Ciprofloxacin-resistant Escherichia coli emerging in a rehabilitation medical center

Cross-resistance and associated resistance in Escherichia coli isolates from nosocomial urinary tract infections between 2004–2006 in a Turkish Hospital

In this study, antimicrobial resistance profiles were determined for 748 isolates of Escherichia coli from patients with acute nosocomial urinary tract infections (UTIs) at a Turkish Training Hospital. Thirteen antibiotics were included. Resistance to ampicillin alone (45.1%) and ciprofloxacin alone (20.6%) were the most commonly identified ‘single resistances’. Multiple resistance was found in 49.7% of the strains. The most common multiple antibiotic resistance profiles included ampicillin-sulbactam/amoxycilline-clavulonate (4.0%) and ampicillin-sulbactam/trimethoprim-sulfamethoxazole/amoxycilline-clavulonate (2.8%). From 2004 to 2006, ampicillin, trimethoprim-sulfamethoxazole and ciprofloxacin resistant strains increased to 76% from 57%, 53% from 43% and 55% from 41%, respectively. The percentage of extended-spectrum β-lactamase (ESBL) producing strains was 7.8% and imipenem resistance was seen in 5.2% of ESBL positive strains. We conclude that clinically important E.coli strains have now emerged with broader multidrug resistance. Periodical evaluation of laboratory results and clinical surveillance are crucially important for optimal antibiotic management of UTIs and infection control policies.

Évaluation de la relation consommation de fluoroquinolones et émergence de résistance chez Escherichia coli : rôles respectif et comparatif des études observationnelles et quasi expérimentales

The emergence of Escherichia coli (E. coli) resistance to fluoroquinolones (FQs) increased and spread gradually worldwide since the early 1990s. The selective pressure of FQs is the main mechanism responsible for the emergence of FQ resistance as shown by in vitro studies. Clinical trials are required to prove the causality between exposure to FQs and emergence of resistance. But this would not be ethical in humans. Non experimental studies must answer several principles to establish causality: association, anteriority, and directional change. We described and compared the contribution of observational and quasi-experimental studies implemented to answer several of these principles. Quasi-experimental studies using interventional models (ARIMA models with transfer function), can answer several of these principles, unlike observational studies. Thus, in addition to assessment of the association, they were able to show that the exposure to FQs precedes the emergence of FQ resistance to E. coli. They were also able to estimate the time necessary for the emergence of resistance and the dose effect, and to show if this association was reversible.

Emerging antibiotic resistance in urinary tract pathogens

In vitro antimicrobial resistance is an evolving and growing problem in UTI. Much of the increase is occurring in acute uncomplicated cystitis, an infection that has traditionally been simple to treat. The current trend of rising TMP-SMX and beta-lactam resistance rates is worrisome. Of more concern, however, are the emerging issues of fluoroquinolone resistance and MDR among community-acquired urinary isolates. Judicious use of antibiotics and development of novel nonantimicrobial-based methods of prevention of UTI are important strategies to help slow the progression of resistance. In the meantime, ongoing surveillance of resistance trends and enhanced understanding of the determinants of resistance are crucial for optimal management of UTIs.

Emergence of reduced susceptibility and resistance to fluoroquinolones in Escherichia coli in Taiwan and contributions of distinct selective pressures

A survey of 1,203 Escherichia coli isolates from 44 hospitals in Taiwan revealed that 136 (11.3%) isolates were resistant to fluoroquinolones and that another 261 (21.7%) isolates had reduced susceptibility. Resistance was more common in isolates responsible for hospital-acquired (mostly in intensive care units) infections (17.5%) than in other adult inpatient (11.4%; P = 0.08) and outpatient isolates (11.9%; P > 0.1). Similarly, reduced susceptibility was more common in isolates responsible for hospital-acquired infections (30.9%) than in other adult inpatient (21.0%; P = 0.04) and outpatient (21.4%; P = 0.06) isolates. Isolates from pediatric patients were less likely to be resistant (1.3 versus 12.0%; P < 0.01) but were nearly as likely to have reduced susceptibility (17.7 versus 21.9%; P > 0.1) as nonpediatric isolates. There was an inverse relationship in the proportion of isolates that were resistant versus the proportion that had reduced susceptibility among isolates from individual hospitals (R = 0.031; P < 0.05). In an analysis of isolates from two hospitals, all 9 resistant strains possessed double point mutations in gyrA and all 19 strains with reduced susceptibility strains had single point mutations; no mutations were found among fully susceptible strains. Risk factors for resistance included underlying cancer (odds ratio [OR], 83; 95% confidence interval [CI(95)], 7.3 to 2,241; P < 0.001), exposure to a quinolone (OR, undefined; P = 0.02), and exposure to a nonquinolone antibiotic (OR, 20; CI(95), 2.2 to 482; P < 0.001); underlying cancer was the only independent risk factor (OR, 83; CI(95), 8.6 to 807; P < 0.001). There were no significant associations between any of these factors and reduced susceptibility. Whereas acute and chronic quinolone use in cancer patients is a major selective pressure for resistance, other undetermined but distinct selective pressures appear to be more responsible for reduced susceptibility to fluoroquinolones in E. coli.

Risk factors for antibiotic-resistant Escherichia coli isolated from hospitalized patients with urinary tract infections: a prospective study

From November 1998 to February 1999 we prospectively evaluated the prevalence of resistance to penicillins, cephalosporins, carbapenem, quinolones, aminoglycosides, and trimethoprim-sulfamethoxazole (SXT) in 320 Escherichia coli isolates isolated from hospitalized patients with acute urinary tract infections (UTIs). We also studied for these strains risk factors for resistance to amoxicillin-clavulanic acid (AMC), fluoroquinolones (FQs), and SXT. Resistance rates were consistent with those from major recent studies reported in the literature. Multivariate analyses selected the following factors as being significantly associated with E. coli resistance: (i) for resistance to AMC, prior (1 year) UTI (odds ratio [OR] = 2.71, P = 0.006), prior (1 year) urinary catheter (OR = 2.98, P = 0.0025), and prior (6 months) antibiotic exposure (OR = 2.68, P = 0.005); (ii) for resistance to FQs male sex (OR = 3.87, P = 0.03), with a trend toward significance for age >65 years (OR = 7.67, P = 0.06) and prior (1 year) UTI (OR = 2.98, P = 0.07); and (iii) for resistance to SXT, male sex (OR = 1.91, P = 0.046), hospitalization in an intermediate-term-care unit (OR = 2.18, P = 0.008), and prior (1 year) UTI (OR = 2.03, P = 0.03). Ours results suggest that prior UTI is a common risk factor for resistance to the different antibiotics tested. Although few studies on risk factors for E. coli resistance to antibiotics have been published, careful interpretation of their findings, taking into consideration the population, infection site, and period studied, should contribute to the formulation of a better strategy that can be used to overcome antibiotic resistance.

Molecular epidemiology of multi-resistant Escherichia coli

In this case-control study multi-resistant Escherichia coli isolates were characterized on a molecular level and risk factors for their development were identified. Thirty-two multi-resistant E. coli strains were isolated from the urine of 13 patients attending a renal clinic for chronic urinary tract infection (UTI) and from different sites of 11 terminally ill patients with nosocomial infections hospitalized on five different wards. All 32 isolates were resistant to ciprofloxacin, cotrimoxazole and produced beta-lactamase. All strains contained plasmids of 2-110 MDa of which a 50 MDa and a 100 MDa plasmid were present in 81% of the strains. Pulse-field gel electrophoresis (PFGE) analysis demonstrated 17 genotypes among 32 strains which indicates a polyclonal outbreak with some geographic clustering. Monitoring of patients over the study period showed that either the resident genotype remained the same and that these retained strains underwent changes in their plasmid contents, or that they were replaced by a different genotype after several months of therapy for chronic UTI. Univariate analysis indicated that multi-resistant E. coli develop in the presence of long-term selective ciprofloxacin pressure at a dosing regimen of 250 mg bid for more than 20 days and that treatment with a broad spectrum antimicrobial for more than three days favours the selection of multi-resistant E. coli in the flora of terminally ill patients with multiple disorders.

Issues in the management of resistant bacteria in long-term-care facilities

The prevalence of antibiotic-resistant bacteria in the long-term-care setting and the risk to nursing home residents is still unknown. Few studies have been done in community-based nursing homes, and most have focused on colonization rather than infection rates. Concerns about methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci have been expressed most often, while relatively scant attention has been paid to the problem of antibiotic resistance in gram-negative bacilli. Antibiotic resistance precautions need to be developed for nursing homes that are simple, effective, inexpensive, and recognize the unique rehabilitative and long-term custodial missions of chronic-care facilities.