Microbiology - Bacteria 2 PDF

BACTERIA II. “ORDINARY” GRAM-POSITIVE BACTERIA General Characteristics 1. Stained dark blue or violet by Gram staining 2. Most have simple morphology 3. Some form heat-resistant endospores 4. Could occur singly, in pairs, or in chains, arranged in trichomes, or form branching hyphae...

BACTERIA II. “ORDINARY” GRAM-POSITIVE BACTERIA General Characteristics 1. Stained dark blue or violet by Gram staining 2. Most have simple morphology 3. Some form heat-resistant endospores 4. Could occur singly, in pairs, or in chains, arranged in trichomes, or form branching hyphae 5. Could be parasite or saprophytes 6. Some of the parasite organisms can be highly pathogenic for humans, animals or plants A. GRAM-POSITIVE COCCI 1. They possess cytochromes 2. They respire with oxygen 3. Some can obtain energy under anaerobic conditions by fermentation Common Species Micrococcus  Gram-positive spherical cells ranging from about 0.5 to 3 micrometers in diameter and are typically appear in tetrads  Micrococcus occurs in a wide range of environments, including water, dust, and soil  May be isolated from human skin, animal and dairy products, and beer; also found in many other places in the environment, including water, dust, and soil.  M. luteus on human skin transforms compounds in sweat into compounds with an unpleasant odor.  Can grow well in environments with little water or high salt concentrations. Most are mesophiles; some, like Micrococcus antarcticus (found in Antarctica) are psychrophiles  Generally saprotrophic or commensal organism; can be an opportunistic pathogen, may be involved in other infections, including recurrent bacteremia, septic shock, septic arthritis, endocarditis, meningitis, and cavitating pneumonia (immunosuppressed patients).  Industrial uses o Actinobacteria, can be catabolically versatile, with the ability to utilize a wide range of unusual substrates, such as pyridine, herbicides, chlorinated biphenyls, and oil. o They are likely involved in detoxification or biodegradation of many other environmental pollutants. o Other Micrococcus isolates produce various useful products, such as long-chain aliphatic hydrocarbons for lubricating oils Staphylococcus – nonmotile, facultatively anaerobic, parasites; occurs in the skin and mucous membranes of humans and animals, relatively resistant to drying, heat (they can withstand 50oC for 30 minutes. S. aureus - frequently found as part of the normal skin flora on the skin and nasal passages; estimated that 20% of the human population are long-term carriers of S. aureus - a pathogen due to production of carotenoid pigment, staphyloxanthin, being a bacterial antioxidant which helps the microbe evade the hosts immune system in the form of 1  reactive oxygen species which the host uses to kill pathogens - Cause illnesses from minor skin infections, such as pimples, impetigo, boils (furuncles), cellulitis folliculitis, carbuncles, scalded skin syndrome, and abscesses, to life-threatening diseases such as pneumonia, meningitis, osteomyelitis, endocarditis, toxic shock syndrome (TSS), bacteremia, and sepsis - Toxins: (a) staphylococcal enterotoxin causes a form of food poisoning characterized by vomiting and diarrhea one to six hours after ingestion of the toxin (b) Exfoliative toxin causes staphylococcal scalded-skin syndrome with peeling of the skin especially among infants, (c) bicomponent toxins may cause severe necrotizing pneumonia in children S. epidermidis - Part of human skin flora; not usually pathogenic; causes biofilms to grow on plastic devices placed within the body like intravenous catheters and on medical prostheses; causes wound infections and Endocarditis. S. saprophyliticus - Part of human skin flora; causes urinary tract infection Streptococcus – arranged in chains, most are parasites of humans and animals S. pneumoniae - Major cause of pneumonia, also acute sinusitis, otitis media, meningitis, bacteremia, sepsis, osteomyelitis, septic arthritis, endocarditis, peritonitis, pericarditis, cellulitis, and brain abscess S. pyogenes - is the most clinically important species of streptococcus; it causes streptococcal sore throat, scarlet fever and rheumatic fever S. faecalis (enterococcus) - occurs normally in the intestinal tracts of humans and animals, can be opportunistic pathogen, cause urinary tract infection S. mutans - inhabits the human oral cavity and is the major causative agent of dental carries S. lactis and subsp. S. cremoris - cocci n pairs and short chains, nonsporulating, nonmotile - harmless contaminants of milk and dairy products, they cause rapid souring and curdling of milk; used as starter cultures for the manufacturer of butter, buttermilk, cheese, because of the flavor they produce - have a homofermentative metabolism and have been reported to produce exclusively lactic acid - L. lactis is one of the most important microorganisms in the dairy industry; crucial importance for manufacturing dairy products, such as buttermilk and cheeses; the bacterium uses enzymes to produce energy molecules ATP, from lactose; lactic acid produced by the bacterium curdles the milk that then separates to form curds, which are 2  used to produce cheese bacterium include the production of pickled vegetables, beer or wine, some breads, and other fermented foodstuffs, such as soymilk kefir, buttermilk - first genetically modified organism to be used alive for the treatment of human disease Leuconostocs - ovoid cocci often forming chain; gram-positive chemoorganoheterotrophic bacteria; facultative anaerobe found in mesophilic mixed-strain cultures but not in thermophilic starter cultures - harmless saprophytes, usually nonpathogenic acid-tolerant organisms with optimal temperature 18 and 25°C but some species are also capable of causing human infection - traditionally found in association with plant matter, found in the wild and is a part of the natural microflora in almost all farming fields - found in many different processed foods (in sugar processing liquors and fermented foods, including olives, cucumbers, sauerkraut, wine, cheese, milk dairy products, and meats ), either as a starter culture or as a contaminant. Leuconostoc requires rich, complex media (nicotinic acid, thiamin, biotin, and pantothenic acid or one of its derivatives and has the ability to produce lactic acid and diacetyl. - Leuconostoc in general is important to fermentation of vegetables; Causes “stink” when creating a sourdough starter; along with other lactic acid bacteria they ferment cabbage, making it sauerkraut. In this process the sugars in fresh cabbage are transformed to lactic acids which give it a sour flavor and good keeping qualities - Used as “starter culture” for the manufacture of buttermilk and cheese because of the flavor they produce. L. carnosum - is an anaerobic bacterium found in spoiled, packaged meat; also produces bacteriocins, and these are used to inhibit and meat products - Able to inhibit growth of other (even closely related) bacteria e.g. Listeria monosytogenes, thus, it may be used as biopreservative. Leuconstoc mesenteroides - Used primarily in sauerkraut production, where its heterofermentative abilities are used in the first stage of four to convert glucose and fructose in cabbage to lactic acid, mannitol, acetic acid, ethanol, and carbon dioxide. In fermented milk and meat products, diacetyl is responsible for butter flavor and the other fermentation products aid in the preservation and palatability of the food. B. ENDOSPORE-FORMING GRAM-POSITIVE BACTERIA 1. Most are rod-shaped, some are cocci 2. Motility is by peritrichous flagella Bacillus - Gram-positive, rod-shaped bacteria, can be obligate aerobes or facultative anaerobes, Ubiquitous in nature - free-living and pathogenic species 3 - Under stressful environmental conditions, the cells produce oval endospores that can stay dormant for extended periods - Many Bacillus species are able to secrete large quantities of enzymes. Bacillus subtilis - rod-shaped, and has the ability to form a tough, protective endospore, allowing the organism to tolerate extreme environmental conditions such as heat, acid, and salt - not a human pathogen, may contaminate food but rarely causes food poisoning - responsible for causing ropiness — a sticky, stringy consistency caused by bacterial production of long-chain polysaccharides — in spoiled bread dough - Enzymes produced by B. subtilis and B. licheniformis are widely used as additives in laundry detergents. - subtilis strain QST 713 (marketed as QST 713 or Serenade) has a natural fungicidal activity, and is employed as a biological control agent. - can convert (decompose) some explosives into harmless compounds of nitrogen, carbon dioxide, and water Bacillus cereus - an endemic, soil-dwelling, endospore-forming Gram-positive, rod-shaped bacterium - Foodborne diseases  Some strains are harmful to humans and cause foodborne illness: cause of “Fried Rice Syndrome” as the bacteria is classically contracted from fried rice dishes that have been sitting at room temperature for hours (such as at a buffet)  causes severe nausea, vomiting and diarrhea  improperly cooked food may cause survival of the bacterial endospores then improperly refrigerated, allowing the endospores to germinate  Cooking temperatures less than or equal to 100 °C (212 °F) allows some B. cereus spores to survive  Germination and growth generally occurs between 10–50 °C (50–122 °F)  Bacterial growth results in production of enterotoxins, one of which is highly resistant to heat and to pH between 2 and 11; ingestion leads to two types of illness, diarrheal and emetic (vomiting) syndrome - Skin infections  also known to cause chronic skin infections that are difficult to eradicate  can cause keratitis - Beneficial strains  Other strains can be beneficial as probiotic feed additive for animals to reduce Salmonella in the intestines and cecum to improve the animals’ growth as well as food safety for humans who eat their meat  They compete with other microorganisms such as Salmonella and Campylobacter in the gut animals such as chickens, rabbits and pigs 4 Bacillus stearothermophilus - Gram-positive thermopile that is widely distributed in soil, hot springs, ocean sediment, and is a cause of spoilage in food products, e.g. canned goods - grow within a temperature range of 30-45 oC (minimum) and 65-75oC (maximum) - Used as a challenge organism for sterilization validation studies  Biological indicator contains spores of the organism on filter paper inside a vial.  After sterilizing, the cap is closed; A color and/or turbidity change indicates the results of the sterilization process; no change indicates that the sterilization conditions were achieved, otherwise the growth of the spores indicates that the sterilization process has not been met.  Biological indicators are used in conjunction with chemical indicators and process indicators to validate sterilization processes Bacillus polymyxa - has the ability to fix nitrogen under anaerobic conditions - Biological nitrogen fixation  Process which nitrogen (N2) in the atmosphere is converted into ammonia (NH3). This process is essential for life because fixed nitrogen is required to biosynthesize the basic building blocks of life, e.g., nucleotides for DNA and RNA and amino acids for proteins. Nitrogen fixation also refers to other biological conversions of nitrogen, such as their conversions to nitrogen dioxide. Microorganisms that fix nitrogen are bacteria called diazotrophs.  occurs when atmospheric nitrogen is converted to ammonia by an enzyme called nitrogenase. The reaction for BNF is: N2 + 8 H+ + 8 e− → 2 NH3 + H2 The process is coupled to the hydrolysis of 16 equivalents of ATP and is accompanied by the co-formation of one molecule of H2. Bacillus thuringiensis - Soil-dwelling bacterium; also occurs naturally in the gut of caterpillars of various types of moths and butterflies, as well as on the dark surface of plants - commonly used as a biological pesticide  The Cry toxin may be extracted and used as an insecticide. During sporulation, many Bt strains produce crystal proteins called δ-endotoxins that have insecticidal action.  Cry toxins have specific activities against insect species of the orders Lepidoptera (moths and butterflies), Diptera (flies and mosquitoes), Coleoptera (beetles), Hymenoptera (wasps, bees, ants and sawflies) and nematodes  Because of their specificity, these pesticides are regarded as environmentally friendly, with little or no effect on humans, wildlife, pollinators, and most other beneficial insects  B. thuringiensis-based insecticides are often applied as liquid sprays on crop plants, where the insecticide must be ingested to be effective. The solubilized toxins are thought to form pores in the midgut epithelium of susceptible larvae 5   Bacillus thuringiensis israelensis (Bti) is a naturally occurring soil bacterium that can effectively kill mosquito larvae present in water - Used genetically modified crops using Bt genes.  genetically engineered (tobacco) plants with insect tolerance by expressing cry genes from B. thuringiensis  Genetically modified maize (corn) has been deliberately genetically modified (GM) to have agronomically desirable traits o resistance to herbicides o resistance to insect pests by incorporation of a gene that codes for the B. thuringiensis (Bt) toxin o This gene codes for a toxin that causes the formation of pores in the Lepidoptera larval digestive tract. These pores allow naturally occurring enteric bacteria, such as E. coli and Enterobacter, to enter the hemocoel, where they multiply and cause sepsis. Bacillus anthracis - Pathogen of the Anthrax acute disease; Gram-positive, spore-forming, rod-shaped - It can be grown in an ordinary nutrient medium under aerobic or anaerobic conditions - Bacillus anthracis spores in particular are highly resilient, surviving extremes of temperature, low-nutrient environments, and harsh chemical treatment over decades or centuries, and create toxins that cause edema on the host - B. anthracis must acquire iron in order to grow and proliferate in its host environment. The most readily available iron sources for pathogenic bacteria are hemoglobin used by the host in the transport of oxygen - Anthrax  Bacillus anthracis can form dormant endospores  When spores are inhaled, ingested, or come into contact with a skin lesion on a host they may reactivate and multiply rapidly.  Spores can be transported by clothing or shoes.  Occupational exposure to infected animals or their products (such as skin, wool, and meat) is the usual pathway of exposure for humans. Workers who are exposed to dead animals and animal products (e.g. wool) are at the highest risk  Respiratory infection in humans initially presents with cold or flu-like symptoms for several days, followed by severe (and often fatal) respiratory collapse  Gastrointestinal infection in humans is most often caused by eating anthrax-infected meat and is characterized by serious gastrointestinal difficulty, vomiting of blood, severe diarrhea, acute inflammation of the intestinal tract, and loss of appetite  Cutaneous (on the skin) anthrax infection in humans shows up as a boil-like skin lesion that eventually forms an ulcer with a black center  If a person is suspected as having died from anthrax, every precaution should be taken to avoid skin contact with the potentially contaminated body and fluids exuded through natural body openings. The body should be put in strict quarantine. 6 Listeria Listeria monocytogenes - A facultative anaerobe, intracellular bacterium, is the causative agent of listeriosis. It is one of the most virulent foodborne pathogens, with 20 to 30 percent of clinical infections resulting in death with fatality rates exceeding even Salmonella and Clostridium botulinum - It is the third-most-common cause of meningitis in newborns. - Gastrointestinal symptoms, such as nausea, vomiting, and diarrhea, may precede more serious forms of listeriosis or may be the only symptoms expressed.  The onset time to gastrointestinal symptoms is unknown but probably exceeds 12 hours.  Contracted through raw or supposedly pasteurized milk,  Once the bacterium enters the host’s monocytes, macrophages, or polymorphonuclear leukocytes, it becomes blood-borne (septicemia) and can grow - L. monocytogenes has been associated with such foods as raw milk, pasteurized fluid milk, cheeses (particularly soft-ripened varieties), ice cream, raw vegetables, fermented raw-meat sausages, raw and cooked poultry, raw meats (of all types), and raw and smoked fish. Its ability to grow at temperatures as low as 0°C permits multiplication in refrigerated foods. At refrigeration temperature, such as 4°C, the amount of ferric iron can affect the growth of L. monocytogenes. - L. monocytogenes from soil, silage, and other environmental sources; quite hardy and resists the deleterious effects of freezing, drying, and heat remarkably well for a bacterium that does not form spores Clostridium - Gram-positive, endospores-forming rod-shaped obligate anaerobes. - include common free-living bacteria as well as important pathogens Industrial Uses - C. thermocellum can utilize lignocellulosic waste and generate ethanol, thus making it a possible candidate for use in production of ethanol fuel. It also has no oxygen requirement and is thermophilic, which reduces cooling cost. - C. acetobutylicum used to produce acetone and biobutanol from starch for the production of gunpowder and TNT. - C. botulinum produces a potentially lethal neurotoxin that is used in a diluted form in the drug Botox, which is carefully injected to nerves in the face, which prevents the movement of the expressive muscles of the forehead, to delay the wrinkling effect of ageing. - C. ljungdahlii, recently discovered in commercial chicken wastes, can produce ethanol from single-carbon sources including synthesis gas, a mixture of carbon monoxide and hydrogen that can be generated from the partial combustion of either fossil fuels or biomass. - Fatty acids are converted by yeasts to long-chain dicarboxylic acids and then to 1,3- propanediol using Clostridium diolis - Non-pathogenic strains of Clostridium may help in the treatment of diseases such as cancer. Research shows that Clostridium can selectively target cancer cells. Some strains can enter and replicate within solid tumors. Clostridium could, therefore, be used to deliver therapeutic proteins to tumors. Clostridium botulinum - anaerobic (oxygen is poisonous to the cells) rod-shaped spore-former, which produces oval, subterminal endospores and is commonly found in soil 7 - in an anaerobic environment it produces the neurotoxin during sporulation - Produces neurotoxins that cause the flaccid muscular paralysis; the main paralytic agent in Botox Botulism - Botulism poisoning can occur due to improperly preserved or home-canned, low-acid food that was not processed using correct preservation times and/or pressure - The ability of C. botulinum to naturally transfer neurotoxin genes to other clostridia is concerning, especially in the food industry where preservation systems are designed to destroy or inhibit only C. botulinum but not other Clostridium species. - Botulin toxin produced by C. botulinum is often believed to be a potential bioweapon as it is so potent that it takes about 75 nanograms to kill a person (LD50 of 1 ng/kg; 500 grams of it would be enough to kill half of the entire human population. - Paralysis that typically starts with the muscles of the face and then spreads towards the limbs. In severe forms, it leads to paralysis of the breathing muscles and causes respiratory failure. - Food borne botulism results from contaminated foodstuffs in which C. botulinum spores have been allowed to germinate in anaerobic conditions. This typically occurs in home- canned food substances and fermented uncooked dishes. Given that multiple people often consume food from the same source, it is common for more than a single person to be affected simultaneously - Botulism can be prevented by killing the spores by pressure cooking or autoclaving at 121 °C (250 °F) for 3 minutes or providing conditions that prevent the spores from growing. The toxin itself is destroyed by normal cooking processes - that is, boiling for a few minutes. - Additional precautions for infants include not feeding them honey Environmental characteristics - Clostridium botulinum is a soil bacterium. The spores can survive in most environments and are very hard to kill. They can survive the temperature of boiling water at sea level, thus many foods are canned with a pressurized boil that achieves an even higher temperature, sufficient to kill the spores. - Growth of the bacterium can be prevented by high acidity, high ratio of dissolved sugar, high levels of oxygen, very low levels of moisture or storage at temperatures below 3°C (38°F) for type A. For example in a low acid, canned vegetable such as green beans that are not heated hot enough to kill the spores (i.e., a pressurized environment) may provide an oxygen free medium for the spores to grow and produce the toxin. On the other hand, pickles are sufficiently acidic to prevent growth; even if the spores are present, they pose no danger to the consumer. Honey, corn syrup, and other sweeteners may contain spores but the spores cannot grow in a highly concentrated sugar solution; however, when a sweetener is diluted in the low oxygen, low acid digestive system of an infant, the spores can grow and produce toxin. As soon as infants begin eating solid food, the digestive juices become too acidic for the bacterium to grow. Clostridium difficile - anaerobic, spore-forming rods (bacilli) Antibiotic-Associated Diarrhea (AAD) - Causes severe diarrhea and other intestinal disease when competing bacteria in the gut flora have been wiped out by antibiotics. Can lead to pseudomembranous colitis, a severe infection of the colon 8  - C. difficile bacteria naturally reside in the gut or accidentally ingested spores hospital, nursing home, or similar facility. When the normal gut flora has been destroyed with broad- spectrum antibiotic such as clindamycin, the gut becomes overrun with C. difficile. This overpopulation is harmful because the bacteria release toxins that can cause bloating and diarrhea, with abdominal infection Control measures - Wearing gloves when caring for patients. - washing with soap and water will eliminate the spores from contaminated hands, - Alcohol-based hand rubs are ineffective - Bleach wipes containing 0.55 percent sodium hypochlorite have been shown to kill the spores and prevent transmission between patients. - Hydrogen peroxide vapor to sterilize a patient room post Clostridium perfringens - is a Gram-positive, rod-shaped, anaerobic, spore-forming bacterium of the genus - C. perfringens is ever present in nature and can be found as a normal component of decaying vegetation, marine sediment, the intestinal tract of humans and other vertebrates, insects, and soil. Food poisoning - Due to poorly prepared meat and poultry caused by Clostridium perfringens enterotoxin - Incubation time is between six and 24 (commonly 10-12) hours - Often, meat is well prepared, but too far in advance of consumption. Since C. perfringens forms spores that can withstand cooking temperatures, if let stand for long enough, germination ensues and infective bacterial colonies develop. Symptoms typically include abdominal cramping and diarrhea - Many cases of C. perfringens food poisoning likely remain subclinical, as antibodies to the toxin are common among the population. Commercial Use - Clostridium perfringens is the main rising agent in salt rising bread in which the main rising agent is a bacterium Clostridium perfringens, which leavens the bread along with lactobacillus and other wild microbes, as opposed to mainly yeast or baking soda Clostridium tetani - Gram-positive rod-shaped, obligate anaerobic bacterium (cannot survive in the presence of oxygen), is heat-sensitive, antiseptic-resistant and exhibits flagellar motility - Its appearance on a gram stain resembles tennis rackets or drumsticks - C. tetani is found as spores in soil or in the gastrointestinal tract (manure) of animals. C. tetani produces a potent biological toxin, tetanospasmin, and is the causative agent of tetanus, a disease characterized by painful muscular spasms that can lead to respiratory failure and, in up to 40% of cases, death. 9  Vaccination - Tetanus can be prevented through the highly effective tetanus vaccine, which is an attenuated tetanus toxin inactivated with formaldehyde to be immunogenic but not pathogenic Pathogenecity - C. tetani usually enters a host through a wound to the skin and then it replicates. Once an infection is established, C. tetani produces exotoxins which are neurotoxin that causes the clinical manifestations of tetanus. - Released in the wound is absorbed into the circulation and reaches ends of motor nerves all over the body. The toxin acts at several sites within the central nervous system including peripheral nerve terminals, the spinal cord, and brain, and within the sympathetic nervous system - Symptoms: Lockjaw, facial spasms, stiffness of the neck, difficulty in swallowing, and rigidity of pectoral and calf muscles. Other symptoms: elevated temperature, sweating, elevated blood pressure, and episodic rapid heart rate. Spasms may occur frequently and last for several minutes with the body shaped into a characteristic form called opisthotonos. Spasms continue for up to 4 weeks, and complete recovery may take months. - Tetanus is often associated with rust, especially rusty nails, but this concept is somewhat misleading. Objects that accumulate rust are often found outdoors, or in places that harbor anaerobic bacteria, but the rust itself does not cause tetanus nor does it contain more C. tetani bacteria. The rough surface of rusty metal merely provides a prime habitat for a C. tetani endospore to reside, and the nail affords a means to puncture skin and deliver endospores into the wound. Corynebacterium diphtheriae - Facultative anaerobicGram-positive, highly pleomorphic organisms with no particular arrangement. Diphtheria - an upper respiratory tract illness caused by Corynebacterium diphtheriae, - characterized by sore throat, low fever, and an adherent membrane (a pseudomembrane) on the tonsils, pharynx, and/or nasal cavity. - A milder form of diphtheria can be restricted to the skin. Less common consequences include myocarditis and peripheral neuropathy - Diphtheria is a contagious disease spread by direct physical contact or breathing the aerosolized secretions of infected individuals. Propionibacterium acnes - aerotolerant anaerobic gram positive bacterium (rod) that is linked to the skin condition acne; - This bacterium is largely commensal and part of the skin flora present on most healthy adult human skin. - It is usually just barely detectable on the skin of healthy pre-adolescents. It lives primarily on, amongst other things, fatty acids in the sebaceous glands on sebum secreted by follicles. It may also be found throughout the gastrointestinal tract in humans and many other animals. It is named after its ability to generate propionic acid 10  - When a pore is blocked, this anaerobic bacterium overgrows and secretes chemicals that break down the wall of the pore and forming an acne lesion (folliculitis), possibly spilling bacteria such as Staphylococcus aureus into the broken skin - Moderate to severe Acne vulgaris appears to be more often associated with virulent sub- strains Mycobacterium tuberculosis (MTB) - is a pathogenic bacteria and the causative agent of most cases of tuberculosis (TB) - M. tuberculosis has an unusual, waxy coating on its cell surface which makes the cells impervious to Gram staining, so acid-fast detection techniques are used, instead. - It is a small bacillus that can withstand weak disinfectants and can survive in a dry state for weeks. Its unusual cell wall, rich in lipids (e.g., mycolic acid), is likely responsible for this resistance and is a key virulence factor. - When in the lungs, M. tuberculosis is taken up by alveolar macrophages, but they are unable to digest the bacterium. The bacteria also evade macrophage-killing by neutralizing reactive nitrogen intermediates - Only an estimated 10% of people infected with M. tuberculosis ever develop the disease, and many of those have the disease only for the first few years following infection, even though the bacillus may lie dormant in the body for decades - The symptoms that patients infected with M. tuberculosis may experience are usually absent until the disease has become more complicated. It may take many months from the time the infection initially gets into the lungs until symptoms develop. A cough is, however, the first symptom of the infection with M. tuberculosis. The initial symptoms, including loss of appetite, fever, productive cough and loss of energy or loss of weight or night sweats, are not specific and might be easily attributed to another condition. Mycobacterium leprae - aerobic bacillus (rod-shaped) surrounded by the characteristic waxy coating unique to mycobacteria causes leprosy (Hansen's disease) - It is an intracellular, pleomorphic, acid-fast bacterium - M. leprae is an. In size and shape, it closely resembles Mycobacterium tuberculosis. Due to its thick waxy coating, M. leprae stains with a carbol fuscin rather than with the traditional Gram stain. The culture takes several weeks to mature. 11