Epidemiological and Genetic Characterization of Methicillin-Resistant Staphylococcus aureus Isolates from the Ear Discharge of Outpatients with Chronic Otitis Media

The origin of methicillin-resistant Staphylococcus aureus (MRSA) strains from otolaryngology outpatients has not been evaluated yet in Korea. We analyzed epidemiologic and genetic characteristics of MRSA isolates from the ear discharge of 64 outpatients with chronic otitis media in a Korean University Hospital during 2004. MRSA strains were grouped as either from the initial visit (n=33) or the follow-up visit (n=31) based on the timing of isolation. Healthcare-associated risk factors were frequently present among patients of the initial visit group, especially prior visit to primary clinic (79%) and antibiotic use (73%). SCCmec typing and multilocus sequence typing results showed that two genotypes, ST5-MRSA-II and ST239-MRSA-III, were prevalent in both the initial visit (73% vs. 24%) and the follow-up visit (55% vs. 42%). Pulsed-field gel electrophoresis identified eight types, including two major types shared by both groups. We conclude that majority of MRSA strains from ear discharge of chronic otitis media belonged to nosocomial clones that might be circulating in the community. This is the first report of the genetic analysis of MRSA strains from otolaryngology practices in Korea

Bacteriophage effectively kills multidrug resistant Staphylococcus aureus clinical isolates from chronic rhinosinusitis patients

Bacteriophage (phage) therapy has been proposed as an alternative to antibiotics. Phages have been shown to kill antibiotic resistant Staphylococcus aureus strains; however, it is unknown whether stress-induced antibiotic tolerance affects S. aureus susceptibility to phages. Our objective was to determine the effectiveness of 2 phages currently in clinical development, against antibiotic-resistant and induced antibiotic-tolerant clinical S. aureus isolates.Antibiotic tolerant S. aureus strains were induced by incubation with increasing concentrations of gentamicin, mupirocin, and ciprofloxacin over time and their susceptibility to 2 clinically relevant phages (Sa83 and Sa87) was assessed. In addition, phage susceptibility was tested in relation to the antibiotic sensitivity of 65 clinical S. aureus isolates, harvested from the sinonasal cavities of chronic rhinosinusitis (CRS) patients. Phage sensitivity was assessed using a plaque spot assay and by measuring optical density values to observe planktonic S. aureus growth in the presence of the phage. Alamar Blue assays were used to assess biofilm viability after phage treatment.Frequency of antibiotic resistance amongst clinical S. aureus isolates was 90.7% (59/65) with 13 of 65 (20.0%) identified as multidrug-resistant. Tolerance to gentamicin, mupirocin, and ciprofloxacin was rapidly induced by incubation with increasing concentrations of respective antibiotics. There was no significant difference in phage sensitivity between antibiotic-sensitive and resistant/tolerant S. aureus clinical isolates in planktonic and biofilm form.Clinical S. aureus isolates from CRS patients have a high (20%) incidence of multidrug resistance. Antibiotic resistance or tolerance did not affect phage susceptibility of those isolates.Guimin Zhang, Yin Zhao, Sathish Paramasivan, Katharina Richter, Sandra Morales, Peter, John Wormald, Sarah Vreugd