S. pseudintermedius and S. aureus lineages with transmission ability circulate as causative agents of infections in pets for years

Abstract

Background: Staphylococcus pseudintermedius (SP) and Staphylococcus aureus (SA) are common colonizers of companion animals, but they are also considered opportunistic pathogens, causing diseases of diverse severity. This study focused on the identification and characterization of 33 coagulase-positive staphylococci isolated from diseased pets (28 dogs and five cats) during 2009-2011 in a veterinary hospital in Spain in order to stablish the circulating lineages and their antimicrobial resistance profile.

Results: Twenty-eight isolates were identified as SP and five as SA. Nine methicillin-resistant (MR) isolates (27%) carrying the mecA gene were detected (eight MRSP and one MRSA). The 55% of SP and SA isolates were multidrug-resistant (MDR). MRSP strains were typed as ST71-agrIII-SCCmecII/III-(PFGE) A (n=5), ST68-agrIV-SCCmecV-B1/B2 (n=2), and ST258-agrII-SCCmecIV-C (n=1). SP isolates showed resistance to the following antimicrobials [percentage of resistant isolates/resistance genes]: penicillin [82/blaZ], oxacillin [29/mecA] erythromycin/clindamycin [43/erm(B)], aminoglycosides [18-46/aacA-aphD, aphA3, aadE], tetracycline [71/tet(M), tet(K)], ciprofloxacin [29], chloramphenicol [29/cat_pC221], and trimethoprim-sulfamethoxazole [50/dfrG, dfrK]. The dfrK gene was revealed as part of the radC-integrated Tn559 in two SP isolates. Virulence genes detected among SP isolates were as follow [percentage of isolates]: siet [100], se-int [100], lukS/F-I [100], sec_canine [7], and expB [7]. The single MRSA-mecA detected was typed as t011-ST398/CC398-agrI-SCCmecV and was MDR. The methicillin-susceptible SA isolates were typed as t045-ST5/CC5 (n=2), t10576-ST1660 (n=1), and t005-ST22/CC22 (n=1); the t005-ST22 feline isolate was PVL-positive and the two t045-ST45 isolates were ascribed to Immune Evasion Cluster (IEC) type F. Moreover, the t10576-ST1660 isolate, of potential equine origin, harbored the lukPQ and scneq genes. According to animal clinical history and data records, several strains seem to have been acquired from different sources of the hospital environment, while some SA strains appeared to have a human origin.

Conclusions: The frequent detection of MR and MDR isolates among clinical SP and SA strains with noticeable virulence traits is of veterinary concern, implying limited treatment options available. This is the first description of MRSA-ST398 and MRSP-ST68 in pets in Spain, as well the first report of the dfrK-carrying Tn559 in SP. This evidences that current transmissible lineages with mobilizable resistomes have been circulating as causative agents of infections among pets for years.

Keywords: Infection; MRSA; MRSA-CC398; MRSP; MRSP-ST71; Pets; Tn559.

Fig. 1

Antimicrobial resistance rate of MSSP and MRSP investigated in this study. PEN, penicillin; ERY, erythromycin; CLI, clindamycin; GEN, gentamicin; TOB, tobramycin; KAN, kanamycin; STR, streptomycin; TET, tetracycline; CIP, ciprofloxacin; CHL, chloramphenicol; SXT, trimethoprim-sulfamethoxazole. The p-value (Fisher’s Exact test) is shown below the figure. Asterisks indicate the antimicrobial agents for which statistical differences were found between the antimicrobial resistance rates of MSSP and MRSP (P < 0.05)

Fig. 2

a Graphical representation of the Tn559 structure containing the dfrK gene integrated in the chromosomal radC gene of the isolate Staphylococcus pseudintermedius C5347 (GenBank accession number MT252966) and nucleotide substitutions detected in the non-coding region downstream the dfrK gene compared to Staphylococcus aureus transposon Tn559 (GenBank accession number FN677369). The nucleotide positions are set based on the whole Tn559. Nucleotide insertions and substitutions are colored in yellow. b Amino acid sequence alignment of radC gene and resultant RadC of Staphylococcus pseudintermedius strain C2719 (GenBank accession number HF679552), where transposon Tn558 was integrated, that of S. pseudintermedius C5347 (GenBank accession number MT252966). The position of the primer pair employed is indicated in grey. Nucleotide substitutions are colored in yellow and amino acid substitutions in blue