Adaptation of Microstix®-Candida slide-test for diagnosis of bovine mastitis due to anascogenic yeasts

Abstract

Although a large diversity of mastitis-causing bacteria (150 species, subspecies or biovars) have been documented, an adequate and simple mycological screening for yeast-related mastitis has not been developed. Since yeast incubation normally lasts longer than the majority of bacteriological ones, usually a treatment is administered before the results of microbial cultures are obtained. Therefore, a simple test has been needed for detection of yeast-related mastitis, the results of which can be read in parallel to bacteriological screening. Application of Microstix®-Candida assay was first checked for its specificity in standard Candida albicans (Oxford strain) cultures (phase I) and then in the other 36 strains of yeasts isolated from clinical mastitis cases during field investigations (second phase). Next, a test was implemented for identification of pathogens in 9 cohorts (1,200 cows) from red-white Polish-Friesian breed in which the dynamics of mastitis were traced by bacteriological and mycological assays along year-long observations. The data obtained showed that apart from frequent infections (∼50-70%) proved by using pure microbial cultures, also mixed (bacterial-fungal) infections (0-25%) appeared as well as negative sieves (in the range of 0-45%). Mycological assays revealed a significant fraction of mixed infections during both lactation and the dry period. Strepto-staphylococcal infection was thus identified, however, its proportion strongly decreased after the introduction of antibiotics (after sensitivity to microbial agents was determined). Microbial monitoring was improved in these herds by parallel application of bacteriological and mycological (particularly Microstix®-Candida) tests. Microstix®-assay appears to be useful for mycological diagnosis in field conditions of infected (mastitis) herds. Its advantages include easy performance and short incubation time that is only 24 h at 37 °C (72-96 h at room temperature). This allowed demonstrating the cow's udder yeast infection simultaneously with the first reading of bacterial cultures. Its specificity was confirmed against standard Candida Oxford strain, and sensitivity (100%) was confirmed in mycological cultures (36 strains) and biochemical assays.