New Technologies

We’re seeing all sorts of advances in fighting MRSA lately! AdvanSource Biomaterials Corporation recently received a patent for antimicrobial polyurethane resins, which can be used structurally or as coatings in different kinds of catheters, and are intended to help combat methicilin-resistant staphylococcus aureus (MRSA) infections.

Press release here: http://phx.corporate-ir.net/phoenix.zhtml?c=68271&p=irol-newsArticle&ID=1463328

Also, on the heels of the emergence of the NDM-1 gene, BioScience Laboratories announced that they’ve obtained seven clinical isolates of Carbapenem-Resistant (CR) Klebsiella pneumonia and Escherichia coli. BioScience Laboratories intends to use these isolates to test products for their predicted efficacy against bacteria containing the NDM-1 gene.

Press release here: http://www.24-7pressrelease.com/press-release-rss/bioscience-laboratories-announces-testing-capabilities-for-ndm1-165887.php

New coating kills MRSA on contact

Researchers have developed a way to coat surfaces with an enzyme that kills MRSA within 20 minutes of contact, says a recent publication in ACS Nano.  The enzyme, lysostaphin, degrades cell walls of Staphylococcus aureus and epidermidis, thus killing the harmful bacteria. 

The researchers had spent several years studying carbon nanotube-enzyme pairs, called conjugates.  Enzymes in coating alone either degrade or leach into the surroundings, but when paired with carbon nanotubes, the authors found that the enzymes were more stable and more densely packed when embedded into polymers such as paint. 

Lysostaphin is extremely selective, killing just S. aureus and epidermidis, is harmless to humans, and does not induce bacterial resistance.  The enzyme-nanotube conjugate also doesn’t become clogged over time, a common problem with other antimicrobial coatings.  Perhaps most impressively, antimicrobial films made with the conjugate were greater than 99% effective in killing all MRSA that came in contact with the film, measured after 2 hours.  And there’s even more: the films are reusable and washable, and stable under dry storage conditions for at least a month.

The lysostaphin-nanotube conjugate could be embedded into paint used in hospital rooms, or into films to put on various other hospital surfaces.  It will be extremely exciting to see how this technology is put to use.

Link to ACS Nano abstract: http://pubs.acs.org/doi/full/10.1021/nn100932t

MRSA infections down, but new threat on the horizon

A study just published in The Journal of the American Medical Association (JAMA) shows that the incidence of hospital-onset methicillin-resistant staphylococcus aureus (MRSA) infection decreased by 28% from 2005 to 2008.  The measurements, taken from 9 major metropolitan areas across the country, also show that MRSA rates for healthcare-associated community-onset infections decreased 17% over the same time period. 

The study’s authors, Kallen et al., are unable to say why the rates decreased, but mention a couple possible factors.  The first possibility is the widespread implementation of MRSA prevention practices.  Kallen et al. note that “the fact that the observed reductions were greater among hospital-onset infections than healthcare–associated community-onset infections suggests that prevention practices in acute care settings contributed” to the decrease in MRSA infection rates.  Another potential factor is a change in the strains associated with MRSA infections, but the authors state that there weren’t changes in MRSA strain composition during that time period, so this is unlikely to be a valid explanation. 

Immediately on the heels of this good news comes a study published in The Lancet Infectious Diseases today, which details how a new bacterial gene might cause worldwide health problems.

NDM-1, which stands for New Dheli metallo-β-lactamase 1, makes bacteria highly resistant to many classes of antibiotics, including the carbapenems.  Unfortunately, the gene has been determined to be readily transmitted and also highly adaptable.  As bacteria that contains NDM-1 encounters bacteria that doesn’t, NDM-1 could insinuate itself into the new bacteria, thus creating a larger resistant population.  The problem is particularly worrying because there is not a single antibiotic in the discovery and production process that is effective against NDM-1-containing bacteria – and because NDM-1 is highly adaptable, it could potentially change itself to resist any drugs that are developed. 

In addition to this already grim news, most of the isolates taken from India were from community-acquired infections, which implies that bacteria with the NDM-1 gene are already pervasive.  The NDM-1 gene has also already spread to the UK and Sweden – and some of the UK patients had recently traveled to India for medical treatments. 

We’re left with a good news/bad news scenario: just as we are starting to see MRSA infection rates fall, we learn that NDM-1-containing bacteria is expected to spread around the globe.

JAMA article: http://jama.ama-assn.org/cgi/content/full/304/6/641
Lancet article: http://www.thelancet.com/journals/laninf/article/PIIS1473-3099%2810%2970143-2/fulltext

Playing chess with MRSA

Researchers from Duke University Medical Center developed a protein design algorithm that is capable of predicting potential drug resistance mutations in MRSA. The algorithm turns predicting mutations into a game of chess where the computer is like a chess player that tries to anticipate an opponent's moves.

The researchers built the algorithm to look for mutations in a specific MRSA enzyme called dihydrofolate reductase (DHFR). DHFR is necessary for MRSA to replicate itself and is also a key source of drug-resistant mutation. The algorithm looks for mutations in DHFR with two key characteristics. First is a positive design mutation which is a mutation that still allows the enzyme to function. The second is a negative design mutation which is a mutation that blocks the function of the drug.

The algorithm could be incorporated into better drug design to beat MRSA's drug-resistant mutations. For example, scientists would be able to design drugs that can pre-emptively deal with possible resistance in the future.

More on this topic

Class I Recall of Cepheid’s Xpert MRSA/SA Blood Culture Assay products for use with GeneXpert Dx System

As reported on fda.gov, “The firm received increasing numbers of complaints for false negative MRSA results when compared to MRSA positive results received from culture methods. All Cepheid MRSA/SA Blood Culture Assay products have a potential of generating infrequent rates of false negative MRSA results, which could result in incorrect treatment or delay of care for patients with MRSA infection.”

“On July 1, 2010, the company issued a press release and sent its customers a revised Corrective Action Notice letter instructing them not to report the MRSA negative result when a MRSA negative/SA positive result is generated on the Cepheid MRSA/SA Blood Culture Assay. Instead, customers were instructed to conduct further antimicrobial susceptibility testing to determine the MRSA result. The MRSA positive/SA positive results generated on the Cepheid MRSA/SA Blood Culture Assay can still be reported. The new instructions will be incorporated in future product labeling. “

The FDA goes on to note that Class I recalls are the most serious type of recall, and that if the products are used, there is a reasonable probability that they will cause serious adverse health consequences, or death.

More information, including model and lot numbers, can be found on the FDA’s website at: http://www.fda.gov/MedicalDevices/Safety/RecallsCorrectionsRemovals/ListofRecalls/ucm218002.htm.

MRSA and survival

Dr. Dan Diekema recently blogged about a new study published in JAMA that shows that respiratory tract MRSA carriage/infection is linked to high mortality in cystic fibrosis patients. He raises an interesting question about why MRSA, and not MSSA, is associated with worse outcome among cystic fibrosis patients especially since there is no evidence to show that MRSA is intrinsically more virulent than MSSA (Now, this is debatable as there are studies that show that MRSA is more virulent than MSSA, however the justifications behind why this is the case are controversial).

Nevertheless, Dr. Diekema’s question reminded me of an article I read on toxoplasma in last week’s Economist. Toxoplasma is a pathogen that’s a close cousin to Plasmodium, the bug that causes malaria. However, despite its high prevalence, symptoms among people infected with toxoplasma are mild and the bug doesn’t seem to cause a lot of damage, UNTIL scientists discovered that rats infected by toxoplasma exhibit more risky behavior, which suggests that the bug is interfering with the brain.

A separate study on toxoplasma in humans found that people involved in road accidents were almost three times more likely to be infected by toxoplasma than those who had not been. Some are going as far as saying that toxoplasma is altering the culture of entire societies.

So, here is my theory to answer Dr. Diekema’s question, maybe MRSA is affecting patients’ psychology and/or behavior in a way similar to that of toxoplasma? Or could it be that MRSA colonization/infection leads to higher susceptibility to toxoplasma infection, which leads to more risky behavior? i.e. not following hand hygiene compliance. I wonder what kind of study we can do to prove my theory.

APIC’s MRSA Census Coming to Your Hospital

How big of a threat is MRSA to hospitals? The recently released APIC survey attempts to answer just that.

MRSA, or Methicillin-resistant Staphylococcus aureus, is responsible for an estimated 19,000 deaths a year in the U.S. and costs hospitals an additional $60,000 per patient who acquires a MRSA infection in the hospital. In October 2006, APIC conducted the first-ever national MRSA prevalence study and found that 46 out of every 1,000 patients in the study were either infected or colonized with MRSA. The rate was larger than previously estimated and led to several concerted efforts by APIC to combat MRSA. The goal of this year’s survey is to update the study results with the current MRSA prevalence rate. The comparison will help evaluate the impact of recent MRSA prevention measures on MRSA prevalence.

The Centers for Medicare & Medicaid Services (CMS) has not yet begun to penalize hospitals with high MRSA infection rates by reducing reimbursement. However, given the current trend that focuses on pay-for-performance, it’s likely that CMS will refuse to pay for preventable MRSA infections in the future.

Therefore, I urge every hospital to participate in this important survey. After all, how do we fight MRSA if we don’t know what kind of problem we are dealing with? The survey results affect the measures and solutions we adopt, the amount of resources we need and receive, the type of care we provide to patients, and the kind of research and innovation that will be necessary to combat the infection.

APIC MRSA Survey