Methicillin-Resistant StaPhylococcus aureus from Blood Cultures
Microbiololgical Characteristics and the Background of Patients
1988 Volume 62 Issue 6 Pages 564-589
Details
1988 Volume 62 Issue 6 Pages 564-589
Staphylococcus aureus used in this study were isolated from blood cultures of inpatients at the Central Clinical Labolatory, Teikyo University Hospital from January 1984 to April 1986. Resistant patterns to various antibiotics, phage type, coagulase type, TSST-1 productivity of these strains were investigated. In addition, background and administrated antibiotics for the patients were analyzed with Multivariate-analysis.
1. In the above period, 81 strains of S. aureus were isolated and 57 strains of them (70.4%) were MRSA.
2. Of this MRSA, 55 strains (96.5%) were resistant to aminoglycosides (AGs). According to previous studies in our hospital, except for production of 3'-phosphotransferase (3'-APH), AGsresistant MRSA were possible to classify into 2 groups. The one is a GM-resistant MRSA that produces bifunctional enzyme having 2′′-phosphotransferase and 6'-acetyltransferase (2′′-APH+6'-AAC) activity. The another one is a TOB-resistant MRSA that produces 4'.4′′-adenylyltransferase (4', 4′′-AAD). 8 strains that produce simultaneously bifunctional enzyme and 4', 4′′-AAD were newly found out in this studies (GMr-+TOBr--MRSA).
3. GMr-+TOBr--MRSA were classified into 2 groups; 3 strains were similar to GMr--MRSA and the others were similar to TOBr--MRSA in respect to phase type, coagulase type and toxin production. From these results, it was suggested that hospitalized MRSA are changing its properties gradually.
4. MRSA positive patients were classified into 3 groups;
1) Age advanced patients affected to brain disorders, malignant tumor, cardiac disorder or diabetis mellitus and fell into so-called immunocompromised host.
2) High risk infants such as congenital immunodeficiency syndrome and low birth weight.
3) Age unrelated patients (but many cases were the twenties) encountered multiple trauma or burn.
Grpoup 1 and 2 recieving radical antibiotic therapy were becoming S. aureus positive over one week hospitalization. In contrast, group 3 become S. aureus positive in a short duration without using anti-biotics.
5. Significant high frequency between MRSA positive cases pre-administrated 2nd & 3rd generation cephems and unrecieved cases, was proved by statistical analysis using the Hayashi's Quantification 2.
6. GMr--MRSA was isolated predominantly from the cases admitted to non-surgical wards and TOBr--MRSA was from the cases of surgical wards respectivelly. The reason why the above phenomenon observed was speculated that many cases of surgical wards were administrating various antibiotics in combination.
7. Post-administrated antibiotics for MRSA infection were also used in combinations of over 2 kinds of antibiotics for almost all cases. By quantification analysis, it was suggested that some of them are effective partially. However, none of them were found to be such as clinicaly effective fully to MRSA infections. From the above findings, it was indicated that MRSA infection if occured, is very difficult to recover.
