Abstract
BackgroundThis study provides biochemical and molecular genetic characteristics of P. multocida isolated from dead saigas in 1988, 2010–2015 on the territory of the Republic of Kazakhstan.ResultsBacteriological samples taken from carcasses of saiga antelope during mortality events recorded in West Kazakhstan in both 2010 and 2011 and in Kostanay in 2012 and 2015 confirmed the presence of P. multocida, according to morphological and biochemical characterisation. Only in the event of 2015 was the agent proven to be the causative agent of the disease observed, haemorrhagic septicaemia. In the other mortality events it is not certain if the organism was a primary aetiology or an incidental finding as confirmatory pathological investigation was not undertaken. The implemented phylogenetic analysis of ribosomal RNA 16S gene allowed us to identify Pasteurella strains isolated in 2010–2015 as P. multocida subspecies multocida. Capsular typing by PCR showed that the studied strains isolated from dead saiga in 2010, 2011, 2012 and 2015 belonged to serotype B. MLST analysis showed that these strains of P. multocida are of the capsule type B and form one clonal grouping with isolates ST64, ST44, ST45, ST46, ST44, ST47 which isolated from cases of hemorrhagic septicemia of animals in Hungary, Burma, Sri Lanka, Pakistan and Spain. Sixteen virulence genes of the five strains of P. multocida, isolated from saigas were studied using multiplex PCR. ptfA, ompA, ompH, oma87, plpB, fimA, hsf-2, pfhA, exbB, tonB, hgbA, fur, nanB, nanH and pmHAS genes were detected in all strains. The toxA gene was not identified in the studied strains. The phylogenies of these isolates is compared across saiga populations and years and the 2015 isolate was compared to that of an isolate from a disease outbreak in 1988 and the findings suggest that these isolated bacteria are stable commensals, opportunistically pathogenic, being phylogenetically uniform with very little genetic variation notable over the last 4 decades.ConclusionIsolation, phenotypic and genetic characterization of the P. multocida isolates inform understanding of the epidemiology of infection in saigas and predict virulent potential of these opportunistic bacteria.
Highlights
This study provides biochemical and molecular genetic characteristics of P. multocida isolated from dead saigas in 1988, 2010–2015 on the territory of the Republic of Kazakhstan
Cases of mass mortality of the saiga antelope were ascribed to pasteurellosis in Kazakhstan in 1981, 1984 and 1988 but extensive pathological diagnosis was not completed and it was not confirmed if these were due to Haemorrhagic septicaemia (HS), pneumonic pasteurellosis or involved other disease agents [11]
Given the important characteristics of pfhA and ptfA genes, the authors recommend them as a marker for the epidemiological characterization of field strains and isolates of P. multocida. This is the first complete description of the phenotypic and genetic characteristics of P. multocida strains isolated from saigas associated with opportunistic isolation, sporadic cases of disease and peracute mass mortality events
Summary
This study provides biochemical and molecular genetic characteristics of P. multocida isolated from dead saigas in 1988, 2010–2015 on the territory of the Republic of Kazakhstan. Cases of mass mortality of the saiga antelope were ascribed to pasteurellosis in Kazakhstan in 1981, 1984 and 1988 but extensive pathological diagnosis was not completed and it was not confirmed if these were due to HS, pneumonic pasteurellosis or involved other disease agents [11]. Significant co-infections were not found and a wide range of known virulent agents excluded whilst the epidemiology and environmental investigations suggested opportunistic infection from latent bacteria triggered by unusually humid and warm weather conditions prior to the mass mortality. These findings were consistent with earlier observations and retrospective modelling for the years 1981 and 1988 in addition to 2015 [18]
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