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
Toxigenic Streptococci Diseases
Scarlet fever, toxic shock syndrome
Immunologic Streptococci Diseases
Rheumatic fever, glomerulonephritis (induce hypersensitivity)
Streptococci Classification
Lancefield classification groups A to V (Most significant: A, B, D)
Group A Streptococci
Many pathogenic strains (Streptococcus pyogenes): cause pharyngitis, strep throat, tissue infections (necrotizing fasciitis, gangrene)
Group B Streptococci
(Streptococcus agalactiae): Anal/Genital tract of women, neonatal transmission risk, meningitis, sepsis
Group D Streptococci
Enterococcus faecalis, Streptococcus bovis): Urinary, biliary, and cardiovascular infections – difficult to treat and Ab resistant
Beta hemolysis
Complete lysis of red cells
Non-beta hemolysis (2 types)
Alpha hemolysis: Incomplete lysis of red cells (Streptococcus pneumoniae, Strep mutans (tooth decay)
Gamma hemolysis: Nonhemolytic, no lysis
Non-pathogenic Gram-positive bacilli
Corynebacteria are found in the skin except for C. diphtheria (Ulcers in the throat and injured heart + nerve tissue)
Listeria monocytogenes (a food contaminant found in nature - can cause systemic illness leading to meningitis)
Pathogenic Gram-positive bacilli
Bacillus anthracis (Anthrax); Spores are spread through inhalation (can remain as spores) and spread rapidly in alveoli, germinate in the lymph nodes, and produce toxins (fever, chest pain, 20% fatality without treatment in days)
Bacillus anthracis (Anthrax) Treatment
Requires long courses AB treatment
Gas gangerne (Clostridium perfringens)
Contaminate wounds, proliferate in dead/necrotic muscle tissue (ferment necrotic tissue), releasing tissue-destroying toxins with systemic effects (sepsis). Toxins also cause neutrophil lysis
Tetanus (C. Tetani)
Produces neurotoxin that causes sustained muscular contractions (bone fractures), Symptoms days to weeks after exposure, Fatal due to effect on respiratory muscles
Botulism (C. botulinum)
Food poisoning from toxin ingestion of improperly cooked/ stored food, infants particularly susceptible, produces neuroparalytic toxins – pathology not caused by infection
Intestinal infection (C. Diff)
Hard to get rid of due to antibiotic resistance (broad spectrum Ab use)
Hemophilus Influenzae
Gram -ve; Variety of infections lung, CNS, Skin, blood
Yersinia pestis
Gram -ve; Plague
Salmonella, Shigella, Campylobacter
Gram -ve; Food poisoning - GI infection
Legionella (Legionnaire’s disease)
Gram -ve; severe pneumonia
Vibrio Cholerae (Cholera)
Gram -ve; severe, acute watery diarrhea
Helicobacter pylori
Gram -ve; stomach inflammation - Ulcers
E.coli
Gram -ve; Common to GI tract residents but some strains that are ingested by raw/uncooked animal products (typically can develop toxic effects including inflammation, anemia, bloody diarrhea and abdominal pain.
Spiral organisms diseases
Syphilis (Tremponema pallidium), Lyme disease, Acid-fast bacteria, and Leprosy
Lyme disease (Borrelia burgdorferi)
Transmitted though infected tick bite to spread throughout the body
3 stages:
Stage 1: circular “bulls eye” rash accompanied with flu like symptoms
Stage 2: cardio (heart palpitations), neuro (meningitis, facial paralysis) and joint pain
Stage 3: chronic arthritis and neuro deficits (memory, fatigue, insomnia)
Acid-fast bacteria
Hard to stain due to waxy coat; causes granulatomas inflammation (Macrophage infection) and TB (Mycobacterium tuberculosis) which primarily infects lungs
Leprosy (Mycobaterium leprae)
The infection leads to skin lesions, peripheral nerve damage (lack of sensation, muscle weakness, vision loss); low infectivity and pathogenicity; inflammation of Schwann cells causes most of the damage
Chlamydiae
Gram-negative, nonmotile bacteria, obligate intracellular parasites, rigid cell wall, no vaccine available for treatment
Chlamydial Diseases
Psittacosis (pneumonia): Inhalation of dried bird feces
Trachoma (Chlamydia trachomatis A, B, C): Chronic conjunctivitis, blindness
Nongonococcal urethritis (men): Spread to other areas
Cervicitis (women): Lead to salpingitis, pelvic inflammatory disease, infertility, ectopic pregnancy
Neonatal inclusion conjunctivitis: Newborn from infected mother
Rickettsiae and Ehrlichiae
Obligate intracellular parasites (typically endothelial cells)– both transmitted by insect bites and respond to some antibiotics
Rickettsia Disease
Infects, proliferates endothelial cells in small blood vessels of skin - causing damage, leakage of blood into surrounding tissues (rash and edema)
Rocky Mountain Spotted Fever (ticks)
East Coast spring and early summer; flu-like and Rash after 2 to 6 days on hands and feet then the trunk, affects CNS
Rickettsialpox (mites from mice) symptoms
flu like symptoms, full-body rash
Typhus symptoms and illnesses
Flu-like, rash (epidemic: lice; endemic: fleas, mites)
Ehrlichiosis Transmission and Symptoms
Transmitted via the bite of an arthropod vector (ticks, mites, lice, fleas), Infect and multiply in neutrophils or monocytes, Cause febrile flu-like (muscle aches, chills) illness with skin rash, Transmission enhanced by poor hygiene, overcrowding, wars, poverty
Primary atypical pneumonia (+Symptoms and treatment)
Mycoplasma pneumoniae; Most common in winter, young adults, outbreaks in groups; Cough, sore throat, fever, headache, malaise, myalgia, Resolves spontaneously in 10 to 14 days and responds to antibiotics: Tetracycline and erythromycin
Viruses’ Nucleic acid structure
Either DNA or RNA (ss,ds, +/-ve), enclosed in a capsid, with an outer envelope made of lipoprotein (often from host cell)
Virus size
Smaller than cells (20 to 300 nm diameter) and cannot be seen under a light microscope
Nucleoid
Genetic material, DNA or RNA, not both (centre of virus)
Capsid
Protective protein membrane surrounding genetic material in virus
Coat/Envelope
Surrounds the virus (combination of host membrane and viral proteins (retrovirus)) - non-enveloped viruses, adenovirus, exist
True or False: Viruses lack metabolic enzymes
True, they rely on the host’s metabolic processes for survival
Modes of action in various viruses
Invades a susceptible cell, Asymptomatic latent viral infection (HSV, VZV: Herpes Zoster/Shingles) – dormant in neural cells, Acute cell necrosis and degeneration (Ebola), Cell hyperplasia, proliferation and Neoplasia(HPV), Slowly progressive cell injury (HCV), Destruction of the immune system (HIV)
Bodily defences against viral infections
(Innate/Adaptive) formation of interferons: Broad-spectrum antiviral agent inhibits viral replication (non-specific), activates immune cells
- Cell-mediated Immunity
- Humoral defences
What do anti-viral agents do?
Block viral replication (HIV/HCV), prevent the virus from invading cells (HIV) - the best defence is a vaccination for community and personal immunity
Fungi
Plantlike organisms without chlorophyll, are obligate aerobes
Types of Fungi
Yeast (small ovoid/spherical), mold - spoilage of foods (branching/filamentous), Bread, cheese, wine, and beer production
Fungi cell wall vs. bacteria cell wall
Chitin vs. peptidoglycan
Fungi vs. bacteria cell membrane
Erogosterol and zymosterol vs. cholesterol
Fungi growth factors
High humidity (moist), heat, dark areas with oxygen supply
How can Fungi cause disease
Present in natural habitat and can cause chronic disease, become opportunistic in immunocompromised, lose regular flora due to antibiotics, cause superficial skin infections
Fungi treatment
Antifungal drugs or topical treatment in mild cases
Mucous membranes (Candida albicans)
Common in immunocompromised patients with
fungal infection on tongue, mouth, esophagus (thrush)
Aspergillus fumigatus
Spores from decaying plant matter can result in severe pulmonary and systemic disease in immunocompromised, asthma can develop
Histoplasmosis, coccidioidomycosis, blastomycosis, cryptococcosis
Inhaled spores from dust; usually acute, self limited respiratory infection, involve blood vessels in severe cases (systemic disease)
Antibiotics mechanism
Inhibits synthesis of the bacterial cell wall (leads to swelling-rupture), inhibits bacterial metabolic functions, and cell membrane(injury-death)
Penicillin family
Penicillin, methicillin, nafcillin, oxacillin, amoxicillin, ampicillin, piperacillin, ticarcillin
Cephalosporins
Cephalexin, cefoxitin, ceftazidime, ceftriaxone; vancomycin, bacitracin
Chloramphenicol
Tetracycline; macrolide; erythromycin, azithromycin, clarithromycin; clindamycin, gentamicin, netilmicin, streptomycin
Antibodies that inhibit bacterial DNA synthesis
Ciprofloxacin, norfloxacin, ofloxacin
Antibiotic Sensitivity Tests: Tube dilution
Measures the highest dilution that inhibits growth in test tube
Antibiotic Sensitivity Tests: Disk method
Inhibition of growth around the disk indicates sensitivity to antibiotic
Antibiotic Sensitivity Tests: MALDI-TOF-MS
Identification of strains with known antibiotic-resistance characteristics
What do tetracycline levels test?
Kidney Function
Adverse effects antibiotics
Toxicity, hypersensitivity (allergy), alteration of normal bacterial flora (resistance)
Development of resistant bacteria
Spontaneous mutation and Plasmid-acquired resistance
Mechanisms for circumventing effects of antibiotics
Develop antibiotic enzymes (penicillinase), Change cell wall structure (repel Ab), and change internal metabolic machinery (Ab loses function/binding)
Cause of antibiotic resistance
Over-prescribing of antibiotics, patients not finishing their treatment, poor infection control in hospitals and clinics, over-use of antibiotics in livestock and fish farming, lack of hygiene and poor sanitation, lack of new antibiotics being developed
