, 19 medical centers collected 4,180 isolates recovered from clinical specimens from patients in intensive care units (ICUs) in Canada. The 4,180 isolates were collected from 2,292 respiratory specimens (54.8%), 738 blood specimens (17.7%), 581 wound/tissue specimens (13.9%), and 569 urinary specimens (13.6%). The 10 most common organisms isolated from 79.5% of all clinical specimens were methicillin-susceptible Staphylococcus aureus (MSSA) (16.4%), Escherichia coli (12.8%), Pseudomonas aeruginosa (10.0%), Haemophilus influenzae (7.9%), coagulase-negative staphylococci/Staphylococcus epidermidis (6.5%), Enterococcus spp. (6.1%), Streptococcus pneumoniae (5.8%), Klebsiella pneumoniae (5.8%), methicillin-resistant Staphylococcus aureus (MRSA) (4.7%), and Enterobacter cloacae (3.9%). MRSA made up 22.3% (197/884) of all S. aureus isolates (90.9% of MRSA were health care-associated MRSA, and 9.1% were community-associated MRSA), while vancomycin-resistant enterococci (VRE) made up 6.7% (11/255) of all enterococcal isolates (88.2% of VRE had the vanA genotype). Extended-spectrum ␤-lactamase (ESBL)-producing E. coli and K. pneumoniae occurred in 3.5% (19/536) and 1.8% (4/224) of isolates, respectively. All 19 ESBL-producing E. coli isolates were PCR positive for CTX-M, with bla CTX-M-15 occurring in 74% (14/19) of isolates. For MRSA, no resistance against daptomycin, linezolid, tigecycline, and vancomycin was observed, while the resistance rates to other agents were as follows: clarithromycin, 89.9%; clindamycin, 76.1%; fluoroquinolones, 90.1 to 91.8%; and trimethoprim-sulfamethoxazole, 11.7%. For E. coli, no resistance to amikacin, meropenem, and tigecycline was observed, while resistance rates to other agents were as follows: cefazolin, 20.1%; cefepime, 0.7%; ceftriaxone, 3.7%; gentamicin, 3.0%; fluoroquinolones, 21.1%; piperacillin-tazobactam, 1.9%; and trimethoprim-sulfamethoxazole, 24.8%. Resistance rates for P. aeruginosa were as follows: amikacin, 2.6%; cefepime, 10.2%; gentamicin, 15.2%; fluoroquinolones, 23.8 to 25.5%; meropenem, 13.6%; and piperacillin-tazobactam, 9.3%. A multidrug-resistant (MDR) phenotype (resistance to three or more of the following drugs: cefepime, piperacillin-tazobactam, meropenem, amikacin or gentamicin, and ciprofloxacin) occurred frequently in P. aeruginosa (12.6%) but uncommonly in E. coli (0.2%), E. cloacae (0.6%), or K. pneumoniae (0%). In conclusion, S. aureus (MSSA and MRSA), E. coli, P. aeruginosa, H. influenzae, Enterococcus spp., S. pneumoniae, and K. pneumoniae are the most common isolates recovered from clinical specimens in Canadian ICUs. A MDR phenotype is common for P. aeruginosa isolates in Canadian ICUs.

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, an annual Canadian national surveillance study (CANWARD) tested 2,943 urinary culture pathogens for antimicrobial susceptibilities according to Clinical and Laboratory Standards Institute guidelines. The most frequently isolated urinary pathogens were as follows (number of isolates, percentage of all isolates): Escherichia coli (1,581, 54%), enterococci (410, 14%), Klebsiella pneumoniae (274, 9%), Proteus mirabilis (122, 4%), Pseudomonas aeruginosa (100, 3%), and Staphylococcus aureus (80, 3%). The rates of susceptibility to trimethoprim-sulfamethoxazole (SXT) were 78, 86, 84, and 93%, respectively, for E. coli, K. pneumoniae, P. mirabilis, and S. aureus. The rates of susceptibility to nitrofurantoin were 96, 97, 33, and 100%, respectively, for E. coli, enterococci, K. pneumoniae, and S. aureus. The rates of susceptibility to ciprofloxacin were 81, 40, 86, 81, 66, and 41%, respectively, for E. coli, enterococci, K. pneumoniae, P. mirabilis, P. aeruginosa, and S. aureus. Statistical analysis of resistance rates (resistant plus intermediate isolates) by year for E. coli over the 3-year study period demonstrated that increased resistance rates occurred only for amoxicillinclavulanate (from 1.8 to 6.6%; P < 0.001) and for SXT (from 18.6 to 24.3%; P ‫؍‬ 0.02). For isolates of E. coli, in a multivariate logistic regression model, hospital location was independently associated with resistance to ciprofloxacin (P ‫؍‬ 0.026) with higher rates of resistance observed in inpatient areas (medical, surgical, and intensive care unit wards). Increased age was also associated with resistance to ciprofloxacin (P < 0.001) and with resistance to two or more commonly prescribed oral agents (amoxicillin-clavulanate, ciprofloxacin, nitrofurantoin, and SXT) (P ‫؍‬ 0.005). We conclude that frequently prescribed empirical agents for urinary tract infections, such as SXT and ciprofloxacin, demonstrate lowered in vitro susceptibilities when tested against recent clinical isolates.There are an estimated 150 million urinary tract infections per year worldwide (31). In the United States, urinary tract infections result in approximately 8 million physician visits per year (33); they are the most common bacterial infections in women, and account for significant morbidity and associated health care costs (10, 31). Most visits to physicians for symptoms of acute cystitis do not result in urine culture or isolate antimicrobial susceptibility testing. Rather, urine culture is often reserved for patients failing empirical therapy and those with recurrent or complicated infections. Among both outpatients and inpatients, Escherichia coli is the primary urinary tract pathogen. It is estimated to account for 75 to 90% of uncomplicated urinary tract infection isolates and ca. 50 to 60% of isolates from patients with recurrent or complicated infections (10, 26).The currently recommended empirical antimicrobial regimen for treating acute uncomplicated bacterial cystitis in otherwise-healthy adult nonpregnant females is a 3-day course of double-strength t...

Ciprofloxacin-resistant Escherichia coli isolates (n ‫؍‬ 1,858) from outpatient midstream urine specimens at 40 North American clinical laboratories in 2004 to 2005 were frequently resistant to ampicillin (79.8% of isolates) and trimethoprim-sulfamethoxazole (66.5%); concurrent resistance to cefdinir (9.0%) or nitrofurantoin (4.0%) was less common. Only 10.8% of isolates were resistant to ciprofloxacin alone. Fluoroquinoloneresistant isolates of E. coli from urine were frequently multidrug resistant.The most recently published in vitro surveillance data from centers across the United States and Canada indicate that approximately 10 to 25% of urinary tract isolates of Escherichia coli from female outpatients are resistant to trimethoprimsulfamethoxazole (SXT) (3,7,10,11,12,21,22,25,26). Culture selection and sample selection biases inherent in published urinary isolate surveillance studies and hospital antibiograms have been summarized previously (8). Resistance to SXT may complicate the management of urinary tract infections (20), and physician concern regarding resistance to SXT (24) has resulted in fluoroquinolones and nitrofurantoin being more frequently prescribed as empirical therapy for cystitis (7, 9, 15).Currently, the majority of urinary isolates of E. coli and most other uropathogens causing uncomplicated cystitis and pyelonephritis in the United States and Canada remain susceptible to fluoroquinolones (5,10,11,12,21,22,25,26); however, the prevalence of fluoroquinolone-resistant isolates of E. coli has been reported to be increasing over time in some centers in the United States and Canada (3,7,11,12,13,18,23,25), and resistance rates have been shown to vary markedly by center, with some hospital laboratories reporting Ͼ25% of their E. coli isolates as fluoroquinolone resistant (3,23). Given that a transition in the therapy for outpatient urinary tract infections may be occurring, or appears imminent (7,8,9,15), and that fluoroquinolone-resistant isolates of E. coli are not uncommon in some centers, we determined the in vitro susceptibilities of prospectively collected fluoroquinolone-resistant midstream urine isolates of E. coli from outpatients to other agents used for the treatment of acute cystitis because these isolates may be encountered by clinicians and no prospective study specifically studying fluoroquinolone-resistant isolates has been published.From January 2004 to June 2005, fluoroquinolone-resistant E. coli isolates from midstream urine specimens from outpatients were collected from 30 medical centers in the United States (n ϭ 1,483) and from 10 Canadian medical centers (n ϭ 375) (25). Each isolate was deemed to be a significant urinary tract isolate by each participating laboratory's urine culture algorithm. Isolates and limited demographic information (patient gender and age) were submitted to the Health Sciences Centre in Winnipeg, Canada, where the isolates were confirmed to be E. coli by conventional methodology (17) and where Clinical and Laboratory Standards Institute-specified br...