Nasal colonization

AD is a 60-year-old woman with a history of poorly controlled diabetes mellitus and MSSA nasal colonization. She weighs 54 kg and is 156 cm tall. She presents today for a hysterectomy. She has no allergies to any medications. The surgeon approaches you for recommendations on prophylactic antibiotic use. 

Mechanism of Action An antibacterial agent that inhibits bacterial protein, RNA synthesis. Less effective on DNA synthesis. Nasal Eradicates nasal colonization of MRSA. Therapeutic Effect Prevents bacterial growth and replication. Bacteriostatic. Pharmacokinetics Metabolized in skin to inactive metabolite. Transported to skin surface removed by normal skin desquamation. 

Nasal colonization of resistant Staphylococcus aureus Intranasal Apply 2 times/day for 5 days. 

Recurrent impetigo, furunculosis, or other staphylococcal infections may be a result of pathogenic nasal carriage of S. aureus. To reduce postoperative complications, eradication of nasal colonization of S. aureus has been extended to colonized health care workers and other susceptible patients.14 Mupirocin has been found to be the most effective topical antibiotic for the elimination and is effective in reducing subsequent infections. When applied intranasally four times daily for five days, it has been shown to reduce nasal carriage for up to 1 year.77... 

These results were in concordance with a study that examined immunocompetent staphylococcal carriers who experienced recurrent skin infections. The study concluded that an initial five-day course of mupirocin followed by a five-day course of nasal mupirocin every month for 1 year reduced the incidence of nasal colonization and in turn lowered the risk of skin infection.78... 

Raz, R. et al., A 1-year trial of nasal mupirocin in the prevention of recurrent staphylococcal nasal colonization and skin infection. Arch. Intern. Med. 156, 1109-1112,1996. 

A third large study found that S. aureus nasal carriers had fewer S. aureus nosocomial infections of any site, but failed to show a reduction in S. aureus surgical site infections, the primary end point of the smdy. The accumulated evidence indicates that patients who stand to benefit from mupirocin prophylaxis are those with proven S. aureus nasal colonization plus risk factors for distant infection or a history of skin or soft tissue infections. General in-patient populations and individuals lacking specific risk factors for S. aureus infection are not likely to benefit from mupirocin prophylaxis. 

Mupirocin is effective in eradicating S. aureus carriage. The consensus is that patients who may benefit from mupirocin prophylaxis are those with proven S. aureus nasal colonization plus risk factors for distant infection or a history of skin or soft tissue infections. 

Mupirocin is a member of a group of iipid acids produced by fermentation of Pseudomonas fluorescens. It can oniy be used topicaiiy because of hydroiysis in vivo that inactivates the drug. It has an intrinsically broad spectrum, but its primary indication is topical use against staphylococcal and streptococcal skin infections, it is commoniy used nasaiiy in infection control programs to eradication nasal colonization by MRSA. Mupirocin binds to bacteriai isoieucyi transfer-RNA synthase, preventing incorporation of isoleucine into bacteriai proteins. Resistance is caused by alterations of the synthase target such that the enzyme still functions but does not bind mupirocin. 

The Cotton Rat as a Model for Staphylococcus aureus Nasal Colonization in Humans... 

Key Words Staphylococcus aureus nasal colonization animal model cotton rat therapy. 

The anterior nares is a primary ecologic niche for Staphylococcus aureus (1,2,3) with 30% of the population being colonized at any one time (1). S. aureus nasal colonization is a well-established risk factor for S. aureus... 

The cotton rat (Sigmodon hispidus) is a well-established model for a number of human pathogens, especially viral respiratory pathogens (14,15). The model detailed in this chapter is an adaptation of a model of S. aureus nasal colonization originally described in mice (16) but now adapted to cotton rats. The cotton rat s nasal histology is comparable to that of humans (17) and pretreatment of cotton rats with antibiotics like streptomycin is not required as it is in mice (16) to establish nasal colonization by S. aureus. We have successfully used the cotton rat S. aureus nasal colonization model to demonstrate the efficacy of lysostaphin as a therapy for S. aureus nasal colonization (18) as well as to study the roles of wall teichoic acid (19) and IsdA and IsdH (20) of S. aureus in nasal colonization. 

This chapter will describe in detail the materials and methods necessary for studying this cotton rat model of S. aureus nasal colonization. These steps include (1) instillation of the S. aureus to establish nasal colonization, (2) treatment of the nares with various therapeutic agents, and (3) recovery and enumeration of colonizing S. aureus. 

If desired, the nasally colonized cotton rats can be treated intranasally to affect nasal colonization (see Note 11). 

Cotton Rat Nasal Colonization by Various Staphylococcus aureus strains... 

AT (transmittance) of 10% is equivalent to 5 x 10 S. aureus per milliliter of buffer at a 1-cm path length, but it is best to determine this empirically for each strain of S. aureus. A dose >10 S. aureus instilled in the nares will ensure consistent nasal colonization even if much of the initial dose is expelled during instillation (see Note 7). Consistent colonization can be achieved with initial inoculums of as low 10 per animal, but care must be taken that the animal does not expel any of the lower inoculum volume. Instillation of <10 S. aureus have not resulted in consistent nasal colonization in our hands. 

Cotton Rats, aureus Nasal Colonization Model... 

Kiser, K. B., Cantey-Kiser, J. M and Lee, J. C. (1999) Development and characterization of a Staphylococcus aureus nasal colonization model in mice. Infect. Immun. 67, 5001-5006. 

Kokai-Kun, J. F., Walsh, S. M., Chanturiya, T., and Mond, J. J. (2003) Lysostaphin cream eradicates Staphylococcus aureus nasal colonization in a cotton rat model. Antimicrob. Agents Chemother. 47, 1589-1597. 

Gluck, U. and Gebbers, J.O. 2003. Ingested probiotics reduce nasal colonization with pathogenic bacteria (Staphylococcus aureus. Streptococcus pneumoniae, and beta-hemolytic streptococci). Am J Clin Nutr 77(2), 517-520. 

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