ABSTRACT
A previously healthy 3-month-old girl was admitted to the hospital after 1 day of fever, decreased oral intake, irritability, lethargy, and decreased activity. Examination disclosed a bulging anterior fontanelle, tachycardia (heart rate of 160 beats/minute), and urate crystals in her diaper. Lumbar puncture revealed meningitis. She was treated with broad-spectrum antibiotics and fluids. A urine culture was negative, but blood and cerebrospinal fluid cultures came back positive for Salmonella species, nontyphoid. During her hospitalization, she developed seizures but quickly improved with treatment and made a complete recovery with no sequela. Additional inquiry disclosed that the baby spent several days a week at her grandparents' house, where they raised chickens and ate fresh chicken eggs, which are well-known carriers for Salmonella.
KEYWORDS: Fresh chicken eggs, nontyphoidal Salmonella meningitis, seizures, transmission of NTS
We describe a case of nontyphoidal Salmonella (NTS) meningitis in a 3-month-old girl who presented with fever. It is essential to recognize this infective form of Salmonella promptly, because adequate intervention is required for better prognosis. Important interventions include rapid diagnostic tests to limit the disease.
CASE DESCRIPTION
A 3-month-old girl was admitted with a 1-day history of high temperature, poor feeding, irritability, and lethargy. Her birth was uncomplicated and she had been well since. There were no reports of diarrhea, vomiting, seizures, or sick contacts. On examination, she was awake and alert but fussy. She was febrile to 100.5°F with a respiratory rate of 56 breaths/min and a pulse rate of 160 beats/min. She had bulging anterior fontanelles with no neck stiffness. The rest of the physical exam was unremarkable. The baby lived with her parents and older sister, and there were no pets or farm animals at home. Several times a week, she stayed at her grandparents' house, where they raised chickens. Her mother denied any direct contact with the chickens but admitted that the family regularly consumed fresh chicken eggs. None of the family members experienced any diarrhea prior to presentation.
Quantifiable lab results are summarized in Table 1. Her serum white blood cell count was 31.0 × 109 cells/L. The cerebrospinal fluid (CSF) was clear and colorless, with a white blood cell count of 496/mL (differential of 74% neutrophils and 21% lymphocytes) and a red blood cell count of 7/mL. The CSF protein was 80.5 mg/dL and glucose was 18 mg/dL. CSF gram stain showed rare amounts of gram-negative rods. The CSF herpes simplex virus test was negative. On day 3 of her hospitalization, she had a 25-minute episode of new-onset seizure requiring lorazepam 0.3 mg and a levetiracetam 50 mg/kg load. A continuous video electroencephalogram for 22 hours was negative. Magnetic resonance imaging (MRI) showed purulent material in the right occipital horn without abscess formation (Figure 1) and dural enhancement on the frontal and parietal convexities bilaterally (Figure 2). Neurosurgery recommended antibiotics and no operative management. She was started on levetiracetam 25 mg/kg twice daily for seizure prophylaxis.
Table 1.
Results of the patient's laboratory investigations
| Variable | Results |
|---|---|
| White blood cell count (cells/L) | 31 × 109 |
| Hemoglobin (g/dL) | 10.1 |
| Platelet count (cells/L) | 735 × 109 |
| C-reactive protein (mg/L) | 155 |
| Sodium (mEq/L) | 135 |
| Potassium (mEq/L) | 3.6 |
| Blood urea nitrogen (mg/L) | 9 |
| Creatinine (mg/L) | 0.24 |
| Albumin (g/dL) | 3.0 |
| Total protein (g/dL) | 6.8 |
| Total bilirubin (mg/dL) | 0.1 |
| Alanine aminotransferase (IU/L) | 17 |
| Alkaline phosphatase (IU/L) | 152 |
| Cerebrospinal fluid | |
| Appearance | Clear |
| White blood cell count (mL) | 496 |
| Lymphocytes (%) | 21 |
| Glucose (mg/dL) | 18 |
| Protein (mg/dL) | 80.5 |
| Red blood cell count (mL) | 7 |
Figure 1.
MRI demonstrating dependent restricted diffusion in the area of the right occipital horn, which likely reflects the presence of purulent material.
Figure 2.
MRI demonstrating dural enhancement on the frontal and parietal convexities bilaterally, which is consistent with meningitis.
A diagnosis of sepsis was made, and the patient was empirically started on intravenous ceftriaxone 100 mg/kg once daily, intravenous vancomycin 20 mg/kg every 6 hours, and intravenous gentamicin 7.5 mg/kg once daily. After 2 days, Salmonella nontyphoid species grew from both the blood and CSF culture with sensitivities for ampicillin. Empiric antibiotics of ceftriaxone, vancomycin, and gentamicin were discontinued and she was started on ampicillin 400 mg/kg/day four times per day. On hospital day 6, ampicillin was stopped and she was switched back to intravenous ceftriaxone 100 mg/kg/day twice daily after review of the literature showed that complication rates may be higher with ampicillin alone.
She quickly improved over the next couple of days with softening of the anterior fontanelles and improved feedings. By hospital day 3, she defervesced and remained afebrile with stable vital signs and no further seizure activity throughout the rest of her hospitalization. On hospital day 4, repeat lumbar puncture showed improved, but not yet normalized, CSF studies. Repeat blood and CSF cultures were negative. By hospital day 14, she had near normalization of spinal fluid parameters, which essentially normalized by hospital day 19. Repeat MRI performed prior to hospital discharge indicated near resolution of purulence. A hearing screen was passed prior to discharge. Intravenous ceftriaxone was continued for a total of 4 weeks. She made a complete recovery with no sequelae to date. Her developmental milestones are currently appropriate for age.
DISCUSSION
According to the Centers for Disease Control and Prevention, NTS is usually transmitted through the consumption of contaminated food or water, with documented associations with home-grown poultry and eggs in the USA.1 Compared to 2010 to 2012, the incidence of NTS infection in 2013 decreased 9% in the USA, although 2013 rates were similar to 2006 to 2008 levels.2 Worldwide, NTS is one of the leading causes of bacterial diarrhea, with around 5% to 10% of cases developing into invasive infections such as meningitis or bacteremia.3 Infants and older immunosuppressed adults are highly susceptible. Although a recent review indicated that approximately 106 to 108 NTS organisms must be ingested to cause symptomatic disease in healthy adults, the number needed for infants is significantly less. Controlling the transmission of Salmonella is difficult due to its high tolerance to environmental stress, widespread distribution, emerging multidrug resistance, and adaptability from a microbial perspective.4
NTS can exist as a carrier state in asymptomatic pregnant women. The risk occurs when the newborn has a relative immune deficiency state, allowing transplacental transmission.5 Additionally, no specific screening test or method exists to identify NTS in pregnant women, possibly due to the rarity of its incidence. Some strains of NTS can also colonize the mammary glands and be transmitted through breast milk, which is disconcerting considering that breastfeeding also confers a protective effect on infants with regard to salmonellosis infection.6
The detection of neonatal meningitis due to NTS has been steadily rising in underserved areas such as Africa, where the increased incidence is related to risk factors associated with NTS including HIV infection, malnutrition, malaria, and anemia. Though the case fatality rate of NTS varies widely from 0% to 72%, the average is 20.6%.7 This may be due to a documented pattern of ceftriaxone and fluoroquinolone resistance emerging in Kenya and other West African regions; thus, empiric treatment for this suspected disease is becoming even more challenging.8
Although current research speculates on the mechanism of NTS transmission, the data are sparse on whether NTS resides in animals (such as chickens), humans, or the environment and how it is transmitted to susceptible individuals. Thus, intervention has been aimed at treating the illness after the fact. Given the need to prevent it, research is being done on the possibility and efficacy of future vaccines against the most common pathogens in this genus. Borstein et al9 proposed a mathematical model to predict how a bivalent conjugate vaccine could have similar effects as a NTS vaccine would in Mali, West Africa. Results from the model concluded that implementing a vaccination program analogous to a preexisting Haemophilus influenza type B program would drastically reduce the incidence as well as mortality of infective NTS in children.9 Although this report occurred in a setting where NTS is much less common, bringing light to its worldwide pathogenicity may help highlight the importance of having a vaccine that could prevent many Salmonella infections.
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