Pathogenic bacteria cause disease in humans. Many different types of bacteria prove harmful to humans, causing infections that range from mild to potentially life threatening. In most cases, pathogenic bacteria can invade different areas of the body causing a range of infections. Staphylococcus aureus, Haemophilus influenzae and Pseudomonas aeruginosa are illustrative examples of harmful bacteria that cause a broad array of human infections.
Staphylococcus Aureus
Staphylococcus aureus is a significant disease-causing bacterium. Enzymes and toxins produced by these bacteria enhance their capacity to invade human tissues, and precipitate key features of S. aureus-associated infections. Enterotoxins cause the symptoms associated with S. aureus food poisoning. Epidermolytic toxins cause peeling of the skin that occurs with staphylococcal scalded skin syndrome. Toxic shock syndrome toxin, or TSST, is the primary actor in the potentially life-threatening toxic shock syndrome. The medical reference text, "Principles and Practice of Infectious Diseases" reports that fever, markedly resistant low blood pressure and multiorgan system failure are the hallmark characteristics of toxic shock syndrome. Other infections that may result from S. aureus include breast and wound infections, endocarditis, pericarditis, pneumonia, lung abscesses, bloodstream infections and joint and bone infections.
Haemophilus Influenzae
Haemophilus influenzae inhabits the nose and throat of up to 75 percent of adults and children, notes Dr. Kenneth Todar in his electronic reference book, "Todar's Online Textbook of Bacteriology." Infections commonly associated with Haemophilus influenzae include middle ear infections, epiglottitis, sinusitis, tracheobronchitis, cellulitis, pericarditis, pneumonia, and bone and joint infections. The Centers for Disease Control and Prevention notes that Haemophilus influenzae type b, or Hib, may cause meningitis and bloodstream infections in infants and young children. The implementation of universal vaccination of infants and children against Hib has led to a marked decline in the incidence of childhood Hib disease in the United States.
Pseudomonas Aeruginosa
Pseudomonas aeruginosa is an opportunistic pathogen. This means the bacteria rarely cause disease unless a precipitating event opens the body to infection. The prevalence of P. aeruginosa in the environment provides ample opportunities for infection. Among intravenous drug users, P. aeruginosa is a common cause of endocarditis, an infection of the interior of the heart including the heart valves. The bacteria gain entry to the bloodstream via contaminated needles and syringes. As explained in "Principles and Practice of Infectious Diseases," the infection can destroy the heart valves and spread elsewhere in the body including the lungs and brain. Among those with a weakened immune system or preexisting lung disease, P. aeruginosa is a common cause of pneumonia. Repeated episodes of P. aeruginosa pneumonia are common among those with cystic fibrosis. P. aeruginosa is also a leading cause of hospital-acquired bloodstream infections, especially among those with cancer, burns or other skin conditions, and surgical or trauma patients.
References
- Todar's Online Textbook of Bacteriology: Staphylococcus aureus and Staphylococcal Disease
- Centers for Disease Control and Prevention: Staphylococcal Food Poisoning
- Todar's Online Textbook of Bacteriology: Haemophilus influenzae and Hib Meningitis
- Centers for Disease Control and Prevention: Haemophilus influenzae Serotype b (Hib) Disease
- "Principles and Practice of Infectious Diseases, Sixth Edition"; Gerald L. Mandell, M.D., et al., Editors; 2004
