Microbial Control PDF

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Notes on the effective ways to control microbial growth especially in the healthcare preofession....

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Chapter 10 Key Terms Narrow Spectrum: Antimicrobials that are effective against only a limited variety of microbial types Broad Spectrum: Antimicrobials that are effective against a wide variety of microbial types Antibiotic: Substances produced by natural metabolic processes of some microorganisms that inhibit the growth of some microorganisms. Prophylaxis: Use of a drug to prevent infection in a person at risk Minimum Inhibitory Concentration: The smallest concentration of a drug that inhibits growth of microbes Therapeutic Index: The ratio of the dose of the drug that is toxic to humans compared to its minimum effective dose Drug Toxicity: Drug that negatively impacts the body systems. EX: Carbenicillin can cause abnormal bleeding Drug Allergy: Drug stimulates antigens to activate immune response. Ex: Penicillin can cause rashes and hives

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An ideal antimicrobial drug is broad spectrum with no negative effect on host, it’s microbicidal over microbistatic, its easily delivered to the infection site, causes no allergic response or predisposition to other infections, also it will work with hosts immune system. A high therapeutic index (TI) is considered safer than a drug with a lower TI. The therapeutic index is the ratio toxic dose to the minimum effective dose. A higher TI indicates a wider margin between the effective dose and the toxic dose. Whereas the smaller the TI the more narrow the margin between the toxic and effective dose making it more potentially toxic. The Cell Wall (Penicillin’s), Protein Synthesis (Tetracycline), Folic Acid Synthesis (Sulfonamides), DNA/RNA (Quinolones), Cell Membrane (Polymyxins) Most chemotherapy drugs are designed to target bacteria and are thought to be ineffective on fungus, protozoa and helminthes. Specifically fungal cells are similar to human cells so drugs toxic to fungus could be potentially as toxic to human cells. Helminthic infections are difficult to treat as well because of their similarity to human physiology and most tapeworms, roundworms and parasites are larger than most microorganisms. Before selecting antimicrobial treatments you should know the causative organism, the microorganisms sensitivity to drugs and the medical condition of the patient. (Same as #3?) Most antimicrobials are structured to treat bacterial infections. Most eukaryotic infections like fungal, helminthic, and protozoan are either much larger than bacterial microbes or their cell structures are closely similar with human body cell structure. This makes it difficult to find a drug that is toxic to the microbe but non-toxic to human cells. The most effective anthelminthic drugs immobilize or disintegrate the metabolism in all stages of their life cycles. Examples include Mebendzole and Albendazole. The three main modes of antivirals are to inhibit entry of the virus (ex: Enfuvirtide {Fuzeon}), Inhibition of nucleic acid synthesis (Acyclovir), and prevention of the maturation of viral particles (Idinavir) Drug resistance is an adaptive mechanism that occurs when microorganisms tolerate drugs that normally inhibit them. It can occur from spontaneous mutation in a critical chromosomal gene or through acquisition of entire new genes or sets of genes via horizontal transfer from another species. New enzymes are synthesized and the drug becomes inactivated, mutation allows less permeability, the drug becomes eliminated, binding sites fro drugs decrease, metabolic pathway is shut down and an alternative pathway is used. Resistance is a problem because new and effective antibiotics have become increasingly slim in availability. Example: Urgent Threat- C Diff, Serious Threat- Drug resistant tuberculosis, Concerning threat-vancomycin resistant VRSA Future options include RNA Interference (Small RNAs can turn off target genes in microbes), CRISPR (cutting out specific bad pieces of genes) Probiotics are preparations of live microorganisms that are fed to animals and humans to improve the intestinal bacteria (Bacterial Flora). Prebiotics encourage the growth of beneficial microbes in the intestine

15. A superinfection is when antimicrobial agents introduced to the host destroys beneficial resident species and other microbes that were once in small population overgrow and cause disease. In the past physicians prescribed broad-spectrum drugs for minor infections instead of more narrowspectrums, which led to the unnecessary killing of good bacteria flora.

Chapter 11 Key Terms Colonization- When bacteria grow on body but do not cause infection Infection- During infection, microbes get past host defenses, gain entry into tissue and multiply Disease- when damage occurs to tissue from infection Microbiota- Community of pathogenic microorganisms Pathogenicity- Organisms Potential to cause disease Virulence- Relative severity of a disease caused by a microbe Portal of Entry- How microbes gain entry into host (Skin, GI Tract, Respiratory Tract) Communicable- when infected host can transmit infectious agent to another host and establish infection in that host Noncommunicable- infectious disease does not arise through transmission from infected host to host Direct Transmission- Involves very close proximity or contact between two hosts (kissing touching sex) Indirect Transmission- Infectious agent > Intermediate conveyor (vehicle i.e. food, air, water) >host Endotoxins- LPS part of cell membrane of gram negative bacteria, systemic effects, fever inflammation Exotoxins {Secreted}- Specific proteins that have a specific cell type target for damage (hemolysis disrupt red blood cells) Prevalence-Total number of existing cases in a single period Incidence- Study of new cases over a certain time period

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They first find a portal of entry (Skin, GI Tract, Respiratory Tract), Attach Firmly and negotiate with micro biome (Fimbriae, capsules), Survive hosts defenses (Avoid phagocytosis, Absence of specific immunity) Cause Damage (Disease) (direct damage via enzymes or toxins, epigenetic effects in host), Exit Host (Respiratory tract, fecal matter, skin) 1. Microbial enzymes, toxins and endo/exotoxins disrupt host cell structure 2. Microbes evade initial host defenses and host continues to react to presence of microbe causing host damage. 3. Microbial products make epigenetic changes to the DNA and structures (histones) altering genes expressed. Exotoxins: Specific to cell type, small proteins, unstable, stimulate antitoxins, don’t stimulate fever usually, secreted from live cells, gram negative and positive. Endotoxins: Systemic, fever, inflammation, lipopolysaccharide of cell wall, stable, don’t stimulate antitoxins, released by cell via shedding or lysis, all gram-negative bacteria.

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Asymptomatic Carriers: Infected but show no symptoms of disease (gonorrhea), Incubating Carriers: Spread the infectious agent during incubation period (Mono), Convalescent: Recuperating patients without symptoms, they shed viable microbes and convey infections to others (Hepatitis A), Chronic Carriers: Individuals who shelter the infectious agent for a long period of time after recovery because of the latency of the infectious agent (Tuberculosis), Passive Carriers: Medical and dental personnel who handle heavily contaminated patient material with secretions and blood that they transfer to other patients (Healthcare diseases) Rabies (Mammals)

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Vertical: Parent-Offspring via milk, ovum. Horizontal: One infected individual  another. Vector: Insect Person Infectious diseases acquired or develop through stay at healthcare facility Ex: MRSA The study of disease in population

Common source propagated source Localized infection: Microbes enter body and remain confined to specific tissue, Systemic infection: Infection spreads to several sites and tissue via blood stream, Focal Infection: Spreads from local site and carried to other tissue, Mixed (polymicrobial): several agents establish themselves at sites, Primary infection: initial infection, Secondary Infection: second infection caused by a different microbe, Acute: Infection comes rapidly with severe but short-lived effects, Chronic Infection: Infection progresses and persists Skin, Upper Respiratory tract, GI Tract, Genitalia, Lungs, Bladder, Breast, Brain, Bloodstream The good microbes have antagonistic effects against intruder microbes. They help our immune system and protect us from invading microorganisms Old age, pregnancy, chemotherapy/immunosuppressive drugs, underlying disease (cancer, diabetes)...