CNS consists of the brain and the spinal cord &infections can be caused by: Normal bacterial flora Pathogens acquired through ingestion Pathogens

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2 CNS consists of the brain and the spinal cord &infections can be caused by: Normal bacterial flora Pathogens acquired through ingestion Pathogens acquired during the birthing process Contamination of shunts

3 Infection of the meninges ( the system of membranes which envelopes the central nervous system). Usually caused by a bacterial infection Characterized by fever, irritability, and various degrees of neurological dysfunction

4 Usually caused by Mycobacterium tuberculosis, fungi, or protozoan parasites. Characterized by fever, headache, stiff neck and back, nausea, and vomiting

5 Involves seizures, paralysis, or defective mental faculties. Problem is not with the meninges, but the actual nervous tissue.

6 POLIOMYELITIS: Infection which destroys cells associated with the anterior the spinal cord, and brain stem. Causes weakness or paralysis of muscle groups & Can cause respiratory difficulties Characterized by asymmetrical paralysis ACUTE POLIOMYELITIS : Inflammatory infection of the peripheral nervous system (consists of the nerves and ganglia outside of the brain and the spinal cord) Characterized by symmetrical paralysis Can be caused by diphtheria toxin, enteric pathogens, cytomegalovirus, and Epstein-Barr virus

7 Acute meningitis usually caused by: H. influenzae N. meningitidis S. pneumoniae A vaccine is available to protect against H. influenzae. Group B streptococci and E. coli often involved in meningitis in newborns Acquired through the birthing process

8 Most common viral causes of acute CNS infections: Enterovirus Herpes simplex virus HIV Epstein-Barr virus Also several arthropod-borne viruses Deep fungal mycoses Cryptococcus neoformans and Coccidioides immitis

9 Tetanus is caused by Clostridium tetani. Gram-positive Anaerobic Rod shaped Produces a terminal spore Toxin produced by C. tetani is neurogenic

10 CDC

11 Etiologic agent is Clostridium botulinum. Gram-positive Anaerobic Spore-forming Rod-shaped Found naturally in soil and sediments of ponds and lakes.

12 Rabies is an acute and fatal viral CNS infection. Can affect all mammals Transmitted by infected secretions (usually through a bite). Prevention is the best cure. Treatment consists of a course of injections. Only beneficial if administered before the onset of symptoms Mortality for rabies is 90%.

13 Enterovirus - Condition first known as infantile paralysis Risk of paralysis actually increases with age. Essentially nonexistent in most modern countries There is an effective vaccine. Still a major problem in underdeveloped countries

14 BSE (mad cow disease) was first identified in the UK in Source of prions traced to cattle feed containing bone meal from sheep that had scrapie. Cows ate the feed and became infected. The infection passed to humans who ate infected beef. Infection in humans is known as variant Creuztfeld-Jacob disease (vcjd). Cases frequently present in young adults.

15 Cryptococcosis is the most important fungal CNS infection. Caused by Cryptococcus neoformans Encapsulated form of yeast Capsule production varies with the strain and environmental conditions. Found throughout world, especially in soil contaminated with bird droppings Causes a chronic form of meningitis

16 Acanthamoeba & Naegleria: Both cysts and trophozoites of amoeba can be found in lesions. AIDS patients can have: Cutaneous ulcers and hard nodules containing amebas Amebas in the cerebrospinal fluid. Acanthamoeba occasionally ends in spontaneous recovery. It is invariably fatal in the immunocompromised.

17 Courtesy of Dr. Andrew Bollen and Dr. Walter Finkbeiner.

18 Bacterial and fungal infections require prompt and aggressive treatment. Treatment periods vary depending on the type of infection. 10 days to 12 months for uncomplicated cases Longer if the infection is caused by M. tuberculosis Treatment of fungal infections can last for years. Treatment of viral infections is mostly supportive.

19 Infections in the blood easily become systemic and systemic infections can have devastating effects on the patient. Types: Bacteremia Viremia Fungemia Parasitemia Pathogenic organisms growing in the blood can lead to major clinical conditions: Sepsis & Septic shock

20 Infections in the blood easily become systemic and systemic infections can have devastating effects on the patient.

21 Systemic nature of blood infections requires aggressive treatment. Blood has access to the entire body: Can carry pathogens from one location to another. Presence of circulating pathogens is a natural progression of an infection: These are quickly removed from the blood by host defenses. In some cases pathogens in the blood reflect a serious, uncontrollable infection.

22 Depending on type of organism blood infections are classified as: Bacteremia Viremia Fungemia Parasitemia

23 Pathogenic organisms growing in the blood can lead to major clinical conditions: Sepsis Septic shock Bacteremia and fungemia can also be caused by pathogens growing inside or outside of intravenous devices.

24 INTRAVASCULAR INFECTIONS-arise when pathogens enter the blood and damage the structures of cardiovascular system Endocarditis infection of the heart Thrombophlebitis infection in the veins Endoarteritis infection of the arteries Most commonly caused by bacteria Fungi are sometimes involved. Infections of the cardiovascular are very dangerous & Can be fatal Commonly produce shedding of organisms into the blood.

25 INFECTIOUS ENDOCARDITIS-Once referred to as bacterial endocarditis Now known that organisms other than bacteria can cause it Infection affects the heart valves Can also develop on the septa of the heart and cardiac shunts. 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

26 CDC/Dr. Edwin P. Ewing, Jr.

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28 Complications from infectious endocarditis: Risk of congestive heart failure Rupture of the chordae tendineae Perforation of the valves Kidney damage Blood is found in urine.

29 SEPSIS AND SEPTIC SHOCK- both result from the progression of bacteremia Gram-positive and Gram-negative bacteria can be responsible Fungi, protozoa, and viruses can also be the cause Sepsis an infection which causes a host response including: sepsis causing altered blood flow to organs causing reduced urine ; changes in mental status; Development of hypotension Multiorgan failure and death.

30 Vector-transmitted to humans. Most explosively virulent bacterial infection ever known. Spreads from lymph nodes to blood From there can spread to the lungs Referred to as pneumonic plague Bacteria multiply very rapidly in lymph nodes Produces a bubo From bubo, bacteria spread rapidly into the blood.

31 CDC

32 Infection of wild animals that can be transmitted to humans. Infected animals may not show any signs. Caused by Francisella tularensis Grows only on specialized medium Takes up to 10 days of incubation Ingestion of contaminated meat or water

33 Brucella enters the host through cuts in the skin,contact with mucous membranes, inhalation; I ngestion Zoonotic infection which involves infection of the reproductive tract. Transmission to humans is by: Occupational contact Ingesting contaminated animal products Chronic illness in humans Can last for weeks or months Causes fever, night sweats, and weight loss Cyclic pattern of symptoms undulant fever

34 Transmitted to humans by Ixodes tick. Caused by the spirochete Borrelia burgdorferi Gram-negative Requires specialized medium for growth Involves ticks, mice, and deer Humans are incidentally involved Acute Lyme disease characterized by: Fever Migratory bull s-eye rash Muscular and joint pain Often meningeal irritation Deer are host for the final stages

35 CDC/James Gathany

36 Rickettsia are coccobacilli that have characteristics of both bacteria and viruses. Divide by binary fission, Very small Gram-negative but stain very poorly Better resolved with Giemsa stain Have a peptidoglycan cell wall with a Gram-negative outer layer Are obligate intracellular parasites

37 Most common infection is Rocky Mountain Spotted Fever (RMSF) caused by Rickettsia rickettsii. Seen throughout the world Most have animal reservoirs Transmitted by arthropod vectors Spread through the vector s life cycle Occurs in association with exposure to wooded areas infested with ticks. Vectors are ticks. Different vectors in different geographic locations

38 Epidemic typhus is a classic example of a rickettsial infection. Most prevalent in U.S. is RMSF. Both characterized by fever, rash, and muscle aches. Both may be fatal as a result of vascular collapse Rickettsia pathogens do not harm the tick Rash is the most characteristic feature.

39 Several forms of typhus, but the two most important are: Epidemic Typhus- Caused by Rickettsia prowazekii. Transmitted by human louse Pediculus humanus corporis. Historically seen in times of war or famine. Crowding and infrequent bathing are common

40 Endemic typhus is caused by Rickettsia typhi. Primary infection rodent to rodent Human infection incidental Transmitted to humans by the rat flea Headache, muscle aches, and fever Maculopapular rash forms

41 Viruses can be found in the blood viremia. Some viruses use blood cells as their hosts. CYTOMEGALOVIRUS- is a herpes viral genus of the Herpesviruses group ARBOVIRUSES- a group of viruses that are transmitted by arthropod vectors & infections in blood are classified as fever infections. Dengue fever & Yellow fever: arbovirus attacks the liver and vector for both are mosquitoes.

42 EPSTEIN-BARR VIRUS- human herpesvirus, a cancer-causing virus of the herpes family, which includes herpes simplex virus1 and 2, and is one of the most common viruses in humans. Dr. M. A. Ansary / Science Photo Library

43 FILOVIRUSES- Ebola and Marburg Ebola is very contagious. Transmission is person-to-person 10% of population in rural Central Africa carry Ebola antibodies. Marburg virus has also been seen in nosocomial settings. 25% mortality rate

44 Ebola & Marburg both cause hemorrhaging in the skin, mucous membranes, and internal organs. Liver cells, lymphoid tissue, kidneys, gonads are all destroyed & can also cause brain damage Reasons for such rapid hemorrhaging are still not clear. Evidence that Marburg replicates in vascular endothelial cells Causes necrosis and bleeding Ebola causes symptoms in as little as 4-6 days. Mortality rate is extremely high: 60-80%. There is no treatment.

45 There are several important and dangerous parasitic infections of the blood: Malaria Trypanosomiasis Filariasis Toxoplasmosis Schistosomiasis

46 American form of trypanosomiasis. Caused by the flagellate protozoan Trypanosoma cruzi.

47 Caused by thread-like filarial nematodes (roundworms) family known as "filariae Tissue changes seen in elephantiasis are often irreversible. Enlarging of the extremities may be ameliorated through the use of pressure bandages. Control of the vector helps prevent infection.

48 CDC

49 Toxoplasmosis is a parasitic disease caused by the protozoan Toxoplasma gondii The parasite infects most genera of warm-blooded animals, including humans, but the primary host is the felid (cat) family Animals are infected by eating infected meat, by ingestion of feces of a cat that has itself recently been infected, or by transmission from mother to fetus. (Refer website /text bk for images)

50 Schistosomiasis Schistosomiasis also known as bilharzia, bilharziosis or snail fever) is a parasitic disease caused by several species of tremotodes ("flukes") a parasitic worm of the genus Schistosoma Refer internet/textbo ok for images

51 Skin and eyes are in contact with potentially pathogenic organisms all the time. Many infections can occur on the skin. The skin is always exposed to pathogens. Soft tissue below the skin is a breeding ground for infections. Eyes are open to the outside world. Infections here extremely dangerous. Proximity to the nervous system Potential for loss of vision

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54 Necrotizing faciitis, Steve Burdette. In Empiric, Esun Technologies, Pittsburgh, PA

55 Salient sign is blistering and peeling off of large sheets of skin. Caused by two exotoxins secreted by certain strains of S. aureus exfoliatins. Normally restricted to infants Can occur in adults, especially in late stages of toxic shock syndrome

56 Gangrene caused by Clostridium perfringens. Tissue necrosis resulting from an obstructed blood supply. Bacteria responsible for the infection release gases. Usually associated with deep tissue wounds. Movement of the affected area causes snap, crackle, and popping sounds, a foul smell Infection is accompanied by high fever, massive tissue destruction, shock, and blackened skin. If not treated, gas gangrene is lethal.

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58 Topical eye drops and ointments containing erythromycin or gentamicin are effective against acute bacterial conjunctivitis. Fluoroquinolones can be used for eye infections caused by Pseudomonas. Quinolones such as ciprofloxacin useful for all types of eye infection.

59 Microbiology, A clinical Approach - Danielle Moszyk-Strelkauskas-Garland Science hod

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