Opportunistic Infections (Buxton) Flashcards Preview

CMBM Exam 4 CL > Opportunistic Infections (Buxton) > Flashcards

Flashcards in Opportunistic Infections (Buxton) Deck (78):
1

What are 3 things that can compromise a host?

Defects/injury to physical barriers

Deficiencies in innate immunity

Deficiencies in adaptive immunity

2

A 12 year old child is severely burned in a house fire. He was hospitalized for over a month with 3rd degree burns on his leg.  About a week after admission, he developed an infection of the burned areas. Blue-green pus was associated with the infection.

What factors increased this child's risk of infection?
 

Burn - loss of protective skin barrier; severe burns lead to decrease in neutrophil function

Hospitalization - at risk for nocosomial infections

3

A 12 year old child is severely burned in a house fire. He was hospitalized for over a month with 3rd degree burns on his leg.  About a week after admission, he developed an infection of the burned areas. Blue-green pus was associated with the infection.
 

Which organisms are the most common causes of burn infections?

Pseudomonas aeruginosa (wet areas)

Staphylococcus aureus (skin)

Staphylococcus epidermidis (skin)

Streptococcus pyogenes (skin, mucous membranes)

Candida (skin, mucous membranes)

Aspergillus (soil, dark & damp areas - spores)

*burn infections often polymicrobial*

4

Q image thumb

Pseudomonas on nutrient agar

5

Q image thumb

Aspergillus

6

Name the following microbes isolated from the 12 y/o burn patient's blood and/or exudate.

1. Gram (+) cocci, catalase (+), coagulase (-)

2. Gram (+) cocci, catalase (+), coagulase (+)

3. Gram (-) rod, greenish colored colonies on nutrient agar

4. fungus in below image

Q image thumb

1. Staph epidermidis

2. Staph aureus

3. Pseudomonas 

4. Aspergillus

7

Of the 4 microbes isolated from the 12 y/o burn patient's wounds, what was isolated from his burn? What was isolated from his blood?

Burn - Pseudomonas, Staph epidermidis

Blood - Pseudomonas, Staph aureus, Aspergillus

8

How did the 12 y/o burn patient become infected?

Skin colonization - Staph

Hospital environment - Pseudomonas, Aspergillus

9

Describe the pathogenesis of burn wound infections.

Bacteria that colonize skin are first to invade wound (within days). Pseudomonal & fungal infections occur ~1 week after hospitalization. Important virulence factors include resistance to phagocytosis & enzymes that facilitate invasion.

10

Describe the epidemiology of Pseudomonas.

Ubiquitous

Resistant to some common disinfectants

Antibiotic resistance is common

Causes infections in CF, catheterized, burn, and intubated patients

11

What are common locations for Pseudomonas infections?

Skin & musculocutaneous tissues

Respiratory tract

CNS

Localized 

Blood (bacteremia)

Heart (endocarditis)

Urinary tract (UTI)

12

Q image thumb

Ecthyma gangrenosum - consequence of Pseudomonas septisemia; hemorrhagic necrosis of the skin

13

How would you treat your 12 y/o burn patient who is positive for Staph epidermidis, Staph aureus, and Aspergillus?

MRSA - Vancomycin, Linezolid, Streptogramin

MSSA - Vafcillin/Oxacillin/Dicloxacillin, 1st/2nd gen. cephalosporin, Clindamycin

Pseudomonas - Extend spectrum penicillin + beta-lactamase inhibitor, carbapemen, Monobactam, fluoroquinolones, Ceftazidime, Cefepime, aminoglycosides

Aspergillus - Voriconazole, Caspfungin

So...Vancomycin + Amp B until data comes back

14

A newborn baby had a fever and appeared septic. Blood cultures grew a gram-positive coccobacillus that was weakly beta-hemolytic, was motile and grew at 4C.  A diagnosis of Listeria monocytogenes was made, and the infection was transmitted from the mother prior to birth.


Why is an infant considered immune compromised?
 

Decreased: production of neutrophils, killing by phagocytes, complement levels, NK cell activity, in vitro lymphocyte proliferation, cytokine production by lymphocytes, CTL responses, expression of CD40L, production of Ig (especially IgG & IgA).

15

A newborn baby had a fever and appeared septic. Blood cultures grew a gram-positive coccobacillus that was weakly beta-hemolytic, was motile and grew at 4C.  A diagnosis of Listeria monocytogenes was made, and the infection was transmitted from the mother prior to birth.

How did the infant become infected?

Fetal infection can occur from:

transplacental transmission

ascending infection through ruptured amniotic membranes

during birth through an infected birth canal

16

A newborn baby had a fever and appeared septic. Blood cultures grew a gram-positive coccobacillus that was weakly beta-hemolytic, was motile and grew at 4C.  A diagnosis of Listeria monocytogenes was made, and the infection was transmitted from the mother prior to birth.
 

What were the symptoms, if any, in the mother?

Nausea, vomiting, diarrhea, fever, malaise, back pain, and headache

Many pregnant women can carry Listeria asymptomatically in their GI tract or vagina

Maternal infection with Listeria can affect pregnancy by causing chorioamnionitis, premature labor, spontaneous abortion, or stillbirth

17

A newborn baby had a fever and appeared septic. Blood cultures grew a gram-positive coccobacillus that was weakly beta-hemolytic, was motile and grew at 4C.  A diagnosis of Listeria monocytogenes was made, and the infection was transmitted from the mother prior to birth.
 

Where is the organism found in nature - how did the mother become infected?

Widely distributed in nature - intestinal tracts of many mammals; most commonly associated with ingestion of prepared meat, dairy products, unwashed raw vegetables, and seafood. Soft cheeses and unpasteurized milk have bee nthe most frequently incriminated dairy products. 

18

A newborn baby had a fever and appeared septic. Blood cultures grew a gram-positive coccobacillus that was weakly beta-hemolytic, was motile and grew at 4C.  A diagnosis of Listeria monocytogenes was made, and the infection was transmitted from the mother prior to birth.
 

How would you treat the baby?

Ampicillin + Gentamicin

19

A 42 year old woman is hospitalized with pneumonia. Her history is significant for long term corticosteriod use for severe asthma. A sputum gram stain revealed gram-positive bacilli, coccobacillary cells and branching filaments. A modified acid-fast stain showed the organism to be partially acid-fast. The organism was identified as Nocardia sp.
 

What made this patient susceptible to this infection?

Corticosteroids - long-term use

20

A 42 year old woman is hospitalized with pneumonia. Her history is significant for long term corticosteriod use for severe asthma. A sputum gram stain revealed gram-positive bacilli, coccobacillary cells and branching filaments. A modified acid-fast stain showed the organism to be partially acid-fast. The organism was identified as Nocardia sp.

What is the source of the bacteria?

Ubiquitous in soil and water

21

A 42 year old woman is hospitalized with pneumonia. Her history is significant for long term corticosteriod use for severe asthma. A sputum gram stain revealed gram-positive bacilli, coccobacillary cells and branching filaments. A modified acid-fast stain showed the organism to be partially acid-fast. The organism was identified as Nocardia sp.

What are the unusual features of this bacteria?

Cell walls contain mycolic acid, thus pick up acid fast stain

22

A 42 year old woman is hospitalized with pneumonia. Her history is significant for long term corticosteriod use for severe asthma. A sputum gram stain revealed gram-positive bacilli, coccobacillary cells and branching filaments. A modified acid-fast stain showed the organism to be partially acid-fast. The organism was identified as Nocardia sp.

How should she be treated?

TMP/SMX is drug of choice; other antibiotic combinations can be used

23

Q image thumb

Nocardia

24

A 42 year old woman is hospitalized with pneumonia. Her history is significant for long term corticosteriod use for severe asthma. A sputum gram stain revealed gram-positive bacilli, coccobacillary cells and branching filaments. A modified acid-fast stain showed the organism to be partially acid-fast. The organism was identified as Nocardia sp. 

If patient has pulmonary nocardosis, what symptoms would you expect to find?

Lobar pneumonia with abscess formation

May mimic TB clinically - fever, weight loss, chest pain

Infection can spread from lung to other sites via blood

 

25

A 23 year old AIDS patient had fever, night sweats, fatigue and diarrhea for the past 3 months. Over that time, she has lost 22 pounds and is short of breath. Her CD4 count has been below 50/cmm for the past 6 months and her viral load is 55,000/cmm. Routine blood cultures were negative after 48 hours; however, growth was seen after 10 days. DNA probes identified the organism as belonging to the Mycobacterium avium complex.

What are the diagnostic features of this organism?
 

Group of related organisms - MAC

Bacilli-weakly gram (+), strongly acid fast

26

Q image thumb

MAC infection in aids patient - disseminated acid fast rods in tissue

27

A 23 year old AIDS patient had fever, night sweats, fatigue and diarrhea for the past 3 months. Over that time, she has lost 22 pounds and is short of breath. Her CD4 count has been below 50/cmm for the past 6 months and her viral load is 55,000/cmm. Routine blood cultures were negative after 48 hours; however, growth was seen after 10 days. DNA probes identified the organism as belonging to the Mycobacterium avium complex. 

What are the sources of this organism?
 

Infect many bird & mammal species

Ubiquitous - in water & soil

Infection thought to occur by ingestion or inhalation

28

Describe the pathogenesis of disseminated MAC infection.

Enters immunocompromised person via ingestion/inhalation - infects resting macrophages of mucosal epithelium - carries organism throughout body (lymphatic sites) - replicates to very high numbers within macrophages within various tissues - infected macrophages secrete cytokines - cytokine storm

29

A 23 year old AIDS patient had fever, night sweats, fatigue and diarrhea for the past 3 months. Over that time, she has lost 22 pounds and is short of breath. Her CD4 count has been below 50/cmm for the past 6 months and her viral load is 55,000/cmm. Routine blood cultures were negative after 48 hours; however, growth was seen after 10 days. DNA probes identified the organism as belonging to the Mycobacterium avium complex.

What diseases does it cause in immune-competent individuals?
 

Pulmonary disease in persons with underlying lung conditions, smokers

30

A 23 year old AIDS patient had fever, night sweats, fatigue and diarrhea for the past 3 months. Over that time, she has lost 22 pounds and is short of breath. Her CD4 count has been below 50/cmm for the past 6 months and her viral load is 55,000/cmm. Routine blood cultures were negative after 48 hours; however, growth was seen after 10 days. DNA probes identified the organism as belonging to the Mycobacterium avium complex.

How is it treated?

In AIDS patients: Clarithromycin/Azithromycin + Ethambutol

31

A 23 year old AIDS patient had fever, night sweats, fatigue and diarrhea for the past 3 months. Over that time, she has lost 22 pounds and is short of breath. Her CD4 count has been below 50/cmm for the past 6 months and her viral load is 55,000/cmm. Routine blood cultures were negative after 48 hours; however, growth was seen after 10 days. DNA probes identified the organism as belonging to the Mycobacterium avium complex.

Could the infection have been prevented in this patient?

AIDS: yes - prophylaxis with Clarithromycin or Azithromycin when CD4 count falls < 50/cmm

32

A 42-year old male with AIDS develops neurologic signs. 

What are some infectious causes of neurologic signs in AIDS patients?


 

AIDS dementia complex (ADC)

Cryptococcal meningitis

Toxoplasma gondii encephalitis

Progressive multifocal leukoencephalopathy (JCV)

33

A 42-year old male with AIDS develops neurologic signs. The patient  was brought to his physician’s office by a friend who reports progressive confusion developing over the past 6 weeks. The patient has become increasingly forgetful. Over the past week, he has developed progressive weakness on the right side of his body (Hemiparesis). CSF exam was normal. PCR of CSF found DNA of JC virus.

What does this patient have in addition to JCV? What symptom(s) clues you in to this diagnosis? What other symptoms might the patient exhibit?

PML - progressive multifocal leukoencephalopathy - hemiparesis

Insidious onset of focal symptoms including behavioral, speech, cognitive, moor, and visual impairment due to focal areas of demyelination throughout the brain.

34

What virus causes a common latent infection, has a seroprevalence rate among adults > 90%, is not associated with disease in healthy people, and causes PML in profoundly T cell suppressed individuals?

JC Virus

35

A 23-year old AIDS patient developed a fever, severe headache, stiff neck, nausea and vomiting. A CSF exam revealed slightly elevated protein, slightly decreased glucose and 10 WBC per ul. Yeast were seen in an India ink stain. What is the most likely diagnosis?
 

Cryptococcus neoformans

36

Q image thumb

Yeast on India ink stain

37

A 23-year old AIDS patient developed a fever, severe headache, stiff neck, nausea and vomiting. A CSF exam revealed slightly elevated protein, slightly decreased glucose and 10 WBC per ul. Yeast were seen in an India ink stain.

Where is this organism found in nature?

Associated with dried pigeon droppings

38

A 23-year old AIDS patient developed a fever, severe headache, stiff neck, nausea and vomiting. A CSF exam revealed slightly elevated protein, slightly decreased glucose and 10 WBC per ul. Yeast were seen in an India ink stain.

How did he become infected?

Enters through inhalation, evades phagocytosis and Th1 cell responses, enters blood, disseminates to meninges and other tissues

39

A 23-year old AIDS patient developed a fever, severe headache, stiff neck, nausea and vomiting. A CSF exam revealed slightly elevated protein, slightly decreased glucose and 10 WBC per ul. Yeast were seen in an India ink stain.

What are important virulence factors of this organism?

Produces a thick polysaccharide capsule once inhaled

40

A 23-year old AIDS patient developed a fever, severe headache, stiff neck, nausea and vomiting. A CSF exam revealed slightly elevated protein, slightly decreased glucose and 10 WBC per ul. Yeast were seen in an India ink stain.

How is this infection diagnosed?

Detection of capsular polysaccharide antigen in serum or CSF, confirmed with growth on Sabouraud's agar or Heart Brain infusion agar.

41

A 23-year old AIDS patient developed a fever, severe headache, stiff neck, nausea and vomiting. A CSF exam revealed slightly elevated protein, slightly decreased glucose and 10 WBC per ul. Yeast were seen in an India ink stain.

What is the treatment?

Amphotericin B + Flucytosine

Maintenance with Fluconazole until CD4 cells increase > 100 for > 6 months

42

An AIDS patient from southeast Missouri presents with persistent high grade fever, weight loss. Physical exam revealed hepatosplenomegaly, mucocutaneous ulcers in the mouth and skin lesions. An ELISA done on serum and urine for Histoplasma antigen was positive. Culture of the skin lesions on Sabouraud’s agar grew Histoplasma capsulatum  after 4 weeks.

What was the source of this infection?
 

Endemic mycosis

Found in Ohio, Missouri, and Mississippi River Valleys

Found in soil contaminated with bird and bat droppings

43

An AIDS patient from southeast Missouri presents with persistent high grade fever, weight loss. Physical exam revealed hepatosplenomegaly, mucocutaneous ulcers in the mouth and skin lesions. An ELISA done on serum and urine for Histoplasma antigen was positive. Culture of the skin lesions on Sabouraud’s agar grew Histoplasma capsulatum  after 4 weeks.

Describe the pathogenesis of disseminated histoplasmosis.

Most likely the result of a prior infection

Fungi once contained in lung granulomas were able to replicate and disseminate following immune suppression

Spreads throughout body

Can be isolated from many tissues

Fatal if not treated

44

An AIDS patient from southeast Missouri presents with persistent high grade fever, weight loss. Physical exam revealed hepatosplenomegaly, mucocutaneous ulcers in the mouth and skin lesions. An ELISA done on serum and urine for Histoplasma antigen was positive. Culture of the skin lesions on Sabouraud’s agar grew Histoplasma capsulatum  after 4 weeks.

Who is at risk for disseminated histoplasmosis?

Patients with profound T cell immune suppression

45

An AIDS patient from southeast Missouri presents with persistent high grade fever, weight loss. Physical exam revealed hepatosplenomegaly, mucocutaneous ulcers in the mouth and skin lesions. An ELISA done on serum and urine for Histoplasma antigen was positive. Culture of the skin lesions on Sabouraud’s agar grew Histoplasma capsulatum  after 4 weeks.

What other clinical manifestations are caused by H. capsulatum?

Initial infection in healthy person - flu-like illness

Chronic pulmonary histoplasmosis (patients with underlying pulmonary disease) - organism does not get walled off effectively, which can lead to cavitations and hemoptosis

46

An AIDS patient from southeast Missouri presents with persistent high grade fever, weight loss. Physical exam revealed hepatosplenomegaly, mucocutaneous ulcers in the mouth and skin lesions. An ELISA done on serum and urine for Histoplasma antigen was positive. Culture of the skin lesions on Sabouraud’s agar grew Histoplasma capsulatum  after 4 weeks.

How should patient be treated?

If overwhelming, disseminated - Amphotericin B with maintainance with Itraconazole until/if sustained improvement in CD4 numbers and viral load

47

Q image thumb

Musculocutaneous ulcers in the mouth; skin lesion due to Histoplasma

48

A 36 year old AIDS patient developed fever and shortness of breath. Since his last medical exam, his CD4 count has dropped to 120/cmm and his viral load has risen to 165,000/cmm. A bronchoalveolar levage specimen stained with methenamine silver revealed trophozoites and cysts.

With what is he infected?
 

Pneumocystis jiroveci

49

A bronchoalveolar levage specimen stained with methenamine silver revealed trophozoites and cysts.

Q image thumb

Pneumocystis jiroveci

50

A 36 year old AIDS patient developed fever and shortness of breath. Since his last medical exam, his CD4 count has dropped to 120/cmm and his viral load has risen to 165,000/cmm. A bronchoalveolar levage specimen stained with methenamine silver revealed trophozoites and cysts.

What kind of organism is this?

Fungus

51

A 36 year old AIDS patient developed fever and shortness of breath. Since his last medical exam, his CD4 count has dropped to 120/cmm and his viral load has risen to 165,000/cmm. A bronchoalveolar levage specimen stained with methenamine silver revealed trophozoites and cysts.

What is the source of the organism?

Source has not been definitively identified. 

May be acquired by inhalation of airborne cysts

Most individuals acquire the organism early in childhood

52

A 36 year old AIDS patient developed fever and shortness of breath. Since his last medical exam, his CD4 count has dropped to 120/cmm and his viral load has risen to 165,000/cmm. A bronchoalveolar levage specimen stained with methenamine silver revealed trophozoites and cysts.

Describe the pathogenesis of this organism.

Pneumocystis jiroveci

Extracellular pathogen controlled by pphagocytic macrophages - enters lung of T cell immune-suppressed individuals - replicates in surfactant - damages basement membrane during proliferation, altering permeability & reducing O2 exchange

53

A 36 year old AIDS patient developed fever and shortness of breath. Since his last medical exam, his CD4 count has dropped to 120/cmm and his viral load has risen to 165,000/cmm. A bronchoalveolar levage specimen stained with methenamine silver revealed trophozoites and cysts.

How can he be treated?

Pneumocystis jiroveci

TMP/SMX  for treatment and maintenance

54

A 36 year old AIDS patient developed fever and shortness of breath. Since his last medical exam, his CD4 count has dropped to 120/cmm and his viral load has risen to 165,000/cmm. A bronchoalveolar levage specimen stained with methenamine silver revealed trophozoites and cysts.

Could this infection have been prevented?

Pneumocystis jiroveci

Yes - prophylactice treatment with TMP/SMX with CD4 count falls below 200/ul.

55

A 10 year old boy developed leukemia for which he was given induction cancer chemotherapy. About a week after chemotherapy began, he developed diarrhea and painful mouth ulcers. Induction chemotherapy lead to remission and the child was placed on maintenance chemotherapy. During this time, his neutrophil count dropped below 500/ul for several weeks and he developed a fever with no localizing signs.

What is a localizing sign and why are they lacking in his case?
 

They're due to inflammatory responses. he has very low neutrophils, thus has poor acute inflammatory responses.

56

A 10 year old boy developed leukemia for which he was given induction cancer chemotherapy. About a week after chemotherapy began, he developed diarrhea and painful mouth ulcers. Induction chemotherapy lead to remission and the child was placed on maintenance chemotherapy. During this time, his neutrophil count dropped below 500/ul for several weeks and he developed a fever with no localizing signs.

What are the causes of fever in a neutropenic cancer patient?

Cancer

Cancer chemotherapy

57

A 10 year old boy developed leukemia for which he was given induction cancer chemotherapy. About a week after chemotherapy began, he developed diarrhea and painful mouth ulcers. Induction chemotherapy lead to remission and the child was placed on maintenance chemotherapy. During this time, his neutrophil count dropped below 500/ul for several weeks and he developed a fever with no localizing signs.

What are possible causes for infection?

Neutropenia < 7 days - Staph, Strep, Pseudomonas, E. coli, Klebsiella

Neutropenia > 10 days - bacterial & fungal - Aspergillus, Candida

58

A 10 year old boy developed leukemia for which he was given induction cancer chemotherapy. About a week after chemotherapy began, he developed diarrhea and painful mouth ulcers. Induction chemotherapy lead to remission and the child was placed on maintenance chemotherapy. During this time, his neutrophil count dropped below 500/ul for several weeks and he developed a fever with no localizing signs. The boy was hospitalized. Blood and urine cultures were taken and the patient was started empirically on broad spectrum IV antibiotics.

What would you recommend?
 

Broad spectrum antibiotic - Ceftazidime or Cefepime; Carbapenem if extended-spectrum beta-lactamase-producing organisms are a problem in the area

Anti-fungal - Caspofungin

59

A 10 year old boy developed leukemia for which he was given induction cancer chemotherapy. About a week after chemotherapy began, he developed diarrhea and painful mouth ulcers. Induction chemotherapy lead to remission and the child was placed on maintenance chemotherapy. During this time, his neutrophil count dropped below 500/ul for several weeks and he developed a fever with no localizing signs. The boy was hospitalized. Blood and urine cultures were taken and the patient was started empirically on broad spectrum IV antibiotics. Candida albicans was isolated on Sabourauds agar from the boy’s blood.


What kind of organism is this, and how did he become infected?
 

Opportunistic yeast

Found as commensals on skin & mucous membranes

Causes infection due to: T cell immune suppression, antibiotic therapy, anticancer therapy, neutropenia

60

What are some disease associations of Candida?

Thrush

Vaginal yeast infections

Esophagitis

Candidemia

Hepatosplenic candidiasis

61

What are treatment options for candidemia?

Echinocandins (caspofungin)

Fluconazole

Voriconazole

Amphotericin B

62

A 52 year old AIDS patient with a CD4 count of 15 developed neurological symptoms.  What are the causes of neurological symptoms in AIDS patients?
 

CNS lymphoma

AIDS dementia complex

Cryptococcal meningitis

Toxoplasma gondii encephalitis

Progressive multifocal leukoencephalitis

CMV encephalitis

63

A 52 year old AIDS patient with a CD4 count of 15 developed neurological symptoms.  What are the causes of neurological symptoms in AIDS patients? An MRI revealed scattered ring-enhancing lesions. 

What are these lesions associated with?

Lymphoma

Toxoplasmosis

Cryptococcosis

64

A 52 year old AIDS patient with a CD4 count of 15 developed neurological symptoms.  What are the causes of neurological symptoms in AIDS patients? An MRI revealed scattered ring-enhancing lesions. After  3 days of hospitalization, the patient died. An autopsy revealed the following: Grossly, the brain was edematous and showed areas of hemorrhagic necrosis. Microscopic examination of brain tissue revealed areas of necrosis and tissue cysts.

Can this infection be treated?
 

Treatment - 3 drug combination

Pyrimethamine

Sulfadiazine

Leukovorin

If intolerant of sulfa drugs, prescribe Clindamycin alongside Pyrimethamine

65

A 52 year old AIDS patient with a CD4 count of 15 developed neurological symptoms.  What are the causes of neurological symptoms in AIDS patients? An MRI revealed scattered ring-enhancing lesions. After  3 days of hospitalization, the patient died. An autopsy revealed the following: Grossly, the brain was edematous and showed areas of hemorrhagic necrosis. Microscopic examination of brain tissue revealed areas of necrosis and tissue cysts.

Can this be prevented?

Prevention in AIDS patients:

TMP/SMX when CD4 count falls below 200

66

A 52 year old AIDS patient with a CD4 count of 15 developed neurological symptoms.  What are the causes of neurological symptoms in AIDS patients? An MRI revealed scattered ring-enhancing lesions. After  3 days of hospitalization, the patient died. An autopsy revealed the following: Grossly, the brain was edematous and showed areas of hemorrhagic necrosis. Microscopic examination of brain tissue revealed areas of necrosis and tissue cysts.

Who else is at risk for toxoplasmosis?

Healthy children & adults - mono-like syndrome

Infants born to infected-during-pregnancy mothers - MAJOR neurological development issues

Patients with severe T cell immune suppression other than AIDS

67

An ultrasound preformed on a pregnant woman in her 16th week of gestation showed her fetus to have hydrocephalis and intracranial calcifications. The mother was tested and found to have IgM antibodies to Toxoplasma gondii. 

What kind of organism is Toxoplasma gondii?

Protozoan

68

An ultrasound preformed on a pregnant woman in her 16th week of gestation showed her fetus to have hydrocephalis and intracranial calcifications. The mother was tested and found to have IgM antibodies to Toxoplasma gondii. 

How may the mother have become infected?

Cleaning the litter box

69

An ultrasound preformed on a pregnant woman in her 16th week of gestation showed her fetus to have hydrocephalis and intracranial calcifications. The mother was tested and found to have IgM antibodies to Toxoplasma gondii. 

What are the manifestations at birth and the long term sequelae of congenital toxoplasmosis?

At birth, most commonly see: 

Hydrocephalis, Intracranial calcifications, Chorioretinitis

Long term, see:

Deafness, visual impairment, learning disabilities

70

An 83 year old woman was hospitalized with profuse, non-bloody, watery diarrhea with nausea, vomiting and lower abdominal cramping. Oocysts stained with a acid-fast stain were detected in a stool sample. Cryptosporidium antigens were detected in stool by ELISA.

What is this organism?
 

Sporozoite protozoan

71

An 83 year old woman was hospitalized with profuse, non-bloody, watery diarrhea with nausea, vomiting and lower abdominal cramping. Oocysts stained with a acid-fast stain were detected in a stool sample. Cryptosporidium antigens were detected in stool by ELISA.

How was she potentially infected?

Ingestion of contaminated water or food

Outbreaks have happened due to contaminated water in pools and water parks (not susceptible to chlorination)

72

An 83 year old woman was hospitalized with profuse, non-bloody, watery diarrhea with nausea, vomiting and lower abdominal cramping. Oocysts stained with a acid-fast stain were detected in a stool sample. Cryptosporidium antigens were detected in stool by ELISA.

Who is at risk for serious disease?

Immune suppressed

Infants

Elderly

73

An 83 year old woman was hospitalized with profuse, non-bloody, watery diarrhea with nausea, vomiting and lower abdominal cramping. Oocysts stained with a acid-fast stain were detected in a stool sample. Cryptosporidium antigens were detected in stool by ELISA.

How would you perform a diagnosis?

Finding oocytes in stool

Requires use of acid fast stain

ELISA tests for antigen detection; PCR test also available

74

An 83 year old woman was hospitalized with profuse, non-bloody, watery diarrhea with nausea, vomiting and lower abdominal cramping. Oocysts stained with a acid-fast stain were detected in a stool sample. Cryptosporidium antigens were detected in stool by ELISA.

What treatment would you use?

Nitazoxanide - immunocompetent

Adjustments to anti-HIV drugs - AIDS patients

Paromomycin - used with some success in immunocompromised, although generally there is no treatment

75

A 54 year old man from rural Georgia was being treated for leukemia with a regimen that included corticosteroids when he developed acute, severe abdominal pain. This was accompanied by nausea, vomiting and diarrhea that was occasionally bloody. Test for bacterial and viral causes of gastroenteritis were negative, however, larvae of Strongyloides stercoralis were found on microscopic examination of the stool. 

Who is at risk of catching this?

Persons living in or visiting endemic areas, including SE US & Appalachian region, tropical & subtropical areas

76

A 54 year old man from rural Georgia was being treated for leukemia with a regimen that included corticosteroids when he developed acute, severe abdominal pain. This was accompanied by nausea, vomiting and diarrhea that was occasionally bloody. Test for bacterial and viral causes of gastroenteritis were negative, however, larvae of Strongyloides stercoralis were found on microscopic examination of the stool. 

What can chronic infections lead to?
 

Disseminated infections if patient becomes immuno-suppressed

77

A 54 year old man from rural Georgia was being treated for leukemia with a regimen that included corticosteroids when he developed acute, severe abdominal pain. This was accompanied by nausea, vomiting and diarrhea that was occasionally bloody. Test for bacterial and viral causes of gastroenteritis were negative, however, larvae of Strongyloides stercoralis were found on microscopic examination of the stool. 

Describe the pathogenesis of this organism.

Parasites escape from GIT in circulation (often bringing along bacteria) - larvae invade CNS, heart, urinary tract, endocrine glands

78

A 54 year old man from rural Georgia was being treated for leukemia with a regimen that included corticosteroids when he developed acute, severe abdominal pain. This was accompanied by nausea, vomiting and diarrhea that was occasionally bloody. Test for bacterial and viral causes of gastroenteritis were negative, however, larvae of Strongyloides stercoralis were found on microscopic examination of the stool. 

How would you treat this?

Thiabendazole