A novel oral carbapenem CS-834: chemical stability of pivaloyloxymethyl esters of carbapenems and cephalosporins in phosphate buffer solution

Characterization of 26 Isolates of Staphylococcus Aureus, Predominantly from Dairy Sheep, Using Four Different Techniques of Molecular Epidemiology

Little information is available regarding the molecular epidemiology of Staphylococcus aureus–induced mastitis in dairy sheep. In this study, 4 different typing techniques were compared in typing 26 S. aureus isolates, predominantly from cases of subclinical mastitis in dairy ewes. The 4 techniques were pulsed-field gel electrophoresis (PFGE), restriction fragment length polymorphism (RFLP) on 2 genes (coagulase and clumping factor B), randomly amplified polymorphic DNA–polymerase chain reaction (PCR) (RAPD-PCR), and multilocus sequence typing (MLST). On the basis of discriminatory power as the key parameter of typing systems, MLST and PFGE were found to be the most powerful techniques. The MLST and PFGE could contribute to epidemiological surveillance and evaluation of mastitis control programs, by documenting prevalence and dissemination of endemic clones in infected populations. The results of this study show that a single clone of S. aureus is widely distributed in infected ewe mammary glands.

Sublethal vancomycin-induced ROS mediating antibiotic resistance in Staphylococcus aureus

S. aureus may cause many human infectious diseases, which is well-known for the quickly developed drug resistance. Reports have shown that oxidative stress connects with bactericidal antibiotics. Our results exhibit that at least induced ROS may be beneficial to vancomycin resistance in two strains of hVRSA. The present findings help to recover novel insights into the relationships between oxidative stress and bacterial resistance, which has important implications for further use of antibiotics and development of therapeutics strategies for hVRSA.

Staphylococcus aureus is the leading cause of many human infectious diseases. Besides infectious dangers, S. aureus is well-known for the quickly developed drug resistance. Although great efforts have been made, mechanisms underlying the antibiotic effects of S. aureus are still not well clarified. Recently, reports have shown that oxidative stress connects with bactericidal antibiotics [Dwyer et al. (2009) Curr. Opin. Microbiol. 12, 482–489]. Based on this point, we demonstrate that reactive oxygen species (ROS) induced by sublethal vancomycin may be partly responsible for the antibiotic resistance in heterogeneous vancomycin resistant S. aureus (hVRSA). Sublethal vancomycin treatment may induce protective ROS productions in hVRSA, whereas reduction in ROS level in hVRSA strains may increase their vancomycin susceptibility. Moreover, low dose of ROS in VSSA (vancomycin susceptible S. aureus) strains may promote their survival under vancomycin conditions. Our findings reveal that modest ROS generation may be protective for vancomycin resistance in hVRSA. These results recover novel insights into the relationship between oxidative stress and bacterial resistance, which has important applications for further use of antibiotics and development of therapeutics strategies for hVRSA.

A comparison of the activities of lacticin 3147 and nisin against drug-resistant Staphylococcus aureus and Enterococcus species

OBJECTIVES

Our goal was to compare the activities of lacticin 3147 and nisin, two of the most well characterized lantibiotics, against antibiotic-resistant staphylococci and enterococci.

METHODS

We determined the MICs of lacticin 3147 and nisin for 20 strains of methicillin-resistant Staphylococcus aureus (MRSA), 20 strains of vancomycin-resistant enterococci (VRE), 6 strains of S. aureus with intermediate resistance to vancomycin (VISA), 5 strains of heterogeneous vancomycin-intermediate S. aureus (hVISA) and 4 strains of S. aureus that are susceptible to methicillin.

RESULTS

Lacticin 3147 displayed potent activity against VRE with MIC values between 1.9 and 7.7 mg/L, and varying levels of activity against S. aureus strains (MRSA, 1.9-15.4 mg/L; laboratory strains, >or=15.4 mg/L; hVISA, 15.4-30.9 mg/L; VISA, >or=61.8 mg/L). Nisin was more active against the S. aureus strains in general (MRSA and laboratory strains, 0.5-4.1 mg/L; VISA and hVISA, 2 to >or=8.3 mg/L), but was less effective than lacticin 3147 against VRE (2 to >or=8.3 mg/L).

CONCLUSIONS

Nisin is more effective against S. aureus whereas lacticin 3147 possesses greater potency against VRE. The modifications responsible for the vancomycin-resistant phenotypes of hVISA and VISA strains also provide protection against the two lantibiotics.

Insights on evolution of virulence and resistance from the complete genome analysis of an early methicillin-resistant Staphylococcus aureus strain and a biofilm-producing methicillin-resistant Staphylococcus epidermidis strain

Staphylococcus aureus is an opportunistic pathogen and the major causative agent of numerous hospital- and community-acquired infections. Staphylococcus epidermidis has emerged as a causative agent of infections often associated with implanted medical devices. We have sequenced the approximately 2.8-Mb genome of S. aureus COL, an early methicillin-resistant isolate, and the approximately 2.6-Mb genome of S. epidermidis RP62a, a methicillin-resistant biofilm isolate. Comparative analysis of these and other staphylococcal genomes was used to explore the evolution of virulence and resistance between these two species. The S. aureus and S. epidermidis genomes are syntenic throughout their lengths and share a core set of 1,681 open reading frames. Genome islands in nonsyntenic regions are the primary source of variations in pathogenicity and resistance. Gene transfer between staphylococci and low-GC-content gram-positive bacteria appears to have shaped their virulence and resistance profiles. Integrated plasmids in S. epidermidis carry genes encoding resistance to cadmium and species-specific LPXTG surface proteins. A novel genome island encodes multiple phenol-soluble modulins, a potential S. epidermidis virulence factor. S. epidermidis contains the cap operon, encoding the polyglutamate capsule, a major virulence factor in Bacillus anthracis. Additional phenotypic differences are likely the result of single nucleotide polymorphisms, which are most numerous in cell envelope proteins. Overall differences in pathogenicity can be attributed to genome islands in S. aureus which encode enterotoxins, exotoxins, leukocidins, and leukotoxins not found in S. epidermidis.