Stool samples for parasitological examination were collected in a remote area of western Nepal. Of 40 specimens collected, 36 were positive for parasites as determined by examination of direct wet mounts and trichrome smears. All but one of the positive specimens contained several parasite species, averaging four species per specimen. Four negative specimens were found in infants under 1 year of age. The parasitic burden in this population appeared to be high, and the prevalence of parasitic infection approached 100%.
To review the appropriateness of standard reference procedures for diagnostic parasitology, we examined 2,206 stool specimens in our laboratory by direct wet mounting with saline and iodine, by saline and iodine wet mounting from Formalin-ethyl acetate concentrates, and by permanent staining with Wheatley's modified trichrome method (W.B. Wheatley, Am. J. Clin. Pathol. 21: 990-991, 1951). Parasites were detected in 98 stool specimens (4.4%). In all but three specimens, direct wet mounting with saline and iodine contributed little significant information to the result yet consumed substantial technical time. We recommend that with preserved feces a direct examination not be performed but that examination of both a concentrate and a permanent stain be routine.
A rapid screening test (45 min) for bacteriuria was evaluated in 1,000 clinical urine specimens. The test procedure is based upon firefly luciferase analysis of bacterial ATP and uses the Lumac kit and Lumac M2010 Biocounter (3M Co., St. Paul, Minn.). The procedure allows for removal and destruction of nonbacterial ATP and subsequent analysis of bacterial ATP by firefly luciferase with a single photon counter. Results, expressed in relative light units, were compared with actual CFU by the calibrated loop technique. Sensitivities and specificities were calculated separately for clean-catch midstream specimens and for urines obtained by catheterization. The sensitivity for 719 clean-catch specimens with a Lumac cutoff of 2500 relative light units, representing 2 105 CFU/ml, was 93%. The sensitivity for 281 catheterized specimens with a Lumac cutoff of 2200 relative light units, representing i104 CFU/ml, was 95%. There were 19 false-negative results in the 1,000 specimens tested; more than 50% of these were contaminated cultures and were not considered significant in determining bacteriuria. In conclusion, the Lumac bioluminescence assay is a reliable, rapid bacteriuria screening technique with the potential of reducing the laboratory cost and for reducing the turnaround time in processing negative urine cultures.
A total of 258 formalinized stool specimens received in our clinical laboratory were examined for parasites by direct smears and by the standard Formalin-ethyl acetate (FEAc) concentration method. Microconcentration (MC), a miniaturization of the FEAc method, was compared with the standard method for efficiency of parasite recovery. MC employed 0.25 to 0.50 ml of formalinized stools, 0.5 ml of Formalin, and 0.25 ml of ethyl acetate; the washing steps were omitted, whereas the rest of the procedure remained the same as the FEAc method. A total of 36 (13.9%) specimens were positive for parasites; of these, 23 (63.9%) were negative on direct examination. In 14 of these 23 specimens, the FEAc and MC methods were equivalent in detecting parasites. MC failed to detect parasites in eight specimens that were positive by FEAc and detected a parasite in one specimen that was negative by FEAc. Of 14 specimens positive by both concentration methods, FEAc detected additional parasite species in 2 specimens and MC did so in 1 specimen. The reduced sensitivity of parasite concentration evident in the MC we believe to be exclusively due to the drastically reduced sample size. We propose MC as an alternative to the FEAc concentration method when only small amounts of feces can be obtained.
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