The cost of treating HAIs in the NHS is about £180m per year
The number of C. difficile cases in Scottish hospitals has fallen by just over 40% in a year, according a new report.
Progress has also been made in reducing MRSA superbugs, with a year-on-year fall of about 14% since 2005.
The figures have been revealed in Health Protection Scotland's (HPS) first annual report on superbug rates.
Professor Jacqui Reilly, from HPS, said "real inroads" had been made in cutting healthcare-associated infections.
A total of 3,625 C. difficile cases in patients aged 65 and over were reported in 2009.
The figure represents a "significant" decrease of 43% compared to the previous year, according to the report.
New cases of the MRSA superbug have been steadily falling over the past four years, the figures show.
Just over 530 were identified last year, with a 14.5% year-on-year fall since 2005.
Separate statistics show cases of C. difficile continued to decline during the last quarter of 2009.
A total of 672 new cases of C. difficile were reported in elderly patients between October and December, which is the lowest since records were first collected in 2006.
According to the most recent estimate, the cost of treating HAIs in the NHS is about £180m per year.
Professor Reilly, head of the healthcare-associated infection and infection control group at HPS, said there was still a "substantial burden" of the infections occurring every year.
She added: "Efforts should continue to focus on preventing and controlling these infections to the irreducible minimum."