New research was presented at ASM Microbe 2018, the combined meeting of the American Society for Microbiology annual meeting and the Interscience Conference on Antimicrobial Agents and Chemotherapy, from June 7-11 in Atlanta. The features below highlight some of the studies that emerged from the conference.
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Platelet Reactivity in PLWHIV
Prior research suggests that platelet function may be altered among people living with HIV (PLWHIV) on various antiretroviral therapy (ART) regimens. It remains unclear whether these alteration are due to chronic HIV infection or ART. For a study, researchers compared P2Y12 receptor-mediated platelet reactivity (PR) among PLWHIV on or off ART with that of participants without HIV. Groups were matched for baseline demographic and laboratory data know to affect PR. PR was significantly increase in PLWHIV when compared with those without the infection. Among PLWHIV, no significant differences in PR were observed between those receiving three different ART regimens or no therapy at all; the study authors conclude that this findings suggests that increased PR in PLWHIV may be driven by chronic HIV infection and not ART.
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Gut Microbiota in HEU Infants
Evidence suggests that use of PrEP to prevent mother-to-child HIV transmission has drastically reduced the rates of infected infants, resulting in increased rates of HIV-exposed by uninfected (HEU) children. While studies have shown that this population is at risk for early-life developmental abnormalities, few have assessed the impact of maternal HIV infection on the gut microbiome of HEU infants. For a study, microbiota from vaginal, stool, skin, and breastmilk samples collected from HIV-infected and -uninfected mothers and meconium, stool, and oral swabs collected from their infants were characterized. While the microbial communities identified in mothers were consistent, independent of HIV infection, differences were observed between those of HEU infants and children born to uninfected mothers (HUU). Shannon diversity index scores were significantly greater in HEU infants compared with HUU infants, and weight-for-age z scores were significantly lower in HEU infants. HUU infants had more abundant populations of Bifidobacteriaceae and Enterococcaceae, whereas HEU infants had more Ruminococcaceae, Pseudomonadaceae, and Enterobacteriaceae in their stools. The bacterial community composition of infants’ meconium and stool changed over time and was correlated with mothers’ HIV status. The study authors suggest their findings may help lead to drug-mediated and probiotic interventions in promoting the health of HEU infants.
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Antibiotic-Resistance Genes in Widely Used Biopesticide
Although considered to be safe for human consumption, Bacillus thuringiensis—a biopesticide used extensively in large-scale agriculture—has been shown to be a carrier of multiple plasmids and has demonstrated antibiotic resistance. Whether the commonly occurring soil bacteria is contributing to the spread of antibiotic-resistant genes (ARG) in the environment is not well established. For a study, researchers used bioinformatic analyses to determine if ARG are present in published B. thuringiensis genomes. After removing duplicates, the study team identified 295 occurrences of 15 unique genes encoding antibiotic resistance. Chromosomally encoded ARG accounted for 287 sequences, with all genomes containing a core set of three ARG, consisting of two genes encoding beta-lactamases (BLA1 and BLA2) and one encoding fosB, a gene promoting resistance to fosfomycin. Additional genes that were well represented in the chromosomes included those encoding resistance to vancomycin, clindamycin, and tetracycline. The study authors conclude that their results suggest the use of B. thuringiensis for pest control may be unintentionally facilitating the transfer of ARG in the environment.
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Oxidative Stress in Antibiotic-Treated HIV & Tuberculosis Patients
The mechanisms behind why tuberculosis patients with slow N-Acetyltransferase 2 (NAT2) genotype are at risk for developing hepatotoxicity remain unknown. In pre-clinical studies, an antibiotic used to treat patients with tuberculosis was suggested to trigger mitochondrial damage. To determine whether HIV/tuberculosis patients treated with this antibiotic have an elevated marker of oxidative stress, study investigators analyzed urine samples among this patient population prior to starting antiretroviral therapy. Levels of urinary 8-hydroxydeguanosine (8-OHdG), a marker of DNA damage, were significantly elevatead among HIV/tuberculosis patients when compared with healthy volunteers. A significant relationship was observed between NAT2 genotype and urine 8-OHdG levels. After adjusting for CD4 cell count and tuberculosis treatment duration, the researchers also observed a statistically significant increase in urine 8-OHdG levels among slow acetylators compared with rapid acetylators.
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Rapid Flu Test Impacts Length of ICU Stay
While previous studies suggest that physicians may hesitate to dispense antiviral medication to patients with false negative rapid influenza antigen test (RIAT) results for whom a considerable number may experience better outcomes with prompt antiviral use, the significance of negative RIAT results is not well understood. Researchers retrospectively analyzed upper respiratory tract samples of ICU patients with laboratory-confirmed severe influenza. Among 307 patients, RIAT was checked for 259, among with 126 (49%) were RIAT negative. Polymerase chain reaction (PCR) tests for 99 of the 126 RIAT-negative upper respiratory tract (URT) samples found 98 to be PCR-positive (99%). Among all cases, 15% had either negative results on all URT samples (RIAT, PCR, or virus culture) of no URT samples tested. Diagnosis in these cases relied upon tests of lower respiratory tract samples. RIAT-negative cases had longer ICU length of stay when compared with RIAT-positive cases (median 12 days vs 9 days), and antiviral medication was significantly delayed in RIAT-negative patients (median 1 day vs 0 days).
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HIV Infection During PrEP in PWID
Previous studies indicate that use of Pre-exposure prophylaxis (PrEP) among persons who inject drugs (PWID) appears to reduce the risk of HIV acquisition when compared with placebo. However, little is known regarding the impact of PrEP on HIV antibody response among those who become infected during PrEP, and therefore, the potential impact on timely diagnosis and treatment. Researchers evaluated longitudinal HIV-1-specific antibody responses among PWID who acquired HIV while on PrEP. HIV-1 antibody levels and avidity to three envelop proteins were measure in the plasma using a customized assay. Among study participants, longitudinal antibody levels and avidity were substantially lower in those who became HIV-infected during PrEP when compared with the placebo group. Significant differences were observed between treatment groups for all assay biomarkers. Longitudinal gp120 antibody levels within those who became HIV-infected during PrEP were significantly decreased when compared with those of the placebo group. “We document an impact on envelope antibody maturation in PWID study subjects who became infected while receiving PrEP, which has significant implications for HIV diagnosis as PrEP use expands,” write the study authors.
