OVERVIEW
Enterobacter pneumonia used to be extremely rare. Recent decades. With the increased use of broad-spectrum antibiotics and respiratory medical devices, Enterobacter pneumonia has accounted for 9.4% of nosocomial-acquired pneumonia, ranking 4th after Pseudomonas aeruginosa pneumonia, Pseudomonas aureus pneumonia, and Klebsiella pneumonia, with Enterobacter inguinalis and Enterobacter aerogenes being the most common causes. Clinically, Enterobacteriaceae pneumonia occurs in debilitated or immunosuppressed individuals, and is prone to outbreaks caused by contaminated medical devices, often accompanied by bacteremia and poor response to multiple antibiotic treatments, among other characteristics.
Etiology
Enterobacteriaceae are divided into Enterobacter inguinalis, Enterobacter aerogenes, Enterobacter aerogenes, Enterobacter agglomerans, Enterobacter jejuni, Enterobacter sakazaki and Enterobacter taylori. Among them, Enterobacter inguinalis and Enterobacter aerogenes are clinically important conditional pathogens, which can cause pneumonia, sepsis, urinary tract infection and meningitis, etc. Enterobacter aerogenes is an important pathogen of hospital-acquired infections, which can contaminate the infusion solution to cause sepsis and other infections. Enterobacteriaceae bacteria are widely distributed in the natural environment. They can be found in soil, sewage, decaying vegetables and dairy products. Enterobacter cloacae and Enterobacter aerogenes can colonize the gastrointestinal and respiratory tracts and are part of the normal flora.
Symptoms.
Enterobacter pneumonia is similar to other gram-negative bacilli pneumonia. The onset of illness is rapid, with sudden onset of chills and fever. Body temperature is often between 37.7℃ and 38.8℃. Cough is obvious, coughing sputum is more voluminous and mucopurulent, but unlike Klebsiella pneumonia, hemoptysis and bloody sputum are rare. If the lesion is extensive, there may be dyspnea. Physical examination may show shortness of breath and cyanosis. Wet rales are often heard in both lungs, and signs of solid changes in the lungs are rare. If the infection is of hematogenous origin, pulmonary signs are sometimes absent, but extrapulmonary infections such as urinary tract and gastrointestinal tract are often found.
Examination
1. Blood picture
The total number of white blood cells may be increased or normal, but neutrophils are often increased, anemia is more common.
2. Urine routine, renal function and liver function
Urine routine, renal function and liver function may be abnormal in Enterobacteriaceae sepsis combined with pneumonia.
3. Sputum bacterial culture
It is the only means to confirm the diagnosis of Enterobacteriaceae pneumonia. Clinically coughed sputum is contaminated by other bacteria in the oropharynx, and specimens can be obtained by transthoracic membrane puncture, percutaneous lung puncture and transfibrillation. If cough sputum culture is used, the specimen needs to be processed before culture and the application of appropriate selective culture medium to improve the reliability of the results.
(1) Treatment of sputum The sputum should be washed with saline for 5-9 times (which can reduce the contaminating bacteria up to 100 times on average), and then the sputum should be taken and incubated with 1%-2% protease or acetylcysteine at 37℃ if the concentration of the bacteria is >106/milliliter and the squamous epithelial cells are <10 in a low-power field of view. When the bacterial concentration is >106/mL, the culture is considered diagnostic, and a series of biochemical reactions and typing are further performed to determine the strain and type of bacteria.
(2) Selection medium Because the concentration of Enterobacteriaceae is sometimes low in sputum specimens, it is necessary to use selection medium to increase the positive rate of culture. Composition of selection medium: 2% cellulose disaccharide 0.1% yeast extract, 0.03% sodium deoxycholate 10μg/ml cephalosporin, 1% agar and Andrade’s indicator. Most of the Enterobacter cloacae were incubated at 37°C for 24 hrs to produce pigmentation due to pH change and most of the fecal coliforms grew slowly or not at all. Enterobacter aerogenes also grows on this medium.
4. X-ray examination
X-ray chest radiographs often show bronchopneumonia of both lower lungs, but in a few cases, only increased lung texture is seen without significant parenchymal infiltration. In a few patients with inhalation infection, the posterior segment of the upper lobe and the dorsal segment of the lower lobe of the right lung can be seen in a large range of solid shadows, between which can be seen in the cavity, but far less common than Klebsiella pneumonia in cases of hematogenous infections, the chest radiographs see irregular nodular hyperdensity, diameter of 4 to 10mm, spread throughout the lungs. If the disease progresses, the nodules increase in size and merge.
Diagnosis
The clinical presentation of Enterobacteriaceae pneumonia is not characteristic and is similar to that of other gram-negative bacilli, making it difficult to confirm the diagnosis on the basis of clinical presentation alone. The presence of fever, increased bronchial purulent secretions, increased leukocyte counts, and the presence of lung foci or new infiltrates on top of the original lung lesions during hospitalization in high-risk individuals are diagnostic. Confirmation and differential diagnosis depend on bacteriologic examination.
Differential diagnosis
It should be differentiated from gram-negative bacillus pneumonia such as Pseudomonas aeruginosa pneumonia Klebsiella pneumonia, Haemophilus influenzae pneumonia, and Aspergillus pneumonia.
Complications
One of the common complications of Enterobacteriaceae pneumonia is bacteremia. Literature reports that among the various causes of Enterobacteriaceae bacteremia, respiratory tract infection followed by development of bacteremia accounted for 11%, second only to those with abdominal organ and urinary tract infections. Therefore, blood cultures should be performed when pulmonary infections are suspected to be due to hematogenous dissemination or when accompanied by bacteremia. If Enterobacteriaceae are positive, the diagnosis is confirmed.
Treatment
1. General treatment
Including rest, nursing care, diet, oxygen, cough and expectorant and other general treatment.
2. Antibacterial treatment
Choose antibiotics that target pathogenic bacteria and combine with drug sensitivity test.
3.Complications treatment
For the complication of pus thorax and other timely puncture or drainage, if it affects the function of other organs, it should be dealt with accordingly.
4. Treatment of primary disease
The nature of the primary disease is often an important factor in determining the prognosis of Enterobacteriaceae bacterial infections. Therefore, in the antimicrobial therapy at the same time, actively treat the primary disease.
Prognosis
The prognosis is poorer in the elderly and frail with severe underlying diseases and immunocompromised.
Prevention
1. Reduce the prophylactic application of antibiotics According to research, the prophylactic application of antibiotics, especially cephalosporin antibiotics, can increase the carriage rate of Enterobacteriaceae in hospitalized patients. Therefore, reducing the prophylactic application of antibiotics can prevent the occurrence of Enterobacteriaceae pneumonia.
2.Local application of non-absorbable oral antibiotics to reduce the parasitization of Enterobacteriaceae spp. bacteria in the oropharynx and gastrointestinal tract can reduce the incidence of Enterobacteriaceae spp. infections in patients in the ICU.
3. Prevent localized E. enterica parasites from developing into infections Some studies have shown that the application of active or passive immunopharmaceuticals can prevent parasitized E. enterica from developing into infections, but most of them are in the experimental stage at present.
4. prevent the spread of infection between patients medical personnel in respiratory care and treatment, pay attention to hand washing, strict aseptic operation.
5. When outbreaks of infection are suspected or occur, immediately perform typing to determine appropriate control measures.