THE ROLE OF MRSA (METHICILLIN-RESISTANT STAPHYLOCOCCUS-AUREUS) ADHERENCE AND COLONIZATION IN THE UPPER RESPIRATORY-TRACT OF GERIATRIC-PATIENTS IN NOSOCOMIAL PULMONARY INFECTIONS

The mechanism of nosocomial respiratory infections caused by MRSA (met hicillin-resistant Staphylococcus aureus) in geriatric patients was in vestigated. Seriously iii patients (SIP) undergoing naso-gastric tube feeding or intravenous hyperalimentation and moderately ill patients ( MIP) who were orally fed, were examined for their colonization and inf ection by Staphylococcus aureus (S. aureus) in the respiratory tract. Colonization of MRSA in the upper respiratory tract in SIP was from si x to ten times higher than that in MIP and was associated with a high incidence of MRSA pulmonary infections. In vitro S. aureus adherence t o nasal or oropharyngeal cells demonstrated that bacteria binding to n asal cells was higher, which probably can be interpreted as an elevate d occurrence of S. aureus colonization in the nasal cavity than in the throat. The binding activity of MRSA was not superior to that of MSSA (methicillin-sensitive S. aureus). Though MRSA binding to the nasal c ells from SIP was not higher than those from MIP, MRSA colonization in the upper respiratory tract was more frequently seen in SIP (P <0.01) . A higher incidence of total infectious episodes (P < 0.02-0.001) and more frequent use of antibiotics (P < 0.02-0.001), which were potent against MSSA might be the basis for selection of MRSA in these patient s. In fact, the rate of MRSA colonization on the skin (pressure sores) was also higher in SIP (P < 0.01). A low nutritional state in SIP (P < 0.01-0.02) might also be associated with MRSA colonization. The pres ent results indicate that the high frequency of infections, antibiotic administration, MRSA skin colonization and low nutritional condition, are enhancing factors of MRSA acquisition in the respiratory tract fo r SIP undergoing artificial feeding, in a geriatric hospital.