Lecture 9 Flashcards
Pathogenic Organism types
Bacteria, Viruses, Fungi
Bacteria types
Chlamydiae, Rickettsiae and Ehrlichiae, and Mycoplasma
Classification of Bacteria
Shape and arrangement(coccus, bacillus, spiral), Gram strain reaction (Gram-positive and Gram-negative), Biochemical and growth characteristics (Aerobic and anaerobic, spore formation, and biochemical profile), Antigenic structure (antigens in the cell body, capsule, flagella (motility)
Bacteria Genomic Sequence
16S ribosomal RNA, proteins and peptides are seen
Coccus (Spherical) Bacteria
Clusters: Staphylococci
Chains: Streptococci
Pairs: Diplococci
Kidney bean-shaped (in pairs: Neisseriae)
Bacillus (rod-shaped) Bacteria
Square ends: Bacillus anthracis (anthrax)
Rounded ends: Mycobacterium tuberculosis (TB)
Club shaped: Corynebacterium (Diptheria)
Comma shaped: Vibrio (Cholera)
Spiral Organisms
Tightly coiled: Treponema pallidum (Syphilis)
Relaxed coil: Borrelia (Lyme)
Steps of Gram-Staining
Step 1: Crystal violet (purple dye) – stains peptidoglycan
Step 2: Gram iodine (acts as a mordant)
Step 3: Alcohol or acetone (rapid decolorization)
Step 4: Safranin (red dye)
How do gram positives stain?
Resists decolorization and retains the purple stain (cell wall is composed of multiple peptidoglycan layers combined with teichoic acid; lipopolysaccharide absent)
How do gram negatives stain?
Can be decolorized and stained red (the cell wall is composed of a thin peptidoglycan layer and lacks teichoic acid; lipopolysaccharide present)
True or False: All bacteria can be stained
False; Mycobacterium has no cell wall and is unable to be stained
Cocci Gram-Positive
Staphylococci, Streptococci, Pneumococci
Cocci Gram-Negative
Gonococci and Meningococci
Bacilli Gram-Positive
Corynebacteria, Listeria, Bacilli, Clostridia (Oxygen and spore forming)
Bacilli Gram-Negative
Haemophilus, Gardnerella, Francisella, Yersinia, Brucella, Legionella, Salmonella, Shigella, Campylobacter, Cholera bacillus, Colon bacillus (E. coli + related organism)
Spiral organisms (Gram-Negative only)
Treponema pallidum and Borrelia burgdorferi
Acid-fast organisms (Gram-Positive only)
Tubercle bacillus and Leprosy bacillus
Staphylococci
Gram-positive cocci in Grapelike clusters found in the skin (epidermis) or the nasal cavity (aureus); normally not pathogenic but opportunistic
Staphylococci pathogenic strains cause
Vomiting and diarrhea, toxic necrosis, tissue necrosis, hemolysis, inflammation (distinguished by culture on blood agar plates)
Staphylococci Infections
Impetigo, boils, nail infection, cellulitis, surgical wound infection, eye infection, postpartum breast infections, Abscess
A drug-resistant strain of Staphylococci
Methicillin-resistant Staphylococcus aureus, or MRSA (antibiotic-resistant)
Streptococci are found…
Gram-positive cocci arranged in chains or pairs, normal inhabitants of skin, mouth, pharynx (Streptococcus viridans), gut, female genital tract (peptostreptococci); opportunistic organisms
Streptococci Diseases
3 types: pyogenic, toxigenic, and immunologic
Pyogenic Streptococci Diseases
Pharyngitis, cellulitis, endocarditis, urinary tract infection