[The prevalence of methicillin-resistant Staphylococcus aureus phagotype 95 in the Hospitales Vall d'Hebron of Barcelona].
BACKGROUND
In our hospital endemic methicillin resistant Staphylococcus aureus (MRSA) has been documented since 1971, with epidemic and interepidemic periods. During these years phage groups I, I-III, and non-typable were found by the international set of phages Phage group 95 (F95) was unusual between 1986 (when phage typing was first available) and 1991, with prevalence of 5.2% (mean), and 100% of sensibility to methicillin. In November 1991 appeared the first MRSA F95 strain, and its prevalence has been increasing until 1997.


METHODS
We have studied 133 strains of MRSA F95 isolated from 87 patients, 39 of them hospitalized in the General Hospital (HG), 38 in Traumatology Hospital (HT) and 8 in the Children's Hospital (HI). Two of these patients had successive stancies in HG and HT. Antimicrobial susceptibility was determined by the disk diffusion method and microdilution to check oxacillin resistance. Moreover these method we have maked: detection of mecA, phage typing with the international set of phages and study of the PGFE patterns by digestion of chromosomic DNA with Smal.


RESULTS
The percentage of methicillin resistance in F95 strains was increased since the appear of the first strain between 8.3% in 1991 to a maximum of 76.9% in 1995, we had a descens to 13.7% in 1996 but 1997 can back to augment it to 72.5%. MICs for oxacillin of these strains were low (< or = 64 mg/l to 87.4% of strains), and all of them were mecA positive, 78.1% of them were resistant to macrolides, 96.5% to tobramycin and 84.9% to quinolones, but only 10.5% to gentamicin, 4.7% were resistant to cotrimoxazol, 1.2% to fosfomycin and 2.5% to rifampin. All of them were sensible to doxycycline, and vancomycin. The pulse field gel electrophoresis showed 7 restriction patterns in MRSA F95, 73.8% of strains correspond to one of them (B), spreading from the spinal cord injury unit and prevalent in HT; and 10.8% to another (C), the first that appear, spreading from the neurosurgical unit and with high prevalence in HG. 6.9% has pattern J a B subtype that appear in broth HG and HT. Pattern E is prevalent in HI it was spread from neonatology unit.


CONCLUSIONS
The emergence in a Center with endemic resistance of new strains of MRSA, not all of them of the same clone, with characteristic resistance pattern to antibiotics and in convivence with other phage groups is one demonstration of genetic variability of SAMR in our entorn.
del Valle
O
O
Servicio de Microbiología, Hospitales Vall d'Hebron, Barcelona. ovalle@cs.vhebron.es
Trincado
P
P
Martín
M T
MT
Gómez
E
E
Cano
A
A
Vindel
A
A
D001434:Bacteriophage Typing; D001483:Base Sequence; D003428:Cross Infection / Q000453:epidemiology / Q000382:microbiology*; D004269:DNA, Bacterial / Q000235:genetics; D005798:Genes, Bacterial / Q000235:genetics; D006769:Hospitals, General; D006801:Humans; D016106:Methicillin Resistance; D008826:Microbial Sensitivity Tests / Q000706:statistics & numerical data; D008969:Molecular Sequence Data; D015345:Oligonucleotide Probes; D016133:Polymerase Chain Reaction / Q000706:statistics & numerical data; D015995:Prevalence; D013030:Spain / Q000453:epidemiology; D013203:Staphylococcal Infections / Q000453:epidemiology / Q000382:microbiology*; D013211:Staphylococcus aureus / Q000145:classification / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification*
D004269:DNA, Bacterial; D015345:Oligonucleotide Probes