Methicillin-resistant Staphylococcus aureus and methicillin-resistant coagulase-negative staphylococci from...

To evaluate the incidence and characteristics of carriers of conjunctival methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant coagulase-negative Staphylococci (MRCNS) among preoperative patients at an eye clinic, bacterial growth was studied in 978 conjunctival specimens of 628 preoperative patients without signs of ocular infection. Specimens were evaluated for growth of bacteria on nutrient agar plate, blood agar plate, or chocolate agar plate for 2 days at 37 degrees C. Methicillin resistance was confirmed by disk diffusion and agar screening methods. Susceptibilities of the bacterial strain to ampicillin (ABPC), cefazolin (CEZ), minocycline (MINO), gentamicin (GM), erythromycin (EM), vancomycin (VCM), and ofloxacin (OFLX) were determined by the disk diffusion method. Of the 628 patients (978 eyes), 352 patients (580 eyes) had positive bacterial growth. Among them, 8 (13 eyes) had MRSA growth and 2 (4 eyes) had MRCNS growth. The rate of nasolacrimal duct obstruction was significantly higher in eyes with positive bacterial growth than in eyes with negative growth. Of the 10 patients (17 eyes) with MRSA or MRCNS growth, 8 were older than 80 years, 5 had the same bacterial strains in the anterior nares and throat, 6 had nasolacrimal duct obstruction, 3 had dry eye, and 9 had been recently hospitalized. All 10 bacterial strains were resistant to ABPC, CEZ, and EM, but were sensitive to MINO and OFLX. Five strains were resistant and 5 were sensitive to GM. Two strains examined were sensitive to VCM. After topical antibiotic use for 0.5 to 6 months, the bacterial strains were eliminated. Two of the 17 eyes with MRSA or MRCNS growth did not undergo surgery. No postoperative endophthalmitis developed in 976 of the 978 eyes. Ophthalmologists should be aware that about 50% of preoperative patients without signs of ocular infection may have bacterial growth on the conjunctiva, and that elderly patients with nasolacrimal duct obstruction, dry eye, and recent hospital stays may be carriers of MRSA or MRCNS.