1.Microorganisms: produce enzymes that destroyes the active drug. Examples: Staphylococci resistant to penicillin G produce a β-lactamase that destroys the drug.
2. Microorganisms change their permeability to the drug. Examples: Tetracyclines accumulate in susceptible bacteria but not in resistance bacteria. Resistance to polymyxins is also associated with change in permeability to the drug.
3. Microorganism develop an altered structural target for the drug. Examples: Erythromycin-resistant organisms have an altered receptor on the 50S subunit of the ribosome, resulting from methylation of a 23S ribosomal RNA. Resistance to some penicillin's and cephalosporin may be a function of the loss or alteration of PBPs.
4. Microorganism develop an altered metabolic pathway that bypasses the reaction inhibited by the drug. Examples: Some sulfonamide-resistant bacteria do not require extracellular PABA but, like mammalian cells, can utilize preformed folic acid.
5. Microorganism develop an altered enzyme that can still perform its metabolic function but is much less affected by the drug. Examples: In trimethoprim-resistant bacteria, the dihydrofolic acid reductase is inhibited far less efficiently than in trimethoprim-susceptible bacteria.
Origin of drug resistance: 1. Non-Genetic origin 2. Genetic Origin
Mycobacterium/TB=Resistant لان تبقى فتره طويلة بلجسم تسوي نفسها
Log phase = الطور الي تنقتل بيه البكتيريا بسهولة لان تتكاثر بسرعة
Aminoglycosides such as gentamicin are not effective in treating salmonella enteric fevers because the salmonellae are intracellular and the aminoglycosides do not enter the cells.
البلدان النامية مثل مصر او العراق :
1-ينطون antimicrobials بدون استشاره طبيه ( without medical authorization or supervision)
2-Guidelines (مرشد طبي اساسي بكل مستشفى ع شكل كتاب) لا يتوفر في مصر وان توفر ف هو مو دقيق
3-اعطاء Antibiotics حت اذا مجان اكو داعي له مثلا ينطون ( ارثرومايسين ، اوجمنتين) للفلاونزه
4-استخدام Broad spectrum antibiotics بشكل متكرر ( فركونتلي)لحد ما يصير مقاومه للجسم بحيث بعد ميفيد
5- Laboratory facilities تشخص الامراض ماكو not available
6- Overcrowding and poor hygiene ( الازدحام خالي) هوايه اكو ف تصير عدوى
7- Infection control ( دكتور عباس اعني ناس اخصاء يكافحون العدوى ) قليل بالمستفيات are often inadequate
8- Many countries do not have effective surveillanceمراقبه لل انتيبايوتيك او تدريب وتسهيلات ماكو ف (يصير جهل يا خالي)
9- Developing countries are often unable to afford costly ( اكو ناس معدها امكانيه تشتري الدوا الزين)
Cross Resistance Microorganisms resistant to a certain drug may also be resistance to other drugs that share a mechanism of action
Limitation of Drug Resistance
1.By maintaining sufficiently high levels of the drug in the tissues to inhibit both original population and first-step mutants.
2.By simultaneously administering two drugs that do not give cross-resistance
3.By avoiding exposure of microorganisms to a particularly valuable drug by limiting its use, especially in hospitals.
• Proteus species are generally resistant to nitrofurantoin and tetracyclines.
• S.pyogenes is usually sensitive to penicillin
• K.pneumoniae is generally ampicillin resistant.
• Anaerobes are sensitive to metronidazole
Selective appropriate antimicrobial treatment also involves considering:
a)Condition (e.g. Liver or kidney disease),
b)The type and site of the infection,
c) Any history of drug hypersensitivity,
D. Age of patient E. Whether a patient is pregnant
Sensitivity testing techniques Laboratory antimicrobial sensitivity testing can be performed using:
1.A dilution technique = minimum inhibitory concentration (MIC)/ minimum bactericidal concentration (MBC)
2.A disc diffusion technique
2. Microorganisms change their permeability to the drug. Examples: Tetracyclines accumulate in susceptible bacteria but not in resistance bacteria. Resistance to polymyxins is also associated with change in permeability to the drug.
3. Microorganism develop an altered structural target for the drug. Examples: Erythromycin-resistant organisms have an altered receptor on the 50S subunit of the ribosome, resulting from methylation of a 23S ribosomal RNA. Resistance to some penicillin's and cephalosporin may be a function of the loss or alteration of PBPs.
4. Microorganism develop an altered metabolic pathway that bypasses the reaction inhibited by the drug. Examples: Some sulfonamide-resistant bacteria do not require extracellular PABA but, like mammalian cells, can utilize preformed folic acid.
5. Microorganism develop an altered enzyme that can still perform its metabolic function but is much less affected by the drug. Examples: In trimethoprim-resistant bacteria, the dihydrofolic acid reductase is inhibited far less efficiently than in trimethoprim-susceptible bacteria.
Origin of drug resistance: 1. Non-Genetic origin 2. Genetic Origin
Mycobacterium/TB=Resistant لان تبقى فتره طويلة بلجسم تسوي نفسها
Log phase = الطور الي تنقتل بيه البكتيريا بسهولة لان تتكاثر بسرعة
Aminoglycosides such as gentamicin are not effective in treating salmonella enteric fevers because the salmonellae are intracellular and the aminoglycosides do not enter the cells.
البلدان النامية مثل مصر او العراق :
1-ينطون antimicrobials بدون استشاره طبيه ( without medical authorization or supervision)
2-Guidelines (مرشد طبي اساسي بكل مستشفى ع شكل كتاب) لا يتوفر في مصر وان توفر ف هو مو دقيق
3-اعطاء Antibiotics حت اذا مجان اكو داعي له مثلا ينطون ( ارثرومايسين ، اوجمنتين) للفلاونزه
4-استخدام Broad spectrum antibiotics بشكل متكرر ( فركونتلي)لحد ما يصير مقاومه للجسم بحيث بعد ميفيد
5- Laboratory facilities تشخص الامراض ماكو not available
6- Overcrowding and poor hygiene ( الازدحام خالي) هوايه اكو ف تصير عدوى
7- Infection control ( دكتور عباس اعني ناس اخصاء يكافحون العدوى ) قليل بالمستفيات are often inadequate
8- Many countries do not have effective surveillanceمراقبه لل انتيبايوتيك او تدريب وتسهيلات ماكو ف (يصير جهل يا خالي)
9- Developing countries are often unable to afford costly ( اكو ناس معدها امكانيه تشتري الدوا الزين)
Cross Resistance Microorganisms resistant to a certain drug may also be resistance to other drugs that share a mechanism of action
Limitation of Drug Resistance
1.By maintaining sufficiently high levels of the drug in the tissues to inhibit both original population and first-step mutants.
2.By simultaneously administering two drugs that do not give cross-resistance
3.By avoiding exposure of microorganisms to a particularly valuable drug by limiting its use, especially in hospitals.
• Proteus species are generally resistant to nitrofurantoin and tetracyclines.
• S.pyogenes is usually sensitive to penicillin
• K.pneumoniae is generally ampicillin resistant.
• Anaerobes are sensitive to metronidazole
Selective appropriate antimicrobial treatment also involves considering:
a)Condition (e.g. Liver or kidney disease),
b)The type and site of the infection,
c) Any history of drug hypersensitivity,
D. Age of patient E. Whether a patient is pregnant
Sensitivity testing techniques Laboratory antimicrobial sensitivity testing can be performed using:
1.A dilution technique = minimum inhibitory concentration (MIC)/ minimum bactericidal concentration (MBC)
2.A disc diffusion technique