Related Experiment Video
Updated: Jun 27, 2026
06:34
Identification of Rare Bacterial Pathogens by 16S rRNA Gene Sequencing and MALDI-TOF MS
Published on: July 11, 2016
Bacteroides fragilis subspecies in clinical isolates
Annals of Internal Medicine
|May 1, 1977
Summary
The subspecies fragilis of Bacteroides fragilis is the most common cause of infections, particularly in blood cultures. Its encapsulation may contribute to its high virulence.
Area of Science:
- Microbiology
- Infectious Diseases
- Bacteriology
Background:
- Bacteroides fragilis is a common bacterium found in the human gut.
- Understanding the prevalence and virulence of different subspecies of B. fragilis is crucial for treating infections.
Purpose of the Study:
- To determine the prevalence of Bacteroides fragilis subspecies in clinical isolates.
- To investigate the relationship between subspecies, encapsulation, and virulence.
Main Methods:
- Collection and analysis of 103 B. fragilis isolates from infected patients over two years.
- Indirect fluorescent antibody studies to assess encapsulation using antibodies against ss. fragilis capsular material.
Main Results:
- Subspecies fragilis (ss. fragilis) was the most common subspecies, found in 68% of isolates.
- ss. fragilis predominated in various infection sites, including blood, intra-abdominal, and wound infections.
- All tested ss. fragilis strains were encapsulated, while other subspecies were not.
Conclusions:
- Subspecies fragilis is the most virulent subspecies of B. fragilis, likely due to its encapsulation.
- The findings highlight the importance of identifying B. fragilis subspecies in clinical settings for effective treatment strategies.
Related Concept Videos
01:26Bacterial Phylum Proteobacteria
Proteobacteria, one of the largest and most diverse bacterial phyla, encompasses a wide range of Gram-negative bacteria distinguished by their outer membrane composed of lipopolysaccharides. These microorganisms exhibit various metabolic capabilities, including phototrophy, chemolithotrophy, and heterotrophy, and thrive in diverse environments from soil to aquatic systems and host-associated niches. The phylum is divided into six classes: Alphaproteobacteria, Betaproteobacteria,...
01:26Bacterial Phylum Planctomycetes
Planctomycetes are a group of morphologically distinct bacteria predominantly classified into two orders: Planctomycetales and Brocadiales. These gram-negative bacteria exhibit unique features, including division by budding and the presence of stalks or appendages. Their cells are often found in rosette arrangements, and they are notable for possessing an S-layer in their cell envelope, which is relatively uncommon among bacteria. Additionally, Planctomycetes frequently exhibit intracellular...
01:30Bacterial Phylum Spirochaetes
Spirochetes, unique bacteria in the phylum Spirochaetes, are gram-negative, motile, tightly coiled, slender, and flexible. They inhabit aquatic sediments and animals, with some causing diseases like syphilis. Spirochetes are classified into eight genera based on habitat, pathogenicity, phylogeny, and characteristics.Their distinctive motility arises from endoflagella, located within the cell’s periplasm. These endoflagella anchor at the cell poles and extend along the cell length, encased by a...
01:27Bacterial Phylum Firmicutes
Firmicutes is a diverse phylum of Gram-positive bacteria characterized by a low GC content in their genomes. This phylum includes organisms with monoderm or diderm cell envelopes, highlighting a complex evolutionary history. Firmicutes comprises several major orders, including Lactobacillales, Clostridiales, and Bacillales, which exhibit remarkable diversity in their morphology, metabolism, and ecological roles.The order Lactobacillales includes lactic acid bacteria, which are fermentative...
01:26Bacterial Phylum Bacteroidota
The phylum Bacteroidota includes over 700 species classified into four primary orders: Bacteroidales, Cytophagales, Flavobacteriales, and Sphingobacteriales. These gram-negative, non-sporulating rods exhibit saccharolytic capabilities and can be aerobic or fermentative, encompassing obligate aerobes, facultative aerobes, and obligate anaerobes. Many species display gliding motility, though some are nonmotile or use flagella. The genus Bacteroides is well-studied due to its significant role in...
01:24Bacterial Phylum Tenericutes
The phylum Tenericutes, which includes the single class Mollicutes, comprises bacteria that lack cell walls. The term "Mollicutes" derives from the Latin word mollis, meaning "soft." These organisms are among the smallest known and are commonly referred to as mycoplasmas due to the prominence of the genus Mycoplasma, which includes well-known human pathogens. Despite their inability to stain gram-positively (a result of their lack of cell walls), mycoplasmas are phylogenetically related to the...