Enterobacterium inguinale is a member of the genus Enterobacteriaceae in the family Enterobacteriaceae. The bacterium is a gram-negative thick and short bacillus, about 0.6 to 1.1 μm wide, about 1.2 to 3.0 μm long, with a periplasmic flagellum (6 to 8 flagellum), power-positive, no bacilli, no pods. Its optimal growth temperature of 30 ℃, parthenogenetic anaerobic, in the ordinary medium can grow, the formation of large and wet mucus-like colonies, in the blood agar is not hemolytic, in the red - methylene blue agar (EMB) for pink and viscous. On MacConkey agar, they were pink or red and slimy. On SS agar it is white or milky white, opaque and viscous if grown. In sugar fermentation: lactose, sucrose, sorbitol, raffinose, rhamnose, honey disaccharide are positive, can not produce yellow pigment. Ornithine decarboxylase test (+), arginine dihydrolase test (+), lysine decarboxylase test (-), indole (-). Enterobacter cloacae have three antigenic components O, H and K. Cultures of most strains can strongly agglutinate with homologous O sera after boiling at 100°C for 1h. And live bacteria with its agglutination weak or non-agglutination, indicating a K antigen, in the O serum does not agglutinate in the live bacteria cultures in by 100 ℃ heating 1h, bacterial suspension by 50% ethanol or 1 mol hydrochloric acid treatment, 37 ℃ for 18h become agglutinable, but in 60 ℃ heating 1h still does not lose its O non-agglutinative properties, with boiling and heating of bacterial suspensions prepared by the antisera do not contain K agglutinin. The antigenic table of Enterobacter cloacae established by Sakazaki consists of 53 O antigen groups, 56 H antigens and 79 serotypes. ① O antigen: slide agglutination test is a routine method for the determination of Enterobacteriaceae inguinalis, overnight agar cultures of concentrated saline bacteriophage, heated to 100 ℃ for 1h, washed by centrifugation, and diluted O serum used for agglutination, although the potency of the serum is 500-1000, but it is still used for slide agglutination with a dilution of 1:10, it is preferable to use a higher dilution of the antisera, which can produce a strong reaction in a few seconds, and the cross reaction is somewhat less. Delayed and unilateral reactions are observed between different O antigens. Although most groups of O antigens can be measured with moderately diluted unabsorbed sera, it is often necessary to use absorbed group-specific sera for the determination of specific O antigens. (ii) H antigen: for the determination of H antigen, the routine method is the test tube agglutination test, using kinetically active overnight broth cultures, the medium is based on trypticase soy broth containing 0.2% dextrose and immersion broth, and after incubation, an equal amount of 0.6% formaldehyde saline is added to the broth cultures, and unabsorbed sera of this bacterium with potency of 10,000-20,000 are usually diluted 1:1,000, and a 1:100 dilution of the H serum 0.1ml placed in a small test tube, and then add formaldehyde solution 1.0ml treated broth cultures, the test tube at 50 ℃ water bath 1 ~ 2h after reading the results. Intra- and extra-genus antigenic relationship of Enterobacteriaceae: Although there are several species within the genus Enterobacteriaceae, Enterobacteriaceae is the only one for which antigenic studies have been carried out, and therefore the antigenic relationship between Enterobacteriaceae and other species of the genus Enterobacteriaceae is not clear at present. It has been previously reported that most Enterobacter cloacae can be serotyped with Klebsiella pods, and Sakazaki's study demonstrated that the mucus produced by Enterobacter cloacae is not a true pod, and that there is no obvious O-antigen and K-antigen relationship between Klebsiella and Enterobacter cloacae.
(II) Pathogenesis
As a gram-negative bacterium, endotoxin plays a pathogenic role. In addition to this, the bacterium is strongly resistant to disinfectants and antibiotics, which is an important factor in the increasing number of hospital-acquired infections. The reason for this is that it can quickly acquire resistance to antibiotics, especially to beta-lactam antibiotics, which should be taken seriously by clinicians.
1. Host defense function is reduced
(1) local defense barrier is damaged: burns, trauma, surgery, certain interventional operations caused by skin, mucous membrane damage, so that enterobacteria enterica inguinalis is easy to invade through the human barrier.
(2)Defective function of the immune system: congenital developmental disorders of the immune system, or acquired damage (physical, chemical, biological factors), such as radiation therapy, cytotoxic drugs, immunosuppressants, viral infections that damage the immune system can cause opportunistic infections.
2. Provide an opportunity for pathogen invasion of various surgeries, indwelling catheters, intravenous puncture catheters, endoscopy, mechanical ventilation, etc. application makes the inguinal enterobacteria have a pathway to invade the organism, which may lead to infection.
3. Enterobacter inguinalis produces β-lactamasesEnterobacter inguinalis produces both ESBIs and AmpC enzymes, resulting in a high degree of resistance to a variety of antibiotics, making clinical treatment difficult. The drug sensitivity test of 144 strains of E. inguinalis in Zhejiang Province showed that the sensitivity rate to amoxicillin-clavulanic acid, cefuroxime, amitrazine, cefotaxime, ciprofloxacin, piperacillin-tazobactam, and amikacin was below 55%, and that the sensitivity rate of cefoperazone-sulbactam, and cefepime was only about 60%, and that only the sensitivity rate of imipenem was as high as 98.61%, of which the high production of AmpC enzyme accounted for 24.31%. strains accounted for 24.31% and ESBLs-producing strains accounted for 36.81%.
4. Widespread use of antibiotics
(1) Broad-spectrum antibacterial drugs can inhibit the normal flora of all human ministries, resulting in dysbiosis.
(2) Antibiotic-sensitive strains of bacteria are inhibited, so that drug-resistant strains of bacteria multiply, which can easily cause the spread of hospital infections and cause patient morbidity. In recent years, due to the widespread use of third-generation cephalosporins, it is easy to screen the high AmpC enzyme-producing Enterobacteriaceae inguinalis, leading to the prevalence of drug-resistant bacteria.