The impact of an infectious diseases consultation on antimicrobial prescribing.

Hagerstown, MD XXX The Impact of an Infectious Diseases Consultation on Antimicrobial Prescribing for severe mastitis and breast abscess. The infant was started on clindamycin and gentamicin. She became febrile to 100.5°F and was transferred to our institution for further evaluation and management. On examination, the child was afebrile and nontoxic appearing. She was tachypneic but comfortable with no signs of respiratory distress. A 4 cm × 2 cm firm, nonmobile mass overlying the right lateral 9th and 10th ribs extending to the back was noted. The mass appeared to be tender to palpation but had no associated erythema or crepitus. Notably, auscultation of the lungs revealed decreased breath sounds over the right middle and lower lobes. Laboratory data at the time of transfer revealed a white blood cell count of 27,310/μL with 39% segmented neutrophils and 9% bands. Platelets were elevated at 770,000/μL. Chest radiograph demonstrated a right lower lobe chest mass with associated medial right 10th rib destruction. A noncontrast chest computed tomography showed a large loculated fluid density in the right hemithorax abutting and inseparable from the pleura, with adjacent osteolytic changes in the posterior right 10th rib and soft tissue thickening of the posterior chest wall. The neonate was admitted for further management and started on empiric antimicrobial therapy with clindamycin, gentamicin and ampicillin. Gentamicin was discontinued in the first 12 hours of admission in favor of cefotaxime. A contrast computed tomography of the chest mass was performed in consideration of potential surgical intervention. This study demonstrated a large, peripherally enhancing fluid collection centered within the right hemithorax consistent with empyema necessitatis. Extension and abscess formation in the posterolateral right chest wall was seen accompanied by osseous involvement of the posterolateral right 9th, 10th and 11th ribs. The patient underwent fluoroscopy-guided percutaneous drainage with pigtail catheter placement, resulting in the removal of 20 mL of purulent fluid. Gram stain of the fluid demonstrated many white blood cells and many Gram-positive cocci in clusters, and cultures grew MRSA. At that time, it was relayed to the medical team that the patient’s mother had undergone incision and drainage of a breast abscess at the outlying hospital with cultures also demonstrating MRSA. Ampicillin and cefotaxime were discontinued, and clindamycin was continued pending susceptibility testing. Culture results confirmed clindamycin-susceptible MRSA. The infant remained stable in the postoperative period. A repeat chest radiograph on the day of catheter removal revealed considerable improvement in aeration of the right lung. After receiving a total of 4 weeks of intravenous clindamycin, the patient was discharged home on oral clindamycin to complete an additional 4 weeks of therapy. DNA fragment analysis via pulsed-field gel electrophoresis was performed on both the mother’s and the patient’s isolates. The strain was confirmed as USA300, and the isolates from mother and infant were identical by this analysis. Telephone follow up with the family after treatment completion revealed that the patient was growing well and thriving, without any untoward side effects from prolonged antimicrobial therapy. Despite the relatively widespread incidence of invasive infection secondary to CA-MRSA, there are only 3 reported cases of CA-MRSA associated empyema necessitatis documented in the pediatric literature and none involving neonates. None of these prior cases identified breast-feeding or maternal breast abscess as potential routes of acquisition. The diagnosis of empyema necessitatis requires tomographic imaging to visualize the pathognomonic changes of a pleural effusion connected to the chest wall mass. Treatment of this condition requires a combination of antimicrobial therapy targeted at the most likely causative agent(s) in conjunction with prompt surgical drainage. The optimal duration of antibiotic therapy for empyema necessitatis and associated osteomyelitis in a patient who has undergone surgical drainage is not established. We recommended a total of 8 weeks therapy given the age of the patient and the invasive nature of the infection, including contiguous osteomyelitis.