Introduction to Bacteriology (1).pptx for MEDICAL study

Bacteria

1. Introduction to Bacteriology

2. Objectives By the end of this lecture you should be able to: D efine bacteriology Describe the interaction of bacteria and humans list the virulence factors that make bacteria to cause disease in humans mention the different ways of classifying and identifying bacteria list the types of media used for bacterial culture list the specimens collected for bacterial isolation list bacteria of medical importance and the diseases they cause

3. Introduction Bacteriology- a branch of microbiology that focuses on the study of bacteria; its identification, classification, characterization of species and diseases they cause Bacteria- single celled living organisms with no membrane bound organelles no nuclear membrane, mitochondria, golgi bodies or endoplasmic reticulum Reproduce asexually by binary fision

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5. Bacteria composition Cytoplasm containing; Ribosomes Plasmids RNA DNA Proteins Cell wall; Gram + (1 cell membrane) or Gram – (2 cell membranes) Flagella Pilli Capsule

6. Bacteria and Humans The human body provides suitable conditions for bacterial growth; nutrition, warm temperature and moisture Bacteria can be either pathogenic or commensal Bacteria have traits that allow them to: enter and invade the human body live, adhere or colonize the body get food through degradation of enzymes escape being cleared by host immune or non immune protective responses

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8. Definitions Pathogenicity - ability of an infectious agent to cause disease. Virulence - degree of pathogenicity Infection - multiplication of an infectious agent within the body Toxigenicity - ability of an infectious agent to produce a toxin that contributes to the development of disease

9. Cont … Invasion - The process whereby parasites, bacteria, fungi and viruses enter the host cells and tissues and spread in the body Pathogen - an organism capable of causing disease Non-pathogen - a microorganism that does not cause disease. It may be part of the normal flora Opportunistic pathogen - An agent capable of causing disease only when the host’s resistance is impaired e.g. when a patient is immunocompromised.

10. Bacteria Virulence factors Toxins Adhesion pili Capsule Enzymes Bi products of growth(gas, acids) Super antigen I nduction of excess inflammation E vasion of phagocytic and immune clearance C apsule R esistance to antibiotics

11. Cont … Classification of bacteria Kingdom- Phylum- Class- Order- Family- Genus-Species Bacteria are named using the Genus and Species name E.G Staphylococcus- Genus (capitalized ) aureus-Species (NOT capitalized ) Italicized Handwritten should be underlined separately Staphylococcus aureus

12. Methods of classifying bacteria Morphological True bacteria: spherical (cocci) and rod (bacilli) Actinomycetes : Rigid organisms like true bacteria exhibit branching and tend to form filaments Spirochaetes: These are relatively longer, slender , non-branched microorganisms of spiral shape having several coils Mycoplasmas: lack in rigid cell wall Rickettsiae and Chlamydiae : Small, obligate parasites Anatomical Capsule: Capsulate and non capsulate Flagella: Aflagellate and flagellate Spores: spore forming and non spore forming

13. Cont … Staining reaction Gram stain: Gram positive and Gram negative Acid fast stain: Acid fast and non acid fast Cultural characteristics Colony morphology Extra growth requirements: Fastidious and non fastidious Hemolysis on sheep blood agar: Alpha and beta hemolysis Utilization of carbohydrates Growth rate: Rapid growers and slow growers Pigment production: Pigment producer and non pigment producer

14. Cont … Environmental factors Temperature Psychrophiles (15-20ᴼC)- Pseudomonas flourescens Mesophiles (20-40ᴼC)- Escherichia coli , Salmonella enterica , Staphylococcus aureus Thermophiles (50-60ᴼC)- Bacillus stearothermophilus Extremely thermophiles (as high as 250ᴼC)

15. Cont … 2. Oxygen dependence Aerobe- grow in ambient temperature, which contains 21% O2 for their growth and a small amount of CO2 0.03%) Obligate aerobes- Strictly require O2 for their growth ( Pseudomonas aeruginosa ) Facultative anaerobe (capable of growing either in presence or absence of O2)- E. coli Obligate anaerobe- Clostridium spp Capnophilic (require increased concentration of CO2, i.e 5-10%)- H. influenzae , N. gonorrhoeae Aerotolerant : Cannot use oxygen for growth but tolerate its presence

16. Cont … 3. pH Acidophiles - Lactobacillus acidophilus Alkaliphiles - Vibrio Neutralophiles ( Ph 6-8 ) Majority of the medically important bacteria grow best at neutral or slightly alkaline reaction (pH 7.2-7.6)

17. Cont … 4. Salt concentration Halophiles Non-halophiles Biochemical reactions: Lactose fermenter/ non lactose fermenter, catalase positive/ catalase negative Motility: Motile and non motile Antigenicity Genotype

18. I dentification of bacteria In order to identify bacteria, it must be grown

19. Methods of identification of bacteria Isolation in pure form Staining reaction Morphology of bacterial colony Cultural characteristics Biochemical properties

20. Gram stain 1884 Hans Christian gram Most important stain used in bacteriology Divides all bacteria into 2 groups: gram (+), purple, thin cell wall gram (-), red, thick cell wall Procedure is as follows; Take a heat fixed bacterial smear Flood it with crystal violet for 1 minute then wash with water (primary stain) Flood the smear with iodine for 1 minute then wash with water (mordant ) Flood the smear with ethanol-acetone, quickly then wash with water ( decolourizer ) Flood the smear with safranin for 1 minute then wash with water (counterstain ) Air dry the smear and observe. Examine under a microscope.

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22. Gram + ve Vs Gram – ve cell wall

23. Acid-fast staining Differential stains: the Ziehl-Neelsen stain used for mycobacteria and other acid fast organism is the oldest method used for this bacteria Procedure Prepare bacterial smear on clean and grease free slide, using sterile technique. Allow smear to air dry and then heat fix Cover the smear with carbol fuchsin stain. Heat the stain until vapour just begins to rise (about 60 ᴼC). Do not overheat. Allow the heated stain to remain on the slide for 5 minutes Wash off the stain with clean water Cover the smear with 3% v/v acid alcohol for 5 minutes Sputum smear is counterstained with methylene blue which stains the background material Wash off the stain with clean water Wipe the back of the slide clean, and place it in a draining rack for the smear to air-dry (do not blot dry ) Examine the smear microscopically, using the 100 X oil immersion objective.

24. Mtb after acid fast staining Appear pinkish from the carbol fuschin stain Background appears bluish

25. Types of media used for bacterial culture Molecular assays are now taking over culture methods but due to the high cost the latter still remains a choice diagnostic method Types of media used in bacteriology: Basic Media-this is simple media. Nutrient broth which supports growth of bacteria with no special nutritional needs enriched , non selective media- supports growth of most organisms without fastidious growth requirements Selective or specialized media- are solid media that have substances like bile salts, antibiotics which inhibit the growth of 1 organism and allow the growth of another

26. Cont … differential media: contains specific chemicals that allow the observer to visually distinguish which species possess certain biochemical properties Identification media-includes media to which chemicals or substances are added in order to help identify bacteria isolated on primary culture like peptone water, urea broth Transport media- is semi solid media that have ingredients that prevent the overgrowth of the commensals/normal flora and make sure of the survival of aerobic and anaerobic pathogens as the specimen awaits testing

27. Types of specimen collected for bacteria isolation Fecal specimen T hroat and mouth specimens E ffusions U rine P us , ulcer and skin specimens CSF Semen S putum U rogenital specimens B lood culture

28. Classification of bacteria After culture, differential stains, biochemicals and microscopy, bacteria are in the groups: gram positive cocci gram positive rods acid fast and partially acid fast rods gram negative cocci gram negative rods Anaerobes spiral shaped mycoplasma and obligate intracellular

29. Bacteria of medical importance GRAM POSITIVE COCCI Staphyloccocus aureus: Boils , skin sepsis, post-operative wound infection, catheter associated infections, food borne infection, septicemia, endocarditis, toxic shock syndrome, osteomyelitis, pneumonia Staphylococcus saprophyticus : UTI in previously healthy women-associated with intercourse Streptococcus pyogenes : infections of the upper UTI, of skin and soft tissue i.e pharyngitis, cellulitis, toxic manifestations include scarlet fever, acute glomerulonephritis and rheumatic fever are imp. complications of both skin and throat infections, streptococcal toxic shock syndrome

30. Cont … Streptococcus agalactiae : neonatal meningitis, septicemia, UTI`s, pneumonia, wound infections Streptococcus pneumoniae : Pneumonia , meningitis, septicemia, otitis and related infections in children GRAM POSITIVE RODS Corynebacterium diphtheria : diphtheria caused by toxigenic strains of C. diphtheria. Bacillus anthracis : anthrax is a significant disease in both domesticated and wild animals. it is a zoonosis and humans are usually infected by contact with the infected hides or bones

31. Cont … Clostriduim perfringes : gas gangrene resulting from infection of dirty ischemic wounds. Food poisoning following ingestion of food contaminated with enterotoxin producing strains Clostridium tetani : tetenus aka lockjaw, severe disease characterized by tonic muscle spasms and hyperflexia and convulsions Mycobacterium tuberculosis and Mycobacterium leprae : M.tuberculosis causes tuberculosis in human and animals. M.leprae is restricted to human only and causes leprosy.

32. GRAM NEGATIVE RODS Escherichia coli : UTI , diarrheal diseases, neonatal meningitis, septicemia Proteus mirabilis and Proteus vulgaris : UTI , hospital-acquired wound infection, septicemia, pneumonia in the compromised host Klebsiella : opportunist infections in the compromised (usually hospitalized) host; urinary and respiratory tracts most common sites of infection Salmonella: vast majority cause diarrheal disease. Also cause systemic disease, typhoid and paratyphoid (enteric fevers ). Vibrio cholerae : cholera, profuse watery diarrhoea Helicobacter pylori : gastritis and duodenal ulcers, associated with gastric carcinoma.

33. GRAM NEGATIVE COCCI Neisseria gonorrhoeae : gonorrhea, and pelvic inflammatory disease and salpingitis in females; ophthalmia neonatorum in infants born to infected mothers. Neisseria meningitidis : meningitis; occasionally septicemia in absence of meningitis Haemophilus influenzae : capsular type b H. influenzae  causes meningitis, osteomyelitis, epiglottitis, otitis Bordetella pertussis : whooping cough (pertussis). Treponema pallidum : causes syphilis Chlamydia trachomatis : causes trachoma (eye infection), urethritis and other infections of the genital tract, and pneumonitis in newborns, acquired during birth from infected mothers.  Chlamydia pneumoniae : important cause of atypical pneumonia. 

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