Molecular characterization of high-level mupirocin resistance in methicillin-resistant staphylococci isolated from companion animals

High-level mupirocin resistance (HLMR) is determined by the plasmid-located ileS2 gene flanked by two copies of the insertion sequence 257 (IS257). The molecular epidemiology of high-level mupirocin-resistant isolates could be assessed by the determination of their IS257-ileS2 spacer regions conformation. In this study, 188 isolates of methicillin-resistant staphylococci were subjected to the detection of HLMR, and analysis of the conformation of the IS257-ileS2 spacer regions. Mupirocin resistance was detected in five (2,6%) isolates, among which two were recognized as Staphylococcus pseudintermedius, two as Staphylococcus haemolyticus, and one as Staphylococcus aureus. High-level mupirocin resistance was revealed by the agar disk diffusion method, and MIC values, and was confirmed by the detection of the ileS2 gene. The conformations of the IS257-ileS2 spacer regions were homologous in two S. haemolyticus strains tested. The remaining three isolates showed diverse IS257-ileS2 conformations. The results of this study indicate that HLMR occasionally occurs in staphylococci isolated from companion animals. The heterogeneity and the homogeneity of the IS257-ileS2 spacer regions confirm that the ileS2 gene spread among staphylococci of animal origin by the transfer of different as well as the same plasmids. Surveillance of the occurrence of mupirocin resistance and molecular characterization of resistant isolates are strongly recommended due to the possibility of plasmid-located resistance gene transfer between staphylococci.

High-level mupirocin resistance in methicillin-resistant staphylococci isolated from dogs and cats

BACKGROUND

Mupirocin is one of the few antimicrobials active against methicillin-resistant Staphylococcus aureus (MRSA), and is frequently used for the eradication of MRSA nasal colonisation in humans. Initially, mupirocin resistance was recognised in human S. aureus, including MRSA isolates, then also among coagulase-negative staphylococci (CoNS). Nowadays, mupirocin resistance is occasionally observed in canine staphylococci, along with Staphylococcus pseudintermedius (MRSP) strains, as well as CoNS, which usually show methicillin resistance. In the current study, high-level mupirocin resistance in methicillin-resistant staphylococci isolated from diseased dogs and cats was investigated.

RESULTS

Among 140 methicillin-resistant staphylococci isolates from dogs and cats, three showed high-level mupirocin resistance in a screening test using the agar disk diffusion method. One was recognised as methicillin-resistant S. aureus, one as methicillin-resistant S. pseudintermedius, and one as methicillin-resistant Staphylococcus haemolyticus. S. pseudintermedius and S. aureus were isolated from dogs, S. haemolyticus was obtained from a cat. All isolates showed high-level mupirocin resistance, confirmed by minimum inhibitory concentration (MIC) values of above 1024 μg/ml and the presence of the plasmid-located gene ileS2. This is the first report on the detection of high-level mupirocin resistance (HLMR) in S. haemolyticus of feline origin.

CONCLUSIONS

This study revealed the occurrence of HLMR in three Staphylococcus isolates obtained from companion animals in Poland. The results of this study indicate that the monitoring of mupirocin resistance in staphylococci of animal origin, especially in methicillin-resistant isolates, is strongly recommended.

Protocol changes to reduce implant-associated infection rate after tibial plateau leveling osteotomy: 703 dogs, 811 TPLO (2006-2014)

OBJECTIVE

To determine the influence of a stricter aseptic protocol on implant-associated infection (IAI) rates after tibial plateau leveling osteotomy (TPLO).

STUDY DESIGN

Retrospective cohort study.

SAMPLE POPULATION

Seven hundred three dogs (811 TPLO).

METHODS

Medical records (2006-2014) of dogs with TPLO with a ≥18-month follow-up were reviewed. An established TPLO protocol was altered to include an iodophore-impregnated adhesive drape, cefazolin administration every 90 minutes intraoperatively and then every 4 hours until hospital discharge, orthopedic surgical gloves, triclosan-coated intradermal sutures (instead of staples), soft-padded bandage with mupirocin ointment, use of single-use gloves while handling treated dogs, and placement of an Elizabethan collar. Signalment, affected limb, protocol changes, IAI, time to explant, and culture and susceptibility results were recorded. Data were analyzed by using Fisher's exact test, Wilcoxon rank-sum test, and a multivariable logistic regression model.

RESULTS

TPLO plates were removed from 31 dogs (8.5% prechange, 1.3% postchange) because of a suspected IAI. Bacterial culture results from an explanted screw were positive in 26 dogs (7.4% prechange, 0.94% postchange). The odds ratio (OR) of IAI in the postchange cohort was decreased by 88% (OR 0.12, 95% CI 0.05-0.33) compared with the prechange cohort, after controlling for variables. Staphylococcus spp. were isolated from all implants removed from IAI-positive postchange dogs, 4/5 of which were methicillin resistant. No methicillin-resistant isolates were grown from the prechange cohort implants.

CONCLUSION

The protocol tested here decreased IAI rates after TPLO, but most infections diagnosed after its implementation involved methicillin-resistant isolates.

CLINICAL SIGNIFICANCE

The protocol reported here may be used as a guide in clinics seeking to reduce their IAI rates after TPLO. Postoperative infections after implementation of this protocol should be monitored to evaluate its potential impact on the emergence of antibiotic resistance.

Antimicrobial Resistance among Staphylococci of Animal Origin

Antimicrobial resistance among staphylococci of animal origin is based on a wide variety of resistance genes. These genes mediate resistance to many classes of antimicrobial agents approved for use in animals, such as penicillins, cephalosporins, tetracyclines, macrolides, lincosamides, phenicols, aminoglycosides, aminocyclitols, pleuromutilins, and diaminopyrimidines. In addition, numerous mutations have been identified that confer resistance to specific antimicrobial agents, such as ansamycins and fluoroquinolones. The gene products of some of these resistance genes confer resistance to only specific members of a class of antimicrobial agents, whereas others confer resistance to the entire class or even to members of different classes of antimicrobial agents, including agents approved solely for human use. The resistance genes code for all three major resistance mechanisms: enzymatic inactivation, active efflux, and protection/modification/replacement of the cellular target sites of the antimicrobial agents. Mobile genetic elements, in particular plasmids and transposons, play a major role as carriers of antimicrobial resistance genes in animal staphylococci. They facilitate not only the exchange of resistance genes among members of the same and/or different staphylococcal species, but also between staphylococci and other Gram-positive bacteria. The observation that plasmids of staphylococci often harbor more than one resistance gene points toward coselection and persistence of resistance genes even without direct selective pressure by a specific antimicrobial agent. This chapter provides an overview of the resistance genes and resistance-mediating mutations known to occur in staphylococci of animal origin.

Prevalence of mupirocin resistance in Staphylococcus pseudintermedius

In the United States, veterinary use of mupirocin is primarily limited to the treatment of canine pyoderma caused by methicillin-resistant Staphylococcus pseudintermedius (MRSP). In this study, only 1 of 581 S. pseudintermedius isolates tested was resistant to mupirocin and carried the high-level mupirocin resistance gene, ileS2, on a plasmid.

Molecular characterization of high-level mupirocin resistance in Staphylococcus pseudintermedius

The genetic analysis of high-level mupirocin resistance (Hi-Mup(r)) in a Staphylococcus pseudintermedius isolate from a dog is presented. The Hi-Mup(r) ileS2 gene flanked by a novel rearrangement of directly repeated insertion sequence IS257 elements was located, together with the aminoglycoside resistance aacA-aphD determinant, on a conjugative plasmid related to the pSK41/pGO1 family plasmids.

Case-control study of Staphylococcus lugdunensis infection isolates from small companion animals

BACKGROUND

Coagulase-negative Staphylococcus lugdunensis has recently been shown to cause invasive infections of people, which are similar in pathogenic effect to those caused by Staphylococcus aureus. Little is known about the pathogenicity of S. lugdunensis in companion animals.

OBJECTIVES

To compare potential risk factors for infection, body sites affected, and whether cases and controls had been treated with antimicrobial drugs based upon susceptibility test results.

ANIMALS

Thirty-three cases of S. lugdunensis infection (25 dogs, six cats and two small mammals) were identified between January 2003 and August 2011. Two Staphylococcus pseudintermedius controls, which were identified by the microbiology laboratory immediately before and after each S. lugdunensis case, were host-species matched to each case.

METHODS

A retrospective case-control analysis.

RESULTS

During the period evaluated, the prevalence of S. lugdunensis infection was 1.3 cases per 10,000 hospital admissions for dogs and 0.95 cases per 10,000 admissions for cats (P = 0.453). In univariate analyses, S. pseudintermedius isolation was significantly associated with skin infections (P < 0.0001), while S. lugdunensis isolation was associated with the respiratory tract (P = 0.03) and other deep tissues (P = 0.005). Cases were less likely than controls to have been treated based upon susceptibility test results (P = 0.02). A conditional logistic regression analysis showed isolation of S. lugdunensis to be associated with recent (≤ 30 days) steroid administration (odds ratio, 17.72; 95% confidence interval, 2.35-132.82; P = 0.005); and in-patient status (odds ratio, 9.67; 95% confidence interval, 2.18-42.88; P = 0.003).

CONCLUSIONS

These results suggest that S. lugdunensis may cause invasive infections in companion animals, which should be treated with antimicrobials based upon susceptibility tests when available.

Prevalence of meticillin-resistant Staphylococcus pseudintermedius (MRSP) from skin and carriage sites of dogs after treatment of their meticillin-resistant or meticillin-sensitive staphylococcal pyoderma

BACKGROUND

Meticillin-resistant staphylococci are significant pathogens in veterinary dermatology, yet longitudinal studies of the impact of routine antimicrobial therapy on emergence or resolution of resistance are lacking.

OBJECTIVES

To determine the prevalence of meticillin-resistant staphylococci on skin and carriage sites in dogs with bacterial pyoderma and evaluate the prevalence of meticillin-resistant Staphylococcus pseudintermedius (MRSP) colonization after successful treatment of pyoderma.

ANIMALS

One hundred and seventy-three dogs that presented to a dermatology referral service with pyoderma and 41 healthy control dogs.

METHODS

Skin, nasal and rectal swabs for bacterial culture were collected at the time of referral and after clinical resolution of the pyoderma. Meticillin resistance was confirmed by demonstration of penicillin binding protein 2a antigen.

RESULTS

Initially, skin cultures yielded MRSP in 70 (40.5%) dogs, meticillin-resistant Staphylococcus aureus (MRSA) in three (1.7%) and meticillin-resistant Staphylococcus schleiferi ssp. coagulans (MRSScoag) in five (2.9%). Samples collected from the nose and rectum (carriage sites) yielded MRSP in 59 (34.1%) dogs, MRSA in 11 (6.4%) and MRSScoag in seven (4.0%). One hundred and two dogs were available for follow-up cultures after clinical cure. Of 42 dogs initially diagnosed with MRSP pyoderma, MRSP was isolated at follow-up from skin in 19 (45.2%) and carriage sites in 20 (47.6%). Of 60 dogs that did not have MRSP pyoderma initially, MRSP was isolated post-treatment from the skin in 17 (28.3%), and MRSP from carriage sites increased from 7.8% (initially) to 26.7% (P = 0.0022).

CONCLUSIONS AND CLINICAL IMPORTANCE

Colonization by MRSP often persists after resolution of MRSP pyoderma. Acquisition of MRSP during treatment appears to be common.

Antibiotic resistance of canine Staphylococcus intermedius group (SIG)--practical implications

A total of 221 SIG strains were isolated from clinical samples of canine origin submitted to the Diagnostic Laboratory of the Division of Bacteriology and Molecular Biology at the Warsaw University of Life Sciences in Warsaw during the period 2006-2010. The aim of the study was to investigate the frequency of prevalence of methicillin-resistant SIG strains and to determine the MIC values of cephalotin, amoxicillin/clavulanic acid, ciprofloxacin, clindamycin, gentamicin, chloramphenicol, mupirocin for a collection of randomly selected 79 strains belonging to Staphylococcus intermedius group (SIG), including 23 mecA-positive and 56 mecA-negative strains. All isolates were identified as belonging to SIG based on their phenotypic properties and PCR amplification of S. intermedius-specific fragment of the 16S rRNA gene. The mecA gene was detected in 26 (12%) of 221 SIG strains. All tested mecA-negative SIG strains were susceptible to amoxicillin/clavulanic acid and cephalotin. One of the 56 mecA-negative SIG strains was resistant to ciprofloxacin, six (11%) to gentamicin. It was found that sixteen (29%) of 56 mecA-negative SIG strains were resistant to clindamycin. Most of the mecA-positive SIG strains were resistant to ciprofloxacin (96%), clindamycin (96%), and gentamicin (96%). Only one MRSIG strain was resistant to chloramphenicol. All examined mecA-positive SIG strains were found to be susceptible to mupirocin. Our results imply that staphylococcal multidrug resistance has become more prevalent, which could lead to difficulties in effective treatment. With some resistant strains the only therapeutic possibility are antimicrobial agents important in human medicine. New regulations for veterinary medicine concerning appropriate therapy of infections caused by multidrug-resistat staphylococci are needed.