streptogramin-a and Staphylococcal-Infections

Novexel is developing the novel, orally active, semisynthetic streptogramin NXL-103, which has potential therapeutic application in the treatment of community-acquired pneumonia, community- or hospital-acquired MRSA, vancomycin-resistant enterococcus, and acute bacterial skin and soft tissue infections. NXL-103 is a combination of streptogramin A:streptogramin B components, initially developed in a 70:30 dose ratio. In multiple in vitro studies, NXL-103 demonstrated potent activity against different types of bacteria, such as Staphylococcus aureus (including MRSA), Streptococcus pneumoniae, Streptococcus pyogenes, Enterococcus faecium, Enterococcus faecalis, Haemophilus influenzae and Haemophilus parainfluenzae. NXL-103 was not affected by the resistance profiles of bacteria against other commonly used antibiotics. In phase I clinical trials, NXL-103 achieved bactericidal levels in plasma and was generally well tolerated, with side effects primarily on the gastrointestinal system. The first phase II trial conducted to evaluate the efficacy of NXL-103 against community-acquired pneumonia revealed that the compound was comparable with amoxicillin. NXL-103 has promise to become an important agent in the treatment of community-acquired pneumonia and complex skin and soft tissue infections, pending further development.

Topics: Animals; Anti-Bacterial Agents; Bacterial Infections; Clinical Trials as Topic; Community-Acquired Infections; Cross Infection; Drug Combinations; Humans; Methicillin-Resistant Staphylococcus aureus; Pneumonia, Bacterial; Staphylococcal Infections; Streptogramin A; Streptogramin B

Topics: Animals; Anti-Bacterial Agents; Genomics; Humans; Lincosamides; Livestock; Methicillin-Resistant Staphylococcus aureus; Phylogeny; Pleuromutilins; Staphylococcal Infections; Streptogramin A; Swine

The aim of this study was to investigate the genetic basis of combined pleuromutilin-lincosamide-streptogramin A resistance in 26 unrelated methicillin-resistant Staphylococcus aureus (MRSA) and coagulase-negative staphylococci (CoNS) from dairy cows suffering from mastitis. The 26 pleuromutilin-resistant staphylococcal isolates were screened for the presence of the genes vga(A), vga(B), vga(C), vga(E), vga(E) variant, sal(A), vmlR, cfr, lsa(A), lsa(B), lsa(C), and lsa(E) by PCR. None of the 26 isolates carried the genes vga(B), vga(C), vga(E), vga(E) variant, vmlR, cfr, lsa(A), lsa(B), or lsa(C). Two Staphylococcus haemolyticus and single Staphylococcus xylosus, Staphylococcus lentus, and Staphylococcus hominis were vga(A)-positive. Twelve S. aureus, two Staphylococcus warneri, as well as single S. lentus and S. xylosus carried the lsa(E) gene. Moreover, single S. aureus, S. haemolyticus, S. xylosus, and Staphylococcus epidermidis were positive for both genes, vga(A) and lsa(E). The sal(A) gene was found in a single Staphylococcus sciuri. All ABC transporter genes were located in the chromosomal DNA, except for a plasmid-borne vga(A) gene in the S. epidermidis isolate. The genetic environment of the lsa(E)-positive isolates was analyzed using previously described PCR assays. Except for the S. warneri and S. xylosus, all lsa(E)-positive isolates harbored a part of the previously described enterococcal multiresistance gene cluster. This is the first report of the novel lsa(E) gene in the aforementioned bovine CoNS species. This is also the first identification of the sal(A) gene in a S. sciuri from a case of bovine mastitis. Moreover, the sal(A) gene was shown to also confer pleuromutilin resistance.

Topics: Animals; Anti-Bacterial Agents; ATP-Binding Cassette Transporters; Cattle; Coagulase; Diterpenes; Drug Resistance, Multiple, Bacterial; Female; Lincosamides; Mastitis, Bovine; Methicillin; Methicillin-Resistant Staphylococcus aureus; Microbial Sensitivity Tests; Pleuromutilins; Polycyclic Compounds; Staphylococcal Infections; Staphylococcus; Staphylococcus epidermidis; Staphylococcus haemolyticus; Staphylococcus hominis; Streptogramin A; Streptogramins

Natural resistance to lincosamides and streptogramins A (LSA), which is a species characteristic of Bacillus subtilis and Enterococcus faecalis, has never been documented in the Staphylococcus genus. We investigate here the molecular basis of the LSA phenotype exhibited by seven reference strains of Staphylococcus sciuri, including the type strains of the three described subspecies. By whole-genome sequencing of strain ATCC 29059, we identified a candidate gene that encodes an ATP-binding cassette protein similar to the Lsa and VmlR resistance determinants. Isolation and reverse transcription-quantitative PCR (qRT-PCR) expression studies confirmed that Sal(A) can confer a moderate resistance to lincosamides (8 times the MIC of lincomycin) and a high-level resistance to streptogramins A (64 times the MIC of pristinamycin II). The chromosomal location of sal(A) between two housekeeping genes of the staphylococcal core genome supports the gene's ancient origins and thus innate resistance to these antimicrobials within S. sciuri subspecies.

Topics: Amino Acid Sequence; Anti-Bacterial Agents; Bacterial Proteins; Chromosome Mapping; DNA, Bacterial; Drug Resistance, Multiple, Bacterial; Lincosamides; Microbial Sensitivity Tests; Molecular Sequence Data; Phenotype; Phylogeny; Sequence Alignment; Sequence Analysis, DNA; Staphylococcal Infections; Staphylococcus; Streptogramin A

To investigate the genetic basis of pleuromutilin resistance in porcine methicillin-resistant Staphylococcus aureus (MRSA) and to map the genetic environment of the identified plasmid-borne resistance gene.. Seventy porcine MRSA isolates, which exhibited high MICs of tiamulin, valnemulin and retapamulin, were investigated for pleuromutilin resistance genes and mutations. They were characterized by staphylococcal cassette chromosome mec (SCCmec) typing, spa typing and multilocus sequence typing (MLST). Plasmid DNA was extracted from the lsa(E)-positive strains and transferred to S. aureus RN4220 for selection of resistance plasmids. The plasmid-borne lsa(E) gene region was sequenced and 10 overlapping PCR assays for the analysis of the genetic environment of lsa(E) were developed.. All 70 MRSA isolates were ST9 (MLST)-t899 (spa)-IVa (SCCmec). Sixteen isolates carried the lsa(E) gene; all others were negative for known pleuromutilin resistance mechanisms. An lsa(E)-carrying plasmid of ∼41 kb was detected in a single isolate. Sequence analysis revealed that the lsa(E) gene was located in a multiresistance gene cluster, which showed partial homology to clusters identified in MRSA, methicillin-susceptible S. aureus (MSSA) and Enterococcus faecalis. PCR analysis of the remaining isolates revealed a partly deleted multiresistance gene cluster in 6/15 isolates and solely the lsa(E) gene without the known flanking regions in 9/15 isolates.. We identified the pleuromutilin-lincosamide-streptogramin A resistance gene lsa(E) in porcine MRSA isolates. The multiresistance gene cluster in which lsa(E) was located differed from the previously described ones found in human MRSA/MSSA or in E. faecalis. The location of lsa(E) on a multiresistance plasmid facilitates its persistence and dissemination.

Topics: Animals; Anti-Bacterial Agents; China; Cloning, Molecular; Diterpenes; DNA, Bacterial; Drug Resistance, Bacterial; Enterococcus faecalis; Lincosamides; Methicillin-Resistant Staphylococcus aureus; Microbial Sensitivity Tests; Multilocus Sequence Typing; Plasmids; Pleuromutilins; Polycyclic Compounds; Staphylococcal Infections; Streptogramin A; Swine; Swine Diseases; Transformation, Bacterial

Two clinical Staphylococcus aureus isolates were investigated due to their unusual antimicrobial susceptibility pattern, i.e. erythromycin-susceptible but clindamycin-resistant. These isolates harboured identical copies of a plasmid-borne vga(A)(LC) gene not previously described in S. aureus. The native plasmids carrying vga(A)(LC) were transferable to a susceptible laboratory strain of S. aureus in vitro, in which they conferred resistance patterns similar to the parent isolates.

Topics: Adolescent; Anti-Bacterial Agents; ATP-Binding Cassette Transporters; Bacterial Proteins; Child, Preschool; Clindamycin; Drug Resistance, Bacterial; Erythromycin; Female; Genetic Variation; Humans; Male; Microbial Sensitivity Tests; Plasmids; Soft Tissue Infections; Staphylococcal Infections; Staphylococcal Skin Infections; Staphylococcus aureus; Streptogramin A

NXL103 (linopristin/flopristin, 30/70) is a novel oral streptogramin combination with activity against a large variety of multidrug-resistant Gram-positive pathogens. The objective of this study was to evaluate the in vitro activity of NXL103 in comparison with oral comparators (clindamycin and linezolid). Six clinical isolates [four meticillin-resistant Staphylococcus aureus (MRSA) and two Streptococcus pyogenes] were exposed for 48 h in an in vitro pharmacokinetic/pharmacodynamic (PK/PD) model at a starting inoculum of ca. 10(6) colony-forming units (CFU)/mL. Antimicrobial simulations included NXL103 500 mg every 12 h, linezolid 600 mg every 12 h and clindamycin 450 mg every 6 h. Bactericidal and static effects were defined as ≥3log(10) and <3log(10) CFU/mL kill from the starting inoculum, respectively. Experiments were performed in duplicate to ensure reproducibility, and differences between regimens were evaluated by analysis of variance (ANOVA) with Tukey's post-hoc test. NXL103 exhibited lower minimum inhibitory concentrations than comparators, with values ≤0.06 mg/L for S. pyogenes and 0.125-0.25 mg/L for MRSA isolates. In the PK/PD model, NXL103 demonstrated significantly better activity than linezolid and clindamycin (P<0.05), achieving sustained bactericidal activity within <2 h against S. pyogenes strains and between 7.3-32 h against MRSA isolates. In contrast, linezolid only exhibited a static effect, whereas clindamycin achieved 3log(10) kill at 6h against the unique clindamycin-susceptible S. pyogenes strain evaluated. In conclusion, at therapeutic concentrations NXL103 exhibits promising activity against both MRSA and S. pyogenes strains, including clindamycin-resistant organisms. Further in vitro and in vivo experiments are warranted to explore the therapeutic benefit of NXL103 for the treatment of Gram-positive skin and soft-tissue infections.

Topics: Acetamides; Anti-Bacterial Agents; Clindamycin; Drug Combinations; Humans; Linezolid; Male; Methicillin-Resistant Staphylococcus aureus; Microbial Sensitivity Tests; Oxazolidinones; Staphylococcal Infections; Staphylococcus aureus; Stem Cells; Streptococcal Infections; Streptococcus pyogenes; Streptogramin A; Streptogramin B

A novel streptogramin A, pleuromutilin, and lincosamide resistance determinant, Vga(E), was identified in porcine methicillin-resistant Staphylococcus aureus (MRSA) ST398. The vga(E) gene encoded a 524-amino-acid protein belonging to the ABC transporter family. It was found on a multidrug resistance-conferring transposon, Tn6133, which was comprised of Tn554 with a stably integrated 4,787-bp DNA sequence harboring vga(E). Detection of Tn6133 in several porcine MRSA ST398 isolates and its ability to circularize suggest a potential for dissemination.

Topics: Animals; Anti-Bacterial Agents; ATP-Binding Cassette Transporters; Bacterial Proteins; Base Sequence; Diterpenes; DNA Transposable Elements; Drug Resistance, Multiple, Bacterial; Genes, Bacterial; Lincosamides; Methicillin-Resistant Staphylococcus aureus; Microbial Sensitivity Tests; Molecular Sequence Data; Plasmids; Pleuromutilins; Polycyclic Compounds; Sequence Analysis, DNA; Staphylococcal Infections; Streptogramin A; Swine

Methicillin-resistant Staphylococcus aureus clonal lineage ST398 and methicillin-susceptible lineage ST9 strains have their main reservoir in swine but can colonize and cause infections in humans. The phenicol/lincosamide/oxazolidinone/pleuromutilin/streptogramin A multidrug resistance gene cfr was detected in isolates of both clonal lineages, rendering a spread to humans with exposure to swine farming possible.

Topics: Animals; Anti-Bacterial Agents; Bacterial Proteins; Drug Resistance, Multiple, Bacterial; Genes, Bacterial; Humans; Methicillin-Resistant Staphylococcus aureus; Plasmids; Staphylococcal Infections; Staphylococcus aureus; Swine

A novel ABC transporter gene, vga(C), was identified on the 14,365-bp multiresistance plasmid pKKS825 in a porcine methicillin (meticillin)-resistant Staphylococcus aureus isolate of sequence type 398. The vga(C) gene encodes a 523-amino-acid protein which confers resistance not only to streptogramin A antibiotics but also to lincosamides and pleuromutilins. Plasmid pKKS825 also carries the resistance genes aadD, tet(L), and dfrK, which may enable the coselection of vga(C) under selective pressure by kanamycin/neomycin, tetracyclines, and trimethoprim.

Topics: Animals; Anti-Bacterial Agents; ATP-Binding Cassette Transporters; Bacterial Proteins; Diterpenes; Drug Resistance, Multiple, Bacterial; Kanamycin; Lincosamides; Methicillin-Resistant Staphylococcus aureus; Molecular Sequence Data; Neomycin; Plasmids; Pleuromutilins; Polycyclic Compounds; Staphylococcal Infections; Streptogramin A; Swine; Swine Diseases; Tetracyclines; Trimethoprim