Invasive salmonellosis in two infants in our environment: The importance of contact with domestic reptiles

Dear Editor,

The primary reservoir of Salmonella spp. is the digestive tract of various animals (poultry, cattle and pigs). The main source of infection in humans is through the consumption of animal-derived food products¹ and, less frequently, the intake of contaminated milk formula². Small reptiles, such as the domestic turtle, are relevant reservoirs in our area, with a colonisation rate of 48%, accounting for 6% of salmonellosis in humans³. We present two independent cases of invasive infections by Salmonella spp.

Case 1. A one-month-old infant with a 12-hour history of fever and irritability, with a bulging fontanelle on examination. The family had a domestic turtle of the Emydidae genus and family, from Tennessee and Kentucky, a subspecies of Trachemys scripta troostii. Laboratory tests revealed CRP of 6.3 mg/l, negative procalcitonin and leukocytosis of 24,690/mm³, with neutrophilia. Lumbar puncture (LP) revealed a cloudy fluid with 210 leukocytes/μl (36% polymorphonuclear, 64% mononuclear), glucose concentration of 48 mg/dl and protein concentration of 52 mg/dl. The Gram stain and the FilmArray™ (bioMérieux, Madrid, Spain) of the CSF were negative. Ampicillin, ceftriaxone and aciclovir were started. The blood culture was negative at the end of the incubation period. Salmonella spp. was isolated in the CSF by culture in conventional media with a microbiological profile sensitive to all the antimicrobials tested. Treatment was optimised with intravenous ceftriaxone and ciprofloxacin for one month, after sterile LP at 72 h. A transfontanellar ultrasound was performed, without identifying complications of meningitis. The patient presented with diarrhoea 24 h after the onset of symptoms, remaining afebrile at 48 h. A study of cohabitants, the pet (waste water) and milk formula was carried out. Salmonella spp. with the same microbiological profile as our case was detected in the stool culture of the brother and of the pet. No abnormalities were detected in neurological follow-up or neuroimaging (MRI and cranial ultrasound scan).

Case 2. A two-month-old infant with a 24-hour history of fever, diarrhoeal stools and septic appearance. The family had a pet turtle of the same genus and species as in case 1. After completion of complementary studies and stabilisation, intravenous ceftriaxone was started. Laboratory tests revealed thrombocytosis of 600,000/mm³ and CRP of 56.7 mg/l. The LP was normal. The blood culture and CSF culture were negative. Salmonella spp. was detected in stool culture with conventional media with the same sensitivity phenotype as case 1. Intravenous antibiotic therapy was maintained for five days. A study of cohabitants, milk formula and turtle waste water was carried out, isolating Salmonella spp. in the turtle water and in the stool culture of the grandmother (cohabitant) with the same sensitivity as our case. The patient responded to treatment without complications.

The genus Salmonella is an important cause of acute gastroenteritis, usually self-limiting. In infants and immunocompromised individuals, it can cause severe extraintestinal manifestations (sepsis, meningitis and secondary focal infections)⁴. On suspicion of salmonellosis in these cases, antimicrobials should be administered early. Third generation cephalosporins (for at least four weeks) are the treatment of choice in meningitis caused by Salmonella spp⁵. A neuroimaging study is recommended, even in neurologically asymptomatic patients responding to antibacterial treatment, due to the high risk of complications that would justify a longer duration of antibiotic therapy⁶. A follow-up LP should be performed 48−72 h after treatment, and in the event of persistent Salmonella in the CSF, some authors propose combination therapy with intracellular antimicrobials, such as quinolones⁷. Ciprofloxacin has excellent bioavailability at the meningeal level due to its lipid solubility, which allows it to cross the blood-brain barrier, reducing mortality, the risk of relapse and complications. Other authors recommend initial combination therapy with third generation cephalosporins and quinolones for a minimum of three weeks from CSF sterilisation⁸.

Given the high risk of invasive salmonellosis after contact with domestic reptiles and the increasing incidence in our setting, children under five years of age, immunocompromised patients, pregnant women and the elderly are advised to avoid contact with reptiles, consistent with the recommendations of the Centers for Disease Control and Prevention (CDC)⁹. In Spain, there is a surveillance protocol for salmonellosis established by the Epidemiological Surveillance Network. When a case is detected, it must be reported and a complete epidemiological study is essential in order to determine the origin. The appropriate preventive measures must be implemented to avoid this type of infection, such as the control of import quotas, the promotion of educational campaigns and ensuring that businesses comply with the regulations¹⁰.

Funding

This study has received no funding nor has it been presented at previous congresses.