Urinary Concentrations and Bactericidal Activity Against Amoxicillin-Nonsusceptible Strains of Escherichia coli with Single-Dose, Oral, Sustained-Release Amoxicillin/Clavulanic Acid: A PhaseI, Open-Label, Noncomparative Clinical Trial in Healthy Volunteers

BACKGROUND

Urinary tract infections (UTIs) account for 5 to 6 million medical consultations in the United States each year. Worldwide, an estimated 20% to 30% of women aged 20 to 40 years have at least 1 episode of the most common type of UTI (uncomplicated cystitis) in their lifetime, with Escherichia coli being the causative pathogen in 80% of cases. Antibacterial activity in urine has been shown to be correlated with outcomes of uncomplicated cystitis.

OBJECTIVE

The objectives of this study were to determine urinary concentrations and ex vivo bactericidal activity of sustained-release (SR) amoxicillin/clavulanic acid 2000/125 mg against intermediately resistant and resistant strains of E coli over 72 hours and compare them with those of a susceptible strain. This study also investigated whether urinary concentrations obtained after dosing cover E coli strains categorized as intermediately resistant and resistant based on current Clinical and Laboratory Standards Institute (formerly NCCLS) breakpoints in uncomplicated cystitis.

METHODS

This Phase I, open-label, noncomparative study in healthy male volunteers was conducted at the Pharmacology Unit, Autónoma University, Madrid, Spain. Subjects received a single oral dose of amoxicillin/clavulanic acid 2000/125 mg SR. The amoxicillin/clavulanic acid MICs were 8/4 microg/mL (susceptible), 16/8 microg/mL (intermediately resistant), and 32/16 and 64/32 microg/mL (resistant). Urine samples were collected before (baseline; time 0) and at the following intervals: 0-2, 2-4, 4-8, 8-12, 12-16, 16-24, 24-36, 36-48, 48-60, and 60-72 hours after dosing. Killing curves with urine samples were performed with initial inocula of approximately 10(7) colony-forming units (CFU)/mL, and bactericidal activity (defined as >3 log(10) CFU/mL and >99.9% reduction in bacterial counts) was calculated as the difference between log(10) initial inoculum and log(10) CFU/mL after 4 hours of incubation of each sample.

RESULTS

Twelve volunteers were included (mean [SD] age, 24.83 [5.64] years; mean [SD] height, 175.75 [7.56] cm; and mean [SD] weight, 73.55 [9.19] kg). No statistically significant differences between the activities in the 12-16-hour interval compared with baseline were found in any of the strains tested. Bactericidal activity against the susceptible and intermediately resistant strains (MICs 8/4 and 16/8 g/mL, respectively) was obtained up to 8 hours after dosing. Bactericidal activity against the resistant strains (MICs 32/16 and 64/32 microg/mL) was obtained in the 2-4-hour interval.

CONCLUSIONS

In this Phase I study in healthy volunteers, urinary concentrations after dosing with amoxicillin/clavulanic acid 2000/125 mg SR showed bactericidal activity against the amoxicillin-susceptible and intermediately resistant strains of E coli.

Influence of shaking on antifungal susceptibility testing of Cryptococcus neoformans: a comparison of the NCCLS standard M27A medium, buffered yeast nitrogen base, and RPMI-2% glucose

Cryptococcus neoformans is a nonfermentative yeast that requires oxygen for growth. The shaking of culture media achieves good oxygenation, promoting the growth of cryptococci. In this study, three test media (RPMI 1640, RPMI 1640-2% glucose, and buffered yeast nitrogen base ¿BYNB) recommended in the National Committee for Clinical Laboratory Standards M27A standard were examined. Growth abilities and minimum inhibitory concentrations (MICs) in microplates incubated at 35 degrees C for 48 h were determined. The results indicated that shaking and an inoculum size of 10(5) CFU/ml yielded optimal growth of this yeast. Compared to RPMI 1640, supplementation of RPMI 1640 with 2% glucose did not significantly improve growth of C. neoformans and resulted in an 8.7-h delay of exponential growth. Cryptococcal growth in RPMI 1640 at 24 h was notably better than that in RPMI-2% glucose, although by 48 h the growths were comparable. The MIC range of amphotericin B observed for the C. neoformans strains grown in RPMI 1640 with or without glucose was too narrow to allow the separation of susceptible and resistant strains based on clinical outcome. The widest ranges of MICs of flucytosine and fluconazole were obtained with BYNB. This work demonstrates the need for a new antifungal susceptibility test for C. neoformans.

[Cutaneous zygomycosis caused by Rhizopus arrhizus in a surgical wound.]

We report a case of cutaneous zygomycosis caused by Rhizopus arrhizus in a surgical wound following colostomy. The patient was a diabetic and in addition presented others risk factors. Zygomycosis was suspected when a necrotic wound surface appeared in the appropiate clinical setting. Diagnosis was confirmed on a combined histological and microbiological study. Extensive surgical resection, high doses of amphotericin B and treatment of the underlying conditions permitted the control of the infection.