The comparative pathogenicity of four serovars of Actinobacillus (Haemophilus) pleuropneumoniae

Abstract

The pathogenicity of 2 isolates of each of serovars 7, 3, 1 and 2 of Actinobacillus pleuropneumoniae was tested by intranasal inoculation into 60, 6-week-old large white pigs. Four dose rates varying from 0.27 to 560 x 10(6) organisms per pig with 10-fold serial dilutions were used. Surviving pigs were necropsied 7 days after inoculation. The proportion of pigs dying and developing gross lesions following infection was significantly greater for pigs given serotype 1 than for each of the other 3 serotypes, which did not differ significantly from each other. Twelve of 16 pigs given either of the 2 isolates of serovar 1 died after acute illness and 1 of 44 pigs given either of the 2 isolates each of serovars 7, 3 and 2 died. Pigs given serovar 1 showed high temperatures, severe respiratory distress, frothy haemorrhagic nasal discharge and weight loss. Lung lesions were produced in all 16 pigs given serovar 1, in 7 of 14 pigs given serovar 7, 7 of 14 pigs receiving serovar 3 and in 5 of 16 pigs given serovar 2. The lethal infections were characterised by a severe acute fibrinohaemorrhagic necrotising pleuropneumonia, whereas non-lethal cases had lung lesions ranging from necrotising purulent pleuropneumonia to abscessation. Significant differences between isolates in proportions of tissues culture positive for A. pleuropneumoniae for serovars 7 and 2, but not for serovars 3 and 1 suggested that isolates may vary in virulence within serovars, but more detailed studies are needed to clarify this point.

Comparative profiling of the transcriptional response to iron restriction in six serotypes of Actinobacillus pleuropneumoniae with different virulence potential

“…Still, observations of variation in pathogenic potential, even among serotypes and strains expressing the same apx toxins, indicate that other virulence determinants must be contributing to the observed differences in pathogenesis [2,15-17]. Serotype 3 is generally believed to be less virulent than the remaining types [4,18], although some serotype 3 strains showed no difference in pathogenicity when compared to other apxII / apxIII producing serotypes [7,17]. …”

Distribution of Tetracycline Resistance Genes in Actinobacillus pleuropneumoniae Isolates from Spain

“…A cough and, in peracute cases, a frothy and bloodstained nasal discharge can also be observed. In addition, the lung lesions are characteristic in acute cases, with consolidation and raised cherry-red or black areas of necrotizing and hemorrhagic pneumonia, with interlobular edema on the diaphragmatic lobe and fibrinous pleuritis (27). The change from traditional continuous swine production to the modern "all in/all out" industry has contributed to new epidemiological situations (20).…”

Optimal regimens regimens based on PK/PD cutoff evaluation of ceftiofur against Actinobacillus pleuropneumoniae in swine

“…However, serotypes 1, 3 ,5 and 7 were the main prevalent serotypes in China [22]. Moreover, serotype 1 was more virulent than other serotypes [23,24] Therefore, A strain App BW39, Whose MIC was similar to MIC90(0.5 μg/mL) and serotype was serotype 1, was analyzed for PD study in broth and serum . According to the MIC and MBC values in vitro and ex vivo, the MBC/MIC ratio was 2 and 1, respectively.…”

“…CBP is used to de ne susceptibility and resistance. In general, the determination of CBP should take into account the ECOFF, COPD and clinical cutoff values [24,25]. Under the clinically recommended dose(5mg/kg), the ceftiofur CO PD value (2 μg/mL) against A. pleuropleumoniae was higher than the ECOFF value (0.125 μg/mL).…”