During Sept 1995, a patient at a hemodialysis center in Montreal, Canada received treatment on a hemodialysis machine to help relieve the effects of kidney disease. The treatment was preformed without any incident. The next day, a 2nd patient received treatment on the same machine. His treatment also went normally, and he returned to his usual activities after the session was completed.

In the following days, both patients experienced bloodstream infections. The had high fever, muscular aches and pains, sore throat, and impaired blood circulation. Because the symptoms were severe, the patients were hospitalized. Both patients had infections of Enterobacter cloacae, gram negative rod. In the following months, an epidemiological investigation reviewed other hemodialysis patients at the center. In all, seven additional adult patients were identified who had used the same hemodialysis machine. All had similar bloodstream infections.

Inspection of the hemodialysis machine indicated the presence of biofilms containing Enterbacter cloacae, specifically where fluid flows. These cultures were identical to those found in the patients. The hospital personnel were disinfecting the machine correctly. The problem was that the valves in the drain line were malfunctioning, allowing backflow of the contaminated material. Health officials began a hospital education program to ensure that further outbreaks of infection were prevented.

1.) Explain what a biofilm is and how it contributed to the infection of the users of the hemodialysis machine.

2.) Suggest how hemodialysis machine originally became contaminated.

3.) Why weren't the other 5 cases of infections correlated with the hemodialysis machine until the epidemiological investigation was begun?

4.) How could future outbreaks of infection be prevented?