Michèle Dumoulin

Use of blood culture medium enrichment for synovial fluid culture in horses: a comparison of different culture methods.

REASONS FOR PERFORMING STUDY Standard methods for culturing equine synovial fluid (SF) are often unrewarding. Evidence-based information on the relative efficiency of different systems used for optimisation of isolation of microorganisms from equine SF is lacking. OBJECTIVES To compare the results of different culture systems performed in parallel on SF samples from horses clinically diagnosed with synovial sepsis. METHODS Synovial fluid specimens were collected between February 2007 and October 2008 from all horses admitted to a referral hospital that were clinically diagnosed with synovial sepsis and from control horses. Synovial fluid samples were cultured in parallel by: 1) direct agar culture (DA); agar culture after: 2) lysis-centrifugation pretreatment (LC); 3) conventional enrichment (CE); 4) combined LC/CE; or 5) blood culture medium enrichment using an automated system (BACTEC 9050). RESULTS Ninety SF samples from 82 horses were included, together with 40 control samples. Seventy-one of 90 samples (79%) were culture-positive by using blood culture medium enrichment (BACTEC), which was significantly higher compared to all other methods. BACTEC enrichment was never negative while any of the other methods was positive. Although agar culture following LC and/or CE resulted in a slightly higher number of positive samples compared to DA, this difference was not significant. All control samples were culture negative by the 5 different techniques. Although the majority of samples containing isolates recovered without enrichment, culture results after BACTEC enrichment were available on the same day as for agar culture with or without LC (19/23 samples), while CE postponed recovery by at least one day in 20/23 samples. CONCLUSION Blood culture medium enrichment is superior to other techniques for isolation of bacteria from SF of horses. The use of an automated system allows enrichment without substantially postponing recovery of microorganisms. POTENTIAL RELEVANCE The efficient and fast isolation of microorganisms from infected SF by the BACTEC system allows for rapid susceptibility testing and a more appropriate antibiotic treatment.

Evaluation of an automated blood culture system for the isolation of bacteria from equine synovial fluid

The objective of this study was to evaluate an automated blood culture system for the isolation of microorganisms from infected equine synovial fluid (SF). Samples were collected from 220 severely inflamed synovial joints and classified as either presumably infected (group A: n=149) or not infected (group B: n=71), based on a combination of clinical history, clinical signs and cytological analysis of the SF. Samples were inoculated into blood culture bottles and after incubation were subcultured onto agar media to confirm the results and to facilitate full bacterial identification. Microorganisms were isolated from 107 group A samples (71.8%) and from three group B samples (4.2%). Overall, the detection system identified 117 bottles as positive and 103 as negative, including nine instrument-false-positives and two instrument-false-negatives. The median time-to-detection for Gram-positive bacteria, Gram-negative bacteria, and for fungi was 14.3 (interquartile range [I.R.] 10.0) h, 8.8 (I.R. 12.8) h, and 72.0 (range 60.8-74.8) h, respectively. It was concluded that culture of infected SF using the automated system combines the advantages of enrichment in specialised medium with the rapid detection of bacterial growth.

Viability and cell death of synovial fluid neutrophils as diagnostic biomarkers in equine infectious joint disease: a pilot study.

Synovial fluid samples from culture-confirmed infected joints (n=13), joints with pronounced non-infectious synovitis (n=11) and healthy joints (n=14) were collected from 24 equine patients and seven slaughterhouse horses. The samples from the joints with non-infectious synovitis and healthy joints served as negative controls. After isolation, counting and identification of neutrophils, the percentage viability, and the proportion apoptotic and necrotic neutrophils were determined by flow cytometry. Viability was significantly higher in infected samples compared to the controls. A significant difference in cell death type was observed, with apoptosis predominating in infected joints, and necrosis being more present in joints with pronounced non-infectious synovitis and healthy joints. The results of this pilot study suggest that flow cytometric analysis of neutrophil viability and cell death dynamics may assist the discrimination between infected and non-infected joints.

Upward fixation of the patella in the horse - A retrospective study

The objective of the present study was to assess the incidence of upward fixation of the patella (UFP) in different types of patients and to evaluate the outcome of conservative and surgical treatment for correcting this condition. A particular attempt was made to find out whether corrective trimming and/or shoeing (CTS) is efficient in the conservative treatment of UFP, and whether a longer postoperative resting period reduces the risk of complications after medial patellar desmotomy (MPD). Medical records of 78 horses with intermittent or permanent UFP were analyzed retrospectively. Young animals and ponies were mostly affected, mainly during winter (P < 0.05). Seventy-six horses with UFP were treated conservatively, with follow-up being possible in 64 of them. This treatment, in which CTS seemed the most important aspect, was fully successful in 51.6% of these patients; 20.3% of them improved partially. In case of no response to conservative treatment, or in case of a permanent fixation, MPD was performed in 20 horses, which corrected UFP completely in 17 of the 18 followed-up patients. However, gait abnormalities were seen in seven of those 17 horses postsurgically, but with the incidence being lower in horses that had rested for at least three months (25%) compared to horses that had only rested for less than one month (66.6%). Results indicate that conservative treatment, with special attention for CTS, is worth trying before performing more radical procedures to correct UFP, and that a longer convalescence period after MPD is desirable.