Epidemiological typing of methicillin-resistant Staphylococcus aureus (MRSA): spa typing versus pulsed-field gel electrophoresis.

Molecular methods based on sequencing, such as spa typing, have facilitated epidemiological typing of bacterial isolates compared to the gold standard pulsed-field gel electrophoresis (PFGE), a technically more demanding method. We studied methicillin-resistant Staphylococcus aureus (MRSA) in 4 Swedish counties from 2003 through 2005, and compared spa typing and PFGE results to epidemiological data. Of 280 MRSA isolates, 91 were from sporadic cases and 189 were associated with 35 outbreaks. A total of 50 spa types and 74 PFGE patterns were detected. 60 (21%) of the MRSA isolates carried the Panton-Valentine leukocidin (PVL) genes. 12 of the PVL-positive MRSA were healthcare associated. 25 of the spa types and 31 of the PFGE patterns were associated with outbreaks. In 1 of the outbreaks we found isolates with different but closely related spa types, and in 6 of the outbreaks we observed isolates with different but related PFGE patterns. In this low-endemic setting, with outbreaks limited in time and place, we found spa typing to be a useful tool for epidemiological typing of MRSA, due to its rapidity, accessibility, ease of use, and standardized nomenclature.

Staphylococci in primary skin and soft tissue infections in a Swedish county.

Patients with skin and soft tissue infections (SSTI) are frequently encountered in primary health care. The majority are uncomplicated and treated empirically by surgical incision and drainage and/or antibiotics. This strategy may risk delaying the detection of methicillin-resistant Staphylococcus aureus (MRSA), which, although still rare in Sweden, is increasingly being found in patients with SSTI. To avoid 'late detection' of MRSA, primary health care physicians in Kronoberg county, Sweden, were asked to perform a culture as soon as the patient's first visit. Samples from 175 patients with primary SSTI confirmed that S. aureus is the dominant pathogen. Two cases of MRSA were detected. Furthermore, isolates of S. aureus producing the Panton-Valentine leukocidin (PVL) toxin were more common among isolates from SSTI than among S. aureus from secondary infections. Finally, we confirmed the importance of the coagulase-negative staphylococcal species S. lugdunensis as a pathogen as it was isolated as the only pathogen in 10% of the skin and soft tissue samples.

Effect of esomeprazole triple therapy on eradication rates of Helicobacter pylori, gastric ulcer healing and prevention of relapse in gastric ulcer patients.

OBJECTIVES: To compare esomeprazole-based triple therapy with esomeprazole alone for the eradication of Helicobacter pylori (H. pylori), healing of ulcer and prevention of relapse in H. pylori-related gastric ulcer (GU) diseases. METHODS: In this double-blind study, 401 H. pylori-positive patients with more than or equal to two GUs were randomized to: esomeprazole (20 mg) twice daily (bid) and amoxicillin (1000 mg) bid and clarithromycin (500 mg) bid (EAC) for 1 week, followed by placebo for 3 weeks (EAC and placebo); EAC for 1 week, followed by esomeprazole (20 mg) once daily (E20) for 3 weeks (EAC and E20); or esomeprazole (20 mg) bid and placebo antimicrobials for 1 week, followed by E20 for 3 weeks (E20 bid and E20). Patients with unhealed GUs at 4 weeks received E20 for an additional 4 weeks. Healed patients were followed up for 12 months. RESULTS: Eradication rates at 4 weeks or 8 weeks were 82% for EAC and E20, 77% for EAC and placebo and 9.5% for E20 bid and E20 (intention-to-treat analysis). Significantly more patients receiving EAC than those receiving esomeprazole alone remained free of GUs during follow-up [EAC and E20, 90%; EAC and placebo, 87%; P=0.0005 for combined group vs. esomeprazole alone [E20 bid and E20 (74%)]. All treatments were well tolerated. CONCLUSION: Esomeprazole-based triple therapy is effective for the eradication of H. pylori, healing of GU and prevention of relapse. Esomeprazole monotherapy for 3 weeks after triple therapy may be beneficial in terms of healing.

Dissemination of multidrug-resistant bacteria into the Arctic.

We show that Escherichia coli isolates originating from Arctic birds carry antimicrobial drug resistance determinants. This finding implies that dissemination of drug-resistant bacteria is worldwide. Resistance genes can be found even in a region where no selection pressure for resistance development exists.

Persistence of resistant Staphylococcus epidermidis after single course of clarithromycin.

We examined how a common therapy that includes clarithromycin affects normally colonizing Staphylococcus epidermidis. Samples from the nostrils of 5 patients receiving therapy were collected before, immediately after, 1 year after, and 4 years after treatment. From each patient and sample, S. epidermidis strains were isolated and analyzed for clarithromycin susceptibility and presence of the erm(C) gene. We show that macrolide-resistant strains of S. epidermidis were selected during therapy and that the same resistant strain may persist for 4 years, in the absence of further antimicrobial treatment.

Bacteria with increased mutation frequency and antibiotic resistance are enriched in the commensal flora of patients with high antibiotic usage.

BACKGROUND: We examined how prolonged antibiotic treatment affected the resistance and mutation frequency of human microflora isolated from intestine (Escherichia coli, enterococci spp.), pharynx (alpha-streptococci) and nostril (coagulase-negative staphylococci, CoNS). METHODS: Samples were collected from patients at the Center of Cystic Fibrosis (n=18) and the haematology ward (n=18) of the University Hospital, Uppsala, Sweden. The individually used amount of antibiotics for 1 year was recorded as the defined daily dose (DDD). Primary health care patients (n=30), with no antibiotic treatment for 1 year before sampling, were used as controls. Three isolates of each bacterium from each patient were examined. Antibiotic susceptibilities were determined by disc diffusion. Mutation frequencies to rifampicin resistance were measured on 30 independent cultures of each bacterial species from each individual by plating on rifampicin agar plates. For alpha-streptococci the mutation frequency to streptomycin resistance was also determined. RESULTS: Isolates from patients with high antibiotic use showed a pronounced shift towards increased resistance and a small but significant increase in the mutation frequency compared with isolates from the controls. For E. coli, enterococci and CoNS the increase in geometric mean mutation frequency in the patient group was 3-, 1.8- and 1.5-fold, respectively (P values 0.0001, 0.016 and 0.012). For alpha-streptococci there was a significant difference in geometric mean mutation frequency between patient and control groups for streptomycin resistance (P=0.024) but not for rifampicin resistance (P=0.74). CONCLUSIONS: High antibiotic use selected for commensals with highly increased resistance and a slight increase in mutation frequency.

Long-term persistence of resistant Enterococcus species after antibiotics to eradicate Helicobacter pylori.

BACKGROUND: Antibiotic treatment selects for resistance not only in the pathogen to which it is directed but also in the indigenous microflora. OBJECTIVE: To determine whether a widely used regimen (clarithromycin, metronidazole, and omeprazole) for Helicobacter pylori eradication affects resistance development in enterococci. DESIGN: Cohort study. SETTING: Endoscopy units at 3 community hospitals in Sweden. PATIENTS: 5 consecutive dyspeptic patients who were colonized with H. pylori, had endoscopy-confirmed duodenal ulcer, and received antibiotic treatment, and 5 consecutive controls with dyspepsia but no ulcer who did not receive treatment. MEASUREMENTS: Fecal samples were obtained from patients and controls before, immediately after, 1 year after, and 3 years after treatment. From each patient and sample, enterococci were isolated and analyzed for DNA fingerprint, clarithromycin susceptibility, and presence of the erm(B) gene. RESULTS: In treated patients, all enterococci isolated immediately after treatment showed high-level clarithromycin resistance due to erm(B). In 3 patients, resistant enterococci persisted for 1 to 3 years after treatment. No resistance developed among controls. CONCLUSION: A common H. pylori treatment selects for highly resistant enterococci that can persist for at least 3 years without further selection.

Determining antibiotic resistance in Helicobacter pylori.

Resistance development is a significant clinical problem in Helicobacter pylori and represents the major cause of treatment failure. Today the problem is most focused on the macrolide clarithromycin that is an essential component of the H. pylori treatment. Traditional methods for resistance determination, e.g., disc diffusion tests or E-tests, could in the next 5 years be replaced by DNA-based methods. The most commonly used molecular methods available today are not used in the daily routine work. Rapid and reliable DNA-based methods for prediction of antimicrobial resistance phenotype are currently available within research. As fabrication costs reduce and validated targeted assays are developed with easy hands-on procedures, it is most likely that such assays will become important tools for clinical diagnosis of resistant H. pylori strains.