Variation in the Antimicrobial Susceptibility ofActinobacillus pleuropneumoniaeIsolates in a Pig, Within a Batch of Pigs, and Among Batches of Pigs from One Farm

Abstract

Antimicrobial resistance in bacterial porcine respiratory pathogens has been shown to exist in many countries. However, little is known about the variability in antimicrobial susceptibility within a population of a single bacterial respiratory pathogen on a pig farm. This study examined the antimicrobial susceptibility of Actinobacillus pleuropneumoniae using multiple isolates within a pig and across the pigs in three different slaughter batches. Initially, the isolates from the three batches were identified, serotyped, and subsample genotyped. All the 367 isolates were identified as A. pleuropneumoniae serovar 1, and only a single genetic profile was detected in the 74 examined isolates. The susceptibility of the 367 isolates of A. pleuropneumoniae to ampicillin, tetracycline and tilmicosin was determined by a disc diffusion technique. For tilmicosin, the three batches were found to consist of a mix of susceptible and resistant isolates. The zone diameters of the three antimicrobials varied considerably among isolates in the second sampling. In addition, the second sampling provided statistically significant evidence of bimodal populations in terms of zone diameters for both tilmicosin and ampicillin. The results support the hypothesis that the antimicrobial susceptibility of one population of a porcine respiratory pathogen can vary within a batch of pigs on a farm.

Update onActinobacillus pleuropneumoniae-knowledge, gaps and challenges

“…It has been demonstrated that whole‐genome sequencing can be used as predictor for App resistance to antimicrobial substances (Bossé, Li, Rogers, et al., ). In general, variation in levels of antimicrobial resistance of App isolates within the same herd can be high (Dayao et al., ), and there is not always an association between in vitro test results and success after treatment of disease.…”

Galactose-1-phosphate uridyltransferase (GalT), an in vivo-induced antigen of Actinobacillus pleuropneumoniae serovar 5b strain L20, provided immunoprotection against serovar 1 strain MS71

“…Antibacterial agents have been viewed as the first choice to treat the diseases caused by bacteria. However, the reported abuse and overuse of antibacterial agents is selecting for an ever-growing population of resistant pathogens, including APP [41][42][43][44]. The use of vaccines has proven to be a better choice in efforts to control PCP outbreaks.…”

Antimicrobial susceptibility of Actinobacillus pleuropneumoniae strains isolated from pig's clinical samples in Serbia

“…For example, in Canada five isolates demonstrated multidrug resistance to penicillins, streptomycin, tetracyclines and sulfanomides, whereas three others showed multiresistance to streptomycin, sulfonamides and tetracyclines (17). In many countries different levels resistance of A. pleuropneumoniae (10,14,25,30) have been determined. Bacterial pathogens that cause diseases in pigs including A. pleuropneumoniae often demonstrate resistance to drugs commonly used in veterinary practice.…”

“…A broad range of antimicrobial agents used for the treatment of disease including β-lactams (penicillin, amoxicillin, ampicillin, and ceftiofur), fluoroquinolones, gentamicin, trimethoprim/sulfamethoxazole, tiamulin, lincomycin/spectinomycin, and tetracyclines (25,30). Isolates of A. pleuropneumoniae are generally reported to be susceptible toward fluoroquinolones, ceftiofur and florfenicol, but various antimicrobial resistance patterns have been observed to others antimicrobials in different countries (10,32).…”