Margareta Rylander

Helicobacter pylori in 205 Consecutive Endoscopy Patients

The presence of Helicobacter pylori in the gastric, antral mucosa of 205 consecutive, unselected gastroscopy patients was investigated by 1-3 biopsies for urea broth test and culture, 1 biopsy for histological examination and 1 blood sample for serology by ELISA. Overall, 41% were positive for H. pylori by culture, 32% by urea broth test, 24% by histological staining and 67%, 56% and 49% for the 3 cut-off limits applied to serology. Culture and serology indicated the presence of H. pylori in 79-92% of the 14 cases with duodenal ulcer, in 59-82% of the 28 cases with gastric ulcers, in 45-71% of the 51 cases with endoscopic gastritis and in 33-69% of 13 cases with oesophagitis. In patients with histological antritis, H. pylori was identified by culture in 71% (60/84), by serology in 95%, 88% and 81% with the different cut-off limits. The sensitivity of serology ranged from 99-78% depending on the cut-off limits and the specificity from 78-100% against all parameters combined. These results suggest that serology is a useful screening method for the presence of H. pylori. Future antibiotic treatment studies are required to evaluate the clinical relevance of H. pylori in gastrointestinal disease and to investigate the possibility to monitor eradication by serology.

VIM-4 in a Carbapenem-Resistant Strain of Pseudomonas aeruginosa Isolated in Sweden

The first VIM metallo-β-lactamase (MBL), VIM-1, was described in Verona in 1997 for a Pseudomonas aeruginosa isolate ([2][1]). Since then VIM-2 has been identified in Marseille in 2000 ([1][2]), VIM-3 has been identified in Taiwan ([7][3]) in 2001, and VIM-4 has been identified in Greece in 2001 ([

Long-term Antibiotic Resistance Surveillance of Gram-negative Pathogens Suggests that Temporal Trends can be Used as a Resistance Warning System

Antibiotic resistance among Gram-negative bacteria and antibiotic consumption were investigated at the Karolinska Hospital, Stockholm, Sweden over a 12-y period. The investigation showed an increase in ciprofloxacin resistance of Escherichia coli from 0% in 1991 to 7% in 1997 and to 11% in 1999. Resistance among Pseudomonas aeruginosa isolates to ciprofloxacin increased from 2.5% in 1991 to 9.0% in 1997 and to 13% in 1999. Resistance levels for norfloxacin showed the same high statistical significance in terms of the temporal trend. A more detailed analysis showed higher resistance against norfloxacin in specific wards. Relationships between antibiotic use and antibiotic susceptibility showed different patterns. The increased ciprofloxacin resistance of E. coli and P. aeruginosa during the study period was paralleled by an increased consumption of quinolones. During the 12-y study period the total use of cephalosporins increased 2.5-fold, while the levels of E. coli resistance to cefuroxime and cefotaxime remained stable. A third pattern was seen with trimethoprim-sulfamethoxazole, namely increasing resistance of E. coli as the use of trimethoprim-sulfamethoxazole declined. The analysis of resistance levels and antibiotic consumption in the present study suggests different mechanisms for the increased resistance. The significant trend of increased resistance to antibiotics over time constitutes an important warning system.

Norfloxacin versus co-trimoxazole for treatment of urinary tract infections in adults: microbiological results of a coordinated multicentre study

In a prospective, coordinated, double-blind multicentre trial, outpatients with urinary tract infections were randomized to 7 days b.i.d. treatment with norfloxacin 200 mg or 400 mg or trimethoprim/sulfamethoxazole. The most prevalent species was Escherichia coli (76.6%) followed by Staphylococcus saprophyticus (14.1%), the latter of which showed a marked seasonal variation with peak incidence during late summer. Minimum inhibitory concentrations (MICs) of 11 antibiotics for 651 pre-treatment bacterial strains were studied. Norfloxacin was found to be active against all isolates with MICs less than or equal to mg/l for gram-negative and less than or equal to 8 mg/l for gram-positive isolates. Reduced susceptibility to norfloxacin was seen in 2 strains of E. coli and 1 of Klebsiella pneumoniae from patients with persisting or relapsing infections following treatment with norfloxacin 400 mg b.i.d. Of other antibiotics tested, ampicillin, cephalothin and sulfamethoxazole were found to have poor activity against many gram-negative isolates while nalidixic acid and mecillinam lacked activity against all gram-positives. Cefotaxime, gentamicin, trimethoprim and trimethoprim/sulfamethoxazole were generally highly active against the isolated bacterial strains.

Calibration of Disk Diffusion Antibiotic Susceptibility Testing: Species-related Trovafloxacin Interpretive Zone Breakpoints and Selection of Disk Potency

International comparisons of antibiotic susceptibility require the use of common minimum inhibitory concentration (MIC) limits. Disk diffusion test results are not directly suitable for such comparisons, since different standards are often used and zone breakpoints issued might reflect different MIC limits. We have used single strain regression analysis (SRA) for the calibration of the disk test, both according to species and individual laboratory, and for quality control of trovafloxacin disk diffusion tests in 5 laboratories in Sweden. Preliminary controls using histogram analysis including subtraction histograms of reference strains revealed marked differences between different laboratories. SRA was performed on 4 reference strains, S. aureus, E. faecalis, E. coli and P. aeruginosa, using disks containing 1, 3, 10, 30 and 100 microg trovafloxacin. The results using SRA showed a difference between laboratories using Biodisk PDM medium, which produced smaller zones, and those using Oxoid IsoSensitest. Species-related regression lines for laboratories using either medium were calculated and corresponding interpretive zone breakpoints determined for MIC limits. Rational criteria for the selection of a suitable disk content of an antibiotic were also defined and applied to trovafloxacin. The 10 microg disk selected by NCCLS (National Committee for Clinical Laboratory Standards) proved optimal.

Comparison Between Agar and Broth Minimum Inhibitory Concentrations of Cefamandole, Cefoxitin, and Cefuroxime

The in vitro susceptibility to cefamandole, cefoxitin, and cefuroxime of clinical isolates of Streptococcus faecalis, Klebsiella, and indole-positive Proteus was assayed using minimum inhibitory concentration (MIC) determinations in broth and on solid media. It could be demonstrated that the agar dilution MICs obtained when S. faecalis was tested against cefuroxime and when indole-positive Proteus strains were tested against cefamandole tended to be considerably lower than those obtained with the broth dilution technique. The Klebsiella strains tested did not show any major differences with regard to MICs in broth or on solid media. Using an animal experimental infection model it could be demonstrated that with indole-positive Proteus the higher broth MIC correlated better to the observed data than the lower agar MIC when a β-lactamase-producing strain was tested. The data obtained indicated that the β-lactamase of the indole-positive Proteus strain was inducible. The results of the study gave evidence for a risk of false susceptibility of some bacterial species against cefamandole when agar techniques, e.g. paper disk diffusion, are used. For cefuroxime, the same phenomenon can be expected with S. faecalis and to some extent with indole-positive Proteus. In this study, cefoxitin seemed considerably less affected by the technique used for susceptibility testing.

Trovafloxacin Susceptibility of Aerobic Clinical Bacterial Isolates from Sweden

Trovafloxacin susceptibility was studied in aerobic clinical isolates of bacterial pathogens from 5 microbiology laboratories in Sweden. Trovafloxacin and ciprofloxacin minimum inhibitory concentration (MIC) determinations were performed on 474 clinical isolates. Disk diffusion tests using trovafloxacin and ciprofloxacin 10 microg disks were performed on a total of 7142 clinical isolates (trovafloxacin). Susceptibility interpretations for trovafloxacin and ciprofloxacin were determined from MIC values and disk diffusion tests using species-related MIC-limits and zone diameter breakpoints. Eight of 12 gram-positive species groups were fully susceptible to trovafloxacin as judged by MIC tests. Trovafloxacin gave MIC50 values of 0.032 mg/l for S. aureus, 1.0 mg/l for MRSA, 0.064 mg/l for coagulase negative staphylococci, 1.0 mg/l for MRSE, 0.064 mg/l for S. saprophyticus, 0.125 mg/l for group A and group B streptococci, 0.064 mg/l for group C and G streptococci and S. pneumoniae, 0.25 mg/l for E. faecalis, and 16.0 mg/l for E. faecium. These MIC values were 4-16-fold lower than those of ciprofloxacin. Both MIC and disk tests showed similar levels of susceptibility among gram-negative isolates for trovafloxacin and ciprofloxacin. For most gram-negative species the trovafloxacin MIC50 values were similar to or slightly higher than those for ciprofloxacin. Trovafloxacin MIC values were much lower for Acinetobacter strains, but higher for P. mirabilis compared with ciprofloxacin. The favourable susceptibility levels of Swedish aerobic pathogens to trovafloxacin emphasize the potential of this drug for the treatment of serious infections.