Severe methicillin-resistant Staphylococcus aureus (MRSA) sepsis with hematogenous pulmonary abscesses and humeral osteomyelitis in a previously healthy child: a case report

Abstract

Background

Staphylococcus aureus is a major pathogen responsible for both community-acquired and hospital-acquired infections. However, disseminated infections complicated by pulmonary abscesses and osteomyelitis are rare in otherwise healthy children.

Case presentation

We report a case of a previously healthy 12-year-old boy who presented with a 7-day history of cough and a 5-day history of fever and progressive swelling of the left upper limb after self-manipulating a right forearm furuncle. Physical examination and imaging revealed multifocal pulmonary abscesses and osteomyelitis of the left humerus. Blood cultures confirmed the presence of methicillin-resistant Staphylococcus aureus (MRSA). Despite initial empirical antibiotic therapy, the patient’s symptoms persisted, necessitating four surgical interventions. The first two surgeries involved debridement with antibiotic-loaded calcium sulfate implantation. Nineteen months later, due to nonunion of the proximal humerus, the patient underwent open reduction and internal fixation with autologous iliac bone grafting, followed by subsequent removal of the internal fixation two years later. This staged approach, starting with infection control followed by delayed reconstruction, led to successful bone union, with complete resolution of the pulmonary abscesses on follow-up imaging.

Conclusion

This case highlights the potential for rapid hematogenous dissemination of Staphylococcus aureus leading to complex multi-organ involvement even in healthy pediatric patients. Prompt diagnosis, multidisciplinary management, and combined surgical and antibiotic therapy are critical for favorable outcomes.

Clinical trial number

Not applicable.

Introduction

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) has become an increasingly important cause of infection, with a steadily rising number of reported cases. While CA-MRSA most frequently manifests as skin and soft tissue infections (SSTIs) [1], it can also cause severe invasive diseases, such as pediatric bacteremia and metastatic complications, which require prompt and aggressive treatment to prevent adverse outcomes [2].

However, hematogenous dissemination of CA-MRSA resulting in concurrent pulmonary abscesses and osteomyelitis is rare, particularly in otherwise immunocompetent children. Such dissemination is often associated with metastatic seeding and may be driven by the highly aggressive virulence of strains producing Panton-Valentine leukocidin (PVL) [3].

Given the risk of rapid clinical deterioration in such disseminated infections, timely diagnosis, comprehensive imaging assessment, and multidisciplinary management are essential for optimal outcomes [4]. Early recognition of both pulmonary and osteoarticular involvement enables prompt initiation of targeted antibiotic therapy and appropriate surgical intervention, thereby reducing the risk of long-term complications [5, 6].

Here, we report a rare case of a previously healthy 12-year-old boy who developed CA-MRSA sepsis complicated by bilateral cavitary pulmonary abscesses and proximal humeral osteomyelitis after manipulation of a skin furuncle. This case underscores the importance of early clinical vigilance, comprehensive diagnostic evaluation, and timely integration of surgical and medical management in complex pediatric CA-MRSA infections.

Case presentation

A previously healthy 12-year-old boy presented with high-grade fever and progressive swelling with pain in the left upper limb. Approximately seven days before admission, he developed a furuncle on the right forearm, which he manually squeezed and ruptured. Shortly thereafter, he experienced paroxysmal cough with right-sided chest pain, aggravated at night and during deep inspiration. Five days later, he developed high fever (peak temperature 39.2 °C), decreased appetite, and restricted mobility of the left upper limb due to worsening swelling and pain. He had no prior medical, family, or psychosocial history.

On admission (D0), physical examination revealed fever (39 °C), tachycardia (159 bpm), and tachypnea (38 breaths/min). The left upper arm circumference was 30 cm compared to 25 cm on the right, indicating marked swelling. The overlying skin was erythematous, warm, and tender, with restricted range of motion at the shoulder and elbow. The right forearm showed a crusted lesion, consistent with a healing skin infection. Palpation of the skeletal bones revealed tenderness and swelling in the left upper limb, particularly around the proximal humerus, consistent with osteomyelitis. Cardiac auscultation revealed no significant murmurs or abnormal heart sounds, suggesting no signs of infective endocarditis. Lung auscultation revealed diminished breath sounds and scattered dry rales. No cervical lymphadenopathy or hepatosplenomegaly was detected, and neurological examination was unremarkable.

Laboratory and imaging findings

On hospital day 1 (D1), laboratory tests showed leukocytosis (WBC 18.9 × 10⁹/L), elevated C-reactive protein (196.2 mg/L), and procalcitonin (4.1 ng/mL). Liver and renal function, myocardial enzymes, coagulation profile, and immunologic screening were within normal limits. Specifically, immunologic screening was performed to rule out primary immunodeficiencies due to the severity of the infection in an otherwise healthy child. The tests included measurement of immunoglobulin levels, which were as follows: IgG 9.55 g/L (normal range: 7–16 g/L), IgA 1.87 g/L (normal range: 0.7–4 g/L), IgM 0.53 g/L (normal range: 0.4–2.3 g/L), and IgE 93.2 IU/mL (normal range: ≤200 IU/mL). Flow cytometry for lymphocyte subsets revealed normal distributions: total T lymphocytes 73.17% (normal range: 50–84%), total B lymphocytes 14.20% (normal range: 5–18%), NK cells 16.75% (normal range: 7–40%), and NKT cells 10.43% (normal range: 0.3–8%). The T-helper/T-suppressor ratio was 0.95 (normal range: 0.71–2.78). These results were within normal reference ranges, and there was no evidence of immunodeficiency. Respiratory pathogen tests, including viral nucleic acid assays, Mycoplasma pneumoniae serology, galactomannan (GM), and (1→3)-β-D-glucan (G test), were negative. Paired blood cultures obtained at admission grew Staphylococcus aureus. The antibiotic susceptibility testing (AST) of the isolate confirmed the strain to be methicillin-resistant Staphylococcus aureus (MRSA), with resistance to oxacillin, cefoxitin, and clindamycin. The minimum inhibitory concentrations (MICs) of the isolate for vancomycin and linezolid were 1 µg/mL and 2 µg/mL, respectively, indicating susceptibility to both antibiotics, as well as to tetracycline.

Chest computed tomography (CT) in the outpatient department on the day of admission (D0) revealed multiple nodular and patchy infiltrates with cavitary lesions in both lungs, consistent with hematogenous dissemination (Fig. 1).

Fig. 1.

Chest CT scan obtained prior to admission showing multiple nodular and patchy infiltrates with cavitary lesions in both lungs, consistent with hematogenous dissemination

On hospital day 1 (D1), plain radiographs of the left humerus demonstrated no obvious osseous abnormalities (Fig. 2A). In contrast, magnetic resonance imaging (MRI) performed on Day 2 demonstrated marked soft tissue swelling of the left upper arm and shoulder joint, bone marrow edema of the humerus, findings indicative of osteomyelitis with associated soft tissue infection (Fig. 2B).

Fig. 2.

(A) Plain radiographs of the left humerus obtained on the day of admission showing no obvious osseous abnormalities. (B) MRI of the left upper extremity on hospital day 3 showing marked soft tissue swelling and bone marrow edema of the humerus. (C) and (D) Chest CT prior to the first discharge, showing significant resolution of pulmonary abscesses. (E) The chest radiograph prior to the third surgery (autologous iliac bone grafting), showing no abnormalities and no new pulmonary lesions

After 10 days of inpatient antimicrobial therapy, follow-up blood cultures were negative. However, the swelling and pain in the patient’s left upper limb persisted, and surgical intervention was performed. Bacterial cultures were taken from the abscess drainage in the left upper limb during the first surgery. The results confirmed MRSA, and the antibiotic susceptibility was the same as before. During the subsequent course of treatment, serial laboratory evaluations showed a gradual normalization of leukocyte count, C-reactive protein, and procalcitonin levels, reflecting a favorable response to antimicrobial therapy. Follow-up blood cultures obtained during hospitalization yielded no growth. Regarding the patient’s pulmonary condition, chest CT prior to the first discharge showed significant resolution of the pulmonary abscesses (Fig. 2C and D). Prior to the third surgery (autologous iliac bone grafting), a follow-up chest radiograph showed no abnormalities, with no new pulmonary lesions observed (Fig. 2E).

Diagnosis and treatment

Initial empirical intravenous antibiotic therapy with vancomycin and cefoperazone–sulbactam was initiated on the day of the patient’s admission (D0). However, the patient’s symptoms persisted, and MRI findings prompted an orthopedic consultation. Despite conservative treatment recommended after an orthopedic consultation, the patient continued to experience swelling and pain in the left upper limb. Consequently, the patient was transferred to the orthopedic department for surgical management. During the first surgery (D11), significant soft tissue detachment was observed around the proximal humerus, along with inflammatory granulation tissue within the marrow cavity. Periosteal detachment was also identified. Bone trepanation and medullary lavage were performed to clear the infected bone marrow, remove inflammatory tissue, ensure adequate drainage, and facilitate local antibiotic penetration. Intraoperative bacterial cultures confirmed MRSA. Despite this procedure, the patient continued to experience fever, swelling, and pain in the left upper limb, which prompted a second surgical intervention on Day 31. After the second surgery, the patient’s condition improved, and he was discharged. Both surgeries involved fascial excision, debridement of infected soft tissue and bone, and implantation of antibiotic-loaded calcium sulfate beads (Fig. 3A). Vancomycin therapy was continued throughout the hospitalization. After 40 days of inpatient treatment, the patient was discharged in improved condition, with an additional 4-week course of oral linezolid. Renal function remained stable during vancomycin therapy, and platelet counts showed no evidence of bone marrow suppression while receiving linezolid.

Fig. 3.

(A) Postoperative day 2 following the first debridement, showing antibiotic-loaded calcium sulfate beads in place. (B) One month after the second debridement, plain radiograph revealing a proximal humerus fracture with malalignment. (C) Postoperative day 1 after open reduction, internal fixation, and autologous iliac crest bone grafting at age 14, showing internal plate fixation of the humerus. (D) Radiograph obtained two years later, showing removal of the internal fixation plate. (E) X-ray of the right humerus, taken concurrently with Fig. 3B, showing no signs of infection or bone involvement

One month after the second surgery (D67), the patient developed left upper arm pain after sleeping. X-ray confirmed a humeral shaft fracture, which was treated with splint fixation for approximately 19 months (Fig. 3B). Prior to the internal fixation surgery at age 14, the patient had persistent pain and restricted mobility in the left upper arm. The left elbow could be flexed, and the left shoulder could be elevated with assistance; however, abduction and extension remained partially limited. At age 14, delayed open reduction, internal fixation, and autologous iliac crest bone grafting were performed (Fig. 3C). Two years later, the internal fixation was removed, and the patient reported no significant pain, with mild discomfort at the implant site. The range of motion (ROM) of the left shoulder and elbow showed no significant limitations, and the patient regained full limb function (Fig. 3D). He is currently under ongoing follow-up. Although the patient had a furuncle on the right forearm, the infection was localized to the left side, and no osteomyelitis developed in the right arm. Figure 3E shows the X-ray of the right humerus taken simultaneously with Fig. 3B, demonstrating no signs of infection or bone involvement on the right side. A detailed timeline of the patient’s clinical course, including key events and surgeries, is presented in Fig. 4.

Fig. 4.

Clinical timeline of the patient’s disease progression and surgical interventions. The timeline begins with the onset of symptoms (D-7), followed by admission (D0). Key events during the hospital course include the first and second surgeries (D11 and D31), which involved debridement of left humeral osteomyelitis and soft tissue abscesses, along with antibiotic bead implantation. At D67, the patient developed left upper arm pain. X-ray confirmed a humeral shaft fracture, which was treated with splint fixation for nearly 19 months. The third surgery at age 14 (D608) involved open reduction, internal fixation, and autologous iliac bone grafting. The fourth surgery at D1319 (approximately 3.6 years after the first admission) involved the removal of the internal fixation

Discussion

This case report describes a previously healthy 12-year-old boy who developed severe, disseminated CA-MRSA infection following self-manipulation of a right forearm furuncle. The infection rapidly spread hematogenously, leading to bilateral pulmonary abscesses and proximal humeral osteomyelitis. Despite the initial absence of significant findings on plain radiographs, MRI revealed early signs of osteomyelitis, enabling timely diagnosis and intervention. This case underscores the rarity and severity of CA-MRSA infections in immunocompetent children, highlighting the potential for rapid dissemination and multi-organ involvement. Early recognition, comprehensive imaging, and a multidisciplinary approach involving pediatric infectious disease specialists, orthopedic surgeons, and radiologists were critical in ensuring a favorable outcome. The successful management of this patient emphasizes the importance of aggressive and coordinated care in cases of complex, multi-site pediatric infections.

Although Staphylococcus aureus remains the most common pathogen in pediatric osteoarticular infections, the involvement of disseminated CA-MRSA presenting simultaneously with pulmonary abscesses and osteomyelitis in an otherwise healthy child is uncommon [7]. Patients with CA-MRSA infections tend to be younger and are often otherwise healthy, without traditional healthcare-associated risk factors [8, 9]. The literature reports that invasive CA‑MRSA infections, including pneumonia, empyema or pulmonary abscess, have increased in children, and are more likely than CA-MSSA infections to involve multiple organ systems [10].

The pathogenesis of hematogenous dissemination involves metastatic seeding of distant organs following bacteremia [11, 12]. In pediatric acute hematogenous osteomyelitis (AHO), this is primarily due to transient bacteremia and the unique anatomical features of growing bones [13]. In our case, both lungs and bones were rapidly affected following bacteremia, reflecting their susceptibility as common metastatic sites. Certain CA-MRSA strains, particularly those producing Panton-Valentine leukocidin (PVL), enhance hematogenous spread by inducing leukocyte lysis and extensive tissue necrosis. PVL is a key virulence factor contributing to tissue destruction, abscess formation, and metastatic spread in severe pediatric infections [14–16]. In our case, the patient developed both pulmonary and bone involvement, followed by a pathological fracture, highlighting the aggressive nature of CA-MRSA in pediatric patients. This underscores the need for heightened clinical vigilance, even in otherwise healthy children, as seemingly mild skin infections can lead to rapid systemic deterioration. The furuncle likely served as the portal of entry, facilitating bloodstream dissemination and subsequent infection of the lungs and humerus.

Inadequate debridement during the initial surgery likely contributed to the patient’s pathological fracture. Although blood cultures were positive for MRSA on admission and became negative after 10 days of antimicrobial therapy, intraoperative cultures during the first surgery identified persistent MRSA in the local pus. In addition, the diagnostic delay—initial radiographs were unremarkable, and MRI was required—may have further increased the risk of complications. This delayed recognition of osteomyelitis, together with incomplete debridement exacerbated bone destruction and contributed to non-union. These findings highlight the need for timely and aggressive surgical intervention to prevent fractures and impaired healing in pediatric MRSA osteomyelitis.

This diagnostic delay can be partly explained by the limited sensitivity of radiographs in early AHO. According to the 2021 Clinical Practice Guideline by the Pediatric Infectious Diseases Society and the Infectious Diseases Society of America (IDSA), plain radiographs are recommended primarily to exclude alternative diagnoses but show low sensitivity (16–37%) for early AHO. By contrast, MRI offers markedly higher sensitivity (81–100%) and specificity (67–94%) [17], enabling detection of bone marrow edema within 1–2 days of symptom onset, whereas radiographic changes may not appear for 10–14 days [18]. In this case, early MRI allowed prompt identification of bone involvement despite negative radiographs, underscoring its crucial role in the evaluation of suspected AHO.

Empirical antimicrobial therapy remains the foundation of managing invasive CA-MRSA infections in children, with vancomycin recommended as first-line treatment for severe disease [17]. In this case, vancomycin combined with cefoperazone–sulbactam provided broad initial coverage, consistent with recommendations for suspected MRSA with possible Gram-negative co-infection [19]. Clinical improvement and normalization of inflammatory markers further supported the effectiveness of vancomycin. Transition to oral linezolid after discharge is supported by its high bioavailability and excellent bone penetration, making it a suitable step-down therapy for MRSA infections with a low risk of serious adverse events [20]. Close monitoring of renal and hematologic parameters is recommended when using vancomycin and linezolid, and recent pediatric data confirm their acceptable safety profiles with appropriate surveillance [21].

Surgical intervention is essential in the management of pediatric acute hematogenous osteomyelitis, particularly when complicated by soft-tissue abscesses or intramedullary involvement [22]. In this patient, two early surgeries were required due to persistent fever, progressive swelling, and a substantial soft-tissue abscess of the proximal upper arm confirmed intraoperatively. The procedures included fascial release, thorough debridement of the infected soft tissues and intramedullary granulation tissue, irrigation, and implantation of antibiotic-loaded calcium sulfate beads. Importantly, the markedly elevated CRP level at admission (196 mg/L) in this case aligns with recent evidence showing that high initial CRP is strongly associated with the need for surgical intervention in children with AHO, particularly in those with MRSA infection [23]. According to Guo et al., children who required multiple surgeries exhibited significantly higher CRP levels at admission compared with those undergoing a single procedure (154.1 vs. 50 mg/L, P < 0.001) [23].

Despite initial improvement, the child later developed a pathological fracture, most likely as a consequence of delayed diagnosis and insufficient removal of infected and necrotic tissue during the first operation. This progression aligns with recent evidence indicating that acute osteomyelitis can rapidly weaken bone structure through infection-mediated destruction, thereby predisposing children to pathological fractures even under minimal mechanical load. As reported by Zargarbashi et al., such infection-related architectural compromise often necessitates repeated surgical debridement to achieve adequate infection control and eventual bone union [24].

In this patient, although infection was eventually controlled through staged debridement and targeted antibiotic therapy, the proximal humerus progressed to nonunion due to early structural compromise. Following the development of nonunion, delayed open reduction, internal fixation, and autologous iliac crest bone grafting were performed at age 14. This timing was chosen because definitive reconstruction is recommended only after complete eradication of infection, as persistent inflammation markedly increases the risk of fixation failure and recurrent osteomyelitis [25]. In addition, performing reconstruction in early adolescence provides improved bone quality and biomechanical stability for internal fixation, thereby enhancing the likelihood of successful union [26]. Autologous iliac crest bone grafting is widely regarded as the gold standard biological option for restoring bone continuity and promoting healing in long-bone nonunion, including cases reconstructed after eradication of infection [27]. The iliac crest is the most commonly used donor site because it provides osteoconductive, osteoinductive, and osteogenic properties with proven consolidation potential [28]. The patient ultimately achieved successful union, demonstrating that a staged surgical approach—beginning with early infection control, followed by delayed biological and mechanical reconstruction—is essential for managing complex pediatric CA-MRSA osteomyelitis.

This report has several limitations. PVL genotyping was not performed, limiting the microbiological characterization of the Staphylococcus aureus isolate. Additionally, vancomycin serum levels were not monitored, limiting pharmacokinetic optimization and precise therapeutic dosing assessment [29]. Lastly, as a single case, the generalizability of this management approach is limited, and further validation through multi-center studies is needed.

Conclusion

This case highlights that early diagnosis, prompt imaging, timely and adequate surgical intervention, local antibiotic therapy, and continuous multidisciplinary management can lead to favorable outcomes in children with disseminated CA-MRSA infections. Establishing standardized protocols for managing complex pediatric CA-MRSA cases could further improve outcomes and minimize complications.

Abbreviations

MRSA

Methicillin-resistant Staphylococcus aureus

CA-MRSA

Community-acquired Methicillin-resistant Staphylococcus aureus

PVL

Panton–Valentine leukocidin

SSTIs

Skin and soft tissue infections

CT

Computed tomography

MRI

Magnetic resonance imaging

WBC

White blood cell

CRP

C-reactive protein

PCT

Procalcitonin

Author contributions

GQ designed and conceived the study; LM wrote the manuscript; ZL performed the data curation and analysis; QZ, YZ, JN and XR revised and edited the manuscript critically; All authors read and approved the final manuscript.

Funding

No external funding was received for the analysis or drafting of this study.

Data availability

The data supporting this case report were extracted from the electronic medical records at the Affiliated Hospital of Jining Medical University, Jining, Shandong, China. To ensure patient privacy and anonymity, a direct link to these records is not provided. The corresponding author can make the data available upon reasonable request.

Declarations

Ethical approval and consent to participate

This is an observational description of a clinical case. No ethical approval was needed.

Consent for publication

Written informed consent was obtained from both the patient’s parents and the patient himself.

Competing interests

The authors declare no competing interests.