Men's offices are crawling with more bacteria than women's workplaces, according to researchers who investigated the microbes where we spend much of our time.

Scientists actually know little about what types of bacteria and viruses grow where we live, work and play, even though we spend about 90 per cent of our time indoors. Understanding more could be useful for medical purposes.

Office phones were abundant in the harmless bacteria. (Charlie Neibergall/Associated Press)

In Wednesday's issue of the journal PloS One, Scott Kelley, a biology professor at San Diego State University and his co-authors surveyed human skin, nasal, oral and intestinal bacteria from 90 offices in New York, San Francisco and Tucson, Ariz.

The same five surfaces were sampled with sterile swabs:

• Chairs.
• Phones.
• Computer mice.
• Computer keyboards.
• Desktops.

Men's offices had up to 20 per cent more bacteria than women's offices, the researchers found.

"The differences between contamination levels in the offices of men and women may be explained by differences in hygiene," the study's authors said.

"Men are known to wash their hands and brush their teeth less frequently than women and are commonly perceived to have a more slovenly nature."

Spreading bacteria

On average, men are larger than women with more skin surface area for bacteria to grow on, they said. Men may also shed more bacteria into their surroundings.

The findings seemed true for Pat Cochrane, a security guard at an office building in Halifax.

"I'd say any girls I know are definitely cleaner than me," Cochrane said with a laugh. "But I mean I'm not filthy or anything."

Office spaces offer a rich breeding ground for neutral or even helpful bacteria, Kelley said. Chairs and phones had a high abundance of bacteria in the study.

"If you're taking a phone [call], picking up the phone, talking into it, stuff is coming out of your mouth in the little specks of food and saliva and then your hands touching the phone itself, you're transmitting bacteria from your hand to the phone or the mouse, so you’re really spreading a lot of this around," Kelley said in an interview.

Our shoes seemed to serve as another source of soil bacteria.

The researchers hope to use the microbial information they gathered to understand the differences between "healthy" buildings and those that could contribute to sick building syndromes.

Investigators weren't able to tell what species or strain the bacteria were, although many of these types live on our skin and in our noses and mouths.

They said most of the human-source bacteria found were harmless. Some staph and strep species could pose a problem for people who are severely immune compromised.

The research was funded by grants from San Diego State University, Clorox Corp. and the Alfred P. Sloan Foundation.

With files from CBC's Pauline Dakin