Top Infectious Disease News of the Week—October 6, 2019

#5: What's New From the CLSI Subcommittee on Antimicrobial Susceptibility Testing

The Clinical and Laboratory Standards Institute (CLSI) Subcommittee on Antimicrobial Susceptibility Testing (AST) held its 2019 meetings in January and June, introducing several new and revised breakpoints. Although the subcommittee approved certain breakpoints in June 2019, they are subject to change prior to official approval of the meeting minutes at the January 2020 meeting.

NOTEWORTHY NOVEL AND REVISED BREAKPOINTS

Azithromycin for Neisseria gonorrhoeae

Current recommendations from the US Centers for Disease Control and Prevention and the World Health Organization support combination therapy with ceftriaxone (250 mg, intramuscular) plus azithromycin (1 g, oral) for the treatment of uncomplicated gonorrhea.¹ The hope for dual therapy of agents with different mechanisms of action is to slow the emergence and spread of resistance to ceftriaxone, as resistance of N gonorrhoeae to other antimicrobial classes (eg, fluoroquinolones) has been documented in recent years.^1,2 Azithromycin minimal inhibitory concentration (MIC) distribution data and clinical efficacy data were reviewed at the June 2018 meeting, and a “susceptible-only” breakpoint of ≤1 mg/L was justified by the wild-type susceptibility distribution and lack of sufficient clinical efficacy data for isolates with MICs between 2 and 8 mg/L. This new breakpoint was subsequently published in the 2019 (29th edition) of the M100 document (Table 1).³ A comment that azithromycin use is required as part of a combination regimen was also included.

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#4: Can Grindr Screen Time Measure HIV Risk?

As dating apps have grown in popularity more and more Americans are using technology to find sexual partners. According to recent estimates, ≥60% of men who have sex with men (MSM) find sexual partners via the internet, primarily through Grindr, which is the most popular dating app among MSM.

In the past, studies have found inconsistent results regarding the association between Grindr use and increased HIV risk behavior. However, in a new study, presented in an oral abstract presentation at IDWeek 2019, investigators sought to assess Grindr on-screen activity and to correlate activity with risk behavior and substance use among MSM in San Diego undergoing community-based HIV and sexually transmitted infection screening.

The investigators conducted a nested cohort study between December 2018 and April 2019, using the “Good to Go” screening program to recruit 784 participants. During testing, participants who were not currently on a pre-exposure prophylaxis (PrEP) regimen completed a survey on demographic information, substance use and risk behavior over the previous 3 months, and Grindr usage.

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#3: Opioid Crisis Shifts Hepatitis C Virus to Millennial Generation

Hepatitis C virus (HCV) infection has skipped a generation and become a predominantly millennial disease, according to a poster presented during IDWeek 2019.

Investigators from the University of Louisville screened 82,243 individuals for HCV infection in 2016-2018 in Norton Healthcare in order to assess trends in a large health care system in an area with a high prevalence of opioid use and HCV infection. The investigators defined millennials as individuals born between 1980 and 1995, and baby boomers were those born between 1945 and 1965.

Traditionally, baby boomers were the largest drivers of HCV, though millennials have been shown in previous research to be the fastest-growing population of those infected with the virus. However, those studies were performed at single institutions with small sample sizes.

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#2: Ceftolozane/Tazobactam Deemed Safe, Effective Against Drug-Resistant P aeruginosa

A dangerous drug-resistant hospital-acquired infection that has raised increasing concern among public health officials can be effectively treated with a drug already on the market, according to new research.

A new study published last month in Clinical Infectious Diseases finds the combination of ceftolozane and tazobactam is safe and effective for patients with drug-resistant Pseudomonas aeruginosa when compared with polymyxins or aminoglycosides.

The findings suggest the novel cephalosporin/beta-lactamase inhibitor would be the better option for patients dealing with multidrug resistant (MDR) or extensively drug resistant (XDR) P aeruginosa infections.

As drug resistance has become a bigger and bigger problem when treating P aeruginosa, providers have increasingly relied on polymyxins and aminoglycosides. Those drugs are a less-than-ideal solution, though, according to study author Jason M. Pogue, PharmD, of the University of Michigan College of Pharmacy, and colleagues. At IDWeek 2019, Contagion® spoke to Pogue, a member of the Contagion® Editorial Advisory Board, about the research.

Read the full article and watch the interview with Jason Pogue, PharmD.

#1: Switching From TDF to TAF-Containing ART Carries BMI, Atherosclerotic Cardiovascular Disease Risk

The benefits of switching from tenofovir disoproxil fumarate (TDF) to tenofovir alafenamide (TAF)-containing antiretroviral therapy (ART) are known and include preserved or improved renal function and bone mineral density in patients living with HIV (PLWH).

However, the effects of the switch on body mass index (BMI) and atherosclerotic cardiovascular disease (ASCVD) risk is unclear. That’s what investigators at Jefferson College of Pharmacy sought to do in a retrospective observational study of virologically suppressed adults living with HIV, which was presented at IDWeek 2019.

Adult patients on TDF for > 1 year with 2 consecutive HIV viral loads < 200 copies/mL in the year prior to a TAF switch were included in the study evaluating BMI and ASCVD risk score changes. Investigators collected and recorded body weight, BMI, cholesterol, ASCVD risk score, and other variables for the year prior to and following the switch. Besides a switch from TDF to TAF, no other ART regimen components were changed for patients included in the study.

Investigators used the Wilcoxon signed-rank test to compare unadjusted distributions of pre and post switch values, and constructed repeated measures generalized estimating equations to evaluate changes in BMI and ASCVD risk scores associated with switching from TDF to TAF. They were adjusted for predicters retained in the model if their p-values were < 005. Finally, the ASCVD risk scores skewed right, so the research team log-transformed the data prior to modeling.

A total of 110 patients were included in the analysis. In the unadjusted set, weight, BMI, total cholesterol, LDL, HDL, and ASCVD score had all significantly increased in the year following the switch (each p ≤ 0.01). Gender was the only factor retained in the adjusted BMI model, which showed that a switch from TDF to TAF resulted in an increase of 0.45 kg/m² in the expected mean for BMI (95% confidence interval [CI]: 0.14, 0.76).

Read the full article and watch the interview with presenting author Jason Schafer, PharmD.