Rhouma Mohamed, Fairbrother John Morris, Thériault William, Beaudry Francis, Bergeron Nadia, Laurent-Lewandowski Sylvette, Letellier Ann
Chaire de recherche industrielle du CRSNG en salubrité des viandes (CRSV), Faculté de médecine vétérinaire - Université de Montréal, 3200 rue Sicotte, Saint-Hyacinthe, QC, J2S 7C6, Canada.
Groupe de recherche et d'enseignement en salubrité alimentaire (GRESA), Faculté de médecine vétérinaire - Université de Montréal, 3200 rue Sicotte, Saint-Hyacinthe, QC, J2S 7C6, Canada.
BMC Microbiol. 2017 Jan 5;17(1):6. doi: 10.1186/s12866-016-0915-0.
Enterotoxigenic Escherichia coli (ETEC) strains producing multiple enterotoxins are important causes of post-weaning diarrhea (PWD) in pigs. The aim of the present study was to investigate the fecal presence of ETEC enterotoxin as well as F4 and F18 genes as an indicator of colistin sulfate (CS) efficacy for treatment of PWD in pigs. Forty-eight piglets were weaned at the age of 21 days, and were divided into four groups: challenged treated, challenged untreated, unchallenged treated, and unchallenged untreated. Challenge was performed using 10 CFU of an ETEC: F4 strain, and treatment was conducted using oral CS at the dose of 50,000 IU/kg. The fecal presence of genes encoding for STa, STb, LT, F4 and F18 was detected using PCR.
The PCR amplification of ETEC virulence genes showed that nearly 100% of pigs excreted genes encoding for STa and STb toxins in the feces before the challenge. These genes, in the absence of the gene encoding F4, were considered as a marker for F4-negative ETEC. One day after ETEC: F4 oral challenge pigs in the two challenged groups excreted the genes encoding LT and F4 in the feces. These genes were considered as a marker for F4-positive ETEC. However, the gene encoding F18 was not detected in any fecal samples of the 4 groups throughout the experiment. After only 3 days of successive oral treatment with CS, a significant reduction in both the F4-positive and negative ETEC populations was observed in the challenged treated group compared to the challenged untreated group (p < 0.0001).
Our study is among the first to report that under controlled farming conditions, oral CS treatment had a significant effect on both fecal F4-positive and F4-negative ETEC in pigs. However, CS clinical efficiency was correlated with non-detection of F4-positive ETEC in the feces. Furthermore the fecal presence of F4-negative ETEC was not associated with clinical symptoms of post-weaning diarrhea in pigs.
产多种肠毒素的产肠毒素大肠杆菌（ETEC）菌株是仔猪断奶后腹泻（PWD）的重要病因。本研究旨在调查ETEC肠毒素以及F4和F18基因在粪便中的存在情况，以此作为硫酸黏菌素（CS）治疗仔猪PWD疗效的指标。48头仔猪在21日龄时断奶，分为四组：攻毒治疗组、攻毒未治疗组、未攻毒治疗组和未攻毒未治疗组。使用10⁸CFU的ETEC:F4菌株进行攻毒，采用50000 IU/kg剂量的口服CS进行治疗。采用PCR检测粪便中编码STa、STb、LT、F4和F18的基因。
ETEC毒力基因的PCR扩增显示，攻毒前近100%的猪粪便中排泄出编码STa和STb毒素的基因。在缺乏编码F4基因的情况下，这些基因被视为F4阴性ETEC的标志物。ETEC:F4口服攻毒一天后，两个攻毒组的猪粪便中排泄出编码LT和F4的基因。这些基因被视为F4阳性ETEC的标志物。然而，在整个实验过程中，四组的任何粪便样本中均未检测到编码F18的基因。连续口服CS仅3天后，与攻毒未治疗组相比，攻毒治疗组中F4阳性和阴性ETEC菌群均显著减少（p＜0 .0001）。
我们的研究是首批报告之一，表明在可控养殖条件下，口服CS治疗对仔猪粪便中F4阳性和F4阴性ETEC均有显著影响。然而，CS的临床疗效与粪便中未检测到F4阳性ETEC相关。此外，F4阴性ETEC在粪便中的存在与仔猪断奶后腹泻的临床症状无关。
