BI276 Week 12 MyLS PDF

Pathogenic Bacteria Airborne Food and water borne Direct contact Sexually transmitted infections (STI’s) Other 1 Airborne Diseases ⚫ Most involve the respiratory system ⚫ Higher concentration of bacteria inside as compa...

Pathogenic Bacteria Airborne Food and water borne Direct contact Sexually transmitted infections (STI’s) Other 1 Airborne Diseases ⚫ Most involve the respiratory system ⚫ Higher concentration of bacteria inside as compared to outside ⚫ A sneeze can contain 10,000 – 100,000 bacteria ⚫ Humans breathe about 500 millions litres of air in a lifetime 2  Airborne: Tuberculosis Mycobacterium tuberculosis (Mtb) Spread from person to person via droplets In the lungs, bacteria are engulfed by macrophages and survive Symptoms: – 4 to 12 week incubation period – Slow appearance of symptoms – Fever – Fatigue – Weight loss – Coughing – May result in expectoration of bloody sputum – Secondary infection in diseased lung tissues  Airborne: Tuberculosis Pathogenicity: – Unique toxic cell envelope components Kill eukaryotic cells and protect Mtb from lysozyme and osmotic lysis – Formation of tubercles – Calcified caseous lesion – Show up prominently in chest X-rays Tissue is dead, but may contain more pathogen 4  Airborne: Tuberculosis Treatment: – Daily doses of rifampin and isoniazid for 2 months – Followed by biweekly doses for 9 months Prevention: – Negative pressure room for infectious individuals – Facemasks with HEPA filters for health-care workers 9.4 million new diagnoses in 2009; 9029 in 2018 The incidence of tuberculosis (TB) in the United States in 2018 was 2.8 cases per 100,000 persons, which is the lowest ever reported, according to an article published in the CDC. Over 7% of cases are in HIV positive individuals; results in 5 over 50% of the deaths in AIDS patients  Airborne: Diphtheria Corynebacterium diphtheriae Nasopharyngeal secretions Exotoxin produced that inhibits protein synthesis and is responsible for pathogenesis Symptoms: – Observation of a pseudomembrane in throat – Blockage in air passage – Thick mucous and pus containing nasal discharge – Fever, Cough – Paralysis – Damage to cardiac, kidney and nervous tissues – Death (suffocation and tissue death) in 5-10% of cases 6  Airborne: Diphtheria ⚫ Diagnosis: – Observation of a pseudomembrane in throat – Bacterial and dead host cells ⚫ Treatment: – Penicillin, erythromycin, or gentamycin – Antitoxin given to neutralize exotoxin in patient’s tissues ⚫ Prevention: – Active immunization with DPT (diphtheria-pertussis-tetanus) – Acellular DTap vaccine 7  Airborne: Pertusis (Whooping Cough) Bordetella pertussis Highly contagious transmission by droplet inhalation Primarily affects children (upper respiratory tract) Symptoms: – 7- to 14-day incubation – Initially cold-like symptoms and inflamed mucous membranes – Fever – Malaise – Cyanosis – bluish skin from lack of oxygen to tissues – Followed by prolonged coughing fits with “whoop” during inhalation – Symptoms can last for up to 6 weeks – Recovery can take months 8  Airborne: Pertusis (Whooping Cough) ⚫ Pathogenicity: – Pertussis toxin most important toxin (Stops protein synthesis) – Tracheal cytotoxin, dermonecrotric toxin (Destroys epithelial tissue) ⚫ Treatment: – Erythromycin, tetracycline, chloramphenicol – Antitoxin given to neutralize exotoxin in patient’s tissues ⚫ Prevention: – Active immunization with DPT (diphtheria-pertussis-tetanus) – Acellular DTap vaccine ⚫ 2 million reported cases in 2009; 200,000 deaths in 2009 18,975 cases reported in 2017; 13,439 cases reported in 2018 (10 deaths in 2018) 9  Airborne: Meningitis Neisseria meningitidis (epidemic meningitis), Streptococcus pneumoniae, Haemophilus influenza Transmitted from person to person through droplets of respiratory or throat secretions Brain or spinal cord meninges Symptoms: – 2 to 10 day incubation period – Initial respiratory illness or sore throat – Stiff neck and back – High fever – Headaches, confusion, sensitivity to light – Death in 5-10% of cases within 24-48 hours after onset of symptoms – Brain damage, hearing loss or a learning disability in 10% to 20% 10 of survivors  Airborne: Meningitis ⚫ Pathogenicity: – Pili-mediated colonization of the nasopharynx – Cross the nasopharyngeal membrane and enter bloodstream – Proliferate within bloodstream ⚫ Treatment: – Immediate antibiotic therapy when symptoms appear – Penicillin, chloramphenicol, cefotaxime, ofloxacin ⚫ Prevention: – Vaccination ⚫ Since 1990’s, 99% decrease in US children less than 5 years old ⚫ Kept in check by herd immunity 11 Food and Water Borne Pathogens ⚫ Diarrheal diseases are the 2nd most common diseases ⚫ Leading cause of childhood death ⚫ 5 million deaths annually ⚫ 10,000 US deaths a year ⚫ Prevention and control focuses on sanitation measures 12  Food and Water: Cholera Vibrio cholerae Ingested food or water contaminated by fecal matter from patients or carriers (Infectious dose of > 105) Shellfish are natural reservoirs Symptoms: – 24-72 hours incubation period, lasting days – Massive water and electrolyte loss (dehydration) – Production of “rice-water stools” – 10-20 litres of diarrhea a day www.sciencephoto.com/images/do wnload_lo_res.html?id=662200074 13  Food and Water: Cholera ⚫ Pathogenicity: – Organisms adhere to intestinal mucosa of small intestine and secrete the cholera toxin (A/B toxin) – Toxin results in massive loss of water and electrolytes ⚫ Diagnosis: – Culture from feces with subsequent identification by agglutination reactions ⚫ Treatment/prevention: – Oral rehydration – Antibiotic therapy 14  Food and Water: Gastroenteritis (E. coli) Escherichia coli Most are non-pathogenic (commensals) Some of the most common and widely distributed pathogens Symptoms: – Develop within hours (and up to 10 days) after ingesting the bacteria. – Vomitting – Fever – Bloody diarrhea 500nm 15  Food and Water: Gastroenteritis (E. coli) Outbreaks: – Meat products – Water resources – Produce and nuts – Manufacturing and packaging Treatment/prevention: – Oral rehydration, improved sanitation – Vaccines – Antibiotic therapy (dangerous) 1. Enterotoxigenic E. coli (ETEC) – Enterotoxins and fimbriae – Enterotoxin = exotoxin released by microorganism that targets intestine – Most common cause of “traveller’s diarrhea” – Severe in the developing world – 210 million cases and 380,000 deaths occur mostly in children 16  Food and Water: Gastroenteritis (E. coli) 2. Enteroinvasive E. coli (EIEC) – Multiplies within intestinal epithelial cells – May produce a cytotoxin and an enterotoxin 3. Enteropathogenic E. coli (EPEC) – Causes effacing lesions – Caused by destruction of brush border microvilli on intestinal epithelial cells 4. Enterohemorrhagic E. coli (EHEC) – Produces effacing lesions, leading to hemorrhagic colitis – Releases shiga-like toxins – Haemolytic uremic syndrome (hemolytic anemia, acute kidney failure, low platelet count) – Leads to kidney failure E.g., E. coli 0157:H7 17 Direct Contact Diseases ⚫ Most involve skin or underlying tissues ⚫ Some can become disseminated ⚫ Numerous examples: – Yersinia pestis – Black death (Pandemic in mid-1300 that lead to death of 75-200 million people) – Staphylococcus aureus ⚫ Sexually transmitted infections (STI’s) form a large grouping 18  Direct Contact: Bacterial Disease Bdellovibrio Widespread in soil and aquatic habitats Bdello means “leech” The predator penetrates the cell wall of the prey and replicates in the cytoplasm (cannibalism) Predation is not obligatory 19  Direct Contact: Streptococcus Streptococcus pyogenes (GAS) Can be transmitted through the air (unusual) Host factors contribute to likelihood of disease Oxygenated tissue is a very rich “growth medium” Leads to disruption of erythrocytes (red blood cells) and release of hemoglobin Symptoms: – Superficial cutaneous diseases (cellulitis, impetigo-like) – Rapidly progressive – Necrotic tissue – Precipitous drop of blood pressure, failure of multiple organs, and 20 high fever  Direct Contact: Streptococcus Pathogenicity: – Necrotizing fasciitis - “flesh eating” – Myositis – Toxic shock syndrome – ~85% of GAS carry exotoxin genes (superantigens; Cysteine proteases) Treatment: – Penicillin or erythromycin – Removal of affected area (incl. amputation) 5-10% of cases are associated with necrotizing conditions 21  Sexually Transmitted Infections ⚫ Major worldwide public health problem (~300 M new cases/year) ⚫ Some also transmitted by nonsexual means ⚫ Some cured easily, others difficult or impossible to cure ⚫ Most frequent in 15–30-year age group but also others sexually active 22  Sexually Transmitted Infections: Gonorrhea Neisseria gonorrhoeae Sexual contact From mother to child during birth 62 million people, aged mainly 15 to 29, are affected worldwide (urban areas and of low socioeconomic level) Symptoms: – 3-8 day incubation period – Dissemination to joints, heart, and throat (rare) Women: Men: Pelvic inflammatory disease (PID) results Typically asymptomatic from infection of fallopian tubes and Painful urination surrounding tissue (10-20%) Discharge Ectopic pregnancies Sterility Sterility 23 Sexually Transmitted Infections: Gonorrhea ⚫ Pathogenicity: – Attach to microvilli or mucosal cells by pili and protein II adhesins – Survive phagocytosis by neutrophils – Fibrosis results and may lead to stricture or urethral closing – If pregnant, can lead to miscarriage, stillbirth, inclusion conjunctivitis, and infant pneumonia ⚫ Treatment: – Ceftriaxone or cefixime – Penicillin, tetracycline, spectinomycin and fluoroquinolone (more recently) resistance exists ⚫ Prevention: – Better education – Safe-sex – Abstinence – Antibiotic eye drops or 24 silver nitrate in newborns at birth Sexually Transmitted Infections: Syphilis Treponema pallidum ⚫Venereal syphilis – sexually transmitted ⚫Congenital syphilis – acquired in utero ⚫Can enter the lymph nodes and spreads throughout body ⚫Pathogenicity: – Largely unknown due to inability to culture organism in the lab ⚫Diagnosis: – Blood tests or seen under microscope ⚫Treatment: – Penicillin, tetracycline, 25 erythromycins or cephalosporins  Sexually Transmitted Infections: Syphilis Prevention: – Better education – Safe-sex – Abstinence – No complete immunity for infection Symptoms: – 3 to 80 days later (avg. 21) – Primary – single chancre (small, painless, reddened ulcer) at infection site and contains spirochetes – Secondary stage – highly variable skin rash followed by latent period – Tertiary stage – formation of gummas (degenerative lesions) in skin, bone, and nervous systems 26  Sexually Transmitted Infections: Chlamydia Chlamydia trachomatis Sexual contact Hand-to-eye Most common cause of newborn conjunctivitis Symptoms: Women: – Typically asymptomatic in women (routine screening for detection) – Cervix infection may produce a vaginal discharge – Can lead to pelvic inflammatory disease (scarring = sterility) Males: – Painful urination and thing urethral discharge (Experienced in 27 1/3 of males 2-6 weeks after contact)  Sexually Transmitted Infections: Chlamydia ⚫ Pathogenicity: – Inflammatory response from Chlamydial lipopolysaccharides ⚫ Treatment: – Tetracylcines, macrolides and some fluoroquinolones – Erythromycin for pregnant women ⚫ Prevention: – Better education – Safe-sex – Abstinence – No complete immunity from infection 28