Modeling Co-Infection by Streptococcus suis and Haemophilus parasuis Reveals Influences on Biofilm Formation and Host Response

Abstract

Streptococcus suis (S. suis) and Haemophilus parasuis (H. parasuis) are two primary pathogens currently affecting the porcine industry. They often cause encephalitis and arthritis. They also frequently co-infect in clinical settings. In the current study, we identified significant correlations between S. suis and H. parasuis. The results from CI versus RIR suggested that S. suis and H. parasuis were competitive in general. Compared to mono-species biofilm, the biomass, bio-volume, and thickness of mixed-species biofilms were significantly higher, which was confirmed using crystal violet staining, confocal laser scanning microscopy, and scanning electron microscopy. Compared to mono-species biofilm, the viable bacteria in the mixed-species biofilms were significantly lower, which was confirmed using the enumeration of colony-forming units (CFU cm−2). The susceptibility of antibiotics in the co-culture decreased in the planktonic state. In contrast, biofilm state bacteria are significantly more difficult to eradicate with antibiotics than in a planktonic state. Whether in planktonic or biofilm state, the expression of virulence genes of S. suis and H. parasuis in mixed culture was very different from that in single culture. Subsequently, by establishing a mixed infection model in mice, we found that the colonization of the two pathogens in organs increased after mixed infection, and altered the host’s inflammatory response. In summary, our results indicate that S. suis and H. parasuis compete when co-cultured in vitro. Surprisingly, S. suis and H. parasuis synergistically increased colonization capacity after co-infection in vivo. This study elucidated the interaction between S. suis and H. parasuis during single infections and co-infections. Future studies on bacterial disease control and antibiotic treatment should consider the interaction of mixed species.

The establishment and application of a one‐step multiplex real‐time polymerase chain reaction assay for the detection of Streptococcus suis, Streptococcus suis serotype 2, and Glaesserella parasuis

“…Currently, due to the continuous development of pig farm intensification, there is a prevalence of GPS-caused diseases in many regions of China, posing a serious threat to the pig farming industry. In recent years, there has been an increase in morbidity and mortality caused by mixed or secondary infections of SS and GPS [1,5]. In a study conducted by Rao et al in Guangxi Province, China, it was reported that SS accounted for 65.21% of pig respiratory pathogens, GPS accounted for 48.19% of pig respiratory pathogens, whereas mixed infections of both were found to account for 13.10% of all cases [34].…”

“…Streptococcus suis (S. suis, SS) and Glaesserella parasuis (G. parasuis, GPS) are most common pathogens in the world of infected pigs widely; both could cause inflammatory infections such as septicemia, meningitis, polyserositis, arthritis, and pneumonia [1]. The number of incidences of porcine streptococcal disease and GPS disease ranked top 10 swine diseases consistently in China from 2018 to 2021 [2,3].…”

“…The number of incidences of porcine streptococcal disease and GPS disease ranked top 10 swine diseases consistently in China from 2018 to 2021 [2,3]. SS and GPS, two vital porcine respiratory resident and pathogenic bacteria, cause clinical symptoms and pathological changes by mixed infection, increasing the complexity of the disease and the difficulty of diagnosis [1,4,5]. There are 35 serotypes of SS depending on different capsular antigens [6], of which Streptococcus suis serotype 2 (SS2) infections are classified as zoonotic infections and are the most predominant causative organisms in both swine and human populations [7].…”

Emerging Approaches for Mitigating Biofilm-Formation-Associated Infections in Farm, Wild, and Companion Animals

“…are known to form biofilms in the respiratory mucosa of animals, leading to bronchitis, pneumonia, and lung abscesses. Respiratory biofilm-related infections are of significant concern in livestock farming and captive animal facilities [ 3 , 22 , 23 ].…”

“…Systemic invasion is characterized by fibrinous polyserositis inflammation, polyarthritis, and fibrinous meningitis, and causes significant losses to producers due to reduction in weight gain, increases in the use of drugs, dead animals, and carcass depreciation [ 112 ]. Although the role of biofilm in H. parasuis pathogenesis is not clear, the expression of genes with putative function in biofilm formation has been detected, which plays a crucial role in the pathogenesis of the disease [ 22 ].…”