Protein engineering of lipase A from Candida antarctica to improve esterification of tertiary alcohols.

Chiral tertiary alcohols are important organic compounds in science as well as in industry. However, their preparation in enantiomerically pure form is still a challenge due to their complex structure and steric hindrances compared with primary and secondary alcohols, so kinetic resolution could be an attractive approach.  Lipase A from Candida antarctica (CAL-A) has been shown to catalyze the enantioselective esterification of various tertiary alcohols with excellent enantioselectivity but low activity. Here we report a mutagenesis study by rational design to improve CAL-A activity against tertiary alcohols. Single mutants of CAL-A were selected, expressed, immobilized and screened for esterification of the tertiary alcohol 1,2,3,4-tetrahydronaphthalene-1-ol. A double mutant V278S+S429G showed a 1.5-fold higher reaction rate than that of the wild type CAL-A, while maintaining excellent enantioselectivity.

Stereodivergent Biocatalytic Formal Reduction of α-Angelica Lactone to (R)- and (S)-γ-Valerolactone in a One-Pot Cascade.

The formal asymmetric and stereodivergent enzymatic reduction of α-angelica lactone to both enantiomers of γ-valerolactone was achieved in a one-pot cascade by uniting the promiscuous stereoselective isomerization activity of Old Yellow Enzymes with their native reductase activity. In addition to running the cascade with one enzyme for each catalytic step, a bifunctional isomerase-reductase biocatalyst was designed by fusing two Old Yellow Enzymes, thereby generating an unprecedented case of an artificial enzyme catalyzing the reduction of nonactivated C=C bonds to access (R)-valerolactone in overall 41 % conversion and up to 91 % ee. The enzyme BfOYE4 could be used as single biocatalyst for both steps and delivered (S)-valerolactone in up to 84 % ee and 41 % overall conversion. The reducing equivalents were provided by a nicotinamide recycling system based on formate and formate dehydrogenase, added in a second step. This enzymatic system provides an asymmetric route to valuable chiral building blocks from an abundant bio-based chemical.

Adverse childhood experiences, antenatal stressful life events, and marijuana use during pregnancy: A population-based study.

Cumulative exposure to adverse childhood experiences (ACEs) and antenatal stressful life events (ASLEs) are independently associated with marijuana use during pregnancy. However, research has not explored how both exposures may influence marijuana use jointly. Assessing the joint associations of ACEs and recent ASLEs on marijuana use can identify people who may benefit from early intervention. Data come from the Nevada Pregnancy Risk Assessment Monitoring System, 2017-2020 (N = 2483). We assessed eight measures of ACEs before age 18 and fourteen measures of ASLEs twelve months before giving birth. Generalized estimating equations estimated the direct and joint associations (additive and multiplicative interaction) of ACEs and ASLEs on marijuana use during pregnancy. 9.8% used marijuana during the most recent pregnancy. Compared to people who reported no ACEs, those reporting 1 ACE (adjusted prevalence ratio[aPR] = 1.96, 95% confidence interval [CI] = 1.30-2.94), 3 ACEs (aPR = 3.58, 95%CI = 2.69-4.77), and 4+ ACEs (aPR = 3.67, 95%CI = 2.36-5.72) were more likely to use marijuana. Compared to people reporting no ASLEs, those reporting 4+ ASLEs (aPR = 3.12, 95% CI = 1.64-5.92) were more likely to use marijuana. There was evidence of interaction for high ACE and ASLE exposure on an additive scale. ACEs and ASLEs were independently associated with marijuana use during pregnancy, and there was evidence of additive interaction. Screening for ACEs and ASLEs during pregnancy, referrals to appropriate behavioral health services, and trauma-informed approaches are important to address marijuana use during pregnancy.

Characteristics of Individuals Seen as Sources of Social Support in Populations at Increased Risk for HIV.

Access to social support from one's social network can serve as a protective factor against HIV infection; however, research exploring the availability of support in diverse populations that include high proportions of people at increased risk for HIV and the characteristics of network members associated with access to such support is limited. Multi-level dyadic analyses of social network data collected from women at risk for HIV and their network members reveal which individual and relationship characteristics of network members are associated with providing emotional, material, and/or health informational support. Results indicate that access to all three types of support was associated with a network member being a friend, a member of a participant's 'core' group, someone whose opinion matters to the respondent, and the respondent trusting them. These findings have implications for interventions designed to increase access to support among individuals at risk for HIV.

Associations between Circumstances Surrounding Overdose and Underlying Classes of Polysubstance Overdose Deaths.

BACKGROUND: The overdose crisis is worsening, with polysubstance overdose deaths involving psychostimulants increasing in the U.S. Substance-specific prevention and intervention activities may not be as effective for polysubstance use, so we sought to classify substances used among overdose decedents to identify unique factors related to these classes. METHODS: We used data from the Nevada State Unintentional Drug Overdose Reporting System, Jan 2019-Jun 2021, which comes from death certificates, coroner/medical examiner reports, and postmortem toxicology. Latent class analysis, multinomial logistic regression, and Chi-squared tests determined underlying drug use classes, differences in characteristics and circumstances surrounding overdose, and assessed relationships between circumstances and drug use classes. RESULTS: We identified four latent classes: (1) prescription drugs (19.1%), (2) predominately methamphetamine (31.4%), (3) multi-drug (28.9%), and (4) opioid and stimulant (20.6%). Compared to other classes, the prescription drug class had a higher percentage of female decedents, from rural counties, with mental health diagnoses, who died at home. The predominately methamphetamine class had a higher percentage of decedents experiencing homelessness. The multi-drug use class had higher percentage of younger and Hispanic decedents. Those in the opioid and stimulant class had higher odds of being recently released from an institutional setting, compared to the multi drug class. CONCLUSIONS: These underlying classes were associated with several characteristics and circumstances that can prove useful for prevention, treatment, and harm reduction agencies when designing programs and interventions to target specific groups of people at-risk for drug overdose.

Enantiodivergent Chemoenzymatic Dynamic Kinetic Resolution: Conversion of Racemic Propargyl Alcohols into Both Enantiomers.

Natural lipases typically recognize enantiomers of alcohols based on the size differences of substituents near the carbinol moiety and selectively react with the R enantiomers of secondary alcohols. Therefore, lipase-catalyzed dynamic kinetic resolution (DKR) of racemic secondary alcohols produces only R enantiomers. We report herein a method for obtaining S enantiomers by DKR of secondary 3-(trialkylsilyl)propargyl alcohols by using a well-known R-selective Pseudomonas fluorescens lipase in combination with a racemization catalyst VMPS4, in which the silyl group reverses the size relationship of substituents near the carbinol moiety. We have already reported R-selective DKR of the corresponding propargyl alcohols without substituents on the ethynyl terminal carbon, and the presence of an easily removable silyl group has enabled us to produce both enantiomers of propargyl alcohols in high chemical yields and with high enantiomeric excess. In addition, immobilization of the lipase on Celite was found to be important for achieving a high efficiency of the DKR.

Who Can I Ask? Who Would I Tell? An Egocentric Network Analysis Among a Sample of Women At-Risk to Explore Anticipated Advice Seeking and Disclosure Around Pre-exposure Prophylaxis (PrEP).

Pre-Exposure Prophylaxis (PrEP) health campaigns invite women to talk with their provider, partner, and peers about PrEP, though they do not offer specific guidance about who and how to engage. This study uses egocentric network methods in a sample of women at risk for HIV to understand what characteristics of women (egos), their networks, and network members (alters) were associated with anticipated PrEP advice-seeking and anticipated PrEP disclosure. Multivariable generalized linear mixed models revealed that women often consider close, supportive, and trusted network members as PrEP discussants while ego-level, network-level, and cross-level interactions depict the complexity of anticipated network activation. Findings highlight the importance of considering women at risk for HIV in a broader social context. Anticipated advice-seeking and disclosure related to PrEP were associated but distinct forms of network activation, which highlights the need to develop specific recommendations about who and how women should engage with their networks around PrEP.

Association of social network characteristics with HIV knowledge, stigma, and testing: findings from a study of racial and ethnic minority women in a small Western city.

Black and Latina women are disproportionately impacted by HIV/AIDS. Despite existing research linking social networks and HIV risk among men who have sex with men (MSM) and other high-risk populations, little research has examined how ethnic/racial minority women's social networks shape HIV prevention and intervention targets. Using interviews with a sample of 165 predominantly Black and Latina-identifying women from a small city in the Western U.S., this research examines the relationship between egocentric network characteristics and HIV knowledge, attitudes, and testing history. Results reveal that network characteristics play a significant role in shaping HIV-related knowledge, prejudice, and testing intention but not HIV testing history. Individual-level factors like homelessness and perceptions of testing barriers are more salient for explaining testing behaviors than network characteristics. Intervention efforts to improve knowledge and reduce prejudice among Black and Latina women may benefit from mobilizing network ties.

Identification of Non-Fatal Opioid Overdose Cases Using 9-1-1 Computer Assisted Dispatch and Prehospital Patient Clinical Record Variables.

Background: The current epidemic of opioid overdoses in the United States necessitates a robust public health and clinical response. We described patterns of non-fatal opioid overdoses (NFOODs) in a small western region using data from the 9-1-1 Computer Assisted Dispatch (CAD) record and electronic Patient Clinical Records (ePCR) completed by EMS responders. We determined whether CAD and ePCR variables could identify NFOOD cases in 9-1-1 data for intervention and surveillance efforts. Methods: We conducted a retrospective analysis of 1 year of 9-1-1 emergency medical CAD and ePCR (including naloxone administration) data from the sole EMS provider in the response area. Cases were identified based on clinician review of the ePCR, and categorized as definitive NFOOD, probable NFOOD, or non-OOD. Sensitivity, specificity, positive and negative predictive values (PPV and NPV) of the most prevalent CAD and ePCR variables were calculated. We used a machine learning technique-Random-Forests (RF) modeling-to optimize our ability to accurately predict NFOOD cases within census blocks. Results: Of 37,960 9-1-1 calls, clinical review identified 158 NFOOD cases (0.4%), of which 123 (77.8%) were definitive and 35 (22.2%) were probable cases. Overall, 106 (67.1%) received naloxone from the EMS responder at the scene. As a predictor of NFOOD, naloxone administration by paramedics had 67.1% sensitivity, 99.6% specificity, 44% PPV, and 99.9% NPV. Using CAD variables alone achieved a sensitivity of 36.7% and specificity of 99.7%. Combining ePCR variables with CAD variables increased the diagnostic accuracy with the best RF model yielding 75.9% sensitivity, 99.9% specificity, 71.4% PPV, and 99.9% NPV. Conclusion: CAD problem type variables and naloxone administration, used alone or in combination, had sub-optimal predictive accuracy. However, a Random Forests modeling approach improved accuracy of identification, which could foster improved surveillance and intervention efforts. We identified the set of NFOODs that EMS encountered in a year and may be useful for future surveillance efforts.

The group-based law enforcement mistrust scale: psychometric properties of an adapted scale and implications for public health and harm reduction research.

BACKGROUND: Negative encounters with law enforcement-direct and vicarious-fuel mistrust. When considered as part of the 'risk environment' in public health and harm reduction research, law enforcement mistrust may have broad implications. For example, fearing arrest may prevent someone from calling 911 when witnessing an overdose or lead to syringe-sharing and community spread of HIV. For people in the US who identify as Black or African American, these effects may compound, given the ways in which communities of color have been overpoliced. The purpose of this study is to investigate the psychometrics of an adapted scale of law enforcement mistrust-the Group-Based Law Enforcement Mistrust Scale (GBLEMS)-and evaluate its associations with racial and ethnic identity and experiences with law enforcement. METHODS: This cross-sectional survey took place in a small city in the Western United States where only 3% of the population is Black or African American. The sample included Black or African American and Hispanic and Latina women at risk of HIV, and members of their social networks, yielding a diverse sample across racial, ethnic, and gender identities (N = 219). The GBLEMS is a 12-item scale adapted from the Group-Based Medical Mistrust Scale (GBMMS; Thompson et al. 2004). The current analysis evaluated the psychometric properties of the GBLEMS (reliability, exploratory factor analysis) and its associations with demographics, other race-based constructs, and experiences with law enforcement. RESULTS: The GBLEMS demonstrated strong reliability (Cronbach's alpha = 0.92) and exploratory factor analysis indicated that items loaded onto two factors-mistrust and disparities in treatment. There was also support for the scale's construct validity. As hypothesized, GBLEMS scores were higher among respondents who identify as Black or African American, and among those who reported other experiences of racial discrimination, medical mistrust, and negative encounters with law enforcement. CONCLUSIONS: This study yielded support for the reliability and validity of the GBLEMS as a multi-item, two-factor scale measuring group-based law enforcement mistrust. When framing public health and harm reduction research in terms of the risk environment, law enforcement mistrust may be important to measure as part of a comprehensive approach that addresses persistent racial disparities.

"It's called overamping": experiences of overdose among people who use methamphetamine.

BACKGROUND: The USA is experiencing increases in methamphetamine use and methamphetamine-related or attributed deaths. In the current study, we explore qualitative narratives of methamphetamine overdose and strategies used by people who use drugs to reduce the undesirable effects associated with methamphetamine use. METHODS: We conducted 21 qualitative interviews with people over the age of 18 who reported using methamphetamine in the previous 3 months in Nevada and New Mexico. Interviews were recorded, transcribed, and analyzed using qualitative thematic analysis. RESULTS: Respondents described a constellation of psychological and physical symptoms that they characterized as "overamping," experienced on a continuum from less to more severe. Reports of acute, fatal methamphetamine overdose were rare. Few reported seeking medical attention for undesirable effects (usually related to psychological effects). General self-care strategies such as sleeping and staying hydrated were discussed. CONCLUSIONS: When asked directly, our respondents claimed that acute, fatal methamphetamine overdose is rare or even impossible. However, they described a number of undesirable symptoms associated with overconsumption of methamphetamine and had few clinical or harm reduction strategies at their disposal. Addressing this current wave of drug-related deaths will require attention to the multiple factors that structure experiences of methamphetamine "overdose," and a collaborative effort with PWUDs to devise effective harm reduction and treatment strategies.

Factors Associated With Calling 911 for an Overdose: An Ethnographic Decision Tree Modeling Approach.

Objectives. To identify factors that influence when people who use drugs (PWUDs) call 911 for an overdose. Methods. We conducted 45 qualitative interviews and 180 surveys with PWUDs who had recently witnessed overdoses in Southern California from 2017 to 2019. We used conditional inference tree and random forest models to generate and validate a model to predict whether 911 would be called. Results. Our model had good in- (83%) and out-of-sample (84%) predictive accuracy. Three aspects of the social and policy environment influenced calling 911 for an overdose: the effectiveness of response strategies employed, the behavior of other bystanders, and whether the responder believes it is their responsibility to call. Conclusions. Even in the presence of policies that provide some protections, PWUDs are faced with difficult decisions about calling 911 and must weigh their own safety against that of an overdose victim. Potential interventions include strengthening training and safety planning for PWUDs, bolstering protections for PWUDs when they call 911, and separating law enforcement response from emergency medical response to overdoses.

"It's Gonna be a Lifeline": Findings From Focus Group Research to Investigate What People Who Use Opioids Want From Peer-Based Postoverdose Interventions in the Emergency Department.

STUDY OBJECTIVE: Postoverdose interventions that deploy peer recovery support specialists to emergency departments (EDs) are a promising response to opioid overdoses among patients presenting in EDs. The objective of this study was to elicit patients' perspectives regarding the feasibility and acceptability of such an intervention and to ensure that their perspectives are represented in intervention design, implementation, and evaluation. METHOD: In 2019 the study investigators conducted focus groups with people who use opioids to elicit perspectives about a postoverdose intervention delivered in the ED by using a semistructured interview guide that asked about feasibility, acceptability, perceived benefits, and concerns. Focus groups were digitally recorded, transcribed, and analyzed for emerging themes. RESULTS: Nine focus groups with 30 people who use opioids were conducted. Key findings that could improve feasibility and acceptability of the intervention include the following: the importance of balancing the urgency of seeing patients quickly with a need to accommodate the experience of precipitated withdrawal symptoms; the need to address privacy concerns; and the need to address concerns related to cost, insurance coverage, and sustainability. Perceived benefits of the intervention included the ability of the peer recovery support specialist to provide advocacy and support, serve as a model of hope and encouragement for behavior change, and fill key service gaps. CONCLUSION: Postoverdose interventions in the ED provide the opportunity to integrate harm reduction-based interventions into traditional biomedical care facilities. These interventions can fill gaps in services and provide additional care and comfort for people who use opioids, but design, implementation, and evaluation should be informed by a patient-centered care perspective.

Impact of Public Safety Policies on Human Immunodeficiency Virus Transmission Dynamics in Tijuana, Mexico.

Background: North Tijuana, Mexico is home to many individuals at high risk for transmitting and acquiring human immunodeficiency virus (HIV). Recently, policy shifts by local government impacted how these individuals were handled by authorities. Here we examined how this affected regional HIV transmission dynamics. Methods: HIV pol sequences and associated demographic information were collected from 8 research studies enrolling persons in Tijuana and were used to infer viral transmission patterns. To evaluate the impact of recent policy changes on HIV transmission dynamics, qualitative interviews were performed on a subset of recently infected individuals. Results: Between 2004 and 2016, 288 unique HIV pol sequences were obtained from individuals in Tijuana, including 46.4% from men who have sex with men, 42.1% from individuals reporting transactional sex, and 27.8% from persons who inject drugs (some individuals had >1 risk factor). Forty-two percent of sequences linked to at least 1 other sequence, forming 37 transmission clusters. Thirty-two individuals seroconverted during the observation period, including 8 between April and July 2016. Three of these individuals were putatively linked together. Qualitative interviews suggested changes in policing led individuals to shift locations of residence and injection drug use, leading to increased risk taking (eg, sharing needles). Conclusions: Near real-time molecular epidemiologic analyses identified a cluster of linked transmissions temporally associated with policy shifts. Interviews suggested these shifts may have led to increased risk taking among individuals at high risk for HIV acquisition. With all public policy shifts, downstream impacts need to be carefully considered, as even well-intentioned policies can have major public health consequences.

Cold Preparation of Heroin in a Black Tar Market.

BACKGROUND: Black tar heroin is typically prepared for injection with heat which decreases the risk of HIV transmission by inactivating the virus. We received reports that persons who inject drugs (PWID) in Tijuana, Baja California, Mexico, a black tar heroin market, were using only water to dissolve heroin. OBJECTIVES: Because Tijuana abuts San Diego County, CA, United States, we undertook the present analyses to determine the prevalence of this practice among PWID in San Diego, California. METHODS: PWID completed quarterly behavioral assessments and serological testing for blood-borne viruses. Bivariate and multivariable logistic regression models were constructed to assess for individual, social, and structural correlates of preparing heroin without heat within the preceding 6 months. RESULTS: Nearly half of black tar heroin users (149/305) reported they had prepared heroin without heat within 6 months. In multivariable analysis, cold preparation was independently associated with younger age (10 year decrease; AOR = 1.25; 95% CI 1.03, 1.53), more drug injecting acquaintances (per 5 acquaintance increase; AOR = 1.05; 95% CI 1.01, 1.09) and prefilled syringe use (injecting drugs from syringes that are already filled with drugs before purchase; AOR = 1.86; 95% CI 1.14, 3.02). Conclusions/Importance: To our knowledge, this is the first paper to report that PWID living in a black tar heroin market are preparing heroin without heat. Additional research is needed to determine whether this is an endemic practice or PWID are engaging in new forms of drug preparation in response to changes in the environment.

Place of Residence Moderates the Relationship Between Emotional Closeness and Syringe Sharing Among Injection Drug Using Clients of Sex Workers in the US-Mexico Border Region.

Injection drug-using men from the US and Mexico who purchase sex in Tijuana, Mexico are at risk for transmitting HIV to their contacts in both countries via syringe sharing. We used social network methods to understand whether place of residence (US vs. Mexico) moderated the effect of emotional closeness on syringe sharing. We interviewed 199 drug-using men who reported paying/trading for sex in Tijuana, Mexico using an epidemiological and social network survey and collected samples for HIV/STI testing. Seventy-two men reported using injection drugs with 272 network contacts. Emotional closeness was strongly associated with syringe sharing in relationship where the partner lives in the US, while the relationship between emotional closeness and syringe sharing was considerably less strong in dyads where the partner lives in Mexico. Efforts to reduce HIV risk behaviors in emotionally close relationships are needed, and could benefit from tailoring to the environmental context of the relationship.

Prevalence and Correlates of the Use of Prefilled Syringes Among Persons Who Inject Drugs in San Diego, CA.

Persons who inject drugs (PWID) are at increased risk for blood-borne virus (BBV) infections and overdose resulting from high-risk injecting practices. Studies of prefilled syringe use ([PFSU] using a syringe that already contained drug solution when it was obtained by the user), an injection practice previously described in Eastern Europe, suggest that it increases susceptibility to BBV. However, little is known about this practice in the USA. Data were obtained from an ongoing cohort study of PWID to determine the prevalence and assess correlates of PFSU in San Diego, CA. Baseline interviews assessed socio-demographics and drug use behaviors. Logistic regression was used to identify factors independently associated with ever using a prefilled syringe (yes/no). Participants (n = 574) were predominately males (73.9%) and white (50.9%) with a mean age of 43.4 years (range 18-80); 33.3% reported ever using prefilled syringes, although only 4.9% reported use in the past 6 months. In multivariable analyses, PFSU was independently associated with ever having a rushed injection due to police presence [adjusted odds ratio (AOR) = 2.51, 95% CI 1.66, 3.79], ever being in prison (AOR = 1.80, 95% CI 1.23, 2.63), injecting most often in public versus private places in the past 6 months (AOR = 1.66, 95% CI 1.11, 2.48), and injecting drugs in Mexico (AOR = 1.70, 95% CI 1.16, 2.49). Results indicate that a history of PFSU is common and associated with environmental factors that may also increase risk for adverse health outcomes. Studies are needed to better understand PFSU in order to develop interventions to prevent adverse outcomes associated with their use.

Patterns of drug use, risky behavior, and health status among persons who inject drugs living in San Diego, California: a latent class analysis.

BACKGROUND: Among persons who inject drugs (PWID), polydrug use (the practice of mixing multiple drugs/alcohol sequentially or simultaneously) increases risk for HIV transmission and unintentional overdose deaths. Research has shown local drug markets influence drug use practices. However, little is known about the impact of drug mixing in markets dominated by black tar heroin and methamphetamine, such as the western United States. METHODS: Data were collected through an ongoing longitudinal study examining drug use, risk behavior, and health status among PWID. Latent class analysis (LCA) was used to identify patterns of substance use (heroin, methamphetamine, prescription drugs, alcohol, and marijuana) via multiple administration routes (injecting, smoking, and swallowing). Logistic regression was used to identify behaviors and health indicators associated with drug use class. RESULTS: The sample included 511 mostly white (51.5%) males (73.8%), with mean age of 43.5 years. Two distinct classes of drug users predominated: methamphetamine by multiple routes (51%) and heroin by injection (49%). In multivariable logistic regression, class membership was associated with age, race, and housing status. PWID who were HIV-seropositive and reported prior sexually transmitted infections had increased odds of belonging to the methamphetamine class. Those who were HCV positive and reported previous opioid overdose had an increased odds of being in the primarily heroin injection class (all P-values < .05). CONCLUSION: Risk behaviors and health outcomes differed between PWID who primarily inject heroin vs. those who use methamphetamine. The findings suggest that in a region where PWID mainly use black tar heroin or methamphetamine, interventions tailored to sub-populations of PWID could improve effectiveness.

Transitions in latent classes of sexual risk behavior among young injection drug users following HIV prevention intervention.

We analyzed data from a large randomized HIV/HCV prevention intervention trial with young injection drug users (IDUs). Using categorical latent variable analysis, we identified distinct classes of sexual behavior for men and women. We conducted a latent transition analysis to test the effect of the intervention on transitions from higher to lower risk classes. Men who were in a high-risk class at baseline who received the intervention were 86 % more likely to be in a low-risk class at follow-up compared to those in the control group (p = 0.025). High-risk intervention participants were significantly more likely to transition to the class characterized by unprotected sex with a main partner only, while low-risk intervention participants were significantly less likely to transition to that class. No intervention effect was detected on the sexual risk behavior of women, or of men who at baseline were having unprotected sex with a main partner only.

Correlates of self-efficacy for condom use among male clients of female sex workers in Tijuana, Mexico.

Male clients of female sex workers (FSWs) in Tijuana, Mexico engage in high levels of unprotected sex. While behavioral change theories posit that self-efficacy predicts condom use, correlates of self-efficacy for condom use remain largely unstudied. We examined these correlates among male clients of FSWs in Tijuana. Eligible male clients were at least 18 years of age, HIV-negative, lived in Tijuana or San Diego, reported unprotected sex with a Tijuana FSW at least once in the past 4 months, and agreed to be treated for sexually transmitted infections (STIs). Participants completed an interviewer-administered questionnaire including demographics, substance use, psychosocial and psychosexual characteristics (e.g., outcome expectancies for negotiation of safer sex, social support, and sexual sensation seeking), and sexual behaviors. Participants also underwent HIV/STI testing. A stepwise hierarchical multiple regression analysis identified correlates of self-efficacy for condom use. Of 393 male clients, median age was 37 years. Participants were mostly Spanish-speaking and employed. Factors independently associated with higher self-efficacy for condom use were higher positive outcome expectancies for negotiation of safer sex, lower sexual sensation seeking scores, and higher social support scores. Both psychosocial and psychosexual factors may influence self-efficacy for condom use among male clients of FSWs. These factors represent central constructs in sociocognitive models that explain behavioral change and could be intervention targets for improving self-efficacy for condom use and, ultimately, safer sex behavior.