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40700.9892Molecular cloning and characterization of two lincomycin-resistance genes, lmrA and lmrB, from Streptomyces lincolnensis 78-11. Two different lincomycin-resistance determinants (lmrA and lmrB) from Streptomyces lincolnensis 78-11 were cloned in Streptomyces lividans 66 TK23. The gene lmrA was localized on a 2.16 kb fragment, the determined nucleotide sequence of which encoded a single open reading frame 1446 bp long. Analysis of the deduced amino acid sequence suggested the presence of 12 membrane-spanning domains and showed significant similarities to the methylenomycin-resistance protein (Mmr) from Streptomyces coelicolor, the QacA protein from Staphylococcus aureus, and several tetracycline-resistance proteins from both Gram-positive and Gram-negative bacteria, as well as to some sugar-transport proteins from Escherichia coli. The lmrB gene was actively expressed from a 2.7 kb fragment. An open reading frame of 837 bp could be localized which encoded a protein that was significantly similar to 23S rRNA adenine(2058)-N-methyltransferases conferring macrolide-lincosamide-streptogramin resistance. LmrB also had putative rRNA methyltransferase activity since lincomycin resistance of ribosomes was induced in lmrB-containing strains. Surprisingly, both enzymes, LmrA and LmrB, had a substrate specificity restricted to lincomycin and did not cause resistance to other lincosamides such as celesticetin and clindamycin, or to macrolides.19921328813
544010.9890Molecular structure and evolution of the conjugative multiresistance plasmid pRE25 of Enterococcus faecalis isolated from a raw-fermented sausage. Plasmid pRE25 from Enterococcus faecalis transfers resistances against kanamycin, neomycin, streptomycin, clindamycin, lincomycin, azithromycin, clarithromycin, erythromycin, roxithromycin, tylosin, chloramphenicol, and nourseothricin sulfate by conjugation in vitro to E. faecalis JH2-2, Lactococcus lactis Bu2, and Listeria innocua L19. Its nucleotide sequence of 50237 base pairs represents the largest, fully sequenced conjugative multiresistance plasmid of enterococci (Plasmid 46 (2001) 170). The gene for chloramphenicol resistance (cat) was identified as an acetyltransferase identical to the one of plasmid pIP501 of Streptococcus agalactiae. Erythromycin resistance is due to a 23S ribosomal RNA methyl transferase, again as found in pIP501 (ermB). The aminoglycoside resistance genes are packed in tandem as in transposon Tn5405 of Staphylococcus aureus: an aminoglycoside 6-adenyltransferase, a streptothricin acetyl transferase, and an aminoglycoside phosphotransferase.). Identical resistance genes are known from pathogens like Streptococcus pyogenes, S. agalactiae, S. aureus, Campylobacter coli, Clostridium perfringens, and Clostridium difficile. pRE25 is composed of a 30.5-kbp segment almost identical to pIP501. Of the 15 genes involved in conjugative transfer, 10 codes for putative transmembrane proteins (e.g. trsB, traC, trsF, trsJ, and trsL). The enterococcal part is joined into the pIP501 part by insertion elements IS1216V of E. faecium Tn1545 (three copies), and homologs of IS1062 (E. faecalis) and IS1485 (E. faecium). pRE25 demonstrates that enterococci from fermented food do participate in the molecular communication between Gram-positive and Gram-negative bacteria of the human and animal microflora.200314597005
81920.9886Trimethoprim resistance transposon Tn4003 from Staphylococcus aureus encodes genes for a dihydrofolate reductase and thymidylate synthetase flanked by three copies of IS257. Trimethoprim resistance mediated by the Staphylococcus aureus multi-resistance plasmid pSK1 is encoded by a structure with characteristics of a composite transposon which we have designated Tn4003. Nucleotide sequence analysis of Tn4003 revealed it to be 4717 bp in length and to contain three copies of the insertion element IS257 (789-790 bp), the outside two of which are flanked by directly repeated 8-bp target sequences. IS257 has imperfect terminal inverted repeats of 27-28 bp and encodes for a putative transposase with two potential alpha-helix-turn-alpha-helix DNA recognition motifs. IS257 shares sequence similarities with members of the IS15 family of insertion sequences from Gram-negative bacteria and with ISS1 from Streptococcus lactis. The central region of the transposon contains the dfrA gene that specifies the S1 dihydrofolate reductase (DHFR) responsible for trimethoprim resistance. The S1 enzyme shows sequence homology with type I and V trimethoprim-resistant DHFRs from Gram-negative bacteria and with chromosomally encoded DHFRs from Gram-positive and Gram-negative bacteria. 5' to dfrA is a thymidylate synthetase gene, designated thyE.19892548057
522230.9885Resistance to macrolides by ribosomal mutation in clinical isolates of Turicella otitidis. The genetic basis of erythromycin resistance in Turicella otitidis, a coryneform bacteria associated with otitis, was studied in five macrolide-resistant clinical isolates. Macrolide resistance genes were searched for by polymerase chain reaction (PCR). Genes for domain V of 23S rRNA (rrl) as well as rplD (L4 protein) and rplV (L22 protein) genes were characterised, amplified by PCR from total genomic DNA and sequenced. In the resistant isolates, cross-resistance to macrolides and clindamycin was associated with mutations at positions 2058 and/or 2059 (Escherichia coli numbering). Three isolates displayed A2058 mutations, one isolate had an A2059G mutation whereas another one contained mutations at positions 2058 and 2059. Southern blot experiments revealed that T. otitidis had three copies of the rrl gene. In conclusion, resistance to macrolides in T. otitidis is due, at least in part, to mutations in the rrl gene.200919414240
522840.9885Mycobacterium bolletii respiratory infections. Contrary to other species in the Mycobacterium chelonae-abscessus complex, we reidentified M. bolletii strains isolated from 4 respiratory patients and found these strains to be uniformly resistant to clarithromycin. No mutations previously associated with macrolide resistance in bacteria were detected in either the 23S rDNA or the genes encoding riboproteins L4 and L22.200919193279
522150.9881Molecular cloning of the DNA gyrase genes from Methylovorus sp. strain SS1 and the mechanism of intrinsic quinolone resistance in methylotrophic bacteria. The genes encoding the DNA gyrase A (GyrA) and B subunits (GyrB) of Methylovorus sp. strain SS1 were cloned and sequenced. gyrA and gyrB coded for proteins of 846 and 799 amino acids with calculated molecular weights of 94,328 and 88,714, respectively, and complemented Escherichia coli gyrA and gyrB temperature sensitive (ts) mutants. To analyze the role of type II topoisomerases in the intrinsic quinolone resistance of methylotrophic bacteria, the sequences of the quinolone resistance-determining regions (QRDRs) in the A subunit of DNA gyrase and the C subunit (ParC) of topoisomerase IV (Topo IV) of Methylovorus sp. strain SS1, Methylobacterium extorquens AM1 NCIB 9133, Methylobacillus sp, strain SK1 DSM 8269, and Methylophilus methylotrophus NCIB 10515 were determined. The deduced amino acid sequences of the QRDRs of the ParCs in the four methylotrophic bacteria were identical to that of E. coli ParC. The sequences of the QRDR in GyrA were also identical to those in E. coli GyrA except for the amino acids at positions 83, 87, or 95. The Ser83 to Thr substitution in Methylovorus sp. strain SS1, and the Ser83 to Leu and Asp87 to Asn substitutions in the three other methylotrophs, agreed well with the minimal inhibitory concentrations of quinolones in the four bacteria, suggesting that these residues play a role in the intrinsic susceptibility of methylotrophic bacteria to quinolones.200516404155
522760.9880Mutation at the position 2058 of the 23S rRNA as a cause of macrolide resistance in Streptococcus pyogenes. BACKGROUND: In streptococci, three macrolide resistance determinants (erm(B), erm(TR) and mef(A)) have been found. In addition, certain mutations at the ribosomal 23S RNA can cause resistance to macrolides. Mutation at the position 2058 of the 23S rRNA of the Streptococcus pyogenes as a cause of macrolide resistance has not been described before. METHODS: Antibiotic resistance determinations for the clinical S. pyogenes strain ni4277 were done using the agar dilution technique. Macrolide resistance mechanisms were studied by PCR and sequencing. All six rRNA operons were amplified using operon-specific PCR. The PCR products were partially sequenced in order to resolve the sequences of different 23S rRNA genes. RESULTS: One clinical isolate of S. pyogenes carrying an adenine to guanine mutation at the position 2058 of the 23S rRNA in five of the six possible rRNA genes but having no other known macrolide resistance determinants is described. The strain was highly resistant to macrolides and azalides, having erythromycin and azithromycin MICs > 256 microgram/ml. It was resistant to lincosamides (clindamycin MIC 16 microgram/ml) and also MIC values for ketolides were clearly elevated. The MIC for telithromycin was 16 microgram/ml. CONCLUSION: In this clinical S. pyogenes strain, a mutation at the position 2058 was detected. No other macrolide resistance-causing determinants were detected. This mutation is known to cause macrolide resistance in other bacteria. We can conclude that this mutation was the most probable cause of macrolide, lincosamide and ketolide resistance in this strain.200415128458
11070.9879Resistance to the macrolide antibiotic tylosin is conferred by single methylations at 23S rRNA nucleotides G748 and A2058 acting in synergy. The macrolide antibiotic tylosin has been used extensively in veterinary medicine and exerts potent antimicrobial activity against Gram-positive bacteria. Tylosin-synthesizing strains of the Gram-positive bacterium Streptomyces fradiae protect themselves from their own product by differential expression of four resistance determinants, tlrA, tlrB, tlrC, and tlrD. The tlrB and tlrD genes encode methyltransferases that add single methyl groups at 23S rRNA nucleotides G748 and A2058, respectively. Here we show that methylation by neither TlrB nor TlrD is sufficient on its own to give tylosin resistance, and resistance is conferred by the G748 and A2058 methylations acting together in synergy. This synergistic mechanism of resistance is specific for the macrolides tylosin and mycinamycin that possess sugars extending from the 5- and 14-positions of the macrolactone ring and is not observed for macrolides, such as carbomycin, spiramycin, and erythromycin, that have different constellations of sugars. The manner in which the G748 and A2058 methylations coincide with the glycosylation patterns of tylosin and mycinamycin reflects unambiguously how these macrolides fit into their binding site within the bacterial 50S ribosomal subunit.200212417742
522980.9876Paradoxical High-Level Spiramycin Resistance and Erythromycin Susceptibility due to 23S rRNA Mutation in Streptococcus constellatus. Objectives: The aim of the study was to characterize phenotypically and genotypically an uncommon mechanism of resistance to macrolides, lincosamides, and streptogramins (MLS) in a Streptococcus milleri group clinical isolate. Materials and Methods: The isolate UCN96 was recovered from an osteoradionecrosis wound, and was identified using the matrix assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry and the partial sequencing of the sodA gene. Antimicrobial susceptibility testing were carried out by the disk diffusion method and minimal inhibitory concentrations (MICs) were determined by the broth microdilution technique. PCR screening was performed for MLS resistance genes described in Gram-positive bacteria. Specific mutations in the ribosomal proteins L3-, L4-, and L22-encoding genes were also screened and those in domain V of the 23S rRNA gene (rrl). The number of mutated copies of the rrl gene was determined using amplification-refractory mutation system quantitative-polymerase chain reaction (qPCR) analysis. Results: The clinical isolate UCN96 was unambiguously identified as Streptococcus constellatus. It was susceptible to all macrolides and lincosamides (ML) antibiotics except spiramycin (MIC >256 mg/L) while it was also resistant to streptogramins. Screening for all acquired resistance genes was negative and no mutation was found in genes coding for L3, L4, and L22 ribosomal proteins. Of interest, a single mutation, A2062C (according to Escherichia coli numbering), was detected in the domain V of 23S rRNA. Conclusion: Mutations at the position 2062 of 23S rRNA have been detected once in Streptococcus pneumoniae, and not yet in other Streptococcus spp. This mechanism is very likely uncommon in Gram-positive bacteria because different copies of 23S rRNA operons should be mutated for development of such a resistance pattern.202032031922
301390.9875Nucleotide sequence and organization of the multiresistance plasmid pSCFS1 from Staphylococcus sciuri. OBJECTIVES: The multiresistance plasmid pSCFS1 from Staphylococcus sciuri was sequenced completely and analysed with regard to its gene organization and the putative role of a novel ABC transporter in antimicrobial resistance. METHODS: Plasmid pSCFS1 was transformed into Staphylococcus aureus RN4220, overlapping restriction fragments were cloned into Escherichia coli plasmid vectors and sequenced. For further analysis of the ABC transporter, a approximately 3 kb EcoRV-HpaI fragment was cloned into the staphylococcal plasmid pT181MCS and the respective S. aureus RN4220 transformants were subjected to MIC determination. RESULTS: A total of 14 ORFs coding for proteins of >100 amino acids were detected within the 17 108 bp sequence of pSCFS1. Five of them showed similarity to recombination/mobilization genes while another two were similar to plasmid replication genes. In addition to the previously described genes cfr for chloramphenicol/florfenicol resistance and erm(33) for inducible resistance to macrolide-lincosamide-streptogramin B resistance, a Tn554-like spectinomycin resistance gene and Tn554-related transposase genes were identified. Moreover, a novel ABC transporter was detected and shown to mediate low-level lincosamide resistance. CONCLUSION: Plasmid pSCFS1 is composed of various parts which show similarity to sequences known to occur on plasmids or transposons of Gram-positive, but also Gram-negative bacteria. It is likely that pSCFS1 represents the result of inter-plasmid recombination events also involving the truncation of a Tn554-like transposon.200415471995
402100.9875The cme gene of Clostridium difficile confers multidrug resistance in Enterococcus faecalis. Antibiotic resistance in C. difficile by efflux has been previously suggested. The genome of C. difficile 630 was screened for sequences encoding putative proteins homologous to NorA from Staphylococcus aureus. Four ORFs homologous to efflux genes were cloned into the pAT79 shuttle vector under the control of transcription and translation signals of Gram-positive bacteria and expressed in Enterococcus faecalis JH2-2 and S. aureus RN4220. One of these sequences, designated cme conferred resistance to ethidium bromide, safranin O, and erythromycin in E. faecalis. The three other ORFs did not confer detectable resistance in both bacteria.200415336408
5224110.9875The novel macrolide resistance genes mef(F) and msr(G) are located on a plasmid in Macrococcus canis and a transposon in Macrococcus caseolyticus. OBJECTIVES: To analyse macrolide resistance in a Macrococcus canis strain isolated from a dog with an ear infection, and determine whether the resistance mechanism is also present in other bacteria, and associated with mobile genetic elements. METHODS: The whole genome of M. canis Epi0082 was sequenced using PacBio and Illumina technologies. Novel macrolide resistance determinants were identified through bioinformatic analysis, and functionality was demonstrated by expression in Staphylococcus aureus. Mobile genetic elements containing the novel genes were analysed in silico for strain Epi0082 as well as in other bacterial strains deposited in GenBank. RESULTS: M. canis Epi0082 contained a 3212 bp operon with the novel macrolide resistance genes mef(F) and msr(G) encoding a efflux protein and an ABC-F ribosomal protection protein, respectively. Cloning in S. aureus confirmed that both genes individually confer resistance to the 14- and 15-membered ring macrolides erythromycin and azithromycin, but not the 16-membered ring macrolide tylosin. A reduced susceptibility to the streptogramin B pristinamycin IA was additionally observed when msr(G) was expressed in S. aureus under erythromycin induction. Epi0082 carried the mef(F)-msr(G) operon together with the chloramphenicol resistance gene fexB in a novel 39 302 bp plasmid pMiCAN82a. The mef(F)-msr(G) operon was also found in macrolide-resistant Macrococcus caseolyticus strains in the GenBank database, but was situated in the chromosome as part of a novel 13 820 bp or 13 894 bp transposon Tn6776. CONCLUSIONS: The identification of mef(F) and msr(G) on different mobile genetic elements in Macrococcus species indicates that these genes hold potential for further dissemination of resistance to the clinically important macrolides in the bacterial population.202133118027
111120.9875The tylosin resistance gene tlrB of Streptomyces fradiae encodes a methyltransferase that targets G748 in 23S rRNA. tlrB is one of four resistance genes encoded in the operon for biosynthesis of the macrolide tylosin in antibiotic-producing strains of Streptomyces fradiae. Introduction of tlrB into Streptomyces lividans similarly confers tylosin resistance. Biochemical analysis of the rRNA from the two Streptomyces species indicates that in vivo TlrB modifies nucleotide G748 within helix 35 of 23S rRNA. Purified recombinant TlrB retains its activity and specificity in vitro and modifies G748 in 23S rRNA as well as in a 74 nucleotide RNA containing helix 35 and surrounding structures. Modification is dependent on the presence of the methyl group donor, S-adenosyl methionine. Analysis of the 74-mer RNA substrate by biochemical and mass spectrometric methods shows that TlrB adds a single methyl group to the base of G748. Homologues of TlrB in other bacteria have been revealed through database searches, indicating that TlrB is the first member to be described in a new subclass of rRNA methyltransferases that are implicated in macrolide drug resistance.200010972803
406130.9875Naturally occurring macrolide-lincosamide-streptogramin B resistance in Bacillus licheniformis. Resistance to the macrolide-lincosamide-streptogramin B (MLS) group of antibiotics is widespread and of clinical importance. B. Weisblum and his coworkers have demonstrated that this resistance is associated with methylation of the 23S ribosomal ribonucleic acid of the large ribosomal subunit which results in a diminished affinity of this organelle for these antibiotics (Lai et al, J. Mol. Biol. 74:67-72, 1973). We report that 10 of 15 natural isolates of Bacillus licheniformis, a common soil organism, are resistant to the MLS antibiotics. The properties of this resistance (high level of tolerance for erythromycin, broad cross-resistance spectrum, and inducibility) suggest that resistance is conferred as described above. The resistance determinant from one of these strains was cloned onto a B. subtilis plasmid vector, and the resulting hybrid plasmid (pBD90) was used to prepare radioactive probe deoxyribonucleic acid for hybridization studies. All of the resistance B. licheniformis strains studied exhibited homology with the pBD90 insert. Plasmid pBD90 showed no homology to the following staphylococcal and streptococcal MLS-resistance plasmids: pE194, pE5, pAM77, pI258. Plasmids pE194 and pE5, on the other hand, carry homologous MLS genes but showed no detectable homology to one another in their replication genes. pBD90 specified a 35,000-dalton erythromycin-inducible protein, detectable in minicells, which therefore appears different from the 29,000-dalton inducible resistance protein specified by pE194. We conclude that there are at least three distinct MLS resistance determinants to be found among gram-positive bacteria.19816780509
5407140.9874Resistance mechanisms and tedizolid susceptibility in clinical isolates of linezolid-resistant bacteria in Japan. OBJECTIVES: Studies combining linezolid resistance mechanisms and tedizolid susceptibility in linezolid-resistant clinical isolates are scarce. This study investigated the linezolid resistance mechanisms and tedizolid susceptibility of linezolid-resistant strains isolated clinically in Japan. METHODS: We analysed 25 linezolid-resistant strains of Enterococcus faecium and Enterococcus faecalis isolated from Japanese hospitals between 2015 and 2021. MICs of linezolid and tedizolid were determined using the agar plate dilution method. Each 23S rRNA copy was amplified by PCR, sequenced and analysed for mutations. The linezolid resistance genes cfr, poxtA, optrA, fexA and fexB were also detected by PCR. RESULTS: Drug susceptibility tests revealed that five linezolid-resistant E. faecium isolates had low (≤1 mg/L) tedizolid MICs. Resistance mechanisms included the G2576T mutation in 23S rRNA, the T2504A mutation and the resistance genes optrA, fexA and fexB. The T2504A mutation was identified in one E. faecium isolate, which exhibited linezolid and tedizolid MICs of 64 and 32 mg/L, respectively. CONCLUSIONS: Some linezolid-resistant isolates demonstrated low (≤1 mg/L) tedizolid MICs. To determine whether tedizolid susceptibility testing should be performed on linezolid-resistant isolates, more linezolid-resistant isolates should be collected and tested for tedizolid MICs. Tedizolid MICs were 2-3 doubling dilutions lower than linezolid MICs. The results of this study suggest that future research should investigate whether the T2504A mutation contributes to tedizolid resistance. To our knowledge, this is the first study to report tedizolid susceptibility in E. faecium with the T2504A mutation and in isolate harbouring this mutation.202540463587
403150.9873Nucleotide sequence and expression of the mercurial-resistance operon from Staphylococcus aureus plasmid pI258. The mercurial-resistance determinant from Staphylococcus aureus plasmid pI258 is located on a 6.4-kilobase-pair Bgl II fragment. The determinant was cloned into both Bacillus subtilis and Escherichia coli. Mercury resistance was found only in B. subtilis. The 6404-base-pair DNA sequence of the Bgl II fragment was determined. The mer DNA sequence includes seven open reading frames, two of which have been identified by homology with the merA (mercuric reductase) and merB (organomercurial lyase) genes from the mercurial-resistance determinants of Gram-negative bacteria. Whereas 40% of the amino acid residues overall were identical between the pI258 merA polypeptide product and mercuric reductases from Gram-negative bacteria, the percentage identity in the active-site positions and those thought to be involved in NADPH and FAD contacts was above 90%. The 216 amino acid organomercurial lyase sequence was 39% identical with that from a Serratia plasmid, with higher conservation in the middle of the sequences and lower homologies at the amino and carboxyl termini. The remaining five open reading frames in the pI258 mer sequence have no significant homologies with the genes from previously sequenced Gram-negative mer operons.19873037534
5223160.9873Cloned ermTR Gene Confers Low Level Erythromycin but High Level Clindamycin Resistance in Streptococcus pyogenes NZ131. Objectives: The most common macrolide resistance mechanisms in streptococci are the presence of methylase encoding genes ermB and ermTR or the presence of efflux encoded by mef genes. In the present study we aimed to show the effects of the ermTR gene under isogenic conditions on the activities of macrolides and lincosamides in streptococci. Materials and Methods: Total DNA was extracted from Streptococcus pyogenes C1, and the ermTR gene was amplified with or without the regulatory region using modified primer with insertion of restriction sites to clone in to pUC18. Transformants were selected after electroporation of Escherichia coli DB10. The recombinant plasmids were purified and merged to pJIM2246 to transform Gram positive bacteria. Recombinant pJIM2246 plasmids with the ermTR gene were then introduced into S. pyogenes NZ131 by electroporation. Results: After transformation with ermTR without regulatory region the minimal inhibitory concentration (MIC) for erythromycin and clindamycin increased from ≤0.06 to ≤0.06 to 8 and >128 mg/L, respectively. Induction with erythromycin affected the MICs for clindamycin of S. pyogenes transformed with ermTR with the regulatory region. Double disk testing showed that induction with erythromycin and azithromycin for the S. pyogenes transformed with ermTR, and regulatory regions decreased the clindamycin inhibition zone but not telithromycin. The ermTR gene in isogenic conditions confers low level resistance to erythromycin and high level resistance to clindamycin. Conclusion: The different induction and resistance profiles of ermTR compared to other erm genes suggest that the methylation of ErmTR may be different than well studied methylases.202031971866
5220170.9870The first report of the vanC₁ gene in Enterococcus faecium isolated from a human clinical specimen. The vanC₁ gene, which is chromosomally located, confers resistance to vancomycin and serves as a species marker for Enterococcus gallinarum. Enterococcus faecium TJ4031 was isolated from a blood culture and harbours the vanC₁gene. Polymerase chain reaction (PCR) assays were performed to detect vanXYc and vanTc genes. Only the vanXYc gene was found in the E. faecium TJ4031 isolate. The minimum inhibitory concentrations of vancomycin and teicoplanin were 2 µg/mL and 1 µg/mL, respectively. Real-time reverse transcription-PCR results revealed that the vanC₁ and vanXYc genes were not expressed. Pulsed-field gel electrophoresis and southern hybridisation results showed that the vanC₁ gene was encoded in the chromosome. E. faecalis isolated from animals has been reported to harbour vanC₁gene. However, this study is the first to report the presence of the vanC₁gene in E. faecium of human origin. Additionally, our research showed the vanC₁gene cannot serve as a species-specific gene of E. gallinarum and that it is able to be transferred between bacteria. Although the resistance marker is not expressed in the strain, our results showed that E. faecium could acquire the vanC₁gene from different species.201425317698
404180.9870Plasmid-borne cadmium resistance genes in Listeria monocytogenes are similar to cadA and cadC of Staphylococcus aureus and are induced by cadmium. pLm74 is the smallest known plasmid in Listeria monocytogenes. It confers resistance to the toxic divalent cation cadmium. It contains a 3.1-kb EcoRI fragment which hybridizes with the cadAC genes of plasmid pI258 of Staphylococcus aureus. When introduced into cadmium-sensitive L. monocytogenes or Bacillus subtilis strains, this fragment conferred cadmium resistance. The DNA sequence of the 3.1-kb EcoRI fragment contains two open reading frames, cadA and cadC. The deduced amino acid sequences are similar to those of the cad operon of plasmid pI258 of S. aureus, known to prevent accumulation of Cd2+ in the bacteria by an ATPase efflux mechanism. The cadmium resistance determinant of L. monocytogenes does not confer zinc resistance, in contrast to the cadAC determinant of S. aureus, suggesting that the two resistance mechanisms are slightly different. Slot blot DNA-RNA hybridization analysis showed cadmium-inducible synthesis of L. monocytogenes cadAC RNA.19948188605
5225190.9870Two genes involved in clindamycin resistance of Bacillus licheniformis and Bacillus paralicheniformis identified by comparative genomic analysis. We evaluated the minimum inhibitory concentrations of clindamycin and erythromycin toward 98 Bacillus licheniformis strains isolated from several types of fermented soybean foods manufactured in several districts of Korea. First, based on recent taxonomic standards for bacteria, the 98 strains were separated into 74 B. licheniformis strains and 24 B. paralicheniformis strains. Both species exhibited profiles of erythromycin resistance as an acquired characteristic. B. licheniformis strains exhibited acquired clindamycin resistance, while B. paralicheniformis strains showed unimodal clindamycin resistance, indicating an intrinsic characteristic. Comparative genomic analysis of five strains showing three different patterns of clindamycin and erythromycin resistance identified 23S rRNA (adenine 2058-N6)-dimethyltransferase gene ermC and spermidine acetyltransferase gene speG as candidates potentially involved in clindamycin resistance. Functional analysis of these genes using B. subtilis as a host showed that ermC contributes to cross-resistance to clindamycin and erythromycin, and speG confers resistance to clindamycin. ermC is located in the chromosomes of strains showing clindamycin and erythromycin resistance and no transposable element was identified in its flanking regions. The acquisition of ermC might be attributable to a homologous recombination. speG was identified in not only the five genome-analyzed strains but also eight strains randomly selected from the 98 test strains, and deletions in the structural gene or putative promoter region caused clindamycin sensitivity, which supports the finding that the clindamycin resistance of Bacillus species is an intrinsic property.202032271828