Mixed anaerobic infection

Introduction to mixed anaerobic infection Hundreds of normal anaerobic flora that are not spore-forming in the skin, mouth, intestines, and vagina, if this symbiotic relationship is compromised (eg, surgery or other trauma, poor blood supply or tissue necrosis), Some strains can cause infections with high morbidity and high mortality. After entering these ways, they can spread to the distant place with blood flow, because aerobic and anaerobic bacteria can often be found in the same infection site. Infections may be mixed, and anaerobic bacteria may be overlooked unless separated and cultured in an appropriate manner. However, anaerobic bacteria may be the main pathogens in the pleural cavity and lung, intra-abdominal, gynecological, central nervous system, upper respiratory tract infections and skin diseases and bacteremia. basic knowledge The proportion of illness: 0.005% Susceptible people: no specific population Mode of infection: non-infectious Complications: shock

Mixed anaerobic infection cause

Pathogen species (30%):

Pathogenic Gram-positive anaerobic bacteria are Digestive and Streptococcus pneumoniae, which are part of the normal flora of the mouth, upper respiratory tract and large intestine. The main Gram-negative anaerobic bacteria are Bacteroides fragilis, Bacteroides melanogis and Bacteroides fusiformis. The Bacteroides fragilis is part of the normal colonic flora, including the most commonly isolated anaerobic pathogens from intra-abdominal infections.

Source of infection (30%):

The characteristics of anaerobic infection are mostly endogenous. The infection rate of periodontitis and root canal anaerobic bacteria is over 96%, and the mixed infection rate of anaerobic and aerobic bacteria in the perianal, abdomen and lung is 70%. More than %; anaerobic infection rate of lung infection and lung abscess is more than 40%, and pathogens are mostly Gram-negative anaerobic bacteria.

Susceptible population (10%):

When the body's immune function is low, patients such as cancer and bone marrow transplantation are prone to bacteremia, and patients in the intensive care unit are prone to iatrogenic infections due to long-term hospitalization.

Mixed anaerobic infection prevention

In order to prevent bacteremia and metastatic disease, preventive measures should include early treatment of localized infections: debridement of necrotic tissue, removal of foreign bodies, reconstruction of blood circulation and early antibacterial treatment of wounds, early surgical exploration, drainage, closure of intestinal perforation and Antibacterial therapy for penetrating abdominal injuries. Patients undergoing elective colon surgery should be prepared with neomycin or erythromycin. Prophylactic parenteral antibiotics should be given immediately after surgery. Cefoxitin or metronidazole should be used alone. Or clindamycin combined with gentamicin or tobramycin can be used to prevent a single dose of antibiotics before debridement surgery, continue to give antibiotics for 24 hours after surgery, the postoperative infection rate can be 20% ~30% fell to 4% to 8%.

Mixed anaerobic infection complications Complications

Bacteremia with concurrent mixed anaerobic infection can cause fever, chills and critical illness, shock, although extremely rare in pure Bacterial septicemia, but intravascular diffuse coagulation can occur in Clostridium-like septicemia.

Mixed anaerobic infection symptoms common symptoms abscess bacteremia intravascular coagulation septic thrombosis

Anaerobic infections usually have three characteristics: (1) easy to form local empyema or abscess. (2) The hypoxic partial pressure and low oxidation-reduction potential occurring in avascular or necrotic tissue are essential for the survival of anaerobic bacteria. (3) Once bacteremia occurs, only diffuse intravascular coagulation (DIC) and purpura are rare.

The following points can be used as clinical clues for anaerobic infections: infection of adjacent mucosal surfaces with anaerobic bacteria, ischemia, tumors, penetrating trauma, foreign bodies, visceral perforation, involvement of skin, subcutaneous tissue, tendons Membrane and muscle diffuse gangrene, pus or infected tissue with fecal odor, abscess formation, gas in the tissue, septic thrombophlebitis, antibiotic treatment without anti-anaerobic bacteria.

Examination of mixed anaerobic infections

All specimens should be Gram stained and aerobic culture. Anaerobic culture should be placed in special medium, incubated for 48~72 hours, and then inspected. It may not be susceptibility data after 1 week after initial culture. The oxybacteria susceptibility test should be rigorous and subject to confirmation by the National Clinical Laboratory Standards Steering Committee. However, if the strain is known, the susceptibility can be presupposed, so many laboratories do not routinely test anaerobic susceptibility. .

If the pus Gram stain of the infected site shows mixed pleomorphic flora, anaerobic infection may be considered. Because Gram stain is difficult to find Bacteroides, it is necessary to carefully observe the characteristic changes. Filamentous bacillus. If the infected part is taken as Gram stain for the mixed flora, and the tissue culture with obvious necrosis only sees -hemolytic streptococcus or a single aerobic bacteria such as E. coli, or even no bacterial growth, it should be considered. The bacteriological technique that may be the delivery or culture of the specimen is improper.

Diagnosis and identification of mixed anaerobic infection

diagnosis

Diagnosis can be based on medical history, clinical symptoms, and laboratory tests.

Differential diagnosis

Mixed anaerobic infections are mainly identified by aerobic bacteria and can be identified by bacterial culture.

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