The aim of this study was to assess the frequency and association of virulence factors of Escherichia (E.) coli isolated from weaned piglets with diarrhea and to correlate it with fecal consistency. A total of 152 rectal swabs were collected from 25-40 day-old piglets with diarrhea, in farms of Southern Brazil. Phenotypical and molecular techniques were used for bacterial isolation, characterization and classification of enterotoxigenic E. coli (ETEC) pathotypes. Statistical analysis was carried out to determine the frequency of virulence factors and virotypes, of fimbriae F4, F5, F6, F18, F41 and toxins LT, STa, STb and STx2e. Out of 456 E. coli isolates, 287 (62.9%) samples showed significant growth of E. coli. Among them, 194 (67.6%) samples showed at least one virulence factor, indicating that ETEC is an important etiological agent of diarrhea in weaned piglets. Higher frequencies were found of fimbria F4 and F18 and enterotoxins LT, STa and STb. Significant association was found to F4, LT, STa and STb; between F18 and STa and STx2e; between F5 and LT, STa and STb. The most frequent virotypes were F18-STa, F4-LT-STa-STb, F4-STa, F4-LT-STb and F18-STa-STx2e. Beta-hemolysis was observed in 47.4% of samples and there was significant association between hemolytic samples and virulence factors F4, F18, STa and STx2e. Regarding fecal consistency, there was significant association of liquid feces and F4 fimbria, STa toxin and virotypes F4-STa and F4-F5-LT-STa-STb. Since there was significant association of ETEC and liquid feces in nursery piglets, it is important to prioritize the sampling of liquid feces for the diagnosis etiologic cause of diarrhea.

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Swine dysentery (SD) is characterized by a severe mucohemorrhagic colitis caused by infection with Brachyspira species. In infected herds the disease causes considerable financial loss due to mortality, slow growth rates, poor feed conversion, and costs of treatment. B. hyodysenteriae is the most common etiological agent of SD and infection is usually associated with disease. However, isolated reports have described low pathogenic strains of B. hyodysenteriae. The aim of this study was to describe an experimental infection trial using a subclinical B. hyodysenteriae isolated from an animal without clinical signs and from a disease-free herd, to evaluate the pathogenicity and clinical pathological characteristics compared to a highly clinical isolate. Forty-eight 5-week-old pigs were divided into three groups: control, clinical and the subclinical isolates. The first detection/isolation of B. hyodysenteriae in samples of the animals challenged with a known clinical B. hyodysenteriae strain (clinical group) occurred 5th day post inoculation. Considering the whole period of the study, 11/16 animals from this group were qPCR positive in fecal samples, and diarrhea was observed in 10/16 pigs. In the subclinical isolate group, one animal had diarrhea. There were SD large intestine lesions in 3 animals at necropsy and positive B. hyodysenteriae isolation in 7/15 samples of the subclinical group. In the control group, no diarrhea, gross/microscopic lesions, or qPCR positivity were observed. Clinical signs, bacterial isolation, macroscopic and histologic lesions were significantly difference among groups, demonstrating low pathogenicity of the subclinical isolate in susceptible pigs.

Mycoplasma hyopneumoniae is one of the most challenging respiratory pathogens involved with swine pneumonia worldwide, responsible for a chronic infection with high morbidity, which predisposes secondary bacterial infections in growing and finishing pigs. Advances in diagnostic techniques allowed identification of genetic characteristics associated with high antigenic and proteomic variability among bacterial strains. This study aimed to evaluate the genetic diversity of M. hyopneumoniae strains in lungs with pneumonic lesions obtained from 52 pig farms located in Minas Gerais, one of the largest swine production states in Brazil. Genotyping was performed using multilocus variable number of tandem repeat (VNTR) analysis (MLVA), targeting two loci encoding P97 and P146 adhesins VNTR. The results showed that this agent is widely disseminated in pig farms and there is a high polymorphism of M. hyopneumoniae variants circulating in the state of Minas Gerais. Different M. hyopneumoniae genotypes are randomly distributed in several regions of the state, with no specific geographic population structure pattern. M. hyopneumoniae association with viral agents was sporadic (3.17% with Influenza A and 1.9% with PCV2).

Brachyspira hyodysenteriae and Lawsonia intracellularis coinfection has been observed in the diagnostic routine; however, no studies have evaluated their interaction. This study aimed to characterize lesions and possible synergisms in experimentally infected pigs. Four groups of piglets, coinfection (CO), B. hyodysenteriae (BRA), L. intracellularis (LAW), and negative control (NEG), were used. Clinical signals were evaluated, and fecal samples were collected for qPCR. At 21 days post infection (dpi), all animals were euthanized. Gross lesions, bacterial isolation, histopathology, immunohistochemistry, and fecal microbiome analyses were performed. Diarrhea started at 12 dpi, affecting 11/12 pigs in the CO group and 5/11 pigs in the BRA group. Histopathological lesions were significantly more severe in the CO than the other groups. B. hyodysenteriae was isolated from 11/12 pigs in CO and 5/11 BRA groups. Pigs started shedding L. intracellularis at 3 dpi, and all inoculated pigs tested positive on day 21. A total of 10/12 CO and 7/11 BRA animals tested positive for B. hyodysenteriae by qPCR. A relatively low abundance of microbiota was observed in the CO group. Clinical signs and macroscopic and microscopic lesions were significantly more severe in the CO group compared to the other groups. The presence of L. intracellularis in the CO group increased the severity of swine dysentery.