MRSA proliferation correlated with fly killing activity. Growth curves of MRSA strains in M9 minimal medium (A) and brain heart infusion (BHI) broth (B) at 25°C for 24 hrs. (C) Growth of MRSA strains within the flies for 24 hrs. A batch of live flies was harvested at 1, 6, 18, and 24 hours post infection and CFU/fly was determined. (D-G) Bacterial counts in different body parts from the flies infected with different MRSA strains at 18 hours post infection: (D) crop; (E) head; (F) wing; (G) leg. The asterisk indicates a statistically significantly difference (p < 0.05) between groups of the high virulence strains and the low virulence strains in bacterial counts in different body parts (Mann–Whitney test). (H-M) Microscopic examination of representative histopathological sections of BHI broth-injected (control) flies (H,K), and M92 (I, L) and USA300-2406 (J, M) infected flies, low (4X) and high magnification (100X) respectively.