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MICROBIOLOGY BSL223Study Guide, Theory Exam 4
Chapter 20
- Terms include:
- Chemotherapy – The treatment of disease by the use of chemical substances. Paul Ehrlich from Germany coined the term “Chemotherapy” where he was looking for a magic bullet to destroy pathogens without harming their host. In 1909 Ehrlich discovered a compound to kill the parasitic spirochete that causes syphilis.
- Selective toxicity – Antimicrobial drugs are chemicals that kill microbial cells but not host cells
- The primary sources of natural antibiotics – Bacteria and Fungi, Page 550, Table 20. Bacteria – Gram + rods and Actinomycetes Gram Positive Rods – Bacillus Actinomycetes – Streptomyces, Saccharopolyspora, Micromonospora Fungi – Cephalosporium, Penicillium 3. The difference between broad spectrum and narrow spectrum antibiotics Narrow Spectrum – Treats a smaller range of different microbial types, for example: Penicillin G affects Gram positive but very few Gram negative bacteria. Broad Spectrum – Antibiotics that treat a broad range of Gram + and Gram - bacteria. Examples of when a Broad Spectrum Antibiotic would be given: Soldier with battle wounds and emerging trauma, Pre-op prophylactically for surgery (abdominal, oral, transplants, indwelling devices). Judicious Use of Antibiotics – Be selective and use discriminatorily. Should treat with narrow spectrum antibiotics to prevent resistance to broad spectrum antibiotics. To prevent the overuse of antibiotics where more strains of microorganisms become more resistant.
Bactericidal – kill microbes directly Bacteriostatic – prevent microbes from growing (host uses phagocytosis and antibodies)
4. What is a superinfection and what causes it? A superinfection is an overgrowth of a pathogen that has developed a resistance to an antibiotic. Antibiotic resistant strains replace the original strains and the infection continues. Broad spectrum antibiotics destroy many normal microbiota, therefore other microorganisms become opportunistic such as C. diff. A typical overgrowth is yeast, Candida albicans, which is not sensitive to antibiotics.
- The 5 major antibiotic modes of action. (Page 551, Table 20.2) 1. Inhibition of Cell Wall Synthesis – penicillin, cephalosporin, bacitracin, vancomycin 2. Inhibition of Protein Synthesis – chloramphenicol, erythromycin, tetracycline, streptomycin 3. Inhibition of Nucleic Acid Replication – quinolones, rifampin 4. Injury to Plasma Membrane – polymyxin B 5. Inhibition of Essential Metabolite Synthesis – sulfanilamide, trimethoprim 6. The 3 groups of Beta lactam antibiotics – Page 557 Penicillins – Natural and Semisynthetic, have a common nucleus, B-Lactam rings, but different R groups Natural – Penicillin G (Injection), Penicillin V (Orally) Semisynthetic – Oxacillin (Narrow spectrum, only for Gram +, resistant to penicillinase) Ampicillin (Extended spectrum, treats many Gram negatives) Augmentin – Amoxicillin + Clavulanic Acid… Amoxicillin is semi-synthetic penicillin and clavulanic acid is the compound that inactivates penicillinase. Cephalosporins – Inhibit Cell Wall synthesis, grouped according to their generations 1 st^ Generation (Ceph) – narrow level of activity against Gram negative bacteria 2 nd^ Generation (Cef) – more extended Gram negative spectrum 3 rd^ Generation (Cef) – most active against Gram negative, some pseudomonads, injected 4 th^ Generation (Cef) – require injections, most extended spectrum 5 th^ Generation (Cef) – MRSA coverage Carbapenems – Most potent, last line of defense, inhibit cell wall synthesis, examples
for para-aminobenzoic acid (PABA), and blocks folic acid production) Vancomycin – Use: MRSA, Staphylococcus aureus Mode of Action: Inhibition of cell wall synthesis (glycopeptide) Cephalosporins – Rocephin – Use : Meningitis, UTI, sepsis, Lyme disease Mode of Action: Inhibition of cell wall synthesis (B-lactam ring) Carbapenems – Doripenem – Use: Pseudomomas aeruginosa Mode of Action: Inhibition of cell wall synthesis (B-lactam ring) Ultra broad spectrum HAART (Highly Active Anti-Retroviral Therapy) – Cocktail Therapy for HIV Antiviral Drugs Entry and Fusion Inhibitors – interfere with assembly and release steps Entry – Non-enveloped, target receptors that HIV uses to bind to the cell before entry Fusion – Enveloped, blocks fusion of the virus and the cell Exit Inhibitors – Inhibits enzyme neuraminidase, which blocks release of cytokines (Flu) Interferons – Alpha interferon is the current drug of choice for viral hepatitis Antifungal Drugs – Azoles – filamentous or unicellular, fluconazole and ketoconazole, used topically or systemic (oral route), for treatment of thrush, yeast Antiprotozoan Drugs – Flagyl – Treats Trichomonas vaginalis Antihelminthic Drugs – Niclosamide – Treats tapeworm infections
10. The disk-diffusion method for testing antimicrobial agents Kirby Bauer test – The bacteria must be water soluble, paper disks impregnated with chemotherapeutic agents are placed on the agar, a “zone of inhibition” forms around the disk which dictates how sensitive the microbe is to the antibiotic. 11. The mechanisms of antibiotic resistance – Page 570, Table 20.
- Blocking entry –
- Inactivation by enzymes –
- Alteration of target molecule –
- Rapid efflux (ejection) of the antibiotic – 12. R factors – A plasmid that allows bacteria to become resistant to one or more antibiotics Chapter 18 – This chapter not originally on the outline, although Prokopp said he had to cover it Herd Immunity – 70% to 80% of people get vaccinated in a community to prevent an epidemic from occurring. Get vaccinated against bacteria, viruses, and toxins. Influenza – most deadly virus in the last 100 years. Vaccines – Are used for prevention of illness rather than treating an illness. By age 12 months, a child has 7 vaccines including the flu, the first vaccine is Hepatitis B given at birth. The Influenza virus is grown in embryonated eggs to create the vaccine. Live Attenuated Vaccines – Infectious live vaccines that are not pathogenic, mimic an actual infection, humoral immunity is induced, B-cells make antibodies, adaptive immunity Subunit Vaccines – use antigenic fragments of a microorganism to stimulate an immune response. Avoids the danger with the use of live or killed pathogenic organisms (Recombinant vaccines). The Hepatitis B vaccine is an example of this. Toxoids – inactivated toxins from a pathogen, produces immune response without getting sick. PPSV23 – Pneumovax – multi valent, protects against 23 types of pneumococcal bacteria, recommended for age 65 and older. Also for age 2 and older who are at high risk for disease. PVC13 – Prevnar13 - multi valent, protects against 13 types of pneumococcal bacteria. Conjugated Vaccines – developed in recent years to deal with poor immune response of children to vaccines. Polysaccharides are combined with proteins such as diphtheria or tetanus toxoid, very successful even at 2 months of age. Primary and Secondary Immune Response to an Antigen – Vaccines produce the primary
Lung – Cystic Fibrosis Pneumococcal pneumonia – VAP (ventilator associated pneumonia), trach tubes
4. Other infectious diseases and the pathogens that cause them: - Chickenpox (Varicella) and Shingles (Herpes Zoster) – caused by human herpes virus 3, after chicken pox outbreak the virus lives in neurons of the ganglion cell root (near the spinal cord) where it remains latent indefinitely, in late adulthood it can reactivate and cause shingles. Lysogenic Provirus, Viravax vaccine (booster) may prevent outbreak. Post herpetic neuralgia – acute pain where the lesions were. - Herpes – HSV1 and HSV2 – treated with Acyclovir HSV1 – cold sores, fever blisters, on the lips and mouth. 90% of population have circulating antibodies, remains latent in the trigeminal nerve ganglion of the face. Herpetic whitlow (lesions on fingers) caused by contact with HSV HSV2 – Genitals, transmitted by sex, latent found in the sacral nerve ganglia near the base of the spine. Stress usually causes an outbreak. - Measles – extremely and most contagious, starts as an upper respiratory infection (URI), children do not receive this vaccine until they are at least 12 months old because their immune response is not fully developed, receive Measles, Mumps, Rubella (MMR) at 12 months old, 1 million children die per year from measles. - Cutaneous fungal infections – ( Cutaneous mycosis), informally known as tineas or ringworm, Tinea capitis (Head), Tinea pedis (Athlete’s foot), Tinea cruris (Jock itch, groin), Tinea unguium (Fingernail, toenails) - Candidiasis – (Yeast) – Oral mucosa (Thrush), Vaginosis or Vaginitis, rectal/anal, skin folds (breast/fat), oropharyngeal - Pediculosis (Lice) – Arthropod, the egg case of a nit is the nymphal stage of the louse (lice), it exits through the cap of the egg by gulping air and forcing out the anus until it pops free, much like a champagne cork. - Conjunctivitis (Red/Pink eye) – Fungal keratitis – caused by fusarium fungi, dirty contact lenses, treat with natamycin, Ophthalmia neonatorum –
infant acquired through birth canal from mom with gonorrhea and chlamydia, can cause blindness
- Trachoma – Chlamydia trachomatis, transmitted by hand contact, sharing objects such as towels, leads to Trichiasis where the eyelids turn in and cause abrasions to the cornea, leading cause of blindness. 5 million blinded victims.
- Herpetic Keratitis – caused by HSV1, infection of the cornea resulting in deep ulcers, causes infectious blindness, treated with Trifluridine. **Chapter 22
- Bacterial meningitis – the 3 most common pathogens –** diagnosed by spinal tap or lumbar puncture, cloudy fluid is very bad. The history of the patient and S/S macular rash, stiff neck, sore throat, fever, lethargic. Crosses through the meninges or the blood brain barrier or both. Meningitis is inflammation of the meninges. Encephalitis is inflammation of the brain. 1. Streptococcus pneumoniae – most common, especially in children less than 4 year’s old (30%) mortality and the elderly (80%) mortality. 2. Haemophilis influenza – nearly eliminated in US due to the Hib vaccine in 1988. 3. Neisseria meningitis – transmission by droplet or direct contact. Typical for college students living in dormitories. **2. Infectious diseases and the pathogens that cause them:
- Tetanus –** Gram +, caused by Clostridium tetani, common in soil contaminated with animal feces, low LD50, S/S is extreme muscle rigidity and paralysis. The bacteria releases a neurotoxin called tetanospasmin which cause the symptoms of tetanus. Vaccine is a toxoid that is inactivated and stimulates antibodies.
Bubonic Plague – spread by fleas from infected animals, 70% mortality, gets into lymph nodes which become swollen and called a bubo.
- Lyme disease (Lyme Borreliosis) – most common tick borne disease in US, grossly unreported, 3 phases, 1 st^ phase is a bull’s eye rash most common in 75% of cases, 2nd^ phase is an irregular heartbeat and neuro defects (facial paralysis, memory loss), 3 rd^ phase months or years later is arthritis.
- Viral Hemorrhagic Fevers – transmitted by mosquito Ades aegypti Yellow Fever – fever, chills, headache, vomiting, followed by Jaundice which reflects liver damage, where it got its name Yellow fever. Dengue Fever – “Break bone fever”, often not fatal unless it progresses to Dengue Hemorrhagic Fever, no vaccine or antiviral drugs have been found to be effective, can also cause Chikungunya Fever.
- Malaria – caused by mosquito vector Anopheles (night feeder), human host for the parasite Plasmodium falciparum , 210 million infected and less than 2 million deaths, spraying and netting helped to lower rates of infection, Artemisinin treatment is the last line of defense. **Chapter 24
- Infectious diseases and the pathogens that cause them.
- Pharyngitis and Scarlet fever.
- Whooping cough.
- TB.
- Bacterial Pneumonias
- Influenza.**
**2. The CDC Childhood Vaccination Schedule. Chapter 25
- Infectious diseases and the pathogens that cause them:
- Dental carries and periodontal disease
- Gastroenteritis and diarrheal diseases: o Salmonellosis o Cholera o EHEC o H. pylori o CDAD o Hep B and Hep C. Know how they are transmitted, whether or not there are vaccines, diagnostic t tests, presentations, at-risk groups, and morbidity/mortality statistics (hint: see fig. 25.15.) o Norovirus o Ascariasis**
4. PID: pathology and common pathogens
