Investigation of In Vitro Susceptibility and Resistance Mechanisms in Skin Pathogens: Perspectives for Fluoroquinolone Therapy in Canine Pyoderma

Abstract

Fluoroquinolones (FQ) are commonly used in dogs with bacterial skin infections. Their use as first choice, along with the increased incidence of FQ-resistance, represents a risk to animal and public health. Our study determined minimum inhibitory (MIC) and bactericidal (MBC) concentrations of five FQs in Staphylococcus aureus, Staphylococcus pseudintermedius, and Escherichia coli, together with FQ-resistance mechanisms. MICs, efflux pump (EP) overexpression and MBCs were measured in 249 skin infection isolates following CLSI guidelines (CLSI VET01-A4, CLSI M26-A). Chromosomal and plasmid-mediated resistance genes were investigated after DNA extraction and sequencing. FQ-resistance was detected in 10% of methicillin-susceptible (MS), 90% of methicillin-resistant (MR) staphylococci and in 36% of E. coli. Bactericidal effect was observed except in 50% of MRSA/P for ciprofloxacin and in 20% of MRSPs for enrofloxacin. Highest MICs were associated with double mutation in gyrA (Ser83Leu + Asp87Asn), efflux pumps and three PMQR genes in E. coli, and grlA (Ser80Phe + Glu84Lys) in S. aureus. EP overexpression was high among E. coli (96%), low in S. aureus (1%) and absent in S. pseudintermedius. Pradofloxacin and moxifloxacin showed low MICs with bactericidal effect. Since in vitro FQ resistance was associated with MR, FQ use should be prudently guided by susceptibility testing.

Exploring Efflux as a Mechanism of Reduced Susceptibility towards Biocides and Fluoroquinolones in Staphylococcus pseudintermedius

“…These data suggest that fluoroquinolone resistance in S. pseudintermedius is mainly due to target mutations of QRDR region of grlA / gyrA as described by Loiacono and colleagues [ 61 ]. The QRDR mutations herein reported have been already associated with fluoroquinolone resistance in S. pseudintermedius [ 43 , 44 , 62 , 63 ], and are known to convey high MIC CIP values, similar to the ones found in this work [ 41 , 63 , 64 ]. This fact prevented the assessment of a potential effect of EIs upon MIC CIP values.…”

“…The EIs TZ and VER revealed a mild effect upon MIC CIP values for the TPP NWT strains, resulting mostly in two-fold MIC reductions ( Table 2 ). However, the EIs effect may be masked by the presence of the double mutation S80I (GrlA)/S84L (GyrA) carried by most of these strains, which are often associated with MIC CIP > 32 mg/L [ 43 , 44 ]. The same mild effect of EIs was observed for most TPP WT strains, with only four strains showing a 4-fold MIC CIP reduction.…”

“…The misuse of fluoroquinolones has promoted an increase of antimicrobial resistance in Portugal and worldwide [ 12 , 50 , 59 , 60 ]. In S. pseudintermedius , resistance mechanisms against fluoroquinolones include increased efflux activity and/or mutations in QRDR of the target genes, grlA and gyrA [ 41 , 44 ]. A previous characterization of the collection in study had revealed a significant rate (~25%) of fluoroquinolone resistance and presence of target gene mutations.…”

Antimicrobial Resistance and Treatment in Companion, Food and Exotic Animals

“…Furthermore, research was focused on investigating the incidence and molecular characterization of extended-spectrum β-lactamase producing Enterobacterales (ESBL-PE) in dogs [ 10 ], with the findings that healthy dogs may be colonized with ESBL-PE multidrug-resistant (MDR) strains, as well as humans, which may serve as a possible source for AMR. Additionally, contemporary perspectives for fluoroquinolone therapy in canine pyoderma and predisposition and resistance mechanisms in skin pathogens were investigated [ 11 ], with findings of fluoroquinolone resistance associated with methicillin-resistant staphylococci. Therefore, Azzariti et al [ 11 ] recommended that fluoroquinolone use should be prudently guided by susceptibility testing.…”

“…Additionally, contemporary perspectives for fluoroquinolone therapy in canine pyoderma and predisposition and resistance mechanisms in skin pathogens were investigated [ 11 ], with findings of fluoroquinolone resistance associated with methicillin-resistant staphylococci. Therefore, Azzariti et al [ 11 ] recommended that fluoroquinolone use should be prudently guided by susceptibility testing. Debergh et al [ 12 ] have reported the very first finding of MDR Klebsiella pneumoniae of sequence type 11 carrying bla SCO-1 and bla DHA-1 isolated from a four-month-old dog in Belgium.…”