In summary, there is no reliable evidence to say that grapefruit-seed extract has any disinfection efficacy. It was found out that some commercial products have been adulterated with artificial disinfectants.
Some sources mention that grapefruit-seed extract has been used in hospitals in the United states; not to prevent/treat skin infections but to disinfect laundry and carpets.
According to Natural Medicines Comprehensive Database, there is insufficient evidence to say that grapefruit-seed extract is effective in prevention or treatment of infections or other skin conditions.
This review Grapefruit Seed Extract as an Antimicrobial Agent (ReliasMedia, 2009) provides summaries of various studies - I added the links:
Researchers at a German Institute of Pharmacy tested six commercially
available grapefruit seed extracts.10 Five of the six products showed
strong antimicrobial activity against a range of bacteria, yeast, and
other microbes. However, further analysis of these five active samples
found they contained between 1.25% and 10% benzethonium chloride. The one sample which contained no benzethonium chloride also showed no
antimicrobial activity. The researchers made their own grapefruit seed
extract and it had no antimicrobial activity. (Pharmazie, 1999)
Of nine commercial grapefruit seed extract products purchased in the
United States, seven contained benzethonium chloride (0.3-22%), three
contained triclosan (0.01-1.13%). (Pharmazie, 2007)
Another investigation was conducted into grapefruit seed extracts used
in farming as organic antimicrobial sprays.4 Nine products were
tested, of which seven contained various synthetic chemicals, most
commonly benzethonium chloride. (Journal of Agricultural and
Food Chemistry, 2006)
In the most recent analysis published, 41 various products were
purchased in Japan.12 These included food additives, cosmetics,
dietary supplements, and disinfectant sprays. All but three
contained one or more synthetic antimicrobials. (Shokuhin
Eiseigaku Zasshi. 2008)
According to another review: The Adulteration of Commercial “Grapefruit Seed Extract” with Synthetic Antimicrobial and Disinfectant Compounds (American Botanical Council, 2012):
A significant amount, and possibly a majority, of ingredients, dietary
supplements and/or cosmetics labeled as or containing grapefruit seed
extract (GFSE) is adulterated, and any observed antimicrobial activity
is due to synthetic additives, not the grapefruit seed extract itself.