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MDL 252 Microbiology 2 > Unit 3 Exam Review > Flashcards

Unit 3 Exam Review Flashcards

1
Q

Organism that obtain food and shelter by living on or withing another organism

A

Parasite

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2
Q

Parasite that can live only in a host

A

Obligate

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3
Q

Parasite that can live both in or on a host, as well as free form

A

Facultative

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4
Q

Parasites that live inside the body

A

Endoparasites

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5
Q

Parasites that exist on the body surface

A

Ectoparasites

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6
Q

Parasites that cause harm to the host

A

Pathogenic

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7
Q

Parasites that benefit from the host, without causing harm

A

Commensals

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8
Q

Organism that harbors the parasite and suffers a loss

A

Host

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9
Q

A host that the parasite lives its adult and sexual stage

A

Definitive host

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10
Q

A host that the parasite lives as the larval and asexual stage

A

Intermediate host

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11
Q

Hosts that harbor the parasite to ensure continuity of the parasite’s life cycly

A

Reservoir host

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12
Q

Organism that is responsible for transmitting the parasitic infection

A

Vector

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13
Q

Specimens that parasites may be recovered from

A

Peripheral blood, CSF, GI tract, liver, lung, muscle, urine, ulcers, eyes

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14
Q

What is the most common specimen parasites are found in?

A

Feces, fresh or preserved

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15
Q

Feces must be free of what substances?

A

barium and antibiotics

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16
Q

What 3 steps are in an O&P exam?

A

Wet mount, concentration, permanent smear

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17
Q

What is a direct wet mount

A

detects motile organisms in duodenal drainage, with saline or iodine

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18
Q

What chemicals can be used to concentration a specimen?

A

Formalin, ethyl acetate sedimentaiton or zinc flotation method, with saline or iodine

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19
Q

What are the permanent stained smears

A

Trichrome or Iron hemotoxylin

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20
Q

What is the Scotch tape prep for?

A

Diagnosis of Pinworm infection (eggs) from anus

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21
Q

What specimen is needed for Trichomonas vaginalis or microfilaria

A

Urine

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22
Q

Thick and thin blood films are used for what parasites?

A

Plasmodium, Babesia and Trypanosomes

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23
Q

What percent of the population world wide harbors E. histolytica

A

0.5 to 50%

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24
Q

Where are the higher rates of infectionn of E. histolytica?

A

underdeveloped countries

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25
Q

What percent of the USA population are infected with histolytica?

A

1 to 3$

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26
Q

What is associated with the infection of E. histolytica?

A

poor hygiene

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27
Q

Who is the principal host of E. histolytica?

A

Humans

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28
Q

How does E. histolytica infection occur?

A

Ingestion of cysts on fecally contaminated food or hands.

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29
Q

What is the E. histolyticac cyst resistant to?

A

The gastric environment

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30
Q

Where does E. histolytica decyst?

A

Small intestine

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31
Q

What is E. histolytica called when it decysts?

A

Metacyst

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32
Q

What does an E. histolytica metacyst divide into?

A

Divides into 4 and then 8 amoebae

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33
Q

Where do the E. histolytica amoebae move to?

A

Large intestine

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34
Q

How do a majority of E. histolytica leave the body?

A

Through feces

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35
Q

With a large E. histolytica infection, what happens to amebae that doesn’t leave the body?

A

The amebae attach to and invade the mucosal tissue

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36
Q

What do E. histolytica amebae form?

A

Flask shaped lesions also called bomb craters

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37
Q

What can E. histolytica bomb craters lead to?

A

liver abscess

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38
Q

What is used to treat asymptomatic E. histolytica infections?

A

Iodoquinol

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39
Q

What is used to treat symptomatic and chronic E. histolytica amebiasis?

A

Metronidazole

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40
Q

How is E. histolytica usually diagnosed?

A

O&P Exam

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41
Q

What does En. Histolytica cause

A

Major cause of amebic dysentery

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42
Q

Describe the troph form of E. histolytica

A

Ameboid appearance, 15 to 20 micrometers in diameter. Single nucleus with small central karyosome.

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43
Q

What types of E. histolytica strains are larger than normal?

A

More invasive strains

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44
Q

What does the E. histolytica endoplasm look like?

A

Finely granular

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45
Q

What may the E. histolytica endoplasm contain?

A

Ingested erythrocytes

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46
Q

How is the nuclear chromatin distributed along the periphery of the nucleus?

A

Evenly distributed

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47
Q

What is diagnostic of E. histolytica?

A

Ingested RBC

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48
Q

Describe the Cyst form of E. histylotica

A

Spherical, with a refractle wall

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49
Q

In an E. histolytica cyst what does the cytoplasm contain?

A

Dark staining chromatoidal bodies

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50
Q

What does the nucleus of E. histolytica look like in cyst form?

A

1 to 4 nuclei with a central karyosome with peripheral chromatin

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51
Q

What are flagella?

A

Thin cytoplasmic extensions

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52
Q

What do flagellates contain?

A

locomotor organelles

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53
Q

What is the most frequent protozoan intestional disease in the US?

A

Giardia lamblia

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54
Q

How is G. lamblia transmitted?

A

water borne disease is most common, drinking from contaminated streams, travel to endemic areas, and day care centers. Also transmitted person to person

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55
Q

How does G. lamblia infection occur?

A

Ingestion of cysts, usually in contaminated water

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56
Q

Where does the Decystation of G. lamblia occur?

A

Duodenum

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57
Q

Where is the duodenum

A

First section of the small intesting

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58
Q

Where do G. limblia trophs colonize?

A

The upper small intestine where they may swim freely or attach to the sub-mucosal epithelium via the ventral suction disc.

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59
Q

What do free trophs do as they move down stream?

A

encyst

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60
Q

What takes place during encystment of G. lamblia?

A

Mistosis

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61
Q

How are G. lamblia cysts passed?

A

In stool

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62
Q

What are the G. lamblia reservoirs?

A

Man is primary, although beavers, pigs and monkeys are also infected

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63
Q

Describe G. lamblia cysts

A

9 to 12 m. eppisodial cells with a smooth defined wall

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64
Q

Describe G. lamblia cytoplasm

A

Four nuclei and mana structures are seen in the troph.

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65
Q

Describe G. lamblia troph

A

12 to 15 m, half pear shaped organism with 8 flagella and 2 axostyles

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66
Q

How are G. lamblia axostyles arranged?

A

bilateral symmetry

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67
Q

What does the G. lamblia troph cytoplasm contain?

A

Two nuclei and two parabasal bodi

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68
Q

What are early symptoms of G. lamblia?

A

flatulence, abdominal distension, nausea and foul-smelling bulky, explosive, often watery diarrhea.

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69
Q

What does G. lamblia stool contain?

A

Excessive lipids but very rarely any blood or necrotic tissue

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70
Q

What is a more chronic stage of G. lamblia associated with?

A

Vitamin B12 malabsorption and lactose intolerance

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71
Q

How is G. lamblia diagnosed?

A

O&P, ELISA, FA, or IFA stain

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72
Q

What is the drug of choice for G. lamblia?

A

Metronidazole

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73
Q

Cryptosporidium infects humans when they ingest __________.

A

Oocysts containing many sporozoites

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74
Q

What parasite is found in the GI tract of many animals and causes epidemics of diarrhea in humans

A

Cryptosporidium

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75
Q

Cryptosporidium contaminates what necessities

A

Food and water

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76
Q

Cryptosporidium is the likely cause when a community has _______

A

diarrhea

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77
Q

Severity of diarrhea and duration of Cryptosporidium symptoms are related to _______

A

Immuno-competence

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78
Q

In what types of patients will Cryptosporidium cause prolonged, severe diarrhea

A

AIDS patients

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79
Q

In AIDS patients the organisms may invade what areas of the body?

A

Gallbladded, biliary tract and lung epithelium

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80
Q

What is the treatment for cryptosporidias?

A

No approved effective treatment

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81
Q

What are the detection tests for Cryptosporidium??

A

Antibody tests, PCR, DFA

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82
Q

What is PCR?

A

Polymerase chain reaction

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83
Q

What is a sensitive method for detection of cryptosporidium?

A

FA/DFA

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84
Q

What are the two “areas” of Trypanosoma outbreaks?

A

African and American

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85
Q

What does African Trypanosoma cause?

A

African sleeping sickness

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86
Q

What is the vector for African Trypanosoma?

A

Tsetse fly

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87
Q

Trypanosoma invades which organs?

A

All organs including heart and CNS

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88
Q

What does African sleeping sickness lead to?

A

apathy, mental dullness, tremors, convulsions, sleepiness, coma

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89
Q

What are long term effects of African sleeping sickness?

A

Weith loss and death from malnutrition, heart failure, pneumonia or parasitic infection

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90
Q

What does American Trypanosoma cause?

A

Chagas disease

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91
Q

What is the vector for American Trypanosoma?

A

Reduvid bug or kissing bug

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92
Q

What is Chagas disease?

A

Chronic or acute infection characterized by neurological disorders

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93
Q

What neurological disorders are caused by Chagas disease?

A

Dementia, megacolon, megaesophagus and damage to the heart muscle

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94
Q

Is chagas disease fatal?

A

Yes unless its treated

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95
Q

What is responsible for human malaria?

A

Five Plasmodium species

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96
Q

What is the estimated amount of malaria cases?

A

200 million global cases

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97
Q

What is the mortality rate of malaria?

A

1 million people per year

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98
Q

What are the 2 most common species of malarial parasite?

A

P. falciparum and P. malariae

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99
Q

Where are malarial parasites most often found?

A

Asia and Africa

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100
Q

What species of malaria parasite is found in Latin America, India and Pakistan?

A

P. vivax

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101
Q

Where is P. ovale almost exclusively found?

A

Africa

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102
Q

How is the malaria parasite transmitted?

A

Female anopheline mosquito

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103
Q

How does the female anopheline mosquito transmit malaria parasites?

A

Injects sporozoites in the saliva.

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104
Q

What are alternate methods that malaria can be transmitted?

A

Transfusion and transplacentally

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105
Q

What symptoms will a patient with malaria develop?

A

headache, lassitude, vague pains in bones, and joints, chilly sensations and fever

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106
Q

What is a malaria fever associated with?

A

Severe headache, nausea, vomitin, and convulsions

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107
Q

What type of pattern do a malaria chill and fever follow?

A

Cyclic (paroxysm)

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108
Q

What type of malaria results in death?

A

P. falciparum which is more severe

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109
Q

Splenomegaly, hepatomegaly and nephritic syndromes are results from what disease?

A

Chronic malaria

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110
Q

How is Plasmodium diagnosed?

A

Detection of parasite in Giemsa stained blood smears

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111
Q

How is P. malariae treatment effective?

A

Various quinine derivatives and eradication of mosquitoes

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112
Q

Describe roundworms

A

Elongate and cylindric with a well developed digestive tract

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113
Q

How are roundworms diagnosed?

A

Eggs in feces

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114
Q

What type of infections are associated with Ascaris lumbricoides?

A

asymptomatic

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115
Q

How is A. lumbricoides infected?

A

Ingesting food or soil contaminated with infected eggs

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116
Q

Where do A. lumbricoides eggs hatch?

A

Upper small intestine

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117
Q

How long do A. lumbricoides female larvae life for?

A

12 to 18 months

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118
Q

How many eggs do female larvae produce?

A

25 million at a average daily output of 200,000 for life cycle

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119
Q

A. lumbricoides eggs are resistant to _____

A

Chemical disinfectant

120
Q

How long can A. lumbricoides live for in sewage

A

survives for months

121
Q

What type of infection is A. lumbricoides?

A

Man to man

122
Q

How is A. lumbricoides diagnosed?

A

Eggs in stool

123
Q

What is Enterobius vermicularis known as?

124
Q

What is the most common helminthic infection?

A

Pinworm or E. vermicularis

125
Q

What type of disease is pinworm?

A

Urban disease of children in a crowded environment (schools, day cares)

126
Q

What is the most common symptom of pinworm?

A

Perianal, perineal and vaginal itching and irritation

127
Q

How is pinworm diagnosed?

A

Finding the adult worm or eggs in the perianal area, particularly at night

128
Q

How are pinworm eggs obtained?

A

scotch tape or pinworm paddle

129
Q

What is the treatment for pinworm?

A

Two doeses of Pyrental Pamate two weeks apart.

130
Q

What is an alternative treatement for pinworm?

A

Mebendazone

131
Q

Who should be treated for pinworm?

A

The whole family, ,to avoide reinfection

132
Q

What must be santized between pinworm treatments?

A

Bedding and underclothing

133
Q

Trichuris trichuria causes what tropical disease?

134
Q

What age group does whipworm effect?

A

5 to 15 years

135
Q

Where is whipworm found?

A

Rural Asia and Africa, can also be seen in the Americas mostly south

136
Q

How do you get infected with whipworm?

A

Ingestion of embryonated eggs in soil

137
Q

How are heavy infections of T. trichuria characterized by?

A

Chronic profuse mucus and bloody diarrhea, associated with abdominal pains and prolapsed rectum

138
Q

What does a T. trichuria infection result in?

A

Malnutrition, weight loss, and sometimes death

139
Q

How is T. trichuria diagnosed?

A

Eggs in feces

140
Q

What is the treatment for T. trichuria?

A

Abendazole

141
Q

What is the most effective way to control T. trichuria?

A

Improved hygiene and sanitary eating habits

142
Q

D. latum is also known as _______?

A

Fish tapeworm

143
Q

What is D. latum associated with?

A

Eating raw or improperly cooked freshwater fish

144
Q

How long can tapeworms get?

A

3-10 meters with more than 3000 proglottids

145
Q

How are humans infected?

A

Eating uncooked fish that contains larvae

146
Q

How long does it take for a tapeworm to mature?

A

3 to 5 weeks

147
Q

What are symptoms of tapeworms?

A

abdominal discomfort, weight loss, loss of appetite and malenutrition

148
Q

What are additional symptoms in heavily infected adults?

A

Anemia, neurological problems, vitamin B12 deficiency

149
Q

How are tapeworms diagnosed?

A

Finding many typical eggs and empty proglottids in feces

150
Q

What can help a tapeworm diagnosis?

A

History of raw fish consumption and residence in an endemic locality

151
Q

What is the drug of choice for D. latum?

A

Praziquantel

152
Q

How can D. latum be prevented?

A

Freezing for 24 hours, thorough cooking or pickling of fish will kill larvae

153
Q

What species of Taenia is prevalent in cows?

A

T. saginata

154
Q

What species of taenia is prevalent in pigs?

155
Q

What is the infection rate of Taenia?

A

As low as 1 per 1000 in North America and as high as 10% in third world

156
Q

What tapeworm shows a higher infection?

157
Q

How are tapeworms ingested?

A

A tapeworm larval cyst is ingested with poorly cooked infected meat

158
Q

What are the symptoms of a light Taenia infection?

A

Asymptomatic

159
Q

What are the symptoms of a heavy Taenia infection?

A

Abdominal discomfort, epigastric pain, vomiting and diarrhea

160
Q

What type of Taenia eggs can infect humans?

161
Q

T. solium eggs can cause what disease in humans?

A

Cysticercosis

162
Q

What is cysticercosis

A

Larval cysts in lung, liver, eye and brain

163
Q

Cysticercosis can cause blindness and _____?

A

neurological disorders

164
Q

Antibodies are produced in cysticercosis and are useful in _______?

A

Epidemiological tools

165
Q

How is Taenia diagnosed?

A

Based upon recovery of eggs or proglottids in stool or perianal area

166
Q

How is a cysticercosis infection confirmed?

A

Antibodies

167
Q

What is the drug of choice for Taenia?

A

Praziquantel

168
Q

What are effective precautions against Taenia?

A

Thorough inspection of beef and pork, adequate cooking or freezing

169
Q

What temperatures can cysticerci not survive?

A

below 10C and above 50C

170
Q

What is the best stain for Giardia lamblia?

A

Trichrome or Iron hemotoxylin

171
Q

What is the best stain for Entamoeba histolytica?

172
Q

What is the best stain for Trichuris trichuria?

A

Iodine wet mount

173
Q

What is the best stain for Trypanasoma cruzi?

A

Blood smear

174
Q

What is the best stain for Cryptosporidium parvae?

A

Modified acid fast staine

175
Q

What is the best stain for Ascaris lumbricoides?

A

Iodine wet mount

176
Q

What is the best stain for D. latum?

A

Iodine wet mount

177
Q

What is the primary stain and function for Kinyoun?

A

Carbolfuchsin stains the mycobacteria bacilli

178
Q

What is the Kinyoun counterstain and function?

A

Methylene blue stains background and other bacteria, not acid fast

179
Q

What is present in the cell wall that contributes to acid fastness?

A

Mycolic acids

180
Q

How will mycobacteria appear on a gram stain?

A

Poorly stained, beaded gram pos bacilli, gram neutral or ghosts

181
Q

Which stain is more sensitive Kinyoun or Flurorchrome?

A

Fluorochrome

182
Q

Why is the quantitation of the AFB important?

A

Indicates the extent of the patient’s infectiousness

183
Q

How many oil fields should be observed before calling a smear negative?

A

300 oil fields

184
Q

What factors may contribute to a false positive smear?

A

Cross-contamination of slides, using tap water in staining, not wiping oil immersion between slides

185
Q

What must be done to prepare a sputum or fluid specimens for AFB staining?

A

Decontamination, concentration by centrifugation, heatfixing

186
Q

Name 2 stool fixatives that are appropriate if infections with Ascaris or Hookworm are suspected.

A

Formalin, SAF, MIF

187
Q

What is the proper specimen and staining method for Plasmodium falciparum?

A

Blood, Giemsa/Wright stain

188
Q

What is the proper specimen and staining method for Cryptosporidium parvae

A

Feces, MAF/IFA

189
Q

What is the proper specimen and staining method for Giardia lamblia

A

Feces, Trichrome/wet pretp?IFA

190
Q

What is the proper specimen and staining method for Trichomas vaginalis

A

Urine, genital, wet prep/Giemsa

191
Q

What is the proper specimen and staining method for Trypanasoma cruzi?

A

Blood, Giemsa/Wright stain

192
Q

Name 3 substances in a fecal specimen that may interfere with the detection of intestinal protozoa

A

Barium, mediations, mineral oil, bismuth

193
Q

Which magnification is appropriate to examine stools that have been stained with trichrome?

A

Oil immersion 1000x

194
Q

How will the background look on trichrome?

195
Q

How does cytoplasm look on trichrome?

A

trophs are blue green, cysts are blue green to purple

196
Q

How does nuclei look with trichrome?

A

red, sometimes tinged with purple

197
Q

How do cellular inclusions look with trichrome?

A

red, sometimes tinged with purple

198
Q

What is the proper microscopic examination procedure for stools that have been concentrated by formalin ethyl-acetate?

A

Examine the sediment at low power (x100) and high power with saline and iodine

199
Q

What is the purpose of Formalin in the concentration?

A

Formalin will preserve the parasite and render it non-infectious

200
Q

What is the purpose of ethyl acetate in the concentration?

A

Ethyl acetate will trap debris and separate it from potential parasites contained in the sediment.

201
Q

Why should stool specimens be preserved and concentrated?

A

Allows for the recovery of protozoa, helminths, coccidian, microspordia

202
Q

If pinworm infection is suspeced, what type of specimen should be collected?

A

Scotch tape prep of perianal or perineum

203
Q

Why is it necessary to do thick blood films for parasites?

A

allows exam of a larger volume of blood for parasites

204
Q

Why is it necessary to do thin blood films for parasites?

A

used for parasite identification

205
Q

Why is a calibrated microscope necessary for observation of parasitology slides?

A

Size is an important characteristic for ID of parasites

206
Q

What are the 6 steps in viral replication?

A

Attachment, penetration, uncoating synthesis, maturation, release

207
Q

How does Herpes infection occur?

A

Break in the mucus membranes of the mouth or throat, via the eye or genitals or directly via minor abrasions in the skin.

208
Q

When are most individuals infected with HSV? And why?

A

By 1-2 years of age due to the universal distribution of the virus

209
Q

Describe the initial symptoms of HSV infection.

A

Initially asymptomatic, however there may be minor local vesicular lesions

210
Q

What are the stages of HSV infection?

A

Local multiplication, viremia, systemic infection, followed by life-long latent infection with periodic reactivation

211
Q

Where can you find lesions of HSV1?

A

Oral and ocular lesions, increasing in genital lesions

212
Q

Where can you find lesions of HSV2?

A

Genital and anal lesions

213
Q

Is there a vaccine for HSV?

A

Not currently licensed but a number are under development.

214
Q

Is HSV a DNA or RNA virus?

215
Q

When does VZV normally occur?

A

Chicken pox - 90% in children, Shingles in the elderly

216
Q

How does chicken pox infect humans?

A

Via respiratory tract or conjunctiva

217
Q

How does the chicken pox spread?

A

After inoculation the virus spreads to bloodstream and reticuloendothelial system

218
Q

Are there complications to chicken pox?

A

Complications are rare but may include CNS infection

219
Q

How does Shingles infect humans?

A

Virus persists in CNS, either latently or a persistent infection. Reactivation leads to infection and tissue damage

220
Q

What can Shingles lead to?

A

Blindness when cranial nerves are involved

221
Q

What is the therapy for Shingles?

222
Q

What is the largest of the Herpes viruses?

A

Cytomegalovirus (CMV)

223
Q

How common is CMV infection?

A

50-80% of US population are infected by age 40

224
Q

What type of infection is CMV?

A

asymptomatic

225
Q

What is the most common transmission of CMV?

A

During pregnancy to infants exposed in utero

226
Q

What types of people are infected with CMV?

A

Immune deficient, specifically T-cell ex. AIDS and immunosuppressed transplant patients

227
Q

How is CMV transmitted?

A

oral/respiratory route

228
Q

Describe the systemic infection of CMV

A

Produces enlargement of cells and nuclear inclusion bodies in a wide range of tissues

229
Q

What is RSV the cause of?

A

Respiratory infections in infants and children

230
Q

What are some infections RSV causes?

A

Pneumonias, croup, upper respiratory

231
Q

How is RSV transmitted?

A

Person to person, possibly nosocomial

232
Q

When is RSV transmitted?

A

Usually in winter

233
Q

What types of standard tests are avaliable for RSV?

A

cell culture, molecular (PCR or DNA) antibody detection

234
Q

What special types of tests are avaliable for RSV?

A

Fluorescent antibody, enzyme immunoassay (EIA)

235
Q

What are the 3 types of influenza?

A

Type A, B, and C

236
Q

Name 3 types of Influenza A?

A

H1N1, H1N2, and H3N2 viruses

237
Q

What is a host for Infuenza A?

A

Wild birds, however they do not become sick when infected. Domestic poultry (turkeys and chickens) can die from avian infuenza.

238
Q

Who has recently become a factor in the spread of influenza?

239
Q

Where is Influenza B normally found?

240
Q

What can Influenze B cause?

A

Morbidity and mortality. Less sever epidemics than Type A. Type B can cause human epidemics, bout not pandemics

241
Q

What type of disease does Infuenze C cause?

A

Mild illness which doesn’t cause epidemics or pandemics

242
Q

How can Influenza be prevented?

A

Vaccination

243
Q

What is the death rate for Mycobacteria and who is subjected to it?

A

3 million people worldwide, normally over 50 years old or immune compromised/surpressed

244
Q

How is mycobacteria transmitted?

A

Person to Person, or from contaminated fomites

245
Q

How is M. tuberculosis spread?

A

P2P by inhalation of droplets (cough, sneeze) More prevalent in contained populations

246
Q

How can tuberculosis spread in a lab?

247
Q

What type of organism is tuberculosis?

A

Obligate, grows under reduced O2, survives for weeks in tutrifying or dried sputum

248
Q

Name points of entry for tuberculosis.

A

Inhalation, food ingestion, milk born infections, puncture wounds, kidney involvement

249
Q

Describe tuberculosis immune response

A

Cell mediated several weeks post infection, followed by tubercle development in lungs

250
Q

What is the most common test for tuberculosis?

A

PPD purified protein derivative

251
Q

Testing method for PPD

A

Inoculate PPD on skin and examine after 48 hours

252
Q

Test results for PPD

A

> 5mm indicates prior exposure

253
Q

What are the PPD testing limitations?

A

Can’t differentiate past exposure from active infection

254
Q

Is there a vaccine for tuberculosis?

A

Yes but not administered in the US

255
Q

Where is the tuberculosis vaccine used?

A

developing countries with high prevalence of disease

256
Q

Why is the tuberculosis not used in US?

A

can’t circumvent disease reactivation, doesn’t prevent infection, may complicate current test methods, only 80% effective

257
Q

Where is NTM (non tuberculosis mycobacteria) found?

A

soil, marshes, rivers, municipal ester supplies, marine and terrestrial life forms

258
Q

How does NTM infect humans?

A

break in skin, trauma injections or surgery, animal contact

259
Q

How many Runyon schemes are there?

260
Q

What is Runyon scheme 1?

A

Photochromogens

261
Q

What does Scheme 1 (Photochromogens) require?

A

Light for pigment production

262
Q

What is Runyon scheme 2?

A

Scotochromogens

263
Q

What does Scheme 2 (Schotochromogens) require?

A

form pigments in the presence or absence of light

264
Q

What is Runyon scheme 3?

A

Nonphotochromogens

265
Q

What does Scheme 3 (Nonphotochromogens) require?

A

no pigments produced

266
Q

What is Runyon scheme 4?

A

Rapid Growers

267
Q

What is unique about scheme 4?

A

growth in 3-5 days at 25 or 37 degrees

268
Q

When is the best time to collect sputum samples?

A

Early morning from deep cough. Collect for 3 days

269
Q

What chemicals can be used to decontaminate sputum samples?

A

Sodium hydroxide, benzalkonium chloride

270
Q

What needs to be done to sputum samples to release mycobacteria from cells?

271
Q

Can mycobacteria be gram stained?

A

Does not gram stain well due to the high lipid content (mycolic or fatty acids)

272
Q

What type of organism is mycobacteria?

A

pleomorphic rod

273
Q

What do AFB gram stain as?

A

Gram invisible, negatively stained ghosts or as beaded gram pos rods

274
Q

What is a flurochrome stain?

A

sensitive, useful for screening numerous specimens fast

275
Q

What does a positive flurochrome look like?

A

bacilli will fluoresce yellow green

276
Q

What is the minimum amount of fields that should be examined?

A

30 low power fields

277
Q

How should flurochrome results be confirmed?

A

Two fuchsin acid fast stains

278
Q

Name 2 acid fast stains

A

Ziehl Neelsen Hot or Kinyoun Cold

279
Q

What do ZN and Kinyoun have in common?

A

Both employ carbol fuschin stain, destain with alcohol, counterstain methylene blue

280
Q

Why are mycobacteria termed acid fast organisms

A

lipid rich walls are resistant to destaining with heated acid alcohol

281
Q

What color does mycobacteria stain?

A

Red from the carbol fuschin, background appears blue/grean from the methylene blue counterstain

282
Q

Name mycobacteria complex media

A

Lowenstein-Jensen and middlebrook

283
Q

What does the Lowenstein-Jensen media contain?

A

potato, eggs, glycerol, citrate

284
Q

Why do many labs use solid and liquid media for mycobacteria?

A

Maximum recovery

285
Q

What is mycobacteria presumptive ID based upon?

A

growth rate, pigmentation, colonial appearance, optimal temperature

286
Q

What test/smear can be used to confirm presence of mycobacteria?

287
Q

What are new ID strategies for M. tb complex and M. avium

A

Nucleic acid probes; tests performed from solid or liquid media, results within hours

288
Q

What additional test methods are being developed for mycobacteria?

A

PCR - Polymerase chain reaction

289
Q

What type of tests can be run to detect M. tuberculosis directly from clinical specimens?

A

Automated detection systems

290
Q

What is the habitat of Nocardia?

A

Soil and water

291
Q

What is the gram stain of Nocardia?

A

Aerobic, branching gram positive rods that may have a beaded appearance

292
Q

How does Nocardia stain?

A

May stain as partially acid fast using a modified acid fast stain; not all isolates are partially acid fast

293
Q

What type of infections does Nocardia cause?

A

Skin and respiratory infections

294
Q

What are the Nocardia growth requirements?

A

30-35C in 48-72 hours

295
Q

What types of agar will Nocardia grow on?

A

sheep bllod, chocolate, or fungal like Sab dex; may need selective agars for contaminated speicmens

296
Q

How do colonies of Nocardia appear?

A

wrinkled, chalky white-orange pigment

MDL 252 Microbiology 2 (7 decks)

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