Couples share bacterial microflora, study confirms

San Francisco-A recent study from Sweden has confirmed what many clinicians have suspected: couples routinely share bacterial microflora. In clinical terms, if one partner is treated for a urinary tract infection or similar complaint, the other partner is likely to serve as a reservoir to re-infect the treated person.

That is exactly what happened in 15 healthy heterosexual couples between the ages of 21 and 30 years at Uppsala University in Uppsala, Sweden. Sara Olofsson, PhD, a biomedical researcher in the university's department of medical sciences and the Institute of Medical Biochemistry and Microbiology, took fecal samples from each of the 30 study participants, then treated the women with trimethoprim (TMP [Proloprim]), 160 mg twice daily for 3 days. Additional fecal samples were taken from all 30 volunteers at 1, 2, 4, and 13 weeks after treatment.

All of the samples were cultured for Escherichia coli and the isolates were tested for TMP sensitivity and phenotyped to trace clonal similarities. The results were not a complete surprise, Dr. Olofsson said at the 46th annual Interscience Conference on Antimicrobial Agents and Chemotherapy, but a literature search indicated that transmission between household partners had not been confirmed in prior studies.

Nearly half carry resistant strains

E. coli was found in 28 of the 30 volunteers before antimicrobial treatment. One man and one woman from different couples tested negative for the common bacteria. Overall, 43% of the volunteers (five women and seven men) carried TMP-resistant strains before treatment.

Among 1,413 E. coli isolates, researchers found 27 strains that were shared between volunteers. Of the 27 strains, seven were shared only between couples, 12 only between strangers, and eight strains between both couples and strangers. Of the 15 couples, nine shared at least one common strain and one couple shared five common strains.

By comparing genotypes of isolates found in volunteers before and after antibiotic treatment, Dr. Olofsson said the team found 12 strains that were transmitted between partners. In most cases transmission was from the male partner to the female.

"I am not a physician and cannot make treatment recommendations," Dr. Olofsson said. "But if you are treating one partner for an infection, say, a urinary tract infection, you should probably not be surprised if the infection recurs when you have not also treated the partner."