STABILITY OF GENOMIC DNA FRAGMENT PATTERNS IN METHICILLIN-RESISTANT STAPHYLOCOCCUS-AUREUS (MRSA) DURING THE COURSE OF INTRAHOSPITAL AND INTERHOSPITAL SPREAD

The analysis of genomic DNA fragment patterns has revealed as a powerf ul tool for strain discrimination in Staphylococcus aureus; for use as an epidemiological marker, stability during the course of an outbreak is an essential prerequisite. Genomic DNA fragment patterns (SmaI res triction, pulsed-field electrophoresis) of four different epidemic MRS A strains were compared along with intra- and interhospital and countr y-wide spread over more than 12 months in Germany. Strain I was isolat ed from infections in 8 hospitals. In one hospital a subclone arised w hich differed from the original strain by 4 fragments. Strain II was s pread among 4 hospitals, isolates from three of these hospitals exhibi ted a variability of one to three fragments in the 150-200 kb range, T wo hospitals in the Hannover-area were affected by strain III; in 17 i solates of this strain a variability up to three fragments was found i n the 170-200 kb range. Strain IV was isolated from 19 cases of infect ions in 3 hospitals in Berlin. The fragment patterns were completely s table. When S. aureus strains are typed by genomic DNA fragment patter ns, a variability in a definite range of molecular masses during the c ourse of an epidemic should be taken into consideration.