Chapter 4: Infectious Disease

What skin surfaces are infected by scabies?

- Wrists - Waistline - Genitals - Webs of fingers

Characteristics of Fungi

-Consist of multicellular filaments (molds) & budding forms (yeasts) -Opportunistic mycoses can cause fatal systemic disease in the immunosuppressed -Superficial mycoses are common and confined to skin, hair, & nails

All of the following are true of endotoxins:

-Found in Gram (-) bacteria -Produce generalized effects, fever, & malaise -Affect the circulatory system, causing vascular collapse

Mucor infection in the nasal passages of a diabetic patient is a surgical emergency. What is the main host factor that predisposes to many fungal infections including Mucor?

-Immunocompromised - On steroid therapy - Severe burns - Diabetes - Autoimmune disease - Impaired WBC function

Put the following in order as they relate to the course of an infection and defined them: recovery, acute phase, incubation, convalescence, and prodromal period

1) Incubation: organism attempts to proliferate 2) Prodromal period: patient suffers mild, nonspecific symptoms, including headache, loss of appetite, and fatigue. 3) Acute phase: time of maximum S/S 4) Convalescence: S/S fade 5) Recovery: no symptoms are present, but the patient still feels fatigued

Clostridium botulinum

Anaerobe; Gram (+)

Why must the influenza vaccine be given yearly?

Antigenic drift

Streptpcoccus pneumoniae

Bacterial coccus Gram (-)

Why are influenza vaccines recommended annually?

Because the virus mutates in a way (antigenic drift) that makes each new strain not susceptible to last year's vaccine.

Name the endemic (deep) mycoses.

Blastomycosis (Blastomyces dermatitidis) Coccidioidomycosis (Coccidioides immitis) Cryptococcosis (Cryptococcus neoformans) Histoplasmosis

Gas gangrene is caused by which Clostridial species?

C. perfringens

A 24-year-old sexually active woman who uses an oral contraceptive recently underwent a successful course of antibiotic treatment for a gonococcal (Gonorrhea: a Gram-negative coccus Neisseria gonorrheae) infection. For the past two days, she has been experiencing intense vulvar and vaginal pruritus (itching), along with a thick "cheesy" vaginal discharge. The symptoms are sufficiently irritating that she seeks medical advice. Her vitals are normal. On physical examination via pelvic exam, the vulva is found to be swollen and erythematous. There are a number of adherent, dry, white, curd-like patches of material attached to the vaginal mucosa. There is no noticeable odor associated with the infection. No other remarkable findings were found. What is your diagnosis?

Candidiasis Candida albicans [yeast infection] --> vaginitis - post-successful antibacterial tx

Discuss the methods for, and the pitfalls of, diagnosing syphilis.

Chancre --> swabs can be taken looking for spirochetes. **Some patients are asymptomatic, and therefore screening tests are required: first a sensitive test (VDRL or RPR) followed by a specific anti-treponemal antibody test (FTA-ABS). Both tests require up to six weeks to become positive, and therefore, early tests may be negative. **There are also occasional false positives in some autoimmune diseases (such as lupus and rheumatoid arthritis), pregnancy, or with IV drug abuse, and false negatives in some cases (such as in tertiary syphilis). Anti-treponemal antibody tests are used as follow-ups to verify the positive RPR or VDRL. However, even after treatment, these remain positive, and therefore cannot be used in the future to determine whether a patient has been reinfected.

What are the first and second most common sexually transmitted diseases in the United States?

Chlamydia and N. gonorrhea

STI pathogen associated with Urethritis, prostatitis, and epididymitis in men, and salpingitis in women

Chlamydia trachomatis & Neisseria gonorrhea

What virus is responsible for cold sores? Shingles? Infectious mononucleosis?

Cold sores: Herpes Simplex Virus (HSV) Type I Shingles: Herpes Zoster Virus/ Varicella-Zoster Virus (VZV) Infectious mononucleosis: Ebstein-Barr Virus (EBV)

During which period of the natural course of an infection do the symptoms fade?

Convalescence

A 5-year-old African American boy presents to his doctor with nausea and vomiting, hoarseness, and loud, rapid breathing. Physical exam reveals a swollen neck, a grey inflammatory membrane in the tonsillar area, and strider. At 24 hours, his cultures grew anaerobic, gram-positive bacilli. What is the pathogen? -Bordetella pertussis -Listeria monocytogenes -Cornybacterium diptheriae -Nocardia

Cornybacterium diptheriae

What virus is most likely to cause gastroenteritis on a cruise ship? The common cold during school year? Involve the parotids and gonads?

Cruise ship: Norwalk/ Norovirus Common cold at school: Rhinovirus Parotid/ Gonad involvement: Mumps

What are the laboratory tools used in investigating the cause of infection?

Cultures Stains: acid-fast and Gram (cell shape) Antigen-expression Antibody-incitation PCR

What are the two most important traditional techniques used to identify organisms?

Cultures & Gram stains

Epstein-Barr virus (EBV)

DNA virus - establishes latent infection in B cells via CD21

All of the following are characteristics of fungi EXCEPT: -Deep mycoses are acquired by skin contact -Consist of multicellular filaments (molds) & budding forms (yeasts) -Opportunistic mycoses can cause fatal systemic disease in the immunosuppressed -Superficial mycoses are common and confined to skin, hair, & nails

Deep mycoses are acquired by skin contact

How do infectious agents spread?

Direct contact Ingestion Indirect contact Droplets Vectors

Name several transformative viruses and their associated cancers.

EBV: non-Hodgkin lymphoma & nasopharyngeal carcinoma HPV: cervical cancer HBV& HCV: hepatocellular cancer HIV: several tumors, and in combination... Kaposi sarcoma associated herpes virus (KSHV-8): Kaposi sarcoma.

Inflammatory cells associated with infection: Helminths

Eosinophils

An organism called Bacillus cereus grows in reheated rice and can cause food poisoning very quickly within four hours. Is it more likely that endotoxin or exotoxin causes this disease?

Exotoxin, preformed, similar to that to Staphylococcus aureus

A new teenage mother refuses antibiotic treatment for her newborn. What is the newborn at risk for?

Eye infection & blindness

T/F: Candida is the most common endemic fungal infection.

FALSE: Candida is not endemic.

T/F: Condyloma lata is a benign, cauliflower-like growth of the cervical, vaginal, or vulvar squamous mucosa caused by HPV.

FALSE: Condyloma acuminatum is caused by HPV; Condyloma lata is caused by syphilis.

T/F: Molecular techniques are now considered the "gold standard" for identification of bacteria.

FALSE: Cultures

T/F: Most exotoxins come from living Gram-negative bacteria and can cause vascular collapse.

FALSE: Endotoxins

T/F: Host immunity always decreases virulence.

FALSE: Host immunity does not always decrease virulence, and the host response may actually induce additional inflammation and damage.

T/F: Immunity against reinfection with STIs prevents patients from acquiring the same STI a second time.

FALSE: Immunity against reinfection is often not achieved, making reinfection possible.

T/F: In testing for TB, a PPD (purified protein derivative) test of less than 15mm is always considered negative.

FALSE: In high-risk/ immunocompromised patients, it would be considered positive.

T/F: TB has no predilection for ethnic groups.

FALSE: More common in AA, Alaskan Inuit, Native Americans, and Southeast Asian descendants.

T/F: Viruses are the only obligate intracellular pathogens.

FALSE: Some bacteria--Chlamydia & Rickettsia

T/F: Vaccination against viruses increases cancer risk.

FALSE: it decreases risk

T/F: Mycobacterium leprae is the most virulent mycobacterium.

FALSE: uncommonly infects

Match the following manifestations with the proper parasite pathogen Filariasis __________ Pinworm infestation ____________ Trypanosomiasis ____________ Pork tapeworm disease ______________ Hookworm disease ___________ -Intense anal itching -Subcutaneous & lymphatic invasion -Periorbital edema with hepatosplenomegaly (liver & spleen enlargement) -Intestinal bleeding & anemia -Brain cysts

Filariasis Subcutaneous & lymphatic invasion Pinworm infestation Intense anal itching Trypanosomiasis Periorbital edema with hepatosplenomegaly (liver & spleen enlargement) Pork tapeworm disease Brain cysts Hookworm disease Intestinal bleeding & anemia

A 42-year-old man who works for a local construction contractor develops a sizable and painful swollen area on the back of his neck. The swollen area is painful and large enough that is causes him considerable discomfort if he tries to button his shirt collar. A ,mild fever adds to the man's discomfort, so he comes to your walk-in clinic for advice. His vitals are normal, except for some fever (38.9ºC/ 102ºF). The swollen area on his neck is located at the hairline and measures 2.4 x 3.7 cm. The center of this area is somewhat soft to the touch and appears to contain a substantial amount of pus. The overall appearance of the swollen area is that of an unusually large pustule surrounded by a distinct rash. There are not other remarkable findings. The man is asked about his medical history. He remembers that, several days ago, his wife noticed some minor irritation surrounding the hair follicles in the area that is now swollen. Except for occasional appearances of boils on his skin over the past few years, the man has enjoyed very good health. What is your diagnosis?

Folliculitis [infected hair follicle] --> skin abscess/ carbuncle w/ pus - can swab after incision & drainage for further confirmation - suspected S. aureus in pus

How does temperature affect the form of fungus?

For some, the form of growth is temperature dependent. Cool temps (i.e., on skin): fungi grow as hypae Body/ High temps (i.e., deep infection): fungi grow in yeast form

Granulomas, or granulomatous inflammation, are most likely caused by what two types of organisms?

Fungi and Mycobacterium tuberculosis

Candida

Fungus - normally found on mucous membranes

Histoplasmosis

Fungus: fungal infection of the lungs

Name the organ systems most commonly affected by infections. What do they share in common?

GI tract, respiratory tract, genitourinary tract, & skin Direct contact with environment

Whooping cough

Gram (-) rod

Escherichia coli (E. coli)

Gram (-) rod; anaerobic

STI pathogen associated with Chancroid, papules, ulcers, and marked inguinal lymphadenopathy, which may abscess

Haemophilus ducreyi

STI pathogen associated with Crops of small, painful blisters in skin or mucosa, which fade in a week

Herpes simplex virus (HSV)

STI pathogen associated with Condyloma acuminatum or dysplasia and cancer of the cervix

Human papillomavirus (HPV)

Concerning viruses, which of the following are true? -Produce enzymes for metabolism -Intracellular parasite -Possess both RNA & DNA -Have a protein coat -Not affected by antimicrobials

Intracellular parasite Have a protein coat Not affected by antimicrobials Viruses DO NOT: -metabolize -produce BOTH DNA & RNA--they have either one or the other

Schistosomes can infect which organs?

Liver, vasculature of GI and genitourinary tracts

Inflammatory cells associated with infection: Fungi

Lymphocytes & Monocytes and Granulomas

Inflammatory cells associated with infection: Mycobacteria

Lymphocytes & Monocytes and Granulomas

Inflammatory cells associated with infection: Viruses

Lymphocytes and Monocytes

What is the most common protozoal infection in the world? In the United States?

Malaria; Giardia

A 12-year-old male is brought to his pediatrician's office by his mother. She reports that he has a fever, cough, and congestion. His physical exam is positive for conjunctivitis, a maculopapular rash, and Koplik spots on the oral mucosa. Which disease has he contracted, which could have been prevented by vaccination? -Poliomyelitis -Mumps -Measles -Rubella

Measles

Inflammatory cells associated with infection: Bacteria

Neutrophils

Helminths (worms)

Parasite

Scabies

Parasite

Eosinophilic inflammation is most likely caused by what type of infection?

Parasites

Diagnosis of which of the following worm infections is made by pressing clear acetate tape to the perianal region and examining it microscopically? -Hookworm -Pinworm -Tapeworm -Flatworm

Pinworm

What is the likely cause of disease in a patient with a recent travel history to sub-Saharan Africa, episodes of fever and jaundice occurring every 48-72 hours in a peripheral blood smear that reveals both anemia and the caustic agent? -Plasmodium -Giardia lamblia -Entamoeba histolytica -Trypanosome

Plasmodium

What virus is responsible for invading motor neurons in the brain or spinal cord, causing paralysis? -Poliomyelitis -Measles -Mumps -Rubella

Poliomyelitis

How does each stage of syphilis manifest?

Primary syphilis: Chancre Secondary syphilis: via skin rash & genital condyloma lata Latent syphilis: subclinical Tertiary syphilis: brain and vascular disease

What are the stages and pathological findings of Mycobacterium tuberculosis?

Primary tuberculosis initially presents as a Ghon tubercle, and a Ghon complex when mediastinal (hilar) lymph nodes are also infected. If the initial infection is controlled, it becomes latent. If the disease is not controlled... Primary progressive tuberculosis is the result, presenting with various organs containing hundreds or thousands of tiny whitish lesions that look like millet seeds. Secondary (reactivation) TB manifests with lesions in the apex of the lung, with less numerous, larger granulomatous lesions with central cores of caseous necrosis.

Which of the following is a corrupt form of normal brain protein, and responsible for Creutzfeldt-Jakob and mad cow disease: -Virus -Bacteria -Worm -Prion

Prion

What are the major categories of infectious agents?

Prions Viruses Bacteria Fungi Parasites (incl. protozoa, helminths, & ectoparasites)

All of the following are true of endotoxins EXCEPT: -Found in Gram (-) bacteria -Produce generalized effects, fever, & malaise -Release enzymes that cause local damage -Affect the circulatory system, causing vascular collapse -None of the above; all are true

Release enzymes that cause local damage

What is the most common cause of infection-associated death? -Respiratory infection -Diarrheal disease caused by infection (C. diff) -HIV/AIDS -Malaria

Respiratory infection

HIV

Retrovirus

What is the ectoparasite responsible for the transmission of Leishmaniasis? -Deer ticks -Fleas -Sandflies -Mosquitos

Sandflies

A 20-year-old college student, newly moved into the dorms, visits the campus clinic. She is concerned about all the small intensely itchy red bumps on her wrists and on the webs of her fingers. Skin scrapings confirm a diagnosis of which of the following infectious agents? -Lice -HPV -Scabies -Molluscum contagiosum

Scabies - infestation of the skin mite Sarcoptes scabiei - lives only in the skin of humans; passed by direct contact - caused intensely itchy (pruritic) red papules (small bumps) around the wrists, waistline, genitals, and the webs of fingers Dx: clinical; insect in skin scrapings Tx: topical drugs

Which of the following parasitic diseases causes the most morbidity and mortality worldwide? -Filariasis -Schistosomiasis -Trichinosis -Echinococcosis

Schistosomiasis - caused by one of several flukes from the Schistosoma family - affects about 4% of the world population; second only to malaria in terms of death and disability - infects the vasculature of the GI and genitourinary tract

Are most cases of TB primary or secondary TB?

Secondary: - 95% of clinical TB - arises from dormant primary TB

What are ectoparasites?

Small, insect-like creatures that attach to/ live in the skin (e.g., fleas, ticks, bedbugs, lice)

A 14-year-old Caucasian female presents to the emergency room complaining of fevers, aches, and diarrhea of several days duration. Her body is covered in a sunburn-like rash. Her mother, who has accompanied her to the hospital, states that her daughter recently started her period and has been using tampons. What is the likely pathogen? -Streptococcus pneumonia -Staphylococcus aureus -Rickettsiae rickettsia -Yersinia pestis

Staphylococcus aureus

A 14-year-old caucasian female presents to the ER complaining of fevers, aches, and diarrhea of several days duration. Her body is covered in a sunburn-like rash. Her mother, who has accompanied her to the hospital, states that her daughter recently started her period and has been using tampons. What is likely the pathogen? -Staphylococcus aureus -Haemophilus influenza -Candida albicans -Streptococcus pneumoniae

Staphylococcus aureus

A 2-year-old Hispanic male presents to his physician with blisters, some of which have ruptured and coalesced into small patches of red, "honey-crusted" lesions covered with dry exudate. Gram stain of fluid isolated from the blisters reveals Gram-positive cocci in long chains. What is the pathogen? -Candida -Staphylococcus aureus -Rickettsiae rickettsia -Streptococcus pneumonia

Streptococcus pneumonia

T/F: A patient with gonococcus should be treated for Chlamydia.

TRUE

T/F: An epidemic is one of diseases found in a geographic area above normal levels.

TRUE

T/F: Anaerobic bacteria are present in the mouth and are responsible for aspiration pneumonia.

TRUE

T/F: Anti-syphilis antibodies remain present for a lifetime.

TRUE

T/F: Chlamydia can be cured with a single does of antibiotics.

TRUE

T/F: Cooking pork prevents trichinosis.

TRUE

T/F: Echinococcus infects the liver and is acquired by ingesting contaminated food.

TRUE

T/F: Gram-positive bacteria = PURPLE; Gram-negative bacteria = PINK.

TRUE

T/F: Intestinal nematodes are the most common parasitic infection in the world.

TRUE

T/F: Staphylococcus and Streptococcus are Gram-positive bacteria that can infect a number of different organs.

TRUE

T/F: Vaccinations against viruses have decreased the incidences of many viral diseases.

TRUE

T/F: Virulence is the ability to cause disease.

TRUE

Define tropism.

The tendency for an organism to infect a particular tissue.

Which of the following statements regarding prions is true? -They are intracellular parasites -They are proteinaceous particles, not living metabolism -They require specialized nutrients for their metabolism -Acquired only by ingestion of contaminated tissue

They are proteinaceous particles, not living metabolism

A 6-year-old male is seen in his pediatrician's office with his mother who reports that he is refusing to eat. A quick physical exam reveals herpangina (blisters in the oral cavity) as well as a rash on the palms of his hands & the soles of his feet. What treatment do you prescribe? -Treatment is supportive; you prescribe fluid & analgesics (aspirin) -Antibiotics -Antivirals -A vaccination to prevent further infection

Treatment is supportive; you prescribe fluid & analgesics (aspirin)

STI pathogen associated with Ulcer, rash on the palms and soles, damage to aorta and CNS

Treponema pallidum

Name the crucial difference between viruses and bacteria.

Viruses: obligate intracellular parasites made of protein and lack a cell wall. Bacteria: live outside of cells (not all do); more complex structures with a cell wall.

What mode of transmission is responsible for the infections of Lyme disease?

tick bites