The importance of clinical testing for anaerobic bacteria

Anaerobic bacterial testing is an important component of clinical microbiological testing. Under anaerobic (or low oxygen) conditions,Bacteria that can only reproduce under conditions of low redox potential are called anaerobic bacteria.

Anaerobic bacteria dominate the normal microbiota in the human gut, oral cavity, upper respiratory tract, urogenital tract, and other areas,Long term use of broad-spectrum antibiotics, hormones, immunosuppressants, etcWhen there is a dysbiosis of the microbiota or a decrease in the body's immune system, or when bacteria enter abnormal habitats, anaerobic bacteria may cause severe or even fatal endogenous anaerobic bacterial infections. Anaerobic bacterial infections often occur in deep wounds,But it can also be accompanied by facultative anaerobic and aerobic bacteria invading any organ and tissue of the human body,When routine bacteriological examinations such as deep abscess and sepsis are negative,Often caused by anaerobic bacterial infection. According to literature reports, the infection rate of anaerobic bacteria in periodontitis and root canal inflammation is as high as96.67%～100%[1,2];The rates of anaerobic bacterial infections in the perianal, abdominal, and pulmonary regions are also relatively high,The mixed infection rate of anaerobic and aerobic bacteria reaches72%～91.7%[1,3];The rates of anaerobic bacterial infections in lung infections and lung abscesses are40.1%～84.2%[4,5];The majority of pathogenic bacteria are Gram negative anaerobic bacteria,Among them, the genus Bacteroidetes is the dominant bacterium;When the immune function of the body is low,Patients with diseases such as cancer and bone marrow transplantation are prone to bacteremia[6-8];Patients in the intensive care unit due to long-term hospitalization,Easy to cause iatrogenic infections. Among various infectious diseases in gynecology and obstetrics100%,Perirectal abscess has77%Can detect anaerobic bacteria,And a considerable number of cases are caused by single anaerobic bacterial infections[1]The infection of Clostridium difficile in antibiotic associated diarrhea is often transmitted through contact,Hospital infection outbreak occurs,Serious cases can lead to death[9]Therefore, anaerobic bacteria testing should be given high attention.

To comprehensively assist clinical diagnosis,To prevent infectious diseases from being missed or misdiagnosed, most hospital microbiology laboratories now carry out anaerobic bacteria identification and drug sensitivity.

To successfully isolate anaerobic bacteria, the first step is to correctly select the specimen:The following bacteriological indicators are helpful for selecting specimens for anaerobic culture:（1）Puss from deep wounds or soft tissue abscesses,Especially when accompanied by a foul odor or containing sulfur particles. （2）Suspected necrotic tissue or lesion clearance material obtained from gas gangrene or rare severe gas production or necrotic infection. （3）Materials obtained from infected lesions in mucosal areas. （4）Material obtained from abscesses in the brain, lungs, liver, or other organs, or from abscesses in the abdominal cavity, perianal region, septum, or other parts. （5）Aspiration fluid of infection foci in sterile area,Including blood, cerebrospinal fluid, ascites, pleural fluid, synovial fluid, or amniotic fluid. （6）Materials obtained from human or animal bites on infected lesions. （7）Exudates that turn black or emit red fluorescence when exposed to ultraviolet light. （8）Under Gram staining microscope,Observed materials with anaerobic bacterial morphology. （9）Suspected food causing botulinum toxin poisoning.

The collection and transportation of specimens are crucial for the success of anaerobic bacterial culture, and it should be noted that specimens cannot be contaminated by normal bacterial communities; Try to avoid contact with air as much as possible.

Collecting specimens correctly:Anaerobic bacteria are a part of the normal microbiota in many parts of the human body, such as the skin, pharynx, intestines, and urogenital tract,Therefore, the following materials do not require anaerobic cultivation:（1）Pharyngeal, nasal, urethral, vaginal or rectal swabs, dental swabs. （2）Cough up phlegm,Secretions collected through bronchoscopy,Urine, feces, and stomach contents expelled or exported. （3）Prostate secretion. To eliminate or minimize the contamination of anaerobic bacteria in the normal microbial community,Extracting samples with a syringe is better than using a swab,Especially suitable for the following clinical situations:（1）Extract pus from an unopened abscess. （2）Chest fluid extracted through thoracentesis. （3）Urine (extracted through bladder puncture above the pubic symphysis or collected through a nephrostomy tube). （4）Pulmonary secretions (extracted by tracheotomy). （5）Abdominal fluid (extracted by puncture). （6）Extract cerebrospinal fluid through lumbar puncture. （7）Sinus specimens can be inserted into small catheters,Suck out with a syringe. Alternatively, samples can be taken from the site of sinus tract injury for biopsy. The gas inside the syringe and needle should be completely expelled, and the needle should be inserted into a sterile rubber stopper to isolate the air before being sent to the laboratory. If a swab must be used,It should be inoculated into a suitable culture medium as soon as possible. Maintain an anaerobic state during transportation. The culture medium should not contain heparin,Because it inhibits bacterial growth.

After receiving the specimen, the laboratory20～30Inoculate the specimen in anaerobic medium within minutes and place it in an anaerobic chamber for cultivation37Cultivation in ℃ box2～7Tian, observe the growth of bacterial colonies on the culture medium every day. Directly inoculate blood and other liquids onto the culture medium of the blood detector, which can quickly detect anaerobic bacteria in the blood. Select suspicious bacterial colonies for identification and drug sensitivity testing, use a micro biochemical system to identify the tested bacteria or store them in refrigeration for a long time.

Anaerobic bacteria as important opportunistic pathogens,The infection caused by it has received increasing attention. Many hospital microbiology labs (such as Shenzhen Second People's Hospital, Shenzhen Hong Kong University Hospital, Shenzhen Futian Hospital, Shenzhen Orthopedic Hospital, Shenzhen Sun Yat sen Hospital, Guangdong Provincial People's Hospital, Sun Yat sen University Affiliated Stomatological Hospital, Sun Yat sen University Affiliated Hospital, Sun Yat sen University Affiliated Sixth Hospital, Southern Hospital, Guangzhou Medical College Affiliated Hospital, Guangzhou Second People's Hospital, Guangzhou Eighth People's Hospital, etc.) cooperate with institutions such as Shenzhen Huada Gene Research Institute to carry out anaerobic bacterial identification and drug sensitivity testing, quickly assisting clinical diagnosis of anaerobic bacterial infections and selecting effective medication plans.