A Comparative Study on Antimicrobial Resistance in Escherichia coli Isolated from Channel Catfish and Related Freshwater Fish Species.

Antimicrobial resistance (AMR) trends in 114 generic Escherichia coli isolated from channel catfish and related fish species were investigated in this study. Of these, 45 isolates were from commercial-sized channel catfish harvested from fishponds in Alabama, while 69 isolates were from Siluriformes products, accessed from the U.S. Department of Agriculture Food Safety and Inspection Service' (FSIS) National Antimicrobial Resistance Monitoring System (NARMS) program. Antibiotic susceptibility testing and whole genome sequencing were performed using the GenomeTrakr protocol. Upon analysis, the fishpond isolates showed resistance to ampicillin (44%), meropenem (7%) and azithromycin (4%). The FSIS NARMS isolates showed resistance to tetracycline (31.9%), chloramphenicol (20.3%), sulfisoxazole (17.4%), ampicillin (5.8%) and trimethoprim-sulfamethoxazole, nalidixic acid, amoxicillin-clavulanic acid, azithromycin and cefoxitin below 5% each. There was no correlation between genotypic and phenotypic resistance in the fishpond isolates, however, there was in NARMS isolates for folate pathway antagonists: Sulfisoxazole vs. sul1 and sul2 (p = 0.0042 and p < 0.0001, respectively) and trimethoprim-sulfamethoxazole vs. dfrA16 and sul1 (p = 0.0290 and p = 0.013, respectively). Furthermore, correlations were found for tetracyclines: Tetracycline vs. tet(A) and tet(B) (p < 0.0001 each), macrolides: Azithromycin vs. mph(E) and msr(E) (p = 0.0145 each), phenicols: Chloramphenicol vs. mdtM (p < 0.0001), quinolones: Nalidixic acid vs. gyrA_S83L=POINT (p = 0.0004), and ß-lactams: Ampicillin vs. blaTEM-1 (p < 0.0001). Overall, we recorded differences in antimicrobial susceptibility testing profiles, phenotypic-genotypic concordance, and resistance to critically important antimicrobials, which may be a public health concern.

Case report: Multidrug-resistant Streptococcus pseudoporcinus isolated from an infected surgical wound of a 9-year-old spayed female Great Dane dog.

Streptococcus pseudoporcinus (S. pseudoporcinus) is a ß-hemolytic, Gram-positive novel bacterium first identified in 2006. It is a catalase-negative, non-motile coccus arranged in short chains. Furthermore, it has a broad beta-hemolytic reaction on sheep blood agar and cross-reacts with Lancefield group B antigen agglutination reagent. In this study, we report a case of S. pseudoporcinus infection of a surgical wound on the left metatarsus of a dog. The patient is a 9-year-old spayed female Great Dane dog with a brief history of multiple cutaneous masses being removed. Post-surgery, the post-surgical site on the left metatarsus became infected and discharged purulent material with a fetid odor. Upon preliminary diagnostic testing, we detected catalase-negative Gram-positive cocci exhibiting beta-hemolytic growth on sheep blood agar. A VITEK® 2 Compact machine from bioMérieux identified the bacterium as S. pseudoporcinus. Furthermore, antibiotic testing revealed multidrug resistance. Therefore, we document a multidrug-resistant S. pseudoporcinus isolate as a cause of canine post-surgical wound infection. Furthermore, it was the only isolate detected from the sample; hence, it is the cause of the infection. To our knowledge, this case is the first report of S. pseudoporcinus in a dog.