Microbiology- a clinical approach by Anthony Strelkauskas et al Chapter 25: Infections of the blood

 Blood has access to the entire body.  Infections in the blood easily become systemic and systemic infections can have devastating effects on the patient.  Up to this day sepsis has high mortality rate.  Blood infections require aggressive treatment.

ANATOMY OF THE CARDIOVASCULAR SYSTEM

 Depending on type of organism blood infections are classified as: ◦ Bacteremia ◦ Viremia ◦ Fungemia ◦ Parasitemia  Can lead to sepsis and septic shock ◦ The latter in particular with gram negative bacteria

 Intravascular infections when pathogens enter blood and damage the structures of cardiovascular system ◦ Endocarditis – infection of heart ◦ Thrombophlebitis – infection in veins ◦ Endoarteritis – infection of arteries ◦ Catheter associated infections  Extravascular infections ◦ Original infection is in a tissue outside of the circulation ◦ Pathogens get access to the lymphatics and eventually the blood and disseminate into other tissues

 Infection of heart valves  Once referred to as bacterial endocarditis ◦ Now known organisms other than bacteria can cause it  Infection involves several factors: ◦ Alteration of the endothelium ◦ Inflammatory response caused by circulating pathogens ◦ Transient bacteremia ◦ Immune complexes

cardiac attack lung emboli rheumatic fever

 Infectious endocarditis classified in two ways: ◦ Acute – high fever and toxicity  Can result in death within few days or weeks ◦ Subacute – low fever, weight loss, and night sweats  Death can take weeks to months

 Antibiotic therapy must be aggressive ◦ Include bacteriocidal drugs given in high concentration but aren’t toxic ◦ Balancing act that can be difficult  Course of therapy can be prolonged ◦ More than four weeks  Dental procedures are dangerous for people predisposed to infectious endocarditis ◦ Need to take high doses of antibiotics before dental procedures and for 6-12 hours after

 Large numbers antibiotic-resistant bacteria in hospitals  Implantation of intravenous lines potentially serious  Infection from intravenous line or catheter, blood colonized by organisms normally found on skin. ◦ In a healthy host, quickly dealt with by host defense. ◦ In debilitated hosts, bacteremia can persist. ◦ Increase chances of infectious endocarditis, distal infections ◦ Commonly S. epidermis, S.aureus, Cornyebacterium species  Intravenous fluid can also become contaminated ◦ Commonly Gram-negative rods such as Pseudomonas  Removal and treatment with antibiotics will normally remedy catheter bacteremia.

 Most common sources of bacteremia: ◦ Urinary tract infections ◦ Respiratory infections ◦ Skin infections  Gram negative bacteria cause much more severe disease due to endotoxin (LPS; lipopolysaccharide) of cell wall

 Septicemia ◦ Presence of bacteria in blood with severe symptoms  Sepsis ◦ Bacteria present (and proliferating) in blood and dissemination into various with organ dysfunction ◦ Induces a systemic inflammatory response syndrome ◦ Fever, chills, and tachycardia ◦ Reduced urine, systemic acidosis, and changes in mental status  Severe sepsis ◦ Sepsis + decreased blood pressure  Septic shock ◦ Sepsis + low blood pressure cannot be controlled

 Early diagnosis is critical ◦ Resolution depends on more than treatment with antibiotics  Also requires: ◦ Adequate maintenance of tissue perfusion ◦ Careful fluid electrolyte management

 Plague: ◦ Reservoir are rats, transmitted by fleas and from human to human; hemorrhagic necrosis, septic shock  Brucellosis: ◦ Zoonosis from farm animals, undulant fever and granuloma  Lyme disease ◦ Reservoir are mice, transmitted by ticks ◦ Chronic disease: skin, joint and CNS are affected  Rickettsia disease: ◦ Reservoir are rodents, transmitted by fleas or lice ◦ Obligate intracellular ◦ Infect the endothelial cells leading to hemorrhages

 Yellow fever ◦ Liver cells are primary target  Dengue fever ◦ 4 serotypes ◦ Infection with a second serotype can lead to severe manifestation  Ebola virus ◦ Kill vascular cells, patient bleeds to death ◦ High mortality rate, ◦ 60 – 80% within few days

 There are several important and dangerous parasitic infections of the blood: ◦ Plasmodium - malaria  Protozoa  Asia, Africa ◦ Trypanosoma - Chaga’s disease  Latin America  Protozoa ◦ Filaria –elephantiasis  Africa, Latin America, Pacific Islands, Asia  roundworm

 Because blood and lymph travel to all parts of the body, they are good ways to spread infection.  The presence of bacteria in the blood is referred to as bacteremia, viruses in the blood as viremia, fungi in the blood as fungemia, and parasites in the blood as parasitemia.  Intravascular infections arise from pathogens gaining entrance to the blood; extravascular infections occur when tissue infections overflow into the blood.

 Bacterial infections of the blood include plague, brucellosis, and Lyme disease, and rickettsial infections like Rocky Mountain spotted fever, and epidemic or endemic typhus.  Viruses that cause infection of the blood include dengue fever virus, yellow fever virus, and Ebola virus.  The three most important parasitic infections of the blood are malaria, toxoplasmosis, and schistosomiasis, but Chagas’ disease and filariasis are also common parasitic infections of the blood. Chapter 25 key concepts

Final Examination – Wednesday, June 12, 2013  10:45am – 1:15pm  Lecture, Chapter End Self Study Questions  100 Multiple Choice Questions: 2 points each x 100 = 200 points  ~65%: Chapters  ~35%: Chapters 1-13  Please bring Scantron and No. 2 pencil

CORRECTION – Chapter Question  Chapter 22 Infections of the Digestive System  1. The most common source of gastrointestinal infection in the developed world is ◦ A. Salmonella ◦ B. Shigella ◦ C. Escherichia ◦ D. Campylobacter ◦ E. Staphylococcus aureus  Correct answer is D. Campylobacter