Background. Pyomyositis is typically caused by gram-positive bacteria, especially Staphylococcus aureus. Few cases of Escherichia coli pyomyositis have been reported, including only 1 involving a patient with a hematologic malignancy. Methods. The clinical microbiology database at The M. D. Anderson Cancer Center (Houston, TX) was reviewed for the period January 2003 through December 2007 to identify cases of E. coli pyomyositis. Clinical characteristics, laboratory and radiologic findings, treatment, and outcomes were recorded. Available isolates un-derwent phylogenetic group determination, virulence genotyping, multilocus sequence typing, repetitive-element polymerase chain reaction, and pulsed-field gel electrophoresis. Results. Six cases of E. coli pyomyositis were identified. All patients were receiving chemotherapy for a he-matologic malignancy; 5 were severely neutropenic. Three patients became hypotensive, 2 required intensive care, and 2 (33%) died, despite receiving carbapenem therapy. All E. coli isolates were fluoroquinolone resistant; 55% produced an extended-spectrum lactamase (ESBL). Five of 6 available isolates belonged to phylogenetic group B2, had similar virulence factor profiles, exhibited > 95% similar repetitive-element polymerase chain reaction profiles, and represented sequence type ST131; however, all had unique pulsed-field gel electrophoresis profiles. Conclusions. E. coli pyomyositis has emerged as a serious problem among our patients with hematologic malignancy. It usually is caused by members of E. coli ST131, a recently identified cause of fluoroquinolone-resistant, ESBL-positive E. coli infection worldwide. Awareness of this emerging syndrome and the usual causative agent is important to ensure appropriate management when febrile, neutropenic patients with hematologic ma-lignancy exhibit signs of localized muscle infection.
Bibliographical noteFunding Information:
Potential conflicts of interest. J.R.R. has been a consultant for Ortho-McNeil and has received grants or contracts from Merck, Bayer, Procter and Gamble, Wyeth-Ayerst, and Rochester Medical. D.P.K. is an investigator for Merck and a consultant for Merck and Schering-Plough; has received grants and research support from Merck, Enzon, and Fujisawa/Astellas; is in the speaker’s bureau of Merck, Pfizer, Enzon, and Fujisawa/Astellas; has been a speaker for Enzon and Fujisawa/Astellas; and is on the advisory board of Merck and Schering-Plough. I.I.R. is a consultant for Clorox, Cubist, and Cook; has received grants from Cubist, Schering-Plough, Ver-sicor, Enzon, Pfizer, Wyeth, and Cook; is on the speaker’s bureau of Merck, Schering-Plough, Pfizer, and Cook; and has royalties related to patents licensed to American Medical Systems, Horizon Medical Products, and TyRx on which he is a coinventor. H.L.D. has consulted with, has received honoraria for speaking, and has received research grants from Salix Pharmaceutical Company; has received a consulting fee from Romark Institute for Medical Research; has received research grants from Optimer Pharmaceuticals and IOMAI Corporation; has received honoraria for consulting and/or speaking from McNeil Consumer Healthcare and Merck Vaccine Division. All other authors: no conflicts.