Bordetella pertussis. Computer enhanced transmission electron micrograph (TEM) of a section through whooping cough bacteria, Bordetella pertussis. These gram-negative bacteria cause whooping cough (pertussis) mainly in infants, although adults may be affected. This infectious disease of the respiratory tract produces fits of coughing that end in loud inspiratory whoops. Potentially fatal in newborn and premature babies, the bacteria are spread in coughed droplets. Antibiotic drugs have a limited effect in the later stages of the disease, although whooping cough vaccinations are effective. Magnification unknown.