Nosocomial Spread of an Unusual Methicillin-Resistant Staphylococcus aureus Clone That Is Sensitive to All Non-β-Lactam Antibiotics, Including Tobramycin

Between January and December 1999, in Hippokration General Hospital, Thessaloniki, Greece, a large proportion of the methicillin-resistant Staphylococcus aureus isolates (34.4%) exhibited susceptibility to virtually all alternative non-β-lactam antibiotics, including tobramycin. Twenty-five of them were selected randomly for further testing; all belonged to a unique genotype and were characterized as heterogeneously resistant to oxacillin. The aadD gene, encoding tobramycin resistance, failed to be amplified in all cases, indicating absence of the gene or the entire plasmid pUB110 from the mec DNA.