These studies examined a small number of ocular Ct isolates from the major trachoma serotypes and found a small subset of genes in addition to ompA that were associated with differences in in vitro growth rate, burst size, plaque morphology, interferon gamma –(IFNγ) sensitivity and, most importantly, intensity of infection and clinical disease severity in non-human primates (NHPs), suggesting that genetic polymorphisms in Ct may contribute to the observed variability in severity of trachoma in endemic communities [8]. The gene discussed is IFNG; the disease is inclusion conjunctivitis.