Microbiology &Antibiotics


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A brief on Microbiology, Infections and Antibiotics

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Microbiology &Antibiotics

  1. 1. Microbiology, Infections & Antibiotics Shilpa Garg
  2. 2. Microbiology • Microbiology - Branch of medical science, related to the study of micro-organisms like bacteria, viruses, parasites, fungi etc. – Bacteriology – Virology – Mycology – Parasitology
  3. 3. Bacteria • All bacteria are unicellular organisms that reproduce by binary fission. • Bacterial cells are extremely small and are most conveniently measured in microns.
  4. 4. Classification of Bacteria • Shapes • Cocci – Spherical or Round Shaped • Bacilli – Rod Shaped • Vibrios - Comma Shaped • Spirilla – Spiral Shaped
  5. 5. Classification of Bacteria • Gram Stain – Gram Positive - Retain Primary Colour (Blue) – Gram Negative - Retain Secondary Colour (Pink) • Aerobes – Require Oxygen for growth • Anaerobes - Grow in absence of Oxygen
  6. 6. Bacteria • Gram Positive Aerobes – Cocci – Staphylococcus aureus – Streptococcus pneumoniae – Enterococcus • Gram Positive Aerobes – Bacilli – Corynebacterium – Listeria
  7. 7. Bacteria • Gram Positive Anaerobes – Cocci – Peptococcus – Peptostreptococcus • Gram Positive Anaerobes – Bacilli – Clostridium tetani – Lactobacilli
  8. 8. Bacteria • Gram Negative Aerobes – Cocci – Neissaria gonorrhoea – Moraxella catarrhalis • Gram Negative Aerobes – Bacilli – E coli – Enterobacter – Klebsiella – Proteus – Pseudomonas – H influenza – Salmonella – Shigella – H pylori
  9. 9. Bacteria • Gram Negative Anaerobes – Cocci – Veillonella • Gram Negative Anaerobes – Bacilli – Bacteroides fragilis – Fusobacterium
  10. 10. Bacteria • Atypical Organisms -Microorganisms that have undergone greater changes than normal in morphology, physiology, or cultural characteristics – Mycoplasma – Chlamydia – Ureaplasma • Acid Fast Bacilli - Bacteria that are not decolorised by acid-alcohol after having been stained with dyes such as basic fuchsin. – Mycobacterium tuberculosis
  11. 11. Bacteria E Coli E Coli
  12. 12. Bacteria TB Causing Bacteria Mycobacterium tuberculosis
  13. 13. Bacteria Anthrax Clostridium perfringes
  14. 14. Bacteria E. coli Clostridium tetani
  15. 15. Bacteria Neisseria Staph. aureus gonorrhoeae
  16. 16. Bacteria Strep Neisseria meningitidis
  17. 17. Infections • It is defined as the successful invasion and multiplication of micro-organisms in body tissues.
  18. 18. Sources of Infection in Man • A) Man – Carrier-The person who harbors the pathogenic micro-organisms without suffering any ill effects from it.
  19. 19. Sources of Infection in Man a) Man • Healthy Carrier • Convalescent Carrier • Temporary Carrier • Chronic Carrier b) Animals c) Insects d) Soil and Water e) Food
  20. 20. Method of Transmission 1) Contact Contact can be direct: e.g. Syphilis, Gonorrohoea, AIDS Or contact can be indirect: e.g. through fomites such as clothes, towels, pencils etc.
  21. 21. Method of Transmission 2) Inhalation : (Air-borne) Inhalation can be a method of transmission eg. tuberculosis bacilli and influenza viruses. 3) Ingestion : (Food-borne) Mode of infection by ingestion can be of three types: a) Water : e.g. Cholera b) Food :e.g. Staphylococcus food poisoning c) Hand : e.g. bacillary dysentery
  22. 22. Method of Transmission 4) Inoculation: Introduction of organisms directly into the tissue e.g. a) tetanus spores inoculated in wounds b) rabies virus deposited subcutaneously by dog bite. 5) Congenital Infection Pathogens are able to cross the placental barrier and infect the foetus in the uterus. This is known as vertical transmission. e.g. congenital syphilis, intrauterine infection.
  23. 23. Clinical Features of Infections 1) Fever 2) Chills 3) Myalgia 4) Photophobia 5) Lymphadenopathy 6) Splenomegaly 7) G.I.Upset
  24. 24. Diagnosis of Infection A) Direct evidence of infection i) Direct microscopic examination a) Gram stain b) Ziehl – Neelsen stain ii) Cultures B) Indirect evidence of infection a) Blood b) Urine analysis
  25. 25. Bacterial Resistance Bacterial resistance is either 1. Natural Resistance 2. Acquired Resistance a) Mutation 3. Cross Resistance
  26. 26. Infections • Urinary Tract Infections – Microbial colonization in urine and tissue invasion of any structure of the urinary tract – Complicated UTIs – Abscess, calculi, requires prolonged therapy – Uncomplicated UTIs – Dysuria, polyuria, simple to treat – Lower UTIs – Upper UTIs – Recurrent UTIs • Relapse • Reinfection
  27. 27. Urinary Tract Infections • Terms used in UTIs – Pyuria – Pus in the Urine – Haematuria – Blood in the Urine – Proteinuria – Proteins in the Urine – Dysuria – Painful Urination – Polyuria – Increased Frequency of Micturition – Oliguria- Scanty Urine
  28. 28. Urinary Tract Infections • Terms used in UTIs – Anuria – Absence of Urine – Urethritis- Inflammation of Urethra – Cystitis - Inflammation of Urinary Bladder – Pyelonephritis - Inflammation of the Kidney including the Pelvis of the Ureter – Prostatitis - Inflammation of the Prostrate – Bacteriuria – Bacteria in Urine
  29. 29. Urinary Tract Infections • Common Micro-organisms – E.coli – Proteus – Klebseilla – Pseudomonas – Enterobacter
  30. 30. Gynaecological Infections • Pelvic Inflammatory Disease – Ascending spread of micro-organisms from the vagina and cervix to endometrium, fallopian tubes and other adjoining structures – Polymicrobial in nature – Streptococci, Peptostreptococci, Bacteroides, prevotella, E.coli – Lower abdominal pain, vaginal discharge, fever, chills, vomiting, dyspareunia, menstrual irregularities
  31. 31. Gynaecological Infections • Sequelae of PID – Oophoritis – Inflammation of Ovary – Salpingitis – Inflammation of Fallopian Tubes – Endometritis – Inflammation of Endometrium – Cervicitis – Inflammation of Cervix – Vaginitis – Inflammation of Vagina
  32. 32. Gynaecological Infections • Common Micro-organisms – Gonococcus – Bacteroides – E.coli – Chlamydia – Streptococcus – Klebseilla – Enterobacter
  33. 33. Sexually Transmitted Diseases • Gonorrhoea – Neisseria gonorrhoea – A gram-negative bacteria which is a principal cause for sexually transmitted disease in males and females. – It is marked in males by urethritis with pain and purulent discharge, but is commonly asymptomatic in females, although it may extend to produce suppurative salpingitis, oophoritis, tubo ovarian abscess and peritonitis. – Affects mucus membranes of lower genitourinary tract
  34. 34. Sexually Transmitted Diseases • Chancroid – A sexually transmitted disease caused by the bacteria haemophilus ducreyi. – Causes multiple painful ulcers on the penis and the vulva often associated with tender and enlarged inguinal lymph nodes.
  35. 35. Lower Respiratory Tract Infections • Bronchitis -Inflammation of one or more bronchi • Bronchiolitis- Inflammationof the bronchioles • Pneumonia - Inflammation of the lungs parenchyma – Nosocomial Pneumonia - A type of pneumonia that is caused by bacteria contracted during a hospitalisation. These hospital-acquired infections tend to be more difficult to treat due to the bacteria's relative resistance to common forms of antibiotic therapy.
  36. 36. Lower Respiratory Tract Infections • Community Acquired Infections - Any infection acquired in the community, that is, contrasted with those acquired in a health care facility. An infection would be classified as community- acquired if the patient had not recently been in a health care facility or been in contact with someone who had been recently in a health care facility.
  37. 37. Lower Respiratory Tract Infections • Empyema – Pus in the Pleural Cavity • Bronchiectasis - Persistent and progressive dilation of bronchi or bronchioles as a consequence of inflammatory disease (lung infections), obstruction (tumour) or congenital abnormality (cystic fibrosis). – Symptoms include fetid breath and coughing, with the expectoration of mucopurulent matter.
  38. 38. Lower Respiratory Tract Infections • Emphysema - A pathological accumulation of air in tissues or organs, because of permanent distension of the air spaces in the portion distal to the terminal bronchiole. Wheezing sound. • Cystic Fibrosis - A generalised disorder of infants, children and young adults, in which there is widespread dysfunction of the exocrine glands, characterised by signs of chronic pulmonary disease (due to excess mucus production in the respiratory tract). There is an ineffective immunologic defense against bacteria in the lungs.
  39. 39. Lower Respiratory Tract Infections • Common Micro-organisms – S aureus – S pneumoniae – Mycobacterium – Mycoplasma
  40. 40. Gastrointestinal Infections • Typhoid Fever – An infectious illness usually spread by contamination of food, milk or water supplies with Salmonella typhi, either directly by sewage, indirectly by flies or by faulty personal hygiene. – Fever, diarrhoeal stools (often bloody), abdominal pain, malaise and a rose coloured rash on the upper abdomen are seen.
  41. 41. Gastrointestinal Infections • Cholecystitis - Acute or chronic inflammation of the gallbladder • Cholangitis - Inflammation of a bile duct • Peritonitis- Inflammation of the peritoneum, a condition marked by exudations in the peritoneum of serum, cells and pus. • Intra-Abdominal Abscess -A localised pus- forming bacterial infection that occurs within the abdominal cavity as the result of a perforated viscus or post operative complication.
  42. 42. Gastrointestinal Infections • Visceral abscess – Abscess in any abdominal organ – Hepatic Abscess – Splenic Abscess – Pancreatic abscess – Renal Abscess
  43. 43. Gynaecological Infections • Common Micro-organisms – Gonococcus – Bacteroides – E.coli – Chlamydia – Streptococcus – Klebseilla – Enterobacter
  44. 44. Bone & Joint Infections • Osteomyelitis - Inflammation of bone caused by a pyogenic organism. It may remain localised or may spread through the bone to involve the marrow, cortex and cancellous tissue
  45. 45. Bone & Joint Infections • Common Micro-organisms – S. aureus – Salmonella – S pyogenes
  46. 46. Skin & Soft Tissue Infections • An abscess, also called a boil or furuncle, appears as a warm, painful swelling under the skin. A carbuncle forms when several abscesses cluster together under the skin. These conditions can make you feel sick and cause a fever. • Cellulitis is an infection that spreads under the skin. It causes redness, swelling, and pain over a patch of skin and can cause fever, chills, and headaches. It is commonly seen on facial skin and the legs. • Impetigo causes sores that are itchy and slightly painful. Sometimes it appears as a large fluid-filled blister. The sores leak fluid and form yellow crusts that look like scabs. Impetigo can spread to other people and to other parts of your body.
  47. 47. Skin & Soft Tissue Infections Wound infections occur when a cut or break in the skin allows bacteria to enter the body.
  48. 48. Skin & Soft Tissue Infections • Skin ulcers, also called pressure sores or bedsores, are areas of damaged skin caused by a lack of blood flow. The lack of blood flow is caused by long periods of pressure, usually from being confined to a bed or chair and not being able to change position easily. A bacterial infection of skin ulcers can slow healing and even be life- threatening if it spreads in the body. • Deep wound infections can occur as a result of deep cuts, bites, injuries that break the skin, and incisions (cuts) that are made during some types of surgery. • Uncomplicated infections can become more severe. For example, a major abscess and cellulitis may grow into deeper tissue and require surgical treatment.
  49. 49. Skin & Soft Tissue Infections
  50. 50. Skin & Soft Tissue Infections • Common Micro-organisms – Staphylococcus aureus – Streptococcus pyogenes
  51. 51. Post Operative Infections • PO Wound Infections
  52. 52. Antimicrobial Agent And Chemotherapy • Chemotherapy is the treatment of disease with chemical agents. •Antibacterial or Antimicrobial agent is the drug used against micro-organisms. • An Antiseptic is usually applied to external surfaces such as skin e.g. iodine. • A Disinfectant is used to sterilize instruments commonly used for surgery e.g.carbolic acid.
  53. 53. Antimicrobial Agent And Chemotherapy • Chemotherapeutic Agents are chemical substances synthesized in the laboratory which can kill (bactericidal) or inhibit (bacteriostatic) the growth of the organisms. • Antibiotics are substances that are derived from micro-organisms which inhibit the growth of or kills other micro-organisms e.g. penicillin and it’s derivatives Ampicillin, Amoxycillin, Cephalosporins.
  54. 54. Antibiotic Terminology • Bacteriostatic :- A bacteriostatic antibiotic is one that is able to inhibit the growth or multiplication of bacteria. • Bactericidal :- A bactericidal antibiotic is one that is able to kill bacteria usually when they are in the process of multiplication. • M.I.C. :- (Minimum Inhibitory Concentration) It is the smallest amount of antibiotic required to inhibit or suppress the growth of the bacteria.
  55. 55. Antibiotic Terminology • M.B.C. :- (Minimum Bactericidal Concentration) It is the smallest amount of antibiotic required to destroy or kill bacteria. • Resistance :- Bacteria that are not susceptible to a particular antibiotic are said to be resistant to that antibiotic. • Cross Resistance :- Bacteria that are resistant to one antibiotic and also demonstrate resistance to another different antibiotic are said to show cross resistance. (This is normally present in antibiotics which a similar structure). • Spectrum :- The range of bacteria against which an antibiotic is effective is called the antibacterial spectrum of that antibiotic.
  56. 56. Classification of Anti-microbial Agents A) Chemical Structure 1. -Lactam Antibiotics : Penicillins, Cephalosporins, Monobactams, Carbapenems 2. Tetracyclines : Oxytetracycline, Doxycycline etc. 3. Aminoglycosides : Streptomycin, Gentamycin, Neomycin etc. 4. Macrolide Antibiotics : Erythromycin, Oleandomycin, Roxithromycin 5. Quinolones : Nalidixic acid, Norfloxacin, Ciprofloxacin, Pefloxacin 6. Imidazole Derivatives : Miconazole, Ketoconazole, Clotrimazole, Fluconazole
  57. 57. Classification of Anti-microbial Agents B) Mechanism of Action 1. Inhibit Cell Wall Synthesis : Penicillins, Cephalosporins, Cycloserine, Vancomycin, Bacitracin. 2. Inhibit Protein Synthesis : Tetracyclines, Chloramphenicol, Erythromycin, Clindamycin 3. Interfere With DNA Function : Rifampin, Norfloxacin, Metronidazole 4. Causing Leakage from Cell Membranes : Amphotericin B, Nystatin
  58. 58. Classification of Anti-microbial Agents C) Spectrum of Activity 1. Antibacterial : Pencillins, Aminoglycosides, Erythromycin etc. 2. Antifungal : Griseofulvin, Amphotericin B, Ketoconazole etc. 3. Antiviral : Idoxuridine, Acyclovir, Amantadine, Zidovudine etc. 4. Antiprotozoal : Chloroquine, Pyrimethamine, Metronidazole, Diloxanide etc. 5. Anthelmintic : Mebendazole, Piperazine, Pyrantel pamoate etc.
  59. 59. Classification of Anti-microbial Agents D) Type of Action Primarily Primarily Bacteriostatic Bactericidal Sulfonamides Penicillins Cephalosporins Tetracyclins Aminoglycosides Vancomycin Chloramphernicol Polypeptides Nalidixic acid Erythromycin Rifampin Ciprofloxacin Ethambutol Cotrimoxazole Idoniazid
  60. 60. Classification of Anti-microbial Agents E. Source Fungi Bacteria Penicillin Polymyxin B Cephalosporin Colistin Griseofulvin Bacitracin Tyrothricin Aztreonam
  61. 61. Selection of an Anti-microbial Agent • Clinical evaluation of the probable etiology • Identification of the causative micro-organism and antimicrobial drugs. • Nature of the drug • Severity of the disease and general condition of the patient • Risk of toxicity of the drug • Age of the patient • Pregnancy and neonatal period • Possibility of drug resistance • History of previous allergic reactions • Cost of the therapy
  62. 62. Tissue and Cell Penetration –Success of antimicrobial therapy depends on the concentration of antibiotics that reaches the site of infections –Tissue Penetration is the amount of drug found in tissue cells and interstitial fluid
  63. 63. Combination of Antibiotics • Normally, single antibiotics are used • Combination therapy is necessary in patients with mixed or life-threatening infections
  64. 64. Why are Antibiotics Combined? • To achieve an additive or synergistic effect against a single organism • In mixed infections with bacteria sensitive to different drugs • To delay the development of resistance • To decrease the adverse reactions of an individual drug so that the dose of a drug can be reduced • When the infection is severe and the body defence is poor
  65. 65. Beta-lactam Antibiotics • The discovery of Penicillin by Alexander Fleming in his London Hospital Laboratory in 1928 was a milestone in the battle between human and microbes • Penicillins, Cephalosporins – A boon to mankind
  66. 66. Drug enters the bacterial cell Binds to Penicillin Binding Proteins No transpeptidase production MECHANISM OF No crosslinking of peptidoglycan chain ACTION OF PENICILLINS Weak bacterial cell wall Lysis of the bacteria
  67. 67. Beta-lactam Antibiotics -Penicillins • Penicillin G, Penicillin V • Penicillinase-resistant Penicillins – Methicillin, Cloxacillin • Aminopenicillins –Ampicillin, Amoxycillin • Antipseudomonal Penicillins - Ticarcillin
  68. 68. Beta-lactam Antibiotics - Cephalosporins • Cephalosporins appear to inhibit bacterial cell wall synthesis in a manner similar to that of penicillins. Structurally they are closely related to penicillins and belong to the same class of b-lactam antibiotics • First – Generation Cephalosporins Cefzolin, Cephalexin, Cefadroxil These cephalosporins have good activity against gram-positive bacteria but poor activity against gram-negative bacteria.
  69. 69. Beta-lactam Antibiotics – Cephalosporins Second – Generation Cephalosporins • Cefuroxime, Cefoxitin, Cefaclor, • The second generation cephalosporins have increased activity against gram-negative micro-organisms.
  70. 70. Beta-lactam Antibiotics - Cephalosporins Third Generation Cephalosporins • Cefotaxime, Ceftazidime, Cefoperazone, Ceftizoxime, Ceftriaxone, Cefpodoxime • Cefixime-oral • These antibiotics generally have increased potency and a wider spectrum of activity against clinically important gram-negative bacteria. But they are less potent than the first generation agents against gram-positive bacteria.
  71. 71. Beta-lactam Antibiotics - Cephalosporins Fourth Generation Cephalosporins Cefepime is considered a fourth generation cephalosporin due to it's intrinsic antimicrobial properties. Fourth generation cephalosporins are projected to have many attributes including:  extended spectrum of activity for gram negative and gram positive organisms (different from third generation cephalosporins)  minimal Beta-lactamase activity due to rapid periplasmic penetration and high penicillin-binding protein (PBP) access  spectrum of activity to include gram negative organisms with multiple drug resistance patterns (Enterobacter and Klebsiella)
  72. 72. The basic mechanisms by which micro-organisms may become resistant to beta-lactams includes: 1. Beta-lactamses 2. Permeability Resistance 3. Changes in Penicillin Binding Proteins (PBP) 4. Mixed Mechanism of Resistance
  73. 73. Beta-lactamase Mediated Resistance • Beta-lactamases are enzymes that recognize and attack beta-lactam ring of the antibiotics • Penicillins are hydrolysed into bacteriologically inactive penicilloic acid • Intact antibiotic never reaches its target proteins in the bacterial cell wall • Ability to produce these enzymes is now widespread in bacteria
  74. 74. Approaches to Overcome Beta- lactamase Resistance • Development of entirely new class of antibiotics. Eg: Quinolones • Development of new beta-lactam antibiotics resisting hydrolysis by beta- lactamase. Eg: New Cephalosporins • Development of Beta-lactamase inhibitors. Eg: Sulbactam and Clavulanic acid
  75. 75. Beta-lactamase Inhibitor • Sulbactam – Binds irreversibly to the beta-lactamase enzymes – Effective against Class A & C of beta-lactamases • Clavulanic Acid – Binds irreversibly to the beta-lactamase enzymes – Induces production of beta-lactamase in some organisms – Effective against Class A of beta-lactamases
  76. 76. Macrolides • Macrolide antibiotics, include – Azithromycin – Clarithromycin – Dirithromycin – Erythromycin – Roxithromycin
  77. 77. Quinolones • Quinolones include – Nalidixic Acid – Norfloxacin – Ciprofloxacin – Sparfloxacin – Lomefloxacin – Ofloxacin – Gatifloxacin – Moxifloxacin – Pfloxacin
  78. 78. 3 Ds of Appropriate Antibiotic Use • The Right Drug. Use only the antibiotic that your healthcare professional prescribed for your condition, and not one used by another person or for another illness. • The Right Dose. Take the prescribed amount of your drug at the correct times. • The Right Duration. Even if you start to feel better, continue taking your drug for the full course (the prescribed number of days) to ensure that no bacteria can survive.