Summary auto-generated
Serratia marcescens, a gram-negative bacterium, has emerged over 30 years as a significant cause of nosocomial infections. Originally considered a harmless saprophyte, it now causes diverse infections including respiratory tract infections, urinary tract infections, septicemia, meningitis, and wound infections, particularly in hospitalized patients and heroin addicts. The organism survives extreme environmental conditions, including disinfectants and low-nutrient water, and produces unique extracellular products including chitinase, lipase, and serrawettin. Environmental isolates characteristically produce red prodigiosin pigment, though clinical isolates rarely do. The review covers identification challenges with the API 20E system, antibiotic resistance mechanisms (including carbapenem-resistant metallo-β-lactamases and aminoglycoside-modifying enzymes), and virulence factors such as mannose-resistant and mannose-sensitive pili, lipopolysaccharide with 24+ somatic antigens, and surface hydrophobicity. Epidemiological typing methods discussed include serotyping, phage typing, plasmid analysis, ERIC-PCR, and ribotyping, with serotyping being recommended as a suitable first-line approach.
Key findings
- S. marcescens causes diverse nosocomial infections and survives extreme environmental conditions including disinfectants and low-nutrient water through cryptic growth mechanisms
- Resistance to β-lactams (via carbapenem-hydrolyzing metallo-β-lactamases and decreased outer-membrane permeability) and aminoglycosides (via inactivating enzymes) is increasingly common and often plasmid-mediated
- Virulence factors include two types of pili (mannose-resistant and mannose-sensitive) mediating adherence to uroepithelial cells, and lipopolysaccharide with 24+ somatic antigens affecting serum resistance and antibiotic susceptibility
- Unique extracellular products include chitinase, lipase, chloroperoxidase, and serrawettin surfactant, with potential biotechnological applications for antifungal activities
- Serotyping is recommended as a suitable first-line typing method for epidemiological investigations, though RAPD-PCR shows promise for rapid outbreak monitoring
This summary was generated automatically from the article PDF and is not part of the original publication. Refer to the PDF for the authoritative text.
Abstract
Over the last 30 years, Serratia marcescens has become an important cause of nosocomial infection. There have been many reports concerning the identification, antibiotic susceptibility, pathogenicity, epidemiological investigations and typing of this organism. Accurate identification is important in defining outbreaks. The API 20E system has been used widely, but is not individually satisfactory. The growth of S. marcescens in the environment has been investigated in relation to water, disinfectants and plastics such as blood bags. Certain extracellular products are unique to S. marcescens. Pigment (prodigiosin) biosynthesis by S. marcescens has been investigated fully since the emergence of the organism as a cause of infection. Many other aspects of the pathogenicity and virulence of S. marcescens have been studied, including adherence and hydrophobicity, lipopolysaccharide (LPS) and extracellular products. Two modes of adhesion to host epithelial surfaces have been suggested. These are mannose-resistant (MR) pili and mannose-sensitive (MS) pili. LPS, which is responsible for the biological activity of endotoxin, has been investigated fully and 24 somatic antigens have been described. The production of different enzymes by S. marcescens as virulence factors has also been reported, including chitinase, lipase, chloroperoxidase and an extracellular protein, HasA. Antibiotics used to treat serratia infection include β-lactam agents, aminoglycosides and fluoroquinolones and a variety of different resistance mechanisms have been demonstrated. Typing methods used to study the epidemiology of S. marcescens include biotyping, bacteriocin typing, phage typing, plasmid analysis, polymerase chain reaction amplification of enterobacterial repetitive intergenic consensus sequences (ERIC-PCR) and ribotyping. Serological typing has also been used and this method seems to be a suitable first-line typing method for S. marcescens, although some strains remain untypable. RAPD-PCR has also been applied to a small number of isolates and seems to be a promising method, especially for rapid monitoring of an outbreak and tracing the source of initial infection.