Mycobacterium tuberculosis has infected more than two billion individuals worldwide, of whom 5%–10% have clinically active disease and 90%–95% remain in the latent stage with a reservoir of viable bacteria in the macrophages for extended periods of time. The tubercle bacilli at this stage are usually called dormant, non-viable, and/or non-culturable microorganisms. The patients with latent bacilli will not have clinical pictures and are not infectious. The infections in about 2%–23% of the patients with latent status become reactivated for various reasons such as cancer, human immunodeficiency virus infection, diabetes, and/or aging. Many studies have examined the mechanisms involved in the latent state of Mycobacterium and showed that latency modified the expression of many genes. Therefore, several mechanisms will change in this bacterium. Hence, this study aimed to briefly examine the genes involved in the latent state as well as the changes that are caused by Mycobacterium tuberculosis. The study also evaluated the relationship between the functions of these genes.

Objectives To investigate possible sources of Stenotrophomonas maltophilia (S. maltophilia) in the clinical environment. Methods Different samples were collected from Amol City of Iran. Steps for the identification of S. maltophilia included culturing, biochemical tests, polymerase chain reaction (PCR) of 16S rRNA gene and 23S rRNA gene. In addition, production of melanin pigment and patterns of motility of the bacteria, were also investigated. Results In our study, 20 S. maltophilia strains were isolated from clinical sources, oxygen manometer apparatus of hospitals were 7/110 (6.36%), blood was 1/777 (0.13%), sputum was 4/40 (4%), urine was 1/2 947 (0.03%), tap water was 1/240 (0.42%) and dental suction was 6/120 (5%). The isolated bacteria showed production of melanin pigment with rates of strong, moderate, weak, and lack of pigment. Types of motilities were seen in isolates. Conclusions The highest percentage of bacteria is isolated of oxygen manometer system and dental suction, yet has not been reported from oxygen manometer system. These bacteria have also been associated with patients who have respiratory problems, so it is essential for staffs of hospitals to draw attention to this source of bacteria.