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Published on: January 2, 2017

Atypical multidrug-resistant serotype 1 Actinobacillus pleuropneumoniae with ApxIII in China

Chuchu Duan1,2, Zhihong Fang2, Zecheng Lin2

  • 1College of Animal Science, Fujian Agriculture and Forestry University, Fuzhou, Fujian, China.

Frontiers in Veterinary Science
|July 28, 2026
PubMed

Insights

A novel Actinobacillus pleuropneumoniae (APP) strain, serotype 1, was identified following a severe pig respiratory disease outbreak. This strain exhibits an unusual toxin gene profile and multidrug resistance, impacting swine health.

Area of Science:

  • Veterinary Microbiology
  • Animal Pathology
  • Epidemiology

Background:

  • Actinobacillus pleuropneumoniae (APP) causes significant economic losses in the swine industry due to porcine contagious pleuropneumonia.
  • An acute respiratory disease outbreak in Fujian Province, China, resulted in high morbidity (30%) and mortality (56%) in pigs.

Purpose of the Study:

  • To isolate and identify the causative agent of the pig respiratory disease outbreak.
  • To characterize the biological properties, including toxin gene profile and antimicrobial resistance, of the isolated pathogen.

Main Methods:

  • Isolation and identification of the etiological agent from deceased pigs' lung tissues.
  • Morphological, biochemical, and serotype-specific PCR analyses for pathogen identification.
  • Toxin gene profiling (Apx toxins), antimicrobial susceptibility testing, and pathogenicity assessment in mice (LD50 determination).

Main Results:

  • An NAD-dependent bacterial strain, identified as APP serotype 1 (isolate APPFJLYC01), was isolated.
  • APPFJLYC01 possessed an atypical toxin gene profile (ApxII, ApxIII, ApxIV, lacking ApxI), differing from typical serotype 1 strains.
  • The isolate displayed multidrug resistance to several antibiotics and was confirmed virulent in mice (LD50 = 7.91 × 10^8 CFU/mL).

Conclusions:

  • A multidrug-resistant APP serotype 1 strain with an atypical toxin gene profile was identified in Fujian Province, China.
  • Findings highlight genetic diversity and antimicrobial resistance in local APP populations.
  • Data supports the development of targeted prevention and control strategies for porcine pleuropneumonia.
Keywords:
Actinobacillus pleuropneumoniaeApxIIIatypicaldrug resistancepathogenicity

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