Comparison of routine urinalysis and urine Gram stain for detection of bacteriuria in dogs.

OBJECTIVE: To determine the utility of performing urine Gram stain for detection of bacteriuria compared to routine urine sediment examination and bacterial aerobic urine culture. DESIGN: Prospective, observational study. SETTING: University teaching hospital. ANIMALS: Urine samples acquired via cystocentesis through convenience sampling from 103 dogs presenting to a tertiary referral institution. INTERVENTIONS: All samples underwent routine urinalysis, including sediment examination, as well as urine Gram stain and quantitative bacterial aerobic urine culture. MEASUREMENTS AND MAIN RESULTS: The urine Gram stain demonstrated improved sensitivity (96% versus 76%), specificity (100% versus 77%), positive predictive value (100% versus 83%), and negative predictive value (93% versus 69%) when identifying bacteriuria, compared to routine urine sediment examination. CONCLUSIONS: The urine Gram stain is highly sensitive and specific when detecting the presence of bacteria in canine urine samples. Gram staining should be considered when bacteriuria is highly suspected and requires rapid identification while bacterial culture is pending.

The microbiology of bacteriuria in men: a 5-year study at a Veterans' Affairs hospital.

Bacteriuria and urinary tract infection occur relatively frequently in older men, but data regarding the causative microorganisms are limited. We retrospectively identified all positive cultures of urine specimens (n = 4943) obtained over a 5-year period at our institution. We determined the frequency of causative microorganisms and grouped these by Gram type, setting of patient care, and method of urine specimen collection. We also assessed the performance characteristics of the Gram-stained smear of uncentrifuged urine. Among our patients, Gram-positive cocci (GPC) were isolated as often as Gram-negative rods (GNR). Escherichia coli was the single or predominant isolate in only 14% of cases, and Enterococcus was the single most commonly identified genus (22.5%). The Gram stain was accurate in predicting the culture results (positive likelihood ratio, 7.0 for GPC and 8.1 for GNR). We conclude that the microorganisms causing bacteriuria in older male veterans are substantially different from those found in women, and the Gram-stained smear provides useful information on the causative organisms.

Analysis of malachite green and metabolites in fish using liquid chromatography atmospheric pressure chemical ionization mass spectrometry.

Malachite green (MG), a traditional agent used in aquaculture, is structurally related to other carcinogenic triphenylmethane dyes. Although MG is not approved for use in aquaculture, its low cost and high efficacy make illicit use likely. We developed sensitive and specific methods for determination of MG and its principal metabolite, leucoMG (LMG), in edible fish tissues using isotope dilution liquid chromatography atmosphere pressure chemical ionization mass spectrometry. MG and LMG concentrations were measured in filets from catfish treated with MG under putative use conditions (ca. 250 and 1000 ppb, respectively) and from commercial trout samples (0-3 and 0-96 ppb, respectively). Concentrations of LMG in edible fish tissues always exceeded those of MG. A rapid cone voltage switching acquisition procedure was used to simultaneously produce molecular ions for quantification and diagnostic fragment ions for confirmation of MG and metabolites. The accurate and precise agreement between diagnostic ion intensity ratios produced by LMG in authentic standards and incurred fish samples was used to unambiguously confirm the presence of LMG in edible fish tissue. This suggested the validity of using LMG as a marker residue for regulatory determination of MG misuse. Additional metabolites derived from oxidative metabolism of MG or LMG (demethylation and N-oxygenation) were identified in catfish and trout filets, including a primary arylamine which is structurally related to known carcinogens. The ability to simultaneously quantify residues of MG and LMG, and to confirm the chemical structure of a marker residue by using LC/MS, suggests that this procedure may be useful in monitoring the food supply for the unauthorized use of MG in aquaculture.

Determination of gentian violet in animal feed, human urine, and wastewater by high pressure liquid chromatography.

Sensitive and specific procedures are described for the analysis of residues of gentian violet in animal feed, human urine, and wastewater at levels of 1000 ppm down to 10 ppb, 1 ppb, and 10 ppb, respectively. The cleaned-up extracts were analyzed by reverse-phase high pressure liquid chromatography by using an absorption detector at 588 nm. Recoveries of the compound from animal feed, human urine, and wastewater at the 10 ppb level were 79%, 58%, and 60%, respectively. Information concerning the stability of the compound in animal feed and the efficiency of extracting the residues is presented. Ancillary information is also reported concerning the separation and analysis of six related triphenylmethane dyes.