OVERVIEW
Fusobacteria are a group of gram-negative bacilli that do not ferment sugars, are conditionally pathogenic, and are part of the normal flora of the human body. The bacterium is highly adherent and adheres readily to various types of medical materials, which may serve as reservoirs for the bacterium. In addition, the bacterium is present in the skin (25%) and pharynx (7%) of healthy individuals, as well as in conjunctiva, saliva, gastrointestinal tract and vaginal secretions. The source of infection can be the patient himself (endogenous infection) or a person infected with Fusobacterium immobilis or a carrier, especially a healthcare worker with infected hands. The routes of transmission are contact and airborne. In hospitals, contaminated medical equipment and staff hands are important vectors. Susceptible persons are elderly patients, premature infants and newborns, surgical trauma, severe burns, tracheotomy or intubation, the use of artificial respirators, intravenous catheters and peritoneal dialysis, broad-spectrum antimicrobial drugs or immunosuppressant applications. Depending on the site of infection and the severity of the disease, it can cause respiratory tract infection, wound infection, sepsis and so on. The incidence of pneumonia is about 3% to 5% among those who use ventilators.
Etiology
The classification of this genus has gone through many changes, such as Calcium acetate micrococcus, Mucococcus, Helicobacter vaginalis, Nitrate-negative bacillus, Nitrate colorless bacillus, Polymorphic mimic, and Lofimora. The bacterium belongs to the family Neisseriaceae, there is only one species, that is, Calcium acetate immobilized bacterium, divided into two subspecies: Calcium acetate immobilized bacterium nitrate-negative subspecies and Lofimeria subspecies; the latter is old known as polymorphic mimic bacterium. The main difference between the two subspecies is that the former can oxidatively decompose glucose, xylose lactose, etc., acid production without gas production, while the latter does not decompose any sugar. In recent years, by deoxyribonucleic acid (DNA) hybridization techniques, Firmicutes have been classified into 19 species. Seven of them have been named, i.e., Acetate Calcium Fusobacterium, Fusobacterium lysogenum, Fusobacterium Acetobacterium, Fusobacterium Acetobacterium, Fusobacterium Acetobacterium, Fusobacterium Agrobacterium and Fusobacterium Johnssonii, and Fusobacterium Radiographis Resistant, with nitrate negative Fusobacterium Acetobacterium and Fusobacterium Lophophorum being more pathogenic.
The pathogenicity of this bacterium is not strong, in which the pathogenicity of Acinetobacter baumannii, Acinetobacter calcoaceticus and Acinetobacter lofii are stronger, and the virulence factor of its pathogenicity is less, which may be mainly related to bacteriocins, pods, hairs and so on, and this bacterium doesn’t cause disease in general, and it can only cause infections when the resistance of the body decreases. At present, among the clinically infected immobilized bacilli, Acinetobacter baumannii and Acinetobacter calcoaceticus account for the majority (80%), the predisposing factors for this disease are patients often have serious primary diseases such as chronic lung diseases, malignant tumors, burns, immunocompromised and elderly hospitalized patients, usually occurring after 1 week of hospitalization; patients in the application of hormones, immunosuppressants and broad-spectrum antibiotics, etc., which can change the immune function and the normal flora in the body and lead to the bacterial infection of the bacteria. The application of hormones, immunosuppressive drugs and broad antibiotics can change the immune function and the normal flora in the body and lead to bacterial dysbiosis; the application of various catheters, endotracheal intubation, artificial devices and major surgery, etc., which are often the pathway of infection; and the place of infection is often the intensive care unit (ICU), the burns ward and so on. The opportunistic infections caused by this genus include skin wound infection, genitourinary tract infection, pneumonia, lung abscess, sepsis, endocarditis, meningitis, brain abscess, etc. It accounts for 1% to 3% of hospital-acquired infections, and can occasionally cause out-of-hospital acquired infections.
Symptoms
Clinical manifestations vary greatly depending on the site of infection and the severity of the disease.
1. Respiratory tract infection
Respiratory tract infections are more common, mostly occurring in patients with serious underlying diseases, such as pre-existing pulmonary diseases, long-term bedridden, receiving a large number of broad-spectrum antibacterial drugs, tracheotomy, tracheal intubation, artificial assisted respiration and so on. Among the respiratory specimen isolates from ICU patients in China, Acinetobacter baumannii ranked the third (11%), with manifestations such as fever, mostly mild or moderate irregular fever, cough, chest pain and shortness of breath, and cyanosis in severe cases. The lungs may have medium to fine wet rales. Chest X-ray often shows bronchopneumonia, or lobar or sheet-like infiltration shadow, occasionally abscess or exudative pleurisy. Septicemia and meningitis may occur. Sputum culture and tracheal aspirate culture have a large number of bacterial growth.
2. Septicemia
Fusobacterium septicemia occurs mainly in hospital-acquired infections. Among the 2576 strains of pathogenic bacteria in sepsis, Fusobacterium indolentis in intra-hospital infections is second only to Escherichia coli and Pseudomonas spp. in Gram-negative bacilli, and the isolation rate with L. pneumophila is almost equal to that of L. pneumophila, accounting for about 8%. In contrast, Fusobacterium immobilis has the lowest incidence of sepsis among the nine Gram-negative bacilli in out-of-hospital infections. Immobilized bacillus sepsis occurs most often in patients with indwelling arterial or venous catheters, urinary catheters, or surgical procedures, or those with severe underlying disease, prolonged adrenocorticotropic hormone or cytotoxic medications, and is often comorbid with respiratory tract infections. Patients have symptoms of febrile toxemia, skin petechiae, hepatosplenomegaly, etc. Shock may occur in severe cases. This disease has a high morbidity and mortality rate, and one of the important reasons is that it is related to the drug resistance of the bacteria and multiple bacterial co-infections.
3. Wound skin infection
Wound infection accounts for 17.5% of the total number of infections with this bacterium, and the incidence rate is in the order of traumatic infections, post-surgical infections, and post-burn wound infections. Wound infection can also be caused by the bacteria and other bacteria (such as Enterobacteriaceae, Pseudomonas aeruginosa, Enterococcus, Staphylococcus or Streptococcus pyogenes) constitute a mixed infection. Intravenous catheters contaminated with the organism can cause severe cutaneous cellulitis. Severe wound infections are often associated with sepsis.
4. Genitourinary tract infection
The detection rate of this bacterium in the genitourinary system is high, second only to the respiratory system. Domestic scholars have reported that the urinary tract infection caused by this bacterium accounted for 28.6%. The primary causes are prostatic hypertrophy, urethral stones, urethral stenosis, and the causative factors are mostly indwelling catheter and cystostomy. Clinical manifestations of urethritis, pyelonephritis, vaginitis, etc., most of the bacterial genus alone is mainly infected, some may be mixed with other bacterial infections, there are still some asymptomatic carriers.
5. Meningitis
Meningitis occurs mostly after craniocerebral surgery, and can also be primary infection, especially in children. The triggering factors are craniocerebral surgery, craniopharyngioma aspiration, lumbar puncture and so on. Clinical manifestations include pyogenic meningitis changes such as fever, headache, vomiting, cervical rigidity, and positive Kernig’s sign. In infants and young children, there is gaze, screaming, convulsions, nystagmus, full and tense fontanel, widening of the bony seams and increased muscle tone in the extremities. Petechiae may also appear on the skin.
6. Other
The organism may cause infections in other parts of the body and form suppurative inflammation, such as septic arthritis, osteomyelitis, peritonitis, abdominal abscess, eye infections and oral abscesses.
Examination
1. Bacterial culture test
It is mainly detected by bacterial culture. The main culture methods are urine culture, sputum culture, and pharyngeal mucus culture. When the urine culture is positive, the bacterial count should be more than 100,000/mL, and the sputum culture is positive, and the number of Fusobacterium colonies in each dry plate should be more than 30, which is also the basis of judgment.
2. Blood test
The total number of white blood cells is obviously increased, and the neutrophils are more than 80%.
3. X-ray examination
X-ray examination of the lungs may show multilobar tracheobronchial pneumonia, occasional abscess formation and exudative pleurisy. Cerebrospinal fluid is turbid, with increased total cell count and neutrophils.
Diagnosis
Diagnosis of Mycobacterium avium infection depends on bacterial culture.
Complications
Ventriculitis, brain abscess, hydrocephalus, septic arthritis, osteomyelitis, peritonitis, abdominal abscess, eye infections, and oral abscesses may be complicated.
Treatment
Drug resistance in Mycobacterium avium is a serious problem. The rate of resistance is on the rise, e.g., increasing resistance to ciprofloxacin. Fusobacterium indolentum has been found to be highly resistant to ampicillin, cefazolin and chloramphenicol.
The resistance rate is still low, including imipenem-cestadine, ceftazidime, cefoperazone-sulbactam, ampicillin-sulbactam, piperacillin-tazobactam and amikacin. Therefore, cefoperazone-sulbactam and imipenem-cestadine are preferred for clinical application, and ampicillin-sulbactam, ticarcillin-clavulanic acid, amikacin, and a new generation of fluoroquinolones can also be chosen. β-lactams and aminoglycosides (or fluoroquinolones and rifampicin) are commonly used in the combination of more severe conditions.