Antibiotic resistance, biofilm formation, and virulence factors of isolates of staphylococcus pseudintermedius from healthy dogs and dogs with keratitis

Abstract

Canine bacterial keratitis is a common infection that can potentially threaten vision. Staphylococcus pseudintermedius (S. pseudintermedius) is an opportunistic pathogen that has been isolated from the canine conjunctival sac but there are only a few reports on the role of this bacterium in canine keratitis. This study focused on the distribution rate of S. pseudintermedius in the canine conjunctival sac, and the antibiotic resistance, biofilm-producing ability, and dissemination of virulence factors in strains of S. pseudintermedius isolated from healthy dogs and dogs with keratitis. The study included 35 healthy dogs and 40 dogs with keratitis. Bacterial species were confirmed by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI–TOF MS). Strains of S. pseudintermedius were screened for resistance against nine different antibiotics by the Kirby–Bauer assay. The ability to produce biofilm was investigated by microtiter plate assay (MtP) and amplification of icaA and icaD genes. Virulence factors in the strains were also evaluated. A total of 132 aerobic bacteria were isolated from the 119 samples in the study. Among them, 67 bacterial strains were isolated from 70 eyes of healthy dogs, and 65 bacterial strains were isolated from 49 eyes of dogs with keratitis. The prevalence of S. pseudintermedius, which was the most frequent bacterial isolate in both the groups, was 20.9% in the healthy group and 23.08% in the keratitis group. Most of the isolates of S. pseudintermedius were sensitive to rifampin (96.6%), oxacillin (100%), and neomycin (96.6%), and resistant to tetracycline (96.6%). Virulence factors such as lip (96.6%), hlgB (96.6%), and hlgA (96.6%) were found in most of the isolates, and 89.66% of isolates were classed as biofilm producers. In conclusion, S. pseudintermedius was the common bacterium in the conjunctivital sac of the healthy dogs and dogs with keratitis in Yangzhou, China, and the presence of virulence factors and biofilm-formation ability were high in the strains isolated from the dogs with keratitis.

In Vitro Antimicrobial Activity of N-Acetylcysteine against Pathogens Most Commonly Associated with Infectious Keratitis in Dogs and Cats

“…The proposed modes of antimicrobial actions of NAC are a competitive inhibition of the uptake of amino acids, such as cysteine, by bacterial cells or the reaction of its own sulfhydryl group with the bacterial cell proteins [ 64 , 65 ]. Human, canine and feline infectious ulcerative keratitis have also been associated with the biofilm formation of different microorganisms [ 63 , 66 , 67 , 68 ]. The complex bacterial communities are encapsulated in an extracellular polymeric matrix, and hereby, they have an increased resistance to antibiotics and the host immune response, increasing bacterial survival, which further complicates the treatment of bacterial keratitis [ 69 ].…”

“…Pathogenic pheno- and genotypes have been shown to lead to the invasion of corneal cells and concurrent corneal ulcerations [ 62 ]. Wang et al also showed that the biofilm-formation ability, rates of virulence gene carriage and antibiotic resistance were higher in isolates of S. pseudintermedius from dogs with bacterial keratitis compared with those isolated from healthy dogs [ 63 ]. Studies investigating the effect of NAC on these pathogenic bacterial strains causing corneal ulcerations are lacking.…”

Impact of multi-drug resistance on clinical outcomes of dogs with corneal ulcers infected with Staphylococcus pseudintermedius

“…The virulence of Staphylococcus pseudintermedius can be explained by several factors such as enzyme secretion (e.g., coagulase, thermonuclease, and proteases), toxin secretion (e.g., exfoliative toxin, enterotoxin, and cytotoxins) ( 28 ), and biofilm formation at the infection site ( 29 ). Specific to dogs with bacterial keratitis, a recent study showed that the biofilm-formation ability and rates of virulence gene carriage and antibiotic resistance were higher in the isolates of Staphylococcus pseudintermedius from dogs with keratitis compared with those from the healthy dogs ( 30 ). In humans, the reported detrimental effects of resistant strains include higher morbidity and mortality rates ( 31 ), limited antimicrobial treatment options for physicians, prolonged hospitalization times and increased healthcare costs ( 32 , 33 ).…”

Antimicrobial activity of cell-free supernatant derived from Ligilactobacillus animalis SWLA-1 in a novel ex vivo canine corneal infection model

“…pseudintermedius (MRSP) ( 10–12 ). Furthermore, many MDRSP strains exhibit resistance to antimicrobial agents used in veterinary ophthalmology, such as fluoroquinolones and tetracyclines ( 13 , 14 ).…”