That PIM expression levels during early stages of infection may be in part directly or indirectly involved in bacterial growth, virulence, and entry into persistence is still unclear; however, studies show that a PIM-hyperproducing M. tuberculosis strain (ΔRv2623) is hypervirulent in vivo being unable to establish a chronic infection (163), while a PIM-hypoproducing M. tuberculosis strain (ΔRv1747) is attenuated in vivo in mice (169) (Table 1). The gene discussed is PIM1; the disease is infection.