The smr gene resides on a novel plasmid pSP187 identified in a Staphylococcus pasteuri isolate recovered from unpasteurized milk.
This work describes a novel plasmid pSP187 (5550 bp) carrying the small multidrug resistance determinant smr encoding resistance to quaternary ammonium compounds (QACs). pSP187 was identified in a Staphylococcus pasteuri isolate recovered from bulk milk in a dairy cattle herd in Norway. Sequence analysis revealed 6 putative ORFs in addition to the smr gene within a cassette with identical genetic organization to that found in the pSK41-like Staphylococcus aureus plasmid pTZ22. A protein homology search suggested the gene product of ORF7 to be a putative replication initiation protein, while ORF2 was predicted to encode a protein homologous to members of FtsK/SpoIIIE cell division-DNA segregation protein families. Sequence similarities to some initiator proteins of rolling circle replicons (RCR) indicated that pSP187 uses a RCR mode of replication, supported by the detection of intermediate ssDNA using S1 nuclease treatment and hybridization analysis. Interestingly, a 30-bp sequence found upstream from ORF7 showed high similarity to other dyad symmetry motifs proposed as putative double-strand origins of replication in the plasmids pGI3 (Bacillus thuringiensis), pSTK1 (Bacillus stearothermophilus), and pER1-2 (Streptococcus thermophilus).


CONCLUSIONS
The novel smr-containing plasmid pSP187 is the first member of RCR group VI to be identified in a Staphylococcus sp.
Bjorland
Jostein
J
Department of Production Animal Clinical Sciences, Norwegian School of Veterinary Science, P.O. Box 8146 Dep, N-0033 Oslo, Norway. jostein.bjorland@veths.no
Bratlie
Marit S
MS
Steinum
Terje
T
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002417:Cattle; D016384:Consensus Sequence; D017124:Conserved Sequence; D018432:Drug Resistance, Multiple / Q000235:genetics*; D005798:Genes, Bacterial; D008826:Microbial Sensitivity Tests; D008892:Milk / Q000382:microbiology*; D008969:Molecular Sequence Data; D010957:Plasmids; D015183:Restriction Mapping; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D013210:Staphylococcus / Q000235:genetics / Q000302:isolation & purification*