Overview.
Multiple lung infections refer to lung infections with two or more (including two) pathogenic microorganisms. Multiple infections with different types of pathogens (e.g., bacterial and fungal, bacterial and viral, fungal or protozoal and viral) have tended to increase in recent years in critical care hospital-acquired pneumonia and pneumonia in immunosuppressed patients. Multiple infections are strictly defined as infections in which multiple pathogens are all present as primary and occur simultaneously, excluding primary infection with one pathogen and secondary infection with another. Secondary infection is a complication caused by the application of broad-spectrum antibiotics, especially the irrational application, which is not a multiple infection, but in most clinical cases the primary infecting organisms have not been killed or it is difficult to conclude that the primary infecting organisms have been killed. Therefore, secondary infections and secondary infections complicated by antimicrobial therapy are not multiple infections in the strict sense in terms of pathogenesis or pathogenesis, but they can be regarded as multiple infections in a broader sense in terms of the simultaneous presence of two or more pathogens and therapeutic goals.
Etiology.
The pathogenic spectrum of multiple lung infections can be any different type of pathogen or concurrent infection with different species (genera) of pathogens within the same type, the more common combinations of pathogens are:
1. plural bacterial infections
Combined infection of two or more aerobic bacteria (including gram-positive and gram-negative, two gram-negative bacilli, or two gram-positive cocci), aerobic and anaerobic bacteria, and mycobacteria and common bacteria.
2. Bacterial plus fungal infection
Any bacterial and fungal co-infection, with aerobic bacteria and conditionally pathogenic bacteria such as Candida and Aspergillus being the most common.
3. Bacterial plus protozoal infection
Pneumocystis carinii combined with bacterial infection is common.
4. Bacterial and viral infections
Respiratory viral infections are common secondary to bacterial infections. Bacterial and cytomegalovirus co-infections are common in immunosuppressed patients.
Symptoms
Anaerobic bacteria combined with other pathogens may have clinical features of anaerobic infection such as purulent sputum. Other types of multiple infections lack characteristic symptoms. In general, patients with multiple infections have more severe symptoms.
Tests
1. Laboratory tests
Coughing sputum after screening, take qualified specimens for culture, if two or more bacteria are dominant growth reach 106CFU/ml, it has important reference value.
2.Other auxiliary examination
X-ray lesions are more extensive, necrotizing pneumonia is more common.
Diagnosis
Multiple lung infections, although clinically quite common, but the diagnosis is very difficult, first, because some pathogens such as viruses and other laboratory diagnostic techniques can not adapt to the clinical needs; second, because of the lower respiratory tract specimen collection difficulties, the upper respiratory tract and the oral cavity there is a large number of colonizing bacteria, and in the process of prolonged hospitalization or antimicrobial treatment of the bacterial flora of the frequent changes in the process of coughing up sputum specimens through the mouth easily be contaminated, the culture of a variety of bacterial growth does not mean that there is really The presence of multiple bacterial growth in culture does not indicate the presence of multiple infections; on the contrary, the absence of bacterial growth in culture or the growth of a single bacterium does not exclude multiple infections.
Clinically, patients with conditions and risk factors that predispose them to multiple infections, or those with moderate-to-severe lung infections that have not responded to standardized antibiotic therapy, should be alerted to the possibility of multiple infections. Lung abscesses and bronchiectasis are commonly characterized by a mixture of anaerobic and aerobic infections and may be treated as multiple infections if the clinical picture is typical. In other types of pneumonia, the diagnosis of multiple infections, including secondary infections, requires definitive pathologic evidence. Blood and pleural fluid specimens with culture results are the most diagnostic, and lower respiratory tract anti-contamination or bronchoalveolar lavage specimens need to be combined with quantitative culture. Cough sputum is screened, and qualified specimens are taken for culture. If two or more bacteria are predominantly growing at 106 CFU/ml, it has an important reference value. Conditional pathogenic fungi also need to be sampled from the lower respiratory tract by applying anti-pollution techniques, and the results of oral sputum specimen culture are meaningless. Virus detection due to culture difficulties, serum immunology and molecular biology techniques have reference value. Pathohistologic examination of Pseudomonas aeruginosa pneumonia and certain specific pathogen infections (fungi, Pneumocystis carinii, Mycobacterium) combined with special stains have important diagnostic value.
Treatment
Antimicrobial therapy of multiple infections is based on pathogenetic diagnosis, the method of which is a combination of drugs. During treatment unsatisfactory results should be early drug sensitivity tests, and then select sensitive drugs for treatment.