Lecture 7 Medical Bacteriology Part II PDF

# Lecture 7: Medical Bacteriology (II) **جامعة المعرفة** - **ALMAAREFA UniversitTY** **كلية الطب** - **COLLEGE OF MEDICINE** **Microbiology & Immunology Unit** **Dr. Rasha Mokhtar Elnagar** **M.B.B.C, MSc, PhD, MD Medical Microbiology and Immunology** **Associate Professor of Medical Microbiology...

# Lecture 7: Medical Bacteriology (II) **جامعة المعرفة** - **ALMAAREFA UniversitTY** **كلية الطب** - **COLLEGE OF MEDICINE** **Microbiology & Immunology Unit** **Dr. Rasha Mokhtar Elnagar** **M.B.B.C, MSc, PhD, MD Medical Microbiology and Immunology** **Associate Professor of Medical Microbiology & Immunology** **Consultant Microbiology & Immunology** ## 1. Gram Positive Bacilli - **Spore formers** - **Aerobes:** - Bacillus anthracis - Bacillus cereus - **Anaerobes:** - C. perfringens - C. Tetani - C. botulinum - C. difficile - **Non-spore formers** - Corynebacterium - Lactobacillus ## 1-Spore formers Gram Positive Bacilli ### 1-Genus Bacillus: - **Morphology:** Gram-positive, spore-forming, aerobic or facultative anaerobic bacilli. - **Important species:** - Bacillus anthracis (Polypeptide capsule) - Bacillus cereus - **Both species are exotoxin producers.** ## Diseases: - **1- B. anthracis:** (Zoonotic disease) - **1- Cutaneous anthrax:** Spore germination in skin form malignant pustule. - **2- Pulmonary anthrax:** (Wool sorter's disease) - **3- Intestinal anthrax.** - **2- Bacillus cereus:** - Food poisoning due to Exotoxin (Enterotoxins). ## 2- Genus Clostridium: - **Morphology:** Gram-positive, spore-forming, obligate anaerobic, bacilli. - **Important species:** All species are exotoxin producers - Clostridium tetani: (motile) - Clostridium botulinum (motile) - Clostridium perfringens: (non-motile) - Clostridium difficile ## Culture conditions: - **Obligate Anaerobes:** - Blood agar in anaerobic jars or anaerobic incubators. - Cooked meat media (anaerobic condition). ## Diseases: - **1- Clostridium tetani:** Tetanus - Tetanus neurotoxin Spastic muscle paralysis. - **2- Clostridium perfringens:** - Gas gangrene (myonecrosis): post trauma. - **3- Clostridium botulinum:** Botulism (Shellfish, Salted fish, Canned food): - Botulinum neurotoxin Flaccid muscle paralysis. - **4- Clostridium difficile:** - Antibiotic-associated diarrhea - Diarrhea & pseudomembranous colitis due to long-term antibiotic therapy. ## 2- Non-Spore formers Gram Positive Bacilli ### Genus Corynebacterium: - **Morphology:** Gram positive bacilli with club shaped ends, arranged in Chinese-letter arrangement. - **Important species:** Corynebacterium diphtheria - Produces exotoxin. ## Culture conditions: - Grow on Löffler's medium, aerobic, at 37°C. ## Disease: - Diphtheria: upper respiratory tract infection. ## 2. Gram Negative Bacilli - **Rod shaped (Enterobacteriaceae)** - **Lactose fermenter** - **Motile:** - E. Coli - **Non-Motile:** - Klebsiella - **Non-Lactose fermenter** - Salmonella - Shigella - Proteus - **Curved** - Vibrio cholera (Comma shaped) - H. pylori - Campylobacter - **Coccobacilli** - Brucella - Haemophilus ## 1-Enterobacteriaceae: - Gram negative bacilli. - Facultative anaerobes. ## Enterobacteriaceae - **Lactose fermentation** - **Positive** - **Motile:** - E. Coli - **Non Motile:** - Klebsiella - **Negative** - **Motile:** - Salmonella - **Non Motile** - H2S negative - Shigella - **Urease positive:** - Proteus - **H2S positive:** - Salmonella ## Example of diseases caused by Enterobacteriaceae: - **1- E. coli:** motile - Urinary tract infection - Neonatal meningitis - **2-Klebsiella:** non-motile - Urinary tract infection - Pneumonia - Bacillemia - **3- Proteus:** - Urinary tract infection - **4-Salmonella:** - Enteric fever (Typhoid and paratyphoid) - Food poisoning - Septicemia - **5-Shigella:** - Bacillary dysentery (Bloody diarrhea). ## 2- Curved Gram-negative bacilli ### 1. Vibrio cholerae - **Morphology:** Gram-negative comma-shaped, motile bacilli. ## Culture conditions: - Alkaliphilic: grow on alkaline media like alkaline peptone water. ## Disease: Cholera (Rice water diarrhea). ### 2. Helicobacter pylori - **Morphology:** Gram negative curved, motile bacilli. ## Culture conditions: - Microphilic, Acidophilic. ## Disease: Peptic ulcer. ## 3 - Coccobacilli ### 1. Brucella: - Gram-negative coccobacilli. - Capnophilic (5-10% CO2). Zoonotic disease: Malta fever (undulating fever). - **Important species:** - Brucella melitensis: in goats and sheep - Brucella abortus: in cows and cattle ### 2. Haemophilus influenzae: - Cause meningitis, pneumonia in infants. - Grow on Chocolate agar, need 2 growth factors: - X= hemin & V= NAD ## Pseudomonas aeruginosa - **Morphology:** Gram-negative rod (pleomorphic), motile, obligate aerobes ## Diseases caused by P. aeruginosa - Urinary tract infections - Bacteremia - Bone and joint infections - Particularly in patients with severe burns and immunosuppressed patients. ## Spirochetes: Treponema pallidum - **Morphology:** - Spiral shape, motile (endoflagella). - Difficult to be seen by Gram stain - Can be stained by Giemsa and Silver stain. - Dark Field microscope: motility. - Cannot be cultured. ## Disease: - Syphilis (sexually transmitted disease). ## Genus Mycobacterium - **Morphology:** - Acid-fast, non-motile, non-spore forming bacilli. - Cannot be stained by Gram stain due to the presence of waxy lipid in cell wall (mycolic acid). - **Image of cell wall:** - Mannan caps - Manno-glycoproteins - Mycolic acids - Lipomannan - Arabinogalactan - Peptidoglycan - PIM - Cell membrane - Porins - **Important species:** - **1- Mycobacterium tuberculosis:** Pulmonary tuberculosis - Chronic cough, night fever and sweating. - **2- Mycobacterium leprae:** Leprosy. ## Commensal bacteria (normal flora) (Human microbiome): - Normally inhabit the human body. - Mostly bacteria but may be fungi as Candida. - Do not cause disease in immuno-competent individuals. ## o Beneficial Role of Normal Flora - Compete for nutrients and attachment sites. - Produce antimicrobial substances. - Bacterial colonization of a newborn acts as a powerful stimulus for the development of the immune system. - Gut bacteria provide important nutrients. - Lactobacilli in the vagina keep acidic pH of the vagina. ## Harmful Effects of Normal Flora ## Can cause infections in the following conditions: - Immunocompromised individuals. - Change of their normal site in the body to another site: (S. epidermidis, into the bloodstream where it can colonize catheters and artificial joints). - Change in the number of normal flora (due to antibiotics overuse) leads to: - In colon: Depletion of normal flora led to overgrowth of pathogenic Clostridium difficile, causing severe pseudomembranous colitis. - In vagina: Depletion of Lactobacilli lead to overgrowth of other pathogens as Candida causing vaginal candidiasis.. ## Distribution of Normal Flora in the Body - **Skin:** - Staphylococcus epidermidis (90%) & Staphylococcus aureus. - Propionibacterium acnes reside in hair follicles and sebaceous glands. - **Nose:** The same skin normal flora. - **Eye:** Staphylococcus epidermidis, Staphylococcus aureus & Moraxella catarrhalis. - **Mouth:** Streptococcus mutans, Lactobacillus & Candida spp. - **Intestinal tract:** E. coli, Klebsiella, Enterococcus faecalis & Candida. - **Female Vagina:** Lactobacillus & Candida albicans, Streptococcus agalactiae. ## Pathogenicity of microorganisms - **Source of Infection** - The environment: soil, air & water. - Animals: zoonotic diseases. - Humans: - Case: patient. - Carrier: person carrying the pathogen without having the disease→ dangerous source of infection as not known to others. ## Mode of Transmission= Routes of Infection (SDL) - **Contact:** - Direct: hand to hand, body secretions, Sexual - Indirect: through contaminated surfaces or objects. - Airborne: - Droplet: - Ingestion: fecal-oral: - Bloodborne: - Arthropod-borne (by insects): - From mother to fetus: - Tran placental transmission - Vertical - **SDL Source:** - Amboss - Centers for Disease Control and Prevention (CDC) ## Case study A 25-year-old woman presents to the clinic with dysuria. On physical examination she is afebrile, has normal vital signs, and has mild tenderness in the midline above the pubis. Her urine analysis shows too many pus cells. Microscopic examination of urine samples showed Gram negative bacilli. She was diagnosed as urinary tract infection. Which of the following is the most likely cause of this case? A. Staphylococcus aureus B. Neisseria gonorrhoeae C. Escherichia coli D. Mycobacterium tuberculosis ## Reference - Lippincott Illustrated Microbiology 4th edition, Chapters: 10, 12-15 &18. ## Thank You