Molecular ecological analysis of porcine ileal microbiota responses to antimicrobial growth promoters1

Abstract

Cultivation-independent microbial molecular ecology approaches were used to examine the effects of antibiotic growth promoters on the pig ileal microbiota. Five-week-old barrows were fitted with a simple T-cannula at the distal ileum. Three diets meeting or exceeding the minimum nutrient requirements were fed for 5 wk and supplemented as follows: 1) negative control (no antibiotic; n = 5), 2) continuous tylosin administration (n = 5), and 3) an antibiotic rotation sequence (wk 1, chlorotetracycline sulfathiazole penicillin; wk 2, bacitracin and roxarsone; wk 3, lincomycin; wk 4, carbadox; wk 5, virginiamycin; n = 5). Ileal luminal contents were collected for DNA isolation at the end of each of the 5 wk of the testing period. The V3 region of 16S rDNA was amplified by PCR and analyzed via denaturing gradient gel electrophoresis (DGGE) and quantitative polymerase chain reaction (qPCR). Resulting PCR-DGGE band numbers (bacterial species) were counted, and the banding patterns analyzed by calculating Sorenson's pairwise similarity coefficients (C(S)), an index measuring bacterial species in common among samples. Band numbers and total bacterial DNA concentrations decreased (P < 0.05) temporally in antibiotic-treated pigs compared with controls. Comparisons between treatments yielded low intertreatment C(S) indices, indicating treatment-dependent alterations in banding patterns, whereas intratreatment comparisons revealed increased homogeneity in antibiotic-treated vs. control pigs. Sequence analysis of treatment-specific bands identified three Lactobacillus, one Streptococcus, and one Bacillus species that were diminished with antibiotic rotation treatment, whereas tylosin selected for the presence of L. gasseri. Lactobacillus-specific qPCR was performed and analyzed as a percentage of total bacteria to further evaluate the effects of antibiotic administration on this genus. Total bacteria were decreased (P < 0.05) by tylosin and rotation treatments, whereas the percentage of lactobacilli increased (P < 0.05) by d 14 and through d 28 in tylosin-treated pigs. The decrease in total bacteria by antibiotics may reduce host-related intestinal or immune responses, which would divert energy that could otherwise be used for growth. Conversely, the ability of tylosin to improve animal growth may relate to its apparent selection for lactobacilli, commensals known to competitively exclude potentially pathogenic species from colonizing the intestine.

Microbial shifts in the swine distal gut in response to the treatment with antimicrobial growth promoter, tylosin

“…In previous studies using pigs as an animal model, certain species of Lactobacillus have been shown to increase in concentration in AGP-treated pigs (11,12,20). In this study we also detected a relative increase in the concentration of the genus Lactobacillus.…”

“…In comparing the results reported here with those from other studies using AGPs, differences in the microbial population shifts did occur (11,12,20). It is unclear why these differences occurred, but is likely related to differences in the AGP used.…”

Effect of colistin and tylosin used as feed additives on the performance, diarrhea incidence, and immune response of nursery pigs

“…One mechanism that may explain this improved performance is an increase in the relative mass of lactobacilli in the intestinal tract when compared to enterogenic bacteria, owing to a significant decrease of the latter (COLLIER et al, 2003;BOSI et al, 2011). Therefore, because of the prevalence of lactobacilli within the small intestine, where the majority of nutrient absorption occurs, the alteration of these bacteria is a potentially important mechanism involved in antibioticinfluenced animal growth (COLLIER et al, 2003). Macrolides are known to be minimally effective against Gram-negative bacteria in the intestine because of the outer membrane permeability barrier of Gram-negative bacteria.…”

Subtherapeutic use of antibiotics in pork production: Risks and alternatives

“…There have been numerous studies demonstrating a beneficial effect of feeding pigs Lactobacillus species (Cho et al 1992;Abe et al 1995;Tortuero et al 1995;Bomba et al 1998;Ragland and Adeola 2002) and Bacillus species (Bonomi 1992;Vassalo et al 1997;Zani et al 1998;Adami and Cavazzoni 1999;Kyriakis et al 1999), while fewer positive effects have been found using Enterococcus species (Jin et al 2000). In swine, the use of probiotics appears to give more consistent and positive effects in piglets than in grower-finisher pigs (Savage 1977;Cole 1991). Pollman et al (1980) demonstrated improved average daily gain (4.5%) and feed conversion (FC) (7.2%) in starter pigs fed L. acidophilus, compared with control animals receiving no antibiotic or probiotic -results that are consistent with documented benefits of subtherapeutic antibiotics (Doyle 2001).…”

“…Antibiotics added to swine feed in subtherapeutic doses have been reported to improve growth rate (Cromwell 2002;Collier et al 2003). Although the mechanisms involved with the growth-promoting effects of antibiotics are not clearly understood, it has been postulated that they increase growth rate as a result of improved gut health, nutrient utilization and improved feed conversion efficiency (Visek 1978).…”