Investigating the epidemiology of repeat Chlamydia trachomatis detection after treatment by using C. trachomatis OmpA genotyping.

Repeat Chlamydia trachomatis detection frequently occurs within months after C. trachomatis infection treatment. The origins of such infection (persistence versus reinfection from untreated or new partners) are varied and difficult to determine. C. trachomatis strains can be differentiated by sequencing the ompA gene encoding the outer membrane protein A (OmpA). We used OmpA genotyping to investigate the epidemiology of repeat C. trachomatis detection after treatment in C. trachomatis-infected subjects seen at a sexually transmitted diseases clinic. Subjects were enrolled, tested for C. trachomatis, treated with azithromycin, and scheduled for a 6-month follow-up for repeat C. trachomatis testing. OmpA genotyping was performed on C. trachomatis-positive urogenital specimens obtained from patients at enrollment and follow-up. The enrollment visit OmpA genotypes for C. trachomatis were determined for 162 subjects (92% female, 94% African American). C. trachomatis was detected at follow-up in 39 subjects (24%). The OmpA genotype distribution at enrollment did not differ in those with versus those without repeat C. trachomatis detection. Of the 35 subjects with C. trachomatis strains genotyped at enrollment and follow-up, 7 (20%) had the same ompA sequence at both visits, while 28 (80%) had discordant sequences. A new sexual partner was reported more often in subjects with discordant C. trachomatis strains than in those with concordant strains (13 [46%] versus 1 [14%]; P = 0.195). Half of the subjects with discordant C. trachomatis strains who reported sexual activity since treatment denied a new sexual partner; 62% of these subjects reported that their partner was treated. Our study demonstrates that most repeat C. trachomatis detections after treatment were new infections with a different C. trachomatis strain rather than reinfection with the same strain. OmpA genotyping can be a useful tool in understanding the origins of repeat C. trachomatis detection after treatment.

Naltrexone-induced conditioned place aversion following a single dose of morphine in the rat.

Limited preclinical research has been conducted investigating the motivational or "affective" properties of withdrawal from acute opioid dependence following a single morphine exposure. Therefore, the purpose of the present study was to pharmacologically characterize the motivational properties associated with naltrexone-precipitated withdrawal after a single injection of morphine using place conditioning. Conditioned place aversion was assessed using a biased two-compartment apparatus and procedure. Adult male Sprague-Dawley rats were given 15 min free access to the entire apparatus on day one to determine initial preferences. Beginning on the second day, combinations of either saline or morphine (1.0-10 mg/kg, s.c.) followed by naltrexone (0.003-3.0 mg/kg, s.c.) 3.75 h later were administered. Rats were then immediately confined to one compartment for 30 min. The next day, rats received the alternative treatment and were confined to the opposite compartment. Twenty-four hours later animals were tested again for 15 min while they had access to the entire apparatus. Morphine followed by naltrexone conditioned significant place aversion (CPA) with just one pairing. This effect was a function of the naltrexone and morphine doses. CPA was also dependent on morphine pretreatment time, with significant aversion only occurring 4 h after morphine pretreatment. Finally continuous morphine administration followed by a single injection of naltrexone resulted in CPA. These data extend the range of behavioral effects associated with antagonist-precipitated withdrawal from acutely administered morphine and suggest that place conditioning is an effective model in assessing motivational aspects of withdrawal from acute opioid dependence in rats.