"Message from a turtle": otitis with Salmonella arizonae in children: Case report.

RATIONALE: Salmonella enterica subsp arizonae is a common gut inhabitant of reptiles (snakes are the most common reservoir, but it also occurs in turtles). Alhough human cases owing to this organism are exceedingly rare, it may occasionally infect young infants and immunocompromised individuals with a history of intimate associations with reptiles. Our case is the 20th one among the infections with S arizonae in children, but the 2nd one of otitis and the first of mastoiditis. The other cases had different anatomical locations, such as gastroenteritis, osteomyelitis, meningitis, ankle infection, wound infection, and sinusitis. PATIENT CONCERNS AND DIAGNOSIS: We report a rare case of otitis with Salmonella in a previously healthy adolescent, which was most likely acquired after bathing in a lake. The ear infection was complicated with mastoiditis. Audiometric testing showed a moderately conductive hearing loss (60 dB on pure-tone average). INTERVENTION: Standard therapy for S arizonae was initiated. The surgery revealed a "hidden" cholesteatoma. Surgical management comprised of canal wall up mastoidectomy with attico-antrotomy and posterior tympanotomy followed by tympanoplasty. OUTCOMES: Daily postoperative dressing care of the incision, along with antibiotic lavage of the external auditory canal packing, ensured a favorable evolution. The functional gain was important; the 1-month postsurgical pure tone audiogram indicated nearly normal hearing (a mean of 25 dB for air conduction thresholds). LESSON: Salmonella enterica serotype arizonae is a rare cause of human infection, being a common organism in reptiles, like snakes and turtles. Young children are at a particular risk for acquiring such infections. Our study might encourage further epidemiologic investigations into these infections to generate a more effective strategy among public health agencies.

Introduction

Salmonella is a Gram-negative facultative anaerobic bacilli that belongs to the Enterobacteriaceae family, and it is usually responsible for food-borne diseases. Approximately 99% of human isolates are Salmonella enterica subsp enterica. Less-frequent subspecies are: S enterica subsp houtenae (IV), S enterica subsp diarizonae (IIIb), S enterica subsp salamae (II), S enterica subsp arizonae (IIIa), and S enterica subsp. indica (VI). The Arizona group, subgenus III of genus Salmonella, has received various names (Salmonella arizonae, Arizona arizonae, Arizona hinshawii) and was finally reclassified as S enterica subsp arizonae (monophasic strains, IIIa) and S enterica subsp diarizonae (diphasic strains, IIIb). Subspecies IIIa and IIIb are still identified as “Arizona” by some automated ID systems. The distinguishing biochemical features include the ability to ferment lactose, utilize malonate, liquefying gelatin, and the inability to grow in the presence of KCN.[

Here, we describe a patient who developed otitis with S arizonae after bathing in a lake. This should be the first report of an immunocompetent child who developed otitis complicated with mastoiditis.

Case report

A 16-year-old boy presented to our pediatric clinic (“Sf. Maria” Children's Hospital, Iasi, Romania) because of discharge from his right ear. No other associated symptoms (fever, pain, or headache) were present. There were no other pathological clinical signs present at the physical examination. The boy lives in a village, within a working class family, in North East Romania. His history revealed that this is the third episode of otorrhea in the last 6 months. One episode required antibiotic treatment (with Amoksiklav) and the other had a spontaneous remission. Routine blood tests did not reveal any abnormalities. The routine microscopic examination of urine and feces as well as the immunity tests was normal.

An otomicroscopic left ear examination revealed purulent secretion in the external auditory canal with skin inflammation. After the ear suction, a soft polypoid mass appeared through a posterior-superior perforation of the tympanic membrane. Inflammation and polypoid degeneration of the middle ear mucosa, as well as otic erosion, were visible, suggesting a chronic suppurative otitis (Fig. 1). The presence of purulent secretions is suggestive for a bacterial etiology, which needs to be confirmed through bacteriological examination.

Figure 1

Local ear examination.

Audiometric testing showed a moderately conductive hearing loss (60 dB on pure-tone average).

Microscopic examination of the direct Gram-stained smear of ear secretion showed inflammation and Gram-negative bacilli. Isolation was done by plating on blood with 5% sheep agar and MacConkey agar, respectively. After overnight incubation on MacConkey agar, the isolate showed lactose-negative colonies that became pink colonies after another 24-hour incubation. The Gram-stain smear of the MacConkey culture showed Gram-negative bacilli (Fig. 2). With the conventional minimal biochemical test, the isolate was identified as Salmonella and it showed agglutination with Salmonella polyvalent O antiserum. This was further confirmed by 3 biochemical identifications: the first one, performed with NBP32 (Microscan, Beckman-Coulther) found a Salmonella/Arizona group; the second one performed with MALDI-TOF mass spectrometry identified Salmonella spp; the third one, performed with Vitek2 (Bio-Merieux) confirmed S enterica subsp. diarizonae. The serotyping (performed at National References Laboratory, INC Cantacuzino Bucuresti, Romania) identified the serotype O:38:r:- and lisotyping found “lysed by phage O1,” which are unique to the S enterica subsp diarizonae type (thus excluding other possibilities from the analysis). Therefore, the final taxonomic framing according to the WHO taxonomy[ confirmed the etiology of otitis in this case, as being attributable to S enterica subsp diarizonae.

Figure 2

Gram-stain smear of ear secretion showing two polymorphonuclear neutrophils and Gram-negative bacilli Salmonella arizona (1000×).

The isolate was subjected to antimicrobial susceptibility testing by disk diffusion method and minimal inhibition concentration, according to the recommendation of the Clinical and Laboratory Standards Institute,[ and was found sensitive to ampicillin, ciprofloxacin, trimethoprim-sulfamethoxasol, and third-generation cephalosporin.

Following confirmed isolation of this organism from the ear discharge, we came back to the patient's history to trace any possible contact with reptiles. We found out that the boy was bathing in a village lake, where turtles were common inhabitants.

A contrast-enhanced computed tomography scan of the head, following the clinical diagnosis of chronic suppurative otitis, revealed: ethmoidal cells partially filled by a hyperdense material, polypoid thickening of the right frontal, maxilar and sphenoidal sinus mucosa, mastoid cells filled with a solid density material, and trabecular destruction (Fig. 3).

Figure 3

Craniocerebral computed tomography scan.

The patient received local and intravenous antibiotics (ceftriaxone 1 g/day) for 10 days, as well as surgical treatment. Surgical management comprised of canal wall up mastoidectomy with attico-antrotomy and posterior tympanotomy followed by tympanoplasty. The mastoid cavity and middle ear was occupied by a white pearly mass—cholesteatoma—surrounded by polypous degeneration of the mucosa and puss-like fluid. The short process of the incus, as well as the superior part of the malleus head, appeared eroded. After drilling, the incus with a diamond burr the ossicular chain was reconstructed by incus reposition. The scutum erosion was drilled with diamond burr; the defect was repaired using conchal cartilage, and an underlying tympanoplasty was performed. Daily postoperative dressing care of the incision line, along with antibiotic lavage of the external auditory canal (EAC) packing ensured a favorable evolution.

The bacterial culture from the ear liquid collected during the operation was negative. The clinical recovery was very good. The functional gain was important, with the 1-month postsurgical pure tone audiogram indicating nearly normal hearing (a mean of 25 dB for air conduction thresholds)

Discussion

The Arizona group organism was first reported in infected reptiles in 1939 by Caldwell and Ryerson.[ It was initially considered to be pathogenic only in reptiles, especially in snakes (78.8% of them harboring it),[ but later it was discovered to be responsible for severe outbreaks in turkeys and sheep.[ Other animals, including poultry, rats, and dogs, have also been involved in human infection.[

The first case of human infection by S arizonae (presenting with gastroenteritis) was recognized in 1944.[ The most common form of infection is gastroenteritis[ with 73% of illnesses occurring in the first 3 months of exposure. It requires an incubation of 2 to 48 hours and is characterized by fever, headache, abdominal pain, vomiting, and diarrhea. Stools are expulsive, copious, and frequently mixed with blood and mucus.[ There is a substantial risk of dehydration owing to the severity of diarrheal illness. Molecular techniques, such as a Salmonella-specific PCR, may prove a valuable tool for confirming the etiology, allowing timely implementation of appropriate therapy, to prevent morbidity and mortality owing to this rare human pathogen.[

Arizona group infection is uncommon among adult patients, having an in-hospital mortality rate of 5.6%[ and it usually occurs in individuals with underlying disease or immunodeficiency. A carrier state is not uncommon, and a recurrence of S enterica subsp arizonae sepsis in immunocompromised patients after 1 year has been reported.[ These infections are often invasive and lead to complications such as meningitis, septicemia, and osteomyelitis.[ Lee et al reported in 2016[ the largest case series infected by S arizonae (in Taiwan): 18 adults of a total of 485 patients with Salmonella species infection, during a 1-year period.

The reported infection in infants occurs as a result of intimate contacts with reptile pets. Little information is available on their distribution in extraintestinal infections, particularly in children. Blood and urine were the most common extraintestinal sites.

Abbot et al retrospectively analyzed salmonellae data (>75,000 isolates) collected by a large state laboratory during 25 years. The Arizona group (subspecies IIIa, IIIb), had isolate totals of 463 (35%) and 443 (33%), respectively. Overall, patients were more likely to have had subspecies II–IV isolated from feces (n = 947) than from an extraintestinal site (n = 395; P < .001). Only patients from whom subspecies IIIa were isolated were equally likely to have an extraintestinal infection as opposed to diarrhea only. Sources of extraintestinal infections included cerebrospinal fluid, blood, urine, cervix, bile, wounds and abscesses, and the respiratory tract.[

Even if infection occurs more often than in adults, there are not many case reports of S arizonae infection in children either: to the best of our knowledge only 20 pediatric patients, below 18 years of age, from 1952 until now[ (Table 1) have been reported. These patients have generally been older children, some of them having an underlying severe disease such as leukemia, histiocytosis, SLE, Netherton syndrome, or sickle cell disease. Other epidemiologic infectious disease studies have included children with S arizonae among other bacterial infections: Kolo et al[ have found 9 pediatric cases with bacteremia with S arizonae (5 of them being infected with HIV), of 102 bateriemic patients during a 6-month period in Nigeria. Meyer Sauteur[ identified 9 cases of S arizonae among 182 children with reptile-associated salmonellosis, most of them (177 children) being previously healthy children.

Table 1

Salmonella enterica subsp arizonae human infections with varying clinical pictures.

Abbots’ data[ showed an equivalent number of cases (Salmonella subspecies II-IV) in children <1 year of age and in persons 11 to 60 years of age (from isolates obtained from fecal samples), but the prevalence of extraintestinal infections occurred in the older patient groups. These patients, as owners or handlers of exotic pets, may be exposed to a greater inoculum, whereas children <1 year primarily acquire infections secondarily from fomites or surfaces, such as sinks used previously to bathe reptiles or by transmission from handler to child.[

There were no reported human S enterica subsp arizonae and diarizonae infection in Romania. The cases that have been reported by Köbölkuti et al[ were only in Viper snakes (both captive and free living).

Conclusions

S enterica serotype Arizonae is a rare cause of human infection, being a common organism in reptiles, like snakes and turtles. It can cause not only gastroenteritis but also osteomyelitis, otitis, mastoiditis, meningitis, osteoarthritis, or septicemia. Young children are at a particular risk of acquiring such infections. Therefore, proper history should be obtained in such cases. These results might encourage further epidemiologic investigations into these infections. In order to use this information to generate a more effective strategy that public health agencies and the exotic pet industry can implement to reduce the extent of disease caused by these organisms.