Investigation of the use of cytobrush for cytological and bacteriological diagnosis of endometritis in mares

Combined microbial and cytological examination of uterine samples is the diagnostic mainstay of infectious endometritis in the mare [1]. Use of a single instrument to perform both samplings could be an economical and practical alternative in the field [2]. Aims of this study were to describe a technique for the collection and processing of endometrial samples by cytobrush (CB) for both cytological and microbiological examinations and to evaluate its feasibility, accuracy and reliability in the diagnosis of endometritis in the mare. Uterine sampling by CB was performed in 33 Standardbred mares. The first 10 mares were sampled with a double-guarded cotton swab (CS) and CB as previously described [3]. In the field, brush was rolled onto a sterilized glass slide (FS) and then it was immersed in 4ml of sterile saline solution. In the lab, the brush and the pellet obtained by the saline centrifugation were rolled onto glass slides (LS and PS). Smears were evaluated for background, quality of the cells harvested, total cellularity and neutrophils (PMN), ratio PMN/uterine epithelial cells and inflammatory scores. Brush and pellet were incubated in enrichment broth, whereas CS was incubated in enrichment broth and directly plated onto blood agar plate. Cytological data obtained by the examination of FS, LS and PS were compared; the agreement between culture results from CS (BCS), CB (BCB) and pellet (BBP) were evaluated. Smears from pellet (PS) were always not diagnostic. Total cellularity, neutrophils, background and inflammatory scores were significantly higher in FS than in LS, whereas quality scores did not differ. The agreement between BCS and BCB was excellent (k=1) in both positive and negative cultures; significantly more positive culture were obtained by BCB and the agreement between BCB and BBP was moderate (k=0.43). Sample collection by cytobrush (CB) was considered the preferred method of cytological smears for use in the field [3]. Our cytological examinations on smears made using the cytobrush in the field (FS) yielded good cellularity and high reliability for diagnosis of endometritis. Even if the use of exfoliative cytology combined with samples collection for culture is poorly described [2,4], our study showed that a double-guarded brush can be used to perform both sampling simultaneously. In order to minimize the risk of contamination a proper procedure should be used. In our results, with this procedure suitable samples for bacteriological examinations were obtained. A culture enrichment broth of both brush and pellet are recommended to ensure more information. The diagnostic interpretation of positive culture data after enrichment must be completed in accordance with cytological results and clinical signs of the mare.