VpsR and VpsT and was regulated negatively by HapR, as well as CRP regulatory complex. These isolates were resistant to ampicillin, furazolidone, doxycycline, vancomycin, erythromycin, while these were susceptible to ciprofloxacin, gentamycin, kanamycin, polymixin B, norfloxacin, chloramphenicol, sulphamethoxazole-trimethoprim, tetracycline, nalidixic acid, and streptomycin. Indeed, 69.01% isolates were resistant to multiple antibiotics (MAR: resistance to 3 or more antibiotics). Treatment protocols for cholera patients should be based on local antibiogram data.201830582054
244360.9861Antibiotic Resistance among Fusobacterium, Capnocytophaga, and Leptotrichia Species of the Oral Cavity. PURPOSE: Antibiotics play an important role in treating periodontal diseases. Due to the effectiveness of antibiotic therapies, their usage in dentistry has significantly increased. The aim of this study focused on the in-vitro susceptibility of different gram-negative oral bacteria species - which are associated with periodontal diseases (Fusobacterium spp., Capnocytophaga spp. and Leptotrichia buccalis) and have different geographical origins (Asia and Europe) - against antimicrobials that are clinically relevant in dental therapy. MATERIALS AND METHODS: A total of 45 strains were tested (29 Fusobacterium spp., 13 Capnocytophaga spp. and 3 L. buccalis) that were either isolated from Chinese patients or were obtained from different strain collections. Their antimicrobial susceptibility to the antimicrobial agents benzylpenicillin, amoxicillin, amoxicillin-clavulanic acid, ciprofloxacin, moxifloxacin, clindamycin, doxycycline, tetracycline and metronidazole was tested using the E-Test. Strains with particular resistance to penicillin, clindamycin and metronidazole were further analysed for resistance genes. RESULTS: All tested bacterial isolates were sensitive to amoxicillin, amoxicillin-clavulanic acid, doxycycline and tetracycline, but showed variable sensitivity towards other antibiotics such as benzylpenicillin, ciprofloxacin, moxifloxacin, clindamycin and metronidazole. CONCLUSION: The results of the present study suggest that certain periodontal disease-related bacterial strains can be resistant towards antimicrobial agents commonly used in adjuvant periodontal therapy.202337014213
542770.9861PCR-based detection of resistance genes in anaerobic bacteria isolated from intra-abdominal infections. Little information is available on the distribution of antimicrobial resistance genes in anaerobes in Japan. To understand the background of antimicrobial resistance in anaerobes involved in intra-abdominal infections, we investigated the distribution of eight antimicrobial resistance genes (cepA, cfiA, cfxA, ermF, ermB, mefA, tetQ, and nim) and a mutation in the gyrA gene in a total of 152 organisms (Bacteroides spp., Prevotella spp., Fusobacterium spp., Porphyromonas spp., Bilophila wadsworthia, Desulfovibrio desulfuricans, Veillonella spp., gram-positive cocci, and non-spore-forming gram-positive bacilli) isolated between 2003 and 2004 in Japan. The cepA gene was distributed primarily in Bacteroides fragilis. Gene cfxA was detected in about 9 % of the Bacteroides isolates and 75 % of the Prevotella spp. isolates and did not appear to contribute to cephamycin resistance. Two strains of B. fragilis contained the metallo-β-lactamase gene cfiA, but they did not produce the protein product. Gene tetQ was detected in about 81, 44, and 63 % of B. fragilis isolates, other Bacteroides spp., and Prevotella spp. isolates, respectively. The ermF gene was detected in 25, 13, 56, 64, and 16 % of Bacteroides spp., Prevotella spp., Fusobacterium spp., B. wadsworthia, and anaerobic cocci, respectively. Gene mefA was found in only 10 % of the B. fragilis strains and 3 % of the non-B. fragilis strains. Genes nim and ermB were not detected in any isolate. Substitution at position 82 (Ser to Phe) in gyrA was detected in B. fragilis isolates that were less susceptible or resistant to moxifloxacin. This study is the first report on the distribution of resistance genes in anaerobes isolated from intra-abdominal infections in Japan. We expect that the results might help in understanding the resistance mechanisms of specific anaerobes.201323338012
541280.9859Molecular basis of resistance to macrolides and other antibiotics in commensal viridans group streptococci and Gemella spp. and transfer of resistance genes to Streptococcus pneumoniae. We assessed the mechanisms of resistance to macrolide-lincosamide-streptogramin B (MLS(B)) antibiotics and related antibiotics in erythromycin-resistant viridans group streptococci (n = 164) and Gemella spp. (n = 28). The macrolide resistance phenotype was predominant (59.38%); all isolates with this phenotype carried the mef(A) or mef(E) gene, with mef(E) being predominant (95.36%). The erm(B) gene was always detected in strains with constitutive and inducible MLS(B) resistance and was combined with the mef(A/E) gene in 47.44% of isolates. None of the isolates carried the erm(A) subclass erm(TR), erm(A), or erm(C) genes. The mel gene was detected in all but four strains carrying the mef(A/E) gene. The tet(M) gene was found in 86.90% of tetracycline-resistant isolates and was strongly associated with the presence of the erm(B) gene. The cat(pC194) gene was detected in seven chloramphenicol-resistant Streptococcus mitis isolates, and the aph(3')-III gene was detected in four viridans group streptococcal isolates with high-level kanamycin resistance. The intTn gene was found in all isolates with the erm(B), tet(M), aph(3')-III, and cat(pC194) gene. The mef(E) and mel genes were successfully transferred from both groups of bacteria to Streptococcus pneumoniae R6 by transformation. Viridans group streptococci and Gemella spp. seem to be important reservoirs of resistance genes.200415328112
544690.9859Antimicrobial sensitivity trends and virulence genes in Shigella spp. from the Oceania region. Shigella is a common cause of diarrhoea in Papua New Guinea (PNG) and other Oceania countries. However, little is known about the strains causing infection. Archived Shigella isolates (n = 72) were obtained from research laboratories in PNG and reference laboratories in Australia. Shigella virulence genes were detected by PCR, and antimicrobial susceptibility was determined by disk diffusion. The ipaH virulence gene was present in all 72 isolates. The prevalence of other virulence genes was variable, with ial, invE, ipaBCD, sen/ospD3 and virF present in 60% of isolates and set1A and set1B genes present in 42% of isolates. Most S. flexneri isolates contained genes encoding enterotoxin 1 and/or enterotoxin 2. Resistance to antibiotics was common, with 51/72 isolates resistant to 2-4 antimicrobials. A greater proportion of bacteria isolated since 2010 (relative to pre-2010 isolates) were resistant to commonly used antibiotics such as ampicillin, chloramphenicol, tetracycline, and trimethoprim-sulfamethoxazole; suggesting that antimicrobial resistance (AMR) in Shigella is increasing over time in the Oceania region. There is a need for improved knowledge regarding Shigella circulation in the Oceania region and further monitoring of AMR patterns.201829906636
5429100.9858Antibiotic resistance pattern of Bacteroides fragilis isolated from clinical and colorectal specimens. BACKGROUND: Bacteroides fragilis is a part of the normal gastrointestinal flora, but it is also the most common anaerobic bacteria causing the infection. It is highly resistant to antibiotics and contains abundant antibiotic resistance mechanisms. METHODS: The antibiotic resistance pattern of 78 isolates of B. fragilis (22 strains from clinical samples and 56 strains from the colorectal tissue) was investigated using agar dilution method. The gene encoding Bacteroides fargilis toxin bft, and antibiotic resistance genes were targeted by PCR assay. RESULTS: The highest rate of resistance was observed for penicillin G (100%) followed by tetracycline (74.4%), clindamycin (41%) and cefoxitin (38.5%). Only a single isolate showed resistance to imipenem which contained cfiA and IS1186 genes. All isolates were susceptible to metronidazole. Accordingly, tetQ (87.2%), cepA (73.1%) and ermF (64.1%) were the most abundant antibiotic-resistant genes identified in this study. MIC values for penicillin, cefoxitin and clindamycin were significantly different among isolates with the cepA, cfxA and ermF in compare with those lacking such genes. In addition, 22.7 and 17.8% of clinical and GIT isolates had the bft gene, respectively. CONCLUSIONS: The finding of this study shows that metronidazole is highly in vitro active agent against all of B. fragilis isolates and remain the first-line antimicrobial for empirical therapy.202133892721
5433110.9858Diversity of antimicrobial resistance genes in Bacteroides and Parabacteroides strains isolated in Germany. OBJECTIVES: Bacteroides spp. are normal constituents of the human intestinal microflora, but they are also able to cause severe diseases. The aim of this study was to determine the diversity of antibiotic resistance genes found in phenotypically resistant Bacteroides and Parabacteroides strains. METHODS: A total of 71 phenotypically resistant Bacteroides spp. from human clinical specimens were screened for the antibiotic resistance genes cfiA, tetQ, tetM, tet36, cepA, cfxA, nim, ermG, ermF, bexA, bla(VIM), bla(NDM), bla(KPC), bla(OXA-48) and bla(GES). The presence of these genes was compared with phenotypic resistance to ampicillin/sulbactam, cefoxitin, ceftolozane/tazobactam, piperacillin/tazobactam, imipenem, meropenem, meropenem/vaborbactam, clindamycin, moxifloxacin, tigecycline, eravacycline and metronidazole. RESULTS: tetQ was the most frequently detected gene, followed by cfiA, ermF, cfxA, ermG, cepA, nim and bexA. None of the strains were positive for tetM, tet36, bla(VIM), bla(NDM), bla(KPC), bla(OXA-48) or bla(GES). Resistance to the tested β-lactams was mainly linked to the presence of the cfiA gene. Clindamycin resistance correlated with the presence of the genes ermG and ermF. The bexA gene was found in six strains, but only two of them were resistant to moxifloxacin. Tigecycline and eravacycline showed good activities despite the frequent occurrence of tetQ. The nim gene was detected in six isolates, five of which were resistant to metronidazole. CONCLUSION: The findings of our study support the general belief that antimicrobial resistance within Bacteroides should be taken into consideration. This underlines the necessity of reliable routine antimicrobial susceptibility test methods for anaerobic bacteria and the implementation of antimicrobial surveillance programmes worldwide.202133508481
2337120.9856Klebsiella pneumoniae susceptibility to biocides and its association with cepA, qacΔE and qacE efflux pump genes and antibiotic resistance. BACKGROUND: Although antiseptics are some of the most widely used antibacterials in hospitals, there is very little information on reduced susceptibility to these biocides and its relationship with resistance to antibiotics. AIM: To determine the relationship between reduced susceptibility to biocides and the carriage of antiseptic resistance genes, cepA, qacΔE and qacE, as well as identifying the role of efflux pumps in conferring reduced susceptibility. METHODS: Susceptibility was assessed for five biocides: chlorhexidine, benzalkonium chloride, Trigene, MediHex-4, Mediscrub; and for 11 antibiotics against 64 isolates of Klebsiella pneumoniae. Susceptibility to all compounds was tested by the agar double dilution method (DDM) and the effect of efflux pumps on biocides determined by repeating the susceptibility studies in the presence of the efflux pump inhibitor carbonyl cyanide m-chlorophenyl hydrazone (CCCP). The presence of the cepA, qacΔE and qacE genes was identified by polymerase chain reaction. FINDINGS: The bacteria were not widely antibiotic resistant though a few showed reduced susceptibility to cefoxitin, chloramphenicol and rifampicin and later-generation cephalosporins but not to carbapenems. Biocide susceptibility, tested by DDM, showed that 50, 49 and 53 strains had reduced susceptibility to chlorhexidine, Trigene and benzalkonium chloride, respectively. The antiseptic resistance genes cepA, qacΔE and qacE were found in 56, 34 and one isolates respectively and their effects as efflux pumps were determined by CCCP (10 mg/L), which decreased the minimum inhibitory concentrations (MICs) of chlorhexidine and Medihex-4 by 2-128-fold but had no impact on the MICs of benzalkonium chloride, Trigene and Mediscrub. CONCLUSION: There was a close link between carriage of efflux pump genes, cepA, qacΔE and qacE genes and reduced biocide susceptibility, but not antibiotic resistance, in K. pneumoniae clinical isolates.201222498639
1227130.9856Antibiotic resistance among coliform bacteria isolated from carcasses of commercially slaughtered chickens. A total of 322 coliform bacteria Escherichia coli, Enterobacter spp., Citrobacter spp., Klebsiella spp. and Serratia spp., were isolated from 50 carcasses of commercially slaughtered chickens. Their resistance to ampicillin, tetracycline, gentamicin, chloramphenicol, cephalotine, cotrimoxazole, nalidixic acid and nitrofurantoin, were determined. The most commonly found resistance was to tetracycline followed by cephalotine, cotrimoxazole and nalidixic acid. A large percentage of E. coli (41%) and Klebsiella spp. (38%) showed multiple antibiotic resistance.19902282290
1260140.9856Isolation, Identification, and Antimicrobial Susceptibilities of Bacteria from the Conjunctival Sacs of Dogs with Bacterial Conjunctivitis in Different Regions of Wuhan, China. In order to investigate the bacterial species present in the conjunctival sacs of dogs with bacterial conjunctivitis in Wuhan (Hongshan District, Wuchang District, Jiangxia District, and Huangpi District) and their resistance to aminoglycoside antibiotics, samples of conjunctival sac secretions were collected from 56 dogs with bacterial conjunctivitis in various regions of Wuhan. Drug susceptibility testing for aminoglycoside antibiotics was performed on the most commonly isolated gram-positive and gram-negative bacteria. The expression of two aminoglycoside modifying enzyme genes, aacA-aphD and aac (6')-Ib, and three 16S rRNA methyltransferase genes, rmtB, rmtE and npmA, were analyzed by PCR. The results showed that a total of 123 bacterial strains were cultured from 56 conjunctival sac secretion samples, with Staphylococcus being the most commonly isolated species, followed by Escherichia. Among them, 14 strains of Staphylococcus pseudointermedius were not resistant to tobramycin, amikacin, gentamicin or neomycin, but the resistance rates to streptomycin and kanamycin were 35.71% and 42.86%, respectively. Among them, 14 Escherichia coli strains were not resistant to tobramycin and gentamicin, but they showed high resistance rates to neomycin and kanamycin (both at 50%). The detection rate of the aacA-aphD gene in Staphylococcus pseudointermedius strains was 100%. The detection rates of the rmtB gene and rmtE gene in Escherichia coli were 85.71% and 28.57%, respectively, while the aac(6')-Ib gene and npmA gene were not detected.202539852896
5428150.9855Antimicrobial resistance and prevalence of resistance genes of obligate anaerobes isolated from periodontal abscesses. BACKGROUND: This study attempts to determine the antimicrobial resistance profiles of obligate anaerobic bacteria that were isolated from a periodontal abscess and to evaluate the prevalence of resistance genes in these bacteria. METHODS: Forty-one periodontal abscess samples were cultivated on selective and non-selective culture media to isolate the oral anaerobes. Their antibiotic susceptibilities to clindamycin, doxycycline, amoxicillin, imipenem, cefradine, cefixime, roxithromycin, and metronidazole were determined using the agar dilution method, and polymerase chain reaction assays were performed to detect the presence of the ermF, tetQ, nim, and cfxA drug resistance genes. RESULTS: A total of 60 different bacterial colonies was isolated and identified. All of the isolates were sensitive to imipenem. Of the strains, 6.7%, 13.3%, 16.7%, and 25% were resistant to doxycycline, metronidazole, cefixime, and amoxicillin, respectively. The resistance rate for both clindamycin and roxithromycin was 31.7%. Approximately 60.7% of the strains had the ermF gene, and 53.3% of the amoxicillin-resistant strains were found to have the cfxA gene. Two nim genes that were found in eight metronidazole-resistant strains were identified as nimB. CONCLUSIONS: In the present study, the Prevotella species are the most frequently isolated obligate anaerobes from periodontal abscesses. The current results show their alarmingly high resistance rate against clindamycin and roxithromycin; thus, the use of these antibiotics is unacceptable for the empirical therapy of periodontal abscesses. A brief prevalence of four resistance genes in the anaerobic bacteria that were isolated was also demonstrated.201423659425
5386160.9855Antibiotic resistance of lactic acid bacteria isolated from Chinese yogurts. The aim of this study was to evaluate the susceptibility of 43 strains of lactic acid bacteria, isolated from Chinese yogurts made in different geographical areas, to 11 antibiotics (ampicillin, penicillin G, roxithromycin, chloramphenicol, tetracycline, chlortetracycline, lincomycin, kanamycin, streptomycin, neomycin, and gentamycin). The 43 isolates (18 Lactobacillus bulgaricus and 25 Streptococcus thermophilus) were identified at species level and were typed by random amplified polymorphic DNA analysis. Thirty-five genotypically different strains were detected and their antimicrobial resistance to 11 antibiotics was determined using the agar dilution method. Widespread resistance to ampicillin, chloramphenicol, chlortetracycline, tetracyclines, lincomycin, streptomycin, neomycin, and gentamycin was found among the 35 strains tested. All of the Strep. thermophilus strains tested were susceptible to penicillin G and roxithromycin, whereas 23.5 and 64.7% of Lb. bulgaricus strains, respectively, were resistant. All of the Strep. thermophilus and Lb. bulgaricus strains were found to be resistant to kanamycin. The presence of the corresponding resistance genes in the resistant isolates was investigated through PCR, with the following genes detected: tet(M) in 1 Lb. bulgaricus and 2 Strep. thermophilus isolates, ant(6) in 2 Lb. bulgaricus and 2 Strep. thermophilus isolates, and aph(3')-IIIa in 5 Lb. bulgaricus and 2 Strep. thermophilus isolates. The main threat associated with these bacteria is that they may transfer resistance genes to pathogenic bacteria, which has been a major cause of concern to human and animal health. To our knowledge, the aph(3')-IIIa and ant(6) genes were found in Lb. bulgaricus and Strep. thermophilus for the first time. Further investigations are required to analyze whether the genes identified in Lb. bulgaricus and Strep. thermophilus isolates might be horizontally transferred to other species.201222916881
5940170.9855In vitro activities of spectinomycin and comparator agents against Pasteurella multocida and Mannheimia haemolytica from respiratory tract infections of cattle. OBJECTIVES: Prior to the renewal of spectinomycin licensing for veterinary uses in Germany, 154 Pasteurella multocida and 148 Mannheimia haemolytica strains from respiratory tract infections in cattle were investigated for their MICs of spectinomycin and other antimicrobial agents. The data obtained should serve as a baseline from which to judge the future development of resistance. Moreover, the in vitro activity of spectinomycin in comparison with other antimicrobials should be assessed. METHODS: MIC determination for all 302 strains was performed by the broth dilution method and evaluated according to NCCLS standards. MIC(50) and MIC(90) values were calculated. Strains resistant to spectinomycin were subjected to PCR assays for genes known to mediate spectinomycin resistance in Gram-negative and Gram-positive bacteria. RESULTS: With the exception of resistance to sulfamethoxazole in P. multocida and M. haemolytica, and resistance to ampicillin in M. haemolytica, an overall low level of resistance was detected. A total of 93.5% of the P. multocida and 98.6% of the M. haemolytica strains were susceptible to spectinomycin, with MIC(90)s of 32 mg/L. PCR analysis showed that none of the spectinomycin-resistant strains carried any of the aadA gene subtypes, nor the genes spc or aad(9). CONCLUSIONS: Prior to the renewal of spectinomycin, only a small number of spectinomycin-resistant strains was detected among bovine P. multocida and M. haemolytica. The genes responsible for spectinomycin resistance in these strains seemed to be different from those so far known to occur in other Gram-negative and Gram-positive bacteria.200414729757
5227180.9854Mutation at the position 2058 of the 23S rRNA as a cause of macrolide resistance in Streptococcus pyogenes. BACKGROUND: In streptococci, three macrolide resistance determinants (erm(B), erm(TR) and mef(A)) have been found. In addition, certain mutations at the ribosomal 23S RNA can cause resistance to macrolides. Mutation at the position 2058 of the 23S rRNA of the Streptococcus pyogenes as a cause of macrolide resistance has not been described before. METHODS: Antibiotic resistance determinations for the clinical S. pyogenes strain ni4277 were done using the agar dilution technique. Macrolide resistance mechanisms were studied by PCR and sequencing. All six rRNA operons were amplified using operon-specific PCR. The PCR products were partially sequenced in order to resolve the sequences of different 23S rRNA genes. RESULTS: One clinical isolate of S. pyogenes carrying an adenine to guanine mutation at the position 2058 of the 23S rRNA in five of the six possible rRNA genes but having no other known macrolide resistance determinants is described. The strain was highly resistant to macrolides and azalides, having erythromycin and azithromycin MICs > 256 microgram/ml. It was resistant to lincosamides (clindamycin MIC 16 microgram/ml) and also MIC values for ketolides were clearly elevated. The MIC for telithromycin was 16 microgram/ml. CONCLUSION: In this clinical S. pyogenes strain, a mutation at the position 2058 was detected. No other macrolide resistance-causing determinants were detected. This mutation is known to cause macrolide resistance in other bacteria. We can conclude that this mutation was the most probable cause of macrolide, lincosamide and ketolide resistance in this strain.200415128458
5939190.9854Resistance to antimicrobial agents of common bacteria isolated from Taiwan. Antimicrobial susceptibility of 11 commonly seen and/or important pathogenic bacteria isolated from the National Taiwan University Hospital in 1981 and 1992 was analysed. Oxacillin-resistance was most remarkable in Staphylococcus aureus. Its prevalence increased rapidly from 6.7% in 1981 to 49.7% in 1992. A high proportion of oxacillin-resistance was also found in coagulase-negative staphylococci, both in 1981 and in 1992. For Streptococcus pneumoniae, no penicillin-resistant nor erythromycin-resistant strain was found in 1981, but by 1992, 5.8% of the isolates were penicillin-resistant 42.3% erythromycin-resistant. Gentamicin-resistance was the most common problem in enterococci, with 70.6% resistance in 1992. As to Gram-negative bacteria, Enterobacter spp. demonstrated a high proportion of resistance to various antimicrobial agents: more than 72% susceptibility was found only for amikacin. Pseudomonas aeruginosa was also a highly resistant bacterium, with only 50 to 90% of susceptibility to various antipseudomonal agents. In Haemophilus influenzae, both ampicillin-resistance and chloramphenicol-resistance were remarkable, with 52.2% and 32.9% resistance, respectively, in 1992.199418611604