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MLT Microbiology > Unit 4 > Flashcards

Unit 4 Flashcards

1
Q

Biochemical tests are based on the _______ of the microorganisms

A

Phenotype

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2
Q

Nucleic acid assays are based on the ______ of the organism and are believed to be more accurate

A

Genotype

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3
Q

The initial screening of gram-negative rods is done by testing for the use of this carbohydrate

A

Lactose

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4
Q

Other sugars used to differentiate bacteria include all of the following except

A

Sucralose

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5
Q

Bacteria can use carbohydrates by

A

Oxidation

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6
Q

Some bacteria are asaccharolytic. This means that these bacteria

A

Do not utilize any carbohydrate; instead they use other organic molecules for energy

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7
Q

During this process, glucose enters the glycolysis pathway, resulting in the formation of pyruvic acid, which is further oxidized to other acids. What is this process called?

A

Fermentation

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8
Q

Oxidative/fermentative (O/F) basal medium is a medium that will test the oxidative and fermentative capabilities of a microbe. The pH indicator is ______

A

Bromothymol blue

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9
Q

When performing the O/F test, one tube is covered with mineral oil and one tube is left uncovered. Why is one tube covered with mineral oil?

A

To create an anaerobic (fermentative) environment

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10
Q

A technician is reading the biochemical tests for identifying a particular gram-negative rod. The organism has produced acid, indicated by a color change, in the closed tube only. This indicates that the organism is

A

A fermenter

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11
Q

What are the sugars present in Triple sugar ion (TSI)?

A

Sucrose, glucose, and lactose

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12
Q

What chemicals are added to TSI to detect the production of hydrogen sulfide gas?

A

Ferrous sulfate and sodium thiosulfate

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13
Q

To inoculate TSI agar or Kilgore iron agar (KIA), the Laboratory scientist should pick a well-isolated colony with an inoculating needle and

A

Stab the butt almost all the way to the bottom of the tube, then move the needle back and forth over the surface of the slant all the way to the top of the tube

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14
Q

These bacteria are unable to ferment either lactose or glucose, but the can degrade the peptones present in the TSI agar or KIA aerobically, resulting in the production of alkaline by-products in the slant or deep, respectively, changing the indicator to a deep red color. What kind of bacteria cannot ferment lactose or glucose?

A

Nonfermenting bacilli

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15
Q

If an organism fermented glucose only and utilized peptones, what would the TSI reaction be?

A

Alkaline/acid

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16
Q

If bacterium utilizes lactose of sucrose, what will the TSI reaction look like?

A

Acid/acid

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17
Q

If a bacterium utlilizes lactose or sucrose and produces H2S, what will the TSI reaction look like?

A

Acid/acid, black butt

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18
Q

The test determines if an organism is a delayed lactose fermenter

A

O-nitrophenyl-B-D-galactopyranoside (ONPG) test

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19
Q

The chemical reaction for the ONPG test is

A

B-galactosidase hydrolyzes ONPG into galactose and o-nitrophenol ( yellow compound)

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20
Q

The methyl red test detects metabolic by products from what pathway/

A

Mixed acid fermentation pathway

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21
Q

The biochemical pathway that the methyl red test confirms is

A

Glucose —> pyruvic acid —>mixed acid fermentation

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22
Q

The two reagents used in the Vosges-Proskauer test are

A

40% KOH and a-naphthol

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23
Q

In the Voges-Proskauer test, you are testing for the metabolic by products of which pathway?

A

Glucose—>pyruvic acid — acetoin

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24
Q

The decarboxylase tests determine

A

Whether the bacteria possess enzymes capable of removing the carboxyl group of specific amino acids in the test medium

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25
Q

Decarboxylase tests exist for all the following amino acids except

A

Tyrosine

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26
Q

The medium used in the decarboxylase test is called

A

Moeller’s decarboxylae base medium

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27
Q

Why does the Moeller decarboxylase base medium contain glucose if it is testing the decarboxylation of amino acids?

A

Decarboxylase are inducible enzymes produced in an acid pH

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28
Q

Using Moeller’s decarboxylase base medium, what color is a positive reaction and what causes this color to be produced?

A

Purple, alkaline environment produced?

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29
Q

Bacteria demonstrating weak decarboxylase activity

A

May take up to 4 days to be positive

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30
Q

Amino acids can be metabolized by these substances that remove an amine group. What is this substance?

A

Deaminase

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31
Q

This test is useful in the initial differentiation of Proteus, Morganella, and Providencia species from the rest of the enterobacteriaceae

A

Phenylalanine deaminase

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32
Q

This reagent is used to demonstrate a positive phenylalanine deaminase test

A

10% ferric chloride

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33
Q

The principle of the citrate test includes all the following except

A

The pH indicator changes from red to bright yellow

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34
Q

A bacterial DNase is

A

An endonuclease that cleaves internal phosphodiester bonds, resulting in smaller subunits of DNA

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35
Q

Extracellular DNase can be produced by

A

Staphylcoccus aureus

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36
Q

Some bacteria produce these enzymes that break down gelatin into amino acids. These enzymes are called

A

Gelatinase

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37
Q

What amino acid is the substrate in indole test broth?

A

Tryptophan

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38
Q

What two reagents can be used to visualize indole in the broth?

A

Ehrlichs’s and Kovac’s

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39
Q

What type of medium is used in the motility test?

A

Semi-solid

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40
Q

A positive test for motility

A

Shows hazy appearance throughout or movement away from a stab

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41
Q

Nam the two reagents that are needed to visualize nitrite in the nitrate reduction test

A

N,N-dimethyl-a-naphthylamine and sulfanilic acid

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42
Q

What does the oxidase test determine?

A

The presence of the cytochrome oxidase system that oxidizes reduced cytochrome with molecular oxygen

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43
Q

What medium is used in the urease test?

A

Christensen media

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44
Q

What does a lysine iron agar (LIA) slant contain?

A

Lysine, glucose, ferric ammonium citrate and sodium thiosulfate

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45
Q

The LIA slant is also useful in differentiating

A

Proteus, Morganella, and Providencia

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46
Q

Commercial identification systems fall into all of the following categories except

A

Use of nitrogen and sulfur sources

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47
Q

How are organisms identified with commercial identification kits?

A

Numeric codes

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48
Q

This identification system for Enterobacteriaceae has a series of 20 cupules attached to a plastic strip. Inside the cupules are lyophilized pH based substrates. What is the name of this system?

A

API 20E

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49
Q

Rapid identification of clinical isolates often involves commercially packaged identification kits and fully automated instruments. What do these kits use to assess the preformed bacterial enzymes?

A

Chromogenic or fluorogenic substrates

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50
Q

What advantage do the methods based on enzyme substrates have over conventional methods?

A

They do not require growth of the organism in the system

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51
Q

Which of the following agars is not selective for enterobacteriaceae?

A

Buffered charcoal yeast extract

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52
Q

The primary pathogens of the enterobacteriaceae include all the following except

A

Proteus mirabilis

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53
Q

What organim presents as a pink colony with a halo on MAC agar and a green metallic sheen on eosin methylene blue (EMB) agar?

A

E. Coli

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54
Q

E. Coli strains have all the following properties except

A

Can use citrate as a sole carbon source

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55
Q

Which organism is the most common cause of UTI in humans?

A

E. Coli

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56
Q

All of the following are categories of diarrhea-causing E. Coli except

A

EMEC

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57
Q

The E. Coli stereotype O157:H7 is associated with all the following except

A

Liver damage

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58
Q

A microbiologist is reading a stool culture and notices a mucoid pink colony on MAC agar. What is the most likely organism?

A

Klebsiella pneumonia

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59
Q

All of the following are clinically significant isolates of the genes Enterobacter, except

A

E. Hartmanni

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60
Q

A DNase-positive member of the family enterbacteriaceae is suggestive of

A

Serratia

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61
Q

What bacterium produces swarming colonies on nonselective media, such as sheep blood agar (SBA)?

A

P. Mirabilis

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62
Q

The most important cause of UTIs is

A

E. Coli

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63
Q

What organism in the genus Providencia is incriminated in nonsocomial outbreaks in burn units and has been isolated from urine culture?

A

Providencia Stuartii

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64
Q

What genus has the following characteristics; urea negative, positive for lysine decarboxylase, hydrogen sulfide, and indole, and does not grow on Simmon citrate?

A

Edwardsiella

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65
Q

You have isolated a bacterium from a stool culture that produces clear colonies on sorbitol MacConkey (SMAC) agar. Which of the following would be the most appropriate test to perform next?

A

Rapid Mehtlyumbelliferyl-b-D-glucuronide (MUG)

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66
Q

What is the name of the organism that has been a documented cause of nursery outbreaks of neonatal meningitis and brain abscesses?

A

C. Koseri

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67
Q

All of the following are biochemical features of salmonella except

A

Lactose positive

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68
Q

Which animals are a common source of salmonellla serotypes?

A

Cold-blooded animals (fish)

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69
Q

What substance produced by the salmonella spp., causes pastroenteritis, has been implicated as a significant virulence factor?

A

Enterotoxin

70
Q

What are the primary antigens used in serologic grouping of salmonellae?

A

Flagellar H antigen and somatic O antigen

71
Q

What organism possess the Vi antigen?

A

Salmonella typhi

72
Q

What disease produced by a salmonella spp. is a severe form of enteric fever?

A

Typhoid fever

73
Q

All of the following are symptoms of salmonellosis that Marty appear 8-36 hour after ingestion of contaminated food except

A

Headache

74
Q

Why is is the most cases of salmonella food poisoning are not treated with antibiotics?

A

The disease is self-limiting and will subside on its own

75
Q

In carrier state, where are pathogenic salmonella carried?

A

Gallbladder

76
Q

All of the following are characteristics of shigella spp. except

A

Urea positive

77
Q

Bacillary dysentery caused but this organism is marker by penetration of intestinal epithelial cells following attachment of the organisms to mucosal surfaces, local inflammation, shedding of the intestinal lining, and formation of ulcers that follow the epithelial penetration. What is this organism?

A

Shigella

78
Q

What bacterium is the causative agent of the plaque?

A

Yersinia pestis

79
Q

What enteric organism may produce a blue-violet pigment on non-blood containing media?

A

Kluyvera

80
Q

Why can direct microscopy not be used to provide a presumptive identification of the enteric bacteria?

A

The microscopic characteristics are indistinguishable from other gram-negative

81
Q

A microbiologist is reading stool cultures plates. She is looking fr enteric pathogens on the MAC plate. What do they look like?

A

Clear, odorless colonies

82
Q

A microbiologist is reading stool culture plates. She sees an organism that has a dry, pink colony with a surrounding “halo” of pink on MAC. What is a good presumptive identification of this organism?

A

Escherichia/citrobacter-like organism

83
Q

A microbiologist is reading stool culture plates. She sees an organism that has a large, mucoid pink colony on MAC. What is a good presumptive identification of this organism?

A

Klebsiella/enterobacter-like organism

84
Q

Which of the following is a curved, gram-negative rod that grow on thiosulfate citrate bile salts sucrose (TCBS) agar?

A

Vibrio

85
Q

What is the name of the organism that causes the disease cholera?

A

V. Cholerae

86
Q

Most infections caused by Vibrio cholerae are associated with

A

Ingestion of undercooked seafood

87
Q

All of the following are biochemical characteristics of vibrio spp. except

A

Oxidase negative

88
Q

What disease manifests in acute cases as a severe gastroenteriritis, accompanied by vomiting followed by diarrheic stools that described as rice water and occur 10-30 times a day?

A

Cholera

89
Q

How is cholera treated?

A

Copious amounts of intravenous fluids

90
Q

What is the name of the organism that is responsible for for “summer diarrhea” in japan?

A

V. Parahaemolyticus

91
Q

Which of the following Vibrio species is most likely to be recovered from extraintestinal tract infections e.g. septicemia?

A

V. Vulnificus

92
Q

What species of aeromonas is the most frequently associated with GI infections?

A

A caviae

93
Q

Aermonads have been implicated in all the following disease except

A

Pneumonia

94
Q

What do aeromonad colonies look like on cefsulodin-novobiocin (CIN) agar?

A

Pink colonies

95
Q

What two biochemical tests help distinguish aeromonas spp. from other enterics?

A

Oxidase and indole

96
Q

Aeromonas are generally susceptible to all these antimicrobial agents except

A

Ampicillin

97
Q

All of the following characteristics describe the genus plesiomonas except

A

Oxidase negative

98
Q

What environment is aeromonas spp. most commonly found in?

A

Fresh water

99
Q

Most vibrio sp. are generally halophilic. However which one can also grow is an environment with 0% sodium chloride?

A

V. Cholerae

100
Q

What is the name of the organism that is strongly associated with gastric, peptic, and duodenal ulcers, as well as GI carcinoma?

A

Helicobacter pylori

101
Q

What organism may play a role in Guillain-Barré syndrome (GBS)?

A

Campylobacter

102
Q

When collecting specimens that may contain campylobacter spp. bacteria, what transport medium should they be placed in, if a delay in transport is possible ?

A

Cary-Blair

103
Q

CAMPY-BAP (blood agar plate) contains

A

Brucella agar base, 10% sheep RBCs, vanomycin, trimethoprim, polymyxin B, amphotericin B, and cephalothin

104
Q

What temperature is an optimal growth temperature for campylobacter jejuni?

A

42C

105
Q

What type of an atmosphere do campylobacters require for growth?

A

Microaerophilic and Capnophilic

106
Q

What oraganim has a microscopic morphology of tiny, curved gram-negative rods, with S-shapes or seagull-wing shapes on gram stain?

A

Campylobacter

107
Q

A Campy blood agar plate incubated at 42C from a stool exhibits colonies that are nonhemolytic, moist, “runny looking” and spreading. The gram stain shows tiny gram-negative rod with some S-shapes and seagull-wing shapes. What is growing on the plate?

A

Campylobacter

108
Q

How is Helicobacter pylori presumptively identified?

A

A rapid urease test done on a gastric biopsy

109
Q

What is the drug of choice for treating intestinal campylobacterosis?

A

Erythromycin

110
Q

What biochemical test will differentiate nonfermenters from enterobacteriaceae (except pleisomonas)?

A

Oxidase

111
Q

What substance do nonfermenters fail to ferment in traditional media?

A

Carbohydrates

112
Q

All of the following are characteristics of pseudomonads except

A

Indole-positive

113
Q

The three nonfermenters that make up the majority of isolates routinely seen in clinical laboratories include all of the following except

A

Pseudomonas putida

114
Q

What pseudomonas sp. is the nonfermenter that is the leading cause of nosocomial pneumonia and bacteremia?

A

Pseudomonas aeruginosa

115
Q

What organism is a common cause of pulmonary disease among individuals with cystic fibrosis?

A

P aeruginosa

116
Q

All of the following are poor prognostic factors associated with pseudomonas aeruginosa bacteriemia except

A

Anemia

117
Q

Which of the following is a virulence factor of pseudomonas aeruginosa?

A

All of the above
*endotoxin
*exotoxins
*capsule

118
Q

An oxidase-positive, nonfermentative gram-negative bacillus that characteristically produces dry, wrinkled colonies describes

A

Pseudomonas stutzeri

119
Q

A microbiologist is reading the plates from a sputum culture. On the sheep blood agar (SBA), the microbiologist sees the flat spreading colonies with a metallic sheen. On certified agar, a fluorescent green color is seen in the medium with clear colonies. On MacConkey, medium clear colonies are seen that have a fruity or grapelike odor. What is the most likely organism?

A

P. Aeruginosa

120
Q

Psuedomonas aeruginosa is resistant to all the following antimicrobial agents except

A

Fluroquinolones

121
Q

An H2S-positive, oxidase-positive, nonfermenters describes

A

Shewanella

122
Q

Which gram-negative coccobacilli can appear as gram-positive cocci in smear made from blood cultures bottles?

A

Acinetobacter spp.

123
Q

In what single setting does strenotrophomonas matophilia typically produce disease?

A

Nosocomial

124
Q

What organism is associated with pneumonia in patients with cystic fibrosis or chronic granulomatous disease (CGD)?

A

Burkholderia capacia

125
Q

What nonfermenter may produce a weak, slow, positive oxidase reaction?

A

Burkholderia cepacia

126
Q

Which plant pathogen may be mistaken for Burkholeria cepacia?

A

Burkholderia gladioli

127
Q

What is the causative agent of gleaners?

A

B. Mallei

128
Q

What organisms causes melioidoisis?

A

B. Pseudomallei

129
Q

Characteristics of most members of the family flavobacteriaceae

A

All of the above
*week fermenters
*cause of nosocomial infections
* ubiquitous in soil and water

130
Q

Elizabetkingae meningosepticum causes all the following disease except

A

Gastroenteritis

131
Q

Characteristics of Moraxella include

A

All of the above
*oxidase-positive and nonmotile
*biochemically inert ad aerobic
* susceptible to penicillin and opportunistic pathogens

132
Q

Which nonfermenter is considered by government agencies to be a potential bioterroist agent?

A

Burkholderia mallei

133
Q

A microbiologist is reading the plates from a sputum culture. The culture is from a patient with cystic fibrosis. One organism dominates the blood agar, chocolate, and MacConkey plates, The MacConkey plate shows an organism with a green pigment and a metallic sheen. The probable identification for this organism is

A

Pseudomonas aeruginosa

134
Q

The bacterium is said to have a fruity or grapelike smell

A

Pseudomonas aeruginosa

135
Q

All of the following are categories of bacterial growth requirements for oxygen and carbon dioxide except

A

Ambient air (95% O2 and 5% CO2)

136
Q

What is anaerobe?

A

An organism that does not require oxygen to live

137
Q

What is an obligate anaerobe?

A

An organism that grows only in the absence of molecular oxygen

138
Q

What substances do organisms that use oxygen have to protect themselves from superoxide anions?

A

Superoxide dismutase and catalase

139
Q

Anaerobes outnumber aerobes in all of the following locations, except

A

Skin

140
Q

All of the following organisms are found on the skin under normal conditions except

A

Clostridium

141
Q

All of the following organisms are found in the GI tract, except

A

Propionibacterium

142
Q

Which of the following is characteristic of members of the genus Clostridium?

A

spore-forming anaerobic bacilli

143
Q

What disease does clostridium perfringens cause?

A

Food poisoning

144
Q

What disease does clostridium botulinum cause?

A

botulism

145
Q

What disease does clostridium tetani cause?

A

Tetanus

146
Q

What organism mostly commonly cause gas gangrene?

A

C. Perfringens

147
Q

An older adult patient in a nursing home is recovering from bacterial pneumonia. The patient has been on a lengthy regiment of antimicrobial agents. Subsequently, the patient is diagnosed with pseudomemebranous colitis. What organism is the most likely cause?

A

Clostridium difficile

148
Q

All of the following are non-spore forming, anaerobic, gram-positive bacilli, except

A

Clostridium

149
Q

An immunosuppressed patient notices sinus tracts that are draining pus. He also notices that there appear to be small, hard “nuggets” int he pus. What disease is he mostly likely suffering from?

A

Actinomycosis

150
Q

Bacterial vaginosis is a synergistic infectious process involving all the following bacteria except

A

Eubacterium

151
Q

The four major groups of anaerobic gram-negative bacilli include all the following except

A

Mobiluncus

152
Q

Which of the following bacteria is most likely the cause of tooth abscesses/

A

P. Gingivalis

153
Q

What are two important factors that must be taken into consideration when transporting specimens for anaerobic culture?

A

Minimum exposure to oxygen and preventing drying out

154
Q

Which of the following is considered a better specimen a better specimen for anaerobic culture than a swab?

A

Aspirate

155
Q

All of the following procedures should be performed on clinical specimens to recover anaerobic bacteria, except

A

Kinyoun Stain

156
Q

Gram stains of specimens for anaerobic cultures should be examined for all the following reasons except

A

The clinical and laboratory standards institute (CLSI) guidelines recommend gram stains on all anaerobic specimens

157
Q

What is the ideal anaerobic incubation system?

A

Anaerobic chamber

158
Q

How long are anaerobic cultures routinely held in the laboratory?

A

5-7 days

159
Q

What evidence indicates the presence of anaerobes in cultures?

A

All of the above

160
Q

How are suspected colonies of anaerobes processed?

A

All of the above
*gram stain morphology and reaction is observed
*an aerotolerance test is set up
*a pure culture/subculture place is inoculated and appropriate disks are added

161
Q

How is the true gram stain reaction of an anaerobe determined?

A

Special potency disks

162
Q

A vaginal swab is received for anaerobic culture. How should this request be handled or processed?

A

Contacts the physician, this is an unacceptable specimen

163
Q

What disk is used to be presumptively identify peptostreptococcus anaerobius?

A

Sodium polyanethol sulfonate (SPS)

164
Q

One egg-yolk agar, clostridium perfringens will demonstrate

A

Off white precipitate around colonies

165
Q

An anaerobic culture reveals colonies with a double zone of hemolysis of SBA plate. There was no growth on plates incubated aerobically. The gram stain of that organism was a boxcar-shaped, gram-positive bacillus. What organisms is this?

A

Clostridium perfringens

166
Q

Material from an intestinal abscess produces gray colonies with a brown color in the area around the colonies on a BBE plate incubated anaerobically. There is also a dark precipitate in the medium in the areas of heavy growth. A Gram stain of the colonies reveals gram-negative coccobacilli. What is the presumptive identification of this organism?

A

B. Fragilis

167
Q

All of the following reasons are cited for performing antimicrobial susceptibility testing on anaerobes by the clinical and CLSI except

A

The determine the resistance mechanisms in anaerobes

168
Q

All of the following are approaches to treating anaerobic infections except

A

Enzyme inactivators

169
Q

What is the most common causative agent of gas gangrene?

A

Clostridium perfringens

170
Q

How does clostridium difficile produce psuedomembrnous colitis and antibiotic-associated diarrhea?

A

Toxin A and toxin B (exotoxins_

171
Q

After 24-hour incubation, an SBA from a vaginal culture reveals heavy growth of a-hemolytic, pinpoint rough colonies. A catalase test is performed and it is negative. What organism should you suspect?

A

Lactobacillus

MLT Microbiology (8 decks)

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