Multidrug-resistant Staphylococcus Aureus Research Articles

A role for non-alkaloidal constitutes in the antibacterial activity of Hydrastis canadensis

The medicinal plant goldenseal (Hydrastis canadensis) has been used historically to treat infection [1], and it is currently among the top ten best selling botanicals in the US. This plant has demonstrated activity in vitro against a number of bacteria, including multidrug-resistant Staphylococcus aureus (MRSA) [2]. Previous studies have implicated several alkaloids, including berberine, in the antibacterial activity of H. canadensis [2, 3]. Recent results from our laboratories, however, have led to the hypothesis that non-alkaloidal constituents also play an important role. An extract from the aerial portions of H. canadensis was separated into 12 fractions using flash chromatography. One of these fractions contained only very low (1000 x < MIC) concentrations of alkaloids, but it enhanced significantly the antibacterial activity of berberine. LC-MS analysis of all 12 of the fractions indicated three potential active compounds (thus far unidentified) that were present at the highest concentration in the active fraction. On the basis of experiments comparing antibacterial activity against wild type and efflux pump knockout mutants of S. aureus, the active constituents of the fraction appear to act as efflux pump inhibitors. Our studies indicate that goldenseal's mechanism of antibacterial activity may be more complex than previously reported, and suggest that H. canadensis could be useful for the treatment of drug resistant bacterial infections, particularly as a topical agent. In addition, we demonstrate the effectiveness of combining bioassay guided fractionation with comprehensive LC-MS analysis to identify potential potentiators/synergists in medicinal plants. Acknowledgements: Bill Burch, Bear Wallow Ginseng, Hendersonville, NC; Research Corporation Cottrell College Science Award CC6642; NSF-MRI Award 0420292.

Various routes of administration of 99mTc-labeled synthetic lactoferrin antimicrobial peptide hLF 1–11 enables monitoring and effective killing of multidrug-resistant Staphylococcus aureus infections in mice

The synthetic antimicrobial peptide representative of the first 11 N-terminal amino acids of human lactoferrin (hLF 1-11) kills multidrug-resistant Staphylococcus aureus (MRSA). This study displays antimicrobial activity of hLF 1-11, via various routes of administration, against MRSA infections in mice. Radiolabeling hLF 1-11 with technetium-99m ((99m)Tc-hLF 1-11) enables scintigraphic monitoring directly after administration. (99m)Tc-hLF 1-11 was taken up by the gall bladder, intestines, and kidneys. Most of the radioactivity was captured in the urinary bladder and about 1% of the injected dose accumulated into infected thigh muscles. At 2 or 24h after either intravenously, subcutaneously, intraperitoneally, or orally injected a single dose of 0.04 mg/kg hLF 1-11 in mice significantly reduced (20-60 times) the number of viable MRSA. In a dose-response setting in immunocompetent mice maximum bactericidal effects (10,000 times reduction) of intravenously injected (99m)Tc-hLF 1-11 was seen with 40 mg/kg whereas the same dose of orally administered (99m)Tc-hLF 1-11 induced about approximately 100 times reduction. In conclusion, intravenously and orally administrated (99m)Tc-hLF 1-11 accumulates in infected tissues and is highly effective against experimental infections with MRSA. Moreover, scintigraphy is an excellent tool to study the pharmacology of experimental compounds and to determine the uptake in infected tissues.

Tracking the in vivo evolution of multidrug resistance in Staphylococcus aureus by whole-genome sequencing.

The spread of multidrug-resistant Staphylococcus aureus (MRSA) strains in the clinical environment has begun to pose serious limits to treatment options. Yet virtually nothing is known about how resistance traits are acquired in vivo. Here, we apply the power of whole-genome sequencing to identify steps in the evolution of multidrug resistance in isogenic S. aureus isolates recovered periodically from the bloodstream of a patient undergoing chemotherapy with vancomycin and other antibiotics. After extensive therapy, the bacterium developed resistance, and treatment failed. Sequencing the first vancomycin susceptible isolate and the last vancomycin nonsusceptible isolate identified genome wide only 35 point mutations in 31 loci. These mutations appeared in a sequential order in isolates that were recovered at intermittent times during chemotherapy in parallel with increasing levels of resistance. The vancomycin nonsusceptible isolates also showed a 100-fold decrease in susceptibility to daptomycin, although this antibiotic was not used in the therapy. One of the mutated loci associated with decreasing vancomycin susceptibility (the vraR operon) was found to also carry mutations in six additional vancomycin nonsusceptible S. aureus isolates belonging to different genetic backgrounds and recovered from different geographic sites. As costs drop, whole-genome sequencing will become a useful tool in elucidating complex pathways of in vivo evolution in bacterial pathogens.

Susceptibility to daptomycin, quinupristin-dalfopristin and linezolid and some other antibiotics in clinical isolates of methicillin resistant and methicillin sensitive S.aureus from the Oslo area

Our study compared the susceptibility of 136 clinical isolates of Staphylococcus aureus and 119 multidrug-resistant Staphylococcus aureus (MRSA) isolates from Oslo to a range of antibiotics, including the novel antibiotics quinupristin-dalfopristin, linezolid and daptomycin. All isolates were susceptible to daptomycin, linezolid and quinupristin-dalfopristin, although a subgroup was less susceptible to the latter. There was no linkage between reduced susceptibility to daptomycin, linezolid or quinupristin-dalfopristin and resistance to other classes of antimicrobials. In addition, MRSA strains from 2004 have become more sensitive to fucidin and rifampicin. The results can be used to evaluate the appropriateness of breakpoints and to define a baseline for monitoring possible future emergence of resistance to daptomycin, quinupristin-dalfopristin and linezolid in Staphylococcus aureus in Norway.

Interactions of Acanthamoeba polyphaga with Listeria monocytogenes and MRSA

Bacterivorous protozoa and bacteria have been in co‐existence since the origin of life. This co‐existence has led unequivocally to the evolution of many different co‐interactions. Most bacteria are ingested and digested, but many escape ingestion for various reasons. Others are ingested but evade digestion, and a few, notoriously Legionella pneumophila, even have the capacity of multiplying within the protozoan host. The aims of this study were to elucidate the interactions of various multi‐drug‐resistant Staphylococcus aureus (MRSA) strains, Listeria monocytogenes sv4b, and Escherichia coli K12 with the amoeba, Acanthamoeba polyphaga. To evaluate the interactions, we set up co‐cultures in Neffs' amoebic saline, at a multiplicity of invasion (MOI) of 1:100 of amoeba to bacteria, and a temperature of 37°C, although the effects of MOI and temperature were also assessed. Survival of bacteria and amoeba was checked at regular intervals, coupled with microscopy. It was discovered under our test conditions, that E. coli was ingested and digested by A. polyphaga, but in contrast, L. monocytogenes, had the capacity to flourish in the presence of A. polyphaga. We also report, for the first time, that all six MRSA isolates tested, survived and replicated in association with A. polyphaga, in comparison to conditions where amoebae were absent. Indeed, we also have evidence suggesting that increases in MRSA, in the presence of A. polyphaga, may be attributable to intracellular survival and replication. These findings have profound implications for the hospital environment, where Acanthamoeba sp., are also commonly isolated. In conclusion, this study illustrates the significance of protozoa as vehicles augmenting the survival of MRSA and L. monocytogenes in the environment.

Severe Acute Respiratory Syndrome and pregnancy

Severe Acute Respiratory Syndrome and pregnancy