Mycobacterium Bacteria

INTRODUCTION

Nature of the Bacteria

Mycobacterium tuberculosis (M. tuberculosis) is the bacterium that causes the disease tuberculosis (TB). A distinctive characteristic of the genus Mycobacteria is the presence of a thick lipid-rich cell wall and resistance to the decolourization step of the gram stain (being acid-fast). The acid-fast characteristic of the M. tuberculosis is the result of a waxy, lipid-rich cell wall. The cell envelope of the tubercle bacilli contains a layer beyond the peptidoglycan which is exceptionally rich in lipids, glycolipids and polysaccharides. The bacterium is gram positive bacillus which is an obligate aerobe, is non-motile, a non-endospore forming and is non-capsulated. The microscopic appearance of M. tuberculosis is seen as straight, slightly curved rods approximately 3 x 0.3µm in size. In liquid culture media, the bacteria usually grow as twisted rope-like pellets known as ‘serpentine cords’. M. tuberculosis is capable of growing on a wide range of enriched culture media such as Lowenstein-Jensen medium or Middlebrook medium. The optimum growth temperature of the pathogenic organsim is 35-37°C and unlike most other mycobacteria, it cannot grow at a temperature of 25°C or 41°C. M. tuberculosis is an airborne pathogen that is transmitted from person to person, usually infecting the respiratory tract through inhalation (Greenwood, et al., 2012).

Other key features of M. tuberculosis are its slow growth rate, dormancy, intracellular pathogenesis and genetic homogeneity. In infected animals or synthetic medium, M. tuberculosis has a generation time of about 24 hours. The short generation time contributes to the chronic nature of the tuberculosis disease and long treatment courses for infected patien...

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...ST. A person could show positive for LTBI, when in fact it is the vaccine causing the positive result. There are conflicting policies on the BCG vaccination both nationally and internationally due to the lack of effectiveness and potential loss of the TST (HSE/HSPC, 2010).

Healthcare workers working in close proximity with infected patients are required to take various standard precautions. These standard precautions include hand hygiene, wearing personal protective equipment, appropriate management of sharps and waste and appropriate decontamination of the working environment. For their own protection, a healthcare worker must assume that all blood, body fluids and secretions from patients are potentially hazardous and my cause infection. If the appropriate precautions are taken, healthcare workers can prevent becoming infected with TB themselves (HSE/HSPC, 2010).