Clostridium difficile most common cause of bacterial diarrhoea in HIV-positive patients

Clostridium difficile is the most common cause of bacterial diarrhoea in HIV-positive patients, according to an American study published in the December 1^st edition of Clinical Infectious Diseases. Investigators looked at trends in bacterial diarrhoea in a population of over 44,000 HIV-positive patients between 1992 and 2002. They also found that the risk of bacterial diarrhoea increased with HIV disease progression and that the incidence of bacterial diarrhoea has fallen since effective anti-HIV treatment became available.

“Diarrhoea occurs commonly among persons with HIV infection: the reported prevalence in developed countries ranges from 42% - 90%”, write the investigators. As well as meaning a lower quality of life, individuals who have progressed to AIDS have shorter survival if they have diarrhoea.

There have been no studies looking at the annual incidence of bacterial diarrhoea since effective HIV therapy became available, and there is little information on how the risk of diarrhoea varies according to the severity of HIV disease. Investigators from the Adult/Adolescent Spectrum of HIV Disease (ASD) Project therefore analysed annual incidence rates of bacterial diarrhoea in a population of over 44,000 HIV-positive individuals recruited from 100 healthcare facilities in nine areas. The investigators also determined the incidence of bacterial diarrhoea according to HIV disease stage (clinical AIDS; immunological AIDS; non-AIDS) and gathered data on the bacteria causing diarrhoea. Changes in rates of diarrhoea were examined between 1992 and 2002.

A total of 11,320 episodes of diarrhoeal illness were reported in the ten years of the study. However, only 1091 (10%) of these episodes had a confirmed bacterial cause and were included in the investigators’ analysis. The mean annual incidence of diarrhoea between 1992 and 2002 was 7 cases per 1000 patient years, which the investigators stressed “was at least 100-fold greater than bacterial diarrhoea rates reported in the general US population.”

Clostridium difficile was identified as the most common cause of bacterial diarrhoea, accounting for 54% of all cases. The next most common were Shigella (14%), Campylobacter (14%) and Salmonella (7%).

The investigators found that, amongst patients with clinical AIDS (AIDS diagnosed after a patient developed an opportunistic infection), the incidence of Clostridium difficile was 10 cases per 1000 patient years, twice that of other bacterial diarrhoea.

Although not statistically significant, the incidence of Clostridium difficile declined from 5 cases per 1000 patient years in 1992 to 3 cases per 1000 patient years in 2002. Amongst patients with clinical AIDS, the rate of Clostridium difficile fell by 60% between 1992 and 2002, a statistically significant decline.

Diarrhoea with other bacterial causes fell from 6 cases per 1000 patient years in 1992 to 2 cases per 1000 patient years in 2002. Once again, the most significant decrease was seen in patients with clinical AIDS, amongst whom the rate fell by 70%.

The investigators comment, “health care professionals should be aware that persons with HIV infection and progressing immunocompromise are at increased risk of developing Clostridium difficile and other bacterial diarrhoea.” They recommend, “when evaluating immunocompromised patients with diarrhoea health care professionals should have a heightened suspicion of Clostridium difficile.”

Basic health prevention measures such as hand washing, food preparation safety and “responsible pet ownership” should be emphasised to HIV-positive individuals, the investigators stress.