key: cord-270688-g703hhm4
authors: Zhao, Ge; Zhang, Lujie; Li, Charles; Zhao, Jianmei; Liu, Na; Li, Yuehua; Wang, Junwei; Liu, Liheng
title: Identification of enterobacteria in viscera of pigs afflicted with porcine reproductive and respiratory syndrome and other viral co-infections
date: 2020-07-11
journal: Microb Pathog
DOI: 10.1016/j.micpath.2020.104385
sha: 
doc_id: 270688
cord_uid: g703hhm4

In order to investigate enterobacteria presence involved in the secondary infections in Porcine Reproductive and Respiratory Syndrome (PRRS) pigs with different viral co-infections, we identified enterobacteria for guiding clinical treatment. Twenty-one diseased pigs were diagnosed with the PRRS virus (PRRSV) and other 7 virus primers by PCR/RT-PCR in the lung and spleen samples. Enterobacteria were isolated using MacConkey agar from 5 visceral samples of PRRS pigs, and identified by 16S rDNA sequencing. PRRSV was positive in 100% of the lung samples and 81.0% of the spleen samples. Seven diseased pigs were diagnosed with only PRRSV infection (33.3%), 7 pigs with PRRSV and 1 or 2 other viruses (33.3%) and 7 pigs with PRRSV and more than 2 types of other viruses (33.3%). PRRSV was more inclined to co-infect pigs with porcine group A rotavirus (PARV) with the co-infection rate of 52.4% (11/21). Approximately 13 types of bacteria were successfully isolated from lung, spleen, liver, kidney and lymph node samples of different PRRS pigs. Enterobacteria were isolated in 100% of lung, liver and lymph samples from pigs infected with PRRSV alone. However, the isolation rates were significantly decreased in the more than 3 viruses co-infection group. Escherichia coli was the most prevalent bacterium, followed by Morganella, Proteus, Shigella, Salmonella, Klebsiella and Aeromonas. Most of the isolated enterobacteria were opportunistic pathogens. Therefore, timely combination with antimicrobial agents is necessary for effective treatment of PRRS-infected pigs.

Porcine reproductive and respiratory syndrome (PRRS) is a swine disease caused by a virus, 46 which poses a significant economic threat to the swine industry worldwide [1] . The PRRS death in PRRS infected pigs [3, 4] . 54 In practical production, farmers focus more attention on ways to prevent and treat infected 55 pigs. Farmers employ vaccine inoculation and isolated rearing to prevent infection [5] . 95 The viscera, including lung, spleen, liver, kidney and lymph nodes from the pigs with 96 PRRS were used for enterobacteria isolation. Firstly, the visceral specimen was removed from 97 the plastic bag to a sterile plate under the biosafety cabinets, and 6 sections were cut by using Table 1 . 

Through the above examination, we confirmed that the diseased pigs were indeed infected 143 with PRRSV, simultaneously. We further determined that some other viruses may infect 144 simultaneously with PRRSV. Nevertheless, the real causes of death among the nursery pigs 145 with PRRS may be the pathogens causing secondary infections [3, 4] . Therefore, we further 146 investigated the enterobacterial proliferation from the gut to the surrounding viscera, such as 147 lung, spleen, liver, kidney and lymph nodes. From the enterobacterial isolation and 148 identification results (Table 3) , approximately 13 types of bacteria were successfully isolated 149 from several viscera of different PRRS-positive pigs, and no enterobacterium was isolated in 150 healthy samples.

If only one type of enterobacterium was isolated, the corresponding organ was supposed to 152 be infiltrated by the gut bacteria. Based on this analysis (Figure 2 ), we found that the total 153 enterobacterial isolation rate from kidneys (42.9%, 9/21) were significantly lower (p<0.05), 154 8 and the total rates from the other 4 viscera were comparative in levels. We also found that 155 when pigs were co-infected with more types of viruses, the lower bacterial isolation rate was 156 obtained (p< 0.05). In the PRRSV alone infection group, enterobacteria were detected with a 157 100% positive rate in lung, liver and lymph samples, whereas in the co-infection group with 158 more than 3 types of virus species, the isolation rates in lung, liver, kidney and lymph were 159 significantly decreased. Only the rates from spleens were comparative. In the current study, we first detected 7 other porcine viruses in addition to PRRSV in the 185 lung and spleen samples to investigate the most common viruses that tend to co-infect with 186 PRRSV. The result showed that PRRSV could be detected in 100% of lung samples, 187 indicating the PRRSV infection was really occuring. However, the PRRSV detection rate in 188 lung was higher than in the spleen, which confirmed that it is easier for PRRSV to invade the 189 respiratory system and then affect other organs, such as the spleen [14] . For the 7 detected 

Epidemiology of porcine reproductive and respiratory syndrome (PRRS): an 279 overview

Emergence of fatal 283 PRRSV variants: unparalleled outbreaks of atypical PRRS in China and molecular dissection 284 of the unique hallmark

Effect of porcine 287 reproductive and respiratory syndrome virus infection on the clearance of Haemophilus 288 parasuis by porcine alveolar macrophages

Secondary infection with Streptococcus suis serotype 7 increases the 291 virulence of highly pathogenic porcine reproductive and respiratory syndrome virus in pigs

Diagnosis and treatment of porcine reproductive and 294 respiratory syndrome

A one-step RT-PCR 296 assay to detect and discriminate porcine reproductive and respiratory syndrome viruses in 297 clinical specimens

Differential detection of transmissible gastroenteritis 299 virus and porcine epidemic diarrhea virus by duplex RT-PCR

Nested reverse 302 transcriptase-polymerase chain reaction for the detection of group A rotaviruses

Detection of classical swine fever virus in boar semen by reverse 305 transcription-polymerase chain reaction

Detection of porcine 307 circovirus type 2 in feces of pigs with or without enteric disease by polymerase chain reaction

A multiple 310 SYBR Green I-based real-time PCR system for the simultaneous detection of porcine 311 circovirus type 2, porcine parvovirus, pseudorabies virus and Torque teno sus virus 1 and 2 in 312 pigs

A comparison of virus isolation, polymerase chain reaction

immunohistochemistry, and in situ hybridization for the detection of porcine circovirus 2 and 315 porcine parvovirus in experimentally and naturally coinfected pigs

16S/23S rRNA sequencing

Nucleic acid techniques in bacterial systematic

Pathogenesis of porcine reproductive and respiratory syndrome virus infection in 322 gnotobiotic pigs

Co-infection of Porcine Circovirus Type 2,Porcine Reproductive and Respiratory Disease 325

Syndrome Virus and Porcine Parvovirus

Detection 327 and Analysis of Porcine Circovirus

Reproductive and Respiratory Syndrome Virus, China Animal Husbandry & Veterinary 329

Morganella morganii infections in a general tertiary 332 hospital

Pathogenesis of Proteus mirabilis urinary 334 tract infection

eMedicine from WebMD

Sherris Medical Microbiology

Klebsiella and acute 339 anterior uveitis

Aeromonas spp. clinical microbiology and disease

Etiology analysis of the bacterial secondary 343 infection of PRRSV in Sichuan Province from

Importance of Providencia species as a major cause of travellers' diarrhea

Genetic and biochemical diversity of ureases of Proteus

Morganella species isolated from urinary tract infection

Sphingomonas paucimobilis bloodstream infections associated 353 with contaminated intravenous fentanyl

Multidrug resistant

Acinetobacter baumannii: a descriptive study in a city hospital

Escherichia fergusonii: an emerging 358 pathogen in South Orissa

Increased incidence of 360 urolithiasis and bacteremia during Proteus mirabilis and Providencia stuartii coinfection due 361 to synergistic induction of urease activity

S: Spleen; L: Lung; +: Positive