CASE REPORT |
https://doi.org/10.5005/jp-journals-10081-1440 |
Common Bane: Uncommon Bug
1,2Department of Pediatrics, North Bengal Medical College & Hospital, Siliguri, West Bengal, India
3,4Department of Microbiology, North Bengal Medical College & Hospital, Siliguri, West Bengal, India
Corresponding Author: Madhumita Nandi, Department of Pediatrics, North Bengal Medical College & Hospital, Siliguri, West Bengal, India, Phone: +91 9433166790, e-mail: madhumitabanik@rediffmail.com
Received: 25 June 2024; Accepted: 17 July 2024; Published on: 05 November 2024
ABSTRACT
Aim and background: Staphylococcus pseudintermedius is an emerging zoonotic pathogen of the Staphylococcus group, mostly found in the skin and soft tissue of domestic animals, especially dogs. Ever since the first human infection was described in 2005, a few other reports have described this in association with skin and other superficial infections in humans, but invasive bloodstream infection has rarely been reported.
Case description: We describe the case of a 10-month-old male baby presenting with fever, irritability, convulsions, and bulging fontanelle diagnosed as acute pyogenic meningitis due to S. pseudintermedius.
Conclusion: S. pseudintermedius is an emerging pathogen of concern.
Clinical significance: This is probably the first case report of S. pseudintermedius causing invasive infection in an infant from India. Awareness of the possibility of this pathogen causing invasive infections is crucial for timely detection and successful treatment with appropriate antibiotics.
Keywords: Case report, Infant, Meningitis, Staphylococcus pseudintermedius
How to cite this article: Nandi M, Barman P, Datta AP, et al. Common Bane: Uncommon Bug. Pediatr Inf Dis 2024;6(4):140–142.
Source of support: Nil
Conflict of interest: None
Patient consent statement: The author(s) have obtained written informed consent from the patient’s parents/legal guardians for publication of the case report details and related images.
INTRODUCTION
Staphylococcus pseudintermedius is an emerging zoonotic pathogen. Originally found in a variety of wild and domestic animals,1 the first human case was described in 2005.2 Since then, several cases involving this pathogen have been described in the literature, mostly skin, soft tissue, and other superficial infections in adults and elderly population living in close proximity to animals.3-6 We hereby report the case of an infant developing acute meningitis caused by this zoonotic pathogen.
CASE DESCRIPTION
A 10-month-old male infant, born to nonconsanguineous parents, presented with moderate-grade intermittent fever, irritability, and refusal to feed for 5 days, as well as multiple episodes of generalized convulsions over the last 2 days. There was no history of rash, loose stools, ear discharge, or contact with any known case of tuberculosis. He was born at term by spontaneous vaginal delivery, was immunized up to date according to government schedule, and had normal developmental milestones in all four domains. He belonged to a family of farmers whose dwelling areas were in close vicinity of place where farm animals were kept. They also had a domesticated street dog that lived inside the premises of their house.
On examination, he was febrile and irritable, with a bulging anterior fontanelle. His heart rate was 125/min, respiratory rate was 46/min, oxygen saturation was 94%, capillary refill time was 2 seconds, and blood pressure (BP) was 76/52 mm Hg. His anthropometric measurements, including head circumference (HC), were within normal limits [weight—10.2 kg, length—71 cm, HC—46 cm, and left mid-upper arm circumference (MUAC)—14 cm]. Capillary blood glucose by glucometer was 86 mg/dL. The general survey from head-to-toe did not reveal any remarkable abnormality. Infantile Glasgow Coma Scale (GCS) on admission was E3V4M5. Signs of meningeal irritation were absent. Examination of cardiovascular, respiratory, gastrointestinal, and genitourinary systems did not reveal any abnormality.
With a clinical diagnosis of acute meningoencephalitis, he was started on ceftriaxone (100 mg/kg) and vancomycin (60 mg/kg) along with other supportive measures after sending blood and other body fluid samples for relevant cytological, biochemical, and microbiological investigations. The investigation reports are summarized in Table 1, which are consistent with a diagnosis of acute pyogenic meningitis with/without septicemia.
| Parameter (Unit) | Result | Parameter (Unit) | Result |
|---|---|---|---|
| Hemoglobin (g/dL) | 10.2 | Serum urea (mg/dL) | 45 |
| TLC (×103/µL) | 26.50 | Serum creatinine (mg/dL) | 0.3 |
| DC | N 75, L 22, E 03, M 00, B 00 | Serum bilirubin (mg/dL) | 1.2 |
| Platelet count (×103/µL) | 270 | SGPT (IU/L) | 54 |
| CRP (mg/L) | 230 | SGOT (IU/L) | 36 |
| CSF protein (mg/dL) | 96 | Urine R/E | WNL |
| CSF sugar (mg/dL) | 26 | Urine C/S | No growth |
| CSF cell count (/mm3) | 1,500 (N 80%, L 20%) | Dengue IgM | Negative |
| CSF C/S | No growth | Malarial parasite | Not found |
| Blood calcium (mg/dL) | 9.2 | Scrub typhus IgM | Negative |
| Blood sugar (mg/dL) | 96 | Leptospira IgM | Negative |
| Serum Na+ (mEq/L) | 130 | JE IgM | Negative |
| Serum K+ (mEq/L) | 3.5 | HSV DNA PCR | Negative |
| Serum albumin (mg/dL) | 3.9 | CSF for KOH mount and India ink stain | No fungi detected |
C/S: culture and sensitivity; CRP: C-reactive protein; CSF: cerebrospinal fluid; DC: differential count; DNA: deoxyribonucleic acid; HSV: herpes simplex virus; IgM: immunoglobulin M; JE: Japanese encephalitis; KOH: potassium hydroxide; PCR: polymerase chain reaction; R/E: routine examination; SGOT: serum glutamate oxaloacetate transaminase; SGPT: serum glutamate pyruvate transaminase; TLC: total leukocyte count; WNL: within normal limits
The blood culture done in BACTEC FX40 (BD diagnostic) reported flag positive within 24 hours, following which organism identification and antibiotic sensitivity were done by VITEC 2 (bioMérieux). It revealed the pathogenic organism as S. pseudintermedius (94% probability), resistant to cefoxitin spectrum (as a proxy for methicillin resistance), with intermediate sensitivity to vancomycin [minimum inhibitory concentration (MIC) = 16]. Based on this report, vancomycin was continued.
The baby gradually started to improve from day 3 of admission, becoming afebrile with improvement in sensorium with no more convulsions. Oral feeding could be started from day 6. Magnetic resonance imaging (MRI) done on day 6 revealed hyperintensities with restricted diffusion involving both cerebral cortex and corpus callosum, with effacement of sulci, suggestive of acute encephalitis and bilateral subdural effusion. As per recommendations, intravenous antibiotics were planned to be given for 6 weeks. Auditory and visual evoked responses and electroencephalogram (EEG) done around 4 weeks of admission were reported within normal limits. The baby was discharged after completion of 6 weeks of antibiotics. A repeat MRI done after 12 weeks revealed remarkable subsidence of subdural effusion.
The baby is on regular follow-up at our institutional District Early Intervention Centre (DEIC) and is doing well.
DISCUSSION
S. pseudintermedius is a gram-positive, coagulase-positive, nonmotile, nonspore-forming cocci. It is a facultative anaerobe. Its natural habitat is the skin and mucous membranes of pets and domestic animals, where it dwells as a commensal.1-5
As per the present understanding of molecular diagnostics, S. pseudintermedius is one of the three species of Staphylococcus intermedius group (SIG), other two being S. intermedius and Staphylococcus delphini, based on certain common phenotypic and biochemical characteristics.1-3
First human infection with this zoonotic pathogen was described in 2005, the organism colonizing an implantable cardioverter-defibrillator (ICD) in a 60-year-old man with multiple comorbidities.2 Since then, human infections have mostly been described as skin and soft tissue infections or implanted device-related colonization or infection in vulnerable adults living in close proximity to infected canines. The few case reports of invasive infections, such as pneumonia, septicemia, meningitis, and brain abscess, have mostly been reported in vulnerable adults and elderly.4,5 In 2010, Durdik et al. from Canada reported the case of an 11-month-old infant suffering from meningitis in whom S. intermedius was isolated from cerebrospinal fluid (CSF).6 But to the best of our knowledge, this is the first report of S. pseudintermedius causing pyogenic meningitis in an infant from India.
Molecular diagnostics are considered the gold standard of identification of this emerging species, but facilities for such tests are limited, especially in resource-limited settings like ours.
We used BACTEC Fx40 for culture and VITEC 2 (bioMérieux) for species identification and antibiotic sensitivity. BACTEC showing flag within 24 hours of incubation is indicative of high bacterial load. The result of VITEC 2 is based on the extent of the match with a unique biochemical and phenotypic reaction pattern. The identity of a possible organism is assigned with a grading according to confidence levels (and probability%) of the match—excellent (96–99%), very good (93–95%), good (89–92%), acceptable (85–88%), low discrimination (2–3 organisms with split ID), inconclusive (>3 organisms), and unidentified organism. So, 94% probability falls in very good probability category.
Consistent clinical features, with a high organism load and VITEC 2 reporting single organism with 94% probability, established the causal association between this rare pathogen and acute bacterial meningitis/septicemia in the index case.
Some previous publications have also attempted a combination of biochemical and phenotypic characteristics to identify this species.5-8
Although the CSF culture was negative for any bacterial growth, based on clinical features and CSF biochemistry and cytology, it was most probably a diagnosis of concomitant acute bacterial meningitis along with septicemia. Some previous publications have also cited different reasons for this nonyield, such as low CSF volume, slow growth of organisms, and low CSF bacterial load.9,10
Some studies have reported how treatment of infection by this pathogen is becoming challenging due to emerging methicillin resistance.11 The index case also demonstrated resistance to wide array of antimicrobials but fortunately responded to vancomycin, resulting in complete eradication and cure.
CONCLUSION
Correct identification of the species with the use of more widely available, rapid, and easy-to-use tools is required to produce a large database for future studies and to establish management guidelines for infections caused by S. pseudintermedius.
Clinical Significance
S. pseudintermedius is an emerging pathogen of concern. Awareness of the possibility of this pathogen causing life-threatening infections, especially in the vulnerable age group, is crucial for timely detection and successful treatment. More concerted efforts are needed to fill the knowledge gap and to better understand the true epidemiology of this novel pathogen.
ORCID
Madhumita Nandi https://orcid.org/0000-0002-0415-589X
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