No abstract

Mycobacterium tuberculosis complex (MTC) comprises a group of bacteria that have a high degree of genetic similarity. Two species in this group, Mycobacterium tuberculosis and Mycobacterium bovis, are the main cause of human and bovine tuberculosis, respectively. M. bovis has a broader host range that includes humans; thus, the differentiation of mycobacterium is of great importance for epidemiological and public health considerations and to optimize treatment. The current study aimed to evaluate primers and molecular markers described in the literature to differentiate M. bovis and M. tuberculosis by PCR. Primers JB21/22, frequently cited in scientific literature, presented in our study the highest number of errors to identify M. bovis or M. tuberculosis (73%) and primers Mb.400, designed to flank region of difference 4 (RD4), were considered the most efficient (detected all M. bovis tested and did not detect any M. tuberculosis tested). Although also designed to flank RD4, primers Mb.115 misidentified eight samples due to primer design problems. The results showed that RD4 is the ideal region to differentiate M. bovis from other bacteria classified in MTC, but primer design should be considered carefully.

Suid herpesvirus 1 (SuHV-1) is the causative agent of pseudorabies (PR), a disease of great importance due to the huge losses it causes in the swine industry. The aim of this study was to determine a method for genotyping SuHV-1 based on partial sequences of the gene coding for glycoprotein C (gC) and to elucidate the possible reasons for the variability of this region. A total of 109 gCsequences collected from GenBank were divided into five major groups after reconstruction of a phylogenetic tree by Bayesian inference. The analysis showed that a portion of gC (approximately 671 bp) is under selective pressure at various points that coincide with regions of protein disorder. It was also possible to divide SuHV-1 into five genotypes that evolved under different selective pressures. These genotypes are not specific to countries or continents, perhaps due to multiple introduction events related to the importation of swine.

RESUMORealizou-se a detecção do gene de Staphylococcus aureus, de enterotoxinas e de resistência à meticilina com extração de DNA feita diretamente de amostras de leite. Das 200 amostras estudadas, 145 (72,5%) amplificaram o gene femA, e estas foram analisadas quanto à presença dos genes sea, seb, sec e mecA. Os genes das enterotoxinas mais prevalentes foram: sea (60%), seb (37,9%) e sec (6,9%). Foram encontradas 18 amostras de leite (11,0 %) com S. aureus portadores do gene mecA. A detecção de S. aureus diretamente do leite, sem a necessidade de isolamento bacteriano e a caracterização do potencial enterotoxigênico, demonstra que a técnica de PCR é muito útil para estudos epidemiológicos das infecções estafilocócicas da glândula mamária. O alto percentual (72,5%) de amostras de leite positivas para a presença do gene femA sugere que S. aureus constitui um dos principais agentes causadores de infecções intramamárias na microrregião de Sete Lagoas-MG e que seu potencial enterotoxigênico e presença do gene mecA, que identifica o S. aureus resistente à meticlina, representa um risco potencial à saúde pública. Palavras-chave: Staphylococcus aureus, enterotoxinas, MRSA, PCR ABSTRACT This work was performed to detect the