Blood and Lymphatic Infections

1. Blood and Lymphatic Infections Chapter 28

3. A Diagram of the Circulatory System

4. Subacute Bacterial Endocarditis

5. Gram-Negative Septicemia • Causative agent • Gram (-) bacteria more likely cause of fatal septicemia • Shock is common despite treatment • Mortality rate nearly 50% due to shock and lung damage • Blood cultures from patients usually reveal • E. coli • Ps. Aeruginosa • Bacteroidessp. • Symptoms • Violent shaking chills and fever • Often accompanied by anxiety and rapid breathing • In case of septic shock • Urine output drops • Respiration and pulse become more rapid • Arms and legs become cool and dusky colored

6. Gram-Negative Septicemia • Pathogenesis • Generally originates outside of bloodstream • Endotoxin is released • Antibiotics can enhance endotoxin release • Exaggerated response Macrophage response to endotoxin • Failed localization allows endotoxin into bloodstream • Causes cascade of harmful events • Lungs particularly susceptible to irreversible damage • Often results in death despite successful treatment of infection

7. Gram-Negative Septicemia • Epidemiology • Mainly a nosocomial disease • General trend • increased life span • antibiotic suppression of normal flora • use of immunosuppressive drugs • biofilm formation of medical devices • Prevention and Treatment • Identification and effective treatment of localized infections • Treatment against causative organisms

8. Tularemia (Rabbit Fever) • Causative agent • Francisella tularensis • Non-motile, aerobic, Gram (-) rod • Symptoms • Characterized by development of skin ulcerations and enlargement of regional lymph nodes • Flu-like • Symptoms usually abate in 1 to 4 weeks • Sometimes may become chronic

9. Tularemia (Rabbit Fever) • Pathogenesis: 90% of infected individuals survive in the absence of treatment • Causes ulcer at entry sight • Lymphatic vessels carry organism to regional lymph nodes • Become large, tender and filled with pus • Spread to other body sites via lymphatics and blood vessels • Pneumonia occurs in 10% - 15% of lung infections • Multiplies within phagocytes • Cell mediated immunity responsible for ridding infection

10. Tularemia (Rabbit Fever) • Epidemiology • Occurs among wild animals in Northern Hemisphere • In eastern U.S. most infections occur in winter • Result from skinning hunted rabbits • In western U.S. infections increase in summer • Due to bites from fleas and ticks • Other reservoirs for infection include • Muskrats, beavers, squirrels, and deer • Prevention and Treatment • Uses PPE when working with animal carcasses • Insect repellents and protective clothing, inspect routinely for ticks • Vaccine available for workers at higher risk of exposure • Treated with gentamicin

11. Brucellosis (Undulant Fever) • Causative agent • Four varieties of Brucella melitensis cause disease in humans • Traditionally each variety given own species name depending on preferred host • B. abortus  cattle • B. canis  dogs • B. melitensis  goats • B. suis  pigs • Organism is Gram (-) rod

12. Brucellosis (Undulant Fever) • Symptoms • Onset usually gradual and symptoms vague • Symptoms flu-like • Without treatment most cases recover within 2 months • 15% will be symptomatic for 3 months or longer

13. Brucellosis (Undulant Fever) • Pathogenesis • Organism penetrates mucous membranes or break in skin • Disseminated via lymphatic or blood vessels • Generally to heart , kidneys, and spleen • Organisms resistant to phagocytic killing • Mortality generally due to endocarditis • Rate is approximately 2% • Osteomyelitis is another serious side effect

14. Brucellosis (Undulant Fever) • Epidemiology • Chronic infection of domestic food animals • Generally involving the mammary gland and uterus • Occurs in workers in meat packing industry • Prevention and Treatment • Pasteurization • Inspection of domestic animals • PPE when working with animals or animal carcass • Attenuated vaccine controls disease in domestic animals • Tetracycline combined with rifampin for 6 weeks

15. Plague (Black Death) • Causative agent • Yersinia pestis • Facultative intracellular bacteria • Resemble safety pin in stained preparation

16. Plague (Black Death) • Symptoms • Develop abruptly 1 – 6 days post infection • Transmission via bite from infected flea • Disease characterized by large tender lymph nodes called buboes • Other symptoms include • High fever • Shock • Delirium • Patchy bleeding under the skin • May also have cough and bloody sputum • Only in lungs infected • Pneumonic plague

17. Plague (Black Death) • Pathogenesis • Flea regurgitates infected material into bite wound • Pla is essential to spread from site of entry • Organisms multiply within macrophages • Macrophages die and release organism • Inflammation in nodes results in characteristic swelling • Nodes become necrotic and spill organisms • Septicemic plague • Mortality rate of untreated reaches between 50% and 80%

18. Plague (Black Death) • Epidemiology • Endemic on rodent populations in all continents except Australia • Prairie dogs, rock squirrels and their fleas are main reservoir • Can spread person to person by household fleas • Organism can remain viable for weeks in dried sputum and flea feces • Prevention and Treatment • Prevention directed by rat control • Killed vaccine gives short-term partial protection • Prompt diagnosis and treatment prevent high mortality • tetracycline for some exposed individuals to control epidemics • Gentamicin, ciprofloxacin and doxycycline effective if given early

19. Infectious Mononucleosis • Causative agent • Caused by Epstein-Barr virus • Double-stranded DNA virus • Belongs to herpesvirus family • Symptoms • Appear after long incubation • Usually 30 to 60 days post infection • Symptoms include fever, sore throat covered with pus, fatigue, enlarged lymph nodes and spleen • Most cases fever and sore throat disappear within 2 weeks, lymph node enlargement within 3

20. Pathogenesis of Epstein-Barr Virus

21. Infectious Mononucleosis • Epidemiology • Distributed worldwide • Infects individuals in crowded, economically disadvantaged areas • Infects at early age without producing symptoms producing immunity • More affluent populations missed exposure and lack immunity • Virus present in saliva for up to 18 months • Mouth-to-mouth kissing important mode of transmission • No animal reservoir • Prevention and Treatment • Avoiding saliva of another person

22. Yellow Fever • Causative agent • Enveloped, single-stranded RNA arbovirus • Belongs to flavivirus family • Virus multiplies in mosquitoes • Mosquitoes transmit virus to humans • Symptoms • Disease can range from mild to severe • Most common form may be only fever and slight headache lasting a day or two • Severe disease characterized by high fever, nausea, nose bleeds and bleeding into the skin, “black vomit” from GI bleeding and jaundice • Mortality rate of severe disease can reach 50% • Reason for the variation in symptoms is unknown

23. Yellow Fever • Pathogenesis • Introduce via bite of Aedes mosquitoes • Multiplies and enters blood stream • Carried to liver • Jaundice results in liver damage • Injury to small blood vessels produces petechiae • Kidney failure is a common consequence of disease • Epidemiology • Reservoir mainly infected mosquitoes and primates in tropical regions of Central and South America and Africa • Periodically spread to urban areas via mosquito bite • Prevention and Treatment • Control achieved by spraying and elimination of breeding sites

24. Malaria • Causative agent • Human malaria caused by four species of genus Plasmodium • P. vivax, P. falciparum, P. malatiae, P. ovale • Infectious form of parasite injected via mosquito • Carried by bloodstream to liver • Infects cells of liver • Thousands of offspring released to produce infection in erythrocytes

25. Malaria • Symptoms • “flu-like” • Generally begin 2 weeks post infection • Transmission via bite of infected mosquito • Symptom pattern changes after 2 to 3 weeks • Falls into three categories • Cold phase – abruptly feels cold and develops shaking • Hot phase – follows cold phase • Temperature rises steeply reaching 104°F • Wet phase – follows hot phase • Temperature falls and drenching sweat occurs

26. Malaria • Pathogenesis • Characteristic feature • Recurrent bouts of fever followed by times of wellness • Caused by erythrocytic cycle of growth and release of offspring • Spleen enlarges to cope with large amount of foreign material and abnormal RBC • Parasites cause anemia by destroying red RBC and converting iron from hemoglobin to non-usable form • Stimulates immune system • Overworked immune system fails and immunodeficiency develops

27. Malaria • Epidemiology • Once common in both temperate and tropical areas • Now dominantly disease of warm climate • Eliminated from continental U.S. in late 1940’s • Mosquitoes of genus Anopheles are biological vectors • Infected mosquitoes and humans constitute reservoir • Transmission via mosquitoes, blood transfusion and sharing of syringes • Prevention and Treatment • Treatment is complicated • Chloroquine • Primaquine and tafenoquine