E. fergusonii is a rare opportunistic pathogen in humans and animals. In 1985, Farmer [13] et al. separated and confirmed that E. fergusonii was a newly discovered species of Enterobacteriaceae in the blood samples of clinical patients. Before that, it was known as group 10 of intestinal bacteria in general. In 1991, Lawrence [8] et al. found that the bacterium had the closest genetic relationship with E. coli, which also belonged to E. coli, and DNA hybridization showed that they had 64% similarity. Compared with E. coli, there are few reports about patients infected with E. fergusonii. Due to the rarity of E. fergusonii, many conventional laboratories cannot distinguish E. coli and E. fergusonii [9].
In 1993, Funke [10] et al. separated E. fergusonii from bile, blood, feces, and abdominal wound secretion of a 69-year-old male patient with pancreatic cancer and bile duct abscess. However, it was confirmed to be the same bacterial clone after experimental analysis. It has been reported that this bacterium was detected in feces before[4,11], and it is well known that the intestinal tract is connected with the biliary duct and pancreatic duct, so it is not clear whether the E. fergusonii migrates from the intestinal tract to the bile duct to cause infection or the bile specimens collected are contaminated with the intestinal contents. In 2011, Lai [12] et al. from Taiwan in China detected this bacterium in the blood of a 73-year-old male patient with pancreatic cancer, but not in feces and bile. The patient, in this case, was a 74-year-old male patient with pancreatic head cancer and Biliary stones, and bile samples were aspirated by an endoscopically aseptic catheter during ERCP surgery, which could basically rule out the possibility of intestinal contamination. Unfortunately, fecal bacteria were not collected for culture and cannot be traced further. Whether this bacterium has a certain organ-targeting for the cancerous tissues of pancreatic cancer remains to be further studied, but when biliary tract infection occurs in elderly patients with pancreatic cancer, this bacterium should be excluded.
Farmer [7] et al. isolated 2 strains of E. fergusonii from human blood for the first time, and collected a total of 25 strains from the American Strain Preservation and Management Center, including 2 strains from blood, 5 strains from urine, 1 strain from abdominal infection, 16 strains from feces and 1 strain from others, but lacked more detailed clinical data. This group reviewed 8 patients, with all eight cases being E. fergusonii: male: female = 5:3, average age 61.4 years old, ≥ 60 years old accounted for 62.5%, with 75% having basic diseases, including malignant tumor disease (2 cases, 25%), diabetes mellitus (2 cases), surgery or trauma (2 cases), biliary tract disease (1 case, 12.5%), stroke (1 case). The infection sites were urinary tract infection, blood flow infection, and intestinal infection in 3 cases, and bone tissue, secretion, and abdominal wound infection in 1 case. The source of the specimen was almost identical to the site of infection.
All of these 8 patients were treated with antibiotics through empirical or drug susceptibility results. Cephalosporins and quinolones were most commonly used, and most of them were improved or cured (4 cases, 50%). 3 cases died due to serious underlying diseases combined with infection, and 1 case was unknown. Drug susceptibility showed that E. fergusonii was most sensitive to Piperacillin/tazobactam and Imipenem, but less sensitive to Levofloxacin and Ciprofloxacin. In 2005, India Mahapatra A [13] et al. isolated 104 strains of E. fergusonii from 600 clinical specimens, 83% of which were susceptible to amikacin, followed by Cefoperazone/sulbactam (79%) and Gatifloxacin (73%), Cefotaxime and Ciprofloxacin 53% and 33%, respectively. Gentamicin showed the poorest sensitivity. However, the susceptibility to Imipenem was not mentioned in the report. With the emergence of multi-antibiotic resistant E. fergusonii, it is vital that we evaluate the antibiotic sensitivity of more cases in future research.
The biofilm is a structured community of bacteria that adheres to a contact surface. It secretes polysaccharide matrix and other extracellular polymers, and encapsulates itself in a large number of bacterial aggregates. Studies have shown that bacteria in biofilms are 10-1000 times more resistant to antibiotics than bacteria in their planktonic state, which can easily lead to the development of bacterial drug resistance and cause serious clinical problems, resulting in recurrent attacks of many chronic and refractory infections. The increasing number of drug-resistant strains of E. coli, which also belong to the Enterobacteriaceae, is mostly due to the formation of its biofilm. E. coli with biofilm helps it to resist conditions such as oxidative stress, antibiotic treatment, dehydration and starvation .[17,18] Scientists believe that biofilm resistance may be related to nutritional restriction, impaired antibiotic penetration, inhomogeneity of the biofilm, abnormal expression of efflux pump genes, horizontal transfer of genes, and secretion of inactivating enzymes.
However, due to the rarity of E. fergusonii with biofilm, its resistance mechanism and other related mechanisms need to be further studied.