Micro special topics 2

Explain the causes of diphtheria, symptoms, and treatment options.

• caused by Corynebacterium diphtheriae, a gram-positive bacterium.​

• Symptoms include a sore throat, fever, and the formation of a grayish membrane in the throat.​

• Diphtheria exotoxin is an A-B toxin that interferes with protein synthesis, and is fatal in very small quantities.​

• The vaccine for diphtheria is a toxoid, designed to provoke the formation of antitoxins against diphtheria toxin.​

Describe the symptoms of the common cold, causative microbes, methods of transmission, and treatment options

• caused by over 200 different viruses, Rhinoviruses (Picornaviridae) and coronaviruses (Coronaviridae) are the most common viruses responsible.​

• Transmission occurs through direct contact or droplet transmission.​

• Treatment is primarily symptom-based, until the immune system fights off the infection.​

Describe tuberculosis, including its symptoms, causative microbes, methods of transmission, and treatment options

• caused by Mycobacterium tuberculosis.

• Symptoms include coughing (often with blood-stained sputum), fever, weight loss, and fatigue.​

• The disease is named for the tubercules, or lump-like lesions, that form as the body isolates the pathogens. ​

• Treatment involves the use of multiple antibiotics.​

pulmonary tuberculosis

tuberculosis cases remaining in the lungs

military tuberculosis

cases end up infecting other tissues

tubercle

lump-like lesions, that form as the body isolates the pathogens. ​

Explain the five-step process of tubercle formation and rupture, resulting in the release of bacteria to infect other regions

M. tuberculosis prevents digestion after ingestion by phagocytes.​

• They interfere with lysosome attachment to the phagosome, and acidification of the phagosome.​

• The bacteria emerge after killing the phagocytes into the center of the tubercle.​

• The lack of oxygen may be sufficient to arrest growth.​

• Introduction of air into the tubercle may result in rupture of the tubercle, releasing the microbes to infect other regions.​

List the four first-line drugs used in treating tuberculosis, and describe their mechanisms of action.

isoniazid, ethambutol, pyrazinamide, and rifampin (aka rifampicin)

List and provide an example for each of the six second-line drug categories used in treating tuberculosis.

• Aminoglycosides (amikacin, kanamycin)​

• Cyclic polypeptides (capreomycin)​

• Fluoroquinolones (ciprofloxacin)​

• Thioamides (ethionamide)​

• Serine analogs (cycloserine)​

• Salicylic acid derivatives (para-aminosalicylic acid)​

Multi-drug-resistant (MDR) tuberculosis strains

defined as being resistant to isoniazid and rifampin, the two most used first-line drugs.​

Extensively drug-resistant (XDR) tuberculosis strains

are defined as MDR strains also resistant to fluoroquinolones and either amikacin, capreomycin, or kanamycin.​

Totally drug-resistant (TDR) strains of tuberculosis

are resistant to most known antibiotics, and were first observed in 2003.​

Explain the causes of typhoid fever, symptoms, and treatment options.

• caused by Salmonella typhi, one of the most virulent serotypes of Salmonella enterica.​

• Symptoms include high fever, headache, and diarrhea.​

• Severe symptoms include encephalitis, perforation of the intestines, and neuropsychiatric episodes.​

• Vaccines against typhoid fever are available, but requires regular boosters to maintain immunity.​

• Many antibiotics are effective against typhoid fever, but multiple resistant strains have developed.​

Explain the causes of cholera, symptoms, and treatment options.

• Vibrio cholerae, a gram-negative bacterium with the typical curved-rod shape.​

• The disease is caused by cholera toxin, an A-B exotoxin that stimulates the release of water and electrolytes by host cells.​

• Treatment is primarily based on replenishment of lost fluids, though several antibiotics are effective.​

Explain how Helicobacter pylori may act to induce peptic ulcers and increased rates of gastric cancer, including a review of its mechanism of pathogenesis and current treatment options.

To defend against the low pH of the stomach, H. pylori produces large amounts of urease.​

• The ammonia neutralizes the HCl, creating a local high-pH region around the bacteria.

Some H. pylori also seek to escape the low pH by burrowing into the mucus layer protecting the stomach endothelium.​

• Adherins produces by the bacteria allow for attachment to the epithelial cells.​

• Ammonia production irritates the cells, causing inflammation and cessation of mucus production.​

• The resultant acid damage to the endothelium results in peptic ulcers, and increases the risk of gastric cancers.

Treatment regimens are often multi-faceted, and include several of all of the following:​

• Proton pump inhibitors​

• Antibiotics​

• Anti-inflammatory drugs​

• Probiotics (specifically lactic acid and butyrate producers)​

Describe hepatitis, including its variations, symptoms, and causative microbes.

• inflammation of the liver, and can be caused by at least five different viruses.​

• Acute hepatitis is often subclinical, but can result in fever, nausea, and abdominal distress.​ Severe cases result in liver damage.

• Chronic hepatitis may also be subclinical, but is often more likely to result in progressive liver damage, cirrhosis, or hepatic cancer.​ Only hepatitis B, C, and D can become chronic.​

• Hep A: Hepatovirus A (family: Picornaviridae)

• Hep B: Hepatitis B (family: Hepadnaviridae)

• Hep C:Hepacivirus C (family: Flaviviridae)

• Hep D: Hepatitus delta virus (family: Incertae sedis)

• Hep E: Orthohepevirus A (family: Hepeviridae)

bioremediation

the use of microbes to detoxify or degrade pollutants.​

bioaugmentation

the addition of specialized microbes to a contaminated area.​

• involve the breakdown of petroleum products or other organic material.​

mycoremediation

the specific use of fungi for bioremediation.​

bioleaching

is the extraction of metals using microbes.​

Explain how Thiobacillus ferrooxidans is used to facilitate mining procedures.

commonly used for the removal of metals through oxidation.

Describe the processes involved in drinking water treatment and sewage treatment.

• requires removal of particulate matter, along with potential contaminating chemicals, organic substances, microbes and cysts.​

• After settling and flocculation, the water is filtered, chlorinated, and irradiated.​

primary treatment in sewage treatment

similar to drinking water treatment, involving settling and removal of particulate matter.​

secondary treatment in sewage treatment

The primary sludge and effluent are separated, and sent to different treatment regions to undergo secondary treatment.​

• Aerobic sewage-metabolizing microbes acts on the effluent within activated sludge systems, trickling filters, or rotating biological contactors.​

• A steady supply of air results in the removal of most organic matter from the effluent, and the precipitation of secondary sludge.​

• The clear effluent is disinfected, and released.​

tertiary treatment in sewage treatment

In many regions, the effluent may undergo tertiary treatment, or further filtration, chemical treatment, and irradiation to render the water safe for human consumption

• primary and secondary sludge are sent to anaerobic sludge digesters.​

• Unlike effluent, anaerobic microbes are used to consume organic matter in the production of methane and water.​

• The remaining solid organic matter is dried, and used as landfill or soil conditioner.​

industrial fermentation

defined as the large-scale cultivation of microbes to produce commercially valuable substances.

bioreactor

microbes reside in vessels

• designed to agitate, nourish, and maintain specific environmental conditions for the microbes to produce the desired substances.​

batch production

Periodic collection of the substances is called batch production,

continuous flow production

materials are processed without interruption, flowing through a linear process on autopilot

Primary metabolites

generated when the microbes are in logarithmic phase

Secondary metabolites

usually generated only when the microbes have entered stationary phase.​

• The secondary metabolites may be modified versions of primary metabolites, or new substances entirely.​

Explain how potential sources of food contamination may occur in spite of proper commercial sterilization

Contamination of mesophilic bacteria is usually caused by underprocessed food or compromised can integrity.

Aseptic packaging

• generally sterilized by hydrogen peroxide and irradiation, then filled with previously sterilized foods or liquids.​

pascalization

• Pre-packaged foods may be subject to high-pressure treatment through submerging into tanks of pressurized water.​