Gregory Phillips

The increasing recognition that the gut microbiota plays a central role in behavior and cognition suggests that the manipulation of microbial taxa through diet may provide a means by which behavior may be altered in a reproducible and consistent manner in order to achieve a beneficial outcome for the host. Resistant starch continues to receive attention as a dietary intervention that can benefit the host through mechanisms that include altering the intestinal microbiota. Given the interest in dietary approaches to improve health, the aim of this study was to investigate whether the use of dietary resistant starch in mice to alter the gut microbiota also results in a change in behavior. Forty-eight 6 week-old male Swiss-Webster mice were randomly assigned to 3 treatment groups (n = 16 per group) and fed either a normal corn starch diet (NCS) or diets rich in resistant starches HA7 diet (HA7) or octenyl-succinate HA7 diet (OS-HA7) for 6 week and monitored for weight, behavior and fecal microbiota composition. Animals fed an HA7 diet displayed comparable weight gain over the feeding period to that recorded for NCS-fed animals while OS-HA7 displayed a lower weight gain as compared to either NCS or HA7 animals (ANOVA p = 0.0001; NCS:HA7 p = 0.244; HA7:OS-HA7 p<0.0001; NCS:OS-HA7 p<0.0001). Analysis of fecal microbiota using 16s rRNA gene taxonomic profiling revealed that each diet corresponded with a unique gut microbiota. The distribution of taxonomic classes was dynamic over the 6 week feeding period for each of the diets. At the end of the feeding periods, the distribution of taxa included statistically significant increases in members of the phylum Proteobacteria in OS-HA7 fed mice, while the Verrucomicrobia increased in HA7 fed mice over that of mice fed OS-HA7. At the class level, members of the class Bacilli decreased in the OS-HA7 fed group, and Actinobacteria, which includes the genus Bifidobacteria, was enriched in the HA7 fed group compared to the control diet. Behavioral analysis revealed that animals demonstrated profound anxiety-like behavior as observed by performance on the elevated-plus maze with time spent by the mice in the open arm (ANOVA p = 0.000; NCS:HA7 p = 0.004; NCS:OS-HA7 p = 1.000; HA7:OS-HA7 p = 0.0001) as well as entries in the open arm (ANOVA p = 0.039; NCS:HA7 p = 0.041; HA7:OS-HA7 p = 0.221; NCS:OS-HA7 p = 1.000). Open-field behavior, a measure of general locomotion and exploration, revealed statistically significant differences between groups in locomotion as a measure of transitions across quadrant boundaries. Additionally, the open-field assay revealed decreased exploration as well as decreased rearing in HA7 and OS-HA7 fed mice demonstrating a consistent pattern of increased anxiety-like behavior among these groups. Critically, behavior was not correlated with weight. These results indicate that diets based on resistant starch can be utilized to produce quantifiable changes in the gut microbiota and should be useful to "dial-in" a specific microbiome that is unique to a particular starch composition. However, undesirable effects can also be associated with resistant starch, including lack of weight gain and increased anxiety-like behaviors. These observations warrant careful consideration when developing diets rich in resistant starch in humans and animal models.

The gastrointestinal (GI) microbiota forms a mutualistic relationship with the host through complex and dynamic interactions. Because of the complexity and interindividual variation of the GI microbiota, investigating how members of the microbiota interact with each other, as well as with the host, is daunting. The altered Schaedler flora (ASF) is a model community of eight microorganisms that was developed by R.P. Orcutt and has been in use since the late 1970s. The eight microorganisms composing the ASF were all derived from mice, can be cultured in vitro, and are stably passed through multiple generations (at least 15 years or more by the authors) in gnotobiotic mice continually bred in isolator facilities. With the limitations associated with conventional, mono- or biassociated, and germfree mice, use of mice colonized with a consortium of known bacteria that naturally inhabit the murine gut offers a powerful system to investigate mechanisms governing host-microbiota relationships, and how members of the GI microbiota interact with one another. The ASF community offers significant advantages to study homeostatic as well as disease-related interactions by taking advantage of a well-defined, limited community of microorganisms. For example, quantification and spatial distribution of individual members, microbial genetic manipulation, genomic-scale analysis, and identification of microorganism-specific host immune responses are all achievable using the ASF model. This review compiles highlights associated with the 37-year history of the ASF, including descriptions of its continued use in biomedical research to elucidate the complexities of host-microbiome interactions in health and disease.

To assess the prevalence and patterns of substance use, HIV prevalence, and sexual risk behaviors in a community-based sample of heterosexuals recruited from areas at high risk for HIV/AIDS and poverty in Washington, DC. Community-recruited heterosexuals aged 18-50 from areas of high AIDS and poverty rates in DC were analyzed. Based on past 12 months use, participants were hierarchically classified into five groups: (1) ever injection drug use (IDU); (2) non-injection crack; (3) non-injection heroin and cocaine; (4) marijuana; and (5) no drug use. Sexual behaviors and HIV serology were also assessed. Of 862 participants, 40% were men, most were Black and unemployed, and more than half had ever been incarcerated. Prevalence of past year substance use was high: binge drinking (59%); marijuana (50%); non-injection crack (28%); heroin and/or cocaine injection (28%), non-injection cocaine (13%); and ecstasy (13%). In the hierarchical classification, 25% were ever IDU, 15% non-injection crack users, 2% non-injection heroin and/or cocaine users, 31% marijuana users, and 27% reported no drug use. Overall HIV seroprevalence was 5.7% and differed by drug use group-9.5%, 11.1%, 1.8%, 1.6%, and 3.2%, respectively. Nearly half reported having ≥3 sex partners in the past year; 20% reported exchange partners, and 69% had concurrent sex partners. Estimated prevalence of substance use in this heterosexual population was high. HIV prevalence among IDUs and non-injection crack users was higher than the estimated population prevalence in Washington, DC. Sexual behaviors above and beyond drug use are likely to be driving HIV transmission.

In Washington, DC, the leading mode of HIV transmission is through men who have sex with men (MSM) behavior. This study explored differences between frequent HIV testers (men testing at least twice a year) and annual or less frequent testers (men testing once a year or less) in DC. Nearly, one-third of MSM reported testing for HIV at least four times in the prior two years. In the multivariable model, frequent testers had significantly higher odds of being aged 18-34 (aOR =1.94), knowing their last partner's HIV status (aOR=1.86), having 5+ partners in the last year (aOR=1.52), and having seen a health-care provider in the last year (aOR=2.28). Conversely, frequent testers had significantly lower odds of being newly HIV positive (aOR=0.27), and having a main partner at last sex (vs. casual/exchange partner; aOR=0.59). Medical providers need to be encouraged to consistently offer an HIV test to their patients, especially those who are sexually active and who have not tested recently.

The epidemiology of HIV in urban centers of the United States such as the District of Columbia (DC) is dynamic with rates of new HIV and AIDS diagnoses as well as risk factors elevated. Correlates of HIV among heterosexual women extend beyond traditional, individual risk factors to structural factors. The purpose of this study was to compare proportions of HIV and correlates of HIV among women participating in National HIV behavioral surveillance (NHBS) system in 2006-7 (NHBS Cycle 1) and 2010 (NHBS Cycle 2). Analysis of 677 female participants at elevated risk for HIV revealed high prevalence of individual-level HIV-associated risk factors (e.g., sexual behavior) and socio-structural associated risk factors (e.g., homelessness, incarceration, lack of health insurance). While a greater proportion of women were HIV-infected in Cycle 2, after controlling for the distribution of demographic characteristics to adjust for a change in eligibility criteria, the pooled sample did not reveal a significantly increased proportion of HIV-infected women in Cycle 2. Homelessness and condom use were associated with greater relative odds of HIV after adjustment for confounders, and non-injection drug use was associated with reduced odds. Findings inform our understanding of the continuing HIV epidemic in DC and support development of effective interventions to slow the epidemic among women in DC and similar urban centers.

Current advances have added geosocial networking (GSN) mobile phone applications as an option for men who have sex with men (MSM) to meet other men. This is the first study to assess GSN application use and sex-seeking behaviors of MSM recruited using venue-based sampling. Among the 379 MSM in this study, 63.6 % reported using GSN applications to find men in the past year. Nearly one-quarter of MSM had sex with a man met using a GSN application in the prior year; these men were more likely to be under 35 years old and have had sex with a man met on the Internet; they were also less likely to be HIV-positive and have <5 male sex partners in the last year. GSN applications are a viable option for use in sampling and delivering interventions to young MSM who are often missed through other methods.

Participation of MSM in group sex events (GSEs) is an understudied phenomenon. Studies on GSEs identified significant proportions of MSM engaging in unprotected anal intercourse (UAI). We sought to identify the prevalence of group sex participation among MSM in Washington, DC and to characterize these experiences. Data were collected for NHBS-MSM-3 in 2011. More than one-quarter of MSM (27.2 %) reported engaging in group sex in the prior year, with one-third reporting no condom use with their sex partners (33.0 %). In multivariable logistic regression, men who participated in a GSE in the prior year were significantly younger, more likely to be white, and to have used crystal meth, poppers, and downers in the past year. The high prevalence of UAI during GSEs, especially in view of the fact that HIV-positive MSM were significantly less likely to report condom use, offers an opportunity to develop risk reduction interventions specific to GSE attendees.