Medical Microbiology Lecture (11) 2024 PDF

Lecture (11) Medical Microbiology (Overview of Some Bacterial Infections) Asst. Professor Dr. Arshad M. Abdullah 1 Learning Outcomes of Lecture (11): Gram-Negative Cocci: - Neisseria gono...

Lecture (11) Medical Microbiology (Overview of Some Bacterial Infections) Asst. Professor Dr. Arshad M. Abdullah 1 Learning Outcomes of Lecture (11): Gram-Negative Cocci: - Neisseria gonorrhoeae (causes gonorrhea) Spiral-shaped Bacteria: - Helicobacter pylori Comma-shaped Bacteria: - Vibrio cholerae (causes cholera) Pleomorphic bacteria: Mycoplasma: - Mycoplasma pneumoniae Chlamydia: - Chlamydia trachomatis (sexually transmitted infections) 2 Neisseria gonorrhoeae Common Name: Gonorrhea or Gonococcus. Gonorrhea is a sexually transmitted infection caused by the bacterium Neisseria gonorrhoeae. It is transmitted through sexual contact (including oral or vaginal intercourse). Neisseria gonorrhoeae 3 Characteristics of Neisseria gonorrhoeae: Gram-negative: pink or red color in Gram stain. Diplococci: in paired and Coffee-bean Shape. Aerobic: grows best in the presence of oxygen. Size: 0.6 -1.0 µm. 4 Pathogenesis of Neisseria gonorrhoeae: Transmission: Sexual contact and Vertical transmission during childbirth. Virulence Factors: Pili and Fimbriae: Essential for attachment to host cells. Outer Membrane Proteins (OMP): Help evade immune response. IgA Protease: an enzyme that breaks down IgA antibodies to evade mucosal immunity. Lipooligosaccharide (LOS ): Endotoxin that contributes to inflammation. 5 Clinical Manifestations of Neisseria gonorrhoeae: In Men: Painful urination (dysuria), Yellowish or greenish discharge, epididymitis. In Women: Increased vaginal discharge, Painful urination, Pelvic pain or lower. abdominal pain, Abnormal vaginal bleeding (between periods). 6 Clinical Manifestations of Neisseria gonorrhoeae: (2) Rectal Infections: Pain, itching, discharge, and sometimes bleeding. Pharyngeal Infections (Throat): Sore throat (often mild), Difficulty swallowing Neonatal infection: Eye Infection (Conjunctivitis): in newborns Eye redness, irritation, and discharge 7 Laboratory Diagnosis of Neisseria gonorrhoeae: Sample Collection: Men: Urethral swabs. Women: Endocervical swabs. Neonates: Eye swab (Conjunctival swabs). Microscopy: Gram-negative diplococci Culture: Media: Chocolate agar. Molecular Tests. 8 Prevention of Neisseria gonorrhoeae: Public Health Measures: Condom use. Partner treatment. Routine screening in high-risk populations. Neonatal Prevention : in pregnant women, Regular screening can help prevent transmission to the baby. 9 Helicobacter pylori (H. pylori) is a type of bacteria that infects the stomach. It can damage the tissue of the stomach and the first part of the small intestine (duodenum). It can also cause pain and inflammation and in some cases lead to Peptic Ulcers in the upper digestive tract. 10 Characteristics of H. pylori: Gram-negative Bacteria. Spiral-Shaped (helical) Bacteria. Microaerophilic Bacteria. Motility: Highly Motile; Flagella help colonize the gastric mucosa. Enzyme Production: Urease converts Urea into Ammonia to Neutralize Stomach Acid. 11 Pathogenesis of Helicobacter pylori: Transmission: Fecal-oral or person-to-person by saliva routes; contaminated food or water. Virulence Factors: Urease: Neutralizes stomach acid. Flagella: Facilitates movement through gastric mucus. Cytotoxin-Associated Gene A( CagA Protein): increases cancer risk Vacuolating Cytotoxin A (VacA Toxin): Causes cell damage. Lipopolysaccharides (LPS): evade from immune response. 12 Clinical Manifestations of Helicobacter pylori: 1) Acute and Chronic Gastritis: Symptoms: Epigastric pain, Nausea, Bloating. 2) Peptic Ulcer Disease: Symptoms: Burning pain, Nausea, possible bleeding. 3) Gastric Cancer: Chronic inflammation increases the risk of Cancer (adenocarcinoma). 4) Mucosa-Associated Lymphoid Tissue lymphoma (MALT lymphoma): Chronic infection stimulates lymphoid tissue in the stomach. 13 Diagnosis of Helicobacter pylori: Invasive Methods: Diagnosis by: Endoscopy with biopsy. Rapid urease test, histology, or culture. Non-Invasive Methods: Urea breath test (detects active infection). Stool antigen test. Serology: Detects antibodies but cannot differentiate active from past infections. 14 Prevention of Helicobacter pylori: Good Hygiene Practices Good Hand-washing Clean Drinking Water Safe Food Handling Health Education 15 Vibrio cholerae (V. cholerae): Cholera is an infection of the intestines caused by the bacterium Vibrio cholerae. Infection with cholera by: drinking water or eating food contaminated with cholera bacteria. The symptoms of cholera include diarrhea and vomiting of clear fluid. 16 Characteristics of Vibrio cholerae: Causative agent of cholera, an acute diarrheal disease. Gram-negative bacterium. Comma-shaped (Curved rod) bacterium. Facultative anaerobe bacterium. Motile bacterium: Single polar flagellum for motility. 17 Pathogenesis of Vibrio cholerae: Transmission: Fecal-oral route through contaminated water or food. Virulence Factors: Cholera Toxin (CT): Causes water and electrolyte secretion into intestines. Toxin- Coregulated Pili (TCP): Adheres to intestinal epithelial cells. Accessory Colonization Factor (ACF): Enhances intestinal colonization. Zonula Occludens Toxin (Zot): Disrupts intestinal tight junctions. Hemagglutinin Protease (HAP): Facilitates bacterial spread. 18 Clinical Manifestations of Vibrio cholerae: - Cholera (Severe Diarrhea): Severe watery diarrhea (rice-water stool). Dehydration, Electrolyte imbalance. - Asymptomatic or Mild Gastro-enteritis: Common in low-infective doses. 19 Diagnosis of Vibrio cholerae: Microscopy: Detection of Motile, comma-shaped bacteria in stool (dark-field microscopy). Culture: Grow on selective media. Serotyping: Detect O1 or O139 antigens using specific antisera. Molecular Tests: Polymerase Chain Reaction (PCR) to detect Toxin genes (ctxA and ctxB). 20 Prevention of Vibrio cholerae: Hygiene and Sanitation: Clean water supply, management and hand washing. Vaccination: Oral cholera vaccines (OCVs) 21 Mycoplasma pneumoniae (M. pneumoniae): Mycoplasma pneumoniae is a type of bacteria that can cause various symptoms, including dry Cough, Fever, and Mild shortness of breath. 22 Characteristics of Mycoplasma pneumoniae: Size: smallest free-living organisms (0.2-0.3 µm). Shape: Pleomorphic (varied shape). Lacks a Cell Wall: No peptidoglycan layer. Resistant to beta-Lactam Antibiotics (e.g., penicillins). Aerobic bacteria: requires oxygen to grow. Growth: Slow-growing bacteria. 23 Pathogenesis of Mycoplasma pneumoniae: Transmission: Respiratory droplets from infected individuals. Highly contagious in crowded environments. Adherence: Uses the adhesin protein (P1) to attach to respiratory epithelial cells. Toxins and Immune Response: Produces (CARDS) Community-Acquired Respiratory Distress Syndrome Toxin, causing inflammation. Triggers a strong immune response, contributing to the symptoms. 24 Clinical Manifestations of Mycoplasma pneumoniae: Respiratory Symptoms: dry cough (hallmark symptom). Fever, Sore Throat, Headache, Malaise. Extrapulmonary Manifestations: Skin: Rashes. Neurological: Meningitis, Encephalitis. Hematologic: Hemolytic anemia due to cold agglutinins. 25 Diagnosis of Mycoplasma pneumoniae: 1) Culture: Requires specialized media (e.g., Eaton’s agar). 2) Serology: Detection of Antibodies in the blood against Mycoplasma pneumoniae. 3) Molecular Tests: to detects the DNA of Mycoplasma pneumoniae. 4) Chest X-ray. 26 Epidemiology of Mycoplasma pneumoniae: Global distribution, infections common in children and young adults. More commonly during late summer and fall. Prevention of Mycoplasma pneumoniae: good hygiene and avoiding close contact with infected individuals. Isolation of Infected individuals. 27 Chlamydia trachomatis is a Gram-negative bacterium and common cause of Sexually Transmitted infections (STIs).Also causes eye infections (trachoma). Risk groups: young adults, and sexually active individuals. Morphology of Chlamydia trachomatis: Elementary body (EB): Infective, extracellular form. Reticulate body (RB): Non-infective, intracellular form. Both forms are part of bacterial developmental cycle. 28 Pathogenesis of Chlamydia trachomatis: infects the epithelial cells of the urethra, cervix, rectum, and eyes. These sites are common entry points for the bacterium due to its mode of transmission, especially via sexual contact or vertical transmission. Cycle: Elementary body (EB) enters host cell via endocytosis. Transform into Reticulate body (RB), replicate inside cells. Reticulate body (RB) mature into Elementary body , which are released to infect other cells. 29 Chlamydia undergo a unique biphasic developmental cycle 30 Transmission of Chlamydia trachomatis: Sexual transmission: Vaginal, anal, and oral sex. Vertical transmission: From mother to neonate (during childbirth). Eye contact: Leading to trachoma. Fomites: Rare, through contaminated towels or surfaces. 31 Clinical Manifestations of Chlamydia trachomatis: Urogenital Infections: Women: Abnormal vaginal discharge, Cervicitis, Pelvic inflammatory disease (PID), infertility. Men: Urethritis, Epididymitis, Prostatitis. Neonates: Neonatal Conjunctivitis, Pneumonia. 32 Diagnosis of Chlamydia trachomatis: 1) Clinical Symptoms 2) Nucleic acid amplification tests (NAATs): Detects Chlamydia DNA or RNA in urine or swab samples from genital sites. 3) Chlamydia Culture 4) Serological tests: Detects antigens and antibodies Direct fluorescent antibody (DFA): in swab samples. Enzyme-Linked Immunosorbent Assay (ELISA). 33 Prevention of Chlamydia trachomatis: - Safe sexual practices: Use of condoms. - Screening: Regular screening for sexually active individuals. - Partner notification and treatment. - Hygiene and face washing in trachoma-endemic regions. 34