Antimicrobial Resistance and PFGE Molecular Typing of Salmonella enterica Serovar Gallinarum Isolates from Chickens in South Korea from 2013 to 2018

Antimicrobial resistance and pulsed-field gel electrophoresis (PFGE) genotypes of collected S. enterica ser. Gallinarum isolates were investigated to examine the epidemiological relationship between field outbreak isolates of S. enterica ser. Gallinarum. Thirty S. enterica ser. Gallinarum isolates collected from poultry farms with FT outbreaks from 2013 to 2018 in South Korea were analyzed. All isolates were resistant to at least 3 of the 18 antimicrobials tested and exhibited an MDR phenotype. All isolates showed resistance to streptomycin, sulfisoxazole, and colistin. One isolate was resistant to 9 antimicrobials. The antimicrobial resistance profile, streptomycin-sulfisoxazole-colistin-nalidixic acid-ciprofloxacin-gentamicin (18/30, 60.0%), was the most prevalent. PFGE types were classified into 10 groups with a 100% correlation cutoff in dendrograms for 30 field isolates. The dominant PFGE types were 1 (8/30, 26.7%), 4 (7/30, 23.3%), and 9 (5/30, 16.7%). Interestingly some isolates collected from the same and different companies had the same PFGE type. We reported a high MDR rate in S. enterica ser. Gallinarum isolates. The present study highlights the occurrence of horizontal spread and cyclic contamination of MDR S. enterica ser. Gallinarum within the same company. Furthermore, we showed cross-contamination between different companies. The characterization of these isolates would be helpful in the development of prevention and control strategies for MDR S. enterica ser. Gallinarum infection in South Korea.

Antimicrobial resistance profile of extended-spectrum beta-lactamases, adenosine-monophosphate-cyclic, and carbapenemase-producing Gram-negative bacteria isolated from domestic animals

Background and Aim: The production of beta-lactamase enzymes, such as extended-spectrum beta-lactamase (ESBL), adenosine-monophosphate-cyclic (AmpC), and Klebsiella pneumoniae carbapenemase (KPC), is one of the most important mechanisms of bacterial resistance to antimicrobials. Gram-negative bacteria show significant resistance due to various intrinsic and acquired factors. These intrinsic factors include low permeability of the outer membrane, various efflux systems, and the production of beta-lactamases, while acquired factors include chromosomal mutation and acquisition of resistance genes by horizontal transfer. Mobile elements such as plasmids, integrative conjugative elements, mobilizable islands, or transposable elements are involved in horizontal transfer. At present, the Gram-negative pathogens of most concern are Acinetobacter baumannii, Pseudomonas aeruginosa, and those belonging to the Enterobacteriaceae family (e.g., Escherichia coli, K. pneumoniae, and Proteus mirabilis). This study aimed to evaluate the profile of antimicrobial resistance and the production of the enzymes ESBL, AmpC, and KPC, in 21 gram-negative bacteria isolated from domestic animals treated at the University Veterinary Hospital (HVU) of the Federal University of Western Bahia (UFOB). Materials and Methods: The biological samples (21) were inoculated to brain heart infusion broth, blood agar, and MacConkey agar and incubated for 24-72 h at 37°C. Gram staining and identification through biochemical tests and matrix-associated laser desorption/ionization time-of-flight mass spectrometry were conducted. To evaluate the antimicrobial resistance profile, the disk diffusion method was used, and 25 antibiotics were employed. For the detection of ESBL, the disk approximation method was applied using chromogenic agar. The presence of KPC was observed using chromogenic agar and the Hodge test. For AmpC evaluation, the disk approximation method was used. Results: The most isolated agent was E. coli (66.66%, 14/21), followed by K. pneumoniae and P. mirabilis (both 14.29%, 3/21), and then Pasteurella spp. (4.76%, 1/21). The bacterial isolates showed high levels of resistance against clindamycin, penicillin, imipenem, polymyxin, cefoxitin, gentamycin, cefotaxime, ceftazidime, cephalothin, ceftriaxone, ciprofloxacin, trimethoprim/sulfamethoxazole, chloramphenicol, and tetracycline. The best effectiveness rates were observed for cefepime, streptomycin, amoxicillin-clavulanate, aztreonam, nalidixic acid, tobramycin, levofloxacin, amikacin, and meropenem. All biological isolates showed multiple resistance to at least three of the antibiotics tested (3/25), and some showed resistance to 24 of the antibiotics tested (24/25). Among the 21 pathogens analyzed, 8 were ESBL producers (38.09%); of these, 6 were identified as E. coli (28.57%), and 2 were identified as K. pneumoniae (9.52%). Two strains of K. pneumoniae produced both ESBL and KPC. None of the isolates were producers of AmpC. Conclusion: The results found in the present work raise concern about the level of antimicrobial resistance among pathogens isolated from domestic animals in Brazil. The results highlight the need for the development and implementation of anti-resistance strategies to avoid the dissemination of multiresistant pathogens, including the prudent use of antimicrobials and the implementation of bacterial culture, antimicrobial sensitivity, and phenotypic tests for the detection of beta-lactamase enzymes in bacteria isolated from animals.

Diversity and antimicrobial resistance of Salmonella enterica serovars in surface river water and sediment

This study aimed to evaluate the contamination by Salmonella sp. in the Capinzal River, to determine the prevalent serovars, patterns of antimicrobial resistance, and the genetic relationships between the serovars identified. A total of 108 samples were collected from 2016 to 2018. The isolation of Salmonella spp. was conducted according to International Organization for Standardization (ISO) standards. The antimicrobial resistance profile of the Salmonella isolates was evaluated, and isolates were selected for serotyping and verification of genetic similarity using the Pulsed-Field Gel Electrophoresis (PFGE) Technique. Of the 108 samples collected, 35 (32.4%) were positive for Salmonella; 17.2% of the isolates were from the rural area; and 88.6% were from the urban area. Salmonella was isolated from all collect points along the river, with a higher incidence at the beginning of the urban area, indicating that contamination starts in the rural area and intensifies in the urban area of the city. A percentage of 35.1% of the Salmonella isolates were resistant to at least two antibiotics, while 18.9% were considered multidrug-resistant (resistant to at least two antibiotics of different classes). Seven serovars were distinguished from the serotyped isolates, with a prevalence rate of 23.5% for S. Infantis, S. Orion, and S. Javiana; 11.8% for S. Senfterberg, and 5.9% for S. Montevideo, S. Heidelberg, and S. enterica subsp. enterica (O: 6.8). The variability in specific restriction sites generated by PFGE resulted in 10 pulsotypes, separating mainly different serotypes.

Prevalence, Risk Factors, and Antimicrobial Resistance Profile of Respiratory Pathogens Isolated From Suckling Beef Calves to Reprocessing at the Feedlot: A Longitudinal Study

Here, we investigated the prevalence and risk factors for the presence of Histophilus somni, Mannheimia haemolytica, Mycoplasma bovis, and Pasteurella multocida in the respiratory tract of calves from the spring processing to the reprocessing at feedlots. Additionally, we characterized, phenotypically and genotypically, the antimicrobial resistance (AMR) profile of the four species. Calves from 22 cow–calf operations were enrolled in the study (n = 30 calves per operation) and sampled by deep nasopharyngeal swabs at three time points: spring processing, weaning, or induction into feedlots, and at reprocessing at the feedlot. Isolates were tested for susceptibility using the minimum inhibitory concentration (MIC) test against commonly administered antimicrobials. Additionally, a subset of isolates underwent whole-genome sequencing to infer presence of AMR genes and resistance determinants. Among studied pathogens, P. multocida was the most prevalent species, regardless of time point, followed by M. haemolytica, M. bovis, and H. somni. For M. bovis, a sharp increase in prevalence was detected at the reprocessing sampling, whereas for P. multocida, an increase in prevalence was observed at the weaning/induction sampling. Comingling and co-location of feedlots were not associated with prevalence of any respiratory pathogen. In terms of AMR, resistance against macrolides was prevalent in M. bovis, with most isolates resistant against tildipirosin, tilmicosin, and tylosin. In general, there was limited evidence to support an increase in resistance rates of respiratory bacteria from the spring processing to reprocessing at feedlots, with the exception of florfenicol resistance in M. bovis, which increased at reprocessing. Metaphylactic administration of tetracyclines at feedlot induction was not associated with the MIC of tetracyclines in any respiratory bacteria. Conversely, there were clear associations between the parenteral use of macrolides as metaphylaxis at the feedlot induction, and increased MIC against macrolides in P. multocida, M. haemolytica, and H. somni. Overall, the AMR phenotypes were corroborated by presence of AMR genes. We hypothesize that the administration of macrolides such as tulathromycin at feedlot induction contributes to historical changes in macrolides MIC data of respiratory bacteria of beef cattle.

Pasteurella multocida capsular: lipopolysaccharide types D:L6 and A:L3 remain to be the main epidemic genotypes of pigs in China

Pasteurella multocida is a leading cause of respiratory disorders in pigs. This study was designed to understand the genotypical and antimicrobial resistant characteristics of P. multocida from pigs in China. To achieve this, we briefly investigated 158 P. multocida isolates from pigs with respiratory disorders in China between 2019 and 2020. Genotyping through multiplex PCR assays assigned these 158 isolates into capsular genotypes A (60.13%, 95/158), D (35.44%, 56/158), F (4.43%, 7/158), and/or lipopolysaccharide (LPS) genotypes L3 (28.48%, 45/158) and L6 (66.46%, 105/158). In addition, eight isolates (5.06%, 8/158) were found to be nontypable using the LPS genotyping method. When combining the capsular genotypes and the LPS genotypes, D: L6 (34.81%, 55/158) and A: L6 (31.65%, 50/158) were the predominant genotypes, followed by A: L3 (24.05%, 38/158). PCR detection of virulence factor-encoding genes showed that over 80% of the isolates were positive for exbB, tonB, exbD, ompH, ptfA, fimA, sodA, sodC, fur, ompA, oma87, plpB, hsf-2, nanH and hgbB, suggesting the presence of these genes were broad characteristics of P. multocida. We also found approximately 63.92% (101/158), 51.27% (81/158), 8.86% (14/158), 7.59% (12/158), 3.16% (5/158), 0.63% (1/158), and 0.63% (1/158) of the isolates grew well in media with the presence of colistin (4 μg/mL), tetracycline (16 μg/mL), tigecycline (1 μg/mL), ampicillin (32 μg/mL), chloramphenicol (32 μg/mL), cefepime (16 μg/mL), and ciprofloxacin (1 μg/mL), respectively. This study contributes to the understanding of genotypes and antimicrobial resistance profile of P. multocida currently circulation in pigs of China.