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G V Doern

Publications and source records attributed to G V Doern.

At least 73 records · Page 4Linked to original sources
PubMed1998

Comparative antimicrobial activity of trovafloxacin tested against 3049 Streptococcus pneumoniae isolates from the 1997-1998 respiratory infection season.

Trovafloxacin is a new fluorinated naphthyridone having expanded activity against Gram-positive and anaerobic pathogens compared with ciprofloxacin or levofloxacin or ofloxacin. A multicenter in vitro trial (201 sites) was initiated in late 1997 to study the comparative activity of trovafloxacin against Streptococcus pneumoniae strains during the recently completed respiratory disease season. Each laboratory was asked to test 20 to 30 recent isolates (3049 strains) by the Etest (AB BIODISK, Solna, Sweden) method with observed phenotypes with elevated trovafloxacin results (MIC, > 1 microgram/mL) confirmed by the monitor laboratory (University of Iowa College of Medicine). Approximately one-third (34.0%) of isolates were penicillin nonsusceptible (12.8% high-level resistance at > or = 2 micrograms/mL). Also 20.4% and 4.5% of strains were resistant to macrolides (erythromycin) and ceftriaxone, respectively. The macrolide resistance rate was lowered to 16.8% when the adverse effect of CO2 incubation was considered. Only 0.3% of S. pneumoniae were vancomycin-nonsusceptible using the current National Committee for Clinical Laboratory Standards breakpoint (< or = 1 microgram/mL) with nearly all results were at 1.5 micrograms/mL. Trovafloxacin (MIC50 and MIC90, 0.094 and 0.19 microgram/mL, respectively) was eight fold more potent than levofloxacin (MIC90, 0.75 and 1.5 micrograms/mL), and fewer strains (0.10%) were discovered with high-level resistance (MIC, > or = 8 micrograms/mL). The four resistant isolates from different states had alterations in both par C and gyr A. Trovafloxacin had the best potency observed against contemporary pneumococcal isolates, and has a spectrum (> 99.8% susceptible) for an orally administered agent that was comparable to the tested parenteral glycopeptide, vancomycin (> 99.7%). Blood and spinal-fluid culture isolates were generally more susceptible to penicillin (74.4 to 75.6%), other beta-lactams, and erythromycin (84.4%); throat and sputum isolates were significantly more resistant (p < 0.01). Increases in resistance among S. pneumoniae strains to beta-lactams and erythromycin were documented in all geographic regions monitored, other resistances also continue to evolve, and high-level fluoroquinolone resistance remains very rare.

Anti-Bacterial Agents↗
PubMed1998

The prevalence of fluoroquinolone resistance among clinically significant respiratory tract isolates of Streptococcus pneumoniae in the United States and Canada--1997 results from the SENTRY Antimicrobial Surveillance Program.

As part of the SENTRY antimicrobial resistance surveillance program, a total of 1100 clinically significant respiratory tract isolates of Streptococcus pneumoniae were tested for susceptibility to six fluoroquinolone antimicrobial agents: ciprofloxacin, levofloxacin, gatifloxacin, grepafloxacin, sparfloxacin, and trovafloxacin. Isolates were obtained during the 5-month period, February to June, 1997 from 27 United States medical center laboratories and seven laboratories in Canadian health care institutions. All testing was performed in a single center. Of 1100 test strains, 3 (0.3%), all from different U.S. centers, were fluoroquinolone resistant. Among the remaining 1097 fluoroquinolone-susceptible isolates, the rank order of activity among the six agents tested in this study was grepafloxacin (modal MIC = 0.25 microgram/mL) = trovafloxacin (modal MIC = 0.25 microgram/mL) = sparfloxacin (0.25 microgram/mL) > gatifloxacin (0.5 microgram/mL) > levofloxacin (1 microgram/mL) = ciprofloxacin (1 microgram/mL). Fluoroquinolone resistance is currently uncommon among respiratory tract isolates of S. pneumoniae in North America, but there exist clear differences between the in vitro activities of different fluoroquinolones for this organism.

Anti-Infective Agents↗
PubMed1998

Fluoroquinolone-resistant Moraxella catarrhalis in a patient with pneumonia: report from the SENTRY Antimicrobial Surveillance Program (1998).

Fluoroquinolone resistance in Moraxella catarrhalis isolates has been quite rare. This report presents a case history of a 22-year-old man with compromised immune status and severe pneumonia caused by M. catarrhalis. The organism was markedly resistant (MICs, 1.5- > 32 micrograms/mL) to several marketed fluoroquinolones including the agent (levofloxacin) used for concurrent and prior therapy. The emergence of this problematic strain seems related to chronic exposure of the patient to compounds in the class and poor patient compliance to prescribed medications. The strain was not clonally related to other M. catarrhalis strains isolated in the same hospital during early 1998. This second documented case of a fluoroquinolone-resistant M. catarrhalis clinical isolate presents a warning that resistances can emerge in at-risk patients, and that surveillance systems (SENTRY) will be necessary to monitor for unusual organisms and spread of resistance phenotypes among commonly isolated respiratory tract pathogens.

Adult↗
PubMed1998

Antimicrobial activity of gatifloxacin tested against 1676 strains of ciprofloxacin-resistant gram-positive cocci isolated from patient infections in North and South America.

Gatifloxacin (formerly AM-115) is a new 8-methoxy fluoroquinolone with an expanded spectrum against Gram-positive cocci and some anaerobes. To assess this new agent's activity, a collection of 1,676 Gram-positive cocci were selected for resistance to ciprofloxacin (> or = 4 micrograms/mL) and tested against gatifloxacin and 18 other compounds by reference broth microdilution methods. The strains (approximately 23,000 total isolates from the SENTRY Antimicrobial Surveillance Program) were from significant blood stream, respiratory tract, wound, and urinary tract infections in patients in North (38 hospitals) and South (10 hospitals) America. Against Enterococcus faecalis and E. faecium, gatifloxacin inhibited only 16% and 10% of strains compared with 12% and 5% for recently released trovafloxacin, respectively. Among Staphylococcus aureus (90% oxacillin-resistant) strains, gatifloxacin was more active (67% susceptible at < or = 4 micrograms/mL) than trovafloxacin (59%) or sparfloxacin (4%). Gatifloxacin had a wider spectrum than trovafloxacin against coagulase-negative staphylococci especially S. epidermidis, 2% versus 58% resistance. The glycopeptides, chloramphenicol and rifampin were most active. Against all genus/species groups with more than 100 sample strains (1,566), high-level resistance to gatifloxacin and trovafloxacin (> 4 micrograms/mL) was not significantly different (41.7% versus 39.1%; p > 0.05). Emerging resistance to the fluoroquinolones remains a clinical problem among Gram-positive species, and gatifloxacin seems to be active in vitro against many of these contemporary strains isolated in the Americas.

Anti-Infective Agents↗
PubMed1998

Antimicrobial susceptibility patterns for pathogens isolated from patients in Latin American medical centers with a diagnosis of pneumonia: analysis of results from the SENTRY Antimicrobial Surveillance Program (1997). SENTRY Latin America Study Group.

Pneumonia is the most common fatal hospital-acquired infection, with attributable mortality rates ranging from 30 to 60%. Rapid initiation of optimal antimicrobial therapy is essential for obtaining treatment success. In this report the antimicrobial susceptibility of 556 strains from the lower respiratory tract were collected by the SENTRY Antimicrobial Surveillance Program (1997). These strains were isolated from hospitalized patients with pneumonia in 10 Latin American centers (6 countries) as part of this 68-center worldwide program. The isolates were susceptibility tested against more than 70 drugs (35 reported) by the reference broth microdilution method. Klebsiella pneumoniae and Escherichia coli phenotypically consistent with extended spectrum beta-lactamase (ESBL) production were characterized further by ribotyping and pulsed-field gel electrophoresis. The five most frequently isolated species were (n/%): Pseudomonas aeruginosa (149/26.8%), Staphylococcus aureus (127/22.8%), Acinetobacter spp. (66/11.9%), Klebsiella spp. (56/10.1%), and Enterobacter spp. (40/7.2%). P. aeruginosa demonstrated high rates of resistance to a majority of the antimicrobial drugs tested. Carbapenems, amikacin, and piperacillin/tazobactam demonstrated the highest susceptibility rates (73.8-77.2%) against P. aeruginosa, however the lowest resistance rate was observed for cefepime (6.7%). Acinetobacter spp. also showed very high rates of resistance and the most active compounds were imipenem and meropenem (89.0% susceptibility) followed by the tetracyclines. Cephalosporin susceptibilities among Klebsiella spp. were low: cefoxitin, 73.0%; ceftazidime, 69.4%; and ceftriaxone, 65.9%. Approximately 37% and 28% of K. pneumoniae and E. coli isolates, respectively, were considered ESBL producers based on NCCLS criteria. Ceftriaxone was active against only 52.5% of Enterobacter spp. isolates, whereas cefepime was active against 90.0% of isolates (MIC50, < or = 0.12 microgram/mL). Oxacillin resistance was detected in nearly 50% of S. aureus isolates. The most active drugs against S. aureus were vancomycin, teicoplanin, and quinupristin/dalfopristin (MIC90, 1 microgram/mL). In summary, our study of pneumonias in Latin American medical centers demonstrated a greatly increased prevalence of Acinetobacter spp. and higher resistance rates among Gram-negative bacilli when compared with similar controlled studies from North America.

Anti-Bacterial Agents↗
PubMed1998

Clonal relationships among high-level penicillin-resistant Streptococcus pneumoniae in the United States.

During the past 6 to 7 years, the problem of antimicrobial resistance in Streptococcus pneumoniae has grown dramatically in the United States. Currently, approximately 26.5% of pneumococcal isolates express intermediate levels of resistance to penicillin; approximately 17.5% are highly penicillin resistant. We studied whether clonal relationships exist among current isolates of high-level penicillin-resistant S. pneumoniae (PRSP) in the United States. One hundred forty-seven PRSP isolates recovered in a 30-center surveillance study in the United States during 1994-1995 were characterized with respect to serotype, antimicrobial susceptibility pattern, and pulsed-field gel electrophoresis (PFGE) profile. Only six serotypes were observed among the 147 PRSP isolates examined in this study: 6A, 6B, 9A, 14, 19F, and 23F. One hundred three (70.1%) of the 147 strains were characterized by one of only nine PFGE types; 76 (51.7%) of the 147 isolates were characterized by only four PFGE profiles. Currently in the United States, most PRSP strains are represented by relatively few clonal groups.

DNA, Bacterial↗
PubMed1998

Prevalence of antimicrobial resistance among respiratory tract isolates of Streptococcus pneumoniae in North America: 1997 results from the SENTRY antimicrobial surveillance program.

As part of the ongoing multinational SENTRY antimicrobial resistance surveillance program, a total of 1,047 respiratory tract isolates of Streptococcus pneumoniae, 845 from 27 United States medical centers and 202 from seven Canadian institutions, were collected between February and June 1997 and characterized in a central laboratory. In the United States, the overall percentages of penicillin-intermediate strains and strains with high-level resistance to penicillin were 27.8% and 16.0%, respectively. In Canada, these values were 21.8% and 8.4%, respectively. Among the 31 centers in the United States and Canada that contributed at least 19 isolates, the combined rate of intermediate plus resistant strains varied between 24.0% and 67.8%. The in vitro activity of 19 other antimicrobials was assessed against all study isolates. Overall rates of resistance among selected agents in the United States and Canada, respectively, were as follows: amoxicillin, 18.1% and 10.5%; cefaclor, 38.3% and 26.2%; cefuroxime, 19.5% and 12.9%; cefpodoxime, 18.6% and 11.4%; cefepime, 8.2% and 4.5%; cefotaxime, 4.0% and 3.0%; macrolides (i.e., erythromycin, azithromycin, and clarithromycin), 11.7%-14.3% and 5.0%-7.4%; clindamycin, 3.5% and 3.5%; chloramphenicol, 3.9% and 4.0%; tetracycline, 10.2% and 10.9%; and trimethoprim-sulfamethoxazole, 19.8% and 15.8%.

Drug Resistance, Microbial↗
PubMed1998

Partial liquid ventilation with perfluorocarbon in the treatment of rats with lethal pneumococcal pneumonia.

BACKGROUND: Partial liquid ventilation with perfluorocarbon is a new therapeutic strategy to treat various lung disorders. The current study was undertaken to determine the efficacy of partial liquid ventilation with a perfluorocarbon (FC-77) in the treatment of pneumococcal pneumonia in rats. METHODS: Male Wistar rats (weight, 275-300 g; n, 75) were infected via direct intratracheal inoculation with ca 10(9) colony-forming units of viable Streptococcus pneumoniae, serotype 3, and 24 h after infection were placed into one of five groups, each containing 15 rats. The groups were (1) no treatment, (2) one intramuscular injection of penicillin G benzathine (200,000 U), (3) partial liquid ventilation with FC-77, (4) partial liquid ventilation with FC-77 and a single intramuscular dose of penicillin G benzathine (200,000 U), and (5) gas ventilation. Animals were observed every 24 h for survival. RESULTS: All untreated or gas-ventilated animals or animals that received only partial liquid ventilation were dead by 7 days. Those receiving only partial liquid ventilation survived longer than untreated controls, but ultimately all succumbed by day 7. Survival was 40% for penicillin-treated rats compared with controls (P < 0.05) and 80% for animals treated with both partial liquid ventilation and penicillin versus antibiotic alone (P < 0.05). CONCLUSIONS: These observations suggest that partial liquid ventilation with perfluorocarbon in combination with antibiotic administration may be an effective therapeutic modality in pneumococcal pneumonia.

Animals↗
PubMed1998

In vitro susceptibilities of Candida bloodstream isolates to the new triazole antifungal agents BMS-207147, Sch 56592, and voriconazole.

BMS-207147, Sch 56592, and voriconazole are three new investigational triazoles with broad-spectrum antifungal activity. The in vitro activities of these three agents were compared with those of itraconazole and fluconazole against 1,300 bloodstream isolates of Candida species obtained from over 50 different medical centers in the United States. The MICs of all of the antifungal drugs were determined by broth microdilution tests performed according to the National Committee for Clinical Laboratory Standards method using RPMI 1640 as a test medium. BMS-207147, Sch 56592, and voriconazole were all quite active against all Candida sp. isolates (MICs for 90% of the isolates tested [MIC90s], 0.5, 1.0, and 0.5 microgram/ml, respectively). Candida albicans was the most susceptible species (MIC90s, 0.03, 0.06, and 0.06 microgram/ml, respectively), and C. glabrata was the least susceptible (MIC90s, 4. 0, 4.0, and 2.0 microgram/ml, respectively). BMS-207147, Sch 56592, and voriconazole were all more active than itraconazole and fluconazole against C. albicans, C. parapsilosis, C. tropicalis, and C. krusei. There existed a clear rank order of in vitro activity of the five azoles examined in this study when they were tested versus C. glabrata: voriconazole > BMS-207147 = Sch 56592 = itraconazole > fluconazole (MIC90s, 2.0, 4.0, 4.0, 4.0, and 64 microgram/ml, respectively). For isolates of Candida spp. with decreased susceptibility to both itraconazole and fluconazole, the MICs of BMS-207147, Sch 56592, and voriconazole were also elevated. These results suggest that BMS-207147, Sch 56592, and voriconazole all possess promising antifungal activity and that further in vitro and in vivo investigations are warranted to establish the clinical value of this improved potency.

Antifungal Agents↗
PubMed1998

Bacterial pathogens isolated from patients with bloodstream infection: frequencies of occurrence and antimicrobial susceptibility patterns from the SENTRY antimicrobial surveillance program (United States and Canada, 1997).

The SENTRY Program was established in January 1997 to measure the predominant pathogens and antimicrobial resistance patterns of nosocomial and community-acquired infections over a broad network of sentinel hospitals in the United States (30 sites), Canada (8 sites), South America (10 sites), and Europe (24 sites). During the first 6-month study period (January to June 1997), a total of 5,058 bloodstream infections (BSI) were reported by North American SENTRY participants (4,119 from the United States and 939 from Canada). In both the United States and Canada, Staphylococcus aureus and Escherichia coli were the most common BSI isolates, followed by coagulase-negative staphylococci and enterococci. Klebsiella spp., Enterobacter spp., Pseudomonas aeruginosa, Streptococcus pneumoniae, and beta-hemolytic streptococci were also among the 10 most frequently reported species in both the United States and Canada. Although the rank orders of pathogens in the United States and Canada were similar, distinct differences were noted in the antimicrobial susceptibilities of several pathogens. Overall, U.S. isolates were considerably more resistant than those from Canada. The differences in the proportions of oxacillin-resistant S. aureus isolates (26.2 versus 2.7% for U.S. and Canadian isolates, respectively), vancomycin-resistant enterococcal isolates (17.7 versus 0% for U.S. and Canadian isolates, respectively), and ceftazidime-resistant Enterobacter sp. isolates (30.6 versus 6.2% for U.S. and Canadian isolates, respectively) dramatically emphasize the relative lack of specific antimicrobial resistance genes (mecA, vanA, and vanB) in the Canadian microbial population. Among U.S. isolates, resistance to oxacillin among staphylococci, to vancomycin among enterococci, to penicillin among pneumococci, and to ceftazidime among Enterobacter spp. was observed in both nosocomial and community-acquired pathogens, although in almost every instance the proportion of resistant strains was higher among nosocomial isolates. Antimicrobial resistance continues to increase, and ongoing surveillance of microbial pathogens and resistance profiles is essential on national and international scales.

Anti-Bacterial Agents↗
PubMed1998

Use of molecular and reference susceptibility testing methods in a multicenter evaluation of MicroScan dried overnight gram-positive MIC panels for detection of vancomycin and high-level aminoglycoside resistances in enterococci.

Modified MicroScan gram-positive MIC no. 8 panels (PM-8) were analyzed for their improved ability to detect vancomycin resistance (VR) and high-level aminoglycoside resistance (HLAR) in enterococci. A validation study design that utilized selected challenge strains, recent clinical isolates, and reproducibility experiments in a multicenter format was selected. Three independent medical centers compared the commercial panels to reference broth microdilution panels (RBM) and Synergy Quad Agar (QA). Resistance was verified by demonstration of VR and HLAR genes by PCR tests. The study was conducted in three phases. (i) In the challenge phase (CP), two well-characterized sets of enterococci were obtained from the Centers for Disease Control and Prevention; one set contained 50 isolates for VR testing and one contained 48 isolates for HLAR testing. In addition, a set of 47 well-characterized isolates representing diverse geographic areas, obtained from earlier national surveillance studies, was tested at the University of Iowa College of Medicine (UICM). (ii) In the efficacy phase (EP), each laboratory tested 50 recent, unique clinical isolates by all methods. (iii) In the reproducibility Phase (RP), each laboratory tested the same 10 strains by all methods in triplicate on three separate days. All isolates from the EP were sent to the UICM for molecular characterization of vanA, -B, -C1, -C2-3, and HLAR genes. In the CP, the ranking of test methods by error rates (in parentheses; very major and major errors combined, versus PCR results) were as follows: for high-level streptomycin resistance (HLSR), QA (12.0%) > PM-8 (5.2%) > RBM (1.6%); for high-level gentamicin resistance (HLGR), RBM (3.7%) > PM-8 (3.1%) > QA (2.6%); and for VR, RBM = QA (3.0%) > PM-8 (1.2%). In the EP, agreement between all methods and the reference PCR result was 98.0% for HLSR, 99.3% for HLGR, and 98. 6% for VR. In the RP, the percentages of results +/- 1 log2 dilution of the all-participant mode were as follows: for VR, 100% (PM-8), 98.9% (QA), and 90.0% (RBM); for HLSR, 99.6% (RBM), 98.5% (PM-8), and 82.2% (QA); and for HLGR, 99.6% (RBM), 99.3% (PM-8), and 98.1% (QA). The ability of the PM-8 to detect VR and HLAR in enterococci was comparable to those for reference susceptibility and molecular PCR methods and was considered acceptable for routine clinical laboratory use.

Anti-Bacterial Agents↗
PubMed1998

International surveillance of bloodstream infections due to Candida species: frequency of occurrence and antifungal susceptibilities of isolates collected in 1997 in the United States, Canada, and South America for the SENTRY Program. The SENTRY Participant Group.

An international program of surveillance of bloodstream infections (BSIs) in the United States, Canada, and South America between January and December 1997 detected 306 episodes of candidemia in 34 medical centers (22 in the United States, 6 in Canada, and 6 in South America). Eighty percent of the BSIs were nosocomial and 50% occurred in patients hospitalized in an intensive care unit. Overall, 53.3% of the BSIs were due to Candida albicans, 15.7% were due to C. parapsilosis, 15.0% were due to C. glabrata, 7.8% were due to C. tropicalis, 2.0% were due to C. krusei, 0.7% were due to C. guilliermondii, and 5.8% were due to Candida spp. However, the distribution of species varied markedly by country. In the United States, 43.8% of BSIs were due to non-C. albicans species. C. glabrata was the most common non-C. albicans species in the United States. The proportion of non-C. albicans BSIs was slightly higher in Canada (47.5%), where C. parapsilosis, not C. glabrata, was the most common non-C. albicans species. C. albicans accounted for 40.5% of all BSIs in South America, followed by C. parapsilosis (38.1%) and C. tropicalis (11.9%). Only one BSI due to C. glabrata was observed in South American hospitals. Among the different species of Candida, resistance to fluconazole (MIC, > or = 64 microg/ml) and itraconazole (MIC, > or = 1.0 microg/ml) was observed with C. glabrata and C. krusei and was observed more rarely among other species. Isolates of C. albicans, C. parapsilosis, C. tropicalis, and C. guilliermondii were all highly susceptible to both fluconazole (99.4 to 100% susceptibility) and itraconazole (95.8 to 100% susceptibility). In contrast, 8.7% of C. glabrata isolates (MIC at which 90% of isolates are inhibited [MIC90], 32 microg/ml) and 100% of C. krusei isolates were resistant to fluconazole, and 36.9% of C. glabrata isolates (MIC90, 2.0 microg/ml) and 66.6% of C. krusei isolates were resistant to itraconazole. Within each species there were no geographic differences in susceptibility to fluconazole or itraconazole.

Antifungal Agents↗
PubMed1998

Controlled comparative evaluation of BacT/Alert FAN and ESP 80A aerobic media as means for detecting bacteremia and fungemia.

During a one-year period, a total of 6,305 blood cultures were processed in a tertiary-care teaching hospital; 6 to 12 ml of blood was inoculated into both a BacT/Alert Fan aerobic bottle and an ESP 80A aerobic bottle. The FAN aerobic bottle contains an antimicrobial-absorbing material; the 80A aerobic bottle does not. Bottles were processed on their respective continuous-monitoring blood culture instruments for up to five days of incubation. Four hundred thirty-three cultures (6.9%) representing 301 septic episodes in 235 different patients yielded 490 bacteria or yeasts thought to be clinically significant. Two hundred seventy-five of the 433 presumed clinically significant positive cultures (63.5%) representing 195 septic episodes and yielding 301 isolates were positive in both FAN and 80A bottles. One hundred nine significant positive cultures (25.2%) (i.e., cultures positive with an organism judged to be of probable clinical significance) from 70 septic episodes yielded 126 isolates only in FAN bottles. Conversely, the 80A bottle was exclusively positive in 49 instances (11.3%), representing 36 septic episodes and yielding 63 isolates. The higher rates of significant positive blood cultures, numbers of septic episodes documented, and numbers of isolates recovered in FAN bottles versus 80A bottles were all statistically significant (P < 0.05). Enhanced rates of detection of presumed clinically significant isolates in FAN bottles were largely accounted for by Staphylococcus aureus, members of the Enterobacteriaceae, and non-Pseudomonas aeruginosa miscellaneous gram-negative bacilli from patients receiving antimicrobial therapy at the time blood cultures were obtained. Enhanced recovery of one organism group, the beta-hemolytic streptococci, occurred in 80A. With one exception, detection times were essentially equivalent in the two systems. The single exception pertained to streptococci and enterococci, which were recovered significantly faster in 80A bottles. Three hundred thirty-eight of the 6,305 blood cultures evaluated in this study (5.4%) were judged likely to be contaminated. The percentages of probable contaminated cultures were as follows: 26.6% FAN and 80A; 42.3% FAN only; 31.1% 80A only (P < 0.05). Finally, the instrument false-positive rates for the two systems were 0.7% with FAN and 3.0% with 80A (P < 0.05). We conclude that while contamination rates were slightly higher with FAN than with 80A, use of FAN aerobic bottles in conjunction with the BacT/Alert system will yield significantly higher numbers of clinically significant blood culture isolates than 80A bottles and the ESP system. Furthermore, this enhanced detection is most conspicuous in patients receiving antimicrobial therapy at the time blood cultures are performed, probably due to the presence of an antimicrobial-absorbing material in FAN aerobic bottles.

Bacteremia↗
PubMed1997

Assessment of the oxacillin disk screening test for determining penicillin resistance in Streptococcus pneumoniae.

The 1 microgram oxacillin disk diffusion screening test was performed on 1516 recent clinical isolates of Streptococcus pneumoniae obtained in a 1994-1995 U.S. surveillance study and the results compared to penicillin MICs determined using a standardized broth microdilution method. The oxacillin disk screening method failed to distinguish penicillin-resistant strains from those that were intermediately susceptible. Furthermore, a high percentage (11.1%) of penicillin-susceptible strains, for which MICs of penicillin were usually 0.06 or 0.03 microgram/ml, yielded zone diameters of < or = 19 mm with the oxacillin screen test and thus would have been falsely categorized as being resistant to penicillin.

Microbial Sensitivity Tests↗
PubMed1997

Multicenter evaluation of antimicrobial resistance to six broad-spectrum beta-lactams in Colombia using the Etest method. The Colombian Antimicrobial Resistance Study Group.

The need for comprehensive and quantitative accurate antimicrobial resistance surveillance systems has become acute as a guide to problem recognition and to focus local interventions. A multilaboratory (10 medical centers) Colombia surveillance project was initiated in early 1997 to monitor the potency and spectrum of six (cefepime, cefotaxime, ceftazidime, cefoperazone/sulbactam, aztreonam, and imipenem) broad-spectrum antimicrobial agents tested against 100 organisms per participant center (802 strains). Ten groups of organisms were tested by a reference-quality method (Etest; AB BIODISK, Solna, Sweden) with results validated by concurrent quality control and additional challenge strain analysis. Results from nine qualifying medical centers were tabulated, and 95.7 to 96.8% of quality assurance tests were within expected ranges. Only cefepime (90.1-100.0% susceptible) and imipenem (96.3-100.0%) were active against all Enterobacteriaceae at > 90% of susceptible isolates using the breakpoint concentrations recommended by the National Committee for Clinical Laboratory Standards. Among ceftazidime- (or cefotaxime- or aztreonam-) resistant Enterobacter spp. and Citrobacter freundii, cefepime remained active, but not cefoperazone with sulbactam. Escherichia coli and Klebsiella spp. strains having resistance phenotypes consistent with extended spectrum beta-lactamase production were discovered in approximately 5 to 10% of isolates. All tested drugs except ceftazidime (31.8-57.7% susceptible) were active against > 94% of oxacillin-susceptible staphylococci. Similar rates of resistance (9.1-14.8%) were observed in Pseudomonas aeruginosa for five of six drugs (not cefotaxime; 15.9% of strains were susceptible). Acinetobacter spp. isolates were most susceptible to imipenem (95.8%), cefepime (86.1%), and cefoperazone/sulbactam (83.3%). Overall for the 1997 order of antimicrobial spectrums for these tested compounds was: imipenem (96.6%) > cefepime (93.6%) > cefoperazone/sulbactam (90.5%) > cefotaxime (74.9%) > aztreonam (74.3% for Gram-negative bacilli only) > ceftazidime (73.2%). These data should be used to guide empiric regimens in Colombia, and additionally will provide a resistance statistical baseline to which future studies in this nation can be compared.

Anti-Bacterial Agents↗
PubMed1997

Comparison of the Vidas and Bio-Whittaker enzyme immunoassays for detecting IgG reactive with varicella-zoster virus and mumps virus.

A total of 215 sera, 164 positive and 51 negative for antibody reactive with varicella-zoster virus (VZV), were analyzed using two commercially available enzyme immunoassays (EIAs) for detecting VZV-IgG, the Vidas Varicella-Zoster IgG assay (bioMeriéux Vitek, Inc., Hazelwood, MO, USA) and the Bio-Whittaker Varicella II assay (Bio-Whittaker, Inc., Walkersville, MD). The sensitivity and specificity of the Vidas and EIA for VZV-IgG was 98.9 and 100%, respectively. The sensitivity of the Bio-Whittaker VZV-IgG EIA assay was 98.8%, specificity 96.1%. Equivocal results were obtained with 4 and 2 sera, respectively. A total of 185 sera, 169 positive and 16 negative for mumps virus antibody, were analyzed with Vidas and Bio-Whittaker mumps IgG EIAs. The sensitivity of the two assays for detecting mumps IgG was 99.4% and 95.7%, respectively. Both assays demonstrated 100% specificity. Two of the 185 sera tested for mumps antibody yielded equivocal results with the Vidas EIA; four equivocal results were obtained with the Bio-Whittaker EIA.

Antibodies, Viral↗
PubMed1997

Antibiotic resistance among clinical isolates of Haemophilus influenzae in the United States in 1994 and 1995 and detection of beta-lactamase-positive strains resistant to amoxicillin-clavulanate: results of a national multicenter surveillance study.

A total of 1,537 clinical isolates of Haemophilus influenzae were recovered in 30 U.S. medical center laboratories between 1 November 1994 and 30 April 1995 and were characterized in a central laboratory with respect to serotype and beta-lactamase production and the in vitro activities of 15 oral antimicrobial agents. Overall, 36.4% of the isolates were found to produce beta-lactamase. The rank order of activity of six cephalosporins on the basis of MICs was cefixime > cefpodoxime > cefuroxime > loracarbef > or = cefaclor > cefprozil. On the basis of current National Committee for Clinical Laboratory Standards (NCCLS) breakpoints ages of isolates found to be resistant or intermediate to these agents were as follows: 0.1, 0.3, 6.4, 16.3, 18.3, and 29.8, respectively (National Committee for Clinical Laboratory Standards. Methods for dilution antimicrobial susceptibility tests for bacteria that grow aerobically, 4th ed. M7-A4, 1995). Azithromycin was, on a weight basis, the most potent of the macrolides tested in this study, followed by erythromycin and then clarithromycin. Azithromycin was typically fourfold more active than erythromycin, which was, in turn, slightly more active than clarithromycin. However, when compared on the basis of the frequency of resistance determined by using current NCCLS breakpoints, there was essentially no difference between azithromycin and clarithromycin, i.e., 0.5 and 1.9%, respectively (P = 0.086). Interpretive breakpoints for erythromycin MIC tests versus H. influenzae have not been developed. Resistance to other non- beta-lactam agents was variable, as follows: trimethoprim-sulfamethoxazole, 9.0%; chloramphenicol, 0.2%; tetracycline, 1.3%; and rifampin, 0.3%. Two conspicuous findings in this study were the identification of 39 strains H. influenzae that were beta-lactamase negative but ampicillin intermediate or resistant (BLNAR) and, even more surprisingly, 17 beta-lactamase-positive isolates that were resistant to amoxicillin-clavulanate (BLPACR). Strains of H. influenzae in the first group have heretofore been very uncommon; organisms in the second group have not previously been described in the literature. The percentages of all study isolates comprised of BLNAR and BLPACR organisms were 2.5 and 1.1, respectively. Overall resistance to ampicillin was thus 38.9%, and that to amoxicillin-clavulanate was 4.5%.

Adolescent↗