Isolation And Identification Of Bacteria From Sow Endometritis And Optimization Of Treatment Technology In Large-scale Pig Farms In Guangxi

Sow endometritis is one of the important causes of reproductive disorders in sows.It usually causes irregular estrus,infertility and abortion in sows,and in serious cases,it may lead to sepsis and even death in sick pigs,which poses a major threat to the economic benefits of farms.Sow endometritis is usually caused by multiple pathogenic microorganisms,such as bacteria,viruses,parasites,leptospira,chlamydia and so on.Bacterial infection is the most important causative factor of endometritis,At this stage,farms often use high doses of broad-spectrum antibacterial drugs to reduce the incidence of endometritis.However,blind and untargeted medication can increase the cost of breeding and lead to frequent occurrence of bacterial multi-drug resistance,which in turn seriously damages the economic efficiency of pig farms.In addition,the epidemiology of endometritis pathogens in sows in Guangxi is not yet clear.Understanding the epidemiology of sow endometritis pathogens in specific geographical areas and exploring the antibiotic susceptibility of local strains will help the prevention and control of sow endometritis.Therefore,this study investigated and analyzed the prevalence of sow endometritis pathogenic bacteria in large-scale pig farms by isolating and identifying bacteria from the uterine contents of sows suffering from endometritis in Guangxi.Meanwhile,in this study,based on the results of drug sensitivity assays of clinical isolates,sensitive drugs of local strains were screened and antibiotic combinations were applied on diseased sows to establish a drug regimen that could effectively cure endometritis in sows.The specific work is as follows:1.Isolation and identification of endometritis pathogenic bacteria and epidemic characteristics in GuangxiIn this study,a total of 165 samples of uterine contents of sows with endometritis were collected from three large-scale pig farms in Guangxi.The results of bacterial isolation and identification showed that a total of 26 species and 321 strains of bacteria were isolated.Among them,Escherichia coli,Enterococcus faecalis,Enterococcus hirae,Enterococcus faecium,Proteus mirabilis,Streptococcus dysgalactiae and Staphylococcus hyicus were the main isolates of sow endometritis,with strains 101,46,25,25,21,20 and 19,respectively.In this study,Streptococcus multilocularis,Streptococcus pasteurii,Streptococcus oligosaccharidis,Streptococcus gallotrophicus and Actinobacillus roxellanae,which have not been reported in the literature,were also isolated from samples of sow uterine contents for the first time.Mixed bacterial infections in the samples were significant,with 105(64%)samples carrying multiple bacteria at the same time.Among them,61 samples carried two bacteria at the same time,34 samples carried three bacteria and 10 samples carried four bacteria.2.Antibiotic sensitivity testing and analysis of isolated strainsSeventeen clinically used antibiotics were selected for antibiotic sensitivity tests on 321 local strains.The results showed that 197(61.37%),194(60.44%),183(57.01%)strains were sensitive to gentamicin,enrofloxacin and florfenicol respectively;in contrast,more than 50% of the strains showed resistance to the rest of the antibiotics,among which resistance to sulfadiazine sodium,sulfamethoxine sodium and lincomycin was the most serious,reaching 316(98.44%),310(96.57%),307(95.64%)strains respectively.β-lactams are often used to prevent and control sow endometritis in the pig farms where the samples were sourced.The resistance rate of β-lactams in this trial ranged from 53% to 68% and was not effective in sterilizing the isolated strains.3.The combination of antibiotics can improve the cure rate of sow endometritisAs sow endometritis is mostly a mixed infection with a high number of drug-resistant strains,a single broad-spectrum antibiotic cannot effectively cure it,and blind and high-dose administration can lead to a vicious circle of decreasing antibiotic sensitivity and multiple drug resistance of bacteria.The sample source pig farms often use β-lactams to prevent and control endometritis in sows.Therefore,based on the results of drug sensitivity experiments,we screened two antibiotic combination combinations(gentamicin + amoxicillin,enrofloxacin + amoxicillin)to expand the antibacterial spectrum of the drugs.The results of in vitro experiments,such as antibiotic combination sensitivity test and bactericidal curve measurement,showed that the two groups of compound drugs mainly showed synergistic or additive effects and had better bactericidal effects compared to single drugs.The results of the in vivo treatment of endometritis in sows showed that the cure rate of the two groups of combination drugs was also improved compared with the original treatment plan(Long-lasting amoxicillinin)of the farm.The best treatment is to administer gentamicin at 3.5 mg/kg body weight once a day for 2 d and to feed amoxicillin at 20mg/kg body weight twice a day for 3 d.The clinical symptoms of endometritis and the estrus rate of sows within 7 d of weaning were significantly improved and increased.This method assisted the farm to treat sow endometritis while slowing down the development of bacterial drug resistance.