Drug resistance in Campylobacter jejuni, C coli, and C lari isolated from humans in north west England and Wales, 1997.
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AIMS: To test the sensitivity of strains of Campylobacter species isolated from humans in England and Wales against a range of antimicrobial agents for the purpose of monitoring therapeutic efficacy and as an epidemiological marker. METHODS: An agar dilution breakpoint technique was used to screen isolates against ampicillin, chloramphenicol, gentamicin, kanamycin, neomycin, tetracycline, nalidixic acid, ciprofloxacin, and erythromycin. Minimal inhibitory concentrations (MIC) were also determined for a sample of quinolone resistant strains. RESULTS: Approximately 50% of strains tested were resistant to at least one drug. Strains which were resistant to four or more of the drugs tested were classified as multiresistant; this occurred in 11.3% of C jejuni, 19.9% of C coli, and 63.6% of C lari. Resistance to erythromycin occurred in 1.0% of C jejuni and 12.8% of C coli. Resistance to quinolones occurred in 12% of strains, with a ciprofloxacin MIC of > 8 mg/l and a nalidixic acid MIC of > 256 mg/l; a further 4% of strains had intermediate resistance with a ciprofloxacin MIC of between 0.5 and 2 mg/l (fully sensitive strains, 0.25 mg/l or less) and a nalidixic acid MIC of between 32 and 64 mg/l (fully sensitive strains, 8 mg/l or less). CONCLUSIONS: Resistance to quinolones in campylobacters from human infection may relate to clinical overuse or use of fluoroquinolones in animal husbandry. Both veterinary and clinical use should be reconsidered and fluoroquinolone drugs used only as a treatment for serious infections requiring hospital admission. Erythromycin resistance is still rare in C jejuni but much more common in C coli. (+info)
Diversity among high-level aminoglycoside-resistant enterococci.
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A total of 55 Enterococcus faecalis and 21 Enterococcus faecium non-replicate isolates were obtained from routine clinical specimens, during a 1 year period, in a tertiary care hospital in Athens, Greece. The most common isolation site was the urinary tract (44% of E. faecalis and 33% of E. faecium isolates). No vancomycin resistance was detected. Ampicillin-resistant isolates did not produce beta-lactamase. High-level gentamicin resistance was detected in 22% and 0% of E. faecalis and E. faecium isolates, respectively. The corresponding figures for high-level streptomycin resistance were 40% and 33%. The aminoglycoside-modifying enzyme gene aac(6')+aph(2") was detected by PCR in 10 of 12 high-level gentamicin-resistant E. faecalis isolates, and the ant(6)-I gene in all high-level streptomycin-resistant isolates of both species. DNA fingerprinting by PFGE grouped 31 of 55 E. faecalis isolates into 10 clusters, and 10 of 21 E. faecium isolates into two clusters, containing two to seven isolates each. Two E. faecalis PFGE types, comprising isolates expressing high-level aminoglycoside resistance, and not observed among non-high-level aminoglycoside-resistant strains, were disseminated in building A of the hospital. In contrast, high-level aminoglycoside resistance seemed to have been acquired nosocomially by a number of genotypically different E. faecium types. Molecular typing was therefore instrumental in understanding the differences in the mode of spread and acquisition of high-level aminoglycoside resistance among these two different enterococcal species. (+info)
Risk factors for recovery of ampicillin-sulbactam-resistant Escherichia coli in hospitalized patients.
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Ampicillin-sulbactam resistance in Escherichia coli is an emerging problem. This study determined risk factors for the recovery of ampicillin-sulbactam-resistant E. coli in hospitalized patients. A case-control design was used to compare two groups of case patients with control patients. The first group of case patients consisted of patients from whom nosocomially acquired ampicillin-sulbactam-resistant E. coli strains were isolated, and the second group of case patients consisted of patients from whom ampicillin-sulbactam-susceptible E. coli strains were isolated. Control patients were a random selection among 5% of all patients admitted during the same time period. Risk factors analyzed included antimicrobial drug exposure, comorbid conditions, and demographics. Univariate and multivariate analyses were performed. Ampicillin-sulbactam-resistant E. coli strains were isolated from 175 patients, and ampicillin-sulbactam-susceptible E. coli strains were isolated from 577 patients. Nine hundred thirty-four control patients were selected. Exposure to penicillin antibiotics as a class and to ampicillin and ampicillin-sulbactam individually were the only significant, independent risk factors associated with the isolation of ampicillin-sulbactam-resistant E. coli (odds ratio [OR] = 2.32 [P < 0.001], OR = 3.04 [P = 0.02], and OR = 1.72 [P = 0.04], respectively), but they were not associated with the isolation of ampicillin-sulbactam-susceptible E. coli. Interestingly, exposure to piperacillin-tazobactam tended to protect against the isolation of E. coli strains resistant to ampicillin-sulbactam, but this did not reach statistical significance (OR = 0.13; P = 0.11). (+info)
Geographic distribution of a large mobile element that transfers ampicillin and vancomycin resistance between Enterococcus faecium strains.
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In several clonally unrelated VanB-type vancomycin-resistant Enterococcus faecium strains, we demonstrated a common physical relationship between pbp5 and Tn5382 as well as common mutations within pbp5. The majority of these strains transferred vancomycin and ampicillin resistance to E. faecium in vitro, suggesting the dissemination of similar transferable pbp5-vanB-containing mobile elements throughout the United States. (+info)
Transfer of erythromycin resistance from poultry to human clinical strains of Staphylococcus aureus.
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The transfer of ermA and ermC genes, the two most common resistance determinants of erythromycin resistance, was studied with Luria-Bertani broth in the absence of additional Ca(2+) or Mg(2+) ions. Fifteen human and five poultry isolates of Staphylococcus aureus, which were resistant to erythromycin but carried different genetic markers for erythromycin resistance, were used for conjugation. Since both the donors (Amp(s)-Tet(r)) and recipients (Amp(r)-Tet(s)) were resistant to erythromycin, the transconjugants were initially picked up as ampicillin- and tetracycline-resistant colonies. The resistance transfer mechanisms of the chromosomally located erythromycin rRNA methylase gene ermA and the plasmid-borne ermC gene were monitored by a multiplex PCR and gene-specific internal probing assay. Four groups of transconjugants, based upon the transfer of the ermA and/or ermC gene, were distinguished from each other by the use of this method. Selective antibiotic screening revealed only one type of transconjugant that was resistant to ampicillin and tetracycline. A high frequency of transfer (4.5 x 10(-3)) was observed in all of the 23 transconjugants obtained, and the direction of tetracycline and erythromycin resistance marker transfer was determined to be from poultry to clinical isolates. The transfers of the ermA and ermC genes were via transposition and transformation, respectively. (+info)
Epidemiological studies of large resistance plasmids in Haemophilus.
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The distribution of large conjugative Haemophilus influenzae plasmids in the nasopharyngeal haemophili of a group of people and in a large collection of 541 H. influenzae type b (Hib) isolates was studied. A newly developed PCR-based assay was used to detect the plasmids. The target sequences were chosen from sequence analysis of part of p1056, a large multiresistance plasmid isolated from a clinical Hib isolate, 1056. Fifty-nine per cent of people were found to carry beta-lactamase-positive (beta-lac(+)), ampicillin-resistant (ampR) haemophili with detectable plasmid sequences. Of these, 83% were in Haemophilus parainfluenzae and 17% were in H. influenzae. In the collection of 541 Hib, antibiotic resistance [beta-lac(+)ampR, beta-lac(+)ampR plus tetracycline resistance (tetR) or tetR] was highly correlated with large plasmids. It was found that 2.3% of the isolates contained large cryptic plasmids (i.e. these isolates were susceptible to antibiotics). The distribution of plasmids between invasive and carried Hib did not differ significantly (25 of 245 and 23 of 276, respectively). Isolates with large plasmids occur at high frequency in the nasopharynx of the normal human population and consist of two populations in Hib, one associated with specific antibiotic resistance traits and the other cryptic. These plasmids do not appear to influence the invasiveness of Hib. (+info)
Evaluation of IS200-PCR and comparison with other molecular markers To trace Salmonella enterica subsp. enterica serotype typhimurium bovine isolates from farm to meat.
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A procedure that uses an original molecular marker (IS200-PCR) and that is based on the amplification of DNA with outward-facing primers complementary to each end of IS200 has been evaluated with a collection of 85 Salmonella enterica subsp. enterica serotype Typhimurium isolates. These strains were isolated from a group of 10 cows at different stages: during transportation between the farm and the slaughterhouse, on the slaughter line, from the environment, and from the final product (ground beef). The 85 isolates were characterized by their antibiotic resistance patterns and were compared by IS200-PCR and by use of four other genotypic markers. Those markers included restriction profiles for 16S and 23S rRNA (ribotypes) and amplification profiles obtained by different approaches: random amplified polymorphic DNA analysis, enterobacterial repetitive intergenic consensus PCR, and PCR ribotyping. The results of the IS200-PCR were in accordance with those of other molecular typing methods for this collection of isolates. Five different genotypes were found, which made it possible to refine the hypotheses on transmission obtained from phenotypic results. The genotyping results indicated the massive contamination of the whole group of animals and of the environment by one clonal strain originally recovered from one cow that excreted the strain. On the other hand, a few animals and their environment appeared to be simultaneously contaminated with genetically different strains. (+info)
Regional variation in ampicillin and trimethoprim resistance in Escherichia coli in England from 1990 to 1997, in relation to antibacterial prescribing.
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Over 200 hospitals in England report resistance data for bacteraemia and meningitis isolates to the Public Health Laboratory Service. We reviewed ampicillin and trimethoprim resistance rates from 1990 to 1997 for Escherichia coli, which is the species reported most frequently from these bacteraemias. Ampicillin resistance was relatively stable over time, but varied between Health Regions. The proportion of ampicillin-resistant E. coli in the East Anglia region remained +info)