The Shell’s Trouble: A Case of child bloodstream infection caused by Aeromonas salmonicida subsp. salmonicida

Background


Background
A. salmonicida is a non-motile aeromonad Gram-negative bacteria which belongs to the genus Aeromonadaceae. The optimum growth temperature for A. salmonicida is 22-25℃, and it rarely grows at 37℃ [1]. A. salmonicida is widely known as a water resident bacteria which generally caused sh disease and affect the salmonid aquaculture industry [2][3]. As we know, A. salmonicida can be divided into ve subspecies in more detail: salmonicida, masoucida, smithia, pectinolytica and achromogenes [1]. So far we have only a few articles that reported about A. salmonicida infected humans. In this paper, we present a case of Aeromonas salmonicida subsp. salmonicida. caused a 22 months old child's bloodstream infection.

Case Presentation
A 22-month-old boy was admitted to our hospital with one-day history fever and mid diarrhea. At admission, his armpit temperature was 39.7℃, respire was 30 times pear minute, pulse rate was 130 beats pear minute. Then, he took general laboratory tests, and blood culture was collected immediately.
The test results showed as follow: white blood cell (hereafter referred to as WBC): 11.5*10 9 /L (reference After three days treatment, the child's condition improved and his body temperature returned to normal (36°C), a complete blood count and (CRP) test did again, and the result was follows: WBC: 7.4*10 9 /L, neutrophils: 2.8*10 9 /L, CRP: 23.18 mg/L. The blood culture indicate positive after 11.6 hours of incubation in BD 9120 ( Becton-Dickinson, New Jersey, United States ) automated blood culture system, the positive bottle was transferred to blood agar plate and Macconkey agar plate for separation and culture, subsequently, identi cation and drug susceptibility tests were carried out for the isolated bacteria (VITEK 2 COMPACT). The culture results showed Aeromonas salmonicida subsp. Salmonicida growth, and the drug susceptibility test results were presented in table. 1.
Day 4, the treatment medication was adjusted from cefathiamidine to ceftriaxone according to the results of drug sensitivity. Day 6, the child had no more fever and his general condition was good. Here was the last laboratory tests result: WBC: 7.8*10 9 /L; neutrophils: 2.3*10 9 /L; CRP: 9.33 mg/L; PCT: 0.410 ng/mL.
Then the child was discharged from hospital at the request of his parents and did not back to hospital for any physical discomfort after that. We called for a follow-up visit three days later, and his condition was very good.

Discussion And Conclusions
As a psychrophilic bacteria that exists widely in water, A. salmonicida is an important sh pathogen and is responsible for furunculosis. This bacterium is believed to not normally grow at the human body temperature.
A. salmonicida can rarely cause human illness from our literature search. According to the literature we searched, human diseases caused by A. salmonicida including bacteremia, septicemia, endocarditis, endophthalmitis, etc. [4][5][6][7][8][9]. The patients' age from 7 to 60, and the symptoms of patients include lower fever, weakness, pain, cough. There of them can be traced back to epidemiological history. The patient under two-years of age in our case is the youngest known infected person who do not have welldeveloped immune system, and maybe this is one of the reasons that caused his infection.
In this case, we further inquired of the child's parents about epidemiological history and possible causes of infection for the bacterial identi cation result. We learned that their family had gone to the beach two days before the onset of illness, the child scratched his hand by the shell, this situation did not get the parents' attention, the wound was just simply washed and bandaged.
We used cefathiamidine for empirical treatment in the early stages of the disease course, and it seemed to be effective according to the test results on the third day. Nevertheless, we later changed to ceftriaxone based on the results of the drug sensitivity test on the forth day. Signs of infection and complete relief of the child's symptoms indicate that treatment plan is correct. This case is highly interesting since it documents A. salmonicida infection caused by shell sh, and the pathogen was con rmed by morphological and molecular tools. This case suggests that physicians should have a high clinical suspicion when dealing with patients with fever of unknown origin, especially when the patient has an epidemiological situation similar to the water environment or aquatic animals.