The study is:
“Non-Invasive Monitoring of Streptococcus pyogenes Vaccine Efficacy Using Biophotonic Imaging,” Faraz M. Alam [pictured here], Colin Bateman, Claire E. Turner, Siouxsie Wiles, Shiranee Sriskandan, PLoS ONE, 8(11), 2013 e82123.
The paper itself says:
“During experiments, bioluminescent S. pyogenes produced an unexpected signal from the genitalia of some mice, corresponding to infection of the lower vaginal tract, suggesting direct inoculation through grooming or airborne transmission within the cage (Figure S1). This underlines the potential for bacteria used in animal experiments to be transmitted beyond the intended site of infection and demonstrates the ability of BPI to identify niches of infection that were not previously suspected.”