Biofilm formation and genotyping of Staphylococcus aureus bovine mastitis isolates: Evidence for lack of penicillin-resistance in Agr-type II strains

• Published in: Veterinary microbiology Vol. 137; no. 1; pp. 83 - 89
• Main Authors: Melchior, M.B., van Osch, M.H.J., Graat, R.M., van Duijkeren, E., Mevius, D.J., Nielen, M., Gaastra, W., Fink-Gremmels, J.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 28-05-2009; Elsevier
• Subjects: Agr-type; Animals; Anti-Bacterial Agents - pharmacology; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Bacteriology; Biofilm; Biofilms - growth & development; Biological and medical sciences; Bovine mastitis; Cattle; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Bacterial - physiology; Genotype; Genotyping; Mastitis, Bovine - microbiology; Microbiology; Miscellaneous; Penicillin Resistance - genetics; Penicillin-resistance; Penicillins - pharmacology; Staphylococcal Infections - microbiology; Staphylococcal Infections - veterinary; Staphylococcus aureus; Staphylococcus aureus - genetics; Staphylococcus aureus - physiology; Trans-Activators - genetics; Trans-Activators - metabolism; Biofilm; Bovine mastitis; Genotyping; Agr-type; Penicillin-resistance; Staphylococcus aureus; Microbiology; Penicillin derivatives; Penicillin; Bacteria; Micrococcales; Micrococcaceae; Ungulata; Mastitis; Typing; Bovine; β-Lactams; Genotype; Strain; Resistance; Mammary gland diseases; Vertebrata; Antibiotic; Mammalia; Isolate; Artiodactyla; Antibacterial agent; Veterinary
• ISSN: 0378-1135; 1873-2542
• DOI: 10.1016/j.vetmic.2008.12.004

The increasing evidence for a role of biofilm formation in bovine mastitis caused by
Staphylococcus aureus led to further investigations on biofilm formation by
S. aureus isolates from mastitis in two growth media (TSBg and bovine milk serum). The ability of 99
S. aureus strains that were recently isolated or obtained from a culture collection (historical strains) to form biofilm, in both growth media as well as the correlation of biofilm formation with the presence of the
ica-,
bap-, and
IS257 genes are described. These genes have been correlated with biofilm formation by human
S. aureus isolates. All strains were also genotyped with respect to their
Agr-type and -subtype, and for the presence of the antibiotic resistance genes
blaZ and
smr by PCR. The prevalence of the
Agr-types and the investigated genes and their correlation with biofilm formation were statistically evaluated.
The
Agr-type of a strain had a marked effect on the biofilm formation, by that strain, however in contrast to human isolates no significant effect of
ica- and
IS257 genes on biofilm formation was observed. The
bap gene was not found in any of the investigated strains. The presence of biofilm related genes showed a high correlation with the
Agr-type of the strains. The data give evidence for a very strong correlation of
Agr-type I strains and penicillin-resistance in the bovine
S. aureus mastitis strains; none of the
Agr-type II strains was found to harbor penicillin-resistance genes.
These data indicate that the most prevalent
Agr-types in
S. aureus bovine mastitis,
Agr-type I and II, can be regarded as different subspecies, with different abilities for the formation of biofilm in bovine milk serum. The very high correlation between
Agr-type II and penicillin-susceptibility strongly suggests that these strains are not able to accommodate
blaZ genes.