# Characterization of Multidrug-Resistant Trueperella (Arcanobacterium) pyogenes Isolates from Vertebral Osteomyelitis in Slaughtered Pigs

## TL;DR

This study found multidrug-resistant Trueperella pyogenes in pig carcasses, highlighting the importance of slaughterhouse monitoring for animal and public health.

## Contribution

The study provides new insights into the antibiotic resistance and virulence of T. pyogenes isolated from pig spinal abscesses.

## Key findings

- Eleven T. pyogenes isolates showed multidrug resistance to 8–14 antimicrobial agents.
- Complete resistance was observed against amikacin, nalidixic acid, and other key antibiotics.
- The study emphasizes the role of slaughterhouses in tracking antimicrobial resistance and emerging pathogens.

## Abstract

Slaughterhouses offer a valuable opportunity to detect hidden animal diseases that may not be observed during life. In this study, we examined fully condemned pig carcasses with spinal abscesses and identified Trueperella pyogenes as a key pathogen. By analyzing samples collected postmortem, we uncovered high levels of antibiotic resistance and evidence of potential virulence, providing critical insights into both animal health and food safety. This research demonstrates how slaughterhouse monitoring can support the early detection of emerging pathogens, track antimicrobial resistance, and guide farm-level interventions. It highlights the epidemiological value of routine meat inspection data for improving animal production systems and protecting public health.

Slaughterhouses serve as critical surveillance hubs for identifying subclinical and economically important diseases in food-producing animals. Trueperella (Arcanobacterium) pyogenes, an opportunistic pathogen commonly found on the mucous membranes of livestock, is associated with mastitis, abortion, and suppurative infections such as abscesses. In this study, we investigated 30 pig carcasses fully condemned due to vertebral osteomyelitis (VO) at two slaughterhouses in Gwangju, Republic of Korea, between November 2023 and May 2024. From abscess lesions, 11 T. pyogenes strains were isolated and characterized morphologically, biochemically, and genetically. The hemolytic exotoxin pyolysin (plo gene), a major virulence factor, was detected in five isolates (45.46%). Phylogenetic analysis of partial 16S rDNA sequences confirmed close clustering with known T. pyogenes reference strains. All 11 isolates exhibited multidrug resistance, showing resistance to 8–14 antimicrobial agents per strain. Complete resistance (11/11, 100%) was observed against amikacin (AMI), nalidixic acid (NAL), chloramphenicol (CHL), florfenicol (FFN), and trimethoprim/sulfamethoxazole (SXT). High resistance rates were also detected for erythromycin (ERY) and clindamycin (CLI) (10/11, 90.9%), ceftazidime (TAZ), ceftriaxone (AXO), ciprofloxacin (CIP) (7/11, 63.6%), and tetracycline (TET) and streptomycin (STR) (5/11, 45.5%), while gentamicin (GEN) resistance was found in three isolates (27.3%). In contrast, none of the isolates showed resistance to ampicillin, cefoxitin, or cefotaxime. These findings underscore the epidemiological value of abattoir-based monitoring in detecting emerging pathogens and tracking antimicrobial resistance. The results provide important baseline data to inform disease control strategies, guide antimicrobial stewardship, and support One Health approaches, including the development of preventive measures such as vaccines.