Vancomycin-resistant Enterococcus faecium strains (VREfm) are critical public health concerns because they are among the leading causes of hospital-acquired bloodstream infections. Chlorhexidine (CHX) is a bisbiguanide cationic antiseptic that is routinely used for patient bathing and other infection control practices. VREfm are likely frequently exposed to CHX; however, the long-term effects of CHX exposure have not been studied in enterococci. In this study, we serially exposed VREfm to increasing concentrations of CHX for a period of 21 days in two independent experimental evolution trials. Reduced CHX susceptibility emerged (4-fold shift in CHX MIC). Subpopulations with reduced daptomycin (DAP) susceptibility were detected, which were further analyzed by genome sequencing and lipidomic analysis. Across the trials, we identified adaptive changes in genes with predicted or experimentally confirmed roles in chlorhexidine susceptibility (efrE), global nutritional stress response (relA), nucleotide metabolism (cmk), phosphate acquisition (phoU), and glycolipid biosynthesis (bgsB), among others. Moreover, significant alterations in membrane phospholipids were identified for some populations with reduced DAP susceptibility. Our results are clinically significant because they identify a link between serial subinhibitory CHX exposure and reduced DAP susceptibility. In addition, the CHX-induced genetic and lipidomic changes described in this study offer new insights into the mechanisms underlying the emergence of antibiotic resistance in VREfm.

No abstract

Vancomycin-resistant Enterococcus faecium (VREfm) are critical public health concerns because they are among the leading causes of hospital-acquired bloodstream infections. Chlorhexidine (CHX) is a bisbiguanide cationic antiseptic that is routinely used for patient bathing and other infection control practices. VREfm are likely frequently exposed to CHX; however, the long-term effects of CHX exposure have not been studied in enterococci. In this study, we serially exposed VREfm to increasing concentrations of CHX for a period of 21 days in two independent experimental evolution trials. Reduced CHX susceptibility emerged (4-fold shift in CHX MIC). Sub-populations with reduced daptomycin (DAP) susceptibility were detected, which were further analyzed by genome sequencing and lipidomic analysis. Across the trials, we identified adaptive changes in genes with predicted or experimentally confirmed roles in chlorhexidine susceptibility (efrE), global nutritional stress response (relA), nucleotide metabolism (cmk), phosphate acquisition (phoU), and glycolipid biosynthesis (bgsB), among others. Moreover, significant alterations in membrane phospholipids were identified. Our results are clinically significant because they identify a link between serial sub-inhibitory CHX exposure and reduced DAP susceptibility. In addition, the CHX-induced genetic and lipidomic changes described in this study offer new insights into the mechanisms underlying the emergence of antibiotic resistance in VREfm.

No abstract

Injury to the hypothalamus and both the anterior and posterior components of the pituitary gland is rare, but can result from infiltrative processes such as sarcoidosis, Langerhans cell histiocytosis, granulomatous with polyangiitis, and lymphocytic hypophysitis. Meningitis, pituitary infection, traumatic brain injury, and surgical instrumentation are other etiologies. A 40 year old man with mild cognitive impairment due to remote meningitis was evaluated for progressive somnolence. He was obtunded and cerebrospinal fluid (CSF) analysis revealed 11 WBC with lymphocytic pleocytosis (90% lymphocytes), highly elevated protein of 588 mg/dL (ref range 12-60 mg/dL), and low glucose of 17 mg/dL (ref range 40-70 mg/dL). MRI Brain revealed basilar meningitis/rhombencephalitis and suspected infectious vasculitis induced right middle cerebral artery territory stroke. Of note, there was substantial T2 hyperintense signaling in the hypothalamus and pituitary areas, which has been reported with tuberculosis (TB), Coccidioidomycosis (Cocci), and the aforementioned etiologies. He received broad antimicrobials, including TB treatment and fluconazole. He developed sinus bradycardia, hypotension, hypoglycemia, and hypothermia. Labs demonstrated inappropriately normal TSH of 1.4 mclU/mL (ref range 0.35-4.94 mclU/mL), low free T4 (fT4) of 0.50 ng/dL (ref range 0.7-1.48 ng/dL) with repeat fT4 undetectably low the following day, and AM cortisol less than 0.5mcg/dL (ref range 4-22 mcg/dL). Levothyroxine and steroids were initiated. He then developed central diabetes insipidus (DI) for which DDAVP was initiated. Comprehensive infectious and autoimmune meningoencephalitis workup was unrevealing. Serum and CSF tests for Listeria PCR, Cocci antibody and antigen, and TB were negative upon multiple, serial checks spanning weeks. CSF analysis one month later showed improvement in protein level (106 mg/dL), but still with elevated WBC (10 WBCs, 98% lymphocytes). MRI one month later demonstrated improvement in edema and the areas of ischemia and vasculitis were less. His adrenal insufficiency and central DI were transient and improved, no longer requiring steroids or DDAVP. He remains on levothyroxine for central hypothyroidism. The MRI and CSF findings point to an infectious etiology for hypopituitarism and central DI. We suspect an indolent bacteria such as Listeria or a fungus, likely Cocci, or TB meningitis. Cocci seemed to provide a unifying explanation as it classically creates infarcts and causes vasculitis. However, serial CSF tests were negative for Cocci, as well as for TB and Listeria. Marked improvement on follow up MRI also makes TB meningitis less likely as imaging would not resolve so quickly. This is a mysterious case; he improved on broad antimicrobial therapy and is being monitored closely in the outpatient setting.