Comparison of the automicrobic system, acridine orange-stained smears, and gram-stained smears in detecting bacteriuria

Abstract

We compared the accuracy of the Gram-stained smear, the acridine orange-stained smear, and the AutoMicrobic system (AMS; Vitek Systems, Inc., Hazelwood, Mo.) in screening for bacteriuria, as detected by conventional cultures. For 1,024 clinical specimens, results with the acridine orange-stained smear and the Gram-stained smear were very similar. When read for the presence of one or more microorganisms or leukocytes per 20 oil immersion fields, both smears were highly sensitive (92.1 and 93.3%, respectively) and moderately specific (70.0 and 61.7%, respectively). Sensitivity was greater for specimens yielding i105 CFU/ml (96.1 and 98.9%, respectively) than for those with 103 to 104 CFU/ml (81.4 and 78.0%, respectively). Preliminary classification based upon the tinctorial and morphological characteristics of the Gram-stained smear was compatible with culture results in nearly all cases. The accuracy of the Gram-stained smears was not influenced by special cleaning of the microscopic slides, or the level of expertise of the microscopist. For 715 specimens, the sensitivity of the AMS in detecting bacteriuria (91.5%) was very similar to that of the stained smears (92.1 and 95.7%, respectively), but the specificity was significantly higher (83.2% versus 42.6 and 70.0%). Detection of microorganisms by the AMS took an average of 6.3 3.0 h. These data suggest that the Gram-stained smear is easily interpreted, very sensitive, acceptably specific, and still the optimal rapid method for screening for bacteriuria in most clinical microbiology laboratories.

Is Endophyte-Plant Co-Denitrification a Source of Nitrous Oxides Emission? —An Experimental Investigation with Soybean

“…Soybeans were grown in brown earth soil (soil pH: 6.4, organic matter: 16.17 g•kg −1 , soil moisture: 45%, and total nitrogen: 0.67 g•kg −1 ) and the average temperature of the sampled plot was 14-18 °C. Aseptic seedlings were prepared as follows: First, all seeds were surface-sterilized, and the final wash buffer was tested by the Acridine Orange Direct Count (AODC) method to ensure that no viable microbes were left [20]. Subsequently, the surface-sterilized seeds were aseptically transplanted into a germ-free potted system (diameter × height: 20 × 10 cm) that had been heat-sterilized at 121 °C for 45 min.…”

“…To remove the plant-surface microorganisms, all plant samples were washed and surface sterilized immediately according to the method described by Xiao [21]. The final wash buffer was tested by AODC to confirm all samples were superficially germ-free [20]. Before the gas collection, sterilized plants were aseptically moved into a chamber unit which contained 0.5 kg of sterilized soil [22].…”

Detection of urinary tract infections by rapid methods.

“…The acridine orange-stained smear has also been evaluated as a rapid microscopic bacteriuria screen (27,47). Hoff et al reported a sensitivity and negative predictive value of 98 and 99%, respectively, for cultures with i104 CFU/ml and suggested that the acridine orange procedure may be a cost-effective method for eliminating the need for culture of urines having <104 CFU/ml (27).…”

“…Hoff et al reported a sensitivity and negative predictive value of 98 and 99%, respectively, for cultures with i104 CFU/ml and suggested that the acridine orange procedure may be a cost-effective method for eliminating the need for culture of urines having <104 CFU/ml (27). However, Lipsky et al found no advantage of acridine orange when compared with results from Gram-stained smears (47). They demonstrated that the diagnostic accuracy was maintained when smears were read by either an expert microbiologist or a relatively inexperienced technician.…”

“…After infancy, bacteriuria in males is uncommon before the age of 50 years. Prostatic obstruction and instrumentation become the major causes of infection among middleaged and older men (47). Inability to empty the bladder completely and seeding of the urinary stream with organisms from the prostate cause persistent or recurrent infection.…”