Nocardia bacteria, computer illustration. These are Gram-positive branching filamentous bacteria that fragment into bacillary and coccoid forms, and cause nocardiosis (bacteria formerly identified as Nocardia asteroides complex, that are now separated into several species based on molecular studies, such as N. abscessus, N. cyriacigeorgica, N. nova and other), a rare pulmonary infection that affects people with weakened immune systems. Another type (N. brasiliensis and other) causes actinomycetoma, a tropical skin and bone infection.