Comparison of methicillin-resistant Staphylococcus pseudintermedius adherence to 2 canine limb salvage endoprosthesis implants.

The objective of our study was to compare adhesion of methicillin-resistant Staphylococcus pseudintermedius (MRSP) to stainless steel (SS) and to tantalum (TA) canine limb salvage endoprosthesis implants in an in vitro experimental study. The median of the mean log10 colony forming units/mL for adherent MRSP was 4.96 (range: 4.63 to 6.33) for the TA endoprosthesis and 4.31 (range: 3.86 to 5.05) for the SS endoprosthesis (P = 0.009). Although the trabecular and porous design of the TA endoprosthesis provides mechanical benefits over the SS endoprosthesis, it may increase the risk of developing infection due to higher levels of bacterial adherence.

Comparaison de l'adhérence deStaphylococcus pseudintermediusrésistant à la méthicilline à deux implants d'endoprothèse pour sauver des membres canins. L'objectif de notre étude consistait à comparer l'adhésion de Staphylococcus pseudintermedius résistant à la méthicilline (MRSP) à des implants d'endoprothèse en acier inoxydable (AI) et en tantale (TA) pour sauver des membres canins lors d'une étude expérimentale in vitro. La médiane des moyennes en log10 des unités formatrices de colonies/mL pour le MRSP adhérent était de 4,96 (écart : de 4,63 à 6,33) pour l'endoprothèse TA et 4,31 (écart : de 3,86 à 5,05) pour l'endoprothèse d'AI (P = 0,009). Même si la conception trabéculaire et poreuse de l'endoprothèse de TA offre des avantages mécaniques par rapport à l'endoprothèse d'AI, elle peut accroître le risque de développer une infection en raison des taux supérieurs d'adhérence bactérienne.(Traduit par Isabelle Vallières).

Evaluation of the Impact of Methicillin-Resistant Staphylococcus pseudintermedius Biofilm Formation on Antimicrobial Susceptibility.

OBJECTIVE: To compare the minimum inhibitory concentration (MIC) of four antimicrobials in planktonic vs. biofilm-associated Staphylococcus pseudintermedius. STUDY DESIGN: In vitro study. SAMPLE POPULATION: 78 isolates from dogs colonized or infected with methicillin-resistant S. pseudintermedius (MRSP, n=39) or methicillin-susceptible S. pseudintermedius (MSSP, n=39). METHODS: Agar dilution was used to determine the MIC of amikacin, cefazolin, enrofloxacin, and gentamicin for planktonic bacteria. A modified broth microdilution assay was used to assess the MIC of biofilm-associated bacteria. RESULTS: MIC were significantly higher in biofilm-associated vs. planktonic bacteria for all antimicrobials; amikacin (median MIC: biofilm >2,000 µg/mL vs. planktonic 3 µg/mL, P<.0001), cefazolin (>1,000 vs. 0.5 µg/mL, P<.0001), enrofloxacin (>1,000 vs. 0.25 µg/mL, P<.0001), and gentamicin (>1,000 vs. 0.3 µg/mL, P<.001). For all antimicrobials, there were significant differences in planktonic MIC for MRSP and MSSP (all P<.0001) but no differences between biofilm MIC for MRSP and MSSP (P=.08-1.0). CONCLUSION: The MIC for biofilm-associated S. pseudintermedius are significantly higher than for planktonic bacteria. Standard methods for determining MIC are not appropriate for biofilm-associated infections. This must be considered when determining treatment regimens for infections that potentially involve biofilms, and further study of methods to control biofilm-associated infections is needed.

Association between methicillin-resistant Staphylococcus pseudintermedius carriage and the development of surgical site infections following tibial plateau leveling osteotomy in dogs.

OBJECTIVE: To evaluate the association between preoperative carriage of methicillin-resistant Staphylococcus pseudintermedius (MRSP) and the development of surgical site infections (SSIs) following tibial plateau leveling osteotomy (TPLO) in dogs. DESIGN: Prospective multicenter study. ANIMALS: 549 dogs. PROCEDURES: At 7 veterinary hospitals, swab specimens were obtained from the pharynx, nares, rectum, and skin of dogs admitted for TPLO. Specimens were submitted for culture of MRSP. For each dog, information regarding preoperative and postoperative antimicrobial administration, comorbidities, contact with other dogs, and whether the dog developed an SSI was obtained. Univariable and multivariable analyses were performed to identify variables associated with preoperative and postoperative MRSP colonization and the development of an SSI. RESULTS: Of the 549 study dogs, 24 (4.4%) were identified as MRSP carriers before TPLO and 37 (6.7%) developed an SSI after TPLO. Bacteriologic culture was performed on specimens obtained from 32 of the 37 SSIs, and MRSP was isolated from 11 (34%). Carriers of MRSP (OR, 6.72; 95% confidence interval [CI], 2.12 to 21.4) and Bulldogs (OR, 11.1; 95% CI, 2.07 to 59.3) were at risk for development of an SSI after TPLO, whereas postoperative administration of antimicrobials (OR, 0.36; 95% CI, 0.15 to 0.91) appeared to protect against development of an SSI. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that carriage of MRSP were a risk factor for development of an SSI after TPLO and measures to rapidly identify and treat MRSP carriers are warranted. Postoperative administration of antimicrobials protected against development of an SSI after TPLO.

Impact of polymethylmethacrylate additives on methicillin-resistant Staphylococcus pseudintermedius biofilm formation in vitro.

OBJECTIVE: To evaluate the impact of gentamicin, silver, or both additives in polymethylmethacrylate (PMMA) beads on methicillin-resistant Staphylococcus pseudintermedius (MRSP) biofilm formation in vitro. SAMPLE: 4 preparations of PMMA beads (formed with no additive [control], gentamicin, silver, and gentamicin and silver). PROCEDURES: Beads from each group were exposed to 10 MRSP isolates known to be strong biofilm formers. Following incubation, the beads were rinsed to remove planktonic bacteria, then sonicated to dislodge biofilm-associated bacteria. Resulting suspensions were serially diluted, plated on blood agar, and incubated overnight; CFUs were counted. Variance of mean CFU counts following log10 transformation was analyzed among PMMA groups. RESULTS: None of the PMMA additives tested completely inhibited MRSP biofilm formation. There was a significant effect of gentamicin and gentamicin plus silver on this variable, compared with controls, but not of silver alone. There was no difference between gentamicin and gentamicin plus silver. When only isolates not susceptible to gentamicin were evaluated, there were no significant differences among PMMA additive groups. Within gentamicin-susceptible isolates, there was an impact of gentamicin and gentamicin plus silver, but no impact of silver alone and no difference between gentamicin and gentamicin plus silver. CONCLUSIONS AND CLINICAL RELEVANCE: Gentamicin-impregnated PMMA was effective at reducing biofilm formation of gentamicin-susceptible MRSP isolates but had no effect on isolates not susceptible to gentamicin. Silver-impregnated PMMA had no effect on MRSP biofilm formation. Results suggested that gentamicin-impregnated PMMA may not be effective in vivo against MRSP isolates not susceptible to gentamicin. Antibacterial efficacy of silver should not be assumed without proper testing of the target bacteria and specific silver compound.

Perioperative administration of antimicrobials during tibial plateau leveling osteotomy.

OBJECTIVE: To evaluate perioperative antimicrobial administration during tibial plateau leveling osteotomy (TPLO) in dogs at the Ontario Veterinary College Health Sciences Centre. STUDY DESIGN: Retrospective case series. ANIMALS: Dogs (n = 184) that had TPLO (n = 226). METHODS: Medical records were reviewed and data collected included timing and dosage of pre, intra, and postoperative antimicrobial administration, method of stifle inspection, duration of surgery, duration of anesthesia, development of surgical site infection (SSI), microbiological investigation, implant removal, and possible comorbidities. Univariable analysis was conducted, followed by stepwise forward logistic regression to determine factors associated with SSI. RESULTS: Of the 225 cases administered perioperative antimicrobials, 96 (42.5%) received appropriate perioperative antimicrobial prophylaxis based on target times for preoperative and intraoperative dosing. Postoperative antimicrobials were administered to 54 (23.9%) of cases. Surgical site infection was documented in 30 (13.3%) cases. Staphylococcus pseudintermedius was isolated from 15/17 (88.2%) SSI from which a bacterium was isolated, with 6/15 (40%) being methicillin-resistant Staphylococcus pseudintermedius (MRSP). Postoperative administration of antimicrobials was protective for SSI (OR 0.1367; P = .0001; 95% CI = 0.021, 0.50). Duration of anesthesia time was associated with the likelihood of development of SSI (OR = 1.0094; P = .001; 95% CI = 1.00, 1.02). CONCLUSION: Current practices for administration of antimicrobial prophylaxis during TPLO can be improved. There was no association between timing of antibiotic administration that was inconsistent with the target and development of SSI. Further study into risk factors of TPLO SSI is required.

Investigation of incidence and risk factors for surgical glove perforation in small animal surgery.

OBJECTIVE: To identify incidence and risk factors for surgical glove perforation in small animal surgery. STUDY DESIGN: Observational cohort study. SAMPLE POPULATION: Surgical gloves (n = 2132) worn in 363 surgical procedures. METHODS: All gloves worn by operative personnel were assessed for perforation at end-procedure using a water leak test. Putative risk factors were recorded by a surgical team member. Associations between risk factors and perforation were assessed using multivariable multi-level random-effects logistic regression models to control for hierarchical data structure. RESULTS: At least 1 glove perforation occurred in 26.2% of procedures. Identified risk factors for glove perforation included increased surgical duration (surgery >1 hour OR = 1.79, 95% CI = 1.12-2.86), performing orthopedic procedures (OR = 1.88; 95% CI = 1.23-2.88), any procedure using powered instruments (OR = 1.93; 95% CI = 1.21-3.09) or surgical wire (OR = 3.02; 95% CI = 1.50-6.05), use of polyisoprene as a glove material (OR = 1.59, 95% CI = 1.05-2.39), and operative role as primary surgeon (OR = 2.01; 95% CI = 1.35-2.98). The ability of the wearer to detect perforations intraoperatively was poor, with a sensitivity of 30.8%. CONCLUSIONS: There is a high incidence of unrecognized glove perforations in small animal surgery.

Chronic liver lobe torsion in a cat.

A 13 yr old castrated male blue British shorthair with a 3 mo history of vomiting was diagnosed with a left lateral liver lobe mass following abdominal ultrasonography. At the time of celiotomy, liver lobe torsion (LLT) of the left lateral lobe was also present. Histopathologic evaluation of the liver mass and associated lobe revealed extensive necrosis secondary to chronic torsion. This is the second reported case of LLT in a cat. Both cases were associated with liver masses. The cat presented in this case remained clinically normal 8 mo postoperatively following lobectomy of the affected lobe.