Characteristics of Aerococcus viridans isolated from bovine subclinical mastitis and its effect on milk SCC, yield, and composition

Meng Sun, Jian Gao, Tariq Ali, Dan Yu, Shiyao Zhang, Saeed U. Khan, Séamus Fanning, Bo Han*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

13 Citations (Scopus)


Aerococcus viridians (A. viridans), an environmental Gram-positive bacterium, has been documented to be associated with bovine mastitis. However, its exact role in bovine mastitis and the changes it brings about in milk characteristics are not yet known. The objectives of the current study were to describe the antibiotic resistance of A. viridans from bovine mastitis as well as the correlation between existence of this pathogen in udders and the somatic cell counts (SCC), daily milk yield, and composition of individual cow. One-year sampling for subclinical mastitis composite milk was conducted based on monthly DHI data from September 2013 to August 2014, in a commercial herd located in Beijing, China. All samples were cultured and pathogens were identified using microbiology method. A. viridians isolates were further identified by API identification system and 16S ribosomal RNA (rRNA) sequencing method. Kirby-Bauer disk diffusion method was used to test the antibiotic resistance of A. viridians against kinds of antimicrobial substance. SCC, milk yield, and milk composition data were from monthly Dairy Herd Improvement (DHI) results. Results showed that a total of 279 (16.67%) A. viridans isolates were identified from among 1674 bacterial isolates cultured from milk samples with high SCC. The incidence of mastitis caused by A. viridans was the highest (48–53%) during the summer season. Majority of the isolates were susceptible to most of antimicrobial compounds tested, especially to β-lactams, but were found to be resistant (50–90%) to aminoglycosides, sulfonamides, and tetracycline. The average SCC of the A. viridans infected cows was significantly higher (1000.0 × 103 cells/mL) (P < 0.01) as compared to healthy cows (72.4 × 103 cells/mL) and daily milk yield decreased (P > 0.05) by 1.86 kg/day. Reductions were also observed in fat content (P > 0.05), lactose (P < 0.01), and total solids (P > 0.05), whereas protein content increased significantly (P < 0.01) in milk samples of cows infected with A. viridans. The results of this study suggest that A. viridans could be considered as an emerging aetiological agent of bovine subclinical mastitis wherein it exerts an effect on SCC, milk yield, and composition.

Original languageEnglish
Pages (from-to)843-849
Number of pages7
JournalTropical Animal Health and Production
Issue number4
Early online date20 Mar 2017
Publication statusPublished - 01 Apr 2017
Externally publishedYes

Bibliographical note

Funding Information:
This research was supported by the Chinese Twelfth “Five-year” National Science and Technology Support Project (No. 2012BAD12B03), National Education Ministry’s Major Project (No. 313054), Specialized Research Fund for the Doctoral Program of Higher Education (SRFDP) State Education Ministry (No. 20120008110042), High-end Foreign Experts Recruitment Program (No. GDT20141100043), and the National Natural Science Foundation of China (No. 31572587).

Publisher Copyright:
© 2017, Springer Science+Business Media Dordrecht.


  • Aerococcus viridans
  • Antibiotic susceptibility
  • Daily milk yield
  • Milk composition
  • Subclinical mastitis

ASJC Scopus subject areas

  • Food Animals
  • Animal Science and Zoology


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