Enteric bacteria, classified in the order Enterobacterales, are Gram-negative, facultatively anaerobic rods that inhabit the intestines of humans and animals. Many members are part of the normal gut flora, while others are important pathogens responsible for enteric and systemic infections.
Explanation
The order Enterobacterales encompasses a diverse group of bacteria formerly grouped as Enterobacteriaceae. These organisms are typically oxidase-negative, catalase-positive rods that ferment glucose and reduce nitrate to nitrite. Most have peritrichous flagella and are motile, though some such as Klebsiella are non-motile. Their cell walls contain lipopolysaccharide endotoxin, and many produce fimbriae and capsules that facilitate adherence and virulence. Enteric bacteria live in the gastrointestinal tract, where commensal species like Escherichia coli synthesize vitamins and compete with pathogens. Pathogenic members cause diseases including gastroenteritis, urinary tract infections, septicemia and pneumonia. Salmonella enterica and Shigella species cause invasive intestinal infections; Yersinia pestis, a member of the order, causes plague. These bacteria adapt to varied environments and can grow aerobically or anaerobically by fermentation. Many species acquire antimicrobial resistance via plasmids and integrons, posing treatment challenges. Detection and identification rely on culture characteristics, biochemical tests and molecular methods such as 16S rRNA sequencing and MALDI‑TOF mass spectrometry.
Members and significance
Prominent genera within Enterobacterales include Escherichia, Salmonella, Shigella, Klebsiella, Enterobacter, Citrobacter, Proteus, Serratia and Yersinia. Escherichia coli, the most abundant commensal in the human colon, can also cause neonatal meningitis and travelers’ diarrhea via toxigenic strains. Salmonella enterica serovars Typhi and Paratyphi cause enteric fever, while non-typhoidal serovars lead to foodborne gastroenteritis. Klebsiella pneumoniae is an opportunistic pathogen associated with pneumonia and liver abscesses, and its hypervirulent strains feature thick capsules. Proteus species are known for swarming motility and involvement in urinary tract infections. Many enteric bacteria contaminate food and water; their presence in drinking water indicates fecal pollution. Monitoring and controlling these organisms are essential for public health and infection prevention.
Enteric bacteria of the order Enterobacterales form a broad group of intestinal Gram-negative rods that play roles as commensals and pathogens. Understanding their biochemical traits and clinical significance aids in diagnosis, treatment and contamination control.
Related Terms: Escherichia coli, Salmonella, Enterobacteriaceae, Gram-negative, Facultative anaerobe