Relationships between antimicrobial use and antimicrobial resistance in Gram-negative bacteria causing nosocomial infections from 1991-2003 at a university hospital in Taiwan

This study was conducted to evaluate the relationship between antimicrobial resistance and antimicrobial use in a university hospital in Taiwan. Disk susceptibility data of Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, Serratia marcescens, Proteus spp., Pseudomonas aeruginosa, Acinetobacter spp., Stenotrophomonas maltophilia and other non-fermentative Gram-negative bacilli causing nosocomial infections were evaluated. Data on annual patient-days and annual consumption (defined daily dose (DDD) per 1000 patient-days) of extended-spectrum cephalosporins (cefotaxime, ceftriaxone, ceftazidime, flumoxef, cefepime and cefpirome), β-lactam–β-lactamase inhibitor combinations (ticarcillin/clavulanic acid and piperacillin/tazobactam), carbapenems (imipenem and meropenem), aminoglycosides (amikacin, gentamicin and tobramycin), fluoroquinolones (ciprofloxacin (oral and injectable) and oral levofloxacin and moxifloxacin) from 1991 to 2003 were analysed. Increasing trends of incidences of several of these bacteria causing all nosocomial infections or nosocomial bloodstream infections were noted from 1991 to 2003. The annual patient-days of the hospital significantly increased, from 360 210 in 1991 to 672 676 in 2002 (linear regression analysis, P < 0.05), but slightly decreased in 2003 (629 168) owing to the severe acute respiratory syndrome epidemic in Taiwan. The rise in cefotaxime-resistant or ciprofloxacin-resistant E. coli and meropenem-resistant P. aeruginosa was significantly correlated with increased consumption of extended-spectrum cephalosporins, β-lactam–β-lactamase inhibitor combinations, carbapenems, fluoroquinolones and aminoglycosides (for ciprofloxacin-resistant E. coli and meropenem-resistant P. aeruginosa only) in the hospital (Pearson's correlation coefficient, r > 0.72 (or <−0.72) and P-value < 0.05). Increased ciprofloxacin-resistant K. pneumoniae and meropenem-resistant Acinetobacter spp. was significantly associated with the increased usage of extended-spectrum cephalosporins but not with the other four classes of antibiotics. This 13-year study in a hospital demonstrated significant changes in antimicrobial use, which may have affected antimicrobial resistance in certain Gram-negative bacteria at the hospital.     

Susceptibility of bacterial isolates to gatifloxacin and ciprofloxacin from clinical trials 1997-1998

MICs of gatifloxacin and ciprofloxacin against 3482 pre-treatment, clinical trial isolates collected during 1997–1998 are reported. These data suggested that gatifloxacin was four- to eight-fold more active than ciprofloxacin against Gram-positive bacteria, with gatifloxacin MIC₉₀s≤0.33 mg/l against Staphylococcus aureus and Streptococcus pneumoniae, and ≤1.0 mg/l versus viridans streptococci and Enterococcus faecalis. Both quinolones had similar MIC₉₀s versus Enterobacteriaceae (generally ≤0.38 mg/l, except 0.7–0.8 mg/l for Citrobacter freundii) and Pseudomonas aeruginosa (8 mg/l). A total of 78% P. aeruginosa had gatifloxacin MICs ≤2 mg/l. Gatifloxacin was more active than ciprofloxacin against Acinetobacter species and non-P. aeruginosa pseudomonads. Both had exceptional activity versus Haemophilus spp, Moraxella catarrhalis and Neisseria gonorrhoeae. In summary, compared to ciprofloxacin, gatifloxacin had improved activity against Gram-positive bacteria and comparable activity against Gram-negative bacteria.     

Comparative activities of six different fluoroquinolones against 9,682 clinical bacterial isolates from 20 European university hospitals participating in the European SENTRY surveillance programme

The in-vitro activities of gatifloxacin, trovafloxacin, levofloxacin, sparfloxacin, ofloxacin, and ciprofloxacin were tested against 9,682 clinical bacterial isolates from 20 European university hospitals participating in the European SENTRY surveillance programme. Gatifloxacin and trovafloxacin exhibited the highest activities against Gram-positive cocci, while levofloxacin, ofloxacin, ciprofloxacin, and gatifloxacin were the most active against Enterobacteriaceae. Ciprofloxacin and levofloxacin showed the highest antimicrobial activities against Pseudomonas spp., while gatifloxacin and trovafloxacin were the most active against Acinetobacter spp. and Stenotrophomonas maltophilia. All Haemophilus spp. and Moraxella catarrhalis isolates were fully susceptible to all quinolones tested. Overall, the new quinolones, showed improved activity against Gram-positive cocci and Gram-negative non-fermenters while retaining their broad-spectrum activity against Gram-negative bacilli.     

A comparison of the antimicrobial activity of meropenem and selected broad-spectrum antimicrobials tested against multi-drug resistant Gram-negative bacilli including bacteraemic Salmonella spp.: initial studies for the MYSTIC programme in India

The evolution in India of multi-drug resistant pathogens possessing extended-spectrum β-lactamases (ESBLs) threatens to compromise the clinical utility of third-generation cephalosporins and monobactams. Using selected resistant strains from a recent Indian 10 centre surveillance study that measured the prevailing incidence of resistance to β-lactam antibiotics, the potential clinical utility of meropenem was assessed against nine other antimicrobial agents. A total of 212 Gram-negative bacilli were tested, of which 125 were confirmed by reference methods to be ESBL-producers. Meropenem was the most active of the test antimicrobials against these strains and the rank order of susceptibility was meropenem (99.1% susceptible)>piperacillin/tazobactam (76.9%)>ciprofloxacin (42.5%)>aminoglycosides (34.4–39.6%)=other β-lactams (30.0–39.6%). Of the tested strains only two (Acinetobacter spp. and Pseudomonas putida) showed an intermediate susceptibility (8 mg/l) to meropenem. Of the 57 tested strains of Salmonella spp., three had an ESBL phenotype, confirmed two of the strains. This study confirms the high levels of resistance to β-lactams agents in India reported elsewhere and also demonstrates, for Escherichia coli and Klebsiella spp., high levels of co-resistance between the tested β-lactam agents and ciprofloxacin and the aminoglycosides, gentamicin and tobramycin. However, carbapenems such as meropenem, remain a therapeutic option.     

Colistin susceptibility testing by Etest and disk diffusion methods

The accuracy of disk susceptibility methods for colistin against 778 bacterial pathogens was evaluated in comparison with Etest using interpretive criteria available from the Clinical and Laboratory Standards Institute (CLSI). Colistin exhibited excellent activity against Acinetobacter baumannii and Escherichia coli isolates (minimum inhibitory concentration for 90% of the organisms (MIC₉₀) = 0.5 mg/L), whilst it was less active both against Enterobacter spp. and Klebsiella pneumoniae (MIC for 50% of the organisms (MIC₅₀) = 0.5 mg/L, MIC₉₀ = 16 mg/L). Colistin also showed good activity against Pseudomonas aeruginosa (MIC₉₀ = 2 mg/L, MIC₅₀ = 1 mg/L) but poor activity against Stenotrophomonas maltophilia (MIC₅₀ = 8 mg/L, MIC₉₀ = 128 mg/L). Only 0.8% of minor errors were observed between the studied methods for P. aeruginosa isolates when the CLSI criteria were applied. All A. baumannii isolates with a zone diameter ≤12 mm were resistant and those with a zone diameter ≥14 mm were susceptible according to MIC breakpoints established by the CLSI. Among nine isolates exhibiting a zone diameter of 13 mm, one was resistant to colistin (MIC = 8 mg/L) and eight isolates were susceptible (MIC = 0.5 mg/L). Applying a MIC breakpoint of ≤2 mg/L for susceptibility in Enterobacteriaceae, all isolates with a zone diameter ≥14 mm were susceptible, whilst all isolates with a zone diameter ≤11 mm were resistant. Among isolates with zone diameters of 12–13 mm, 59% were characterised as susceptible. Major errors were observed only in K. pneumoniae isolates at a rate of 0.8%. The poor agar diffusion characteristics of colistin limit the predictive accuracy of the disk diffusion test and consequently values of 12–13 mm should be confirmed with MIC determination by Etest or broth dilution method.     

The indirect pathogenicity of Stenotrophomonas maltophilia

Stenotrophomonas maltophilia has at least two inducible β-lactamases, L1 and L2, which can hydrolyze almost all classes of β-lactam antimicrobial agents. This study was done to verify the indirect pathogenicity of S. maltophilia that could promote the growth of other β-lactam agent-susceptible bacteria in a mixed culture. We counted CFU of β-lactam agent-susceptible bacteria under the presence of imipenem or ceftazidime in a pure culture and mixed culture with S. maltophilia. Our results showed that β-lactamase leaking from S. maltophilia can encourage the growth of Serratia marcescens and Pseudomonas aeruginosa even if imipenem or ceftazidime was supplemented. This study discovered a blind spot in chemotherapy against an indirect pathogen such as S. maltophilia.     

Assessment of pathogen occurrences and resistance profiles among infected patients in the intensive care unit: report from the SENTRY Antimicrobial Surveillance Program (North America, 2001)

Originating from 25 selected intensive care units (ICUs) in North America, a total of 1,321 bacterial strains from blood, respiratory tract, urine and wound sites were processed at a central laboratory as part of the SENTRY Antimicrobial Surveillance Program (2001) to assess their occurrence rates and antimicrobial susceptibility profiles. The rank order of pathogens recovered was Staphylococcus aureus (24.1%), Pseudomonas aeruginosa (12.2%), Escherichia coli (10.1%), Klebsiella spp. (8.9%), Enterococcus spp. (7.2%), coagulase-negative staphylococci (7.0%) and Enterobacter spp. (7.0%). Although oxacillin resistance among S. aureus was 51.4%, no resistance was detected to vancomycin, linezolid and quinupristin/dalfopristin. The most active agents tested against P. aeruginosa were amikacin, cefepime, tobramycin, meropenem and piperacillin/tazobactam (3.1-13.0% resistance). Among agents tested against the Enterobacteriaceae, amikacin, cefepime, imipenem and meropenem showed greatest in vitro activity (0.0-3.4% resistance). Extended-spectrum beta-lactamase-producing phenotype rates were 11.2 and 16.2% in E. coli and Klebsiella spp., respectively. Linezolid was most active against enterococci (1.1% resistance; G2576U ribosomal mutation) whereas 28.4% of isolates were resistant to vancomycin. Cefepime and the carbapenems (imipenem or meropenem) for Gram-negative isolates and linezolid for Gram-positive isolates, provided the broadest spectrum of in vitro activity against contemporary ICU pathogens in North America.     

Sustained activity and spectrum of selected extended-spectrum beta-lactams (carbapenems and cefepime) against Enterobacter spp. and ESBL-producing Klebsiella spp.: report from the SENTRY antimicrobial surveillance program (USA, 1997-2000)

Enterobacter spp. and Klebsiella spp. are important clinical pathogens that frequently exhibit resistance to third-generation cephalosporins. In Enterobacter spp. strains, resistance is usually due to derepression of the Amp C locus, whereas plasmid-encoded extended-spectrum beta-lactamases (ESBLs) are primarily responsible for resistance in Klebsiella spp. Here we report the results from the SENTRY Antimicrobial Surveillance Program concerning the rates and trends of resistance to extended-spectrum beta-lactams and other antimicrobial agents in Enterobacter spp. and Klebsiella spp. isolated between 1997 and 2000 in participating hospitals in the United States. Among Enterobacter spp., resistance (MIC>or=32 mg/l) to aztreonam, ceftazidime and ceftriaxone ranged from 12.3 to 21.2% over the 4 years, whereas resistance in Klebsiella (MIC>or=2 mg/l) ranged from 5.9 to 6.8%. There was no trend toward increased resistance to these beta-lactam agents over the monitored period. Carbapenems (imipenem, meropenem) and cefepime had excellent activity against both ceftazidime-susceptible and -resistant Enterobacter spp. and Klebsiella spp. (>99% susceptible), although the minimum inhibitory concentration values of cefepime were higher in ceftazidime-resistant isolates compared with ceftazidime-susceptible isolates. Co-resistance to other antimicrobial agents was common in both tested genus groups.     

Mohnarin 2006-2007年度报告：非发酵革兰阴性杆菌耐药性监测

目的了解2006~2007年度全国84家医院中非发酵革兰阴性杆菌的分布情况及对各类抗菌药物的耐药性。方法药物敏感性试验采用纸片扩散法,耐药性数据分析采用WHONET5.4软件进行统计分析。结果共收集非发酵革兰阴性杆菌分离株22983株,菌株数列前6位的菌种为假单胞菌属(48.2%)、不动杆菌属(31.4%)、嗜麦芽寡养单胞菌(11.5%)、伯克霍尔德菌属(2.9%)、金黄杆菌属(2.1%)和产碱杆菌属(1.4%)。铜绿假单胞菌对左氧氟沙星、哌拉西林、头孢哌酮/舒巴坦、环丙沙星、头孢吡肟、头孢他啶、哌拉西林/三唑巴坦、美罗培南和阿米卡星敏感性范围从56.3%至73.8%;不动杆菌对亚胺培南和美罗培南的敏感率分别为77.3%和75.6%;头孢哌酮/舒巴坦69.9%,米诺环素69.4%。不动杆菌对本次研究中的其它抗菌药物耐药率高于38.8%。嗜麦芽寡养单胞菌对米诺环素、复方磺胺甲口恶唑和左氧氟沙星的敏感性分别为96.8%、82.8%和82.2%;洋葱伯克霍尔德菌对米诺环素、复方磺胺甲口恶唑、头孢他啶和美罗培南的敏感性分别为89.3%、72.9%、65.4%和62.9%。结论非发酵菌在临床分离比重大,细菌耐药明显,临床应采取积极措施,合理使用抗菌药物,减少耐药菌发生。     

How carbapenem-resistant Acinetobacter spp. established in a newly constructed hospital

Annually increasing rates of carbapenem-resistant Acinetobacter spp. were observed in a Taiwan hospital since its establishment in November 1998 to March 2005. Increasing consumption of carbapenems was also noticed. Carbapenem-resistant Acinetobacter spp. from 33 patients carried a class 1 integron. Twenty-eight isolates were Acinetobacter baumannii harbouring both ISAba1 and an OXA-51-like gene. Twenty-four of the 28 A. baumannii isolates had ISAba1 upstream of the OXA-51-like gene. Four A. baumannii isolates harboured the OXA-24-like gene and one isolate had the VIM-11 gene. Regarding the five non-baumannii Acinetobacter spp., three Acinetobacter genomic species 3 isolates and one Acinetobacter radioresistens isolate had both IMP-1 and OXA-58-like genes. One A. radioresistens isolate had an OXA-23-like gene. One major clone of A. baumannii (25/28; 89.3%) was identified by ribotyping. Three ribotypes were identified as being brought into the hospital by patient transfer from other hospitals. In conclusion, an insidious clonal dissemination with various resistance mechanisms contributed to the spread of carbapenem-resistant Acinetobacter spp. in a hospital setting, with increasing usage of carbapenems as the possible selection pressure. Notification of carbapenem-resistant Acinetobacter spp. infection when patients are transferred between hospitals is important to control the spread of carbapenem resistance.     

Use of in vitro susceptibility and pathogen prevalence data to model the expected clinical success rates of tigecycline and other commonly used antimicrobials for empirical treatment of complicated skin and skin-structure infections

The overall expected coverage for tigecycline and selected antimicrobial regimens based upon prevailing susceptibility rates was evaluated for the empirical therapy of complicated skin and skin-structure infections (cSSSIs). Consecutive, non-duplicate bacterial isolates collected from 2000–2005 from patients with documented cSSSI in 57 medical centres located in the USA (38 centres), France (6 centres), Germany (7 centres), Italy (3 centres) and Spain (3 centres) were used to evaluate the frequency of pathogen occurrence and susceptibility rates of select parenteral antimicrobials (SENTRY Program). By applying pathogen-specific susceptibility rates to the frequency of pathogen occurrence in each country, the overall expected coverage for each treatment regimen was measured. The most frequently isolated pathogens were Staphylococcus aureus (33.3–49.9%), Pseudomonas aeruginosa (8.3–17.2%), Escherichia coli (6.6–13.9%) and enterococci (4.1–8.8%). Tigecycline was highly active against the most common pathogens, except for P. aeruginosa and Proteus mirabilis. The highest overall expected empirical coverage was obtained with combination therapy regimens, including vancomycin plus either imipenem (94.4–99.3%) or piperacillin/tazobactam (92.5–98.2%). Among the monotherapy regimens evaluated, tigecycline provided the highest overall expected coverage in the USA (90.6%), France (89.9%) and Italy (83.3%), whilst piperacillin/tazobactam showed the highest expected coverage in Germany (93.1%) and imipenem in Spain (87.7%). Our results suggest that tigecycline represents a viable additional option for the empirical treatment of cSSSI in these countries.     

Susceptibility of Canadian isolates of Haemophilus influenzae, Moraxella catarrhalis and Streptococcus pneumoniae to oral antimicrobial agents

We measured the susceptibility of Canadian isolates of three respiratory tract pathogens (Haemophilus influenzae, Moraxella catarrhalis and Streptococcus pneumoniae) to several currently approved antimicrobial agents by two different methods. We also measured the susceptibility of isolates to seven fluoroquinolones. Beta-lactamase was produced by 123/566 (21.7%) of H. influenzae isolates compared with 178/200 (89%) of M. catarrhalis isolates. For S. pneumoniae 83/374 (22.2%) isolates were penicillin resistant and of these 2.1% (8/374) showed high level resistance (MIC≥2 mg/l). Regardless of methodology, all fluoroquinolones were highly active against H. influenzae (MIC₉₀ ≤0.031 mg/l) and M. catarrhalis (MIC₉₀ ≤0.064 mg/l) isolates. Susceptibility of H. influenzae to cefuroxime and amoxycillin/clavulanic acid was 99–100% whereas 84–85.5% were susceptible to cefaclor and cefprozil. Azithromycin susceptibility ranged from 82.6 to 99.2% depending on the method. M. catarrhalis isolates were uniformly susceptible to all agents tested except amoxycillin. Cross-resistance in S. pneumoniae to all non-quinolone agents was concurrent with increasing penicillin resistance as shown by increasing MIC₉₀ values. For the fluoroquinolones tested, the rank order of potency based on MIC₉₀ values was as follows: gemifloxacin (0.031–0.063 mg/l), trovafloxacin (0.125 mg/l), moxifloxacin (0.125–0.25 mg/l), grepafloxacin (0.125–0.25 mg/l), gatifloxacin (0.5 mg/l), levofloxacin (1 mg/l) and ciprofloxacin (2 mg/l). Our study confirms either a high or increasing prevalence of antimicrobial resistant respiratory pathogens in Canada and also compares the new and old fluoroquinolones and their potential role as therapy for community-acquired infections. The prevalence of β-lactamase positive H. influenzae may have decreased from levels reported in previous studies.     

嗜麦芽窄食单胞菌的耐药性变迁调查及与抗菌药物使用强度相关性分析

目的:对医院嗜麦芽窄食单胞菌的耐药性变迁情况及与抗菌药物使用强度相关性进行分析,为临床合理用药提供参考。方法:对2012-2017年医院各科室送检的标本进行检查,采用法国生物梅里埃公司的VITEK-ⅡCompact全自动微生物鉴定仪进行鉴定及纸片扩散法进行药敏分析,运用WHONET 5.5软件和SPSS 16.0软件进行数据统计分析。结果:嗜麦芽窄食单胞菌的标本主要来源为痰(54.0%)和支气管灌洗液(15.8%),主要分布于ICU(21.5%)和呼吸内科(18.0%)。嗜麦芽窄食单胞菌对头孢他啶、左氧氟沙星和复方磺胺甲恶唑的耐药率分别为21.8%、7.7%和13.4%。嗜麦芽窄食单胞菌对左氧氟沙星的耐药率与美罗培南和左氧氟沙星的使用强度存在高度正相关性(P<0.05),对复方磺胺甲吹恶唑的耐药率与阿米卡星的使用强度存在高度负相关性(P<0.01)。结论:嗜麦芽窄食单胞菌对某一药物产生耐药与该药或其他药物的使用强度相关,因此在临床上监测耐药率及抗菌药物的使用强度相关性有助于控制和降低抗菌药物的耐药率。     

Evaluation of antimicrobial activity of beta-lactam antibiotics using Etest against clinical isolates from 60 medical centres in Japan

An antimicrobial resistance surveillance study was carried out in 60 medical centres across Japan. Resistance to piperacillin was 10.8% in clinical isolates of Escherichia coli, while 1.3% or fewer isolates were resistant to other beta-lactams. Klebsiella spp. were more susceptible to imipenem, cefepime and cefpirome. Isolates of Enterobacter spp., Citrobacter spp., indole-positive Proteus and Serratia spp. were susceptible to imipenem, cefepime and cefpirome, while Acinetobacter spp. were most susceptible to cefoperazone/sulbactam, imipenem, ceftazidime (5.8% resistance) and cefepime (7.6%). Isolates of Pseudomonas aeruginosa were more susceptible to ceftazidime (12.3% resistance), cefoperazone/sulbactam (12.5%) and cefepime (12.6%) than to piperacillin (15.0%), cefpirome (22.6%) and imipenem (30.8%). The percentage of Japanese imipenem resistant P. aeruginosa clinical isolates was around 30%.     

Age-related trends in pathogen frequency and antimicrobial susceptibility of bloodstream isolates in North America: SENTRY Antimicrobial Surveillance Program, 1997-2000

We report age-related trends in pathogen frequency and antimicrobial susceptibility from 25,745 bloodstream infections (BSI) due to bacterial pathogens reported from medical centres participating in the North American SENTRY Antimicrobial Surveillance Program between January 1997 and September 2000. Staphylococcus aureus, Escherichia coli and coagulase-negative staphylococci (CoNS) were the most common pathogens, together accounting for 55% of all BSI pathogens during this time period. Among nosocomial BSI, CoNS were the most frequently isolated pathogens in infants less than 1 year of age, but S. aureus increased in frequency with increasing age. Among community-onset BSI pathogens, Streptococcus pneumoniae was the most frequently reported pathogen causing BSI in patients aged 1–5, S. aureus among those aged 6–64, and E. coli predominated at the extremes of age (less than 1 year and ≥65 years of age). Among key organism: antimicrobial agent combinations evaluated, oxacillin resistance in S. aureus increased with increasing age; conversely, oxacillin resistance among CoNS was highest among children 5 years of age or younger. Penicillin resistance among S. pneumoniae BSI was highest in children younger than 5 years, while vancomycin resistance among Enterococcus spp. predominated among nosocomial BSI in patients over 50 years of age. Important age-related differences exist in species distribution and antimicrobial susceptibility of pathogens causing BSI. This information should be helpful for clinicians as they consider empirical antimicrobial therapy for patients with suspected BSI across the age continuum.     

Pathogen occurrence and antimicrobial resistance trends among urinary tract infection isolates in the Asia-Western Pacific Region: report from the SENTRY Antimicrobial Surveillance Program, 1998-1999

Worldwide surveillance of antimicrobial resistance among urinary tract pathogens is useful to determine important trends and geographical variation for common Gram-positive and -negative species. The most common causative uropathogens often have intrinsic or acquired resistance mechanisms which include ESBL production among enteric bacilli, multi-drug resistant staphylococci and non-fermentative Gram-negative bacilli such as Pseudomonas aeruginosa and Acinetobacter spp. and vancomycin-resistant Enterococcus spp. This study evaluates pathogen frequency and the resistance rates among urinary tract infection (UTI) pathogens in 14 medical centres in the Asia-Pacific region between 1998 and 1999. The isolates were referred to a central monitor for reference NCCLS broth microdilution testing, identification confirmation and patient demographic analysis. Over 50% of the 958 pathogens were Escherichia coli and Klebsiella spp. followed by P. aeruginosa, Enterococcus spp. and Enterobacter spp. Susceptibility for the three enteric bacilli was high for carbapenems (100%), 'fourth-generation' cephalosporins (cefepime 94.9-98.6%) and amikacin (> or = 93.0%). Beta-lactamase inhibitor compounds were more active against E. coli (piperacillin/tazobactam; > 90% susceptible) than the other two enteric species and all other tested agents had a narrower spectra of activity. The rank order of anti-pseudomonal agents was amikacin (91.5% susceptible)> imipenem > piperacillin/tazobactam > tobramycin > ceftazidime and cefepime (77.4 and 76.4% susceptible, respectively). Susceptibility to quinolones for the P. aeruginosa isolates was only 63.2-67.0%. Only one vancomycin-intermediate Enterococcus spp. (van C phenotype) was detected among the 103 strains tested. Newer fluoroquinolones (gatifloxacin; MIC(50), mg/l) were more potent against enterococci than ciprofloxacin (MIC(50), 2 mg/l) and high-level resistance to aminoglycosides was common (41.7%). The data presented are compared to studies of similar design from other areas which are part of the SENTRY surveillance network.     

Bacteremia due to Enterobacter spp. in cancer patients--analysis of 51 episodes

Fifty one episodes of bacteremia due to Enterobacter spp. appearing within 7 years among 12 301 admissions in a single cancer institution were studied for risk factors, clinical presentation and outcome. Fifteen episodes were due to Enterobacter aerogenes, 23 due to E. cloacae and 13 due to E. agglomerans. The proportion of bacteremia due to Enterobacter spp. among Gram-negative bacteremias was 10.1% and infection associated mortality was 13.8%. The incidence in 1989–1995 varied from 3.7 to 8.7% and was relatively stable. Most common risk factors were: solid tumors as underlying disease, central venous catheter insertion, prior surgery and prior chemotherapy within 48 h. Neutropenia and urinary catheters were not at high risk in either one of the patients subgroups. Comparing two subgroups of 51 bacteremias, monomicrobial and polymicrobial (when Enterobacter spp. was isolated from blood culture with other microorganism), previous chemotherapy, vascular catheter insertion and prior endoscopy were more frequently associated with polymicrobial Enterobacter spp. bacteremia. There was also differences in infection associated mortality: bacteremias due to Enterobacter spp. only had significantly lower mortality in comparison to polymicrobial Enterobacter spp. bacteremias (3.3 vs. 29.3%; P<0.02). Susceptibility of Enterobacter spp. strains isolated from 51 episodes was stable and showed only two episodes due to quinolone-resistant strains, both in 1992 despite of the use of ofloxacin in prophylaxis of neutropenic patients since 1990 in our institute. Ninety-two to 94% of all strains were susceptible to aminoglycosides, 96–98% to ofloxacin and ciprofloxacin, respectively and 94.9% to meropenem but only 75.5% to ceftazidime.     

Nosocomial bloodstream infections in a Turkish university hospital: study of Gram-negative bacilli and their sensitivity patterns

Treatment of nosocomial bacteraemia is usually governed by the surveillance results of the particular unit. Such results are especially important when antimicrobial resistance rates are high. Multiresistant isolates including Gram-negatives producing extended-spectrum β-lactamases have been frequently reported in tertiary care units in Turkey. In this study, antimicrobial susceptibilities of Gram-negative blood isolates (n=348) were determined by microbroth dilution tests. The results showed carbapenems (meropenem and imipenem) to be uniformly more potent in vitro than any other drug against the Enterobacteriaceae. Quinolone antibiotics were more active in vitro than aminoglycosides against a range of bacteria. Gram-negative bloodstream isolates were highly resistant to many antimicrobial agents in the hospital. In order to prevent hospital infection and antimicrobial resistance, surveillance of aetiological agents must be performed regularly.     

The prevalence of antimicrobial resistance among uropathogens causing acute uncomplicated cystitis in young women

Four hundred and fifty-two urine isolates from women with acute uncomplicated cystitis and a positive urine culture presenting to a sexually transmitted disease clinic were collected during 1989–1991, and 213 specimens were collected over 1995–1997. The predominant species was Escherichia coli, representing 68% of the isolates; others included Staphylococcus saprophyticus (8%), Group B streptococci (7%), Proteus spp. (6%), Klebsiella spp. (4%) and Enterococcus spp. (3%). More than 10% of the E. coli isolates were resistant to ampicillin, cephalothin, tetracycline and trimethoprim–sulfamethoxazole (TMP–SMX ) during both study periods, with the greatest increase in resistance to ampicillin and TMP/SMX between the two periods. Six hundred and four urinary tract infection isolates, including 83% E. coli, 7% S. saprophyticus, 3% Klebsiella spp. 2% Proteus spp., 2% enterococci, 1% Enterobacter spp. and 2% other organisms, were collected from women with acute cystitis attending a university student health service during 1995. Among E. coli isolates, 25% were resistant to ampicillin, 24% to tetracycline and 11% to TMP–SMX. Resistance to fluoroquinolones was essentially absent among gram-negative pathogens. Continued evaluation of susceptibility patterns of pathogens causing acute uncomplicated cystitis to traditional as well as new antimicrobials in well defined populations is necessary to ascertain the optimal empiric therapy.     

Canadian Pseudomonas aeruginosa susceptibility study from 48 medical centers: focus on ciprofloxacin

We tested 1503 clinical isolates of Pseudomonas aeruginosa, from 48 Canadian medical centers, against ciprofloxacin and 11 other antimicrobial agents to determine in vitro activity. The frequency of susceptibility was highest for carbenicillin and ticarcillin (91% each) followed by imipenem and ceftazadime (90% each). Overall susceptibility (≤1.0 mg/l) to ciprofloxacin was 84% while resistance (≥4.0 mg/l) was 12%. Ciprofloxacin resistant isolates were more common from urinary tract specimens than from specimens collected from the respiratory and/or skin and soft tissue. Isolates from cystic fibrosis patients were more resistant to all agents tested than isolates from non-cystic fibrosis patients.