Kari C. Kugler

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%.

Survey of Bloodstream Infections Due to Gram-Negative Bacilli: Frequency of Occurrence and Antimicrobial Susceptibility of Isolates Collected in the United States,Canada, and Latin America for the SENTRY Antimicrobial Surveillance Program, 1997

During 1997, a total of 4,267 nosocomial and community-acquired bloodstream infections due to gram-negative organisms were reported from SENTRY hospitals in Canada (8 sites), the United States (30 sites), and Latin America (10 sites). Escherichia coli was the most common isolate (41% of all gram-negative isolates), followed by Klebsiella species (17.9%), Pseudomonas aeruginosa (10.6%), and Enterobacter species (9.4%). For all gram-negative isolates combined, the most active antimicrobials tested were meropenem, imipenem, and cefepime. The quinolones levofloxacin (MIC90, 2 microg/mL), ciprofloxacin (MIC90, 1 microg/mL), gatifloxacin (MIC90, 2 microg/mL), sparfloxacin (MIC90, 2 microg/mL), and trovafloxacin (MIC90, 2 microg/mL) were also active against most isolates. Bloodstream infection isolates from Latin America were uniformly more resistant to all classes of antimicrobial agents tested than were isolates from Canada or the United States. Resistance phenotypes consistent with extended-spectrum beta-lactamase production were also most common among E. coli and Klebsiella species from Latin America. Further investigation of the reasons for regional differences in resistance patterns is needed, as is ongoing surveillance to detect resistance trends and to guide antimicrobial use.

Survey of blood stream infections attributable to gram-positive cocci: frequency of occurrence and antimicrobial susceptibility of isolates collected in 1997 in the United States, Canada, and Latin America from the SENTRY antimicrobial surveillance program

The SENTRY Antimicrobial Surveillance Program was established in January, 1997 to monitor the predominant pathogens and antimicrobial resistance patterns of nosocomial and community-acquired infections via a network of sentinel hospitals in the United States (30 sites), Canada (eight sites), Latin America (10 sites), and Europe (24 sites). During the first 12-month study period (January to December, 1997), a total of 9519 blood stream infections (BSI) were reported by SENTRY participants in the U.S. (6150), Canada (1727), and Latin America (1642). The Gram-positive cocci, Staphylococcus aureus, coagulase-negative staphylococci (CoNS), enterococci, and streptococci accounted for 53.9% (5131 infections) of all BSI (56.5% U.S., 55.7% Canada, and 42.9% Latin America). The staphylococci, Enterococcus spp., S. pneumoniae, beta-hemolytic streptococci, and viridans group streptococci accounted for 6 of the top 11 BSI pathogens in the U.S. and Canada, whereas only S. aureus (1st), CoNS (3rd), and Enterococcus spp. (9th) were among the top 11 pathogens in Latin American hospitals. The results of this survey affirm the importance of Gram-positive cocci as causes of BSI in both North America and Latin America and demonstrate that important antimicrobial resistance exists among isolates of staphylococci, streptococci, and enterococci from all three geographic regions. This includes oxacillin-resistance among S. aureus (26.9% U.S., 29.2% Latin America, and 4.0% Canada) and CoNS (71.5% U.S., 68.4% Latin America, and 65.6% Canada), penicillin resistance among viridans group streptococci (48.5% U.S., 45.1% Canada, and 33.3% Latin America) and pneumococci (36.1% U.S., 27.5% Canada, and 65.6% Latin America), high-level resistance (HLR) to aminoglycosides among enterococci (27.2 to 70.1% U.S., 33.3 to 75.7% Canada and 16.7 to 51.5% Latin America), and macrolide resistance among beta-hemolytic streptococci (12.4 to 14.2% U.S., 10.5 to 12.3% Canada, and 0.0 to 4.0% Latin America), viridans group streptococci (32.4 to 39.7% U.S., 22.5-35.2% Canada, and 20.0% Latin America), and pneumococci (10.0 to 10.6% U.S., 9.8-10.8% Canada, and 9.4-18.7% Latin America). BSI isolates of Gram-positive cocci from the U.S. and Latin America were considerably more resistant than those from Canada. New agents with Gram-positive activity will be essential for optimal treatment of BSI attributable to Gram-positive cocci in both North and Latin America.

Haemophilus influenzae and Moraxella catarrhalis from Patients with Community-Acquired Respiratory Tract Infections: Antimicrobial Susceptibility Patterns from the SENTRY Antimicrobial Surveillance Program (United States and Canada, 1997)

ABSTRACT Between February and June of 1997, a large number of community-acquired respiratory tract isolates of Haemophilus influenzae (n = 1,077) and Moraxella catarrhalis (n = 503) from 27 U.S. and 7 Canadian medical centers were characterized as part of the SENTRY Antimicrobial Surveillance Program. Overall prevalences of β-lactamase production were 33.5% in H. influenzae and 92.2% in M. catarrhalis with no differences noted between isolates recovered in the United States and those from Canada. Among a total of 21 different antimicrobial agents tested, including six cephalosporins, a β-lactamase inhibitor combination, three macrolides, tetracycline, trimethoprim-sulfamethoxazole (TMP-SMX), rifampin, chloramphenicol, five fluoroquinolones, and quinupristin-dalfopristin, resistance rates of >5% with H. influenzae were observed only with cefaclor (12.8%) and TMP-SMX (16.2%).

Characteristics of pathogens causing urinary tract infections in hospitals in North America: results from the SENTRY Antimicrobial Surveillance Program, 1997

Urinary tract infection (UTI) is common and involves pathogens with changing susceptibility patterns. The SENTRY Antimicrobial Surveillance Program evaluates international pathogen incidence patterns to detect and manage the emergence of resistant strains. We describe the antimicrobial resistance patterns among 1617 pathogens recovered from UTIs during the third-quarter of 1997 in North America (United States and Canada), as part of this worldwide program. The isolates were tested against more than 50 antimicrobial agents (20 reported) by reference broth microdilution methods, and selected isolates were characterized by pulsed-field gel electrophoresis (PFGE) and automated ribotyping. The five most frequently isolated species were Escherichia coli (48.6%), Enterococcus spp. (13.7%), Klebsiella spp. (12.0%), Pseudomonas aeruginosa (6.2%), and Enterobacter spp. or Proteus mirabilis (3.8% each). For each nation, imipenem and cefepime produced the widest spectrum of coverage among the beta-lactams and amikacin was best among the aminoglycosides. For Gram-negative species, high resistance among beta-lactam antimicrobial agents was noted especially for various penicillins against E. coli (37.9% to 42.8%) and for the cephalosporins tested against enterococci (99.4% and 100%). Approximately 7.0% of enterococci in the USA were vancomycin-resistant (88% with Van A). P. aeruginosa provided the most consistent levels of resistance, but the following agents were most active against these organisms: amikacin (96.6 to 97.4% susceptible), tobramycin (89.5 to 100.0%), piperacillin/tazobactam (89.5 to 100.0%), piperacillin (89.5 to 96.6%), imipenem (89.7 to 92.1%), cefepime (77.6 to 89.7%), and ceftazidime (82.9 to 86.2%). E. coli (2.2 to 2.7%), K. pneumoniae (6.2 to 6.4%), and a single Enterobacter cloacae strain produced extended-spectrum beta-lactamases; and five other Enterobacter spp. were likely to have expressed chromosomally mediated (Amp C) Stably derepressed cephalosporinases with associated resistance to ceftazidime (16.7 to 21.2% resistance). These data demonstrated that several UTI isolates in SENTRY hospitals have high levels of resistance to various classes of antimicrobial agents with little evidence of clonal dissemination.

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)

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.

Trends in antimicrobial susceptibility of bacterial pathogens isolated from patients with bloodstream infections in the USA, Canada and Latin America

From January through June of 1998, 4579 bloodstream infections (BSI) due to bacterial pathogens were reported from SENTRY hospitals in Canada, the USA and Latin America. Staphylococcus aureus, Escherichia coli, and coagulase-negative staphylococcus (CoNS) were the most common pathogens, together accounting for 55.2% of all BSI during this time period. Compared with the 5794 BSI reported from SENTRY from January through June of 1997, no major change was seen in the frequencies of occurrence of the most common bacterial causes of BSI. Between 1997 and 1998, the major change in antimicrobial resistance was an increase in oxacillin-resistance in both S. aureus and CoNS in all regions. These data demonstrate widespread antimicrobial resistance in Canada, Latin America and the USA, with a notable increase in oxacillin-resistance among staphylococci. Ongoing surveillance remains essential, and will enhance efforts to limit the scope of this worldwide problem.

Bacterial pathogens isolated from patients with skin and soft tissue infections: frequency of occurrence and antimicrobial susceptibility patterns from the SENTRY Antimicrobial Surveillance Program (United States and Canada, 1997)

As part of the SENTRY Antimicrobial Surveillance Program, 1562 bacterial isolates were recovered from hospitalized patients with skin and soft tissue infections (SSTIs) in 30 United States (U.S.) and 8 Canadian medical centers between October and December, 1997. The overall rank order of recovery of the six most common pathogens was Staphylococcus aureus (42.6%) > Pseudomonas aeruginosa (11.3%) > Enterococcus spp. (8.1%) > Escherichia coli (7.2%) > Enterobacter spp. (5.2%) > beta-hemolytic streptocci (5.1%). With one exception, essentially the same order was observed in both the U.S. and Canada. The single exception was the Enterococcus group, which were the third most common isolate in the U.S. (9.6%), but the seventh most common isolate in Canada (3.7). Of note, 24.0% of S. aureus isolates were oxacillin resistant; vancomycin was uniformly active. Vancomycin resistance among Enterococcus spp. (16.5%) was observed only in the U.S. Several antimicrobial agents remained broadly active for SSTI isolates of P. aeruginosa, including meropenem, amikacin, tobramycin, and piperacillin with or without tazobactam. Imipenem resistance (MICs, > or = 8 micrograms/mL) was observed in 11.9% of isolates of P. aeruginosa and ceftazidime, and cefepime had equivalent activity (85.2% and 85.8% susceptible, respectively). Numerous beta-lactams, aminoglycosides and fluoroquinolones were broadly active against E. coli SSTI isolates (i.e. < 5% resistance). Extended-spectrum beta-lactamase production was uncommon both with E. coli and Klebsiella spp. in both nations. Cefepime, imipenem, and meropenem; the aminoglycosides; and fluoroquinolones were conspicuously more active against Enterobacter spp. than other agents tested. High-level, stably derepressed Amp C beta-lactamase production was commonly observed in this group (26.8%), but cefepime generally retained activity against these ceftazidime-resistant organisms. The results of this study serve to define the most common bacterial causes of SSTIs in North America, elucidate patterns of antimicrobial resistance and can be used as a basis for making initial empiric antimicrobial management decisions in hospitalized patients with such infections.

Strength training for obesity prevention in midlife women.

OBJECTIVE: The primary goal of this study was to assess whether increases in fat-free mass (FFM) and decreases in total and percentage fat mass from 15 weeks of twice weekly supervised strength training would be maintained over 6 months of unsupervised exercise in a randomized controlled trial.DESIGN: In all, 60 women aged 30–50 y, body mass index between 20 and 35 kg/m2, were randomized to control or treatment groups. The treatment group performed twice-weekly supervised strength training followed by 6 months of unsupervised training. Measurements at baseline, 15, and 39 weeks included body weight and body composition by dual-energy X-ray absorptiometry. Repeated measures regression was used to assess between-group differences for changes over time.RESULTS: Almost 90% of prescribed exercise sessions were completed. The body composition treatment effects over 15 weeks were largely maintained over 6 months of unsupervised exercise. Over the total 39 weeks of strength training, the treatment group gained +0.89 kg more in FFM, lost −0.98 kg more in fat mass, and lost –1.63% more in percent body fat when compared to the control group. P-values for these between-group differences in 39-week changes were 0.009, 0.06, and 0.006, respectively. Strength training did not result in any significant weight loss or waist circumference attenuation. Adjustment for changes in energy intake and physical activity did not alter these results.CONCLUSIONS: Twice-weekly strength training is behaviorally feasible for busy midlife women and the favorable body composition changes resulting from supervised strength training can be maintained over time. These findings lay the groundwork for determining the long-term health benefits of this behaviorally feasible exercise prescription, potentially including prevention of age-associated fat gains.

Antibacterial activity of 41 antimicrobials tested against over 2773 bacterial isolates from hospitalized patients with pneumonia: I—results from the SENTRY Antimicrobial Surveillance Program (North America, 1998)

Pneumonia is the second most frequent cause of nosocomial infection, and hospitalization frequently is needed for community-acquired pneumonia. Knowledge of causative pathogens through periodic surveillance, and their prevailing antimicrobial susceptibility patterns becomes paramount in choosing appropriate empiric therapy. The SENTRY Antimicrobial Surveillance Program, tracks pathogen distribution worldwide since 1997 and documents emerging resistance to a wide range of antimicrobial agents. During the respiratory disease season in 1998, each of 30 medical centers (25 in the United States [US], and five in Canada [CAN]) contributed 100 consecutive isolates obtained from hospitalized patients with suspected pneumonia. The 2773 organisms, processed by the monitor consisted of a total of 35 species, with Staphylococcus aureus comprising 25.6% of all isolates and five other species (Pseudomonas aeruginosa 18.7%, Haemophilus influenzae 9.4%, Streptococcus pneumoniae 7.8%, Klebsiella spp. 7.0%, and Enterobacter spp. 6.7%) making up almost 50% of the total. In the US, pneumococci (8.5%) were more prevalent than in CAN (4.1%; p = 0.001). The US isolates of S. pneumoniae were variably susceptible to penicillin (76.8%), with non-susceptible strains demonstrating greater levels of cross resistance to macrolides (31.8%), cefepime (9.0%) and cefotaxime (6.8%), but remaining susceptible to gatifloxacin and quinupristin/dalfopristin. H. influenzae and Moraxella catarrhalis were generally ampicillin-resistant, 40.4-44.4% and 93.7-95.7%, respectively. P. aeruginosa remained very susceptible to amikacin (91.3-93.8%) > tobramycin > meropenem > piperacillin/tazobactam > gentamicin > piperacillin > cefepime (80.0-81.8%). Extended spectrum beta-lactamase phenotypes among the Klebsiella spp. were isolated from five medical centers in the US and were 4.8-6.0% overall; a rate similar to the previous year. Among the US isolates of Enterobacter spp., only 77.6% and 79.6% were susceptible to ceftazidime and cefotaxime, respectively, but >90% were inhibited by cefepime, imipenem, meropenem, aminoglycosides, and fluoroquinolones. Isolates from CAN were generally more susceptible, except for Pseudomonas isolates, where resistance to aminoglycosides, fluoroquinolones and imipenem was greater. The SENTRY Program results outline important national differences in the frequencies of pathogen occurrence, but more importantly, identify unstable patterns of resistance to available antimicrobial drugs, and serves as a reference for results of other local, national or international investigations.