An 11-year-old female student, with no history of hospitalizations or chronic diseases, had received flucloxacillin one month prior to hospitalization as treatment for an impetus.
His mother had systemic lupus erythematosus, housewife and his father, who worked in international mail services.
The patient suffered a fall, so she consulted in the Emergency Unit (EU) for pain in the right knee.
A contusion was diagnosed and managed on an outpatient basis with immobilization and analgesia.
Given the persistence of pain, the patient returns to the doctor a week later.
Physical examination revealed severe pain in the right knee, spontaneous pain associated with proximal metaphysis of the right tibia, with increased volume and local temperature, with no fever, no hemodynamic compromise, or general condition.
On admission, a complete blood count with leukocytosis and left shift (24% bacilliform), C-reactive protein (CRP) 270 mg/L and ESR 101 mm/h stood out.
The X-ray showed a slight increase in soft tissues in the right knee, with no associated bone lesion.
Surgical debridement was performed and antimicrobial treatment was initiated with intravenous cloxacillin (185 mg/kg/day) every 6 h.
On the third postoperative day, he persisted with severe pain and began with fever and general malaise.
Both hemocultives and bone tissue culture were positive for MRSA, so vancomycin was initiated, contact isolation according to institutional standards and a new surgical procedure was performed.
Given the persistence of fever, a three-phase scintigram was performed, which showed an increase in bone voiding activity located in the metaphysis of the right proximal tibia.
The evolution was torpid, with fever up to 15 days after starting vancomycin, requiring multiple infections in which persistence and articular damage were found.
Intraoperative cultures were positive until 12 days after initiating vancomycin.
Due to the persistence of fever secondary foci or other infection were ruled out.
A basic immunological study was carried out which was normal.
On day 18 of treatment with vancomycin, she developed a maculopapular morbilliform rash, which was considered an adverse drug reaction, so the therapy was switched to clindamycin IV.
The patient was treated conservatively and without local pain, totaling 56 days of antibacterial treatment: 17 days of vancomycin and 39 days of clindamycin.
She was discharged with decreasing inflammatory parameters (HSV 28 mm/h and CRP 19.2 mg/L), and treatment with oral linezolid (300 mg twice a day) for 20 days.
The PSI confirmed that the strain was MRSA, PVL negative.
In addition, a study of familial nasal carriage was conducted in which the mother was found to be positive and decolonization with topical mupirocin was performed.
Genetic analysis and molecular characterization of both strains showed the absence of PV-L marker and determined the same genetic subtype by PFGE (CL-SAU-COM-SMA-017) and MLST to the type of sequence ST8.
