Adynamic ileus as an atypical manifestation of Staphylococcus aureus meningitis confirmed by metagenomic next-generation sequencing: A case report

Abstract

Staphylococcus aureus is an uncommon cause of bacterial meningitis, and S. aureus meningitis complicated with adynamic ileus has not been previously documented. This report presents a rare case of a man in his late 30s who developed purulent meningitis and intestinal pseudo-obstruction secondary to a skin-derived S. aureus infection. The patient initially presented with persistent fever, headache, and altered mental status. Subsequently, he developed abdominal distention, vomiting, dysuria, and meningeal signs. Laboratory tests revealed hyponatremia and elevated cerebrospinal fluid pressure; however, conventional cerebrospinal fluid culture failed to detect any pathogen. Diagnosis was ultimately confirmed through metagenomic next-generation sequencing, which identified S. aureus as the causative agent. Targeted antimicrobial therapy with vancomycin and meropenem resulted in rapid clinical improvement. This case highlights the importance of considering central nervous system infections in patients presenting with unexplained gastrointestinal and autonomic symptoms. Moreover, it emphasizes the clinical utility of metagenomic next-generation sequencing in identifying pathogens in culture-negative, atypical infections. Early recognition and intervention are essential to improving outcomes in such complex presentations.

Introduction

Staphylococcus aureus is a gram-positive opportunistic pathogen that can cause a wide range of infections, from mild skin and soft tissue infections to life-threatening conditions such as pneumonia, endocarditis, and central nervous system (CNS) infections. ¹ Although meningitis caused by S. aureus is relatively uncommon—accounting for only 1%–9% of all bacterial meningitis cases—it is associated with a high mortality rate of 14%–70%. ² Its clinical manifestations are diverse, including classic signs such as meningeal irritation and elevated intracranial pressure as well as atypical symptoms such as hemiplegia, aphasia, rash, and hyponatremia. ³

Intestinal obstruction is a common clinical condition characterized by impaired passage of intestinal contents, and it is typically classified as mechanical, adynamic (also known as paralytic), or vascular in origin. ⁴ The most frequent causes include postoperative adhesions, tumors, hernias, and mesenteric ischemia. ⁵ However, neurogenic dysfunction can also cause adynamic ileus, particularly when the brainstem or autonomic regulatory centers are involved.^6–8 To date, no cases of intestinal obstruction secondary to S. aureus meningitis have been reported.

In this context, the present report describes a rare and complex case of purulent meningitis and adynamic ileus secondary to skin-derived S. aureus infection, wherein the diagnosis was established via CNS-directed evaluation and confirmed using metagenomic next-generation sequencing (mNGS). ⁹ The case highlights the importance of considering CNS infections in patients with unexplained gastrointestinal symptoms and supports the clinical utility of mNGS in atypical and diagnostically challenging scenarios.

Case presentation

To protect patient privacy, all personal identifiers have been removed, and the patient’s age and dates have been generalized. A man in his late 30s was admitted to the Affiliated Hospital of Southwest Medical University (Luzhou, China) in early 2020 with a 1-week history of progressively worsening intermittent fever. Approximately 1 month before admission, he sustained trauma to the lateral aspect of his right thigh. Since then, he had experienced recurrent headaches and febrile episodes. Initial laboratory tests revealed a white blood cell (WBC) count of 9.75 ×10⁹/L, neutrophil count of 8.51 × 10⁹/L, and neutrophil percentage of 87.3%. Chest computed tomography (CT) showed mild exudative changes in the lower lobes of both lungs, while magnetic resonance imaging (MRI) of the brain and abdomen revealed no abnormalities. Empiric antimicrobial therapy was initiated with intravenous (IV) moxifloxacin at a dosage of 0.4 g once daily (0.4 g, IV drip, qd). On hospital days 2–3, the patient developed intermittent episodes of delirium and somnolence. Neurological examination revealed increased muscle tone, neck stiffness, and positive meningeal signs, including nuchal rigidity. Serum electrolyte analysis showed hyponatremia (Na⁺ level: 119.5 mmol/L) and hypochloremia (Cl⁻ level: 89.2 mmol/L). Based on the suspicion of meningitis, moxifloxacin was discontinued, and empiric antimicrobial therapy was switched to IV ceftazidime, administered at a dosage of 1 g every 8 h (1 g, IV drip, q8h). On day 4, his symptoms worsened. He developed a fever (38.8°C) and experienced persistent headache, fatigue, recurrent delirium, abdominal distention, vomiting, urinary retention, and persistent neck stiffness with positive meningeal signs. Abdominal examination revealed diffuse distension and tenderness, without rebound tenderness or peritoneal signs. Abdominal CT demonstrated features suggestive of adynamic ileus (Figure 1), including bowel distention, gas accumulation, and increased fluid–gas levels in the abdominal and pelvic regions. These findings indicated functional disruption of intestinal motility in the absence of mechanical obstruction. Gastrointestinal decompression and fasting were initiated. Cerebrospinal fluid (CSF) analysis showed an elevated opening pressure (270 mmH₂O), lactate dehydrogenase level of 81.3 U/L, lactate level of 3.99 mmol/L, protein level of 0.923 g/L, and glucose level of 3.18 mmol/L. CSF analysis also showed a WBC count of 57 × 10⁶/L, with 95% mononuclear cells and 5% polymorphonuclear cells; his red blood cell count was 2000 × 10⁶/L. However, conventional CSF culture was negative. Given the clinical suspicion of infection despite negative cultures, mNGS of the CSF sample was performed on hospital day 11 using the PISA platform (Genekey BioTech), a targeted mNGS approach for pathogen detection. The analysis included quality control of sequencing data, removal of human-derived reads, taxonomic classification, microbial abundance estimation, and integration with clinical context to identify the causative pathogen. S. aureus was the only bacterial species detected, with 21,197 mapped reads and an estimated load of 10⁴ copies/mL, supporting its role as the likely pathogen. The patient was started on a combination of IV vancomycin (1 g, IV drip, every 12 h) and meropenem (1 g, IV drip, every 8 h). His clinical symptoms improved significantly within 2 days, and follow-up abdominal CT revealed resolution of the intestinal obstruction. From hospital days 17 to 28, vancomycin therapy was continued. On hospital day 28, the patient was clinically stable and discharged in good condition. At 1-year follow-up, no recurrence or sequelae were observed. A comprehensive summary of the patient’s clinical presentation, diagnostic findings, treatment strategy, and disease progression is illustrated in Figure 2. The reporting of this study conforms to the Case Report (CARE) guidelines. ¹⁰

Figure 1.

Representative computed tomography (CT) and magnetic resonance imaging (MRI) findings during hospitalization. (a) Abdominal CT on admission showing no evidence of intestinal obstruction. (b) Cranial MRI performed during hospitalization revealing no abnormalities despite the presence of central nervous system (CNS) infection symptoms such as neck stiffness and altered mental status. (c) Abdominal CT on hospital day 4 demonstrating features consistent with adynamic ileus, including marked bowel distention, gas accumulation, and multiple air–fluid levels in the abdominal and pelvic regions. Notably, no clear transition point or evidence of mechanical obstruction was observed, further supporting a diagnosis of functional rather than mechanical ileus and (d) Follow-up abdominal CT after targeted antibiotic therapy showing resolution of the ileus and normalization of bowel morphology.

Figure 2.

Clinical timeline of symptom development, diagnostic evaluation, clinical impressions, and therapeutic interventions. Laboratory and imaging tests revealed progressive systemic and neurological involvement. Final diagnosis of Staphylococcus aureus-induced purulent meningitis was confirmed via metagenomic next-generation sequencing (mNGS) of the cerebrospinal fluid (CSF). The patient received intravenous (IV) antimicrobial therapy and supportive care, resulting in full recovery. GI: gastrointestinal; CT: computed tomography; MRI: magnetic resonance imaging; LDH: lactate dehydrogenase; WBC: white blood cell; NEU: neutrophil; Na⁺: sodium ion; Cl⁻: chloride ion.

Discussion

Meningitis caused by S. aureus originating from skin and soft tissue infections is relatively uncommon, accounting for only 1%–9% of all bacterial meningitis cases.^2,11 Its co-occurrence with adynamic ileus is even rarer, with no such cases reported in the literature to date. This atypical clinical combination makes early diagnosis particularly challenging and highlights the importance of including CNS infections in the differential diagnosis of patients presenting with such complex multisystem symptoms. In this case, the diagnostic process was notably difficult due to the absence of focal neurological signs on early imaging and the nonspecific nature of initial laboratory findings. The patient initially presented with intermittent fever and headache, accompanied with mild leukocytosis and neutrophilia, suggesting a systemic bacterial infection. However, both brain and abdominal MRI showed no abnormalities, and chest CT revealed only mild pulmonary exudate, hampering early identification of the infection site. With disease progression, several new symptoms emerged, including altered mental status, meningeal signs, electrolyte imbalance, and gastrointestinal dysmotility, raising suspicion of CNS involvement, possibly related to the brainstem. Although CSF analysis demonstrated clear inflammatory features (elevated opening pressure, increased protein and lactate levels, and CSF leukocytosis), conventional CSF culture was negative, hindering pathogen identification and delaying targeted therapy. On hospital day 11, mNGS of the CSF sample, a diagnostic breakthrough, revealed the presence of S. aureus. This enabled a definitive diagnosis of purulent meningitis, allowing timely initiation of targeted antimicrobial therapy (vancomycin and meropenem). The patient’s symptoms improved rapidly, with resolution of both neurological and gastrointestinal symptoms, validating the diagnosis and therapeutic approach.

From a pathophysiological perspective, this case highlights the critical role of the brainstem in autonomic regulation, including the control of gastrointestinal motility, respiration, and urinary function. ¹² The patient’s multisystem manifestations, including headache, altered mental status, recurrent delirium, abdominal distension, vomiting, urinary retention, and meningeal signs, strongly suggested brainstem dysfunction. These findings reinforce the concept of the gut–brain axis and demonstrate how a CNS infection may lead to downstream autonomic disturbances such as adynamic ileus.^13,14 Clinicians should be aware of this mechanism when evaluating unexplained gastrointestinal symptoms in the context of possible CNS infection. The failure of conventional CSF culture to identify the pathogen in this case reflects a common diagnostic limitation in real-world clinical practice. Although S. aureus is not a fastidious organism, false-negative culture results may occur due to several factors, such as prior antibiotic use, low bacterial load, fastidious growth requirements, and suboptimal specimen handling.^15,16 These factors highlight the diagnostic limitations of conventional microbiological methods, especially in atypical or partially treated infections. In contrast, mNGS facilitated rapid and accurate pathogen identification without relying on viable bacterial growth. ⁹ This case illustrates the increasing value of mNGS in diagnosing CNS infections, especially in the intensive care unit, infectious disease settings, and neurological care settings, where time-sensitive decision-making is critical. mNGS is particularly useful when conventional cultures are negative despite strong clinical suspicion of infection or in urgent situations involving infection with unknown pathogens, viral encephalitis, or potential mixed infections. Nevertheless, mNGS also has certain limitations, including a lack of susceptibility data, potential contamination, and high cost,^9,17 which should be considered during its clinical implementation. Furthermore, the patient’s wide range of nonspecific symptoms, including fever, hyponatremia, altered consciousness, urinary retention, and ileus, could easily be misattributed to abdominal or urological conditions, complicating the diagnostic process. ¹⁸ This highlights the need for systematic clinical reasoning, integration of medical history, monitoring of symptom evolution, imaging analysis, and laboratory data collection to correctly identify the underlying etiology in patients exhibiting complex multisystem presentations.

In conclusion, this case presents a rare but clinically significant combination of S. aureus meningitis complicated with adynamic ileus. It expands our understanding of CNS infection-related autonomic dysfunction and underscores the diagnostic value of mNGS in atypical, culture-negative infections. This case serves as a valuable reference for clinicians, facilitating earlier recognition, more accurate diagnosis, and optimized management of patients with similar complex presentations.