Tuesday, September 29, 2009

Microbiology of drugs for treating multiply drug-resistant Gram-positive bacteria.

Microbiology of drugs for treating multiply drug-resistant Gram-positive bacteria

J Infect. 2009 Sep

Division of Infectious Diseases, Beth Israel Deaconess Medical Center, Boston, Massachusetts 02215, USA.

George M. EliopoulosCorresponding Author Contact Information, a, E-mail The Corresponding Author

Several new antimicrobials demonstrate in vitro activity against methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), and other Gram-positive bacteria. Data from large surveys indicate that linezolid, daptomycin, and tigecycline are almost universally active against MRSA. Linezolid and tigecycline inhibit both Enterococcus faecium and Enterococcus faecalis at low concentrations; daptomycin is somewhat more potent against the latter. The investigational agents dalbavancin and telavancin are more potent than vancomycin against vancomycin-susceptible organisms. Dalbavancin inhibits vanB type VRE at low concentrations, but is not active against vanA type VRE. Telavancin is less active against VRE than against vancomycin-susceptible enterococci, but minimum inhibitory concentrations are lower than those of vancomycin against VRE. With continued careful use of available antimicrobials, the vast majority of these organisms should remain susceptible to 1 or more of the agents discussed for the foreseeable future.

ScienceDirect/Trends in Microbiology

Treatment options for nosocomial pneumonia due to MRSA.

Treatment options for nosocomial pneumonia due to MRSA.

J Infect. 2009

Department of Medicine, Winthrop University Hospital, Mineola, New York, USA. Michael S. NiedermanCorresponding Author Contact Information, a, b, E-mail The Corresponding Author

Keywords: Antibiotic resistance; Nosocomial pneumonia; Guidelines; MRSA; De-escalation therapy

Nosocomial pneumonia, which includes hospital-acquired pneumonia, ventilator-associated pneumonia, and health care associated pneumonia, remains an important cause of morbidity and mortality. The continuing emergence of methicillin-resistant Staphylococcus aureus (MRSA) as a nosocomial pneumonia pathogen is particularly problematic not only because of its prevalence, but also because antimicrobial resistance is increasingly associated with inappropriate empirical antibiotic therapy. As a result, intensivists are faced with the dual goals of providing initial accurate broad-spectrum antibiotic coverage to reduce mortality while minimizing the risk for the emergence of antimicrobial resistance. These competing goals can be achieved by using an approach that initially delivers liberal broad-spectrum coverage followed by de-escalation once culture results and serial clinical observations become available. In ventilator-associated pneumonia, linezolid has demonstrated favorable activity against Gram-positive bacteria, including MRSA, and is recommended in evidence-based guidelines as an alternative to vancomycin, particularly when MRSA is documented as the etiology.

Elsevier/Science Direct

Monday, September 21, 2009

Short communication: methicillin-resistant Staphylococcus aureus detection in US bulk tank milk.

Short communication: methicillin-resistant Staphylococcus aureus detection in US bulk tank milk.
J Dairy Sci. 2009 Oct

Virgin JE, Van Slyke TM, Lombard JE, Zadoks RN.
USDA, APHIS, VS, Centers for Epidemiology and Animal Health, Fort Collins, CO 80526-8117, USA.

* USDA:APHIS:VS, Centers for Epidemiology and Animal Health, 2150 Centre Ave., Bldg B, Fort Collins, CO 80526-8117 Quality Milk Production Services, College of Veterinary Medicine, Cornell University, Ithaca, NY14850-1263
1 Corresponding author:

Staphylococcus aureus is a major cause of mastitis in dairy cattle. This study estimated the herd prevalence of methicillin-resistant Staph. aureus (MRSA) among US dairy herds by testing bulk tank milk (BTM) samples using genotypic and phenotypic methods. A nationally representative sample of 542 operations had BTM cultured for Staph. aureus, and 218 BTM samples were positive upon initial culture. After 4 wk to 4 mo of frozen storage, 87% of 218 samples (n = 190) were still culture positive for Staph. aureus on blood agar, but none were positive for MRSA on the selective indicator medium CHROMagar MRSA. A duplex PCR was used to detect the Staph. aureus-specific nuc gene and the methicillin resistance gene, mecA, in mixed staphylococcal isolates from the 190 BTM samples that were positive for Staph. aureus after storage. Seven samples tested positive for nuc and mecA, and 2 samples tested positive for mecA only. MecA-positive Staphylococcus spp., but not MRSA, were subsequently isolated from 5 samples, whereas neither mecA-positive Staphylococcus spp. nor MRSA was isolated from the remaining 4 samples. Presence of methicillin-resistant, coagulase-negative Staphylococcus spp. may complicate the detection of MRSA by means of PCR on BTM. Bulk tank milk in the United States is not a common source of MRSA.

Journal of Dairy Science

Thursday, September 17, 2009

Toward the Development of Evidence-Based Guidelines for the Management of Methicillin-Resistant Staphylococcus aureus Otitis.

Toward the Development of Evidence-Based Guidelines for the Management of Methicillin-Resistant Staphylococcus aureus Otitis.

J Otolaryngol Head Neck Surg.
Macneil SD, Westerberg BD, Romney MG.


OBJECTIVES: (1) To determine the causative bacteriology of discharging ears in a case series from a tertiary/quaternary academic centre serving an urban population and from a review of the literature and (2) to develop treatment guidelines for methicillin-resistant Staphylococcus aureus (MRSA) otorrhea based on the best available evidence.

METHODS: A retrospective analysis of all "ear" cultures from the microbiology laboratory at St. Paul's Hospital, Vancouver, was performed to ascertain a qualitative analysis on the susceptibility and bacteriology data. A systematic review of the literature was performed for all studies examining the bacteriology, susceptibility, and treatment for any MRSA infection producing otorrhea.

RESULTS: Staphylococcus aureus and Pseudomonas aeruginosa (PA) were present in 39.7% and 13.5%, respectively, of ear cultures obtained at our institution versus 9.9 to 54.1% and 25.0 to 48.6% in identified studies in the literature. Methicillin-sensitive Staphylococcus aureus (MSSA) was present more frequently than MRSA (31.2% vs 8.5% at our institution; 16.9% vs 6.9% in the literature). MRSA isolates were often resistant to gentamicin (14.8%) and ciprofloxacin (7.7%) but susceptible to trimethoprim-sulfamethoxazole (TMP-SMX) (85.3%) and fusidic acid (96.3%), suggesting a preponderance of the "community strain" of MRSA.

CONCLUSION:The susceptibility of MRSA to antibiotics in commonly used otic drops (ie, gentamicin and ciprofloxacin) is low. Based on the available data, we suggest an evidence-based approach to the management of MRSA otorrhea considering whether the strain is community or hospital acquired and whether the tympanic membrane is intact.