Gram-negative bacteria are characterized by their cell wall structure, which differs significantly from that of gram-positive bacteria. The cell wall of gram-negative bacteria consists of a thin peptidoglycan layer surrounded by an outer membrane containing lipopolysaccharides, which makes them more resistant to antibiotics compared to gram-positive bacteria. These organisms are commonly found in various environments and can cause a range of infections. Here is a list of notable gram-negative bacteria, categorized by their typical clinical associations:
Enterobacteriaceae Family
- Escherichia coli (E. coli) - Causes urinary tract infections, neonatal meningitis, gastroenteritis.
- Klebsiella pneumoniae - Leads to pneumonia, bloodstream infections, wound or surgical site infections.
- Salmonella spp. - Associated with food poisoning and typhoid fever.
- Shigella spp. - Responsible for shigellosis (bacillary dysentery).
- Proteus mirabilis - Known for urinary tract infections and kidney stones.
- Enterobacter spp. - Can cause various infections, including urinary tract infections, respiratory tract infections.
- Serratia marcescens - Causes nosocomial infections (hospital-acquired), particularly urinary and respiratory tract infections.
Non-Enterobacteriaceae
- Pseudomonas aeruginosa - Often associated with hospital-acquired infections, including pneumonia, urinary tract infections, and bacteremia.
- Haemophilus influenzae - Can cause meningitis, pneumonia, otitis media, and epiglottitis.
- Neisseria meningitidis - Leads to meningitis and meningococcemia.
- Neisseria gonorrhoeae - Causes gonorrhea, a sexually transmitted disease.
- Helicobacter pylori - Linked to peptic ulcers and gastric cancer.
- Campylobacter jejuni - Known for causing gastroenteritis.
- Acinetobacter baumannii - Associated with a range of infections, particularly in healthcare settings.
Other Gram-Negative Bacteria
- Bordetella pertussis - Causes whooping cough.
- Bacteroides fragilis - Found in the gut, can cause peritonitis and abscesses.
- Legionella pneumophila - Responsible for Legionnaires’ disease.
- Vibrio cholerae - Causes cholera.
- Francisella tularensis - Causes tularemia.
- Brucella spp. - Leads to brucellosis.
- Yersinia pestis - Causes plague.
Zoonotic Gram-Negative Bacteria
- Bartonella henselae - Causes cat-scratch disease.
- Leptospira spp. - Responsible for leptospirosis.
Atypical Gram-Negative Bacteria
- Mycoplasma pneumoniae - Causes atypical pneumonia (lacks a traditional cell wall).
- Chlamydia trachomatis - Causes chlamydial infections including trachoma and sexually transmitted infections.
Mycobacteria (Acid-Fast)
- Mycobacterium tuberculosis - Causes tuberculosis.
- Mycobacterium leprae - Causes leprosy.
Spirochetes
- Treponema pallidum - Causes syphilis.
- Borrelia burgdorferi - Causes Lyme disease.
Each of these bacteria has unique characteristics and can be involved in various clinical scenarios. Their relevance in a clinical setting varies, with some being common causes of community-acquired infections and others being notable for hospital-acquired infections or specific diseases. Understanding their pathogenic mechanisms, antibiotic resistance patterns, and associated conditions is crucial in the medical field
Others includes:
- Vibrio vulnificus - Can cause wound infections and septicemia, especially after exposure to contaminated seawater.
- Burkholderia cepacia - Known for causing respiratory infections in people with cystic fibrosis.
- Stenotrophomonas maltophilia - Associated with respiratory and bloodstream infections, particularly in immunocompromised individuals.
- Moraxella catarrhalis - Common cause of otitis media in children and respiratory tract infections in adults.
- Providencia stuartii - Can cause urinary tract infections and other nosocomial infections.
- Hafnia alvei - Typically found in the gut, occasionally causes opportunistic infections.
- Morganella morganii - Known for urinary and wound infections.