Serratia bacteria are often present in the bodies of healthy people, without causing any symptoms or problems, reports the Merck Manual. In people who have reduced resistance, are in the hospital, or use devices such as catheters or airway tubes, Serratia may cause infections of the urinary tract or respiratory tract. Cultures of the tissue affected by the infection are necessary to confirm Serratia infection.
Serratia bacteria have close links to Klebsiella and Enterobacter bacteria, notes the Merck Manual. Doctors treat all three bacteria with the same kinds of antibiotics, but they tend to cause different kinds of infections. Serratia bacteria are more likely to infect the urinary tract but can also affect the respiratory tract and surgical incision sites.
Many strains of Serratia bacteria have a distinctive red color, and scientists once believed that the bacteria was a nonpathogen, according to Clinical Microbiology Reviews. Serratia was thus instrumental in medical research and in military research intended to study the possible effects of bioterrorist attacks. Since that time, doctors and researchers have learned that Serratia can cause many illnesses, including urinary tract infections, meningitis, endocarditis, pneumonia and wound infections. Some antibiotic-resistant strains of Serratia exist as of 2015. These strains most often spread in hospitals and are particularly difficult to treat.
When a doctor suspects a Serratia infection, he may confirm the infection with cultures, explains the Merck Manual. Depending on the location of the infection, the doctor may take samples of sputum, lung secretions, urine, blood or tissue. He stains the cultures and examines them under a microscope. Samples may also go through testing for susceptibility to particular antibiotics, so the doctor can prescribe an effective treatment.