Lincomycin resistance gene lnu(D) in Streptococcus uberis
Efthymia Petinaki1, Véronique Guérin-Faublée, Vianney Pichereau
1Service de Microbiologie and EA 2128 Relations hôte et microorganismes des épithéliums, Hôpital Côte de Nacre, Université de Caen Basse-Normandie, 14033 Caen Cedex, France.
Abstract:
Streptococcus uberis UCN 42, isolated from a case of bovine mastitis, was intermediately resistant to lincomycin (MIC = 2 microg/ml) while remaining susceptible to clindamycin (MIC = 0.06 microg/ml) and erythromycin. A 1.1-kb SacI fragment was cloned from S. uberis UCN 42 total DNA on plasmid pUC 18 and introduced into Escherichia coli AG100A, where it conferred resistance to both clindamycin and lincomycin. The sequence analysis of the fragment showed the presence of a new gene, named lnu(D), that encoded a 164-amino-acid protein with 53% identity with Lnu(C) previously reported to occur in Streptococcus agalactiae. Crude lysates of E. coli AG100A containing the cloned lnu(D) gene inactivated lincomycin and clindamycin in the presence of ATP and MgCl(2). Mass spectrometry experiments demonstrated that the lnu(D) enzyme catalyzed adenylylation of clindamycin. A domain conserved in deduced sequences of lincosamide O-nucleotidyltransferases Lnu(A), Lnu(C), LinA(N2), and Lin(D) and in the aminoglycoside nucleotidyltransferase ANT(2'') was identified.
Insights
A novel gene, lnu(D), identified in Streptococcus uberis, confers resistance to lincomycin and clindamycin by inactivating these antibiotics. This finding is crucial for understanding and combating antibiotic resistance in veterinary medicine.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Streptococcus uberis is a significant cause of bovine mastitis.
- Antibiotic resistance in mastitis-causing pathogens poses a threat to animal health and food safety.
- Understanding the genetic basis of antibiotic resistance is essential for developing effective treatment strategies.
Purpose of the Study:
- To identify and characterize the genetic determinant responsible for lincomycin and clindamycin resistance in Streptococcus uberis UCN 42.
- To elucidate the mechanism of action of the identified resistance gene.
- To explore the evolutionary relationship of the identified gene with other known resistance genes.
Main Methods:
- Cloning of a DNA fragment from S. uberis UCN 42 into Escherichia coli.
- Gene sequencing and analysis.
- Biochemical assays to determine enzyme activity (inactivation of antibiotics).
- Mass spectrometry to identify the enzymatic reaction products.
Main Results:
- A novel gene, designated lnu(D), was identified and cloned, conferring intermediate resistance to lincomycin and susceptibility to clindamycin in S. uberis.
- The lnu(D) gene encodes a 164-amino-acid protein homologous to known lincosamide nucleotidyltransferases.
- The Lnu(D) enzyme was shown to inactivate lincomycin and clindamycin via adenylylation in the presence of ATP and MgCl2.
- A conserved domain was identified in Lnu(D) and other related nucleotidyltransferases.
Conclusions:
- The lnu(D) gene is responsible for lincomycin and clindamycin resistance in the studied S. uberis strain.
- The Lnu(D) enzyme confers resistance through antibiotic adenylylation, a mechanism previously observed for other lincosamide resistance genes.
- This discovery contributes to the understanding of antibiotic resistance mechanisms in Gram-positive bacteria and has implications for veterinary antibiotic use.
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