Enterococci are Gram-positive commensals of the mammalian intestinal tract and harbor intrinsic resistance to broad-spectrum cephalosporins. Disruption of colonization resistance in humans by antibiotics allows enterococci to proliferate in the gut and cause disseminated infections. In this study, we used (EF)-colonized mice to study the dynamics of enterococci, commensal microbiota, and the host in response to systemic ceftriaxone administration. We found that the mouse model recapitulates intestinal proliferation and dissemination of enterococci seen in humans. Employing a ceftriaxone-sensitive strain of enterococci ( JL308), we showed that increased intestinal abundance is critical for the systemic dissemination of enterococci. Investigation of the impact of ceftriaxone on the mucosal barrier defenses and integrity suggested that translocation of enterococci across the intestinal mucosa was not associated with intestinal pathology or increased permeability. Ceftriaxone-induced alteration of intestinal microbial composition was associated with transient increase in the abundance of multiple bacterial operational taxonomic units (OTUs) in addition to enterococci, for example, lactobacilli, which also disseminated to the extraintestinal organs. Collectively, these results emphasize that ceftriaxone-induced disruption of colonization resistance and alteration of mucosal homeostasis facilitate increased intestinal abundance of a limited number of commensals along with enterococci, allowing their translocation and systemic dissemination in a healthy host.

Linear IgA bullous dermatosis (LABD) is an autoimmune vesiculobullous disease, which is typically idiopathic but can also rarely be caused by medications or infections. Vancomycin is the most common drug associated with LABD. Lesions typically appear 24 hours to 15 days after the first dose of vancomycin. It is best characterized pathologically by subepidermal bulla (blister) formation with linear IgA deposition at the dermoepidermal junction. Here we report an 86-year-old male with a history of left knee osteoarthritis who underwent a left knee arthroplasty and subsequently developed a prosthetic joint infection. This infection was treated with intravenous vancomycin as well as placement of a vancomycin impregnated joint spacer. Five days following initiation of antibiotic therapy, he presented with a vesiculobullous eruption on an erythematous base over his trunk, extremities, and oral mucosa. The eruption resolved completely when intravenous vancomycin was discontinued and colchicine treatment was begun. Curiously, complete resolution occurred despite the presence of the vancomycin containing joint spacer. The diagnosis of vancomycin-induced linear IgA bullous dermatosis was made based on characteristic clinical and histopathologic presentations.

Chronic lymphocytic leukemia (CLL) is a disorder of B cells that affects humoral as well as cell-mediated immunity. Protection against cryptococcal infections is mounted by an intricate and synchronized interplay of both integral arms of immunity. Whether CLL or small molecule tyrosine kinase inhibitors are independently predisposing hosts to cryptococcal infections remain to be explored. Herein, we present a report of a patient who developed disseminated cryptococcosis while receiving ibrutinib therapy for CLL in the salvage setting. We further present relevant literature available thus far on the topic and discuss immunologic mechanisms that may be involved in the fungal pathogenesis in such patients.

Drug induced aseptic meningitis is a rare but challenging diagnosis, most commonly reported with nonsteroidal anti-inflammatory drugs and antibiotics. Trimethoprim/sulfamethoxazole is a sulfonamide that is widely used in clinical practice for the treatment and prophylaxis of various infections. Drug induced aseptic meningitis, when seen with trimethoprim/sulfamethoxazole, occurs predominantly in patients with some degree of immune compromise and is less commonly seen in immune competent individuals. The patient often exhibits the classic symptoms of meningitis. Early diagnosis is important, since the cessation of the antibiotic leads to rapid clinical improvement. Trimethoprim/sulfamethoxazole induced aseptic meningitis has been underreported to FDA/MED-WATCH program. Here we report two cases of trimethoprim/sulfamethoxazole: an immune competent individual and immune compromised individual, both of which presented with signs of meningitis and a negative infectious workup. Trimethoprim/sulfamethoxazole is an uncommon and mysterious adverse reaction to a commonly used antibiotic. It should be considered in the differential diagnosis of patients presenting with acute signs and symptoms of meningitis especially after infectious causes have been ruled out.

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