Bacteria
Mycoplasma pneumoniae are small bacteria from the class Mollicutes that do not have a peptidoglycan cell wall. M. pneumoniae causes tracheobronchitis, which symptoms include a sore throat, cough, fever, and fatigue, as well as a mild form of pneumonia that is often referred to as atypical pneumonia or walking pneumonia. These infections often peak in the summer and early fall and are transmitted when an infected individual coughs or sneezes, spreading respiratory droplets that contain the bacteria. Mild M. pneumoniae infections are usually self-limiting while more serious or prolonged illnesses are treated with antibiotics, though the lack of a cell wall often renders many antibiotics ineffective. Children, members of the military housed in barracks, elderly individuals in nursing homes, and young adults living in dorms are at the greatest risk of developing M. pneumoniae infections.
Chlamydia pneumoniae
Chlamydia pneumoniae are obligate intracellular bacteria in the Chlamydiaceae that can only replicate after they have been taken up by another cell via phagocytosis. This bacterium causes both upper and lower respiratory infections. Upper respiratory symptoms include runny nose, congestion, headache, cough, sore throat, and hoarseness or loss of voice, while lower respiratory infections include bronchitis and atypical pneumonia. C. pneumoniae is spread from coughing or sneezing droplets containing the bacteria and has a relatively long incubation period of 3-4 weeks. Most of these infections are self-limiting but antibiotics can be used to treat the bacteria. C. pneumoniae can be contracted year-round, and those at most risk are children, military personnel, people living in dorms, and the elderly.
Bordetella pertussis
Bordetella pertussis is a gram-negative, non-motile bacterium that is responsible for pertussis, which is also known as whooping cough. The hallmark symptoms of pertussis are a paroxysmal cough followed by a “whooping” sound in addition to fever, runny nose, and sometimes vomiting. The disease has about a week-long incubation period, and coughing fits can last for several weeks. Pertussis is most dangerous to infants, with half of all infected infants requiring hospitalization. To treat pertussis, antibiotics can be administered within 3 weeks of exposure, and there is a vaccine available.