Prevalence of Staphylococcus aureus and Lack of Its Lytic Bacteriophages in the Anterior Nares of Patients and Healthcare Workers at a Rural Clinic

Abstract

Background: Nearly 30% of people in the United States are colonized with Staphylococcus aureus and 1% to 2% with methicillin-resistant Staphylococcus aureus (MRSA) in the anterior nares. However, it is not known if lytic bacteriophages against S. aureus are present in the anterior nares, and if they are, what the prevalence rate is, or if they interfere with S. aureus colonization. The aim of this study was to determine the prevalence of nasal carriage of S. aureus and MRSA and to screen for S. aureus lytic bacteriophages in healthcare environment workers and ambulatory patients.

Within-host diversity of MRSA antimicrobial resistances

“… 4 Free phages were detected in the nasal swabs of nearly half of the patients, which is substantially higher than previous reports. 31 , 38 This may be due to the choice of S. aureus RN4220 as the host strain, as it is negative for known RM systems and therefore susceptible to lytic phage DNA that is normally restricted. 4 It is possible a higher rate of lytic bacteriophages in the nose may be detectable with a broader range or more closely related host strains.…”

“…The bacteriophage isolation assay was modified from Aswani et al 31 Each original nasal swab stored in transport medium (Nuova Aptaca) was placed into a 15 mL Falcon tube containing 2–3 mL of phage buffer (50 mM Tris-HCl pH 7.8, 100 mM NaCl, 1 mM MgSO 4 , 4 mM CaCl 2 and 1 g/L gelatin; Sigma–Aldrich). Suspended swabs were vortexed for 1 min and incubated for 2 h at 37°C at a shaking speed of 200 rpm.…”

Staphylococcus epidermidis Bacteriophages from the Anterior Nares of Humans

“…Seven of the positive samples were from males, and four were from females. Coagulase-negative staphylococci were ubiquitous flora in these subjects (data not shown), while only 24% of the samples grew S. aureus (2). None of the samples yielded phages against S. aureus.…”

“…Phages against S. epidermidis and S. aureus were detected by a modified plate assay technique (2) using S. epidermidis ATCC 35983 and S. aureus ATCC 29213, respectively, as host strains. A 30-l aliquot of each of the nasal swab filtrate sample was spotted onto each strain (2). The 202 samples were also pooled into 8 groups, numbered I to VIII (Table 1), of 25 samples each, and 50-l aliquots of each pool were rechecked for the presence of phages on Trypticase soy agar (TSA) plates incubated at 37°C for 48 h.…”

“…The study design and methodological details are described elsewhere (2). Briefly, the anterior nares of 202 human subjects were swabbed with dry swabs.…”