Bacteroides Fragilis

Bacteroides Fragilis

Introduction

Bacteroides fragilis is a gram-negative, rod shape anaerobes, non-motile, and non-sporulating. Many of Bacteroides species live in the colon and intestines of humans and animals. Bacteroides fragilis is found predominantly in the colon and intestinal tract along with E. coli and other species present (Mandell, Bennett & Dolin, 2004). Bacteroides fragilis is composed of 30-50% of normal fecal matter in human. Its size is smaller than that of E. coli and they have large vacuoles, which resembles spores but they themselves are non-sporulating organism. They also have enormous capsule with NO cell membrane endotoxin, which limit their pathogenicity. However, they have sphingolipids within their membrane and its peptidoglycan layer contains meso-diaminopimelic acid (Madigan & Martinko, 2005).

Discussion

Bacteroides species are anaerobic bacteria that are predominant components of the bacterial florae of mucous membranes and are therefore a common cause of endogenous infections. Bacteroides infections can develop in all body sites, including the CNS, the head, the neck, the chest, the abdomen, the pelvis, the skin, and the soft tissues. Inadequate therapy against these anaerobic bacteria may lead to clinical failure (Shetab, 1998). Because of their fastidiousness, they are difficult to isolate and are often overlooked. Their isolation requires appropriate methods of collection, transportation, and cultivation of specimens. Treatment is complicated by 3 factors: slow growth, increasing resistance to antimicrobial agents, and the polymicrobial synergistic nature of the infection (Mandell, Bennett & Dolin, 2004).

The B fragilis group, a member of the Bacteroidaceae family, includes B fragilis (causes the most clinical infections), Bacteroides distasonis, Bacteroides ovatus, Bacteroides thetaiotaomicron, and Bacteroides vulgatus. These bacteria are resistant to penicillins, mostly through the production of beta-lactamase (Madigan & Martinko, 2005). They are part of the normal GI florae and predominate in intra-abdominal infections and infections that originate from those florae (eg, perirectal abscesses, decubitus ulcers). Enterotoxigenic B fragilis (ETBF) is also a potential cause of diarrhea. Pigmented Prevotella, such as Prevotella melaninogenica and Prevotella intermedia (which were previously called the Bacteroides melaninogenicus group), Porphyromonas (eg, Porphyromonas asaccharolytica), and nonpigmented Prevotella (eg, Prevotella oralis, Prevotella oris) are part of the normal oral and vaginal florae and are the predominant AGNB isolated from respiratory tract infections and their complications, including aspiration pneumonia, lung abscess, chronic otitis media, chronic sinusitis, abscesses around the oral cavity, human bites, paronychia, brain abscesses, and osteomyelitis. Prevotella bivia and Prevotella disiens (previously called Bacteroides) are important in obstetric and gynecologic infections (Ryan & Ray, 2004).

Description and Significance

Although Bacteroides fragilis makes up from 1-2% of the normal flora in our body, they are responsible for 80% of anaerobic infections. As an anaerobic pathogen, Bacteroides fragilis also competes with other organisms inside the colon/intestinal lumen for nutrients and food. This can be of great benefit to our body because when organisms compete, it decreases the availability of nutrients for other dangerous pathogens to grow, harming our body (Mandell, Bennett & Dolin, 2004). Most of the Bacteroides fragilis was isolated from human stools, and depending on where the infection is located at, different ways of sampling ...