Friday, November 30, 2012

Methicillin-Resistant Staphylococcus aureus: A Food-Borne Pathogen?


Methicillin-Resistant Staphylococcus aureus: A Food-Borne Pathogen?


Nov 2012

Source

Institute of Farm Animal Genetics, Friedrich-Loeffler-Institut, 31535 Newstadt-Matieusee, Germany; email: sarah.wendlandt@fli.bund.de.

Abstract


Prior to the 1990s, most methicillin-resistant Staphylococcus aureus (MRSA) was hospital-associated (HA-MRSA); community-associated MRSA (CA-MRSA) then began to cause infections outside the health-care environment. The third significant emergence of MRSA has been in livestock animals [livestock-associated MRSA (LA-MRSA)]. The widespread and rapid growth in CA-MRSA and LA-MRSA has raised the question as to whether MRSA is indeed a food-borne pathogen. The observations on animal-to-animal and animal-to-human transfer of LA-MRSA have prompted research examining the origin of LA-MRSA and its capacity to cause zoonotic disease in humans. This review summarizes the current knowledge aboutMRSA from foodproducing animals and foods with respect to the role of these organisms to act as food-borne pathogens and considers the available tools to track the spread of these organisms. It is clear thatLA-MRSAandCA-MRSAand even HA-MRSA can be present in/on food intended for human consumption, but we conclude on the basis of the published literature that this does not equate to MRSA being considered a food-borne pathogen. Expected final online publication date for the Annual Review of Food Science and Technology Volume 4 is February 28, 2013. Please see http://www.annualreviews.org/catalog/pubdates.aspx for revised estimates.

Wednesday, November 21, 2012

Presence of antiseptic resistance genes in porcine methicillin-resistant Staphylococcus aureus.


Presence of antiseptic resistance genes in porcine methicillin-resistant Staphylococcus aureus.


2012

Source

Department of Health Technology and Informatics, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong.

Abstract


Numerous studies have documented the presence of methicillin-resistant Staphylococcus aureus (MRSA) in meat-producing animals, which has led to concern about its spread into the community. Disinfectants play an important role in reduction of contamination in both animal husbandry and food-preparation, helping control spread of organisms from foodstuffs, including raw meat. Plasmid-borne antiseptic resistance (AR) genes increasing tolerance to several disinfectants have been reported in S. aureus of human origin (qacA/B and smr) and from bovine, equine, and caprine staphylococcal isolates (qacG, qacH, and qacJ). This study investigated the presence of AR genes in porcine MRSA isolates. Plasmid DNA from 100 MRSA ST9 strains isolated from pig carcasses was amplified for the presence of AR genes. Minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) to benzalkonium chloride (BC) and chlorhexidine gluconate (CHX) were determined in AR gene-positive isolates. qacG was present in 45 strains, eight of which also harbored smr. No strains carried qacA/B, qacH or qacJ. Presence of smr increased MICs to both BC and CHX and MBCs of CHX, but qacG presence only resulted in elevated MBC for CHX. This is the first report of AR genes from a porcine source. AR gene positivity has previously been associated with methicillin resistance and AR gene presence in these strains may increase their ability to persist in the environment. Improved implementation of hygiene measures during transportation and pre- and post-slaughter should be considered to prevent spread in the community.

Complete Genome Sequence of Wide-Host-Range Staphylococcus aureus Phage JD007.


Complete Genome Sequence of Wide-Host-Range Staphylococcus aureus Phage JD007.


Dec 2012

Source

Department of Medical Microbiology and Parasitology, Institutes of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai, China.

Abstract


Methicillin-resistant Staphylococcus aureus-related infections have become a serious problem worldwide. Bacteriophage therapy is an alternative approach against this threat. S. aureus phage JD007, which belongs to the Myoviridae family according to transmission electron microscopic imaging, could lyse nearly 30% of the S. aureus strains from Ruijin Hospital, Shanghai, China, and was isolated from chicken feces in Shanghai, China. The complete genome showed that JD007 is a linear, double-stranded DNA phage 141,836 bp in length with a GC content of 30.4% encoding 217 open reading frames. A BLAST search of the JD007 genome revealed that it was very similar to that of phage GH15.

Friday, November 16, 2012

Difference in agr Dysfunction and Reduced Vancomycin Susceptibility between MRSA Bacteremia Involving SCCmec Types IV/IVa and I-III.

Difference in agr Dysfunction and Reduced Vancomycin Susceptibility between MRSA Bacteremia Involving SCCmec Types IV/IVa and I-III.

2012

Source

Department of Infectious Diseases, Chonnam National University Medical School, Gwang-ju, Republic of Korea.

Abstract


BACKGROUND:

Dysfunction of agr, with reduced susceptibility or hetero-resistance to vancomycin, is thought to be associated with a worse outcome of methicillin-resistant Staphylococcus aureus (MRSA) bacteremia (MRSAB). However, the difference in agr dysfunction according to the SCCmec type in MRSA infection is undetermined. We compared the prevalence of agr dysfunction, reduced vancomycin susceptibility and the outcomes of SCCmec IV/IVa and I-III MRSAB.

METHODS:

The study included 307 cases of MRSAB. SCCmec types were determined by multiplex PCR. The clinical and microbiological features and outcomes of 58 SCCmec IV/IVa MRSAB were compared with those of 249 SCCmec I-III MRSAB.

RESULTS:

Compared with SCCmec I-III MRSAB, SCCmec IV/IVa MRSAB was associated with lower rates of agr dysfunction, three percent versus forty three percent, vancomycin minimum inhibitory concentration (MIC) = 2 µg/mL three perecent versus fifteen percent, and hetero-resistance to vancomycin zero versus eight percent. However, the 30-day and S. aureus-related mortality in patients with SCCmec IV/IVa MRSAB were not different from those in patients with SCCmec I-III MRSAB in multivariate analyses

CONCLUSIONS:

SCCmec IV/IVa MRSAB was associated with lower rates of agr dysfunction and hetero-resistance to vancomycin and a lower vancomycin MIC, compared with SCCmec I-III MRSAB. However, the outcomes of SCCmec IV/IVa MRSAB did not differ from those of SCCmec I-III MRSAB.

Environmental Contamination as a Risk Factor for Intra-Household Staphylococcus aureus Transmission.


Environmental Contamination as a Risk Factor for Intra-Household Staphylococcus aureus Transmission.


2012

Source

Division of Infectious Diseases, Department of Medicine, Columbia University, College of Physicians & Surgeons, New York, New York, United States of America.

Abstract


BACKGROUND:

The household is a recognized community reservoir for Staphylococcus aureus. This study investigated potential risk factors for intra-household S. aureus transmission, including the contribution of environmental contamination.

METHODS:

We investigated intra-household S. aureus transmission using a sample of multiple member households from a community-based case-control study examining risk factors for CA-MRSA infection conducted in Northern Manhattan. During a home visit, index subjects completed a questionnaire. All consenting household members were swabbed, as were standardized environmental household items. Swabs were cultured for S. aureus. Positive isolates underwent further molecular characterization. Intra-household transmission was defined as having identical strains among two or more household members. Multiple logistic regression was used to identify independent risk factors for transmission.

RESULTS:

We enrolled 291 households: 146 index cases, 145 index controls and 687 of their household contacts. The majority of indexes were Hispanic (85%), low income (74%), and female (67%), with a mean age of 31 (range 1-79). The average size of case and control households was 4 people. S. aureus colonized individuals in 62% of households and contaminated the environment in 54% of households. USA300 was the predominant clinical infection, colonizing and environmental strain. Eighty-one households had evidence of intra-household transmission: 55 (38%) case and 26 (18%) control households (P<.01). Environmental contamination with a colonizing or clinical infection strain (aOR: 5.4 [2.9-10.3] P<.01) and the presence of a child under 5 (aOR: 2.3 [1.2-4.5] P = .02) were independently associated with transmission. In separate multivariable models, environmental contamination was associated with transmission among case (aOR 3.3, p<.01) and control households (aOR 27.2, p<.01).

CONCLUSIONS:

Environmental contamination with a colonizing or clinical infection strain was significantly and independently associated with transmission in a large community-based sample. Environmental contamination should be considered when treating S. aureus infections, particularly among households with multiple infected members.


Tuesday, November 13, 2012

Orphan Drug AeroVanc for MRSA Lung Infection in CF


Orphan Drug AeroVanc for MRSA Lung Infection in CF



Savara Pharmaceuticals announced that the FDA has granted orphan drug status to AeroVanc (vancomycin hydrochloride inhalation powder) for the treatment of pulmonary methicillin-resistant Staphylococcus aureus (MRSA) infection in cystic fibrosis (CF) patients. AeroVanc is a proprietary inhaled dry powder form of vancomycin in a capsule-based device designed for self-administration.

Savara is currently preparing for its Phase 2a clinical study of AeroVanc's efficacy, to be carried out in 20 CF centers in the United States. AeroVanc has demonstrated positive safety and tolerability results in Phase 1 clinical studies conducted in healthy subjects and patients with cystic fibrosis, with a pharmacokinetic profile that supports its potential as a once- or twice-daily treatment for pulmonary MRSA infection.
Vancomycin administered by IV is the antibiotic of choice for the treatment of MRSA-related bronchopneumonia, however, IV administration, poor penetration into the lungs and systemic toxicities limit its use in a chronic setting. By delivering vancomycin directly to the site of infection, AeroVanc is expected to improve clinical efficacy and reduce adverse effects due to systemic drug exposure.

Whole-Genome Sequence of Livestock-Associated ST398 Methicillin-Resistant Staphylococcus aureus Isolated from Humans in Canada.


Whole-Genome Sequence of Livestock-Associated ST398 Methicillin-Resistant Staphylococcus aureus Isolated from Humans in Canada.


Dec 2012

Source

National Microbiology Laboratory, Winnipeg, Manitoba, Canada.

Abstract


Despite reports of high colonization rates of ST398 livestock-associated methicillin-resistant Staphylococcus aureus(LA-MRSA) among pigs and pig farmers, the incidence of LA-MRSA infection in the general population in Canada appears to be rare in comparison to that in some European countries. In this study, the complete genome sequence of a Canadian representative LA-MRSA isolate (08BA02176) from a human postoperative surgical site infection was acquired and compared to the sequenced genome of an LA-MRSA isolate (S0385) from Europe to identify genetic traits that may explain differences in the success of these particular strains in some locales.

Wednesday, November 7, 2012

Riccardin C derivatives as anti-MRSA agents: Structure-activity relationship of a series of hydroxylated bis(bibenzyl)s.


Riccardin C derivatives as anti-MRSA agents: Structure-activity relationship of a series of hydroxylated bis(bibenzyl)s.


Oct 2012

Source

Division of Pharmaceutical Sciences, Okayama University, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 1-1-1, Tsushima-Naka, Kita-ku, Okayama 700-8530, Japan.

Abstract


Members of a series of macrocyclic bis(bibenzyl) riccardin-class derivatives were found to exhibit antibacterial activity towards methicillin-resistant Staphylococcus aureus (anti-MRSA activity). Structure-activity relationship (SAR) studies were conducted, focusing on the number and position of the hydroxyl groups. The minimum essential structure for anti-MRSAactivity was also investigated.

Staphylococcal Enterotoxin B Toxic Shock Syndrome Induced by Community-acquired Methicillin-resistant Staphylococcus aureus (CA-MRSA).


Staphylococcal Enterotoxin B Toxic Shock Syndrome Induced by Community-acquired Methicillin-resistant Staphylococcus aureus (CA-MRSA).


2012

Source

Internal Medicine, Department of Pulmonary Medicine/Infection and Oncology, Nippon Medical School, Japan.

Abstract


We herein report a case of toxic shock syndrome (TSS) associated with the 2009 pandemic H1N1 (pH1N1) influenza virus and a community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infection in a 16-year-old Vietnamese girl. Staphylococcal enterotoxin B (SEB) was detected in the patient's serum, and the level of anti-SEB antibodies was found to be elevated. A flow cytometric analysis showed evidence of activated SEB-reactive Vβ3(+) and Vβ12(+) T cells. These data suggest that the CA-MRSA-induced activation of SEB-reactive T cells may cause TSS in patients with pH1N1 virus infection. Moreover, this is the first report describing immunological confirmation of SEB contributing directly to TSS in a patient fulfilling the diagnostic criteria of TSS.

Methicillin-Resistant Staphylococcus aureus (MRSA) Detected at Four U.S. Wastewater Treatment Plants.


Methicillin-Resistant Staphylococcus aureus (MRSA) Detected at Four U.S. Wastewater Treatment Plants.


Nov 2012

Source

Maryland Institute for Applied Environmental Health, University of Maryland School of Public Health, College Park, Maryland, USA.

Abstract


Background: The incidence of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infections is increasing in the United States, and it is possible that municipal wastewater could be a reservoir of this microorganism. To date, no U.S. studies have evaluated the occurrence of MRSA in wastewater.

Objective: We examined the occurrence ofMRSA and methicillin-susceptible S. aureus (MSSA) at U.S. wastewater treatment plants.

Methods: We collected wastewater samples from two Mid-Atlantic and two Midwest wastewater treatment plants between October 2009 and October 2010. 

Samples were analyzed for MRSA and MSSA using membrane filtration. Isolates were confirmed using biochemical tests and PCR (polymerase chain reaction). Antimicrobial susceptibility testing was performed by Sensititre® microbroth dilution. Staphylococcal cassette chromosome mec (SCCmec) typing, Panton-Valentine leucocidin (PVL) screening, and pulsed field gel electrophoresis (PFGE) were performed to further characterize the strains.

Data were analyzed by two-sample proportion tests and analysis of variance.

Results: We detected MRSA (n = 240) and MSSA (n = 119) in 22 of 44 (50%) and 24 of 44 (55%) wastewater samples, respectively. The odds of samples being MRSA-positive decreased as treatment progressed: 10 of 12 (83%) influent samples were MRSA-positive, while only one of 12 (8%) effluent samples was MRSA-positive. Ninety-three percent and 29% of unique MRSA and MSSA isolates, respectively, were multidrug resistant. SCCmec types II and IV, the pvl gene, and USA types 100, 300, and 700 (PFGE strain types commonly found in the United States) were identified among the MRSA isolates.

Conclusions: Our findings raise potential public health concerns for wastewater treatment plant workers and individuals exposed to reclaimed wastewater. Because of increasing use of reclaimed wastewater, further study is needed to evaluate the risk of exposure to antibiotic-resistant bacteria in treated wastewater.

Methicillin-resistant Staphylococcus aureus in Nasal Surveillance Swabs at an Intensive Care Unit: An Evaluation of the LightCycler MRSA Advanced Test.

Methicillin-resistant Staphylococcus aureus in Nasal Surveillance Swabs at an Intensive Care Unit: An Evaluation of the LightCycler MRSA Advanced Test.

Nov 2012

Source

Department of Laboratory Medicine, Dongguk University Ilsan Hospital, Goyang, Korea.

Abstract


BACKGROUND:

We compared the LightCycler MRSA advanced test (Roche Diagnostics, Germany) with enrichment culture methods to evaluate the relative diagnostic performance of the LightCycler MRSA advanced test for active surveillance in a high-prevalence setting.

METHODS:

A total of 342 nasal swab specimens were obtained from patients in the intensive care unit at admission and on the seventh day for follow-up. The results of LightCycler MRSA advanced test were compared to those of the enrichment culture. For discrepant results, mecA gene PCR was performed.

RESULTS:

For the detection of methicillin-resistant Staphylococcus aureus (MRSA), the LightCycler MRSA advanced test showed 98.5% sensitivity and 78.6% specificity and had positive and negative predictive values of 75.0% and 98.8%, respectively. A total of 46 samples had discrepant results between the LightCycler MRSA advanced test and enrichment culture. Of the 44 specimens that were positive in the LightCycler MRSA advanced test but negative by enrichment culture, mecA genes were detected in 37 specimens. In addition, of the original 44 cases, 21 patients had a history of MRSAcolonization or infection within the last month; of those 21 specimens, 20 were positive for mecA gene as shown by PCR. Seven mecA-negative discrepant specimens comprised 3 methicillin-sensitive S. aureus-culture positive and only 2 patients had MRSA infections.

CONCLUSIONS:

Despite its low specificity and positive predictive value, the LightCycler MRSA advanced test could serve as a rapid test for patients colonized with MRSA.

Sunday, November 4, 2012

Study determines best treatment timeline for MRSA-related pneumonia


Study determines best treatment timeline for MRSA-related pneumonia



A recent study at Henry Ford Hospital found that while the national practice guideline for treating MRSA-related pneumonia is seven to 21 days, effective treatment time could be achieved in half that time.
Researchers determined that patients treated for eight to 13 days on a therapy of either vancomycin or linezolid antibiotics experienced the highest rate of survival. The study is thought to be the first to evaluate MRSA-related pneumonia’s length of treatment.
The study was presented on Friday at the San Diego-based meeting of the Infectious Diseases Society of America.
“Based on our study, clinicians can effectively treat their patients within eight to 13 days, thus minimizing patients’ exposure to antibiotics and their side effects,” Hadeel Zainah, the study’s lead author, said.
The retrospective study involved the evaluation of the medical charts of 115 patients who were hospitalized with MRSA pneumonia. The patients received either linezolid, vancomycin or both.
Forty-percent of the patients were treated from eight to 13 days, 27 percent were treated for 14 to 20 days, and 13.9 percent of patients received treatment for more than 20 days. Patients treated between 14 and 20 days and for more than 20 days experienced lower survival rates.
Thirty-two of the patients died after 28 days.
The study did not evaluate if treatment duration affected length of stay or whether one antibiotic was more effective than the other.
MRSA-related pneumonia is a respiratory illness that can follow a bout of influenza. Symptoms include fever, chills, shortness of breath, headache, sore throat and cough.

Anti-MRSA Drug Fast-Tracked

Anti-MRSA Drug Fast-Tracted

BY Paul Bass | OCT 11, 2012 10:39 AM


Superbugs beware: a bunch of scientists in lab coats in downtown New Haven have your number.
The white-coated researchers gathered in their offices at the 300 George St. biotech complex Wednesday to mark a milestone: a decision by federal regulators to put a new antibiotic they’re developing on a fast track to approval.
They also gathered to thank a politician who helped them get there, Connecticut U.S. Sen. Dick Blumenthal.
The gathering took place in the third-floor suite belong to Rib-X (pronounced RYE-bex), an 11-year-old pharmaceutical company that employs 43 people to develop antibiotics to combat deadly “superbugs,” bacteria that have developed resistance to existing medicines.
The Food and Drug Administration has designated a Rib-X drug working its way toward approval, called radezolid, a “qualified infectious disease product.” That means it can get an extra five years of market exclusivity (no generic competitors allowed) if approved. And it will get a “priority review” and “fast-track status” from FDA regulators as it tries to speed its way toward approval. A Nobel Prize-winning Yale chemist named Thomas Steitz helped develop it.
Rib-X received the same FDA designation last month for another drug under development called delafoxacin. Both drugs treat a wide range of infections including MRSA (aka methicillin-resistant Staphylococcus aureus), a fast-growing virus that kills 17,000 Americans a year.
A new law called The GAIN (Generating Antibiotic Incentives Now), which passed earlier this year, created the FDA designation. Blumenthal cosponsored it. Rib-X was the first company to benefit from it.
Blumenthal sponsored the law to “streamline and fast-track the products that can save lives,” he said at Wednesday’s gathering. The “antiobiotic pipeline” has been drying up, he said, because unlike “blockbuster” drugs like cholesterol-fighting Lipitor—which patients buy their entire lives, thus ensuring its makers profits—antibiotics are designed for up to two weeks’ use. And that means less potential profit for potential investors in the development of new drugs. Blumenthal said the GAIN Act is meant to get new antibiotics flowing through that pipeline.
Blumenthal (pictured) was making a return visit to the 300 George biotech complex. He made it a campaign stop in 2010 to demonstrate the kind of new-economy jobs he hoped to help promote if elected to the Senate.
On Wednesday, Blumenthal said he learned some lessons about medicine in working on the GAIN Act. He also learned a political lesson: “Bipartisanship is possible for a good cause.” Republicans, most notably Tennessee’s Bob Corker, worked with Blumenthal on the bill.
Blumenthal was asked if these new medicines simply lead to newer super-bugs, requiring more and more antibiotics; and if it makes more sense to find new ways to stop people from getting infections in the first place.
His answer: We need to do both.
He advocated “exploring” cutting down on hospital-acquired infections through disposable equipment and more frequent hand-washing, for instance; and avoiding overusing antibiotics on, for instance, cattle and other factory-farmed animals.
At the same time, “people have these diseases now” and need antibiotics that work, he argued. Also, he said, drugs have wiped out some diseases in the past, and that remains a worthwhile quest.
“There will always be an arms race with the bugs,” added Rib-X Chief Scientific Officer Erin Duffy (at far left in the photo at the top of this story). “Some will be conquered. There will always be the evolution process” requiring that science “stay ahead. ... “To surrender is to say MRSA will spread and there’s nothing we can do” to stop it.