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Serratia infections: from military experiments to current practice
1Department of Pathology and Area Laboratory Services, Madigan Healthcare System, Tacoma, WA 98143, USA. steven.mahlen@us.army.mil
Abstract:
Serratia species, in particular Serratia marcescens, are significant human pathogens. S. marcescens has a long and interesting taxonomic, medical experimentation, military experimentation, and human clinical infection history. The organisms in this genus, particularly S. marcescens, were long thought to be nonpathogenic. Because S. marcescens was thought to be a nonpathogen and is usually red pigmented, the U.S. military conducted experiments that attempted to ascertain the spread of this organism released over large areas. In the process, members of both the public and the military were exposed to S. marcescens, and this was uncovered by the press in the 1970s, leading to U.S. congressional hearings. S. marcescens was found to be a certain human pathogen by the mid-1960s. S. marcescens and S. liquefaciens have been isolated as causative agents of numerous outbreaks and opportunistic infections, and the association of these organisms with point sources such as medical devices and various solutions given to hospitalized patients is striking. Serratia species appear to be common environmental organisms, and this helps to explain the large number of nosocomial infections due to these bacteria. Since many nosocomial infections are caused by multiply antibiotic-resistant strains of S. marcescens, this increases the danger to hospitalized patients, and hospital personnel should be vigilant in preventing nosocomial outbreaks due to this organism. S. marcescens, and probably other species in the genus, carries several antibiotic resistance determinants and is also capable of acquiring resistance genes. S. marcescens and S. liquefaciens are usually identified well in the clinical laboratory, but the other species are rare enough that laboratory technologists may not recognize them. 16S rRNA gene sequencing may enable better identification of some of the less common Serratia species.
Insights
Serratia marcescens, once thought harmless, is a significant pathogen causing opportunistic and nosocomial infections. Antibiotic-resistant strains pose a danger, necessitating vigilance in healthcare settings.
Area of Science:
- Medical Microbiology
- Infectious Diseases
- Bacteriology
Background:
- Serratia species, particularly Serratia marcescens, have a complex history, evolving from perceived nonpathogens to recognized human pathogens.
- Historically, S. marcescens was involved in U.S. military experiments due to its pigmentation and presumed lack of pathogenicity, leading to public and military exposure.
- By the mid-1960s, S. marcescens was confirmed as a human pathogen, with S. liquefaciens also implicated in outbreaks.
Purpose of the Study:
- To review the historical context and evolving understanding of Serratia species as human pathogens.
- To highlight the association of Serratia species with nosocomial infections and opportunistic infections.
- To emphasize the clinical significance of antibiotic resistance in Serratia infections and the importance of accurate laboratory identification.
Main Methods:
- Literature review of historical experiments, clinical case reports, and microbiological studies concerning Serratia species.
- Analysis of the role of Serratia species in outbreaks and hospital-acquired infections.
- Discussion of the challenges and advancements in the laboratory identification of Serratia species, including the utility of 16S rRNA gene sequencing.
Main Results:
- Serratia species, especially S. marcescens and S. liquefaciens, are significant causative agents of nosocomial and opportunistic infections.
- Many nosocomial infections are linked to multiply antibiotic-resistant strains of S. marcescens, increasing patient risk.
- Accurate identification of less common Serratia species can be challenging for laboratory technologists, though 16S rRNA gene sequencing offers improved identification.
Conclusions:
- Serratia species are common environmental organisms that frequently cause hospital-acquired infections.
- The increasing prevalence of antibiotic-resistant Serratia strains necessitates heightened awareness and preventative measures in healthcare facilities.
- Enhanced diagnostic methods like 16S rRNA gene sequencing are crucial for the precise identification of all Serratia species, aiding in effective patient management.
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