Bacterial interactions in bovine respiratory and reproductive infections

Abstract

The ability of the aerobic bacterial flora from the normal bovine respiratory and reproductive tracts to enhance or inhibit the growth of Pasteurella haemolytica, P. multocida, and Haemophilus somnus was tested in vitro. Six strains of each of these pathogens were cross streaked with each isolate of bovine normal flora. Flora which enhanced the growth of these pathogenic bacteria outnumbered inhibitors four to one. An intermediate number of isolates produced no effect on pathogen growth. Most enhancers were gram positive (Micrococcus, Staphylococcus, Corynebacterium, or Rhodococcus isolates), although several isolates of Moraxella and Actinobacter were also good enhancers. For H. somnus, there were proportionally more organisms which produced marked enhancement among the preputial flora than among the nasal flora, which may account for the greater number of genital carriers than nasal carriers. Bacillus isolates were the most significant inhibitors among the nasal flora, whereas no genus or species from the reproductive tract was noted to produce appreciable inhibition. It is proposed that changes in ratios of inhibitors to enhancers may determine, in part, whether a carrier state or disease occurs. Also, suggestions are made for in vitro use of this phenomenon for diagnostic tests.

The nasopharyngeal microbiota of beef cattle before and after transport to a feedlot

“…In addition to changes in pathogen prevalence, it is possible that alterations in other community bacteria affect BRD pathogen growth. Aerobic bacteria from the bovine respiratory tract have previously been shown to both enhance and inhibit the growth of M. haemolytica and P. multocida in vitro [34], thus the total NP microbiota may be critical to disease susceptibility. In the present study, it was determined that the NP microbiota of calves undergoes numerous alterations, both in community membership and structure, following the first 14 days in the feedlot environment.…”

Probiotic bacteria inhibit the bovine respiratory pathogenMannheimia haemolyticaserotype 1in vitro

“…However, there is limited information on bacteria that inhibit BRD pathogens, including M. haemolytica. Corbeil et al (1985) observed that strains of Streptococcus and Bacillus isolated from the bovine respiratory and reproductive tracts were capable of inhibiting M. haemolytica in vitro. Although the authors did not test any Lactobacillaceae, we have observed a reduced relative abundance of nasopharyngeal Lactobacillus in cattle that develop BRD (Holman et al 2015), suggesting that these bacteria are important in maintaining a healthy respiratory microbiota.…”

“…In contrast, S. thermophilus caused a slight increase in adhesion of M. haemolytica to BBE cells that was significant in the competition assay (increase of 0Á3 log 10 CFU per ml), suggesting that this strain might enhance growth or adhesion of M. haemolytica. Interestingly, Streptococcus viridans has also been shown to enhance the growth of M. haemolytica in vitro (Corbeil et al 1985).…”

“…While host immunity is important in controlling pathogens, there is evidence showing a bacterial component to regulating microbial populations in the bovine respiratory tract. For example, aerobic bacteria isolated from the bovine upper respiratory tract have been shown to both inhibit and enhance growth of M. haemolytica in vitro (Corbeil et al 1985) and Bibersteinia trehalosi (Dassanayake et al 2010) and Pasteurella multocida (Bavananthasivam et al 2012) have previously been described to inhibit M. haemolytica by proximity-dependent mechanisms. Thus, bacterial competition has an important role in the respiratory tract and perhaps commensals could be used as probiotics to inhibit pathogenic bacteria.…”

Intranasal Bacterial Therapeutics Reduce Colonization by the Respiratory Pathogen Mannheimia haemolytica in Dairy Calves

“…Unfortunately, this approach is not always effective in preventing BRD (9) and can be seen as an irrational use of antibiotics leading to the development of antibiotic resistance in the digestive and respiratory microbiota (10). This has been shown by the recent characterization of M. haemolytica and P. multocida displaying multidrug resistance (11,12), which in some instances was linked to resistance genes contained within integrative conjugative elements (13,14). Discovery and development of alternatives to antibiotics to prevent BRD in dairy calves are therefore needed.…”