Towards a phenotypic screening strategy for emerging ß-lactamases in Gram-negative bacilli.

The purpose of this manuscript was to review recent literature and guidelines regarding phenotypic detection of emerging ß-lactamases [extended-spectrum ß-lactamases (ESBLs), AmpC ß-lactamases and carbapenemases] in Gram-negative bacilli (GNB) in order to formulate recommendations on best practice to screen for them. We conclude that chromogenic ESBL screening agar plates are suitable to screen for ESBL-producing Enterobacteriaceae directly from clinical samples. Furthermore, ceftazidime (CAZ) and ceftriaxone or cefotaxime (CTX) are the indicator antimicrobial agents of choice for ESBL detection in GNB. In non-inducible Enterobacteriaceae, the combined double-disk synergy test (CDDST) with at least CTX and CAZ and additionally cefepime as indicators is the preferred ESBL confirmation assay. The two most suitable ESBL confirmation strategies in AmpC co-producing Enterobacteriaceae are adapted CDDSTs: (i) with addition of 3-aminophenylboronic acid to CTX and CAZ disks; and (ii) with addition of cloxacillin (CLOX) to Mueller-Hinton agar. Reduced cefoxitin susceptibility and decreased susceptibility to cefotetan are regarded as suitable screening tests for plasmid-mediated and derepressed AmpC production. A CLOX-based CDDST with CTX and CAZ as indicators is considered to be the best AmpC confirmation assay. Finally, in Enterobacteriaceae isolates we suggest to screen for carbapenemases with a 0.5 µg/mL meropenem screening breakpoint. For class A carbapenemase confirmation, the home-prepared as well as the commercially available boronic acid-based CDDST can be considered. For metallo-ß-lactamase confirmation, ethylene diamine tetra-acetic-acid-based home-prepared assays are recommended. The most suitable method (CDDST or DDST) and indicator antimicrobial agent(s) vary depending on the bacterial genus.

Antimicrobial resistance and spread of multi drug resistant Escherichia coli isolates collected from nine urology services in the Euregion Meuse-Rhine.

We determined the prevalence and spread of antibiotic resistance and the characteristics of ESBL producing and/or multi drug resistant (MDR) Escherichia coli isolates collected from urine samples from urology services in the Euregio Meuse-Rhine, the border region of the Netherlands (n=176), Belgium (n=126) and Germany (n=119). Significant differences in resistance between the three regions were observed. Amoxicillin-clavulanic acid resistance ranged from 24% in the Netherlands to 39% in Belgium (p=0.018), from 20% to 40% (p<0.004) for the fluoroquinolones and from 20% to 40% (p=0.018) for the folate antagonists. Resistance to nitrofurantoin was less than 5%. The prevalence of ESBL producing isolates varied from 2% among the Dutch isolates to 8% among the German ones (p=0.012) and were mainly CTX-M 15. The prevalence of MDR isolates among the Dutch, German and Belgian isolates was 11%, 17% and 27%, respectively (p< =0.001 for the Belgian compared with the Dutch isolates). The majority of the MDR and ESBL producing isolates belonged to ST131. This study indicates that most antibiotics used as first choice oral empiric treatment for UTIs (amoxicillin-clavulanic acid, fluoroquinolones and folate antagonists) are not appropriate for this purpose and that MDR strains such as CTX-M producing ST131 have spread in the entire Euregion. Our data stress the importance of ward specific surveillance to optimize empiric treatment. Also, prudent use of antibiotics and further research to alternative agents are warranted.

Lactobacilli vs antibiotics to prevent urinary tract infections: a randomized, double-blind, noninferiority trial in postmenopausal women.

BACKGROUND: Growing antibiotic resistance warrants studying nonantibiotic prophylaxis for recurrent urinary tract infections (UTIs). Use of lactobacilli appears to be promising. METHODS: Between January 2005 and August 2007, we randomized 252 postmenopausal women with recurrent UTIs taking part in a double-blind noninferiority trial to receive 12 months of prophylaxis with trimethoprim-sulfamethoxazole, 480 mg, once daily or oral capsules containing 109 colony-forming units of Lactobacillus rhamnosus GR-1 and Lactobacillus reuteri RC-14 twice daily. Primary end points were the mean number of symptomatic UTIs, proportion of participants with at least 1 UTI during 12 months, time to first UTI, and development of antibiotic resistance by Escherichia coli. RESULTS: The mean number of symptomatic UTIs in the year preceding randomization was 7.0 in the trimethoprim-sulfamethoxazole group and 6.8 in the lactobacilli group. In the intention-to-treat analysis, after 12 months of prophylaxis, these numbers were 2.9 and 3.3, respectively. The between-treatment difference of 0.4 UTIs per year (95% CI, -0.4 to 1.5) was outside our noninferiority margin. At least 1 symptomatic UTI occurred in 69.3% and 79.1% of the trimethoprim-sulfamethoxazole and lactobacilli participants, respectively; median times to the first UTI were 6 and 3 months, respectively. After 1 month of trimethoprim-sulfamethoxazole prophylaxis, resistance to trimethoprim-sulfamethoxazole, trimethoprim, and amoxicillin had increased from approximately 20% to 40% to approximately 80% to 95% in E coli from the feces and urine of asymptomatic women and among E coli causing a UTI. During the 3 months after trimethoprim-sulfamethoxazole discontinuation, resistance levels gradually decreased. Resistance did not increase during lactobacilli prophylaxis. CONCLUSIONS: In postmenopausal women with recurrent UTIs, L rhamnosus GR-1 and L reuteri RC-14 do not meet the noninferiority criteria in the prevention of UTIs when compared with trimethoprim-sulfamethoxazole. However, unlike trimethoprim-sulfamethoxazole, lactobacilli do not increase antibiotic resistance. TRIAL REGISTRATION isrctn.org Identifier: ISRCTN50717094.

Cranberries vs antibiotics to prevent urinary tract infections: a randomized double-blind noninferiority trial in premenopausal women.

BACKGROUND: The increasing prevalence of uropathogens resistant to antimicrobial agents has stimulated interest in cranberries to prevent recurrent urinary tract infections (UTIs). METHODS: In a double-blind, double-dummy noninferiority trial, 221 premenopausal women with recurrent UTIs were randomized to 12-month prophylaxis use of trimethoprim-sulfamethoxazole (TMP-SMX), 480 mg once daily, or cranberry capsules, 500 mg twice daily. Primary end points were the mean number of symptomatic UTIs over 12 months, the proportion of patients with at least 1 symptomatic UTI, the median time to first UTI, and development of antibiotic resistance in indigenous Escherichia coli. RESULTS: After 12 months, the mean number of patients with at least 1 symptomatic UTI was higher in the cranberry than in the TMP-SMX group (4.0 vs 1.8; P = .02), and the proportion of patients with at least 1 symptomatic UTI was higher in the cranberry than in the TMP-SMX group (78.2% vs 71.1%). Median time to the first symptomatic UTI was 4 months for the cranberry and 8 months for the TMP-SMX group. After 1 month, in the cranberry group, 23.7% of fecal and 28.1% of asymptomatic bacteriuria E coli isolates were TMP-SMX resistant, whereas in the TMP-SMX group, 86.3% of fecal and 90.5% of asymptomatic bacteriuria E coli isolates were TMP-SMX resistant. Similarly, we found increased resistance rates for trimethoprim, amoxicillin, and ciprofloxacin in these E coli isolates after 1 month in the TMP-SMX group. After discontinuation of TMP-SMX, resistance reached baseline levels after 3 months. Antibiotic resistance did not increase in the cranberry group. Cranberries and TMP-SMX were equally well tolerated. CONCLUSION: In premenopausal women, TMP-SMX, 480 mg once daily, is more effective than cranberry capsules, 500 mg twice daily, to prevent recurrent UTIs, at the expense of emerging antibiotic resistance. TRIAL REGISTRATION: isrctn.org Identifier: ISRCTN50717094.

Comparison of Vitek identification and antifungal susceptibility testing methods to DNA sequencing and Sensititre YeastOne antifungal testing.

The colorimetric Vitek 2 YST card and the yeast susceptibility test (AST-YS01) were evaluated for their identification efficacy and their use in assessing the in vitro susceptibility of Candida spp. to fluconazole, voriconazole and amphotericin B. Ninety-one percent or 62 of 68 Candida isolates from blood specimens were correctly identified, as compared to determinations of the ITS2 fragment length. The overall essential agreements between Vitek 2 and the Sensititre YeastOne (SYO) colorimetric method were 78.4%, 84.6% and 90.8%, for fluconazole, voriconazole and amphotericin B, respectively. The overall categorical agreements between Vitek 2 and SYO for fluconazole and voriconazole were 76.9% and 96.9%, respectively. The poorest agreement between Vitek 2 and SYO was seen with C. glabrata (n = 27), particularly for fluconazole. The MIC values of 2 C. glabrata strains (3%) could not be determined with the Vitek 2 due to an insufficient growth in the control well. For other Candida species (n = 38) Vitek 2 and SYO showed acceptable agreements.

Staphylococcus aureus carriage among GPs in The Netherlands.

BACKGROUND: The extent to which GPs serve as a reservoir for antibiotic-resistant Staphylococcus aureus is unknown and not well studied. AIM: To determine the prevalence of nasal S. aureus carriage among GPs in the Netherlands, as well as the antimicrobial resistance and the genotypes of isolated S. aureus. DESIGN OF STUDY: Observational, point-prevalence, and cross-sectional study. SETTING: GPs attending the annual conference of the Dutch College of General Practitioners in 2006. METHOD: Nasal swabs were randomly taken from 395 GPs and analysed for the presence of S. aureus. Antimicrobial susceptibility was determined by a microbroth dilution method and the genotypes by spa typing, which was associated with multilocus sequence typing. RESULTS: Of the GPs, 129/395 (33%; 95% confidence interval [CI] = 28 to 37%) were carriers of S. aureus. No meticillin-resistant S. aureus (MRSA) was found. Resistance was observed to penicillin (71%; 95% CI = 63 to 79%), fusidic acid (7%; 95% CI = 3 to 13%), and clarithromycin (6%; 95% CI = 3 to 12%). In 72% of the isolates, an MRSA-related genotype of S. aureus was found. CONCLUSION: The low antibiotic resistance found among S. aureus of GPs suggests that GPs are not a reservoir of antibiotic-resistant S. aureus strains. The relatively high resistance to fusidic acid, which has not previously been described in the Netherlands and is mostly because of antibiotic use, suggests that patients infect GPs and not the other way round. GPs may be at risk for nasal carriage of S. aureus with an MRSA-related genotype.

Trends in antimicrobial susceptibility of Escherichia coli isolates from urology services in The Netherlands (1998-2005).

OBJECTIVES: An increase in antibiotic resistance of Escherichia coli, the most common pathogen in urinary tract infections (UTIs), is encountered worldwide. Optimal treatment of UTIs will contribute substantially to limit antibiotic use and antimicrobial resistance. This study determined trends in antimicrobial resistance of uropathogenic E. coli, which can be of use to optimize UTI guidelines. METHODS: During 1998-2005, E. coli from urine samples of patients attending urology services were collected in three regions in The Netherlands: north-east (NE, n = 1084), west (W, n = 1064) and south (S, n = 1212). The antibiotic susceptibility was determined using microbroth dilution following CLSI guidelines. E. coli ATCC 35218 and ATCC 25922 were used as reference strains. RESULTS: Amoxicillin resistance remained stable over time (37% to 47%), but was higher in the south (44%) compared with the other regions (40%; P < 0.02). Resistance to piperacillin increased from 4% (1998) to 32% (2005; P < 0.001), and resistance to fluoroquinolones increased from 6% to 13% (P < 0.01). Interregional differences were observed for resistance to piperacillin (NE 10%, W 12%, S 14%; P < 0.05) and to fluoroquinolones (NE 7%, W 13%, S 8%; P < 0.001). Trimethoprim +/- sulfamethoxazole resistance remained stable (27% to 37%), as did that of nitrofurantoin (4% to 9%). The percentage of strains with multidrug resistance (resistance to three or more groups of antibiotics) for each region increased over time (P < 0.05). CONCLUSIONS: Antibiotic resistance was fairly constant over time for most agents tested, except for piperacillin and the fluoroquinolones. Regional differences were observed for several compounds. National and regional surveillance of antibiotic resistance is important to keep therapeutic guidelines up-to-date and adequate for the treatment of resistant microorganisms.

Evaluation of the nitrite and leukocyte esterase activity tests for the diagnosis of acute symptomatic urinary tract infection in men.

For 422 male patients with symptoms indicative of a urinary tract infection, nitrite and leukocyte esterase activity dipstick test results were compared with results of culture of urine samples. The positive predictive value of a positive nitrite test result was 96%. Addition of results of the leukocyte esterase test did not improve the diagnostic accuracy of the nitrite test.

Urinary tract infections in general practice patients: diagnostic tests versus bacteriological culture.

OBJECTIVES: Urinary tract infections (UTIs) are common bacterial infections encountered in general practice. For the optimal treatment the general practitioner (GP) should rely on the results of diagnostic tests and recent antimicrobial susceptibility of uropathogens. PATIENTS AND METHODS: In total 1993 female patients (11-70 years) with complaints of an acute uncomplicated UTI were included. The performance characteristics of the diagnostic tests used were determined and compared with the antibiotic prescription rate. The antibiotic therapy (agent and duration), the uropathogens and the antibiotic susceptibility of Escherichia coli were determined for each age group. RESULTS: The positive predictive value (PPV) (96%) and the specificity (94%) of the nitrite test were high for all samples. A negative nitrite with a positive leucocyte-esterase (LE) test showed a high PPV (79%) and sensitivity (82%). When both nitrite and LE tests were negative approximately 50% of the samples were culture positive. Of the patients, 94% of those with a positive nitrite test and 71% of those with a negative nitrite and positive LE test were prescribed antibiotics, mostly nitrofurantoin and trimethoprim. Nitrofurantoin prescriptions decreased and those of fluoroquinolones increased with increasing age. Nitrofurantoin was equally prescribed for 3-7 days in all patients. Trimethoprim was mostly prescribed for 3 days in patients aged 21-50 years and for 5 days in the other patients. E. coli, the uropathogen mostly isolated, decreased in frequency with increasing age. Proteus mirabilis was found more in the oldest patients and Staphylococcus saprophyticus in the younger patients. The antimicrobial susceptibility of E. coli was not age related. The lowest percentages were found for amoxicillin (67%) and trimethoprim (77%). Fluoroquinolone resistance was emerging in the older patients. CONCLUSIONS: For female patients with symptoms of an acute uncomplicated UTI a positive nitrite test or a negative nitrite test with a positive LE test confirmed UTI whereas a negative nitrite together with a negative LE test did not rule out infection. For empirical treatment GPs should take into account the changing aetiology with increasing age. Prudent use of antibiotics in general and more specifically fluoroquinolones remains recommended. As trimethoprim resistance reached 20% it might be advisable to no longer use it as therapy of first choice for acute uncomplicated UTIs in The Netherlands.

Antibiotic treatment and resistance of unselected uropathogens in the elderly.

A population-based study was conducted among women over the age of 70 years with complaints of uncomplicated urinary tract infections (UTIs). The positive predictive value of the nitrite test alone or in combination with the leukocyte esterase test ranged between 83% and 99%. The nitrofurantoin prescription rate decreased whereas fluoroquinolone and amoxicillin/clavulanic acid prescriptions increased with increasing age. The aetiology of infection was age-dependent. Escherichia coli was the most commonly isolated uropathogen, followed by Proteus mirabilis and Klebsiella pneumoniae. For these uropathogens, the lowest susceptibility percentages were found for amoxicillin, trimethoprim and co-trimoxazole. As trimethoprim susceptibility reached approximately 75%, it may be advisable not to use this as a first-choice agent in the treatment of uncomplicated UTIs in the elderly.

Acute uncomplicated lower urinary tract infections in general practice: clinical and microbiological cure rates after three- versus five-day treatment with trimethoprim.

OBJECTIVES: Epidemiological studies indicate that acute uncomplicated urinary tract infections (UTI) in women can be successfully treated with short treatment regimens. However, the findings from the literature do not match experiences in daily practice. METHODS: A randomised, controlled trial evaluating the microbiological and clinical (self-reported) cure rates of a three-day vs. five-day treatment regimen with trimethoprim for UTI in women. RESULTS: No statistically significant difference in bacteriological cure rate was found between the three-day and five-day regimen. One day after the shorter regimen 44% of women considered themselves as 'not-recovered' due to persistence of the symptoms compared with 35% after the five-day treatment (p > 0.05). Three days after therapy these percentages were 30 and 25% respectively. CONCLUSION: The relatively high percentage of persistent symptoms one day after the three-day regimen might be responsible for general practitioners believing that short regimens are not successful. It is therefore advisable that if urine samples are controlled to wait at least three days after finishing treatment.