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Lo10 Pc2 Infectious Diseases

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Lo10 Pc2 Infectious Diseases
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LO10 PC2 INFECTIOUS DISEASES Infectious Diseases Syn: Communicable Diseases Caused by micro-organisms or Parasite – living in/on and feeds on host Henedina A. aini! "Ph #$%& Page %
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LO10 PC2 INFECTIOUS DISEASES

Infectious DiseasesSyn: Communicable DiseasesCaused by micro-organisms or Parasite living in/on and feeds on host

Contamination vs. infection Contamination the mere presence of microbes in or on the bodyInfection results when the organism has invaded the bodys external defenses, multiplied, and become established in the body

Disease ProcessPathogens generally cause disease by one of two basic mechanisms1) Rapid growth2) Production of toxins

Stages in the development of a disease1. Exposure2. Incubation Period3. Prodromal Period4. Acute Stage5. Recovery Stage6. Convalescence7. Immunity

Exposure & IncubationExposure = contactTime between infection and the appearance of signs and symptoms

Prodromal StageMild, non-specific symptoms that signals the onset of the diseaseEx: headache/ soreness/ tirednessClinical StageTypical signs and symptoms of the diseaseMost contagious Most affectedRecovery Stage (decline of illness)Signs/ symptoms begin to subsideTemperature is reducedFeeling a little bit better

Convalescence or Recovery StageSymptoms have disappearedTissues healBody regains strengthCan have relapseNeed rest, sleep, healthy diet

ImmunityFully recoveredFeel 100% functionalBody has developed antibodiesProtected from the same infection Antimicrobial ResistanceAntimicrobial resistance: When microorganism is no longer affected by a particular antimicrobial that was once effective against that species. Determined via the culture and sensitivity testing

Culture and Sensitivity Testing of Bacteria Bacteria isolated from the site of infection are cultured on a plate. Some bacteria cannot be cultured on a plate Ex. leprosy must be cultured in an armadillo or on the foot plate of a mouse Paper discs soaked with various antibiotics are applied to the plate. If the bacteria is affected by the antibiotic or sensitive to it, a zone of inhibition is seen. Indicates that the bacteria is susceptible to the drugThe size of the zone of inhibition is a measure of how well the antibiotic works against that particular bacterium.

Mechanisms of Antimicrobial Resistance Production of a drug-inactivating enzyme by the microbe Change in receptor structure of the organism Change in structural features of the microorganism that affect drug permeability Development of alternative metabolic pathwaysThese abilities can be conferred on a particular bacterium by a spontaneous mutation or conjugation (a sort of bacterial sex).

Factors Promoting Development of Antimicrobial ResistanceI. Administration of antimicrobials when not needed.- Antibiotics are not effective against viruses

II. Non-adherence to dosing regimen.III. Dosing that does not maintain adequate drug levels. Drug levels may be too low Correct dosing but drug absorption is poor Ex. when drugs are taken with antacids

Common Resistant MicrobesMethicillin-resistant Staphylococcus aureus (MRSA)Penicillin-resistant Streptococcus pneumoniae Vancomycin-resistant Enterococci (VRE)Multi-drug resistant tuberculosisHIV

Principles of Antimicrobial Selection and Administration I. Match drug with bug principle II. Consider Drug SpectrumIII. Consider Combination TherapyIV. Consider Site of InfectionV. Maintain Adequate Drug Blood LevelsVI. Antibiotic Combinations

I. Match the Drug with the BugA. Identify pathogen: culture, gram stain (positive vs. negative), common causeB. Determine microbial susceptibility to drug: culture and sensitivity, genotype and phenotype, literature- This can be done even before the drug is given to the personC. Role of infectious disease consultant1. Suggest appropriate therapy2. Prevent overuse or inappropriate use of antimicrobials

II. Spectrum, Therapy, and Site of InfectionNarrow vs. Broad Spectrum drug

III. Consider Combination therapyIV. Consider Site of Infection Skin Lung Meninges/brain AbscessV. Maintain Adequate Drug Blood Levels Antibiotic administration varies, i.e. QID or TID, etc.Depends on: half-life of the medication how fast the medication is excreted through the liver or the fecesSome oral antibiotics should be administered on an empty stomach and should not be co-administered with other oral medications.

VI. Antibiotic CombinationsCombinations of antibiotics working on different mechanisms may be synergistic or antagonistic with each other.In the case of mixed infections with more than one bacterial species, a combination may be required.In some instances, antibiotic resistance is discouraged by combinations.Combinations should be used only when indicated.

Which of the following promote antimicrobial resistance?1. Administering antimicrobials when needed2. Maintaining adequate drug levels3. Non-adherence to regimen4. Using antimicrobial to which the organism is sensitive

Patient Variables in Administering Antimicrobials A. Health status: comorbidities, immunosuppressive therapy, etc.B. Life span and gender: appropriateness of dose and agentC. Ethnicity/culture: belief about medications may hinder complianceD. Environment: access to refrigeration, running water, etc.Adverse Effects of Antibiotic Therapy Normal gut flora are killed, producing diarrhea and can pave the way for colonization with pathogenic bacteria, possibly even leading to death. Ex. E. Coli and other organisms help to maintain normal gut function Suprainfection infection with a second (antibiotic resistant) organism that occurs during antibiotic therapy. In pseudomembranous colitis, the bowel is colonized with Clostridium difficile, producing a severe diarrhea that is sometimes fatal. Allergy most common with the penicillins.

END OF LECTURE

Henedina A. Maini, RPh 2015Page 7


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