PubMed Health⌕ Search

Biomedical subjects

Ronald N Jones

Publications and source records attributed to Ronald N Jones.

At least 55 records · Page 3Linked to original sources
PubMed2006

Prevalence and antimicrobial susceptibility patterns among gastroenteritis-causing pathogens recovered in Europe and Latin America and Salmonella isolates recovered from bloodstream infections in North America and Latin America: report from the SENTRY Antimicrobial Surveillance Program (2003).

Gastroenteritis-causing pathogens are the second leading cause of morbidity and mortality worldwide. Complicating the clinical diarrhoea syndrome is the emergence of antimicrobial resistance among the responsible bacterial pathogens. The reported increases in fluoroquinolone resistance in Salmonella, Shigella and Campylobacter have been extremely worrisome considering the primary role of ciprofloxacin as a treatment. In this study, 1479 bacterial isolates from gastroenteritis infections were collected in Europe and Latin America, which included Salmonella spp. (834; 56%), Shigella spp. (311; 21%), Campylobacter spp. (182; 12%) and Aeromonas spp. (72; 5%). The fluoroquinolones displayed the greatest activity against these pathogens, with only three non-Campylobacter spp. strains being non-susceptible using current Clinical and Laboratory Standards Institute (CLSI) breakpoint criteria. Whilst ciprofloxacin resistance in European and Latin American Salmonella was only 0.2% and 0.0%, respectively, a total of 16.2% and 12.9% of isolates were resistant to nalidixic acid, indicating possible first-step gyrA mutations. Among confirmed extended-spectrum beta-lactamase-producing Salmonella strains, CTX-M genes were detected in 15 originating from Russia. Erythromycin and azithromycin were the most potent agents tested against Campylobacter spp. (values of minimum inhibitory concentration for 90% of the organisms, 0.5 mg/L and 0.12 mg/L, respectively), with erythromycin displaying the highest susceptibility (91.1%). Salmonella isolates from bloodstream infections displayed antibiograms that were nearly identical to strains causing gastroenteritis. Considering the role that antimicrobial therapy plays in the management of moderate to severe bacterial gastroenteritis, global surveillance and local/national public health programmes can provide critical data illuminating the dissemination of resistance and guidance for empirical therapy.

Aeromonas↗
PubMed2006

Occurrence and characterization of carbapenemase-producing Enterobacteriaceae: report from the SENTRY Antimicrobial Surveillance Program (2000-2004).

Emergence and dissemination of Enterobacteriaceae isolates harboring carbapenemases in various geographic regions represents a significant threat to the management of nosocomial infections. Enterobacteriaceae isolates from the SENTRY Antimicrobial Surveillance Program (2000-2004) demonstrating decreased susceptibility to imipenem and meropenem (minimum inhibitory concentration [MIC], > or =2 mg/L) were evaluated for the production of metallo-beta-lactamases and serine carbapenemases using disk approximation and polymerase chain reaction (PCR) tests. Carbapenemase-producing strains were epidemiologically typed by automated riboprinting and pulsed-field gel electrophoresis (PFGE) to establish clonality. Among 37,557 Enterobacteriaceae (5 genus groups) evaluated, 119 (0.32%) had increased carbapenem MIC values, and a carbapenemase was identified in 51 (42.9%) of these strains. KPC-2 and KPC-3 were the most frequently occurring carbapenemases (24 isolates, 20.2%) in the United States and were detected in Klebsiella spp, Citrobacter spp., Enterobacter spp., and Serratia marcescens strains isolated in New York, Arkansas, and Virginia. SME-2-producing S. marcescens were isolated in the New York City area, Texas, and Ohio, while NMC-A was found in one E. cloacae strain from New York. In contrast, metallo-beta-lactamases were prevalent in Europe. IMP-1-producing E. cloacae (11 isolates) were detected in Turkey, while VIM-1-producing strains were found in Italy (Enterobacter spp.) and Greece (Klebsiella pneumoniae). Clonal dissemination of carbapenemase-producing strains was observed in several medical centers on both continents. The occurrence of carbapenemases in various Enterobacteriaceae remains rare but appears to be spreading geographically (not in Latin America), mainly with metallo-beta-lactamases being found in Mediterranean Europe and KPC enzymes in the New York City area.

Anti-Bacterial Agents↗
PubMed2006

Changing antimicrobial susceptibility patterns among Streptococcus pneumoniae and Haemophilus influenzae from Brazil: Report from the SENTRY Antimicrobial Surveillance Program (1998-2004).

Although antimicrobial resistance rates among Streptococcus pneumoniae and Haemophilus influenzae have increased significantly in most countries in the last years, most studies from Brazil report relatively low resistance rates among these pathogens. In this study, we analyzed the susceptibility patterns of S. pneumoniae and H. influenzae from Brazil during a 7-year period. A total of 829 S. pneumoniae and 718 H. influenzae consecutively collected from 1998 to 2004, mainly from respiratory tract and bloodstream infections, were susceptibility tested by broth microdilution methods against >30 drugs and the results were analyzed by year. Overall, 77.8% of S. pneumoniae strains were considered susceptible (MIC, < or =0.06 microg/ml) to penicillin. Resistance to penicillin (MIC, > or =2 microg/ml) and ceftriaxone (MIC, > or =4 microg/ml) were detected in 7.5 and 0.5% of strains, respectively. The fluoroquinolones, levofloxacin (MIC90) 1 microg/ml) and gatifloxacin (MIC90, 0.5 microg/ml), were active against 99.8% of the isolates tested. Among the other non-beta-lactam drugs tested, the rank order of susceptibility rates was chloramphenicol (98.9%) > clindamycin (96.4%) > erythromycin (90.6%) > tetracycline (69.8%) > trimethoprim/sulfamethoxazole (36.7%). Resistance to penicillin has increased markedly among S. pneumoniae isolates over 7 years (from 2.9 to 11.0%). Additionally, resistance rates against erythromycin, clindamycin, and tetracycline decreased among pneumococcal strains during the same period. S. pneumoniae recovered from pediatric patients (< or =5 years) showed increased penicillin and trimethoprim/sulfametroxazole resistance rates compared to older populations. The rate of ampicillin resistance among H. influenzae was 14.0%, which also corresponds with the beta -lactamase production rate. All H. influenzae isolates were susceptible to amoxicillin/clavulanate (MIC90, 1 microg/ml), ceftriaxone (MIC90, < or =0.008 microg/ml), cefepime (MIC90, 0.12 microg/ml), ciprofloxacin (MIC90, < or = 0.12microg/ml), levofloxacin (MIC90, < or =0.5 microg/ml), and gatifloxacin (MIC90, < or =0.03 microg/ml). Resistance to the antimicrobials tested remained very stable among H. influenzae isolates during the 7-year study period. The continued emerging antimicrobial resistances found in these pathogens (mainly S. pneumoniae) highlight the need for alternative agents for the treatment of infections caused by these species.

Anti-Bacterial Agents↗
PubMed2006

Activity of retapamulin (SB-275833), a novel pleuromutilin, against selected resistant gram-positive cocci.

Retapamulin (SB-275833), the first pleuromutilin to be developed for human topical use, was tested against a selected population of staphylococci and beta-hemolytic streptococci. The MIC90 results for retapamulin were 0.12 microg/ml for Staphylococcus aureus and < or = 0.03 microg/ml for Streptococcus pyogenes; no cross-resistance was observed for organism subsets resistant to oxacillin, erythromycin, or mupirocin.

Anti-Bacterial Agents↗
PubMed2006

Daptomycin bactericidal activity and correlation between disk and broth microdilution method results in testing of Staphylococcus aureus strains with decreased susceptibility to vancomycin.

A total of 207 Staphylococcus aureus strains, including 105 well-characterized strains with decreased susceptibility to vancomycin (17 vancomycin-intermediate S. aureus [VISA] and 88 heteroresistant VISA [hVISA] strains) and 102 wild-type methicillin-resistant S. aureus (MRSA-WT) strains were tested by reference/standardized broth microdilution and disk diffusion methods, as well as by Etest (AB BIODISK, Solna, Sweden), against daptomycin and vancomycin. The lowest concentration of antimicrobial agent that killed > or = 99.9% of the initial inoculum was defined as the minimum bactericidal concentration (MBC) endpoint, and time-kill curves were performed in selected strains to further evaluate bactericidal activity. All MRSA-WT and hVISA strains were inhibited by < or = 1 microg/ml of daptomycin, while the VISA strains showed slightly higher daptomycin MICs (range, 0.5 to 4 microg/ml). All daptomycin MBC results were at the MIC or twofold higher. In contrast, 14.7% of MRSA-WT, 69.3% of hVISA, and all VISA strains showed a vancomycin MBC/MIC ratio of > or = 32 or an MBC of > or = 16 microg/ml (tolerant). The correlation coefficients between broth microdilution and disk diffusion method results were low for daptomycin (0.07) and vancomycin (0.11). Eight (3.8%) strains (all hVISA or VISA) were "nonsusceptible" to daptomycin by broth microdilution methods but susceptible by the disk diffusion method. For vancomycin, 35 (16.9%) strains were nonsusceptible by broth microdilution methods but susceptible by disk diffusion methods. In conclusion, daptomycin was highly bactericidal against S. aureus strains, and its bactericidal activity was not affected by decreased susceptibility to vancomycin. In contrast, many (one in seven) contemporary MRSA-WT, the majority of hVISA, and all VISA strains showed vancomycin MBC/MIC ratios consistent with tolerance, a predictor of poor clinical response. Disk diffusion tests generally failed to detect strains categorized as nonsusceptible to daptomycin or vancomycin by the reference broth microdilution method or Etest, and reassessment of breakpoints should be immediately attempted for MIC methods suggested as the test of choice.

Anti-Bacterial Agents↗
PubMed2006

Comparison of censored regression and standard regression analyses for modeling relationships between antimicrobial susceptibility and patient- and institution-specific variables.

In order to identify patients likely to be infected with resistant bacterial pathogens, analytic methods such as standard regression (SR) may be applied to surveillance data to determine patient- and institution-specific factors predictive of an increased MIC. However, the censored nature of MIC data (e.g., MIC < or = 0.5 mg/liter or MIC > 8 mg/liter) imposes certain limitations on the use of SR. In order to investigate the nature of these limitations, simulations were performed to compare a regression tailored for censored data (censored regression [CR]) and one tailored for an SR. By using a model relating piperacillin-tazobactam MICs against Enterobacter spp. to patient age and hospital bed capacity, 200 simulations of 500 isolates were performed. Various MIC censoring patterns were imposed by using 26 left- or right-censored (L,R) pairs (i.e., MICs < or = 2 mg/liter(L) [2L] or MICs > 2 mg/liter(R) [2R], respectively). Data were fit by CR and SR for which censored MICs were either (i) excluded, (ii) replaced by 2L or 2R, or (iii) replaced by 2(L - 1) or 2(R + 1). Total censoring for the 26 pairs ranged from 7 to 86%. By CR, deviations of average parameter estimates from the true parameter values were <0.10 log2 (mg/liter) for all parameters for each of the 26 pairs. By SR, these deviations were >0.10 log2 (mg/liter) for at least 18 of the 26 pairs for all but one parameter. Two-standard-error confidence intervals for individual parameters contained as little as 0% of cases for all SR approaches but > or = 91.5% of cases for the CR approach. When censored MIC data are modeled, CR may reduce or eliminate biased parameter estimates obtained by SR.

Anti-Bacterial Agents↗
PubMed2006

Contemporary prevalence of BRO beta-lactamases in Moraxella catarrhalis: report from the SENTRY antimicrobial surveillance program (North America, 1997 to 2004).

A total of 7,860 community-acquired Moraxella catarrhalis isolates (SENTRY Antimicrobial Surveillance Program, 1997 to 2004) were tested by broth microdilution methods, and 399 randomly selected strains from North American sites were tested for BRO-1 and BRO-2 by PCR methods. Several antimicrobials remained very active, including amoxicillin-clavulanate (MIC90s, < or =0.25 microg/ml), azithromycin (MIC90s, < or =0.12 microg/ml), ceftriaxone (MIC90s, 0.5 microg/ml), and levofloxacin (MIC90s, < or =0.03 to 0.06 microg/ml). The BRO-2 incidence rates by year were 3 to 4% overall (96 to 97% for BRO-1) and were the highest in Canada (7.9%), with the incidence in the United States being only 2.0%.

Anti-Bacterial Agents↗
PubMed2006

Selection of a surrogate agent (vancomycin or teicoplanin) for initial susceptibility testing of dalbavancin: results from an international antimicrobial surveillance program.

The immediate lack of market-dominating commercial products (Vitek or MicroScan) for susceptibility testing of the new glycolipopeptide, dalbavancin, requires a surrogate marker agent to assist microbiologists in the correct categorization of potentially indicated species (staphylococci and streptococci). Error-rate analyses for 16,749 isolates using vancomycin or teicoplanin results to categorize dalbavancin susceptibilities demonstrated that both glycopeptide agents were highly predictive of dalbavancin-susceptible results (nearly 100%) with only a rare minor error. Vancomycin test results most reliably predict dalbavancin susceptibility until validated commercial reagents become available for direct testing in clinical practice.

Anti-Bacterial Agents↗
PubMed2006

Comparison of dalbavancin MIC values determined by Etest (AB BIODISK) and reference dilution methods using gram-positive organisms.

While standardized microdilution testing methodologies and quality control ranges exist for the novel glycolipopeptide dalbavancin, no testing methods have been described that are immediately available for routine use in clinical laboratories. In this study, we found that the dalbavancin Etest (AB BIODISK, Solna, Sweden) procedure demonstrated a high degree of agreement (100% within +/-2 log(2) dilution steps) with the standardized broth microdilution method, validating the use of the Etest as an alternative test for investigational or clinical purposes following regulatory approval.

Anti-Bacterial Agents↗
PubMed2006

Multicenter evaluation of the Etest and disk diffusion methods for differentiating daptomycin-susceptible from non-daptomycin-susceptible Staphylococcus aureus isolates.

Daptomycin is a novel cyclic lipopeptide that is approved by the U.S. Food and Drug Administration for the treatment of complicated skin and skin structure infections associated with Staphylococcus aureus and other gram-positive pathogens and also staphylococcal bacteremia, including right-sided endocarditis. The Clinical and Laboratory Standards Institute (CLSI) established "susceptible-only" interpretive criteria for broth microdilution (BMD) and disk diffusion (DD) testing of daptomycin in 2005. However, a series of S. aureus isolates have been recovered with daptomycin MICs in the nonsusceptible range (i.e., MICs of >1 microg/ml). The objective of this study was to determine the ability of the Etest and DD methods to differentiate daptomycin-susceptible from nonsusceptible isolates of S. aureus compared to the results of the CLSI BMD reference method. There was a good correlation between Etest MIC results and the results of BMD among laboratories (r = 0.86 to 0.88), with 95.3% of the Etest MICs within a +/-1 log(2) dilution of the BMD MIC result. A total of 92 of 102 (90.2%) non-daptomycin-susceptible isolates of S. aureus identified by BMD in two participating laboratories were also classified as nonsusceptible by Etest. However, the very major and major error rates reported by one of the participating laboratories were 13.5 and 4.0%, respectively, primarily due to the absence of an intermediate category. The DD method, however, did not reliably differentiate daptomycin-susceptible from non-daptomycin-susceptible isolates. In 2005, daptomycin disks were voluntarily removed from the market by Cubist Pharmaceuticals. The disk diffusion breakpoints were subsequently removed from the CLSI M100 standard in 2006.

Anti-Bacterial Agents↗
PubMed2006

Accuracy of three automated systems (MicroScan WalkAway, VITEK, and VITEK 2) for susceptibility testing of Pseudomonas aeruginosa against five broad-spectrum beta-lactam agents.

One hundred recent clinical Pseudomonas aeruginosa isolates were used to assess the quantitative (MIC) and qualitative (susceptibility category) accuracies of the MicroScan WalkAway, VITEK, and VITEK 2 automated susceptibility test systems when five-broad spectrum beta-lactams, aztreonam, cefepime, ceftazidime, imipenem, and piperacillin-tazobactam, were tested. Isolates were selected so that the MICs for the isolates overrepresented the MICs near the breakpoints to assess precisely the agreement between the results obtained with the automated systems and the results obtained by the reference tests. The categorical and MIC results from the automated systems were compared to the consensus result of three reference methods: broth microdilution, agar dilution, and disk diffusion. The consensus categorical testing (susceptibility and resistance) rates were 47 and 27%, respectively, for aztreonam; 59 and 14%, respectively, for cefepime; 44 and 43%, respectively, for ceftazidime; 71 and 19%, respectively, for imipenem; and 50 and 50%, respectively, for piperacillin-tazobactam. All systems tested exhibited a high, unacceptable level of very major (false-susceptible) errors for piperacillin-tazobactam (19 to 27%). Major (false-resistant) error rates were generally acceptable (0 to 3%), but minor error rates were elevated (8 to 32%) for cefepime (VITEK 2 and VITEK) and for aztreonam (all three systems), leading to consistent trends toward false resistance. Manufacturer reevaluation of these automated systems for the testing of selected beta-lactams with current clinical isolates of P. aeruginosa that exhibit contemporary resistance mechanisms would be prudent to minimize the potential for serious reporting errors.

Bacteriological Techniques↗
PubMed2006

International surveillance of Candida spp. and Aspergillus spp.: report from the SENTRY Antimicrobial Surveillance Program (2003).

During 2003, a total of 1,397 Candida isolates, 73 Aspergillus isolates, 53 Cryptococcus neoformans isolates, and 25 other fungal isolates from infected, normally sterile, body sites in patients hospitalized in North America, Europe, and Latin America were studied as a component of the longitudinal SENTRY Antimicrobial Surveillance Program. The MICs for seven antifungal agents were determined in a central laboratory (JMI Laboratories, North Liberty, IA) using testing methods promulgated by the Clinical and Laboratory Standards Institute (formerly the National Committee for Clinical Laboratory Standards). The rank order of Candida spp. occurrence was as follows: C. albicans (48.7%), C. parapsilosis (17.3%), C. glabrata (17.2%), C. tropicalis (10.9%), C. krusei (1.9%), and other Candida spp. (4.0%). C. albicans accounted for 51.5, 47.8, and 36.5% of candidal infections in North America, Europe, and Latin America, respectively. Ravuconazole, voriconazole, and fluconazole were highly active against C. albicans, C. parapsilosis, and C. tropicalis, with both former agents being more potent (MIC at which 90% of the isolates tested are inhibited [MIC90] of < or =0.008 to 0.12 microg/ml) than fluconazole (MIC90 of 0.5 to 2 microg/ml). C. glabrata isolates were less susceptible to these agents, with MIC90s of 1, 1, and 64 microg/ml, respectively. Ravuconazole and voriconazole were the most active agents tested against C. krusei (MIC90 of 0.5 microg/ml). Among Aspergillus spp., A. fumigatus was the most commonly (71.2% of isolates) recovered species; 96.2, 96.2, 84.6, and 11.5% of strains were inhibited by < or =1 microg/ml of ravuconazole, voriconazole, itraconazole, and amphotericin B, respectively. Of the antifungal agents tested, ravuconazole and voriconazole displayed the greatest spectrum of activity against pathogenic Candida and Aspergillus spp., regardless of geographic origin. These results extend upon previous findings from SENTRY Program reports (1997 to 2000), further characterizing species composition as seen in local clinical practice and demonstrating the potent activity of selected, newer triazole antifungal agents.

Antifungal Agents↗
PubMed2006

Increased resistance to first-line agents among bacterial pathogens isolated from urinary tract infections in Latin America: time for local guidelines?

Emerging resistance phenotypes and antimicrobial resistance rates among pathogens recovered from community-acquired urinary tract infections (CA-UTI) is an increasing problem in specific regions, limiting therapeutic options. As part of the SENTRY Antimicrobial Surveillance Program, a total of 611 isolates were collected in 2003 from patients with CA-UTI presenting at Latin American medical centers. Each strain was tested in a central laboratory using Clinical Laboratory Standard Institute (CLSI) broth microdilution methods with appropriate controls. Escherichia coli was the leading pathogen (66%), followed by Klebsiella spp. (7%), Proteus mirabilis (6.4%), Enterococcus spp. (5.6%), and Pseudomonas aeruginosa (4.6%). Surprisingly high resistance rates were recorded for E. coli against first-line orally administered agents for CA-UTI, such as ampicillin (53.6%), TMP/SMX (40.4%), ciprofloxacin (21.6%), and gatifloxacin (17.1%). Decreased susceptibility rates to TMP/SMX and ciprofloxacin were also documented for Klebsiella spp. (79.1 and 81.4%, respectively), and P. mirabilis (71.8 and 84.6%, respectively). For Enterococcus spp., susceptibility rates to ampicillin, chloramphenicol, ciprofloxacin, and vancomycin were 88.2, 85.3, 55.9, and 97.1%, respectively. High-level resistance to gentamicin was detected in 24% of Enterococcus spp. Bacteria isolated from patients with CA-UTI in Latin America showed limited susceptibility to orally administered antimicrobials, especially for TMP/SMX and fluoroquinolones. Our results highlight the need for developing specific CA-UTI guidelines in geographic regions where elevated resistance to new and old compounds may influence prescribing decisions.

Adult↗
PubMed2006

Performance accuracy of antibacterial and antifungal susceptibility test methods: report from the College of American Pathologists Microbiology Surveys Program (2001-2003).

CONTEXT: The College of American Pathologists Microbiology Surveys Program provides external proficiency samples that monitor the performance of nearly 3000 laboratories that perform and report antimicrobial susceptibility tests. OBJECTIVE: To summarize results obtained with bacterial and yeast challenge samples (2001 through 2003). DESIGN: One organism every 4 months was tested by surveys participants against antibacterials/antifungals by routinely used methods. Reports were graded by interpretive category (susceptible, intermediate, resistant) based on an 80% consensus of referees/participants. RESULTS: The most common antibacterial test methods/systems were Vitek (38%-43%), MicroScan (39%-43%), and the disk diffusion test (14%-15%), although Etest was most used for fastidious species. YeastOne was the dominant antifungal test (50%-55%). Antifungal results demonstrated continuous, improved accuracy (83%-88%), highest for YeastOne (96%) and broth microdilution (95%) methods. Antibacterial test accuracy was consistently greater than 97% against gram-positive organism challenges and greater than 98% against gram-negative challenges. For gram-negative strains with well-characterized resistance mechanisms, the accuracy by method was disk diffusion greater than broth microdilution greater than automated systems. Major problems identified were (1) Haemophilus influenzae control ranges require re-evaluation, (2) overuse of beta-lactamase tests, (3) errors among Enterococcus faecium against penicillins (Vitek 2, MicroScan), (4) false-susceptible results with trimethoprim/sulfamethoxazole against coagulase-negative staphylococci (MicroScan), (5) macrolide false-susceptibility for beta-hemolytic streptococcus (MicroScan), (6) flawed reporting for antimicrobials not active at the infection site, (7) use of outdated interpretive criteria, and (8) failure to follow Clinical and Laboratory Standards Institute testing/reporting recommendations. CONCLUSIONS: Susceptibility tests were generally performing satisfactorily as measured by the surveys, but serious errors were identified with some drug/organism combinations that may require action by the Clinical and Laboratory Standards Institute and/or the Food and Drug Administration.

Anti-Bacterial Agents↗
PubMed2005

Oxazolidinone susceptibility patterns in 2004: report from the Zyvox Annual Appraisal of Potency and Spectrum (ZAAPS) Program assessing isolates from 16 nations.

OBJECTIVES: To investigate the activity of linezolid (an oxazolidinone), a potent choice for community- and hospital-acquired infections, via a worldwide surveillance network called the Zyvox Annual Appraisal of Potency and Spectrum (ZAAPS) Program. METHODS: A total of 4098 Gram-positive strains were collected from 42 laboratories located in North America (five sites in Canada), South America (10 sites), Europe (16 sites) and the Far East (11 sites). Each country or site submitted 200 isolates (Canada submitted 200 isolates for each of five sites; total 1000) for confirmation of organism identification and reference MIC processing. Nearly 25 comparator agents were tested along with quality control strains, and interpretative criteria from the CLSI, formerly the NCCLS, M100-S15 were applied. No linezolid resistance was detected in strains from 16 monitored countries in 2004. RESULTS: Linezolid remained highly active against Streptococcus pneumoniae, viridans group and beta-haemolytic streptococci (MIC90, 1 mg/L). Against Staphylococcus aureus, linezolid showed 99.5% of results at 0.5-2 mg/L with only one isolate at 4 mg/L. Oxacillin-resistant S. aureus rates varied between nations and ranged from 1.4% in Sweden to 29.5% in the UK to 65.2% in Mexico. Linezolid MIC values were generally one log2 dilution step lower for coagulase-negative staphylococci (CoNS) when compared with S. aureus. No CoNS strains produced a linezolid result at 4 mg/L. Compared with ZAAPS 2002 and 2003 results for enterococci where seven resistant strains were identified, the 2004 data revealed no resistance and 98.1% of linezolid MIC results were at 1 or 2 mg/L. Vancomycin-resistant enterococci (5.3% overall) varied markedly by country including a high of 47.2% in Korea. CONCLUSIONS: Linezolid continues to be effective in vitro against Gram-positive pathogens from five continents and no oxazolidinone-resistant strains were identified among the 4098 systemically collected strains (2004) or among 20 158 non-United States isolates for the entire ZAAPS Program (2002-04).

Acetamides↗
PubMed2005

Analysis of Salmonella spp. with resistance to extended-spectrum cephalosporins and fluoroquinolones isolated in North America and Latin America: report from the SENTRY Antimicrobial Surveillance Program (1997-2004).

Emerging antimicrobial-resistant Salmonella spp. requires increased efforts to appropriately test susceptibility. The SENTRY Antimicrobial Surveillance Program monitored Salmonella spp. and detected nalidixic acid-resistant strains with elevated fluoroquinolone minimum inhibitory concentration (MIC) results and strains with extended-spectrum beta-lactamase (ESBL) "phenotypes" over the last 8 years. A total of 786 stool and bloodstream isolates from North American and Latin American medical centers (2001-2003) were tested by reference broth microdilution methods. Genetic analysis was used to further characterize the resistance mechanisms. Twenty-one sites forwarded 89 (11.3%) nalidixic acid-resistant (MIC, > or =32 microg/mL) strains. Nineteen of these isolates were studied to determine mutations in the quinolone resistance-determining region (QRDR). Among the nalidixic acid-resistant Salmonella spp. isolates, fluoroquinolone MIC values were also elevated (8- to 32-fold) compared with "wild-type" strains. Ciprofloxacin and gatifloxacin (MIC(90), 0.5 microg/mL) were more potent than levofloxacin and garenoxacin (1 microg/mL) against nalidixic acid-resistant strains. Single gyrA mutations were responsible for elevated fluoroquinolone MIC values and included D87Y (5), S83F (7), D87N (5), and S83Y (2). During 2001, 9 sites contributed 11 (2.9%) strains that met ESBL screening criteria (> or =2 microg/mL) for aztreonam or ceftazidime or ceftriaxone. ESBL confirmation was evaluated by Etest (AB BIODISK, Solna, Sweden) ESBL strips and the enzymes were characterized by polymerase chain reaction and gene sequencing. The ESBL phenotype isolates had the following MIC patterns: ceftazidime (> or =16 microg/mL), aztreonam (4 to >16 microg/mL), and ceftriaxone (8-32 microg/mL). All strains were susceptible to cefepime, carbapenems, gentamicin, and fluoroquinolones. No strains were inhibited by clavulanic acid consistent with all isolates producing the identified CMY-2, AmpC-like enzyme. Fluoroquinolones may be compromised among isolates with QRDR mutations detected using nalidixic acid as a screening agent. Salmonella spp. with ESBL phenotypes were likely to harbor CMY-2 (not an ESBL) and remain susceptible to cefepime, carbapenems, and fluoroquinolones, which can be used for serious invasive Salmonella spp. infections. Compared with the stool culture isolates, the blood culture isolates had higher QRDR mutations, but remained susceptible to the fluoroquinolones. The blood culture isolates were more susceptible to penicillins (ampicillin and ticarcillin) and not significantly different for ceftriaxone or trimethoprim/sulfamethoxazole susceptibility patterns. No QRDR trends over time were detected in North America, but increased resistance was observed in Latin America.

Anti-Bacterial Agents↗
PubMed2005

Antimicrobial susceptibility patterns of unusual nonfermentative gram-negative bacilli isolated from Latin America: report from the SENTRY Antimicrobial Surveillance Program (1997-2002).

The antimicrobial susceptibility of 176 unusual non-fermentative gram-negative bacilli (NF-GNB) collected from Latin America region through the SENTRY Program between 1997 and 2002 was evaluated by broth microdilution according to the National Committee for Clinical Laboratory Standards (NCCLS) recommendations. Nearly 74% of the NF-BGN belonged to the following genera/species: Burkholderia spp. (83), Achromobacter spp. (25), Ralstonia pickettii (16), Alcaligenes spp. (12), and Cryseobacterium spp. (12). Generally, trimethoprim/sulfamethoxazole (MIC50, < 0.5 microg/ml) was the most potent drug followed by levofloxacin (MIC50, 0.5 microg/ml), and gatifloxacin (MIC50, 1 microg/ml). The highest susceptibility rates were observed for levofloxacin (78.3%), gatifloxacin (75.6%), and meropenem (72.6%). Ceftazidime (MIC50, 4 microg/ml; 83.1% susceptible) was the most active beta-lactam against B. cepacia. Against Achromobacter spp. isolates, meropenem (MIC50, 0.25 microg/ml; 88% susceptible) was more active than imipenem (MIC50, 2 microg/ml). Cefepime (MIC50, 2 microg/ml; 81.3% susceptible), and imipenem (MIC50, 2 microg/ml; 81.3% susceptible) were more active than ceftazidime (MIC50, >16 microg/ml; 18.8% susceptible) and meropenem (MIC50, 8 microg/ml; 50% susceptible) against Ralstonia pickettii. Since selection of the most appropriate antimicrobial agents for testing and reporting has not been established by the NCCLS for many of NF-GNB species, results from large multicenter studies may help to guide the best empiric therapy.

Anti-Bacterial Agents↗