04 - Anaerobes, Uncultivatable Bacteria & Virology (MLS Exam #4)

Question 1

Define

Anaerobe

Answer 1

A bacterium able to replicate in the absence of oxygen.

Question 2

Define

Aerotolerant anaerobe

Answer 2

Anaerobes that can survive a short exposure to oxygen but will not be able to perform metabolic processes unless placed into an anaerobic environment.

Question 3

Define

Obligate or strict anaerobe

Answer 3

Anaerobes that are killed almost immediately in the presence of oxygen.

Question 4

Define

Exogenous anaerobes

Answer 4

Anaerobes that exist outside the bodies of animals and the infections they cause are termed exogenous infections.

They can be found in soil, in freshwater and saltwater sediments,

Exogenous anaerobic infections are usually caused by gram-positive, spore-forming bacilli belonging to the genus Clostridium. Clostridia initiate infection when spores are ingested by way of contaminated food or gain access to the body through open wounds contaminated with soil.

Question 5

Define

Endogenous anaerobes

Answer 5

Anaerobes that exist inside the bodies of animals and are the source of endogenous infections.

The anaerobes most frequently isolated from infectious processes in humans are those of endogenous origin.

Question 6

Discuss the significance of anaerobes in the infectious process.

Answer 6

• Anaerobes outnumber aerobes on mucosal surfaces, such as the linings of the oral cavity, gastrointestinal (GI) tract, and genitourinary (GU) tract. These heavily colonized surfaces are the usual portals of entry into the tissues and bloodstream for endogenous anaerobes.
• Under ordinary circumstances, microorganisms that are members of the microbiota do not cause disease, and many actually can be beneficial.
• However, when some of these organisms gain access to usually sterile body sites, such as the bloodstream, brain, and lungs, they can cause serious or even fatal infections.

Question 7

Define normal anaerobic flora for specimen types

Skin

Answer 7

Indigenous members of the skin microbiota include anaerobes that colonize the sebaceous glands and hair follicles.

Propionibacterium, peptostreptococci, Cutibacterium (Propionibacterium) acnes

Question 8

Define normal anaerobic flora for specimen types

Intestinal tract

Answer 8

• It is estimated that 500 to 1000 different species of bacteria live in the GI tract. Microbiota studies have found that anaerobes outnumber facultative anaerobes by a factor of 1000 : 1.
• Any infection in the peritoneal cavity would likely be caused by organisms that have escaped from the GI tract.

Bifidobacterium, Eubacterium/ Eggerthella, Clostridium, peptostreptococci, Bacteroides fragilis group, Parabacteroides, Bilophila, Campylobacter, Fusobacterium, Porphyromonas, Prevotella, Sutterella, Veillonella

Question 9

Define normal anaerobic flora for specimen types

Upper respiratory tract and Oral Cavity

Answer 9

Of the bacteria present in saliva, nasal washings, and gingival and tooth scrapings, 90% are anaerobes.

Actinomyces, Eubacterium/ Eggerthella, peptostreptococci, Campylobacter, Fusobacterium, Prevotella, Bifidobacterium, Porphyromonas, Veillonella

Question 10

Define normal anaerobic flora for specimen types

Genitourinary tract

Answer 10

• Although anaerobic bacteria colonize the distal urethra, they are not considered to be a cause of uncomplicated urinary tract infections.
• Similarly, 50% of the bacteria in cervical and vaginal secretions are anaerobes.
• GU swabs and voided or catheterized urine specimens are unacceptable for anaerobic bacteriology because recovery of these organisms would not distinguish whether they were present as pathogens or as endogenous microbiota.

Peptostreptococci, Bifidobacterium, Fusobacterium, Lactobacillus, Mobiluncus, Prevotella, Veillonella

Question 11

Discuss

Factors That Predispose Patients to Anaerobic Infections

Answer 11

Generally, infectious diseases involving anaerobic bacteria follow some type of trauma to protective barriers such as the skin and mucous membranes. Trauma at these sites allows anaerobes of the endogenous biota (or in some cases, soil anaerobes) to gain access to deeper tissues.

Human or animal bite wounds. Aspiration of oral contents into the lungs after vomiting. Tooth extraction, oral surgery, or traumatic puncture of the oral cavity. Gastrointestinal tract surgery or traumatic puncture of the bowel. Genital tract surgery or traumatic puncture of the genital tract. Introduction of soil into a wound.

Question 12

Discuss the physical characteristics that are found when anaerobes are recovered in the infectious process.

Answer 12

*Infectious processes involving anaerobes are usually purulent, with many polymorphonuclear leukocytes present. (not always)
* Infection in close proximity to a mucosal surface
* Presence of foul odor
* Presence of large quantity of gas
* Presence of black color or brick red fluorescence
* Presence of sulfur granules

Question 13

Many of the infectious processes involving anaerobes consist of mixtures of obligate anaerobes or mixtures of obligate or aerotolerant anaerobes and facultative organisms, this is called what?

Answer 13

Polymicrobial infection

Question 14

Associate the causative anaerobic organism with the clinical infection.

Food poisoning

Answer 14

Clostridium perfringens

C. perfringens is associated with two types of food poisoning— type A, a relatively mild and self-limited GI illness, and type C, a more serious but rarely seen disease. C. perfringens foodborne disease usually follows the ingestion of large numbers of enterotoxin-producing strains in contaminated food.

Question 15

Associate the causative anaerobic organism with the clinical infection.

Botulism

Answer 15

Clostridium botulinum

• Results from the ingestion of preformed botulinum toxin,Botulinum toxin is an extremely potent neurotoxin; only a small amount produces death.
• Weakness and paralysis are the main features of botulism.
• The food sources involved commonly in botulism include home-canned goods.
• Botulinum toxin type A (Botox) is also used medically to treat chronic migraines and temporarily improve facial wrinkles.

Question 16

What is a common source of infant botulism?

Answer 16

Raw Honey

Question 17

Associate the causative anaerobic organism with the clinical infection.

Tetanus

Answer 17

Clostridium tetani

• Tetanus occurs when spores in the environment enter the skin through puncture wounds.
• The clinical manifestations of tetanus are attributed to the neurotoxin tetanospasmin produced by Clostridium tetani. Tetanospasmin acts on neurons, preventing the release of inhibitory and excitatory neurotransmitters. This results in a spastic type of paralysis, with continuous muscular spasms. leading to trismus (lockjaw), risus sardonicus (distorted grin), and difficulty breathing.
• Therapy for tetanus requires the injection of antitoxin, muscle relaxants, and intensive therapy.

Question 18

Associate the causative anaerobic organism with the clinical infection.

Myonecrosis (gas gangrene)

Answer 18

C. perfringens (the most common cause)

• Myonecrosis, or gas gangrene, usually occurs when organisms contaminate wounds, through trauma or surgery.
• C. perfringens, C. histolyticum, C. septicum, C. novyi, and C. bifermentans have all been associated with myonecrosis.
• C. perfringens is the most common cause. Under favorable conditions, the organisms are able to grow, multiply, and release potent exotoxins. In gas gangrene exotoxins, such as α-toxin produced by C. perfringens, cause necrosis of the tissue and allow deeper penetration by the organisms.
• The onset and spread of myonecrosis can be rapid, and extensive surgical debridement of the necrotic tissue is often required.** If treatment is delayed, amputation of the affected limb is not uncommon.**

Question 19

Associate the causative anaerobic organism with the clinical infection.

Pseudomembraneous colitis

Answer 19

Clostridioides difficile

• This organism is part of the GI biota in about 5% of individuals
• Following antimicrobial therapy, many bowel biota organisms other than C. difficile are killed, thus allowing C. difficile to multiply with less competition and produce high levels of two toxins: toxin A, an enterotoxin, and toxin B, a cytotoxin.
• Bloody diarrhea with associated necrosis of colonic mucosa is seen in patients with pseudomembranous colitis. C. difficile is a common cause of health care– associated (nosocomial) infection.

Question 20

Associate the causative anaerobic organism with the clinical infection.

Actinomycosis

Answer 20

Actinomyces spp. (A. israelii is the most common)

Actinomycosis is a chronic, granulomatous, infectious disease characterized by the development of sinus tracts and fistulae, which erupt to the surface and drain pus that may contain so-called sulfur granules, dense clumps of bacteria that may be colored.

Question 21

Associate the causative anaerobic organism with the clinical infection.

Lemierre’s disease

Answer 21

Fusobacterium necrophorum

Lemierre disease, a syndrome of thrombophlebitis of the jugular vein that occurs rarely following group A streptococcal pharyngitis, is caused by F. necrophorum. The streptococcal infection produces a peritonsillar abscess containing a number of bacterial species. The abscess aids F. necrophorum in penetrating the tissue to reach the jugular veins.

Question 22

Associate the causative anaerobic organism with the clinical infection.

Acne

Answer 22

Propionibacterium acnes

Question 23

Which nonselective media should be used for anaerobic cultures?

Answer 23

Anaerobic blood agar (CDC)

An enriched medium containing sheep blood for enrichment and detection of hemolysis, vitamin K (required by some Porphyromonas spp.), and yeast extract

Question 24

What selective media is used to select for Bacteroides fragilis group?

Answer 24

Bacteroides bile esculin agar (BBE)

• Containing gentamicin (which inhibits most aerobic organisms)
• 20% bile (which inhibits most anaerobes)
• Esculin; used primarily for rapid isolation and presumptive identification of members of the B. fragilis group
• Black colonies (because of esculin hydrolysis)

Question 25

Name the selective medium containing sheep red blood cells and phenylethyl alcohol; used primarily to suppress the growth of any facultative, gram-negative bacilli (e.g., Enterobacteriaceae) that might be present in the clinical specimen, especially swarming Proteus spp.

Answer 25

Phenylethyl agar (PEA) ## Footnote Supports growth of almost all obligate anaerobes (gram-positive and gram-negative)

Question 26

What is the composition of anaerobic gas?

Answer 26

* 5% hydrogen * 80-90% nitrogen * 5-10% carbon dioxide (CO2)

Question 27

Name 3 ways in which ANO2 conditions can be acheived?

Answer 27

1. Anaerobic chambers 2. Anaerobic jars 3. Anaerobic bags

Question 28

How long should primary anaerobic cultures incubate before an initial read?

Answer 28

48 hours

Question 29

How long are anaerobic cultures routinely held for?

Answer 29

5-7 days (5 days at CCF) | * 10-14 to rule out Actinomyces or Cutibacterium acnes

Question 30

When anaerobes are suspected, what steps must be performed and recorded for each colony morphotype present on the anaerobic blood agar plate to initiate presumptive identification of the isolates?

Answer 30

1. Describe the colony morphology and note the media in which growth occurred. (CDC, BBE) 2. Describe the Gram stain reaction and cell morphology. 3. Set up an aerotolerance test 4. Perform MALDI-TOF (if available)

Question 31

# Define Aerotolerance Testing

Answer 31

Determines whether a microorganism isolated under anaerobic conditions is a strict or facultative anaerobe. ## Footnote Subculture the suspected isolate to both aerobic (BAP) and anaerobic (CDC) media and observe the actual atmospheric requirements of the organism.

Question 32

Interpretation of Aerotolerance Test Results

Answer 32

Question 33

# Describe the principle and application of the test. Fluorescence

Answer 33

Porphyromonas and Prevotella fluoresce brick red under long-wave (366-nm) UV light. (Wood's lamp)

Question 34

# Describe the principle and application of the test. Catalase

Answer 34

Helps differentiates aerotolerant strains of Clostridium (catalase negative) from Bacillus (catalase positive). | 15% hydrogen peroxide

Question 35

# Describe the principle and application of the test. Spot indole test

Answer 35

The spot indole test is useful in identifying **C. acnes (indole positive)** from the similar Propionibacterium spp. (indole negative).

Question 36

# Describe the principle and application of the test. Urease test

Answer 36

C. sordellii is the only Clostridium species that is urease positive.

Question 37

# Describe the principle and application of the test. Lipase production (EYA)

Answer 37

****Lipase-positive organisms produce a colony covered with an iridescent, multicolored sheen, sometimes described as resembling the appearance of gasoline on water or mother of pearl. **Fusobacterium necrophorum**

Question 38

# Describe the principle and application of the test. Lecithinase production (EYA)

Answer 38

Lecithinase cleaves lecithin found in egg yolk, releasing insoluble fat (diglyceride) that produces an opaque zone around the colony. **C. perfringens**

Question 39

# Describe the principle and application of the test. Sodium Polyanethol Sulfonate Disk (SPS)

Answer 39

(SPS) disk aids in the identification of anaerobic gram-positive cocci.

Question 40

An SPS-sensitive, gram-positive anaerobic coccus can be presumptively identified as

Answer 40

Peptostreptococcus anaerobius

Question 41

An SPS-resistant, spot indole– positive, gram-positive anaerobic coccus can be presumptively identified as

Answer 41

Peptoniphilus asaccharolyticus

Question 42

Name 2 rapid anaerobic identification panels.

Answer 42

1. RapID ANA 2. API 20 A

Question 43

Discuss antimicrobial susceptibility testing considerations for anaerobic bacteria.

Answer 43

Beacuse the isolation, identification, and susceptibility testing of anaerobes is slow, when physicians suspect an anaerobic infection, they routinely select a broad-spectrum agent for empiric therapy that will cover most anaerobes, pending outcome of the culture. ## Footnote Carbapenems, metronidazole, and the β-lactam combination antibiotics continue to have activity against most anaerobes and are used as empiric therapy.

Question 44

When should susceptibility testing be performed on anaerobes?

Answer 44

When it is recovered as a pure culture in a sterile site. ## Footnote * Brain abscess * Endocarditis * Infection of a prosthetic device or vascular graft * Joint infection * Osteomyelitis * Bacteremia

Question 45

A test for beta-lactamase production VIA cefinase is disc is performed on what type of anaerobic organisms?

Answer 45

Anaerobic GNB (other than B. fragilis group)

Question 46

What method(s) are used to perform anaerobic susceptibility testing?

Answer 46

1. E-test 2. Microbroth dilution panels

Question 47

Other than susceptibilty testing, how can anaerobe-associated diseases be treated?

Answer 47

* Surgery * Hyperbaric oxygen therapy * Antitoxins * Refractory CDAD can be treated with fecal microbiota transplant

Question 48

What are some indications that anaerobes may be present in a Culture?

Answer 48

* A foul odor on opening an anaerobic jar or bag. * Colonies present on the anaerobically incubated blood agar plates but not on the CO2-incubated blood plate * Good growth (> 1 mm in diameter) of black colonies on a BBE agar plate, characteristic of members of the B. fragilis group * Double zone of hemolysis on CDC (ANO2) suggestive of C. perfringens

Question 49

# Presumptively Identify the Gram-Positive Anaerobes * Colony morphology: Large, flat colonies; **barnyard odor**, chartreuse fluorescence * Gram stain: Thin rods, rare spores

Answer 49

Clostridium difficile

Question 50

# Presumptively Identify the Gram-Positive Anaerobes * Colony morphology: Large, irregular-shaped, **double zone of β-hemolysis** * Gram stain: Boxcar, large, square rods

Answer 50

Clostridium perfringens

Question 51

# Presumptively Identify the Gram-Positive Anaerobes Colony morphology: Smoothly swarming Gram stain: Thin rods, subterminal spores

Answer 51

Clostridium septicum ## Footnote Is often a marker for gastrointestinal cancer

Question 52

# Presumptively Identify the Gram-Positive Anaerobes Colony morphology: Smoothly swarming but slow growing Gram stain: Swollen terminal spores Spot Idole: Positive

Answer 52

Clostridium tetani

Question 53

Which anaerobes are most commonly associated with a gram stain of gram positive cocci?

Answer 53

Peptostreptococcus spp., Finegoldia, or Peptoniphilus

Question 54

What anaerobe has a gram stain of Gram negative cocci?

Answer 54

Viellonella spp.

Question 55

What anaerobe has a gram stain of "fusiform" (thin with pointed ends) GNB and colonies that resemble "breadcrumbs"?

Answer 55

Fusobacterium nucleatum

Question 56

What anaerobic species has a gram stain of branching, filamentous, non-spore forms gram positive rods?

Answer 56

Actinomyces spp.

Question 57

Which species of Actinomyces form "molar tooth" colonies?

Answer 57

Actinomyces israelii

Question 58

Describe Actinomycosis

Answer 58

Actinomycosis is a chronic, granulomatous, infectious disease characterized by the development of sinus tracts and fistulae, which erupt to the surface and drain pus that may contain so-called **sulfur granules**, dense clumps of bacteria that may be colored.

Question 59

Actinomyces has a similar gram stain to Nocardia. What stain could be used to differentiate the two?

Answer 59

AFB stain. Nocardia is Acid fast postive. Actinomyces is acid fast negative.

Question 60

Which anaerobe has a gram stain of non-spore forming "spidery" gram positive bacilli and the colonies described as white and "puffy"?

Answer 60

Cutibacterium acnes

Question 61

What reactions does Cutibacterium acnes have to spot indole and catalase?

Answer 61

Positive for both

Question 62

Cutibacterium acnes is a slow growing organism, typically incubated for 10-14 days, and is associated with what type of infection?

Answer 62

Prosthetic joint infection

Question 63

What organism is associated with IUD (intrauterine device) infections?

Answer 63

Actinomyces

Question 64

How long should a culture be incubated for when trying to rule out Actinomyces or Cutibacterium acnes?

Answer 64

10-14 days

Question 65

What anaerobe has a gram stain of pleomorphic GPB that looks like a "dog biscuit"?

Answer 65

Bifidobacterium

Question 66

Which anaerobic organism may be considered a contaminant if isolated from a blood culture bottle?

Answer 66

Cutibacterium acnes | It can be part of skin flora

Question 67

Which anaerobic species is associated with spore forming GPB?

Answer 67

Clostridium spp

Question 68

What is the gram stain of Bacteroides spp?

Answer 68

Bacteroides spp. colonies reveal gram-negative coccobacilli or bacilli.

Question 69

To be diagnosed with C. diff colitis, you must test positive for what?

Answer 69

Toxins

Question 70

# Describe Spirochetes

Answer 70

Slender, flexuous, helically shaped, unicellular bacteria ranging in size from 0.1 to 0.5 µm wide and from 5 to 20 µm long, with one or more complete turns in the helix.

Question 71

How do humans contract disease by leptospires?

Answer 71

Through contact with the **urine of an infected animal**. The usual portal of entry being conjuctiva or abrasions or cuts in the skin.

Question 72

Leptospirosis is also known as what disease?

Answer 72

**Weil disease** ## Footnote Severe systemic disease includes renal failure, hepatic failure, and intravascular disease and can result in death.

Question 73

What media is used to isolate leptospires?

Answer 73

Fletcher's media

Question 74

What organism is the causitive agent of Lyme disease?

Answer 74

Borrelia burdorferi

Question 75

What vector transmits Lyme disease?

Answer 75

Ticks known as Ixodes

Question 76

Explain the three stages of Lyme disease.

Answer 76

Stage 1: Erythema migrans (localized circular rash at innoculation site) Stage 2: Neurologic or cardiac involvement: most commonly facial nerve palsy Stage 3: Joints most commonly involved (arthritis)

Question 77

Describe the diagnostic method used to diagnose Lyme disease

Answer 77

IFA or EIA and confirmation with Western blot

Question 78

Name the disease associated with Borrelia recurrentis

Answer 78

Relapsing fever. ## Footnote Fevers that subside after 3-6 days and then return in 1 week

Question 79

What vector is associated with **endemic** relapsing fevers?

Answer 79

Ticks

Question 80

What vector is associated with **epidemic** relapsing fevers?

Answer 80

Louseborne | Lice ## Footnote Louseborne fever is transmitted via the body louse, **Pediculus humanus,** and humans are the only reservoir.

Question 81

What is the causative agent of syphilis?

Answer 81

Treponema pallidum

Question 82

Describe the microscopy used to visualize T. pallidum in clinical specimens.

Answer 82

The organisms are too thin to be observed by bright-field microscopy, so spirochetes are illuminated against a dark background. **Dark-field microscopy** requires considerable skill and experience; however, demonstration of motile treponemes in material from the chancre is diagnostic for primary syphilis.

Question 83

Describe the 3 stages of the disease caused by T. pallidum.

Answer 83

1. Primary: A chancre or ulcer appears at site of innoculation and lasts 1-8 weeks 2. Secondary: Flulike symptoms, swollen lymph nodes and rash 3. Tertiary or late stage: 1/3 of untreated patients progress to 3rd stage; lesions (gummas) seen in bone, skin & other tissues.; neuro & cardiovascular involvement

Question 84

Name the drug of choice for treating patients with syphilis

Answer 84

Penicillin

Question 85

The Life cycle of Chlamydia.

Answer 85

Question 86

Chlamydia's life cycle has a unique growth cycle that involves two distinct forms, an elementary body (EB), and a reticulate body (RB), which form is infectious?

Answer 86

The elementary body (EB) is infectious, and the reticulate body (RB) is noninfectious.

Question 87

C. trachomatis causes what type of eye infection?

Answer 87

C. trachomatis causes the chronic eye infection **trachoma**, the number one cause of preventable blindness in the world. ## Footnote Trachoma is a chronic disease that begins as follicular conjunctivitis. The chronic inflammation causes the eyelid to turn inward, which results in continual abrasion to the cornea from the eye lashes. The condition results in scarring and ulceration of the cornea. This can result in secondary bacterial infection and blindness.

Question 88

Name the organism that is an obligate intracellular parasite that infects the non-ciliated, columnar or transitional epithelial cells of the conjunctiva, respiratory, UG tract or rectum.

Answer 88

Chlamydia spp.

Question 89

Chlamydia is usually susceptible to what drugs?

Answer 89

Doxycycline

Question 90

What is the most common STD in the United States whose infection is often asymptomatic?

Answer 90

Chlamydia trachomatis

Question 91

Diseases associated with C. trachomatis.

Answer 91

Associated with eye trachoma, lymphogranuloma venereum (LGV), PID, and Reiter syndrome.

Question 92

How is the Chlamydia detected?

Answer 92

Nucleic Acid Hybridization and Amplification Assays. NAATs ## Footnote * While cell culture is the gold standard: it has been replaced by NAATs because of it's higher sensitivity and specificity. * Can be performed on urine and urethral/cervical swabs. * Can detect two STDs in one sample— gonorrhea and C. trachomatis infection. * Technicially less demanding. * However, as of yet no NAAT has been approved for use on conjunctival, oropharyngeal, or rectal specimens.

Question 93

What strains of C. trachomatis are more invasive, producing a more serious infection and pronounced antibody response?

Answer 93

LGV Strains

Question 94

What type of species of Chlamydia is recognized as an important respiratory pathogen?

Answer 94

Chlamydophila pneumoniae | formally known as TWAR ## Footnote Respiratory pathogen known to be the cause of sinusitis, pharyngitis, acute respiratory disease, bronchitis and pneumonia. Implicated as a possible factor in asthma and cardiovascular disease. Resembles that of Mycoplasma pneumoniae

Question 95

Which organism causes **psittacosis, a contagious disease of birds** that is transmissible (especially from parrots) to human beings as a form of pneumonia?

Answer 95

Chlamydophila psittaci

Question 96

# Name the organism associated with the Rickettsial disease: Rocky Mountain Spotted Fever (RMSF) and the vector is a dog tick.

Answer 96

R. rickettsii ## Footnote Most severe of the Rickettsial infections. Acquired through tick bites (Dermacentor variabilis) in the USA – the bacteria then enter the blood stream and are phagocytosed where replication can occur intracellularly. Symptoms occur after 7 days of incubation – Rash (patches on wrists and ankles), fever, headache, nausea, etc. High mortality rate without treatment

Question 97

# Name the organism associated with the Rickettsial disease: Murine typhus and the vector is a flea.

Answer 97

R. typhi ## Footnote Humans scratch the bite of the flea, pushing flea stool into the wound, which contains the bacteria.

Question 98

# Name the organism associated with the Rickettsial disease: Epidemic typhus and the vector is a louse (Pediculus humanus).

Answer 98

R. prowazekii ## Footnote . Humans scratch the bite of the lice, pushing the lice stool into the wound, which contains the bacteria. Rash of the palms and soles of the feet occurs. Mortality in untreated patients can reach 40%.

Question 99

# Name the organism associated with the Rickettsial disease: Scrub typhus and the vector is a chigger.

Answer 99

Orientia

Question 100

# Name the organism associated with the Rickettsial disease: **Rickettsialpox**, the reservoir is the common house mouse, and the vector is the mouse **mite** Liponyssoides sanguineus.

Answer 100

R. akari

Question 101

# Name the organism associated with the Rickettsial disease: Human granulocytic anaplasmosis (HGA) and the vector is a deer tick.

Answer 101

Anaplasma phagocytophilum ## Footnote Note that As the cells divide within the phagosome, they develop into morulae (mulberry-like bodies; Fig. 24.11). Morulae are round to oval clusters of bacteria 1 to 3 µm in diameter. As the host cell ruptures, the morulae break into many individual EBs, which continue the infective cycle.

Question 102

# Name the organism associated with the Rickettsial disease: Human Granulocytic Ehrlichiosis (HME) and the vector is the lone star tick.

Answer 102

Erlichia

Question 103

# Name the organism: Causative agent of **Q fever** and can infect a wide range of vectors (ticks, birds, fish, livestock and other mammals).

Answer 103

Coxiella burnetii ## Footnote * Considered to be a facultative intracellular parasite. * Spore-former. * Highly contagious and considered a bioterrorism agent. * IFA of infected tissue is a reliable identification method

Question 104

# Name the organism: Cat scratch fever and the vector is a kitten.

Answer 104

Bartonella henselae

Question 105

True or False: Chlamydiae and rickettsiae are both obligate intracellular organisms.

Answer 105

True

Question 106

What organisms should be considered as possible causes of neonatal conjunctivitis?

Answer 106

N. gonorrhoeae and C. trachomatis

Question 107

What organisms are characterized by being the smallest free-living bacteria and lack a cell wall?

Answer 107

Mollicutes or Mycoplasma ## Footnote Mycoplasma and Ureaplasma are the two genera in the family Mycoplasmataceae.

Question 108

Mycoplasma pneumoniae causes which disease?

Answer 108

Primary atypical pneumonia (walking pneumonia)

Question 109

Mycoplasma hominis is associated with what disease?

Answer 109

Urogenital tract disease

Question 110

Ureaplasma urealyticum is associated with what disease?

Answer 110

Urogenital tract disease

Question 111

Why can't you gram stain Mycoplasma?

Answer 111

Because they lack a cell wall and do not retain the stain ## Footnote Often isolated on anaerobic media and after performing a gram stain on the tiny colony with a result of "no organisms seen", Mycoplasma should be suspected

Question 112

Mycoplasmas are generally slow-growing, highly fastidious, facultative anaerobes requiring complex media containing what for growth?

Answer 112

Cholesterol and fatty acids

Question 113

Which species of Mycoplasma form colonies with slightly raised centers, giving the classic “fried egg” appearance?

Answer 113

M. hominis

Question 114

Describe the structural components of viruses

Answer 114

At a minimum, viruses contain a viral genome of **ribonucleic acid (RNA) or deoxyribonucleic acid (DNA) and a protein coat— the capsid.** The genome can be double stranded (ds) or single stranded( ss).

Question 115

The genome and its protein coat together are referred to as what?

Answer 115

The nucleocapsid

Question 116

The entire virus particle is called what?

Answer 116

Virion

Question 117

How are viruses classified?

Answer 117

* Genome type (RNA or DNA) * Number of strands in the genome (ds or ss), * Morphology * Presence or absence of an envelope

Question 118

Viruses are obligate intracellular parasites. What does that mean?

Answer 118

They must be inside a living cell and use the host cell machinery to replicate.

Question 119

Describe the basic steps of viral replication

Answer 119

1. **Absorption**. In the first step for infection of a cell to occur, virions must absorb or **attach** to the cell surface. 2. **Penetration**. Viruses can penetrate the cell by several different mechanisms and penetration is virus dependent. 3. **Uncoating.**Once inside the cell, the virus loses its protein coat, releasing the genome. The viral genome then directs the host cell to make viral proteins and replicate the viral genome. 4. **Assembly or maturation of the virus particles.**The new virions are formed and then released by lysis if they are naked viruses or by budding if they are enveloped viruses.

Question 120

When should samples be collected for viral detection?

Answer 120

Viral shedding is highest in** early stages of infection** and decreases rapidly a few days after acute symptoms.

Question 121

What is the optimal specimen for viral detection?

Answer 121

For optimal recovery, specimens for viral isolation should be **collected from the affected site. ** ## Footnote For example, secretions from the respiratory mucosa are most appropriate for viral diagnosis of respiratory infections. Aspirates, or surface swabs, are usually appropriate for lesions.

Question 122

What types of swabs can and cannot be used for viral specimen collection?

Answer 122

* Swabs used must be made of Dacron or rayon. * Do not use Calcium alginate or wood shafted swabs. They can inhibit the replication of some viruses and can interfere with nucleic acid amplification tests.

Question 123

If a viral specimen must be frozen, what temperature should it be kept at?

Answer 123

–70 ° C ## Footnote –70 ° C. Specimens should never be stored at − 20 ° C because this temperature facilitates the formation of ice crystals that will disrupt the host cells and result in loss of viral viability. Repeated freeze– thawing cycles are to be avoided because they can also result in loss of viral viability.

Question 124

Define cytopathic effect (CPE) as it relates to viral identification

Answer 124

Many viruses produce distinctive and characteristic visual changes in infected cells referred to as a cytopathic effect (CPE). ## Footnote Some viruses produce a very characteristic CPE that can provide a presumptive identification of a virus isolated from a clinical specimen. For example, HSV grows rapidly on many different cell lines and frequently produces a CPE within 24 hours. A predominantly cell-associated virus, HSV produces a focal CPE (in which adjacent cells become infected) and plaques, or clusters of infected cells. The combination of rapid growth, plaque formation, and growth on many different cell types is presumptive evidence for the identification of HSV.

Question 125

Name 4 general types of cell cultures / lines used for viral isolation

Answer 125

1. HDF, human diploid fibroblasts 2. HEp2, human laryngeal carcinoma cell line 3. PMK, primary monkey kidney 4. RK, rabbit kidney

Question 126

Describe the four major methods the clinical laboratory uses to diagnose viral infections.

Answer 126

* Direct detection of the virus in clinical specimens (microscopy, EIA) * Nucleic acid– based detection (PCR) * Isolation of viruses in cell cultures (gold standard but seldom used) * Serologic assays to detect antibodies to virus

Question 127

Name the phenomenon where slight antigenic change is seen in influenza viruses over time because of minor mutations in the ssRNA.

Answer 127

Antigenic drift

Question 128

Name the phenomenon whereby an often-unexpected change occurs in influenza virus strains. This antigenic change is often so drastic that it triggers pandemics. Causes changes in H and N antigens.

Answer 128

Antigenic shift

Question 129

# Name that Virus Most cases are asymptomatic. Those that are symptomatic usually involve the respiratory tract, eye, or gastrointestinal tract.

Answer 129

Adenovirus | dsDNA ## Footnote Family: Adenoviradae

Question 130

# Name that Virus There are two species: HSV-1 and HSV-2. These viruses cause oral herpes, genital herpes, neonatal herpes, and ocular herpes. Also the leading cause of fatal sporadic encephalitis in the United States. Neonates are most at risk for HSV-2 encephalitis. HSV detection by culture is sensitive and is often positive in less than two days.

Answer 130

Herpes simplex viruses (aka Human herpesvirus 1 and Human herpesvirus 2) | dsDNA ## Footnote Family: Herpesviridae

Question 131

# Name that Virus Congenital infection can be significant. If the mother acquires primary infection during pregnancy irreversible damage could result to the fetus. As a result, this virus is one of the leading causes of mental retardation, deafness, and intellectual impairment. Infants may develop a blueberry muffin rash.

Answer 131

Cytomegalovirus (Human herpesvirus 5) | dsDNA ## Footnote Family: Herpesviridae

Question 132

# Name that Virus Virus infects B lymphocytes and stimulates the production of heterophile antibodies. Infection can present as infectious **mononucleosis**. Some cancers have been associated with this virus including Burkitt’s lymphoma. Atypical lymphocytes may been seen in hematological testing.

Answer 132

Epstein-Barr virus (Human herpesvirus 4) | dsDNA ## Footnote Family: Herpesviridae "kissing disease"

Question 133

# Name that Virus Causative agent of chickenpox and shingles. Skin scrapings are the best specimens.

Answer 133

Varicella-Zoster virus (human herpesvirus 3) | dsDNA ## Footnote Family: Herpesviridae

Question 134

# Name that Virus Associated with the childhood disease called roseola infantum.

Answer 134

Human herpesvirus 6 (HHV-6) | dsDNA ## Footnote Family: Herpesviridae

Question 135

# Name that Virus Associated with genital warts. Diagnosis is made from koilocytes on pap smears. Linked to cervical cancer.

Answer 135

Human papilloma virus (HPV) | dsDNA ## Footnote Family: Papillomaviridae

Question 136

# Name that Virus Infections are associated with Kaposi sarcoma.

Answer 136

Human herpesvirus 8 (HHV-8)

Question 137

# Name that Virus Causative agent of smallpox.

Answer 137

Variola virus | dsDNA ## Footnote Family: Poxviridae

Question 138

# Name that Virus The most recognized symptom of an infection caused by this virus is erythema infectiosum (also called fifth disease) - a rash on the cheeks. Some referred to it as a slapped cheek appearance.

Answer 138

Parvovirus B19 | ssDNA ## Footnote Family: Parvoviridae

Question 139

# Name that Virus Most common cause of viral gastroenteritis in infants and children.

Answer 139

Rotavirus | dsRNA ## Footnote Family: Reoviridae

Question 140

# Name that Virus A group of viruses transmitted by arthropods such as ticks and mosquitoes and can cause hemorrhagic fevers in humans.

Answer 140

Arboviruses

Question 141

# Name that Virus A group of viruses carried by rodents and can cause hemorrhagic fevers in humans

Answer 141

Arenaviruses

Question 142

# Name that Virus Causes gastroenteritis and is associated with outbreaks on cruise ships.

Answer 142

Norovirus

Question 143

# Name that Virus Novel strains of this group of viruses has been associated with severe acute respiratory syndrome (SARS).

Answer 143

Coronaviruses | ssRNA ## Footnote Family: Coronaviridae

Question 144

# Name that Virus Infections with these two viruses are rare, but almost always fatal due to hemorrhagic fevers.

Answer 144

Ebola and Marburg virus | ssRNA ## Footnote Family: Filoviridae

Question 145

# Name that Virus These viruses have a **segmented genome** and are classified based on two major surface glycoproteins: hemagglutinin (H) and neuraminidase (N). They attack ciliated epithelial cells lining the respiratory tract and cause the flu.

Answer 145

Influenza virus A, B, and C | ssRNA ## Footnote Family: Orthomyxoviridae

Question 146

# Name that Virus These viruses are the primary cause of respiratory disease in young children. Type 1 is the primary cause of croup.

Answer 146

Parainfluenza viruses (1 through 4) | ssRNA ## Footnote Family: Paramyxoviridae

Question 147

# Name that Virus ssCauses bilateral swelling of the parotid glands.

Answer 147

Mumps virus | ssRNA ## Footnote Family: Paramyxoviridae

Question 148

# Name that Virus This virus causes a stuffy nose, cough, and Koplik spots.

Answer 148

Measles virus (also known as rubeola) | ssRNA Family:Paramyxoviridae ## Footnote Koplik spots are white spots that appear on the mucous membranes of measles patients approximately 1 day before the appearance of the typical measles rash.

Question 149

# Name that Virus Most common cause of severe lower respiratory tract disease among infants and young children.

Answer 149

Respiratory syncytial virus (RSV) | ssRNA ## Footnote Family: Paramyxoviridae

Question 150

# Name that Virus Infection with this virus can be assumed if a child has a lower respiratory tract infection, but tests negative for respiratory syncytial virus, influenza viruses, and parainfluenza viruses.

Answer 150

Human metapneumovirus | ssRNA ## Footnote Family: Paramyxoviridae

Question 151

# Name that Virus Causes nausea and vomiting in neonates.

Answer 151

Enterovirus

Question 152

# Name that Virus Virus requires an RNA-dependent DNA polymerase to replicate and is T-lymphotropic (infects CD4+ T-cells). Patients are treated with highly active antiretroviral therapy (HAART).

Answer 152

HIV (human immunodeficiency virus)

Question 153

# Name that Virus Infection usually results after being bitten or scratch by a wild animal. Symptoms are flulike at first and then develop into mental status changes. Patients often experience hallucinations, paralysis, excessive salvation, hydrophobia, and bouts of terror.

Answer 153

Rabies virus

Question 154

# Name that Virus These viruses are a diverse collection of viruses grouped together because they all infect primarily the liver. Laboratory diagnosis is based on serologic markers.

Answer 154

Hepatitis A, B ,C, D,E, etc.

Question 155

# Name that Virus German measles

Answer 155

Rubella virus

Question 156

# Name that Virus The common cold

Answer 156

Rhinovirus

Question 157

# Name that Virus Infects the central nervous system and cause paralysis.

Answer 157

Polioviruses

Question 158

# Name that Virus Hand/foot/mouth disease: Small painful sores appear on the tongue, buccal mucosa, and soft palate and a rash on the hands, feet, and buttock.

Answer 158

Cosackievirus A

Question 159

How do retroviruses (e.g., HIV) replicate?

Answer 159

Retroviruses replicate with the enzyme reverse transcriptase, which uses viral RNA as a template to make a complementary DNA strand.

Question 160

Members of which family produce life-long latent infections?

Answer 160

Herpesviridae

Question 161

Which opportunistic infections or conditions are used as indicators of acquired immunodeficiency syndrome (AIDS)?

Answer 161

Some opportunistic infections and conditions associated with AIDS include candidiasis, cryptococcal meningitis, cryptosporidiosis, histoplasmosis, persistent HSV infections, mycobacterial infections, recurrent pneumonia, and Kaposi sarcoma.

Question 162

Which immunologic markers are used to diagnose human immunodeficiency virus (HIV) infection?

Answer 162

**Testing for HIV-specific antigens and antibodies** is important in the diagnosis of HIV infection, including antibodies to viral antigens p24, p31, gp41, and gp120/ 160.

Question 163

Why are vaccines for influenza not always effective?

Answer 163

Influenza viruses mutate often as a result of replication errors. These mutations cause **antigenic drift**, ensuring antigenic variability of strains each year. Recombination events of the influenza A genome result in a major antigenic change called antigenic shift. Health care agencies predict the most likely strains that will predominate in the next season. Trivalent influenza vaccines are available prior to the start of the influenza season. Although this process is extremely successful, occasionally an unexpected strain will predominate, and the vaccine may not provide total coverage for that strain. Even with this known possibility, it is still advised that all persons be vaccinated because some protection is better than no protection at all.