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MedLabs - 5000 Bacteriology > Gram Positive Rods > Flashcards

Gram Positive Rods Flashcards

1
Q

Column1

A

Column2

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2
Q

Aerobic, gram-positive, sporeforming rod

A

General physical characteristics of Bacillus

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3
Q

B. anthracis habitat and epidemiology

A

Habitat - soil; rarely isolated in developed countries but may be prevalent in impovershied areas where vaccination of animals is not practiced
Transmission - contact with infected animals or animal products; inhalation of spores of their introduction through breaks in the skin or mucous membranes; occasionally acquired through ingestion
Clinical significance - anthrax

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4
Q

B. cereus habitat and epidemiology

A

habitat - ubiquitous in soil throughout the world
transmission - traumatic introduction into normally sterile sites; ingestion of contaminated food
Clinical significance - food poisoning; opportunistic pathogen

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5
Q

What are the three forms of Anthrax

A

Cutaneous, Pulmonary, and Gastrointestinal

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6
Q

Cutaneous Anthrax characteristics

A

Painless papule progresses to ulceration with surrounding vesicles; then to an eschar formation; painful lymphadenopathy, edema, and systemic signs may develop
•Estimated 2000 cases reported annually, worldwide
•Incubation period: 1 to 10 days
•Mortality rate in patients with untreated cutaneous anthrax: 20%

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7
Q

Pulmonary Anthrax characteristics

A

“wool-sorters disease”:
•Inhalation of spore; rapid onset of sepsis with fever, edema, and lymphadenopathy; meningeal symptoms in half the patients
•Incubation period: 2 to ? days
•Virtually all patients who develop disease progress to a fatal outcome (immediate medical intervention)
- associated with a prolonged latent period

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8
Q

Gastrointestinal Anthrax characteristics

A

Ingestion of spore; ulcers form at the site of invasion (e.g., mouth, esophagus, intestine) leading to regional lymphadenopathy, edema and sepsis
•Accounts for less than 1% of the total cases worldwide; never reported in the United States
•Mortality associated with gastrointestinal anthrax is believed to approach 100%

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9
Q

Virulence factors of B.anthracis

A

Polypeptide capsule, Edema toxin, Lethal toxin; and 3 factors

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10
Q

Polypeptide capsule of B.anthracis

A

consisting of poly-D-glutamic acid observed in clinical specimens
•Protects the organism against the bactericidal components of serum and phagocytes, and phagocytic engulfment
•Plays its most important role during the establishment of the infection, and a less significant role in the terminal phases of the disease, which are mediated by the anthrax toxin

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11
Q

toxins of B.anthracis

A

Virulent strains also produce exotoxins that combine to form edema toxin (combination of protective antigen and edema factor) and lethal toxin(protective antigen with lethal factor)

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12
Q

Factors (1-3) of B.anthracis

A

Factor I : edema factor (EF) which is necessary for the edema producing activity of the toxin
•Factor II: protective antigen (PA), because it induces protective antitoxic antibodies in guinea pigs. PA is the binding domain of the anthrax toxin which has two active (A) domains, EF (above) and LF (below)
•Factor III: lethal factor (LF) because it is essential for the lethal effects of the anthrax toxin

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13
Q

What are the differences between Reference and Sentinel labs

A

Reference - ODHL
Sentinel - clinical, hospital labs
(different levels of laboratories)

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14
Q

Virulence factors involved in food poisoning (B.cereus)

A 
emetic form (heat-stable) 
diarrheal form (heat-labile)
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15
Q

Emetic Form of B.cereus

A

Heat-stable, proteolysis-resistant enterotoxin causes the emetic form of the disease
Results from the consumption of contaminated rice.Most bacteria are killed during the initial cooking of the rice, but the heat-resistant spores survive. If the cooked rice is not refrigerated, the spores germinate, and the bacteria can multiply rapidly. The heat-stable enterotoxin that is released is not destroyed when the rice is reheated.
•Emetic form of disease is an intoxication, caused by ingestion of the enterotoxin and not the bacteria
Incubation period: 1 to 6 hours
Symptoms: vomiting, nausea, and abdominal cramps
Duration: 8 to 10 hours

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16
Q

Diarrheal form of B.cereus caused by (and its affects)

A

Heat-labileenterotoxin causes the diarrheal form of the disease.
•Similar tothe enterotoxins produced by Escherichia coli and Vibrio cholerae; each stimulates the adenylatecyclase-cyclic adenosine monophosphate system in intestinal epithelial cells, leading to profuse watery diarrhea

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17
Q

Diarrheal Form of B.cereus

A

True infection, resulting from ingestion of the bacteria in contaminated meat, vegetables, or sauces
•Longer incubation period, during which the organism multiplies in the patient’s intestinal tract, followed by the release of the heat-labile enterotoxin; greater than 6 hours
•Symptoms: diarrhea, nausea, and abdominal cramps
•Duration: ~ 1 day

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18
Q

Treatment of Bacillus diseases

A

Self-limiting gastroenteritis (B.cereus)

Antibiotics available for B. anthracis

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19
Q

Types of testing used to diagnose Bacillus species

A

Microscopy:Gram-positive or gram-variable (spores appear clear since they do not take up stain); many species are large, boxy, GPR
•Cultivation and biochemicals
•Molecular diagnostics
•Antimicrobial susceptibility

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20
Q

B. anthracis diagnosis

A

Sheep blood agar: nonhemolyticwith filamentous outgrowths (“Medusa-head”); have a consistency of beaten egg whites
•Nonmotile

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21
Q

B. cereus diagnosis

A

Sheep blood agar: large, flat, beta-hemolytic colonies
•Motile
•Food: 105cells per gram of food

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22
Q

General characteristics of Cornebacterium

A

Pleomorphic gram-positive rod (e.g., “club-shaped”; V and L formations; palisades)

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23
Q

C. dipththeriae habitat, and epidemiology

A

Habitat - inhabits human nasopharynx, but not part of normal flora; humans only known reservoir
Transmission - person to person by exposure to respiratory droplets or direct contact with lesions
Clinical Significance - (2 forms)
•Respiratory: pharyngitis characterized by the development of an exudative membrane (life-threatening because it covers the airway)
•Cutaneous: nonhealingulcers and membrane formation

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24
Q

Diphtheroids habitat, and epidemiology

A

Habitat - normal skin flora of humans and animals, fresh and salt water, soil and air worldwide
Transmission - endogenous
Clinical Significance - opportunistic pathogen in immunocompromisedpatients

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25
Q

Virulence factors of Corynebacterium

A

Diphtheria toxin, Exotoxin, Tox gene, A-B exotoxin

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26
Q

Diptheria toxin

A

major virulence factor of C. diphtheriae

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27
Q

Exotoxin of Diphtheria

A

Exotoxinis produced at the site of the infection and then disseminates through the blood to produce the systemic signs of diphtheria
•toxgene that codes for the exotoxin is introduced into strains of C. diphtheriaeby a lysogenic bacteriophage (β-phage)
•A-B exotoxin inhibits protein synthesis

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28
Q

Found worldwide, particularly in poor, crowded urban areas and the protective level of vaccine-induced immunity is low
•Largest outbreak in the latter part of the 20th century occurred in the former Soviet Union (1994 almost 48,000 cases were documented, with 1746 deaths)
•Maintained in the population by asymptomatic carriagein the oropharynx or on the skin of immune people (after either exposure to C. diphtheriaeor immunization)

A

Diphtheria

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29
Q

Diphtheria prevention

A

DPT vaccine: at ages 2 months, 4 months, 6 months, 15 to 18 months, and at 4 to 6 years
•Booster vaccinations with diphtheria toxoid combined with tetanus toxoid be given every 10 years

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30
Q

Types of Diphtheroids

A

Corynebacterium Jeikeium/urealyticum

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31
Q

Corynebacterium jeikeium

A

Types of Diphtheroids
- Risk factors: immunocompromised patient with hematologic disorders or intravascular catheters
•“Healthy people” carriage: uncommon; skin of ~40% of hospitalized patients can be colonized, regardless of their immune status
•Very resistant to antibiotics (antibiotic therapy during hospitalization may foster colonization)

32
Q

Corynebacterium urealyticum

A

Type of Diphtheroid
- Pathogen of the urinary tract
•Strong urease producer (makes the urine alkaline, leading to the formation of renal stones)
•Risk factors: immunosuppression, underlying genitourinary disorders, an antecedent urologic procedure, and previous antibiotic therapy

33
Q

Diphtheroid treatment

A

Antibiotics are available to treat infections associated with corynebacteria
•Antitoxin for diphtheria to neutralize any unbound toxin

34
Q

Diphtheroid Microscopy Diagnosis

A

•Irregular shaped bacteria have cell arrangements resembling Chinese letter (Vs, Ls, Y-formation) or palisades (rows of parallel cells)

35
Q

Diphtheroid Culture and Biochemical Diagnosis

A

Specialty media for C. diphtheriae

36
Q

Diphtheroid Toxin Examination / Diagnosis

A

All isolates of C. diphtheriaeshould be tested for the production ofexotoxin
•In vitro immunodiffusionassay (Elektest), a tissue culture neutralization assay using specific antitoxin
•Molecular assay

37
Q

Short, gram-positive rods
•Facultative anaerobes
•Intracellular pathogen

A

General characteristics of Listeria

38
Q

Listeria Habitat and Epidemiology

A

Habitat - Soil, vegetation, and water; may colonize the human gastrointestinal tract
Transmission - Consumption of contaminated food (Soft cheese, raw milk, turkey, raw vegetables [esp. cabbage], processed meats, ice cream) •Transplacentalspread from mother to neonate
Clinical Significance - Human disease in several well-defined populations: neonates, the elderly, pregnant women, and patients with defective cellular immunity
•Estimated 2500 infections occur annually in the United States

39
Q

Listeria Infections in pregnant woman

A

Most commonly seenin the third trimester
•Mother experiences flu-like illness with fever, headache, and myalgia; self-limited
•Spontaneous abortion and stillborn neonates (within 3 to 7 days)

40
Q

Listeria Infections in newborn

A

Fatality reaches 50% if the fetus is born alive

•Early onset (transplacental) and Late onset

41
Q

Early onset Listeria in newborn

A

acquired transplacentally

42
Q

Late onset Listeria in newborn

A

(acquired at or soon after birth) disease occurs 2 to 3 weeks after birth, in the form of meningitis or meningoencephalitis with septicemia

43
Q

Listeria Infections in the elderly

A

Fatality rate is high

•Most common manifestations are central nervous system infection (e.g., meningitis) and endocarditis

44
Q

Listeria Virulence Factors

A
  • Virulent strains produce internalins(cell attachment factors),haemolysins, and a motility protein
  • Organisms can survive within phagocytes and spread intracellularly
45
Q

Treatment of Listeria

A

Antibiotics available for treatment of Listeria infections

46
Q

Prevention of Listeria

A

Avoidance of high-risk foods for susceptible population

47
Q

Listeria Laboratory Diagnosis

A

Microscopy
•Culture and biochemicals: Cold enrichment
•Molecular assays
•Antimicrobial susceptibilities•
Epidemiologic investigations: Serotyping, Molecular assays

48
Q

Listeria Species of importance

A

L. monocytogenes

49
Q

Erysipelothrix Species of importance

A

E. rhusiopathiae

50
Q

Microaerophilic, Pleomorphic, gram-positive rod

A

General characteristics of Erysipelothrix

51
Q

Erysipelothrix Habitat and Epidemiology

A

Transmission - Primarily occupational (e.g., butchers, meat processors, farmers, poultry workers, fish handlers, and veterinarians)
•Cutaneous infections typically develop after the organism is inoculated subcutaneously through an abrasion or puncture wound during the handling of contaminated animal products or soil (ZOONOSIS)
Clinical Significance - erysipeloid infection and septicemic form of infection

52
Q

What are the differences between the primary forms of Erysipelothrix infection

A
  • erysipeloid (localized skin infection); inflammatory skin lesion that develops at the site of trauma after 2 to 7 days of incubation
  • septicemic –> Endocarditis may have an acute onset but is usually subacute; involvement of previously undamaged heart valves (particularly the aortic valve) is common
53
Q

Erysipelothrix Diagnossi

A

Microscopy
Culture and biochemicals
Antimicrobial susceptibilities

54
Q

Gardenerella Habitat and Epidemiology

A

Habitat - Member of the vaginal flora of up to 69% of women at reproductive age
Transmission - Endogenous
Clinical significance - Bacterial vaginosis, UTI

55
Q

Pleomorphic, gram-positive rod or coccobacillusthat often stains gram-variable

A

Gardenerella general characteristics

56
Q

important species of Gardnerella

A

G. vaginalis

57
Q

Complications of Gardnerella

A

Having bacterial vaginosis increases the risk of acquiring STDs; may complicate pregnancy

58
Q

Gardenerella Laboratory Diagnosis

A

Microscopy - Observation of “clue” cells
Culture and biochemicals
DNA probe assay (BD Affirm)
OSOM BVBlue test

59
Q

Gardenerella treatment

A

Antibiotics are recommended for women with symptoms

•Routine treatment of sex partners not needed

60
Q

Cells elongate to form branching filamentous forms
•Some genera are partially acid-fast: Resist to decolorizationwith weak acid solutions, Based on the presence of mycolicacids (long chain fatty acids) in the cell wall

A

General Characteristics of Aerobic Actinomycetes

61
Q

Aerobic Actinomycetes Acid-fast stain (process)

A

Smear is flooded with carbolfuchsinfor several minutes
•Slide is rinsed and then decolorized with acid alcohol (modified stain uses a weak acid)•Counterstain with methylene blue
•If mycolicacids are present in the cell wall, they retain the dye and appear reddish-purple in a positive stain

62
Q

Strict aerobic rods, Weakly acid-fast, Aerial hyphae

A

Nocardia General characteristics

63
Q

Nocardia Habitat and epidemiology

A

Habitat - Inhabitants of soil and water, primarily responsible for decomposition of plant material
Transmission - traumatic inoculation or inhalation
Clinical significance - Cutaneous, pulmonary and disseminations (chronic in immunocompromised)

64
Q

Nocardia Laboratory Diagnosis

A

Microscopy : weakly acid fast
Culture and biochemicals
Molecular assays

65
Q

Other Aerobic Actinomycetes

A

Streptomyces, Gordonia, Tsukameralla, Rhodococcus

pathogens of immunocompromised

66
Q

Nodocardia Treatment

A

Clinical isolates of Nocardiasppare variably resistant to antibiotics
•Empiric coverage with two or three agents in patients with severe infection
•Cutaneous infection in an immunocompetenthost with monotherapy

67
Q

Patients who are immunocompromised and pregnant women should avoid eating soft cheeses such as Mexican-style, feta, brie, Camembert, and blue-veined cheese to prevent:

A

foodborne listeriosis

68
Q

A Corynebacterium species recovered from a throat culture is considered a pathogen when it produces:

A

An exotoxin

69
Q

A gram-positive branching filamentous organism recovered from a sputum specimen was found to be positive with a modified acid-fast stain method. What is the most likely presumptive identification?

A

Nocardia spp

70
Q

What is the name of the group of bacteria that are slightly curved, gram-positive rods often referred to as club-shaped or Chinese letters when viewed in a Gram stain?

A

Corynebacterium

71
Q

What is the major virulence factor associated with Corynebacterium diphtheriae?

A

Diphtheria toxin

72
Q

What Corynebacterium infects mostly immunocompromised patients?

A

NOT ulcerans

73
Q

What organism is responsible for spontaneous abortion and stillborn neonates and can cause meningitis with a fatality rate approaching 50% in newborns?

A

Listeria monocytogenes

74
Q

Erysipelothrix rhusiopathiae produces all the following diseases EXCEPT:

A

Meningitis

Bacteremia
Endocarditis
Erysipeloid

75
Q

The three proteins that make up the anthrax toxin include all the following EXCEPT:

A

Protective antigen
Edema factor
Cellular factor
Lethal factor

76
Q

What Bacillus sp. is a relatively common cause of food poisoning and opportunistic infection in susceptible hosts?

A

Bacillus cereus

MedLabs - 5000 Bacteriology (27 decks)

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