Mannheimia spp. are veterinary pathogens that can cause mastitis and pneumonia in domestic cattle and sheep. While Mannheimia glucosida can be found as normal flora in oral and respiratory mucosa in sheep, there have been no reported cases of human infection with this organism.

The mosaic structure and molecular evolution of the leukotoxin operon (lktCABD) was investigated by nucleotide sequence comparison of the lktC, lktB, and lktD genes in 23 Mannheimia (Pasteurella) haemolytica, 6 Mannheimia glucosida, and 4 Pasteurella trehalosi strains. Sequence variation in the lktA gene has been described previously (R. L. Davies et al., J. Bacteriol. 183:1394-1404, 2001). The...

Florfenicol in vitro activities for a total of 756 bacterial isolates from respiratory tract infections of cattle and swine were comparatively investigated by the agar diffusion method and the microdilution broth method. Florfenicol showed high in vitro activity against Pasteurella multocida, Mannheimia haemolytica, Actinobacillus pleuropneumoniae, and Streptococcus suis, with all of the isolat...

Lung tissue removed from neonatal calves with acute Mannheimia haemolytica pneumonia showed that rapid up-regulation of the basal mRNA expression of tracheal antimicrobial peptide (TAP), NF-kappa B, and intercellular adhesion molecule 1 occurred after infection; TAP and interleukin 8 expression were highly correlated. This work suggests that the coordinated expression of beta-defensin and infla...

Mannheimia haemolytica, Pasteurella multocida, and Bibersteinia trehalosi have been identified in the lungs of pneumonic bighorn sheep (BHS; Ovis canadensis). Of these pathogens, M. haemolytica has been shown to consistently cause fatal pneumonia in BHS under experimental conditions. However, M. haemolytica has been isolated by culture less frequently than the other bacteria. We hypothesized th...

Mannheimia haemolytica is a major bacterial component of bovine respiratory disease (BRD); unfortunately, very little is known about M. haemolytica transmission dynamics among cattle. Identifying potential variation in M. haemolytica populations over time and induction of nasopharyngeal colonization and subsequent shedding are 2 areas where knowledge is lacking. In our study, 2 separate loads o...

Leukotoxin-producing Mannheimia haemolytica consistently causes fatal pneumonia in bighorn sheep (BHS) under experimental conditions. Surprisingly, by culture methods, it has been isolated from pneumonic BHS lungs less frequently than other bacteria. However, in one study PCR assays detected M. haemolytica from over 70% of the pneumonic lung samples that were negative for this organism by cultu...

Mannheimia haemolytica leukotoxin is produced during the logarithmic growth phase in submerged culture in RPMI 1640 medium with and without the addition of foetal calf serum or albumin. In order to establish a pattern of optimal leukotoxin production in small volumes in submerged cultures and to define some parameters involved, two high leukotoxin producing Mannheimia haemolytica strains were g...

BACKGROUND Mannheimia haemolytica is an important etiological agent in bovine respiratory disease. OBJECTIVES Explore risk factors for recovery of susceptible and resistant M. haemolytica in feedlot cattle and explore associations with health outcomes. ANIMALS Cattle (n = 5,498) from 4 feedlots sampled at arrival and later in feeding period. METHODS Susceptibility of M. haemolytica isolat...

Iron-regulated outer membrane proteins (IROMPs) in Mannheimia haemolytica A1, which function as a receptor for complexes containing iron ions, are induced by iron deficiency in the growth environment of the bacteria. Densitometric analysis of SDS-PAGE separation showed expression of IROMPs of 71, 77, and 100 kDa in the case of bacteria grown in a medium with 2,2-dipyridyl. The electrophoregrams...