Our patient, a 28-day-old boy, was referred to the Department of Pediatrics of our hospital with the diagnosis of right-sided orbital cellulitis on April 28, 2010. His symptoms, including anorexia, rhinorrhoea, and right eye redness had begun five days before admission.
The newborn was full-term and had been delivered vaginally. Birth weight was 4,900 g and he was on combined breast and formula feeding pattern.
On admission, the patient's temperature was 37.7°C, heart rate was 132 beats/min, and physical examination revealed no other pathological findings except right eye proptosis, conjunctival injection and periorbital erythema. The infant did not have evidence of pneumonia on chest radiograph.
White blood cell count was 19,000 cells/mm3 with differential of neutrophils 49%, lymphocytes 24%, monocytes 11%, activated lymphocytes 10%, myelocytes 1% and eosinophils 5%. Platelet count was 373,000/mm3. Blood, urine, and cerebrospinal fluid (CSF) samples were cultured and proved sterile. The examination of CSF showed 300 RBC/mm3, 2 WBC/mm3, glucose 3.88 mmol/L with concomitant blood glucose 6.55 mmol/L, protein 0.52 g/L and LDH 24 IU/L. Erythrocyte sedimentation rate (ESR) was 91 mm/h and C-reactive protein (CRP) was 120 mg/L.
Ophthalmic examination revealed right eye proptosis, periocular redness and edema and conjunctival discharge. Ocular motility was severely impaired. Pupils were equal, round, normally reactive to light. Slit-lamp anterior segment examination and dilated fundus examination were within normal limits.
Brain MRI was normal and orbital MRI at 3.0T showed ethmoid opacification and a right eye proptosis due to an intra-orbital lesion, located in the retrobulbar fatty tissue between the medial, lateral, inferior rectus muscles and the wall of the globe. The lesion, containing multiple cystic regions, was consistent with orbital cellulitis with abscess formation (Figure1).
Empirical therapy of intravenous daptomycin 12 mg/kg qd, rifampin 20 mg/kg qd and ceftriaxone 100 mg/kg qd was initiated. On the fifth day of treatment, as the abscess had expanded to the preseptal area and the right eye proptosis continued with tension and edema of the lower eyelid, surgical drainage was performed through the inner area of the lower fornix. The culture of pus yielded a low colony count of MRSA. Polymerase chain reaction was performed in order to test the isolate for genes encoding the Panton-Valentine leukocidine (PVL) production (luk-S-PV and luk-F-PV) as previously described [2]. In addition, the S. aureus strain was studied by multilocus sequence typing. The molecular analysis of the isolate revealed that it was a PVL-positive ST80 S. aureus strain. The isolate was resistant to oxacillin, tetracycline and fucidic acid and susceptible to erythromycin, trimethoprim/sulfamethoxazole, vancomycin, linezolid, daptomycin, rifampin and moxifloxacin. The MIC to daptomycin was determined by the E-test method (AB Biodisk, Solna, Sweden) and was found to be 0.19 mg/L.
The infant remained afebrile. Further drainage of a small quantity of pus from the previously incised area was performed on the sixth day of treatment. Orbital MRI was performed the following day, revealing reduction of the abscess cavity volume, particularly at the posterolateral aspect of the orbit.
ESR was 40 mm/h and CRP was 3 mg/L on the eighth day of treatment and on the 15th day, ESR was 21 mm/h and CRP decreased to 0.1 mg/L.
During the following weeks, his ophthalmic findings were gradually improved without requirement for further surgery. The edema of the lower eyelid subsided fully during the fourth week of treatment. A repeat MRI was performed after 4 weeks of antimicrobial therapy, in which residual inflammatory findings were observed in the inferolateral structures of the orbit.
The combination antimicrobial therapy was administered for 42 days and successfully controlled the infection. The patient tolerated well the 6-week daptomycin therapy. The infant had normal creatinine and blood urea nitrogen values. No increase in serum creatine phosphokinase (CPK) levels was noted. CPK level was measured at least once per week and it ranged from 31 to 113 IU/L (median value 87 IU/L). A follow-up evaluation was performed 4 weeks after the completion of antimicrobial therapy and both the clinical examination and MRI findings were normal without residual ophthalmic disease. Since then, no relapse or long-term ophthalmic sequelae have been observed.
Maternal medical history and the thorough clinical investigation failed to reveal obvious predisposing factors of CA-MRSA acquisition or the site of entrance.
