MICROBIOLOGY

Microbiology



Abstract

Today, it is understood that AIDS is caused by the human immunodeficiency virus (HIV), a retrovirus that attacks the cells of the immune system and is transmitted through direct contact at the mucus membrane or the bloodstream with HIV-infected body fluids such as blood, semen, vaginal fluid, and breast milk. The three major modes of transmission for HIV are sexual contact with an HIV-positive individual, exposure to infected bodily fluids such as through injection drug use or blood transfusions, and mother-to-child transmissions. Although saliva does contain trace amounts of HIV, it is now understood that infection from saliva is virtually impossible. eliminate the risk of transmission. Although HIV transmission from blood transfusions is extremely low in the developed world, the World Health Organization (WHO) estimates that much of the world does not have access to a safe, uncontaminated blood supply. As such, HIV transmission from blood transfusions accounts for up to 10% of new HIV infections worldwide each year. For injection drug users, not sharing needles and other drug paraphernalia can lead to decreased risk of HIV transmission. The risk of transmission during pregnancy, labor, and delivery can be reduced from 25% to less than 1% by antiretro-viral therapy and caesarean childbirth.

Microbiology

Introduction

HIV is a virus that is found most predominantly in body fluids containing white blood cells (e.g., blood, semen, breast milk, and cervical/vaginal secretions). HIV is most often transmitted when one of these body fluids from an infected person enters the blood system of an uninfected person through an opening in the body. HIV transmission most often occurs through sexual intercourse, sharing infected injection equipment involved in illicit drug use, breast-feeding, or transfusion of untested blood products, which does not occur in the developed world. Prevention of HIV infection generally involves modification of behaviors related to these modes of transmission.

Bacteria and HIV

Helicobacter pylori is a bacterium that has proved to have both protective and causative effects in relation to cancer. H. pylori infection has a protective effect against Barrett's esophagus, a precursor for adenocarcinoma of the esophagus. It has also been implicated for its role in the precancer process (i.e., chronic gastritis) associated with stomach cancer—more specifically, gastric adenocarcinoma and gastric MALT lymphoma.

H. pylori has the ability to damage the mucous barrier, making it more vulnerable to carcinogens. Furthermore, it can increase the rate of proliferation of the gastric epithelium. Nevertheless, H. pylori is not the only risk factor for stomach cancer; factors such as diet and tobacco smoking (among others) also play important roles. H. pylori infection is known to be acquired in childhood; those who have been infected usually do not have any symptoms until later in life.

H. pylori is believed to be transmitted orally in two ways. The first is through the ingestion of food or water that has been contaminated with fecal matter. The second is through oral contact (i.e., kissing, drinking from the same cup/bottle, etc.). In light of this, it is not unusual that the risk of ...