Infection caused by Proteus mirabilis strains with transferrable gentamicin-resistance factors.

During a period of 10 weeks, four patients in one hospital became infected with gentamicin-resistant Proteus mirabilis. In two of them septicaemia associated with indwelling catheters developed, one had urinary tract and wound infections, and in the fourth patient the organism was isolated from a superficial wound. The P. mirabilis strains showed multiple drug resistance. Strains form the first three patients were apparently identical and were sensitive to tobramycin. Their gentamicin resistance was not transferable to Escherichia coli K12, but could be transferred to another strain of P. mirablilis (PM13-3). The fourth strain was resistant to tobramycin; its gentamicin/tobramycin resistance was transferable to E. coli K12.