Because anaerobes are the predominant components of the normal flora of the skin and mucous membranes, they are a common cause of infections of endogenous origin.
[5] The frequency of the host or patient's recovery depends on the employment of proper methods of collection of specimen, their transportation to the microbiology laboratory and cultivation.
The origin of brain abscess is generally an adjacent chronic ear, mastoid, or sinus infection [6] oropharynx, teeth [7] or lungs.
[citation needed] Meningitis due to anaerobic bacteria is infrequent and may follow respiratory tract infection or complicate a cerebrospinal fluid shunt.
Administration of antimicrobials in a high-dose for an extended period of time can offer an alternative treatment strategy in this type of patients and may substitute for surgical evacuation of an abscess.
A substantial improvement in patients' survival rate has occurred after the introduction of computed tomography (CT) and other scans and utilization of metronidazole therapy.
Physical examination generally show signs of peritoneal inflammation, isuch as rebound tenderness, abdominal wall rigidity and decrease in bowel sounds.
Radiographs studies may show free air in the peritoneal cavity, evidence of ileus or obstruction and obliteration of the psoas shadow.
Free gas in the tissues, abscess formation and foul-smelling discharge is commonly associated with the presence of anaerobic bacteria.
[41] Infections which are in the deep tissues (necrotizing cellulitis, fasciitis and myositis) often include Clostridium spp., S. pyogenes or polymicrobic combinations of both aerobic and anaerobic bacteria.
Gas in the tissues and putrid-like pus with a gray thin quality are often found in these infections, and they are frequently associated with a bacteremia and high mortality rate.
The high concentration of anaerobic bacteria in the oral cavity explains their importance in cranial and facial bone infections.
The high number of gut anaerobes in pelvic osteomyelitis is generally caused by their spread from decubitus ulcers sites.
The anaerobic organisms in osteomyelitis associated with peripheral vascular disease generally reach the bone from adjacent soft-tissue ulcers.
are especially common in bite and skull bone infections, whereas members of the B. fragilis group are often found in vascular disease or neuropathy.
[citation needed] Septic arthritis due to anaerobic bacteria is frequently associated with contiguous or hematogenous infection spread, prosthetic joints and trauma.
[citation needed] The type of bacteria involved in bacteremia is greatly influenced by the infection's portal of entry and the underlying disease.
[citation needed] The main factors which predispose to anaerobic bacteremia are: hematologic disorders; organ transplant; recent gastrointestinal, obstetric, or gynecologic surgery; malignant neoplasms intestinal obstruction; decubitus ulcers; dental extraction; sickle cell disease; diabetes mellitus; postsplenectomy; the newborn; and the administration of cytotoxic agents or corticosteroids.
The mortality rate varies between 15% and 30% and can be improved in those who are diagnosed early and receive appropriate antimicrobial therapy and their primary infection when present is resolved.
[citation needed] Condition predisposing to anaerobic infections include: exposure of a sterile body location to a high inoculum of indigenous bacteria of mucous membrane flora origin, inadequate blood supply and tissue necrosis which lower the oxidation and reduction potential which support the growth of anaerobes.
Conditions which can lower the blood supply and can predispose to anaerobic infection are: trauma, foreign body, malignancy, surgery, edema, shock, colitis and vascular disease.
Other predisposing conditions include splenectomy, neutropenia, immunosuppression, hypogammaglobinemia, leukemia, collagen vascular disease and cytotoxic drugs and diabetes mellitus.
A preexisting infection caused by aerobic or facultative organisms can alter the local tissue conditions and make them more favorable for the growth of anaerobes.
[50] The hallmarks of anaerobic infection include suppuration, establishment of an abscess, thrombophlebitis and gangrenous destruction of tissue with gas generation.
Anaerobic bacteria are very commonly recovered in chronic infections, and are often found following the failure of therapy with antimicrobials that are ineffective against them, such as trimethoprim–sulfamethoxazole (co-trimoxazole), aminoglycosides, and the earlier quinolones.
[citation needed] Toxin can be neutralized by specific antitoxins, mainly in infections caused by Clostridia (tetanus and botulism).
[citation needed] The available parenteral antimicrobials for most infections are metronidazole, clindamycin, chloramphenicol, cefoxitin, a penicillin (i.e. ticarcillin, ampicillin, piperacillin) and a beta-lactamase inhibitor (i.e. clavulanic acid, sulbactam, tazobactam), and a carbapenem (imipenem, meropenem, doripenem, ertapenem).
[5] An antimicrobial effective against Gram-negative enteric bacilli (i.e. aminoglycoside) or an anti-pseudomonal cephalosporin (i.e. cefepime) are generally added to metronidazole, and occasionally cefoxitin when treating intra-abdominal infections to provide coverage for these organisms.
Penicillin can be added to metronidazole in treating of intracranial, pulmonary and dental infections to provide coverage against microaerophilic streptococci, and Actinomyces.
Penicillin can be added to metronidazole in the treating dental and intracranial infections to cover Actinomyces spp., microaerophilic streptococci, and Arachnia spp.