Prevention of Postoperative Infections in Horses

In vitro evaluation of the effect of tris-EDTA and 0.0005% chlorhexidine solution on the strength of two absorbable sutures

OBJECTIVE

To determine the effect of 0.0005% chlorhexidine and tris-EDTA solution on the strength of three commonly used suture types for closure of equine ventral midline celiotomy.

STUDY DESIGN

Controlled laboratory study.

SAMPLE POPULATION

Knotted loops (n = 10/group, 150 knot constructs total).

METHODS

Strands of 2 polyglactin 910, 3 polyglactin 910, and 2 polydioxanone were tied to form knotted loops. All knotted loops were mounted on a tabletop force measurement machine system and loaded at 100 mm/min until the breaking force (N) was determined. The breaking force (N) of knotted loops using dry suture was recorded at study start, then of knotted loops soaked in either 0.0005% chlorhexidine and tris-EDTA for 20 min followed by incubation in equine serum (treatment) or serum alone (control) for 14 and 21 days. Analysis of variance (ANOVA) compared the breaking force between the treatment and control groups at each time point.

RESULTS

There was no significant difference in the breaking force of 2 USP polyglactin 910 (p = .35, confidence interval [CI] = -0.21-0.59), 3 USP polyglactin 910 (p = .61, CI = -0.41-0.24), or 2 USP polydioxanone (p = .76, CI = -0.63-0.46) soaked in 0.0005% chlorhexidine and tris-EDTA solution followed by equine serum when compared to each respective suture soaked in equine serum only.

CONCLUSION/CLINICAL SIGNIFICANCE

Since 0.0005% chlorhexidine and tris-EDTA solution did not exhibit a significant effect on the breaking force of the absorbable sutures studied, the solution may be used for incisional lavage in the clinical setting.

Incidence of surgical site infection after internal fixation of the first phalangeal bone and the third metacarpal/metatarsal bone fractures in Thoroughbred racehorses

Surgical site infection (SSI) is one of the major complications of equine fracture surgery. The purpose of this study was to investigate the incidence of and risk factors for SSI after internal fixation of the first phalangeal bone (P1) and the third metacarpal/metatarsal bone (MC3/MT3) fractures in Thoroughbred racehorses. Between 2011 and 2020, 451 cases underwent surgery with screws or a locking compression plate (LCP) for sagittal fractures of P1 or condylar fractures of MC3/MT3. Overall, 2.9% (13/451) of the cases developed an SSI. The incidence was significantly higher in plate fixation (21.4%) than in screw fixation (2.3%). There was no significant association with other variables, such as sex, age, number of screws, experience of surgeon, or prophylactic antimicrobials. The median duration of hospitalization for screw fixation was 14 days without an SSI and 20 days with an SSI, and those for plate fixation were 26 and 25-88 days, respectively, indicating that the development of SSI prolongs the duration of hospitalization. On the other hand, there were no significant differences in discharge and race resumption rates between cases with and without an SSI. These data indicate that the incidence of SSI in this study was low and that it was higher following plate fixation than screw fixation.

Use of Clinical Audits to Evaluate Timing of Preoperative Antimicrobials in Equine Surgery at a Veterinary Teaching Hospital

Based on human surgical guidelines, intravenous antimicrobials are recommended to be administered within 60 min of surgical incision. Achieving this target in horses is reportedly challenging and influenced by hospital policies. The objectives of this study were to evaluate and improve: (1) the timing of antimicrobial administration to surgical incision (tAB-INC), (2) contributions of anesthesia pre-induction (tPRI) and surgical preparation (tPREP) periods to tAB-INC, and the (3) completeness of antimicrobial recording. Two clinical audits were conducted before and after the policy changes (patient preparation and anesthesia record keeping). tPRI, tPREP, and tAB-INC were calculated and compared for elective arthroscopies and emergency laparotomies within and between the audits. The percentage of procedures with a tAB-INC <60 min was calculated. Antimicrobial recording was classified as complete or incomplete. A median tAB-INC <60 min was achieved in laparotomies (audit 1; 45 min, audit 2; 53 min) with a shorter tPREP than arthroscopies (p < 0.0001, both audits). The percentage of procedures with tAB-INC <60 min, tAB-INC, tPRI, and tPREP durations did not improve between the audits. There was a positive correlation between the number of operated joints and tPREP (audit 1, p <0.001, r = 0.77; audit 2, p < 0.001, r = 0.59). Between audits, antimicrobial recording significantly improved for elective arthroscopies (82–97%, p = 0.008) but not emergency laparotomies (76–88%, p = 0.2). Clinical audits successfully quantified the impact of introduced changes and their adherence to antimicrobial prophylaxis guidelines. Antimicrobial recording was improved but further policy changes are required to achieve a tAB-INC <60 min for arthroscopies.

Colloidal Iron Oxide Formulation for Equine Hoof Disinfection

The presence of bacteria of various origins on horse hoofs enables the onset of infections following trauma or even post-surgical wounds. Thus, the analysis of new antibacterial substances is of fundamental importance. In this study, the antibacterial efficacy of Iron Animals (IA), a stable colloidal suspension of iron oxide, organic acids, and detergents, was tested in vitro and in vivo. In vitro assays were performed to test the unspecific inhibitory effect of IA on both gram-positive and gram-negative bacteria monitoring the microorganism growth by spectrophotometry (optical density OD600) at 37 °C for 24 h. In vivo test consists on the quantification of the bacterial load in colony forming units per gram (CFU/g) of specimens collected from the frog region of the anterior hooves of 11 horses. Sampling followed the application of four disinfectant protocols consisting of two consecutive 3 min scrubs with 50 mL of 10% Povidone-iodine (PI) or 4% Chlorhexidine (CHx), with or without an additional application for 15 min of 10 mL of Iron Animals (PI+IA and CHx+IA). In vitro, IA completely suppressed the bacterial growth of all the tested microorganisms, resulting in effectiveness also against CHx-resistant bacteria, such as Staphylococcus aureus. In vivo, PI emerged as an ineffective protocol; CHx was effective in 18% of cases, but with the addition of IA (CHx + IA) its use emerged as the best disinfectant protocol for horse hoof, achieving the lowest bacterial load in 55% of cases. The addition of IA, after PI or CHx, improves the effectiveness of both disinfectants leading to the highest bactericidal activity in 82% of cases.

Use of aminoglycoside antibiotics in equine clinical practice; a questionnaire-based study of current use

Veterinary use of the aminoglycoside antibiotics is under increasing scrutiny. This questionnaire-based study aimed to document the use of aminoglycosides with a particular focus on gentamicin. An online questionnaire was delivered to generalist equine veterinary surgeons and specialists in internal medicine to determine the perceived importance, frequency of use and routes of administration of the aminoglycoside antibiotics. A series of hypothetical scenarios were also evaluated regarding gentamicin. Data were compared to evaluate the impact of the level of specialisation on prescribing practices for different antibiotics using Chi-squared and Fischer's exact tests. Data were analysed from 111 responses. Gentamicin was commonly used empirically without culture and susceptibility testing. Generalists were more likely to use gentamicin only after susceptibility testing than specialists in a variety of clinical presentations including respiratory diseases, septic peritonitis, acute febrile diarrhoea, cellulitis and contaminated limb wounds (p < 0.01). Intravenous administration of gentamicin was most common, although inhaled and regional administration of gentamicin and amikacin were also described. Amikacin was most commonly used by intra-articular administration. Gentamicin was more likely to be used in high-risk procedures or contaminated surgeries (86% and 74%, respectively) compared with clean surgery (32%; p < 0.0001). Gentamicin was often used perioperatively in horses undergoing exploratory celiotomy and more commonly used in horses undergoing an enterotomy (90%) than without and enterotomy (79%; p = 0.04). Most respondents (86%) used gentamicin at a dose of 6.6 mg/kg in adults, with few changing their dosing strategies based on the presence of sepsis, although higher doses were more reported in foals (7-15 mg/kg) irrespective of the presence of sepsis. Aminoglycosides are widely used in equine practice and use outside current EU marketing authorisations is common. Stewardship of the aminoglycoside antibiotics could be enhanced in both generalists and specialists through the more frequent use of susceptibility testing, regional administration and dose adjustment, especially in foals.

Comparison of incisional complications between skin closures using a simple continuous or intradermal pattern: a pilot study in horses undergoing ventral median celiotomy

Background

Development of incisional complications following ventral median celiotomy might depend on suture pattern for skin closure.

Methods

In this prospective study, 21 healthy male horses underwent celiotomy. Skin closure was either performed via a continuous percutaneous pattern (CO group; 5 warmbloods/5 ponies) or an intradermal pattern (ID group; 5 warmbloods/6 ponies). Follow-up examination of the incisional site included daily monitoring for edema, dehiscence, and drainage. Transcutaneous ultrasound was performed at Days 3, 6, and 10 as well as on Week 8 and 12 to evaluate size of edema and presence or absence of sinus formation, and hernia formation. Prevalence of incisional infection on base of positive microbiological analysis at any time up to Day 10 was evaluated and compared between ID and CO group. Furthermore, edema size was analysed by a linear mixed-effect model for group and time dependency.

Results

Observed incisional complications included edema (9/10 in CO, 10/11 in ID), suture sinus formation (2/10 in CO, 1/11 in ID), surgical site infection (2/10 in CO, 0/11 in ID), and incisional hernia (1/10 in CO, 0/11 in ID). The overall prevalence of incisional infection was 9.5% without significant differences between both groups (20% in CO, 0% in ID; p = 0.214). Edema size was not dependent on time or group (p = 0.545 and p = 0.627, respectively).

Discussion

CO and ID suture pattern are appropriate for skin closure following ventral median celiotomy in horses. None of the animals in the continuous ID group developed surgical site infections, even without the use of antibiotics.

A retrospective analysis of the risk factors for surgical site infections and long-term follow-up after transpalpebral enucleation in horses

Background

Implants are often used to improve the cosmetic appearance of horses after enucleation of the eye. When surgical site infection (SSI) occurs, the implant will almost always be lost. The aim of this study is to collect data on the risk factors for SSIs and report long-term follow-up (cosmetic results and return to work) after transpalpebral enucleations. In this retrospective study, records of horses undergoing transpalpebral enucleation were reviewed (2007–2014) and telephone interviews were used to obtain long term follow-up. The potential risk factors for SSIs (indication for enucleation, use of an implant, standing procedures, duration of surgery, opening of the conjunctival sac and prolonged use of antimicrobials) were analysed for their association with the outcome measure ‘SSI’ vs ‘no SSI’ by multivariable binary logistic regression testing. Indications for enucleation were grouped as follows: Group 1 (clean) included equine recurrent uveitis, too small or too large globes, and intraocular tumours, Group 2 (non-clean) included corneal perforation/rupture and infected ulcers and Group 3 (tumour) included extraocular tumours.

Results

One hundred and seven cases of enucleation were evaluated. An implant was used in 49 horses. The overall number of SSIs was 8 (7.5%). Multivariable logistic regression testing showed implants (OR 7.5, P = 0.04) and standing procedures (OR 12.1; P = 0.03) were significantly associated with the percentage of SSIs and increased the risk of SSI. The eyes of horses in Groups 2 and 3 trended towards a larger risk for developing SSIs (OR 4.9; P = 0.09 and OR 5.9; P = 0.1, respectively). Prolonged use of antimicrobials, long surgery times and the opening of the conjunctival sac during dissection did not show significant associations with SSI risk.

Conclusions

The risk of SSI after enucleation is low in clean eyes and when no implant is used. Placing an implant or performing a standing enucleation significantly increases the risk of SSIs. Although implants can be used for eyes that fall into Groups 2 and 3, 17% of the horses in these two groups developed an SSI leading to loss of the implant.

Species identification and antimicrobial resistance of coagulase-negative staphylococci isolated from the meat of sea fish

Seventy-eight isolates of staphylococci obtained from the meat of Theragra chalcogramma, Scomber scombrus, and Clupea harengus were identified and tested in this study. 16S rDNA sequence specific for the genus Staphylococcus was detected in all isolates with the help of PCR method. All of 78 isolates were coagulase-negative, and DNAse activity was only confirmed in 4 of them. The following species of staphylococci were identified using MALDI-TOF mass spectrometry: S. warneri (52%), S. epidermidis (33%), S. haemolyticus (6.4%), S. pasteuri (3.8%), S. sciuri (1.2%), S. capitis (1.2%), and S. hominis (1.2%). Antimicrobial resistance to 7 antibiotics was determined in each isolate with the help of agar dilution method. In general, resistance against ampicillin was observed in majority of isolates (87%). On the contrary, the best sensitivity of CoNS was determined to gentamicin (96%). Only 1 S. warneri strain showed resistance to cefoxitin. Furthermore, 83% of staphylococcal isolates were simultaneously resistant to 2 or more antibiotics.

PRACTICAL APPLICATION

This study confirmed the need of monitoring antimicrobial resistance in coagulase-negative staphylococci not only in the meat of slaughter animals but also in retail marine fish. The results showed that MALDI-TOF mass spectrometry is useful, accurate, and rapid method for species identification of food pathogens including Staphylococcus spp.

Clonal spread of methicillin-resistant coagulase-negative staphylococci among horses, personnel and environmental sites at equine facilities

A cross-sectional study was carried out to investigate species distribution and clonality of methicillin-resistant coagulase-negative staphylococci (MRCoNS) isolated from the nasal cavity of 39 horses and 32 veterinary or caretaker staff, and from 76 environmental surfaces at three equine facilities in Denmark. MRCoNS obtained by selective isolation were characterised by 16S rDNA sequencing, PCR detection of mecA, and pulsed-field gel electrophoresis (PFGE). MRCoNS were found in 32 (82%) horses, 20 (63%) humans and 50 (66%) environmental samples. The most common species was S. vitulinus (n=56), followed by S. sciuri (n=25), S. haemolyticus (n=14). Undistinguishable PFGE patterns were observed in MRCoNS of equine, human and environmental origin. A S. vitulinus clone and a S. haemolyticus clone were isolated from multiple horses, staff members and environmental sites within a farm and a veterinary hospital, respectively. The results indicated that methicillin-resistant strains of these two species can be shared by and possibly exchanged between horses and personnel, either directly or through contaminated environments.