Updates

By Carol A. Kemper, MD, FACP, Clinical Associate Professor of Medicine, Stanford University, Division of Infectious Diseases; Santa Clara Valley Medical Center, Section Editor, Updates; is Associate Editor for Infectious Disease Alert.

Do I Smell a Rat — Smelling TB?

Source: Poling A, et al. Using giant African pouched rats to detect tuberculosis in human sputum samples: 2009 findings. Am J Trop Med Hyg. 2010;83:1308-1310.

As reported here in 2003, the World Bank began funding a project to train giant pouched Gambian rats to sniff out tuberculosis (TB) in sputum specimens in sub-Saharan Africa. Rats have been successfully trained to target landmines, and using a similar training/reward technique, pilot data suggested that rats could be trained to detect TB in respiratory specimens. Compared to a trained technician (~ 95% accuracy), preliminary data in 2003 suggested the rats were able to detect TB in 92% of smear-positive cases and 77% of culture-positive cases, with a 2% false-positive rate.

The rats have since gotten better. While trained technicians were able to identify AFB in 13.3% of 10,523 respiratory specimens by light microscopy, the rats were able to detect an additional 600 cases. When multiple rats were allowed to pause for 5 seconds over each specimen, the specificity improved to 89%. All it takes is training — and bananas. Compared to a trained technician, who can process about 20 specimens in a day, the rats are much more efficient — but they don't do any clean up.

Safer-sex Intervention for HIV-discordant Couples

Source: El_Bassel N, et al. National Institute of Mental Health Multisite Eban HIV/STD prevention intervention for African-American HIV serodiscordant couples. Arch Intern Med. 2010;170:1594-1601.

Researchers in four american cities (Los Angeles, Philadelphia, Atlanta, and New York) participated in a multi-state HIV- and STD-prevention trial in African-American HIV-discordant heterosexual couples (> 18 years of age). A total of 535 couples who reported unprotected sex within the prior three months were randomized to a safer-sex intervention based on the "Eban" system or to a health-promotion (HP) group. The Eban system is based on an African concept of fencing off a safe space for loved ones and family as a form of protecting the family unit. Couples in this group participated in eight weekly 2-hour sessions with play acting, problem solving, communication, and negotiation. Using a blocked randomization algorithm, different couples received Eban intervention as a single couple, in groups of couples, or in same-sex groups. In contrast, the HP group received individual health counseling.

The primary outcome was the number of condom-protected acts of intercourse over the next 12-month period. Secondary outcomes included the cumulative incidence of STDs and HIV seroconversion.

The woman was the positive partner in 60% of the couples (varying from 57% to 64% between sites). Attendance at the Eban sessions was remarkably good — the average attendance was 91%, with 86% of the couples attending all eight sessions. In comparison, 76% of the couples participated in all of the HP sessions.

Following the Eban sessions, the number of couples who consistently used condoms 100% of the time increased from 11% at baseline to 42% within the immediate post-intervention period. The effect was remarkably sustained, with approximately 36% of couples maintaining 100% compliance at 6 and 12 months. In the HP group, 100% consistent condom use increased from 14% at baseline to 27% immediately post-intervention, and also remained fairly stable at 6 and 12 months. The number of unprotected sex acts in "inconsistent" users also was significantly reduced in both intervention groups, although the reduction was similar between groups. The cumulative incidence of STDs did not significantly differ between groups over the 12-month period.

HIV seroconversion occurred in two persons in the Eban group and three persons in the HP group, giving an overall annual seroconversion rate for HIV-discordant couples in studies was 935 per 100,000. When compared to the general annual HIV seroconversion rate in the African-American community in the United States (about 84 per 100,000), the risk of HIV transmission within discordant couples, as demonstrated in this study, is still alarmingly high — despite whatever the intervention.

Transfusion-associated HIV

Source: CDC. HIV transmission through transfusion — Missouri and Colorado, 2008. MMWR. 2010;59: 1335-1339.

Estimates of the risk of hiv transmission from blood products in the United States are approximately 1 in 1.5 million. This translates into approximately 11 potential HIV+ donors and 20 contaminated blood products. Despite these risks, this report details the only case of documented transfusion-associated HIV transmission reported to the CDC since 2002.

A 40-year-old male who reported no risk factors for HIV infection, and was a regular blood donor (for no remuneration), donated blood in June and November 2008. His specimens in June tested HIV negative by EIA and by nucleic acid testing of mini-pooled plasma specimens, but the November donation tested positive. As per the Missouri Department of Health's protocol, the donation from June was re-examined and potential recipients of that donation identified.

Blood products from the donor went to two individuals, including an older man who died within two days of cardiac surgery; there were no specimens or tissues available to examine whether HIV could have been transmitted. The second patient had chronic renal failure on hemodialysis for several years, and received a single unit of fresh frozen plasma during kidney transplant surgery. He had last tested HIV negative three years earlier. By the time the recipient was identified, he had a negative HIV EIA, a plasma RNA viral load of 7,240, and a CD4 count of 48 cell/mm3. He was pre-emptively started on antiretroviral therapy and, by April, his EIA was positive and his CD4 had improved. Sequencing of the donor and recipient HIV DNA demonstrated > 99% similarity.

The (former) blood donor was married but admitted to casual and anonymous sex (both male and female), generally when intoxicated.

While the blood donation system for infectious screening is obviously effective, the weakest link is the failure of individuals, such as this man, to honorably acknowledge their own risky behaviors and refrain from putting others at risk. But if you are practiced in deception (and willingly place your wife and sexual partners at risk), how can we expect the safety of a stranger to matter?

Is There a Safer Stud?

Source: MedPage Today, January 10, 2011.

Investigators examined the risk of periodontal infection and longer-term consequences of tongue piercings in a randomly selected group of people (ages 16 to 26 years of age) who were getting their first tongue piercing. As reported in the Journal of Adolescent Health (Kapferer I, et al. Tongue piercing: The effect of material on microbiological findings. J Adolesc Health. 2011; e-pub), colony counts of 80 different bacteria were examined by DNA hyberidization methods in the oral cavities, tongues, and on the studs of 85 patients within two weeks of tongue piercing. The studs were either made of stainless steel, titanium, polytetrafluoroethylene, or polypropylene.

Concentrations of bacteria were significantly greater on the tongue, and especially in the stud tract in patients with tongue piercings. Unlike the usual gingival bacterial flora found in the oral cavity, 18 other types of bacteria were found at significantly higher colony counts on the tongues, and eight bacteria were more commonly found on the studs. Colony counts were significantly higher on the stainless steel studs than on other products, suggesting that bacteria could more effectively create biofilms with stainless steel studs.

Late complications of tongue piercing included recession of the tongue from around the stud in 29%, and in 5% had chipped teeth. No one developed gingivitis. Based on this data, tongue-piercers should consider the safety of different tongue studs.