Impact of Antibiotic Treatment on the Gut Microbiome and its Resistome in Hematopoietic Stem Cell Transplant Recipients.

Antibiotic-resistant bacterial infections are increasingly an issue in allogenic hematopoietic stem cell transplant patients. How antibiotic treatment impacts antibiotic resistance in the human gut microbiome remains poorly understood in vivo. Here, a total of 577 fecal samples from 233 heavily antibiotic-treated transplant patients were examined using high-resolution prescription data and shotgun metagenomics. The 13 most frequently used antibiotics were significantly associated with 154 (40% of tested associations) microbiome features. Use of broad-spectrum ß-lactam antibiotics was most markedly associated with microbial disruption and increase in resistome features. The enterococcal vanA gene was positively associated with 8 of the 13 antibiotics, and in particular piperacillin/tazobactam and vancomycin. Here, we highlight the need for a high-resolution approach in understanding the development of antibiotic resistance in the gut microbiome. Our findings can be used to inform antibiotic stewardship and combat the increasing threat of antibiotic resistance.

HIV-1 Drug Resistance by Ultra-Deep Sequencing Following Short Course Zidovudine, Single-Dose Nevirapine, and Single-Dose Tenofovir with Emtricitabine for Prevention of Mother-to-Child Transmission.

Antiretroviral drug resistance following pMTCT strategies remains a significant problem. With rapid advancements in next generation sequencing technologies, there is more focus on HIV drug-resistant variants of low frequency, or the so-called minority variants. In South Africa, AZT monotherapy for pMTCT, similar to World Health Organization option A, has been used since 2008. In 2010, a single dose of co-formulated TDF/FTC was included in the strategy for prevention of resistance conferred by single-dose nevirapine (sd NVP). The study was conducted in KwaZulu-Natal, South Africa, among pMTCT participants who received AZT monotherapy from 14 weeks of gestation, intrapartum AZT and sd NVP, and postpartum sd TDF/FTC. Twenty-six specimens collected at 6 weeks post-delivery were successfully sequenced using 454 ultra-deep sequencing. Non-nucleoside reverse transcriptase inhibitor (NNRTI) resistance was detected in 17 of 26 (65%) patients, 2 (7%) had Thymidine analogue mutations, and 3 (11%) had K65R. Of the 17 patients with NNRTI resistance, 11 (65%) had high-level NNRTI resistance, whereas 6 (35%) had intermediate NNRTI resistance. The levels of NNRTI resistance are much higher than would be expected, given the inclusion of antepartum AZT and postpartum TDF/FTC. This high level of NNRTI resistance could impact future NNRTI-containing treatment for a large proportion of pMTCT-exposed women. The detection of Thymidine analogue mutations highlights the need to understand the clinical impact of these on AZT-containing antiretroviral treatment in women exposed to AZT monotherapy.

Plasma HIV-1 tropism and risk of short-term clinical progression to AIDS or death.

INTRODUCTION: It is uncertain if plasma HIV-1 tropism is an independent predictor of short-term risk of clinical progression / death, in addition to the CD4 count and HIV RNA level. We conducted a nested case-control study within EuroSIDA to assess this question amongst people with current HIV RNA level >1000 copies/mL, including both people on ART and those ART naïve. METHODS: People with an AIDS diagnosis or who died from any causes for whom there was a stored plasma sample with HIV-1 RNA (VL)≥1,000 copies/mL available in the time window of 3-12 months prior to the event were identified. At least one control was selected for each case matched for age, VL and HCV status at the time of sampling. Controls were event-free after a matched duration of time from the date of sampling. Plasma HIV tropism was estimated using 454 and population sequencing (PS). Non-R5 HIV was defined as: (a) ≥2% of sequences with a Geno2Pheno (G2P) FPR≤3.75% by 454, and (b) a G2P FPR≤10% by PS. We also compared CD4 slopes over the 12 months following the date of sampling using a linear mixed model with random intercept according to HIV tropism and ART status. RESULTS: The study included 266 subjects, 100 cases and 166 controls, with sample taken on average in 2006; 23% and 24% had non-R5 HIV by 454 and PS respectively. There were 19% women, 25% MSM, 92% Caucasians, 22% HCV+. At the time of sampling, 26% were ART-naïve, 25% had started but were off ART and 49% were receiving ART. The median age, CD4 and viral load was 41 years, 350 cells/mm(3) and 4.81 log c/mL, respectively. Baseline characteristics were well balanced by tropism. Factors independently associated with clinical progression or death were female gender (OR=2.12; 95% CI=1.04, 4.36; p=0.038), CD4+ count (OR=0.90 per 100 cells/mm(3) higher; 95% CI 0.80, 1.00; p=0.058), being on ART (OR=2.72; 95% CI 1.15, 6.41; p=0.022) and calendar year of sample (OR=0.84 per more recent year; 95% CI=0.77, 0.91; p<0.001). Baseline plasma tropism was not an independent risk factor for clinical progression or death by either 454 or PS. No significant interaction was observed between tropism and ART status. There were no significant differences in the CD4+ slope within or between tropism groups. CONCLUSIONS: Plasma HIV-1 tropism does not appear to add to the ability of CD4 count and viral load to predict the short term risk of AIDS and death outcomes, even with 454 sequencing.