Isolation, identification and virulence determinants of Streptococcus agalactiae from bovine subclinical mastitis in Egypt

Khaled Abd El-Hamid Abd El-Razik,Abdelgayed M Younes,Ehab A Fouad,Amr M Abdou,Abdulaziz M Almuzaini,Amany A Arafa

doi:10.3855/jidc.12668

Khaled Abd El-Hamid Abd El-Razik, Abdelgayed M Younes + Show 4 more

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https://doi.org/10.3855/jidc.12668

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Abstract

This study aimed to investigate the prevalence of contagious mastitis caused by Streptococcus agalctiae (S. agalactiae) in cattle from households and small-scale dairy farms in Egypt. Molecular characterization of S.agalactiae isolates was described including the genetic determinants of virulence to assess the genetic variation in isolated strains of S. agalactiae. Three hundred and sixty milk samples were collected from 90 apparently healthy dairy cows randomly selected from household and small-scale dairy farms were examined by Somatic Cell Count (SCC) as an indicator for subclinical mastitis. S.agalactiae isolates were bacteriologically and molecularly identified followed by identification of virulence genes using PCR. A total of 172 milk samples (47.77%) were positive with SCC > 200×103/ml. Bacteriological examination of the positive SCC milk samples revealed that 28 (16.28%) of the isolates were S.agalactiae. Molecular examination using PCR confirmed only 22 isolates of S. agalactiae (12.8%). Moreover, we used the pattern of virulence genes to address the genetic variation of S. agalactiae strains isolated from cases of contagious mastitis in cattle in Egypt. Virulence genes hylB, cylE, iagA, and bac were determined in 100%, 68.2%, 13.6% and 100% of isolates respectively. The use of molecular methods for the identification of the causative agent in mastitis confirmed that, in Egypt, Streptococcus agalactiae is considered as one of the predominant infectious agents among contagious mastitis causing pathogens. The pattern of virulence genes presented the genetic diversity of highly virulent S. agalactiae strains isolated from cases of contagious mastitis in cattle in Egypt.

Highlights

This study aimed to investigate the prevalence of contagious mastitis caused by Streptococcus agalctiae (S. agalactiae) in cattle from households and small-scale dairy farms in Egypt
Three hundred and sixty milk samples collected from 90 apparently healthy dairy cows were examined by Somatic Cell Count (SCC) as an indicator for subclinical mastitis
Virulence genes In the present study, screening of virulence genes was performed by Polymerase Chain Reaction (PCR) using the primers and reaction conditions in Table 1 to detect hylB, cylE, iagA, and bac genes (Figure 2)

Summary

Introduction

This study aimed to investigate the prevalence of contagious mastitis caused by Streptococcus agalctiae (S. agalactiae) in cattle from households and small-scale dairy farms in Egypt. We used the pattern of virulence genes to address the genetic variation of S. agalactiae strains isolated from cases of contagious mastitis in cattle in Egypt. The pattern of virulence genes presented the genetic diversity of highly virulent S. agalactiae strains isolated from cases of contagious mastitis in cattle in Egypt. The main contagious mastitis pathogens are Staphylococcus aureus, Streptococcus agalactiae, and Mycoplasma spp They primarily infect the cow’s udder and they can spread from cow to cow during the time of milking [4]. Streptococcus agalactiae is a contagious obligate gram-positive bacterium of the bovine mammary gland, and mostly causes subclinical mastitis and elevated cow SCC [6].

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