HAMBURGER-ASSOCIATED ESCHERICHIA-COLI O157 H7 INFECTION IN LAS-VEGAS - A HIDDEN EPIDEMIC/

Objectives. This study sought to determine whether a multistate fast f ood hamburger-associated outbreak of Escherichia coli O157:H7 infectio n involved Las Vegas residents as well and, if so, why public health o fficials had not detected it. Methods. A matched case-control study wa s conducted among persons with bloody diarrhea and their healthy meal companions. Hamburger production, distribution, and cooking methods we re reviewed. Unused hamburger patties were cultured, and E. coli O157: H7 isolates were characterized. Local laboratory stool culture practic es were reviewed. Results. Fifty-eight cases of bloody diarrhea were i dentified. illness was associated with eating regular hamburgers (matc hed odds ratio [OR] = 9.0, 95% confidence interval [CI] = 1.02, 433.4) , but 25% of ill persons reported eating only jumbo hamburgers. Regula r and jumbo hamburger patties yielded E. coli O157:H7 indistinguishabl e from the lone clinical isolate. No local laboratory cultured routine ly for E. coli O157:H7 until after the outbreak. Conclusions. A large outbreak of E. coli O157:H7 infections escaped timely notice in Las Ve gas because local laboratories did not culture for this pathogen, Heal th officials should encourage laboratories to screen at least all bloo dy stools on sorbitol-MacConkey medium.