MRSA (Mersa) Questions

Antibiotic-Resistant "Superbugs" May Be Transmitted From Animals to Humans

Link: JAMA -- Antibiotic-Resistant "Superbugs" May Be Transmitted From Animals to Humans, November 14, 2007, Kuehn 298 (18): 2125.

The emergence of antibiotic resistance on farms where livestock are routinely treated with antimicrobials has been well documented, but whether it poses a human health threat has been controversial. Now, a growing body of evidence suggests these "superbugs" of animal origin are being transmitted to humans. A trio of posters presented at the Interscience Conference on Antimicrobial Agents and Chemotherapy in September highlighted evidence that resistant bacteria themselves or bits of DNA containing genes encoding drug resistance can and do cross from animals to humans. Additionally, 2 recent epidemiological studies in distinct human populations suggest that bacteria are developing resistance to antibiotics on poultry farms and that these resistant bacteria are colonizing humans.

Researchers discover new strategies for antibiotic resistance

Link: Researchers discover new strategies for antibiotic resistance.

Drs. Michael R. Yeaman and Nannette Y. Yount present evidence that small proteins in the immune systems of humans and all kingdoms of life share fundamental structural and functional characteristics that enable these molecules to inhibit or kill microbial pathogens – even as these pathogens evolve to resist conventional antibiotics. "These findings reveal that nature uses a recurring molecular strategy to defend against infection," said Dr. Yeaman. "A clearer understanding of this strategy provides new opportunities to develop innovative anti-infective therapies to better prevent or treat life-threatening infections that resist current antibiotics." Most modern antibiotics work by targeting specific structures or functions in microbial pathogens. If the targets change due to mutation, pathogens can quickly become resistant to the antibiotics. In contrast, immune system molecules have retained the ability to fight infection – even as microbes evolve.

Clindamycin still very effective despite extensive CA MRSA Use

Link: HighWire Press -- Medline Abstract.

A previous study at our institution revealed 98% of methicillin-resistant Staphylococcus aureus (MRSA) isolates were susceptible to clindamycin; however, beta-lactams were then the predominant empiric treatment. This follow-up chart review study examined subsequent staphylococcal skin and soft tissue infection treatment and susceptibility patterns over a 2-year period. Of 296 S. aureus skin and soft tissue infections, 73% were MRSA, of which 87% were community-associated-MRSA; MRSA infections peaked in warm summer months. Despite a significant increase in empiric clindamycin use, 97% of community-associated-MRSA isolates retained susceptibility to clindamycin.

Hospital strains help community strains become resistant?

Link: HighWire Press -- Medline Abstract.

CONCLUSIONS: This study demonstrated that although CA-MRSA genotypes were heterogeneous, the predominant genotype that was circulating in our community was genotype A. Also, the multidrug resistance of CA-MRSA might be connected to the spreading of nosocomial strains in the community.

MRSA has creeping resistance to key drugs

Link: HighWire Press -- Medline Abstract.

Methicillin-resistant Staphylococcus aureus (MRSA) isolates (n = 3,189) from 2,990 patients were investigated by agar screening and by the E-test(TM) macromethod for reduced susceptibility to glycopeptide. No vancomycin-resistant S. aureus or glycopeptide-intermediate S. aureus (GISA) were detected but 178 isolates were confirmed as hetero-GISA (hGISA) by vancomycin population analysis profile (PAP)-area under the curve (vPAP-AUC) ratio determination and/or teicoplanin PAP (tPAP) methods. Of 139 isolates detected using the recommended E-test(TM) macromethod cut-off values of >/=8 mg/L for both vancomycin and teicoplanin or >/=12 mg/L for teicoplanin alone, 73 were confirmed as hGISA by vPAP-AUC, 95 by tPAP and 108 by both methods.

Antibiotic Resistance: Doctors' Antibiotic Prescribing Practices Still Contributing To Problem

Link: ScienceDaily: Antibiotic Resistance: Doctors' Antibiotic Prescribing Practices Still Contributing To Problem.

General practitioners are still prescribing antibiotics for up to 80% of cases of sore throat, otitis media, upper respiratory tract infections, and sinusitis, despite the fact that official guidance warns against this practice, according to an analysis of the world's largest primary care database of consultations and prescriptions, published in a supplement to the Journal of Antimicrobial Chemotherapy. Although prescriptions of antibiotics for respiratory tract infections declined during the 1990s, GPs still continue to prescribe antibiotics for a high proportion of infections even if the causes of the symptoms are likely to be viral. And this practice is hindering efforts to prevent the spread of antibiotic resistance

Multi drug resistant MRSA noted in India

Link: HighWire Press -- Medline Abstract.

We report the prevalence of methicillin resistant Staphylococcus aureus (MRSA) infections and their antibiotic susceptibility pattern in our hospital located in eastern Uttar Pradesh. Out of total 549 strains of Staphylococcus aureus isolated from different clinical specimens 301 (54.85%) were found to be methicillin resistant. More than 80% of MRSA were found to be resistant to penicillin, cotrimoxazole, ciprofloxacin, gentamicin, erythromycin, tetracycline, 60.5% to amikacin and 47.5% to netilmicin. However, no strains were resistant to vancomycin. Many MRSA strains (32.0%) were multi-drug resistant. To reduce the prevalence of MRSA, the regular surveillance of hospital associated infection, monitoring of antibiotic sensitivity pattern and formulation of definite antibiotic policy may be helpful.

Antibiotics are over prescribed

Link: Prescribing of Antibiotics to Children Still at a Level to Cause Drug Resistance, Experts Warn.

Regular prescribing of antibiotics to children in the community is sufficient to sustain a high level of antibiotic resistance in the population, warn experts in a study published on bmj.com today. UK general practitioners are strongly encouraged to reduce antibiotic prescribing to minimize the risk of drug resistance, yet prescribing antibiotics to children remains common practice, write David Mant and colleagues at the University of Oxford. A paper published in 1999 reported that 55 percent of children aged 0-5 years in the UK (the group of patients who receive most antibiotics in the community) receive an average of 2.2 prescriptions for a �-lactam antibiotic like amoxicillin from their general practitioner each year. Although a reduction in prescribing (and the strategy of recommending a 24- to 48-hour delay before filling antibiotic prescriptions) has probably resulted in about a 40 percent decrease in consumption since then, unpublished data suggest that community antibiotic prescribing is again rising, they say. This week's BMJ also reports on a study showing that UK GPs are still prescribing antibiotics for a large proportion of patients with minor infections, despite national guidance. So they set out to assess the effect of antibiotic prescribing on antibiotic resistance in individual children in primary care.

VISA mutating and resisting daptomycin?

Link: Characterization of daptomycin nonsusceptible vancomycin-intermediate Staphylococcus aureus in a patient with endocarditis -- Julian et al., 10.1128/AAC.00559-07 -- Antimicrobial Agents and Chemotherapy.

New Way To Target And Kill Antibiotic-Resistant Bacteria Found

Link: New Way To Target And Kill Antibiotic-Resistant Bacteria Found.

Putting bacteria on birth control could stop the spread of drug-resistant microbes, and researchers at the University of North Carolina at Chapel Hill have found a way to do just that. The team discovered a key weakness in the enzyme that helps "fertile" bacteria swap genes for drug resistance. Drugs called bisphosphonates, widely prescribed for bone loss, block this enzyme and prevent bacteria from spreading antibiotic resistance genes, the research shows. Interfering with the enzyme has the added effect of annihilating antibiotic-resistant bacteria in laboratory cultures. Animal studies of the drugs are now underway. "Our discoveries may lead to the ability to selectively kill antibiotic-resistant bacteria in patients, and to halt the spread of resistance in clinical settings," said Matt Redinbo, Ph.D., senior study author and professor of chemistry, biochemistry and biophysics at UNC-Chapel Hill.