Gram-negative anaerobic rods and cocci

Bacteria from group G− anaerobes belong to species that are difficult to cultivate, therefore it is difficult to identify them as the causative agent of the disease. We include the clinically important genera Bacteroides, Prevotella, Fusobacterium, Mobiluncus a Veillonella.

Gram-negative anaerobic rods

Anaerobic G− bacilli form the normal flora of mucous membranes, often acting as 'secondary pathogens. These are pleomorphic bacteria that are difficult to cultivate. The main pathogenic mechanism is non-specific tissue damage by the acids produced.Bakteroidy a fusobakteria they produce enzymes that facilitate their penetration into tissues and spread.

These bacteria can cause infections anywhere in the human body: oral, pleuropulmonary, intra-abdominal, periodontal, also in the small pelvis and female genital infections. They are an infectious agent even in tissues damaged by injury or surgery. abscesses filled with foul-smelling pus form in the affected area. They are used for therapy lincomycin, chloramphenicol, clindamycin and metronidazole, it is often necessary to choose a ``surgical intervention (incision, drainage).

Bacteroides spp.

Bacteroides spp. Bacteria of the genus Bacteroides are an important part of the natural intestinal flora, some species are potentially pathogenic. Their membrane contains sphingolipids , they have diaminopimelic acid in the wall. Bacteroides are gram-negative pleomorphic rods with rounded ends, usually encapsulated . They are characterized by resistance to bile acids . They massively colonize the large and small intestine, where they play a role in the digestion of complex molecules, the upper respiratory tract. In the vagina, it belongs to the commensal species B. fragilis, B. capillosus or B. ureolyticus . Their endotoxin has little biological activity.

Pathogenicity

The most important pathogens include B. fragilis with a polysaccharide capsule as a virulence factor. It can cause peritonitis , surgical infections in the digestive tract, and appendicitis . It inhibits phagocytosis and, like other species of this genus, is resistant to beta-lactams , aminoglycosides , and recently species resistant to erythromycin and tetracycline have appeared . The genus Bacteroides also includes, for example, B. ovatus , B. vulgatus and B. gracilis .

Prevotella spp.

Prevotella spp. Bacteria of the genus Prevotella are Gram-negative anaerobic fermenting rods related to the genus Bacteroides . Individual species are, for example , P. oris, P. buccae, P. dentalis and P. melaninogenica . Diseases caused by these bacteria include wound , urinary and respiratory infections ( angina , sinusitis ), they can also be an infectious agent in the formation of abscesses in the oral cavity, for example after a human bite. Due to the production of beta-lactamase, they are resistant to beta-lactam antibiotics .

Fusobacterium spp.

Fusobacterium spp.

Mobiluncus spp.

Mobiluncus spp.

Gram-negative anaerobic cocci

The G− group of anaerobic cocci includes Acidaminococcus spp., Megasphaera spp., which are part of the natural bacterial flora of humans. Bacteria of the genus Veillonella are clinically important.

Veillonella spp.

Veillonella spp.