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R Canton

Publications and source records attributed to R Canton.

13 recordsLinked to original sources
PubMed2003

Worldwide incidence, molecular epidemiology and mutations implicated in fluoroquinolone-resistant Streptococcus pneumoniae: data from the global PROTEKT surveillance programme.

OBJECTIVES: To analyse the mutations and epidemiology associated with fluoroquinolone-resistant pneumococci collected as part of the PROTEKT global surveillance programme during 1999-2000. METHODS: Sixty-nine centres in 25 countries submitted a total of 3362 Streptococcus pneumoniae isolates, for which the MICs of antimicrobial agents were determined using NCCLS methodology. RESULTS: Levofloxacin resistance was low overall (1% worldwide), with higher rates in: Hong Kong (14.3%), South Korea (2.9%), USA (1.8%), Mexico (1.5%), Canada (1.4%) and Japan (1.3%). Levofloxacin resistance was very low or absent in European countries, and absent in Australia. Worldwide, there was a total of 35 levofloxacin-resistant isolates, of which 22 (63%) were resistant and 10 (29%) were intermediate to moxifloxacin. All levofloxacin-resistant isolates were susceptible to telithromycin (< or =0.5 mg/L), linezolid (< or =2 mg/L) and quinupristin/dalfopristin (< or =1 mg/L). One or more mutations in the topoisomerase genes were identified in all levofloxacin-resistant isolates; most of these isolates (33/35) had a mutation in one of the DNA gyrase encoding genes (gyrA, gyrB) and one of the topoisomerase IV encoding genes (parC, parE). Eighteen (51%) isolates carried the same combination of amino acid substitutions: Ser-81-->Phe in GyrA and Ser-79-->Phe in ParC. Isolates displaying a levofloxacin MIC of 2-4 mg/L generally had no mutation or one mutation in either a DNA gyrase or a topoisomerase IV gene, although most mutations were in parC. CONCLUSIONS: Most levofloxacin-resistant isolates possess two mutations (one in DNA gyrase and one in topoisomerase IV). Although multilocus sequence typing demonstrated that most of these isolates were unrelated, 12 (34%) were the Spain23F-1 clone: 10 from Hong Kong and one each from Saskatchewan, Canada and Sao Paulo, Brazil.

Amino Acid Substitution↗
PubMed2002

Multicentre evaluation of the VITEK 2 Advanced Expert System for interpretive reading of antimicrobial resistance tests.

Interpretive reading analyses the complete resistance profiles of bacteria to multiple antibiotics and infers the resistance mechanisms present; it aids therapeutic choice and enhances surveillance data. We evaluated the Advanced Expert System (AES), which interprets MICs generated by the VITEK 2. Ten European laboratories tested 42 reference strains and 76-106 of their own strains, representing important resistance genotypes. Interpretive reading by the VITEK 2 AES achieved full agreement with genotype data for 88-89% of strains, with the correct mechanism identified as one of two possibilities for a further 5-6%. Mechanisms inferred with 90% agreement with reference data included methicillin resistance in staphylococci, glycopeptide resistance in enterococci, quinolone resistance in staphylococci and Enterobacteriaceae, AAC(6')-APH(2")-mediated aminoglycoside resistance in Gram-positive cocci, erm-mediated macrolide resistance in pneumococci, extended-spectrum beta-lactamases (ESBLs) in Enterobacteriaceae and Pseudomonas aeruginosa, and acquired penicillinases in Enterobacteriaceae. VanA, VanB and VanC phenotypes of enterococci were distinguished reliably, and ESBL production was accurately inferred in AmpC-inducible species as well as Escherichia coli and Klebsiella spp. Mechanisms identified, but only as possibilities among several, included IRT-type beta-lactamases and individual aminoglycoside-modifying enzymes in Enterobacteriaceae. Most disagreements with reference data concerned pneumococci found to have high-level penicillin resistance by the VITEK 2 AES but previously determined, phenotypically, to have intermediate resistance. When ESBL production was inferred in E. coli and klebsiellae, the VITEK 2 AES edited susceptible results for cephalosporins (except cefoxitin) to resistant; when an acquired penicillinase was inferred in Enterobacteriaceae, piperacillin results were edited to resistant; and when staphylococci were found methicillin resistant, resistance was reported for all beta-lactams. Further editing may be desirable (e.g. of cephalosporin results for salmonellas inferred to have ESBLs).

Data Interpretation, Statistical↗
PubMed2001

Variations in the prevalence of strains expressing an extended-spectrum beta-lactamase phenotype and characterization of isolates from Europe, the Americas, and the Western Pacific region.

To evaluate the prevalence of extended-spectrum beta-lactamase (ESBL)-producing strains among species of Enterobacteriaceae, a microdilution susceptibility test was performed with strains of Klebsiella pneumoniae, Escherichia coli, Proteus mirabilis, and Salmonella species that were isolated as part of the SENTRY project. The highest percentage of ESBL phenotype (defined as a minimum inhibitory concentration [MIC] > or =2 microg/mL for ceftazidime, ceftriaxone, or aztreonam) was detected among K. pneumoniae strains from Latin America (45%), followed by those from the Western Pacific region (25%), Europe (23%), the United States (8%), and Canada (5%). P. mirabilis and E. coli strains for which MICs of extended-spectrum cephalosporins or monobactams were elevated also were more prominent in Latin America. Testing with ceftazidime revealed more isolates with elevated MICs than did testing with ceftriaxone or aztreonam. ESBL strains showed high levels of co-resistance to aminoglycosides, tetracycline, trimethoprim-sulfamethoxazole, and ciprofloxacin. Imipenem remains highly effective against ESBL strains. Organisms expressing an ESBL are widely distributed worldwide, although prevalence rates are significantly higher in certain geographic regions.

Aztreonam↗
PubMed1998

Helicobacter pylori infection and insulin-dependent diabetes mellitus.

Helicobacter pylori is associated with different diseases: duodenal ulcer, rosacea, ischaemic heart disease and gastric cancer. Given the abnormal immunological response and the high prevalence of gastrointestinal symptoms in diabetic patients, we conducted a study on H. pylori prevalence among these patients. We designed a case control study of a population-based cohort. Eighty insulin-dependent diabetes mellitus (IDDM) patients with an average age (24.05 +/- 8.3 years), and 100 control subjects (25 +/- 7.1 years) were selected to verify the seroprevalence of Helicobacter pylori in these populations. One serum sample was obtained from each subject for evaluation of antibodies against Helicobacter pylori, parietal cells (APA) and pancreatic islets cells (ICA). The seroprevalence of H. pylori among IDDM patients aged less than 24 years was significantly higher than among control subjects; the corresponding rate among IDDM aged greater than 24 years was significantly lower than among control subjects. Antibodies against parietal cells (APA) and islet cells (ICA) among H. pylori positive diabetic patients were significantly higher than among H. pylori negative diabetic patients. IDDM patients were subdivided on the basis of the evolutive course of diabetes. Seroprevalence of H. pylori as well as prevalence of ICAs decreased with IDDM duration. Nevertheless, no variation in the prevalence of APAs during the course of diabetes was observed. We observed an association between the seroprevalence of Helicobacter pylori and the duration of IDDM. The seroprevalence of H. pylori and ICA decreased with the evolutive course of diabetes mellitus among IDDM. The prevalence of ICA and APA in IDDM H. pylori positive subjects was higher than among controls.

Adolescent↗
PubMed1998

Antimicrobial susceptibility profiles of oropharyngeal viridans group streptococci isolates from cystic fibrosis and non-cystic fibrosis patients.

The antimicrobial susceptibility profile of 77 oropharyngeal viridans streptococci isolates from 34 cystic fibrosis (CF) patients and 58 isolates from 43 healthy non-CF patients were studied by the E-test and the standard disk diffusion methods. Overall penicillin and cefotaxime resistances (intermediate plus resistant isolates) were significantly higher (p < 0.05) among CF isolates (72.7% and 45.5%, respectively) than among non-CF isolates (51.7% and 15.5%, respectively). No significant difference was observed in overall (intermediate plus resistant) erythromycin resistance rates, although high-level erythromycin resistance (> or =32 microg/mL) was more frequently found in CF isolates (24.6%) than in non-CF isolates (12.1%). An unexpected high percentage of isolates showed low level erythromycin resistance (MIC range, 0.5-15 microg/mL): 41.5% in cystic fibrosis and 46.5% in non-CF isolates. No significant differences were observed regarding the percentage of colonized patients with at least one penicillin-resistant isolate. On the contrary, colonization with cefotaxime (p < 0.001) or erythromycin (p = 0.014) resistant isolates were significantly more prevalent in CF patients. Similar tetracycline and chloramphenicol resistance rates were observed for both groups. Viridans isolates resistant to a single antibiotic were more prevalent among non-CF patients and multiple resistance was higher among CF patients. Prior antibiotic exposure could result in differences in beta-lactam resistance and colonization rates with resistant isolates between both groups. None of the non-CF patients was previously treated with antimicrobials for a period of three months before sampling. In contrast, 94.1% of CF patients were treated with antimicrobials within the same period; 65.6% with beta-lactam antibiotics. Patients with CF disease, frequently exposed to antimicrobials, may be a reservoir of viridans streptococci isolates with resistance determinants, particularly to beta-lactam antibiotics.

Adolescent↗
PubMed1995

New extended-spectrum TEM-type beta-lactamase from Salmonella enterica subsp. enterica isolated in a nosocomial outbreak.

A new extended-spectrum beta-lactamase was detected in a lactose-positive Salmonella enterica subsp. enterica strain that caused a nosocomial outbreak involving eight patients in a pediatric cardiology unit. This strain showed high levels of resistance to ceftazidime and aztreonam and relatively low levels of resistance to cefotaxime and ceftriaxone. Resistance was associated with a conjugative plasmid of 59 kb, which encoded a new beta-lactamase with an isoelectric point of 5.9 that strongly hydrolyzed ceftazidime and to a much lesser extent hydrolyzed cefotaxime. The enzyme activity was inhibited by clavulanate. The corresponding bla gene was cloned and sequenced. The deduced amino acid sequence showed three significant amino acid replacements with respect to the TEM-1 sequence: Arg-164-->His, Glu-240-->Lys, and Thr-265-->Met. This combination is unique among extended-spectrum beta-lactamases and served to characterize the new enzyme, TEM-27.

Amino Acid Sequence↗
PubMed1993

Characterization of a new TEM-type beta-lactamase resistant to clavulanate, sulbactam, and tazobactam in a clinical isolate of Escherichia coli.

A clinical Escherichia coli strain highly resistant to the combinations of amoxicillin-clavulanate, ampicillin-sulbactam, and piperacillin-tazobactam was isolated from a patient with a community-acquired urinary tract infection who was previously treated with amoxicillin-clavulanate. These resistances were carried by a 45-kb conjugative plasmid encoding for a single beta-lactamase with a pI of 5.4. Cloning and sequencing of the new beta-lactamase, IRT-3, revealed identity with the blaT1 gene encoding the TEM-1 beta-lactamase except for a replacement of the methionine residue at position 67 by isoleucine and of the methionine residue at position 180 by threonine. Both mutations were segregated by the construction of hybrid genes, and only the mutation at methionine at position 67 was related to resistance to the suicide inhibitors. The inhibitory effects of clavulanate, sulbactam, and tazobactam on the TEM-1 enzyme were substantially decreased in comparison with those on IRT-3, as indicated by the 50% inhibitory concentrations.

Clavulanic Acid↗
PubMed1991

The incidence and beta-lactam resistance of Proteus vulgaris in hospital infections: the last decade.

During the period of 1980-1990, 581 Proteus vulgaris strains were obtained in a general hospital. They were considered as the significant isolate in 0.6% of soft tissue infections, 0.6% of urinary tract infections and in 0.2% of bacteremic episodes. Sixty-three percent of the 393 tested strains showed resistance to ampicillin, cefazolin and cefamandole or cefuroxime. About 7% were susceptible to all beta-lactam drugs, and showed a very low beta-lactamase activity and 5% of the strains showed a phenotype of resistance including ampicillin, carbenicillin-ticarcillin, cefazolin and cefamandole or cefuroxime, and presented increased chromosomal beta-lactamase activity. Cefotaxime-resistance was detected in 2% of the isolates which appeared in the period 1987-1990.

Ampicillin Resistance↗