Unit 3 PHM

What are the main mechanisms of action for antibiotics? What might each class of drugs target within a cell?

- Inhibit cell wall synthesis -inhibit protein synthesis -metabolic antagonist -Nucleic acid synthesis inhibitor

What are some resistance mechanisms that microbes can use to evade antibiotic action?

-Prevent drug entry -Pump drug out -Inactivate drug -modify target -usage of alternate pathway

What problems are associated with S. aureus carriers?

25-35% of population are carriers. About 2 percent are carriers of MRSA. As long as carriers are healthy, they dont have infection. But if carriers become immunocompromised, they can infect themselves.

How many polio virus serotypes cause human disease?

3. P1,P2, and P3.

How common in EBV infection?

90% of people show evidence of current of past infection of EBV by the time they are 60.

What are the symptoms associated with infection with the polio virus?

95% of people are asymptomatic. 4% have mild flu like symptoms. 1% of people get paralysis.

How is leprosy transmitted?

95% of world's population is not susceptible. Droplet transmission.

How are community acquired C. difficile infections possibly spread?

Asymptomatic carriers like infants. Doctors offices/waiting rooms. Food and water supply like meats and vegetables.

Why is recurrence thought to be such a big problem for C. difficile infections?

Because antibiotics are both a risk factor and a treatment.

Compare and contrast chickenpox and shingles.

Chickenpox - Extremely contagious. Droplet or viral particle transmission. Shingles - caused by dormant Varicella Zoster infection. Not contagious.

What is the connection between chickenpox and lollipops?

Chickenpox parties are a common practice, where parents knowingly infect their children with the Varicella Zoster virus. A woman sold infected lollipops for other children to eat.

How is HIV infection diagnosed?What are some pros and cons to in home testing?

Detect antibodies for the virus, and viral proteins and genes. Pros - people will know they have HIV infection, and get treatment, without stigma. Cons - potential for false negatives, not a diagnosis you should get alone at home.

What is the connection between EBV and cancer?

EBV is thought to get into certain immune cells. As cells replicate, EBV does to. Disrupts the cell growth regulators allowing uncontrolled cell replication. -Lymphomas. In China - nasopharyngeal cancers In Eastern Europe - Gastric Cancers host factors - organ transplants, and HIV patients.

How are prion diseases diagnosed? How are they treated?

Examine brain upon autopsy. Can also look for presence in CSF fluid, or on tonsils, or identify mutations. There is no treatment, but drugs may slow progression. Problem getting drugs past BBB.

What is the difference between HIV and AIDS?

HIV - human immunodeficiency virus. AIDS - Acquired Immunodeficiency syndrome - late stage HIV infection.

What are the recent developments regarding global eradication of polio?

Have sropped spread of polio in all countries at one point except Pakistan, Afghanistan, and Nigeria. P2 is gone. Next gone is P3. So give bivalent oral vaccine, and injection of dead for P1.

Explain the concept and importance of a species barrier in regards to prion diseases.

Idea that a prion from one species and the normal protein from another species are too different to effectively interact with eachother. Since replication depends on protein-protein interactions, even if one animal is exposed to prions from another type of animal, it may never develop disease. Scientists think this is not true. It just leads to a really long incubation period when prions are transferred. (up to 3 years).

What are some misconceptions about leprosy that have persisted?

If you had any contact with a person w/ leprosy, you would get it. Also, that it's untreatable.

Compare the two general types of polio vaccines. What is the problem with the oral polio vaccine?

Inactivated Virus - injected. 3 doses. Shorter immunity than oral. Oral - live attenuated virus, contains all 3 serotypes, 3 doses. Cheap and doesn't require medical professional. Duration of immunity - lifelong. But can get VAPP - because virus reverts back to original form.

Why has antibiotic resistance spread so quickly?

Inappropriate use of antibiotics. Golden age of antibiotics - microbes have gained resistance from selective pressures. Over 50% of those who get antibiotics don't need them, or are prescribed doses too low to be effective. We are bad at developing new drugs.

What is the basic disease progression for smallpox?

Incubation (7-17 days) Initial symptoms - achiness, malaise, high fever (2-4 days) Early rash - highly contagious in tongue or mouth - ( 4 days) Pustular rash - bumps more raised, solidified pustules - 5 days. scabs - 5 days - rash scabs over. Scabs resolve - 6 days. Overall 3 week illness.

What types of disease does Group A Strep cause?

Infections are variable. Most people get strep throat or impetigo. Sever cases - Strep TSS and NF.

How can meat from BSE infected cows be made safe for consumption?

It can't.

How is the HIV virus able to mutate rapidly?

Its a retrovirus, so it uses reverse transcriptase to incorporate into the host genome, and then undergoes transcription and translation within the host. Incredibly error prone, and up to 5-10 mutations per replication cycle.

Explain the difference between latent TB infection and active TB disease.

Latent - bacteria are not actively growing. Not contagious. Immune system is winning the battle. 85% of people will not progress to active. Active - 15% of latent infections become active. Immune system lost, so bacteria are actively growing. Can take years.

What problem may be associated with the smallpox vaccine?

Live virus - inadvertent innoculation - doesn't give lifelong immunity.

Describe multidrug therapy for leprosy? Why is this better than monotherapy? Are there any concerns/controversies surrounding the current multidrug therapies?

MDT - Rifampin, Clofazin, and Dapsone. Treatment has cured 16 million people. Monotherapy risks missed dose and development of resistant infection. Also monotherapy is lifelong. MDT is only 6 months to 2 years. Stigma: side effects causes darkness and scaliness of skin.

What strategies were used to eradicate smallpox?

Mass eradication wasn't possible. They used ring vaccination.

During which stages of smallpox are individuals contagious? Approximately how long does a person remain contagious during a smallpox infection?

Most contagious from initial rash all the way until rash scabs fall off. Up to 3 weeks.

How is antibiotic resistance thought to develop and spread in microbes?

Multiple instances of horizontal gene transfer, and binary fission. Spontaneous mutations could cause resistance, but most aren't beneficial.

What are some possible options for treating recurrent C. difficile infections?

Narrow spectrum antibiotics. Immunotherapy. Bacteriotherapy - probiotics, fecal transplants, non-toxin producing C. diff.

What are the major risk factors for nosocomial C. difficile infection? How are these different from the risk factors for community-acquired C. difficile infection?

Nosocomial - older than 65. On antibiotics within recent months. Receiving medical care. On acid blockers. Comorbitidity. Community = younger. females. likely to be healthy, not on antibiotics.

Why is the BCG vaccine not available in the US?

Nullifies the skin test. Risks don't outweigh the rewards.

Ca-MRSA

Only resistant to beta-lactam antibiotics. more virulent, and more easily transmissible, but causes little more than a skin infection. Skin-skin contact. wounds piercings. crowded living conditions.

How is smallpox spread?

Person to person. Prolonged contact (within 6 feet for 2-3 hours). Possible through bodily fluids. Rash is contagious for up to 3 weeks.

What characteristics of the NAP1 strain are believed to contribute to the increased incidence, severity, and mortality associated with this strain?

Resistant to fluoroquinolone. Increased Toxin Production. Production of toxin AB, which doesn't cause disease alone, but together with A and B, causes severe disease.

Ha-MRSA

Resistant to multiple drugs. Mildly virulent. symptoms: malaise, rash, chills, fever, shortness of breath, chest pain.

Why is surgical removal of infected tissue often necessary in cases of NF?

Since NF kills muscle and fat around the site of infection, antibiotics may not be able to reach the site of infection. Thus debridement can clear dead tissue to restore blood flow.

Define the different types of CJD.

Sporadic - 85% - no known cause. Familial - 15% - inherited PrPsc gene. Iatrogenic - 1 % - acquired in a medical setting. vCJD - through contaminated beef consumption.

Explain the process for C. diff infection. Why are infants not as susceptible as adults to have active disease?

Spores are ingested and go to intestinal tract where they germinate in small intestine. The vegetative cells end up in the colon where they colonize. Infants are not as susceptible because of their immature GI tract - the GI cells have no receptors for the toxins, but 50% of infants are colonized with C. diff.

What is the major characteristic that allows for C. difficile to be spread so easily in hospital settings? what are ways that its spread might be prevented?

Spread easily because of spore production. Population in hospital - lots of people on antibiotics. Alcohol based sanitizers don't work.

Explain the diagnosis process for MRSA. Make sure to include any potential problems with accurate diagnosis.

Suspected with any skin infection. Test resistance against oxacillin and cefoxitin. Complication: heteroresistance - resistance not always expressed under certain durations of incubation or conditions. PCR amplification - problem. mecA gene mutates. so primers would only be 70% similar. Risk factors, time, and medical history is usually enough for treatment to begin.

What are the symptoms associated with leprosy? What are leprosy reactions? When can they occur? What are the risk factors for each type?

Symptoms - Skin and nerve involvement. Lesions, growths, numbness, weakness, discoloration, and inflammation. Severe : amputations and blindness. Type I reaction - mild disease. Inflammaiton and pain in pre-existing legions. Multi drug therapy is risk factor. Type II reaction - Progressed disease. Inflmamation, new nodules under skin, fever and malaise. Risk factors are stress, severe leprosy, changes in hormone level (lactation, menstruation, puberty).

Explain the two types of TB tests.

TB skin test - inject tuberculin under skin, and look for immune response ( ring of swelling). TB blood test - measure immune response to the bacterium when injected. Tests don't indicate active disease. If symptoms present - chest X-ray and sputum culture to confirm.

What are symptoms of NF and TSS?

TSS - GAS produces toxin in bloodstream. Causes massive damage and organ failure. Symptoms - high fever, aches, malaise, low BP, Sunburn like rash, vomiting. NF - Localized, disproportionate pain. Swelling. Ulcers, black spots, or can all be internal. Possible fever, chills, and nausea.

In what ways can infection with prions occur?

The PrPsc gene can be inherited, acquired through contaminated food sources, or a random mutation can occur.

Explain the mechanism of methicillin resistance for MRSA.

The mecA gene encodes for PBP2a. 4 penicillin binding proteins are usually present in Staph aureus. They play an important role in peptidoglycan synthesis. PBPs are responsible for the cross linkages in cell wall. Methicillin usually binds to and inactivates PBPs. MRSA has a 5th PBP that methicillin cant bind to. PBP2a is extremely active, so it takes over the function of the other 4.

What is similar between the causative agents of TB and leprosy?

They are both mycobacterium, and are hydrophobic, due to the presence of mycolic acid in their cell wall.

What are prions? What are characteristics that separate them from other infectious agents?

They are misfolded proteins. Resistant to denaturation. Do not contain nucleic acids. Cannot destroy them. Cause transmissible spongiform encephalopathies.

What is the vaccine for chickenpox?

Varivax or Proquad. high risk of febrile seizures.

What is the vaccine for Shingles?

Zostavax. Most people don't know it exists, and insurance only covers it past a certain age, but that doesn't match with the optimal time for vaccination.

What factors may alter the effectiveness of antibiotics?

oral - survive low pH of the stomach topical - toxic if ingested BBB - infections in brain difficult to control Necrotic tissue - blocks blood flow to infection site Liver metabolism - drug must not be processed before reaching infection site drug degradation - drug can't degrade before reaching infection site Microbe susceptibility - has to be killable.