ABSTRACT
Objective To evaluate the practicability of CHROMagar orientation medium combined with simple biochemical tests for identification of common oxidase-negtive gram-negative bacilli.Methods The CHROMagar orientation medium was used together with biochemical tests including indole test , ornithine decarboxylase test and lysine decarboxylase test for identification of common oxidase -negtive gram-negative bacilli.The sensitivity, specificity, likelihood ratio, Youden index and Kappa value of the diagnostic assays were evaluated .McNemar test was performed to evaluate facticity, accuracy and cost of the method in com-parison with the Vitek-2 system as reference method .Results The identification of oxidase-negtive gram-negative bacilli from 318 bacterial strains showed that the sensitivities and specificities of CHROMagar orien-tation mediumm in combination with simple biochemical tests to Serratia marcescens, Stenotrophomonas mal-tophilia and Acinetobacter baumannii reached 100%, and for Escherichia coli, Enterobacter aerogenes and Klebsiella pneumoiae were above 90%.The specificities for identification of Enterobacter cloacae, Klebsiella oxytoca, Citrobacter freundii and Proteus mirabilis were all above 90%, but the sensitivities were around 75%-90%.Kappa values of the assays were above 0.85, howerer, which was only 0.5947 for Citrobacter freundii.McNemar test showed that all P values were above 0.05, and cost of the assays was reduced by 90%.Conclusion CHROMagar orientation medium in combination with simple biochemical tests is a cost-effective assay for identification of common oxidase-negtive gram-negative bacilli .
ABSTRACT
BACKGROUND: Urine cultures are among the most numerous of culture types for microbiology studies. In this study, we evaluated the utility of CHROMagar Orientation (CO; Becton Dickinson, Cockeysville, MD, USA), a new chromogenic medium, for the detection, enumeration, and presumptive identification of urinary tract pathogens. METHODS: The 438 clinical urine samples sent for routine culture were plated onto CO and Bi-plate (blood/MacConkey agar). We compared the detection and enumeration of potential pathogens, and the agreement between presumptive identification directly from CO and the confirmative identification, which was performed using conventional biochemical tests and Vitek system. RESULTS: The detection rate of urinary tract pathogens on all two media, CO and Bi-plate were nearly identical. The enumeration of colony counts was consistent on the two media for 102 of the 108 (94%) microorganisms. Colony color and morphology on CO accurately differentiated Escherichia coli and Enterococcus spp. The overall agreement of presumptive identification on CO was 91 of the 108 (84%). CONCLUSION: The CO enabled accurate detection, count determination, and presumptive identification of common urinary pathogens, both in pure and mixed cultures.
Subject(s)
Enterococcus , Escherichia coli , Urinary TractABSTRACT
BACKGROUND: Urine samples should be tested in a rapid and cost-effective way, as they represent the largest volume of specimens cultured in the microbiology laboratory. Some bacteria can be presumptively identified with CHROMagar Orientation (CO) according to the specific colors produced on the colonies. In this study, the usefulness of CO agar was evaluated for urine cultures. METHODS: The urine samples from 980 patients from March through April, 2004 were inoculated on blood agar (BAP), MacConkey agar, and CO agar plates, and we compared the detection rates of potential pathogens and the agreement between presumptive identification directly from the CO agar and the confirmative idntification, which was performed using Vitek systems (bioMerieux). RESULTS: The detection rates of urinary tract pathogens on all three media, conventional BAP, MacConkey agar and CO agar were identical (18.9%). All isolates of Escherichia coli (54) and ente-rococci (40) were correctly identified with CO agar. The overall agreement of presumptive identification was 87.4% (187/199). CONCLUSIONS: Use of the CO agar enabled a rapid presumptive identification of E. coli, and ente-rococci, the most common urinary tract pathogens. The CO agar is cost-effective by saving some of the bacterial identification kits that would be required for the conventional BAP and MacConkey agar method.
Subject(s)
Humans , Agar , Bacteria , Escherichia coli , Urinary TractABSTRACT
OBJECTIVE To investigate the function of CHROMagar orientation medium for quick detection of(urinary) tract pathogens.METHODS The comparative experiment was performed with CHROMagar orientation(medium) and 5% sheep blood agar for clinical urine specimens from the patient with suspective urinary tract(infections).RESULTS Among the total of 1369 clinical urine specimens,1023 specimens yielded no growth,344 specimens yielded growth on both media,and 2 other specimens yielded no growth on blood agar but yielded growth on CHROMagar orientation medium.CONCLUSIONS The growth of bacteria is not inhibited by the(orientation) medium and no significant differences were found in the results between the both media.The(orientation) medium can quickly confirm the genus of the pathogens,and it has significance for using antibiotics(reasonably).One of the greatest advantages of this medium is the easy recognition of mixed cultures.