Dynamics and chronology of Mycoplasma hyopneumoniae strain 232 infection in experimentally inoculated swine

Abstract

Direct detection of Mycoplasma hyopneumoniae through molecular tools is a growing trend for early diagnosis, highlighting the importance of knowing M. hyopneumoniae dynamics in the respiratory tract upon infection. This study focused on monitoring the infection level and its effects in different anatomic sites of the respiratory tract of experimentally infected swine in four time-points post-infection. To this end, 24 pigs were allocated to either non-inoculated group (n = 8) or inoculated group (n = 16). On day 0 post-infection (dpi), animals of the inoculated group were intratracheally inoculated with M. hyopneumoniae. Nasal swabs were collected weekly for qPCR detection of bacterial shedding. At 14, 28, 42, and 56 dpi, four animals from the inoculated group and two from the control group were necropsied. Bronchoalveolar lavage fluid (BALF) and samples from three different anatomical tracheal sections (cranial - CT, medium - MT, lower - LT) were collected for qPCR and histopathology. Bacterial loads (qPCR) in tracheal samples were: 4.47 × 102 copies∕μL (CT), 1.5 × 104- copies∕ μL (MT) and 1.4 × 104 copies∕μL (LT samples). M. hyopneumoniae quantification in BALF showed the highest load at 28 dpi (2.0 × 106 copies∕ μL). Microscopic lesions in LT samples presented the highest scores at 56 dpi and were significantly correlated with the pathogen load on 14 dpi (0.93) and 28 dpi (0.75). The greatest bacterial load of M. hyopneumoniae in CT samples and BALF was registered at 28 dpi, and it remained high in BALF and LT throughout the 56 dpi. The pathogen was able to persist during the whole experimental period, however higher estimated quantification values were registered in the lower parts of the respiratory tract, especially at 56 dpi. These findings are important for improving diagnostics, treatment, and control measures of M. hyopneumoniae infection in swine herds.

Association between Enzootic Pneumonia-like Lung Lesions and Carcass Quality and Meat pH Value in Slaughter Pigs

“…Compared with other entries in the literature, a histopathological examination revealed similar microscopic changes in all samples such as epithelium hyperplasia, cilia density reduction, peribronchiolar and perivascular lymphohistiocytic infiltration, and cuffing formation [ 42 ]. In some papers, the microscopic scoring was provided together with macroscopic lung scoring to quantitatively assess the effects of changes in experimentally inoculated swine [ 43 , 44 , 45 , 46 ] but in field samples, as long as changes are observed, this approach may be less applicable.…”

The role of co-infections in M. hyopneumoniae outbreaks among heavy fattening pigs: a field study

“…On the contrary to the infection status, the M. hyopneumoniae load varied in time but with a different pattern depending on the group. The highest PCR number of copies was detected at T0 in Groups A and B and at T1 in Group C. Because the highest burden of M. hyopneumoniae has been proven to occur at 28 days post-infection [ 30 ], it can be assumed that the early stages of the EP outbreaks occurred at T0 in Groups A and B and at T1 in Group C. Considering the higher sensitivity of real-time PCR on TBS samples collected in the early stage of the outbreak [ 31 ], these findings suggest that sampling of pigs with clinical signs may lead to a more effective and timely diagnosis of EP outbreaks.…”