Methicillin-resistant Staphylococcus aureus (MRSA) is an important nosocomial pathogen that shows resistance to many antibiotics and is usually associated with serious infections. Having the ability for biofilm formation increases resistance to antibiotics. Sanguisorba officinalis L. is a perennial plant that is distributed in the northern districts of China and has been used as a traditional Chinese medicine. In this study, the effect of S. officinalis on MRSA strain SA3 isolated from a dairy cow with mastitis was evaluated by testing the growth and biofilm formation ability of MRSA cultured with or without ethanol extracts of S. officinalis. The results showed that the ethanol extract of S. officinalis strongly inhibited the biofilm formation of MRSA. With a confocal laser scanning microscope system, we observed that the biofilm structure of the test group with the addition of S. officinalis appeared looser and had less biomass compared with the control group without S. officinalis. Furthermore, we found that the transcript levels of the icaADBC operon remarkably decreased upon addition of the ethanol extract of S. officinalis, indicating that S. officinalis inhibits biofilm formation of MRSA in an ica-dependent manner.

Escherichia coli, Pasteurella multocida, Proteus mirabilis, Pseudomonas aeruginosa, Salmonella spp. and Staphylococcus aureus are six bacterial pathogens of avian. However, these pathogens may cause many similar pathological changes, resulting in clinical isolates that are difficult to quickly and simultaneously detect and identify. Here, a multiplex polymerase chain reaction (m-PCR) assay is reported to rapidly identify targets genes (phoA, KMT1, ureR, toxA, invA, and nuc) of these six pathogens in clinical samples. Six pairs of specific primers were designed. The optimal reaction conditions, specificity, and sensitivity of the m-PCR assay were investigated. The results showed that betaine remarkably improved amplification of the target genes. Specific test results showed that all six pathogens were detected by the proposed m-PCR protocol without cross-amplification with viruses or parasites. Sensitivity test results showed that the m-PCR system could amplify the six target genes from bacterial genomes or cultures with template amounts of 500 pg or 2.8–8.6 × 10³ colony forming units, respectively. Furthermore, the six bacterial pathogens isolated from the infected tissue samples were successfully identified. The proposed m-PCR assay is a useful tool to monitor and diagnose bacterial infection in birds with high specificity, sensitivity and throughput.

Avian pathogenic Escherichia coli (APEC) is a major bacterial infectious disease that may lead to local or systemic infections in chickens with clinical manifestations. The irp2-fyuA gene cluster has been confirmed to be the main genes involved in the synthesis of HPI. The objective of this study was to determine the influence of the irp2 and fyuA genes in the high pathogenicity island (HPI) of avian pathogenic Escherichia coli (APEC) on its pathogenicity by knocking out these genes. The ΔAE17 (lacking irp2) and ΔΔAE17 (lacking irp2 and fyuA) strains of APEC were constructed. The ΔAE17 and ΔΔAE17 strains showed significantly impaired capacity to adhere onto DF-1 cells. The LD₅₀ results indicated that the virulence of the ΔAE17 and ΔΔAE17 strains was decreased in comparison with that of the AE17 strain. We concluded that the knock-out of the core HPI genes weakened APEC adhesion onto DF-1 cells, inhibited transcription of virulence genes, and reduced pathogenicity in chicks. The effects of genetic deletion of irp2 and fyuA on APEC were more severe than those produced by deletion of irp2 only, indicating that irp2 and fyuA co-regulate APEC pathogenicity.