Urinary tract infection caused by Edwardsiella tarda: a report of the ... - BMC Infectious Diseases

Edwardsiella tarda is an uncommon pathogen from the Enterobacteriaceae family that can rarely infect humans. The human infection rate is 0.0073% in Japan and 1% in Panama. According to a cohort study conducted in Japan between January 2005 and December 2016, the incidence rate of E. tarda is 0.02%, and the mortality rate within 90 days is 26.9% [3, 7, 11].

Clinical complications of E. tarda infection are enteritis, liver abscess, cholecystitis, spontaneous bacterial peritonitis, mycotic aneurysm, necrotizing fasciitis, empyema, osteomyelitis, psoas abscess, spinal epidural abscess secondary peritonitis and UTI [12, 13].

Our patient is the first case of human E. tarda infection in Iran and the second in the Middle East. According to the reports, E. tarda infection cases are mostly reported in East Asia, Australia, North and South America [3].

Edwardsiella tarda infection frequently occurs when water temperatures are high, particularly from summer to autumn [14]. It is more common in the elderly, with an average age of 61 years [3]. In contrast, our patient was a 4-year-old child with E. tarda infection in spring.

Intestinal symptoms such as gastroenteritis are the most frequent manifestations of E. tarda infection [15]. Although E. tarda is a rare human pathogen, immunocompromised patients and those with subacute or chronic diseases have a higher incidence of extraintestinal infection [16]. Tamada et al. reported the first case of urosepsis by E. tarda in 2009 [12]. The patient was a woman undergoing chemotherapy for advanced uterine cancer. In a study of E. tarda infection in Thailand, the organism was isolated from 13 patients with urinary tract infection, none of which were associated with bacteremia, and the majority of patients had chronically indwelling urethral catheters [17]. Our patient, in contrast, had no history of chronic illness or medication or urethral catheter use.

Although E. tarda produces β-lactamase, it rarely displays resistance to β-lactam antibiotics [18]. Antibiotics with activity against Gram-negative bacilli, such as the majority of β-lactams, aminoglycosides, tetracyclines, fluoroquinolones, and antifolates, are effective against nearly all E. tarda strains [12]. However, in our case, the isolated E. tarda strain was resistant to cefixime, cotrimoxazole, and fluoroquinolones. Penicillins, cephalosporins, and carbapenems are frequently used in the treatment of E. tarda [3]. Our patient was also initially treated with ceftriaxone, which resulted in the improvement of the patient's symptoms.

Historically, E. tarda has been identified in a wide variety of reptiles, amphibians, and fish, including catfish and eels, in both fresh and brackish water settings, and it can also cause disease in these animals [13]. According to the research carried out by Preena et al., E. tarda is one of the pathogens that can infect goldfish species and cause 100% mortality in these fish [19]. In addition, this pathogen poses a serious threat to aquaculture globally. Contact with goldfish is likely to cause illness in humans [3]. Likewise, our patient was frequently exposed to goldfish prior to the onset of symptoms. Additionally, the goldfish died after a short time, which could be indicative of infection by E. tarda.

Goldfish is one of the 7 Haft Seen items in Iran. Haft Seen is an arrangement of seven symbolic objects that is customarily displayed during the Nowruz holidays beginning on March 21. Goldfish are indigenous to China. According to government accounts, it has been brought from China to Iran in past years due to cultural requirements. In recent years, however, it has been widely cultivated in Iran. Also, each year following the Nowruz holiday, people release millions of these fish into the rivers and lakes of Iran [20]. This is also a significant concern in the United States and Canada. In 2015, for instance, the Canadian government urged people to stop releasing fish into lakes. Considering that goldfish carry several parasites and can reproduce rapidly in harsh environments, they pose a threat to the ecosystem. It is recommended to prevent the release of this type of goldfish in nature. Regular veterinary care is also required for goldfish [21].

This case demonstrates that E. tarda can be a urinary pathogen and can induce extraintestinal infection even in individuals with a healthy immune system. Our patient is the first known case of Edwardsilla infection in Iran, and since aquatic animals spread this pathogen, there is a likelihood that other humans and aquatic animals will become infected in Iran. As a result, the appropriate safety measures should be adopted, including preventing contact with aquatic organisms and consuming raw or undercooked fish and seafood, as well as isolating fish that may be suspicious or infected from others.