Rapid in vivo development of resistance to daptomycin in vancomycin-resistant Enterococcus faecium due to genomic alterations

Daptomycin is a cyclic lipopeptide used in the treatment of vancomycin-resistant Enterococcus faecium (VREfm). However, the development of daptomycin-resistant VREfm challenges the treatment of nosocomial VREfm infections. Resistance mechanisms of daptomycin are not fully understood. Here we analysed the genomic changes leading to a daptomycin-susceptible VREfm isolate becoming resistant after 50 days of daptomycin and linezolid combination therapy. Seven isogenic VREfm isolates from the same patient (daptomycin-susceptible and daptomycin-resistant) were analysed using Illumina whole genome sequencing, and two isolates were further characterised with Nanopore sequencing. One nonsynonymous SNP in the rpoC gene previously shown to harbour mutations in daptomycin-resistant VREfm was identified in the daptomycin-resistant isolates. Whole genome comparative analysis identified the loss of a 46.5 kb fragment, duplication of a 29.7 kb fragment, and integration of two plasmids upon acquisition of daptomycin resistance. Transmission electron microscopy showed similar alterations in cell morphology and cell wall structure as have previously been described in daptomycin-resistant Enterococcus faecalis.

Antibiotic exposure in infancy and development of BMI and body composition in childhood

BACKGROUND

It has been hypothesized that antibiotic usage in early life could contribute to development of overweight in childhood. Studies have seen association between antibiotic usage and overweight in childhood. We aimed to investigate the relationship between antibiotic exposure in infancy and development of body mass index (BMI) and body composition.

METHODS

A prospective mother-child cohort study of 738 pregnant women and their 700 children, Copenhagen Prospective Studies on Asthma in Childhood₂₀₁₀ (COPSAC₂₀₁₀). Information on antibiotic exposure was collected by interviews. Height/length and weight measures were collected at age 1, 2, 3, 4, 5 and 6 years and body composition was determined by a dual-energy X-ray absorptiometry (DXA) scan at age 3.5 and 6 years.

FINDINGS

306 (46%) of the 661 children were exposed to antibiotics before 1 year of age. There were no differences in BMI z-score development at age 1-6 years between children exposed to antibiotics compared to unexposed: z-score difference, -0.06 (95%CI: -0.17;0.06), p = 0.33, and no sex-differences (p-interaction = 0.48). Children exposed vs. not exposed to antibiotics had comparable fat percentage at 6 years of age: log(mean difference), 0.60% (95%CI: -0.212 to 1.41), p = 0.15.

INTERPRETATION

Children exposed to antibiotics had similar BMI, BMI z-score and body composition between 1 and 6 years of life compared to unexposed children. Our study does not support the hypothesis that antibiotic exposure in infancy leads to development of obesity in the first 6 years of life.

FUNDING

The Lundbeck Foundation, The Ministry of Health, Danish Council for Strategic Research and The Capital Region Research Foundation.

[Mycoplasma pneumoniae-associated mucositis in a 17-year-old girl]

Stevens-Johnson syndrome is an autoimmune condition characterised by erythematous target lesions on the skin with involvement of the oral and genital mucosa and conjunctivae. Recent case reports describe incomplete presentations with absence of the characteristic skin changes. This is caused by extrapulmonary manifestations of Mycoplasma pneumoniae lung infection and is now recognised as M. pneumoniae-associated mucositis (MPAM). This case report describes the clinical presentation of MPAM in a 17-year-old girl and highlights the importance of the recognition and the appropriate clinical management.

Cesarean Delivery and Body Mass Index at 6 Months and Into Childhood

BACKGROUND AND OBJECTIVES

The prevalence of cesarean delivery (CD) is rising worldwide, and so is childhood obesity. Studies have shown associations between these factors. We examined the development of BMI from birth through childhood to determine whether CDs were associated with differences in growth and obesity.

METHODS

Term children from the birth cohorts Copenhagen Prospective Studies on Asthma in Childhood₂₀₀₀ (COPSAC₂₀₀₀) and COPSAC₂₀₁₀ were included. Height, length, and weight measurements were collected prospectively until 5 years in COPSAC₂₀₁₀ and until 13 years in COPSAC₂₀₀₀. Dual-energy x-ray absorptiometry (DXA) scans were performed at 3.5 and 7 years. Information on relevant covariates were verified during clinical visits. Analyses were adjusted for covariates associating with CD.

RESULTS

In COPSAC₂₀₁₀, 20% (N = 138/673) of the children were delivered by CD; 49% were girls. In COPSAC₂₀₀₀, 19% (N = 76/393) were delivered by CD; 51% were girls. Children delivered by CD had a higher mean BMI at 6 months compared with those delivered vaginally: COPSAC₂₀₁₀ β-coefficient, .41 (95% confidence interval [CI], .12 to .69), P = .01; COPSAC₂₀₀₀ β-coefficient, .16 (95% CI, -.11 to .68), P = .16; and meta-analysis β-coefficient, .37 (95% CI, .14 to .60), P = .002. There were no differences in BMI trajectory between the 2 groups by 5 and 13 years, nor cross-sectional BMI at 5 and 13 years, nor in fat percentages from DXA scans.

CONCLUSIONS

Children delivered by CD had a higher BMI at 6 months of age, but this difference did not track into later childhood. Our study does not support the hypothesis that CD leads to later overweight.

Germline heterozygous variants in genes associated with familial hemophagocytic lymphohistiocytosis as a cause of increased bleeding

Familial hemophagocytic lymphohistiocytosis (FHL) is caused by biallelic variants in genes regulating granule secretion in cytotoxic lymphocytes. In FHL3-5, the affected genes UNC13D, STX11 and STXBP2 have further been shown to regulate the secretion of platelet granules, giving rise to compromised platelet function. Therefore, we aimed to investigate platelet degranulation in patients heterozygous for variants in UNC13D, STX11 and STXBP2. During the work-up of patients referred to the Coagulation Unit, Skåne University Hospital, Malmö, Sweden and the Department of Hematology, Rigshospitalet, Copenhagen, Denmark due to bleeding tendencies, 12 patients harboring heterozygous variants in UNC13D, STX11 or STXBP2 were identified using targeted whole exome sequencing. Transmission electron microscopy (TEM) was used to assess the secretion of platelet dense granules following thrombin stimulation. Platelet degranulation, activation and aggregation were further assessed by flow cytometry (FC) and light transmission aggregometry (LTA) with lumi-aggregometry. In total, eight out of twelve (67%) patients showed impaired degranulation by at least one of the assays (TEM, FC and LTA). In the 12 patients, eight different heterozygous variants were identified. One variant was strongly associated with impaired degranulation, while four of the variants were associated with impaired granule secretion to a slightly lesser extent. One additional variant was found in six out of the twelve patients, and was associated with varying degrees of degranulation impairment. Accordingly, six out of the eight (75%) identified variants were associated with impaired platelet degranulation. Our results suggest that heterozygous variants in UNC13D, STX11 and STXBP2 are sufficient to cause platelet secretion defects resulting in increased bleeding.