Lecture 10 - Cardiovascular and Respiratory System Diseases Lecture Notes PDF

Microbes and Human Diseases: Cardiovascular and Respiratory System Diseases  Structure and Function of the Cardiovascular and Lymphatic Systems Structure Heart Blood Lymphatic system Function Circulate blood through the body’s tissue...

Microbes and Human Diseases: Cardiovascular and Respiratory System Diseases  Structure and Function of the Cardiovascular and Lymphatic Systems Structure Heart Blood Lymphatic system Function Circulate blood through the body’s tissues Deliver certain substances to cells and remove other substances from them.  Bacterial Diseases of the Cardiovascular and Lymphatic Systems Sepsis and Septic Shock Septicemia – The presence of pathogenic microorganisms or their toxins in the blood Sepsis - systemic inflammatory response syndrome (SIRS) - Gram-Negative Sepsis - Gram-Positive Sepsis -Puerperal Sepsis Signs and symptoms - fever, chills, and accelerated breathing and heart rate. Severe Sepsis - drop in blood pressure (shock) and dysfunction of at least one organ. Septic shock - A final stage, when low blood pressure can no longer be controlled by addition of fluids  Gram-Negative Sepsis Caused by gram-negative bacteria Endotoxins can cause a severe drop in blood pressure with its associated signs and symptoms. Klebsiella spp E. coli Pseudomonas aeruginosa  Gram-Positive Sepsis Staphylococci and streptococci produce potent exotoxins that cause toxic shock syndrome. The frequent use of invasive procedures in hospitals allows gram-positive bacteria to enter the bloodstream. Risk factor - patients who undergo regular dialysis Enterococci are responsible for many healthcare-associated infections Enterococcus faecium and Enterococcus faecalis are leading cause of healthcare-associated infections. Resistant to many antibiotics Group B streptococci is the most common cause of neonatal sepsis.  Puerperal Sepsis Puerperal fever and childbirth fever, is an healthcare-associated infection. Begins as an infection of the uterus as a result of childbirth or abortion. Streptococcus pyogenes is most common cause Puerperal sepsis progresses from an infection of the uterus to an infection of the abdominal cavity (peritonitis) and in many cases to sepsis. Antibiotics, especially penicillin, and modern hygienic practices have now made S. pyogenes puerperal sepsis an uncommon complication of childbirth. Lymphangitis, one sign of sepsis. As the infection spreads from its original site along the lymph vessels, the inflamed walls of the vessels become visible as red streaks.  Bacterial Infections of the Heart The wall of the heart consists of three layers - Endocardium inner layer Inflammation of the endocardium is called endocarditis. Subacute bacterial endocarditis Symptoms - fever, general weakness, and a heart murmur Caused by alpha-hemolytic streptococci (most often, Streptococcus viridans). Common after tooth extractions or tonsillectomies Left untreated by appropriate antibiotics, subacute bacterial endocarditis is fatal within a few months. Acute bacterial endocarditis Caused by Staphylococcus aureus. Streptococci can also cause pericarditis, inflammation of the sac around the heart (the pericardium).  Rheumatic Fever Caused by Streptococcus pyogenes Autoimmune complication First stage - subcutaneous nodules at joints Inflammation of the heart from a misdirected immune reaction against streptococcal M protein, damages the valves. A nodule caused by rheumatic fever Treatment - penicillin  Tularemia Zoonotic disease Transmitted by contact with infected animals Vectors - rabbits and rodents Caused by Francisella tularensis, gram-negative bacillus Penetration from the skin abrasion Lymph nodes are affected Mortality less than 3%. If left untreated, the proliferation of F. tularensis can lead to sepsis and infection of multiple organs. Treatment - antibiotics streptomycin administered for 10 to 15 days  Brucellosis Brucellosis is the world’s most common bacterial zoonosis The disease often becomes chronic and is capable of affecting any organ system. Brucella bacteria are small, aerobic, gram-negative coccobacilli. They easily become airborne and are considered dangerous to handle. They are considered a potential agent of bioterrorism. Brucella abortus found in cattle, also infects camels, bison, and several other animals. Brucella suis infect swine but is known to infect cattle when they are kept in contact with swine herds. Brucella melitensis found in goats and sheep. The incubation period is usually 1 to 3 weeks but might be much longer. Common symptoms – fever, malaise, night sweats, and muscle aches. Treated with antibiotics  Anthrax Caused by Bacillus anthracis The endospore-forming bacillus is a large, aerobic, gram-positive microorganism Endospores have survived in soil tests for up to 60 years. B. anthracis endospores are ingested along with grasses, causing a fatal sepsis. People at risk are those who handle animals Virulence factors of B. anthracis are two exotoxins Anthrax lesions  Anthrax Three forms of Anthrax Cutaneous anthrax - contact with material containing anthrax endospores. 90% cases - Endospore enters at minor skin lesion. A papule appears and then vesicles, which rupture and form an ulcerated area that is covered by a black eschar (scab). Gastrointestinal anthrax caused by ingestion of undercooked food containing anthrax endospores. Symptoms - nausea, abdominal pain, and bloody diarrhea. Ulcerative lesions occur in the gastrointestinal tract Inhalational (pulmonary) anthrax Endospores inhaled into the lungs have a high probability of entering the bloodstream. Symptoms - mild fever, coughing, and chest pain The mortality rate is exceptionally high, approaching 100%. Anthrax lesion Treatment – Antibiotics doxycycline or ciprofloxacin Prevented by vaccination Diagnosis – isolation of B. anthracis from a clinical specimen  Gangrene Ischemia – interrupted blood supply caused by wound The wound becomes anaerobic Ischemia leads to necrosis, or tissue death The death of soft tissue resulting from the loss of blood supply is called gangrene Complication of diabetes C. perfringens cause of gangrene Gas gangrene The surgical removal of necrotic tissue and amputation are the most common medical treatments for gas gangrene. Prevention - prompt cleaning of serious wounds and precautionary treatment with penicillin.  Vector-Transmitted Diseases Plague Caused by bacteria Yersinia pestis Transmitters are rats Vectors are rat flea, Xenopsylla cheopis From the flea bite, bacteria enter the human’s bloodstream and proliferate in the lymph and blood. Types of plague -Bubonic plague -Septicemic plague -Pneumonic plague Treatment - Gentamicin and fluoroquinolones are effective Diagnosis – isolation of bacteria Vaccine is available  Lyme Disease (Lyme Borreliosis) Caused by Borrelia Disease - Lyme borreliosis Reservoir – field mice and other animals Vector – tick First symptom – rash at the bite site Flulike symptoms appear in a couple of weeks as the rash fades. Treatment by antibiotics If non-effective treatment, heart is affected, irregular heartbeat. Second phase - chronic neurological symptoms, such as facial paralysis, fatigue, and memory loss may be present. The bull’s-eye rash of Lyme Third phase - develops arthritis that may affect for years. disease Diagnosis – serological tests  Viral Diseases of the Cardiovascular and Lymphatic Systems Burkitt’s Lymphoma Tumor of the jaw Caused by Epstein-Barr virus (human herpesvirus 4) Mosquito vector Treatment with anticancer drugs  Infectious Mononucleosis EB virus cause of infectious mononucleosis Childhood EB virus infections are usually asymptomatic Adulthood infection is more symptomatic because of an intense immunological response. Transmitted by saliva (kissing, sharing drinking vessels) The incubation period before appearance of symptoms (a) Large lymphocyte with the is 4 to 7 weeks unusual lobed nucleus that is The infected B cells produce heterophile antibodies that characteristic of mononucleosis. (b) Normal are used in the diagnosis of mononucleosis. lymphocyte  Cytomegalovirus Infections Cause human herpesvirus 5 Escaping antibody action by moving between cells that are in contact Transmitted by kissing, sexually, by transfused blood, and by transplanted tissue. For immunocompromised individuals, CMV is a frequent cause of a life-threatening pneumonia, but almost any organ can be affected. About 85% of AIDS patients exhibit a CMV-caused eye infection, Cytomegalovirus retinitis. Without treatment, it results in eventual loss of vision. Treatment – Ganciclovir Vaccines are under development, but none is currently available.  Classic Viral Hemorrhagic Fevers Yellow Fever Zoonotic disease Monkeys are a natural reservoir for the virus Transmitted by contact with animal Yellow fever virus is injected into the skin by a mosquito, A. aegypti Symptoms of early stages - fever, chills, and headache, followed by nausea and vomiting Late stage – jaundice, yellow color of the skin, deposition of bile pigments Mortality rate 20% There is no specific treatment for yellow fever  Classic Viral Hemorrhagic Fevers Dengue Caused by Dengue virus Transmitted by A. aegypti mosquitoes Symptoms vary from a mild case of fever to a severe, fatal disease If the patient suffers from severe bleeding and organ impairment, the case is classified as severe dengue. Mosquito abatement is necessary to control the disease  Emerging Viral Hemorrhagic Fevers Marburg virus, or green monkey virus, Filoviridae family Transmitted to people from fruit bats Human-to-human transmission occurs Early symptoms are headache and muscle pain Late symptoms are vomiting blood and bleeding Ebola Hemorrhagic fever caused by Ebolavirus, a filovirus Blood vessels are damaged, the virus interferes with coagulation, and blood leaks into surrounding tissue. Reservoir is a cave-dwelling fruit bat Symptoms include fever, fatigue, muscle pain, headache, followed by vomiting, diarrhea, rash, bleeding Treatment – monoclonal antibodies Vaccine is available  Protozoan Diseases of the Cardiovascular and Lymphatic Systems Chagas Disease (American Trypanosomiasis) Protozoan disease of the cardiovascular system Caused by Trypanosoma cruzi, a flagellated protozoan Reservoir for T. cruzi are wild animals, including rodents, opossums, and armadillos. Vector is a bug, called the “kissing bug” The acute stage, characterized by fever and swollen glands lasting for a few weeks Chronic form of the disease - damage to the nerves controlling the peristaltic contractions of the esophagus or colon can prevent them from transporting food. This causes them to become grossly enlarged, conditions known as megaesophagus and megacolon. Deaths are caused by damage to the heart, which occurs in about 40% of chronic cases. Diagnosis – detections trypanosomes in blood samples. Treatment - triazole derivatives nifurtimox and benznidazole  Toxoplasmosis Disease of blood and lymphatic vessels Caused by Toxoplasma gondii – sporeforming protozoan Reservoir are cats Sexual phase in the intestinal tract of the cat Transmitted by ingestion of contaminated food Congenital infection of a fetus, resulting in stillbirth or a child with severe brain damage or vision problems. Toxoplasmosis can be detected by serological tests. Treatment - pyrimethamine in combination with sulfadiazine and folinic acid.  Malaria Caused by Plasmodium Vector - Anopheles mosquito Symptoms chills and fever and often by vomiting and severe headache. Transmitted by blood transfusions with unsterilized syringes Four species of Plasmodium cause malaria in humans Plasmodium vivax is cause of most cases, but it is benign The most dangerous malaria is that caused by P. falciparum More red blood cells (RBCs) are infected and destroyed than in other forms of malaria. The brain is frequently affected, and P. falciparum is the usual cause of cerebral malaria. Diagnosis by examining a blood smear for infected RBCs No Vaccine available  Malaria Prophylaxis and Therapy for Malaria Prophylaxis - chloroquine is the drug of choice Mefloquine, many side effects Therapy Chloroquine, malarone or oral quinine plus an antibiotic such as doxycycline. Prevention Vector control  Leishmaniasis Caused by protozoan pathogens Leishmania species Transmitted by the bite of female sandflies Promastigote – the infective form is in the saliva of the insect Transmitted by the contact with contaminated blood from transfusions or shared needles can also lead to infection. Leishmaniasis is treated with amphotericin B Three forms of Leishmaniasis - Visceral Leishmaniasis, fatal - Cutaneous Leishmaniasis - Mucocutaneous Leishmaniasis Cutaneous leishmaniasis  Structure and Function of the Respiratory System Upper respiratory system - nose, the pharynx (throat), larynx (voice box), middle ear and the auditory (eustachian) tubes. Lower respiratory system - Trachea (windpipe), bronchial tubes, and alveoli - Oxygen and carbon dioxide are exchanged between the lungs and blood - Pleura - double-layered membrane enclosing the lungs Microbial Diseases of the Upper Respiratory System Pharyngitis - inflammation of the mucous membranes of the throat, or sore throat. Laryngitis - when the larynx is the site of infection Tonsillitis – inflammation of tonsils Sinusitis - infection of a sinus involving heavy nasal discharge of mucus. Epiglottitis - inflammation of the epiglottis  Bacterial Diseases of the Upper Respiratory System Streptococcal Pharyngitis Caused by group A streptococci Transmitted by respiratory secretions Characterized by local inflammation and a fever Tonsillitis occurs, and the lymph nodes in the neck become enlarged and tender Complication – Otitis media Diagnosis – isolation of bacteria from a throat swab  Scarlet Fever Caused by Streptococcus pyogenes erythrogenic (reddening) toxin Pinkish red skin rash, which is probably the skin’s hypersensitivity reaction to the circulating toxin, and a high fever. The tongue has a spotted, strawberry-like appearance and then, as it loses its upper membrane, becomes very red and enlarged. Treated by antibiotics  Diphtheria Caused by Corynebacterium diphtheriae, a gram-positive, non–endospore-forming rod. When the heart and kidneys are affected by the toxin, the disease can rapidly be fatal. The nerves can be involved, and partial paralysis results Vaccines are available Cutaneous diphtheria - C. diphtheriae infects the skin, at a wound or skin lesion. Antibiotics should be used only in conjunction with antitoxin.  Otitis Media Otitis media – infection of the middle ear The condition is most frequent in early childhood Microorganisms that can cause otitis media - S. pneumoniae - H. influenzae - Moraxella catarrhalis - S. pyogenes - Respiratory syncytial viruses Treatment - amoxicillin, are usually the first choice (when the cause is bacteria).  Viral Disease of the Upper Respiratory System The Common Cold Rhinoviruses (30–50%); Coronaviruses (10–15%) Symptoms include sneezing, excessive nasal secretion, and congestion. Complications - laryngitis and otitis media Microbial Diseases of the Upper Respiratory System  Bacterial Diseases of the Lower Respiratory System Pertussis (Whooping Cough) Caused by Bordetella pertussis, obligately aerobic, gram-negative coccobacillus. Virulent factor is capsule B. pertussis produces several toxins Tracheal cytotoxin is responsible for damage to the ciliated cells Pertussis toxin enters the bloodstream and is associated with systemic symptoms of the disease. Gasping for air between coughs causes a whooping sound Diagnosis – isolation of pathogen from a throat swab Treatment with antibiotics, most commonly erythromycin or other macrolides  Tuberculosis Caused by Mycobacterium tuberculosis, obligate aerobe rods M. bovis is the cause of bovine tuberculosis, which is transmitted to humans via contaminated milk or food. M. bovis infections cause TB that primarily affects the bones or lymphatic system. Mycobacterium bacteria can survive for weeks in dried sputum and are very resistant Tuberculosis is most commonly acquired by inhaling the bacillus. Bacilli reach the lungs, where they are usually phagocytized by a macrophage in the alveoli. Symptoms include coughing, sputum may become bloodstained, vessels may rupture and resulting in fatal hemorrhaging.  Tuberculosis Diagnosis - Tuberculin skin test - Chest X-ray - CT scan - Microscopic examination of smears Treated by antibiotics A positive tuberculin skin test on an arm BCG vaccine is available  Bacterial Pneumonias Streptococcus pneumoniae is the most common - typical pneumonia Pneumoniae caused by other microorganisms (fungi, protozoa, viruses, and other bacteria) - atypical pneumonia Lobar pneumonia - lobes of the lungs are infected Bronchopneumonia - alveoli of the lungs adjacent to the bronchi are infected. Pleurisy - complication of various pneumonias, in which the pleural membranes become painfully inflamed.  Pneumococcal Pneumonia Caused by S. pneumoniae - a gram-positive bacterium This microbe is also a common cause of otitis media, meningitis, and sepsis. Capsule makes the pathogen resistant to phagocytosis. Pneumococcal pneumonia involves both the bronchi and the alveoli Symptoms include - high fever, breathing difficulty, and chest pain Pneumococci can invade the bloodstream, the pleural cavity surrounding the lung, and occasionally the meninges. Diagnosis - isolating the pneumococci from the throat, sputum, and other fluids. Treatment with antibiotics Vaccine is available  Haemophilus influenzae Pneumonia Caused by Haemophilus influenzae - a gram-negative coccobacillus Gram stain of sputum will differentiate this type of pneumonia from pneumococcal pneumonia. Children under 5 and adults over 65 are most at risk for infection. Treatment with antibiotics  Mycoplasmal Pneumonia Caused by Mycoplasma pneumoniae Termed as walking pneumonia Most common in young adults and children Symptoms include low-grade fever, cough, and headache. Colonies of Mycoplasma are very small Lack of cell wall Treatment with antibiotics  Chlamydial Pneumonia Caused by Chlamydophila pneumoniae Association between C. pneumoniae and atherosclerosis, the deposition of fatty deposits that block arteries. Transmitted from person to person, probably by the respiratory route. PCR is the preferred diagnostic method because culturing the bacteria is slow and serological tests don’t distinguish species. Treatment with antibiotic azithromycin.  Respiratory Syncytial Virus (RSV) The most common cause of viral respiratory disease in infants RSV is sometimes implicated in cases of otitis media Symptoms are coughing and wheezing that last for more a week Fever occurs only when there are bacterial complications Diagnosis – serological test Vaccine is in clinical trials Monoclonal antibody, palivizumab, is recommended for prophylaxis in immunocompromised and other high-risk patients.  Influenza (Flu) Caused by Influenza Virus Hemagglutinin (HA) spikes and neuraminidase (NA) spikes HA spikes allow the virus to recognize and attach to body cells NA spikes help the virus separate from the infected cell as the virus exits after intracellular reproduction. 16 subtypes of HA 9 subtypes of NA Antigenic drift and antigenic shift Three serotypes of human influenza viruses A and B viruses cause seasonal epidemics every winter C viruses cause a mild respiratory illness Diagnosis – serological test, PCR Treatment - antiviral drugs zanamivir and oseltamivir Vaccines are available References Gerard J. Tortora, Berdell R. Funke, Christine L. Case - Microbiology_ an introduction-Pearson (2018), Chapters 23 and 24