Typing of mecD Islands in Genetically Diverse Methicillin-Resistant Macrococcus caseolyticus Strains from Cattle

Abstract

Macrococcus caseolyticus belongs to the normal bacterial flora of dairy cows and does not usually cause disease. However, methicillin-resistant M. caseolyticus strains were isolated from bovine mastitis milk. These bacteria had acquired a chromosomal island (McRImecD-1 or McRImecD-2) carrying the methicillin resistance gene mecD. To gain insight into the distribution of McRImecD types in M. caseolyticus from cattle, 33 mecD-containing strains from Switzerland were characterized using molecular techniques, including multilocus sequence typing, antibiotic resistance gene identification, and PCR-based McRImecD typing. In addition, the same genetic features were analyzed in 27 mecD-containing M. caseolyticus strains isolated from bovine bulk milk in England/Wales using publicly available whole-genome sequences. The 60 strains belonged to 24 different sequence types (STs), with strains belonging to ST5, ST6, ST21, and ST26 observed in both Switzerland and England/Wales. McRImecD-1 was found in different STs from Switzerland (n = 19) and England/Wales (n = 4). McRImecD-2 was only found in 7 strains from Switzerland, all of which belonged to ST6. A novel island, McRImecD-3, which contains a complete mecD operon (mecD-mecR1m-mecIm [where the subscript m indicates Macrococcus]) combined with the left part of McRImecD-2 and the right part of McRImecD-1, was found in heterogeneous STs from both collections (Switzerland, n = 7; England/Wales, n = 21). Two strains from England/Wales carried a truncated McRImecD-3. Phylogenetic analyses revealed no clustering of strains according to geographical origin or carriage of McRImecD-1 and McRImecD-3. Circular excisions were also detected for McRImecD-1 and McRImecD-3 by PCR. The analyses indicate that these islands are mobile and may spread by horizontal gene transfer between genetically diverse M. caseolyticus strains. IMPORTANCE Since its first description in 2017, the methicillin resistance gene mecD has been detected in M. caseolyticus strains from different cattle sources and countries. Our study provides new insights into the molecular diversity of mecD-carrying M. caseolyticus strains by using two approaches to characterize mecD elements: (i) multiplex PCR for molecular typing of McRImecD and (ii) read mapping against reference sequences to identify McRImecD types in silico. In combination with multilocus sequence typing, this approach can be used for molecular characterization and surveillance of M. caseolyticus carrying mecD.

The Novel Macrolide Resistance Genes mef (D), msr (F), and msr (H) Are Present on Resistance Islands in Macrococcus canis, Macrococcus caseolyticus, and Staphylococcus aureus

“…Mobility of McRI msr . The presence of an integrase gene (int) related to that of McRI mecD and intact flanking att sites suggests that McRI msr could also be mobilized by an Int-catalyzed site-specific recombination reaction as observed for mecD elements (7,10,13). To determine whether McRI msr was able to excise itself, the genomic DNA of Epi0076A was analyzed for the presence of circular forms.…”

“…Similarly, the msr(H) gene of M. canis KM0218 was also associated with an McRI msr -like structure integrated at the rpsI locus. The 3= end of the rpsI gene, a highly conserved locus in Staphylococcaceae, has already been shown to hold integrated elements carrying an int gene or small accessory islands without an obvious mobilization function (4,7,10,13). The att-flanked segments found in M. canis Epi0076A and SD607 suggests that the site-specific int gene is active in accumulating accessory DNA and diversifying the rpsI locus.…”

“…McRI mecD ) in methicillin-resistant M. caseolyticus strains(7,13). Similar to McRI mecD , the mef(D)-msr(F)-containing element in Epi0076A and SD607 was delimited at both sides by characteristic attachment (att) sites of 61 bp and carried a related site-specific integrase gene (int) of the tyrosine recombinase family preceded by its regulator's intR and xis(Fig.…”

Polymicrobial Necrotizing Fasciitis in a Dog: The Involvement of Macrococcus caseolyticus, Proteus mirabilis, and Escherichia coli

“…Escherichia coli , a gram-negative facultative anaerobic bacterium, is mainly a gut microbe [ 11 ]. M. caseolyticus is an aerobic gram-positive bacterium and has been isolated from different mammals, even from milk and meat products [ 12 , 13 ]. M. caseolyticus belongs to the normal skin flora of most domestic animals, methicillin-resistant, and causes mastitis in cows [ 13 , 14 ].…”

“…M. caseolyticus is an aerobic gram-positive bacterium and has been isolated from different mammals, even from milk and meat products [ 12 , 13 ]. M. caseolyticus belongs to the normal skin flora of most domestic animals, methicillin-resistant, and causes mastitis in cows [ 13 , 14 ]. Until now, there is no report of E. coli involvement in NF cases in dogs.…”