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MLT Microbiology > Unit 2 > Flashcards

Unit 2 Flashcards

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1
Q

Colony morphology is defined as

A

Colony characteristics

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2
Q

Which of the following descriptions will directly facilitate ID of bacteria?

A

Physical characteristics of colony morphology

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3
Q

An upper respiratory specimen contains many indigenous organisms which may be time consuming, cost prohibitive and insurmountable. What should the microbiologist do?

A

Differentiate the potential pathogens from the “usual” inhabitants of the upper respiratory tract and direct the diagnostic work up only to potential pathogens

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4
Q

When microbiologists set up a biochemical ID using a commercial system on a suspected pathogen from a culture, they must

A

Correlate colony characteristics with the suspected ID of the organism

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5
Q

Generally, microbiologists observe the colonial morphology of organisms on primary culture after how many hours of incubation?

A

18-24 hours

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6
Q

Plate reading is

A

A comparative examination of bacteria growth on a variety of culture media

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7
Q

MacConkey (MAC) agar is used to

A

Differentiate between lactose fermenters and lactose nonfermenters

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8
Q

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

A

Clear, colorless colonies

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9
Q

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

A

Escheriochia/citrobacter-like organism

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10
Q

The relative concentration of bacteria on culture plates in directly proportional to

A

The concentration in which they are present in the clinical specimen

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11
Q

Alpha Beta-hemolysis is

A

Partial lysing of erythrocytes in a BAP around and under the colony

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12
Q

Beta (beta)-hemolysis is

A

Complete clearing or erythrocytes in a BAP around and under the colony

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13
Q

Gamma (y)-hemolysis is

A

When organisms have no lytic effect on the erythrocytes in the BAP

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14
Q

Colonies growing on the SBA have discolored the media to a green color around and under the colonies. This is consistent with which type of hemolysis?

A

Delta

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15
Q

The colonies growing on the SBA have produced a wide, deep, clear zone around and under the colonies. This is consistent with which type of hemolysis?

A

Gamma (no hemolysis)

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16
Q

When differentiating colony size on the culture place, what organisms generally have the larger colonies by comparison?

A

Gram-negative rods

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17
Q

The edge of the colonies is described as all the following except

A

Glasslike

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18
Q

Colonies of Bacillus anthracite are described as

A

Medusa’s heads

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19
Q

Swarming is

A

A hazy blanket of growth on the surface of the agar that extends way beyond the streak lines

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20
Q

A microbiologist is a reading a vaginal culture. She sees the very white colonies that are non-hemolytic on a BAP but appear to have feet. What organism could this possibly be?

A

Yeast

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21
Q

The elevation of bacterial colonies is described by all of the following except

A

Pointed

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22
Q

A term used to describe colonies that resemble coins is

A

Umbilicate

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23
Q

The density of the bacterial colony can be described by all the following, except

A

Ground glass

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24
Q

The term used to describe colonies that are solid in color and that do not allow any light to pass through it

A

Opaque

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25
Q

All of the following terms are used to describe the consistency of a bacterial colony, except

A

Smooth

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26
Q

All of the following colors are commonly used to describe bacteria, except

A

Orange

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27
Q

What organism forms a small, fuzzy-edged colony with an umbonate center on blood or CHOC agar?

A

Eikenella corrodens

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28
Q

When looking at a tube of thioglycollate broth, streamers or vines and puffballs are visible. What organism grows like this is thioglycollate?

A

Streptococcus spp.

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29
Q

All of the following characteristics are used to describe bacterial colony characteristics except

A

Temperature

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30
Q

Nucleic Acid hybridization is

A

Coupling of complementary single-stranded nucleic acid molecule

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31
Q

The target nucleic acid strand is

A

The DNA or RNA sequence unique to the organism of interest

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32
Q

The probe is

A

Used to detect the target nucleic acid molecule

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33
Q

Common uses of probes include all of the following except

A

Abnormal WBC detection

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34
Q

The variables that affect the outcome of a given hybridization reaction include all of the following except

A

Organic acid concentration

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35
Q

How is the stability of a given hybrid calculated?

A

By determining the melting temperature of a probe

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36
Q

How do high probe concentrations affect a given by hybridization reaction?

A

Lower the reaction time

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37
Q

Many hybridization assay conditions are based on the expectation that a probe

A

Has exact complementarity to the target nucleic acid

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38
Q

In hybridization reaction, the pH affects

A

The stability of double-stranded nucleic acid molecules in solution

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39
Q

The function of the probe is to

A

Form a duplex with every complementary sequence available in the reaction

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40
Q

Which of the following compounds are used for labeling probes?

A

Fluorescein

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41
Q

The principle of solid support hybridization (often called blotting) is :

A

The target sequence is part of the solid support, and the probe, which is in isolation, hybridizes to the target

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42
Q

The southern blot test separates

A

DNA

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43
Q

The steps for performing the southern blot test include all the following except:

A

After the labeled probe is hybridized to specific target , the DNA is electrophoresed again, then dried and read

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44
Q

A northern blot is used to detect

A

RNA

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45
Q

The steps is separated the Northern blot test include all the following except

A

The membrane is then transferred to a gel so that the RNA can be immobilized in the gel

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46
Q

In situ hybridization, first described in 1969, is where

A

DNA or RNA can be detected directly in tissue with labeled probes

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47
Q

The principe of in-solubility hybridization is

A

The hybridization between a labeled probe and target nucleic acids in a liquid solution in tubes or in microtiter wells

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48
Q

The AccuProbe system uses the following technology prinicple

A

A single-stranded, chemiluminescent-labeled DNA probe is designed to hybridize to the target organisms ribosomal RNA (rRNA) forming a DNA:RNA duplex

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49
Q

PCR includes all of the following except

A

Gene expression

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50
Q

PCR requires all the of the following components, except

A

DNA helicase

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51
Q

This piece of instrumentation is a integral part of the PCR process

A

Thermal cycler

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52
Q

In a PCR, the target DNA is

A

Exponentially amplified over many cycles of PCR

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53
Q

During the denaturation step in PCR

A

The target double-stranded DNA is separated into single strands

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54
Q

The goal of the primer annealing step is to

A

Hybridize oligonucleotide primers to the denatured, single-stranded target DNA strands

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55
Q

What is the purpose of the primer extension?

A

To produce PCR products

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56
Q

The most commonly used polymerase is

A

Taq DNA polymerase

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57
Q

This cation is required for the proper function of the Taq DNA polymerase

A

Mg

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58
Q

One of the most significant drawbacks to PCR is:

A

The process is easily contaminated

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59
Q

What chemical has been very successful in reducing carryover from PCR assays?

A

Uracil-N-glycosylate

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60
Q

The most common nucleic acid stain used after separation by agarose gel electrophoresis is

A

Ethidium bromide

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61
Q

The advantages of real-time PCR over stranded PCR include all the following except

A

RT-PCR assay will contaminate equipment, reagents, and work spaces

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62
Q

What is the fluorescence resonance energy transfer (FRET) methodology?

A

The transfer of energy is made from a donor dye molecule to an acceptor dye

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63
Q

What is the principle of the 5’ nuclease assay (TaqMan)?

A

The Taq DNA polymerase extends from the primers and replicates the template to which the TaqMan probe is annealed. The reporter dye is released by 5’ nuclease activity of the polymerase first and then the probe is released, thus increasing the fluorescence

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64
Q

A Scorpion primer

A

Uses a single ogliocnucleotide to prime a specific sequence and to detect accumulated PCR product

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65
Q

The most sensitive technique available for detecting and quantifying messenger RNA is

A

Reverse-transcription PCR

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66
Q

Multiplex PCR is good for

A

Simutaneously detecting two or more different targets from one PCR tube

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67
Q

Nested PCR is very sensitive and specific because

A

The assay itself basically serves as a form on internal control and ensures specificity

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68
Q

NASBA stands for

A

Nucleic acid sequence-based amplification

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69
Q

Accurate epidemiological surveillance of specific organisms is needed for all the following reasons except

A

The increase in nosocomial infections

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70
Q

All of the following non amplified typing technique are used to differentiate strains of an organism except

A

Multilocus sequence typing

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71
Q

All of the following amplified typing techniques are used to differentiate strains for an organism, except

A

PFGE

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72
Q

What is the principle of restriction enzyme analysis of chromosomal DNA?

A

DNA is extracted and isolated, and digested with a restriction enzyme. The resulting RFLP pattern is analyzed by agarose gel electrophoresis and transferred to a membrane

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73
Q

This method is good for separating large DNA fragments is a low-percentage, low-melt agarose gel by an angled electrical field that periodically changes orientation

A

PFGE

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74
Q

This method analyzes gene expression polymorphism by analyzing proteins.

A

Multilocus enzyme electrophoresis

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75
Q

This technique is a popular method of DNA fingerprinting

A

Random amplified polymorphic DNA

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76
Q

When an organisms genome is sequenced, all of the following information can be obtained except

A

Disease causing mechanisms

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77
Q

The basis for this method is a microscopic grouping of DNA molecules attached to a solid support mechanism. Silicon chip, glass, or plastic have been used as he solid surfaces. What method is this?

A

DNA microarray

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78
Q

What is proteomics?

A

The study of proteins on a cellular level

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79
Q

Relatively nontoxic antimicrobial therapeutic agents include all of the following, except

A

Heavy metals

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80
Q

Antibiotics work by targeting all of the following except

A

Bacterial plasmid DNA

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81
Q

Which of the following public health issues in uniting scientists from across the world to develop strategies to address it?

A

Antibiotic resistance

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82
Q

Mechanism that mediate intrinsic antibiotic resistance include all of the following except

A

Alternate biosynthetic pathways

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83
Q

Antibiotic mechanism of action target all the following, except

A

Blocking the Embden-Meyerhof pathway

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84
Q

Both gram-positive and gram-negative bacteria have an inner cytoplasmic membrane that is composed of

A

Phospholipids and proteins

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85
Q

In gram-positive bacteria, this is substantially thicker and more multilayered than in gram-negative bacteria

A

Peptidoglycan

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86
Q

The outer membrane of gram-negative bacteria composed of

A

Lipopolysaccharides, phospholipids and porin proteins

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87
Q

All of the following are beta-lactate antibiotics except

A

Monoterpenes

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88
Q

Penicillins, cephalosporins, monobactams, and carbapenems all have this ring in their structure that is responsible for inhibiting the transpeptidation reaction, resulting in bacterial lysis and cell death

A

Beta-lactam

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89
Q

What is the mechanism of action of the glycopeptides (vancomycin and teicoplaninin)?

A

The glycopeptides bind to the substrate of the transpeptidation enzyme and disrupt the cell membrane construction

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90
Q

Which antibiotic inhibits folate synthesis, proving the essential precursor molecule, pyridine thymidylate, needed in DNA synthesis?

A

Sulfamethoxazole

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91
Q

This antibiotic affects the DNA replication by targeting topoisomerases II and IV, enzymes considered important in controlling DNA replication

A

Quinolone

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92
Q

This antibiotic interferes with DNA transcription by blocking of RNA chain elongation

A

Rifampin

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93
Q

All of the following antibiotics target the 50S ribosomal subunit to prevent mRNA translation in the bacteria, except

A

Quinolones

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94
Q

These antibiotics are cationic carbohydrate-containing molecules, and their positive charge provides the basis for the interaction with the 30S ribosomal subunit. What class of antibiotic are these?

A

Aminoglycosides

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95
Q

The members of the polyketide class of antibiotic include all the following except

A

Oxycycline

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96
Q

The members of the macrolide class of antibiotics include all the following except

A

Rifamycin

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97
Q

These two classes of antibiotics allow initiation and mRNA translation to begin, but they act by inhibiting peptide elongation

A

Macrolides and tetracyclines

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98
Q

All of the following are recently approved classes of antibiotics that target protein synthesis, except

A

Sixth generation cephalosporins

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99
Q

Intrinsic mechanisms of resistance are

A

Innate characteristics of the bacterium and transmitted to progeny

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100
Q

Acquired mechanims of resistance are those that

A

Result from acquisition of DNA by acquisition of extrachromosomal DNA

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101
Q

What is porin?

A

Outer membrane channels that permit the inflow of nutrients and the outflow of wastes

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102
Q

This type of pathogen may demonstrate decreased or loss of porin synthesis in combination with other resistance mechanisms, resulting in multi drug resistant pathogens

A

Nosocomial

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103
Q

Biofilms are groups of bacteria that are irreversibly attached to surfaces and are embedded in a matrix of extracellular polymeric substances. They are most commonly found on

A

Indwelling medical devices

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104
Q

Efflux pumps

A

Function as transported proteins involved in the removal of toxic substances from the interior of the cell to the external environment

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105
Q

The beta-lactam agents consist of all the following antibiotics, except

A

Vancomycin

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106
Q

Beta-lactamases hydrolyze Beta-lactam antibiotics using two distinct mechanisms: those having metallic-based mechanism of action and those with

A

A serine-based mechanism of action

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107
Q

How do the Beta-lactamase inhibitors work?

A

By acting as substrates for the Beta-lactamase and reducing their effect on the antibiotic

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108
Q

Acquired antibiotics resistance mechanisms include

A

All of the above
*efflux mechanisms
*acquisition of new targets
*modification of existing antibiotic targets

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109
Q

Streptococcus pneumoniae and streptococcus pyrogenes use efflux as an effective mechanism for acquired resistance to

A

Macrolides

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110
Q

The primary mechanism of resistance to this antimicrobial class is modification by mutations encoding single amino acid changes in these targets. What antimbiotic class is this?

A

Quinolones

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111
Q

This type of resistance mechanism modifies the antibiotic targets and results in reduced affinity of antibiotics for their microbial targets

A

Enzyme alteration

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112
Q

A young, healthy patient goes into the hospital for reconstructive knee surgery and spikes a fever the day after surgery. The doctor finds the patient has a nosocomial infection with methicillin-resistant staphylococcus aureus (MRSA). What antibiotic should the doctor use to treat this patient?

A

Vancomycin

113
Q

A patient undergoes a colon resection. Because of the amount of bacteria present in the colon, the physician put the patient on broad-spectrum antibiotics after surgery. The patient develops a fever 2 days after surgery. He developed an infection with vancomycin-resistant enterococci (VRE). What antibiotics can be used to treat this organism?

A

Synercid

114
Q

How does staphylococcus aureus acquire resistance to methicillin?

A

Mobile DNA element

115
Q

This is one of the first resistance mechanisms identified and is a strategy that bacteria use successfully to survive the action of many classes of antibiotics

A

Acquisition of inactivating enzymes

116
Q

Extdende beta-lactamase target all the following antibiotics except

A

Macrolides

117
Q

Resistance to aminoglcosides is mediated by

A

All of the above
*efflux
*changes in the target site
*impermeability or by enzymatic modification of amino and hydroxy moieties appended to the cyclitol rings

118
Q

Plasmids are

A

Circular structures present in bacteria that contain genes encoding proteins and DNA and have the capacity to self-replicate and portion into daughter cells during cellular division

119
Q

Transposons are

A

DNA elements that encode transposition an excision function and can transpose from one place on the chromosome to another

120
Q

Integrons are

A

Genetic elements capable of integrating resistance genes (cassettes) by an integrin-encoded, site specific recombinase

121
Q

Insertion sequence are

A

DNA elements found in bacteria that carry genes only for the enzymes needed to promote their own transportation

122
Q

When should antimicrobial susceptibility testing be performed on a bacterial isolate from a clinical specimen?

A

When the organism is part of the normal microbiota

123
Q

A 12-year old girl goes to the doctor complaining of a sore throat, fever, headache, and general malaise. The doctor does a quick strep test that is positive for group A beta-hemolytic streptococcus. No antibiotic testing is needed because streptococcus is

A

Universally susceptible to penicillin

124
Q

Important factors that must be considered when determining whether antimicrobial susceptibility testing is warranted include

A

All of the above
*the body site from which the organism was isolated
*the presence of other bacteria and the quality of the specimen from which the organism was grown
*the host’s status

125
Q

Why should antimicrobial susceptibility testing or normal flora isolates or isolates likely to represent contamination or colonization not be performed?

A

This may encourage a physician to treat a normal condition

126
Q

Why would normal flora isolating from immunosuppressed patients undergo antimicrobial susceptibility testing?

A

Species usually viewed as normal flora may be responsible for an infection in an immunosuppressant patient

127
Q

How are antibiotics chosen for inclusions into laboratory antimicrobial testing protocols?

A

Both B and C
*the CLSI recommends the drugs that should be tested and reported for each type of specimen
*the institutional pharmacy and therapeutics committee sets the list of drugs that are used in their facility

128
Q

Two antibiotics are contrainindicated in pediatric patients. They are

A

Tetracycline and fluoroquinolones

129
Q

Because the identity of the bacterial isolate is often unknown at the time the susceptibility testing is performed, it’s may include drugs that are inappropriate for reporting. What does the microbiologist odor when this occurs?

A

A drug should not be indiscriminately reported because results may be misleading

130
Q

A primary tenet of antimicrobial therapy is to use

A

All of the above
*the least toxic agents
*the most cost-effective agents
*the most clinically effective agents

131
Q

Guidance for the development of a selective-reporting or cascade-reporting protocol for antibiotics is available from the

A

CLSI

132
Q

As a general guideline, it is suggested that within a particular antimicrobial class, primary (ggroup A) agents should be reported first and secondary (group B) agents should be reported only if

A

The patient cannot tolerate the primary agents

133
Q

Why are aminoglyecosides not an effective treatment for meningitis?

A

They do not cross the blood-brain barrier

134
Q

When would it be appropriate for institution to routinely test group C agents?

A

If a particular institution routinely encounters large numbers of isolates resistant to group A and group B agents

135
Q

What antibiotics should be reported for UTIs?

A

Urinary tract active agents

136
Q

What is the most critical step in any susceptibility test?

A

Inoculum preparation

137
Q

What is the most widely used method of inoculum standardization?

A

McFarlnad turbidity standards

138
Q

What McFarland standard provides turbidity comparable to that of a bacterial suspension containing approximately 1.5 x 10^8 CFU/mL?

A

0.5

139
Q

The minimal inhibitory concentration (MIC) is

A

The lowest antibiotic concentration to inhibit the growth of the an organism

140
Q

What concentrations of antibiotics are typically tested in MICs ?

A

Serial twofold dilution concentration are tested

141
Q

Note that for some antimicrobial agents, different MIC interpretive criteria exist for

A

Organisms or organism groups

142
Q

What broth is recommended on the tube dilute MIC tests?

A

Mueller-Hinton

143
Q

The broth microdilution MIC test uses these for the testing

A

Multi well microdilution trays

144
Q

What is the approximate final concentration of organisms on each well of a microdilution tray?

A

5 x 10^5 CFU/mL

145
Q

When reading broth microdilution MIC testing, the MIC for a particular drug is

A

The lowest concentration showing no obvious growth

146
Q

What is the storage temperature for frozen panels?

A

-20 X to -70 C

147
Q

What’s is a breakpoint panel?

A

An MIC panel with only one or a few concentration of each drug

148
Q

On a breakpoint panel, when two concentrations aren tested and no growth is present in either well, isolate is

A

Susceptible

149
Q

On a breakpoint panel, when there is growth in the low concentration but no growth in the high concentration, the isolate

A

Intermediate

150
Q

One a breakpoint panel, when there is growth in both wells, the isolate is

A

Resistant

151
Q

In terms of MIC microdilution trays, a skipped well occurs

A

When there is growth at higher concentrations and no growth at one or more of the lower concentration wells

152
Q

In this method of antimicrobial susceptibility testing, specfic volumes of various concentrations of antimicrobial solutions are dispensed into premeasured volumes of molten and cooled agar, which is subsequently poured into standard Petri dishes. Organisms are inoculated onto the plate. What type of antimicrobial susceptibility testing is this?

A

Agar dilution

153
Q

In this type of antimicrobial susceptibility test, a McFarland 0.5 standardized suspension of bacteria is swabbed over the surface of a Mueller-Hinton agar plate, and paper disks containing single concentrations of each antimicrobial agent are placed onto the inoculated surface. What is the name of this?`

A

Kirby-Bauer

154
Q

A zone of inhibition is

A

The area around the antibiotic disk where the bacteria cannot grow

155
Q

What agencies develop the zone interpretive Criteria?

A

FDA and CLSI

156
Q

In the Kirby-Bauer test, what is used to grow streptococci that do not grow adequately on unsupplemented Mueller-Hinton agar?

A

Mueller-Hinton agar with 5% sheep blood

157
Q

After the plate is incubated in the Kirby-Bauer test, what occurs?

A

The diameter of each inhibition zone for each antibiotic is measured using a ruler or caplier

158
Q

Once zone measurements have been made, the mL reading for each antimicrobial agent is

A

Interpreted as susceptible, intermediate or resistant

159
Q

Agar dilution and disk diffusion tests for streptococcus pneumonia and streptococcus spp. use

A

Mueller-Hinton agar supplemented with 5% sheep blood

160
Q

A patient is admitted to the hospital with a diagnosis of endocarditis. Two separate blood cultures grow out of viridans streptococci. The penicillin MIC of the organism is 0.12 ug/mL. What antibiotic should the physician prescribe?

A

Penicillin

161
Q

When performing disk diffusion testing with Haemophilus influenza and H. Parainfluenza what type of medium is used?

A

Mueller-Hinton with hematin and nicotinamide adenine dinucleotide (NAD)

162
Q

Therapy of disseminated meningococcal infections and various types of Gonococcal (GC) infections are

A

Generally empiric based on recommendation of CDC

163
Q

A man goes to his doctor because he has a cloudy substance dripping from his penis. A gram stain is performed and gonorrhea is isolated. What is the drug of choice to treat this infection?

A

Ceftriaxone

164
Q

On what media is Kirby-Bauer testing performed for Neisseria gonorrhoeae?

A

GC agar base supplemented with various nutrients

165
Q

What type of antimicrobial susceptibility testing method does CLSI recommend for anaerobes?

A

Agar dilution

166
Q

How long are MIC panels for anaerobes incubated?

A

48 hours

167
Q

The CLSI has published methods for susceptibility testing of several agents of potential bioterroism, including Brucella anthracis, yersinia pestis, burkholderia mallei, B. Pseudomallei, francisella tularensis and Brucella spp. How does CLSI suggest clinical laboratories perform antimicrobial susceptibility testing on these isolates/

A

Do not attempt to perform antimicrobial susceptibility on any these isolates; refer them t a Public health laboratory equipped to handle them

168
Q

Oxacillin-resistant staphylococcus aureus is called

A

Methicillin-resistant S. Aureus (MRSA)

169
Q

In vitro testing conditions that can be modified to enhance the expression of oxacillin resistance include all the following except

A

Use Mueller-Hinton media

170
Q

Oxacillin-resistant staphylococci can appear susceptible in vitro to other B-Lactam agents such as

A

Cephalosporins

171
Q

To obtain a bacterial effect in enterococci, ampicillin must be given in combination with

A

Aminoglycosides

172
Q

Which enterococcus is/are the most common species demonstrating vancomycin resistance among clinical isolates?

A

Enterococcus faecium

173
Q

Spontaneous mutations occur in the B-lactamase genes that results in extended-spectrum B-lactamases (ESBL). The ESBL inactivate

A

All of the above
* cephalosporins
* penicillins
* aztreonam

174
Q

When testing E. Coli, Klebsiella spp., and proteus mirabilis, which drug is mostly likely to indicate the presence of an ESBL?

A

Cefpodoxime

175
Q

What antibiotics are active against ESBL-producing strains of bacteria?

A

Carbapenems

176
Q

What principle do most current automated antimicrobial susceptibility instruments use to read growth/?

A

Turbidimetric detection

177
Q

The BD Phoenix system uses this principle to measure bacterial growth in the susceptibility test wells

A

Redox indicator system

178
Q

How many hours of incubation are necessary for the antimicrobial susceptibility test run on the BD phoenix?

A

6-8 hours

179
Q

What principle does the Microscan walk away SI use to determine antimicrobial susceptibility?

A

Turbidimetry

180
Q

What principle does the TREK ARIS 2X system use to determine antimicrobial susceptibility?

A

Hydrolysis of a fluorogenic substrate

181
Q

What automated system was originally designed for use in outer space?

A

VITEK

182
Q

What principle does the VITEK series use to determine antimicrobial susceptibility?

A

Turbidimetry

183
Q

What is the principle of the Etest?

A

Establishing an antimicrobial density gradient in agar

184
Q

Who sets the criteria in the table of values that relate the diameter of the zone to a category of susceptibility in disk diffusion testing?

A

CLSI

185
Q

The inhibition zone size and MIC interpretive criteria published by the CLSI are established by careful analysis of all of the following except

A

Pharmacodynamic data

186
Q

If the MIC or zone size is interpreted as susceptible using the latest CLSI tables

A

The clinical interpretation of the result is the patients infecting organism should respond to therapy with that antimicrobial agent using the dosage normally recommended for that type of infection and that species

187
Q

If the MIC or zone size is interpreted as resistant using the latest CLSI tables

A

The patients infecting organism in unlikely to be inhibited by the usually achievable concentration of the antimicrobial agent based on the dosages normally used with that drug

188
Q

If the MIC or zone size is interpreted as intermediate using the latest CLSI tables

A

The patients infecting organism is likely to require the maximum amount of antimicrobial or more than can be achieved and for which of the clinical response is likely to be less than with susceptible strain

189
Q

All of the following organisms often produce-B-lactamase, except

A

Neisseria Meningitis

190
Q

What is the principle of the most commonly used test to detect B-lactamase production?

A

Chromogenic cephalosporin nitrocefin

191
Q

A microbiology technologist is performing a B-lactamase test on a staphylcoccus isolated from a hospitalized patient. The test was negative, so the technologies reported out in vitro antimicrobial susceptibility tests results for B-lactam antibiotic. After 2 days, the patient was not improving and the physician changed the patients antibiotic to an Aminoglycoside. The patient showed improvement immediately. Why was the B-lactamase test on the staphylococci negative when the organism produced B-lactamase?

A

Staphylococci must be exposed to the B-lactam agent before it will produce a positive test results

192
Q

Quality control of antimicrobial susceptibility tests involves

A

Testing standard reference strains that have defined antimicrobial susceptibility (or resistance) to the drugs tested

193
Q

How should quality control testing occur?

A

Quality control testing should be included in all the patients tested and treated like a patient specimen

194
Q

What is a mechanism for ensuring the testing personnel are proficient in their tasks?

A

All of the above
*supervisory review of reported results
*self-assessment checklists
*periodic competency testing through proficiency surveys

195
Q

What is the most widely used supplementary quality control measure for antimicrobial susceptibility testing?

A

Use of antibiograms to verify results generated on patient isolates

196
Q

All of the following steps are taken to verify the results from an atypical antibiogram, except

A

Calling around to other hospitals to see if they are encountering the same organism with the same antibiogram

197
Q

What is generated by analysis of individual susceptibility results on isolates from a particular institution in a defined period and represents the percentage of isolates of a given species that is susceptible to the antimicrobial agents commonly tested against the species?

A

Cumulative antibiogram

198
Q

Advantages of the commercial microdilution susceptibility test methods include all the following except

A

More accurate results than manual methods

199
Q

A drug will generally inhibit multiplication of bacteria so that the patients immune defense mechanisms are no longer overwhelmed when

A

The drug concentration exceeds the MIC for the microbe

200
Q

The minimum bactericidal concentration (MBC) test differs from the MIC test because the MIC test gives the concentration needed at the site of infection to Inhibit bacterial multiplications whereas the MBC gives

A

The amount of antimicrobial that must be achieved at the infection site to kill the organism

201
Q

Goals of combination antimicrobial therapy include all of the following except

A

Ensure that at least one antimicrobial will obtain the MBC at the infection site

202
Q

A combination of antimicrobias is said to show synergism if

A

It’s antibacterial activity is significantly greater than that of the single agents

203
Q

When the activity of the combination of antimicrobial agents is less than that of the single agents, we say the agents are

A

Antagonistic

204
Q

All of the following techniques are used to measure the amount of antimicrobial agent in the serum except

A

Bioluminescence assays

205
Q

Staphylococci are catalase-positive, gram-positive cocci that resemble other bacteria and are members of this family

A

Staphylococcaceae

206
Q

All of the following staphylococci are coagulate-positive, except

A

S. Saprophyticus

207
Q

The two species of coagulate-negative staphylococci most often isolated in clinical laboratories are

A

S. Epidermidis and S. Saprophyticus

208
Q

All of the following virulence factors are associated with staphylococcus aureus except

A

Endotoxins

209
Q

What are the staphylococcal products that cause diarrhea and vomiting in humans?

A

Enterotoxins

210
Q

Staphylococcal enterotoxin B is linked to

A

Staphylococcal psuedomembranous enterocolitis

211
Q

What is the mechanism by which toxic shock syndrome toxin-1 (TSST-1) causes TSS?

A

The toxin is a superantigen that stimulates T-cell proliferation with production of large amounts of cytokines

212
Q

What are the effects of the alpha-hemolysin produced by staphylococcus aureus?

A

It lyses RBCs, damage platelets and macrophages and can cause severe tissue damage

213
Q

What are the effects of the a-hemolysin produced by staphylococcus aureus?

A

It acts on sphingomyelin in the plasma membrane of RBCs

214
Q

What are the effects of the Panton-Valentine toxin produced by staphylococcus aureus?

A

It kills leukocytes

215
Q

All of the following enzymes are produced by staphylococci, except

A

Amylase

216
Q

Why do staphylococci spread so easily when infecting the skin?

A

They produce hyaluronidase, which hydrolyzes hyaluronic acid present in the intracellular ground substance that makes up connective tissue

217
Q

What is the function of protein A in the cell wall of staphylococcus aureus?

A

To bind IgG and prevent phagocytosis

218
Q

The primary reservoir for staphylococci is

A

Nares

219
Q

The development of staphylococcal infection is determined by

A

All of the above
* virulence of the strain
*sizes of the inoculum
*status of the host’s immune system

220
Q

Staphylococci resist the action of inflammatory cells by the production of toxins and enzymes, thereby establishing

A

A focal lesion

221
Q

Infection caused by staphylcoccus aureus are suppurative, meaning

A

The infection is filled with pus and necrotic tissues

222
Q

This disease is an extensive exfoliative dermatitis caused by staphylococcal exfoliative toxin

A

RItter’s disease

223
Q

This is rare but potentially fatal multisystem disease characterized by high fever, hypotension, and shock, and it is associated with highly absorbent tampons

A

TSS

224
Q

Staphylococcus aureus food poisoning is most commonly caused by these two enterotoxins

A

A and D

225
Q

This infection occurs secondary to influenza A virus, has a high mortality rate, and occurs among the infants and immunocompromised patients

A

Staphylococcal pneumonia

226
Q

Infection by this organism are predeominately hospital acquired. And some predisposing factors include catheterization, medical implantation, and immunosuppressive therapy

A

S. Epidermidis

227
Q

This staphylococcal species is associated with UTI in young, sexually active females

A

S. Saprophyticus

228
Q

Colony characteristics for staphylococcus aureus on blood agar after 18-24 hours incubation at 35 C include all the following except

A

Swarming

229
Q

This staphylococcus products wide zones of beta hemolysis on 5% sheep blood agar

A

S. Aureus

230
Q

All of the following is used to describe the colony morphology of staphylococcus Epidermidis, except

A

Beta-hemolytic

231
Q

The presence of mecA indicates

A

Resistance to methicillin

232
Q

How is staphylococcus Saprophyticus presumptively identified?

A

Novobiocin susceptibility

233
Q

What antimicrobial agent is used for detection of methicillin resistance ?

A

Oxacillin

234
Q

Automated antimicrobial to susceptibility testing methods are not reliable in detecting staphylococci resistant to this agent

A

Vancomycin

235
Q

A 20 year old woman goes to her physician complaining of burning upon urination, frequency and general malaise. Her physician orders a urine culture, which grew 25,000 colony-forming units (CFU)/mL of a catalase-positive, coagulate-negative, novobiocin-resistant gram-positive occurs. What is the most likely pathogen?

A

S. Saprophyticus

236
Q

A young man goes to his physican complaining of large, raised, suppurative abscesses on his neck. The man denies having a fever or the chills. What is the name of the lesions on his neck, and what organism causes this type of lesions?

A

S. Aureus and furuncles

237
Q

a young, healthy woman was rushed to the hospital with a high fever, hypotension and shock. She has not been feeling well that day, but her conditions progressively worsened throughout the day. She was feeling fine until a couple of days after she started menstruating. What condition could this woman be exhibiting?

A

TSS

238
Q

Later in the evening, after attending a family reunion, several family members went to the emergency department after experiencing nausea, vomiting, abdominal pain, and severe cramping. The menu included fried chicken, hot dogs, hamburgers, potato salad, deviled eggs, eclairs, and explanation for these symptoms?

A

Staphylococcal food poisoning

239
Q

What is the most common causative agent of pyoderma?

A

Staphylococcus aureus

240
Q

What test differentiates staphylococci from streptococci?

A

Catalase

241
Q

The atmospheric conditions best suited to grow steptococci and enterococci are

A

Oxygen-free atmosphere

242
Q

Which of the following is found in the cell wall made of streptococci and enterococci?

A

Teichoic acid and Peptidoglycan

243
Q

Common schemes to classify streptococci include all the following except

A

Flagellar antigens

244
Q

Physiologic classification of streptococci divide the species into all the following groups, except

A

Beta-hemolytic streptococci

245
Q

Which of the following test can be used to presumptively identify streptococcus pyogenes?

A

Bacitracin

246
Q

Which of the following test can be used to identify group B streptococci?

A

CAMP

247
Q

What test can be used to differentiate streptococcus from other B-hemolytic streptococci?

A

Hippurate hydrolysis

248
Q

What test presumptively differentiates B-hemolytic group A streptococci and non hemolytic group D enterococci from other streptococcal species?

A

PYR

249
Q

Which two tests are often used in the ID of the non-hemolytic, catalase-negative, gram-positive cocci?

A

Bile esculin and salt tolerance

250
Q

What test is used for the presumptive identification of streptococcus pneumonia?

A

Optochin

251
Q

Most physicians offices use a rapid throat swab method to identify streptococcus pyogenes infections in children. If the test is positive, the physician treats the patient. What should happen if the test is negative?

A

The physician should perform a throat culture

252
Q

Which of the following is the drug of choice in treating most streptococcal infections. However, penicillin is the drug of choice in treating and streptococcal infections?

A

Penicillin

253
Q

What is the cellular structure that streptococcus pyogenes relies primarily on for its virulence?

A

M proteins

254
Q

All of the following are virulence factors associated with group A streptococcus, except

A

Enterotoxins

255
Q

What is the hemolysin responsible for hemolysis on SBA by Group A streptococci incubated anaerobically?

A

Streptolysin O

256
Q

What causes the red spreading rash in scarlet fever?

A

Streptococcal pyrogenic exotoxins

257
Q

Streptokinase is an enzyme produced by Group A streptococci that

A

Lyses fibrin clot

258
Q

What is the most common disease caused by streptococci?

A

Pharyngitis

259
Q

Skin infections of pyoderma caused by Group A streptococci results in all the following syndromes, except?

A

Bullous impetigo

260
Q

What disease is produced by group A streptococci that are characterized by a rapidly progressing inflammation and necrosis of the skin, subcutaneous fat, and fascia?

A

Necrotizing fasciitis

261
Q

Two serious complications of an infection with group A streptococci are

A

Acute glomerulonephritis and rheumatic fever

262
Q

What is the drug of choice to treat group A streptococci when the patent cannot tolerate penicillin?

A

Erthyromyocin

263
Q

What organism forms small, transparent colonies surrounded by a wide zone of B-hemolysis on SBA?

A

Streptococcus pyogenes

264
Q

Streptococcus agalactiae is a significant cause of

A

Invasive disease of the newborn

265
Q

What organism on SBA has grayish white colonies surrounded by a small zone of B-hemolysis?

A

Streptococcus agalactiae

266
Q

What are two tests presumptively used to identify Group B streptococci?

A

Hippurate hydrolysis and CAMP

267
Q

What two tests are presumptively used to identify enterococcus?

A

Bile esculin and 6.5% NaCl broth

268
Q

What is VRE?

A

Vancomycin-resistant enterococcus

269
Q

The major virulence factor for streptococcus pneumonia is

A

Capsular polysaccharide

270
Q

Streptococcus pneumoniae causes all the following infections, except

A

Pharyngitis

271
Q

A 57-year old male presents to the emergency department with a fever, productive cough, and complaining of chest pain. A STAT gram stain reveals gram-positive oval-shaped cocci in pairs. You should suspect

A

Streptococcus pneumonia

272
Q

Why do streptococcus pneumonia colonies on SBA sometimes appear like a coin—raised edges and a depressed center?

A

The older growth at the center is killed due to autolysis

273
Q

Where are the viridians strepococci constituents of the normal microbiota?

A

All of the above
*upper respiratory tract
*female genital tract
*GI tract

274
Q

Streptococcus-like organisms that resemble enterococci and viridans streptococci include all the following except

A

Moraxella

275
Q

A young girl goes to her physicians office with a fever, headache, and sore throat. The mother states the girl has a fever of 38.8 C (102 F) what test should be physician order?

A

Throat culture

276
Q

A patient comes to the emergency department with a productive cough, shortness of breath, and 102 F fever. The patient is diagnosed with pneumonia. What organism commonly encountered in the microbiology laboratory can cause this disease?

A

Streptococcus pneumonia

277
Q

A microbiologist is reading a sputum culture on the bench. There is growth on the BAP and CHOC plate, but no growth on the MAC plate. The colonies growing on the BAP have discolored the media to a green color around and under the colonies. What organism could this be?

A

Streptococcus pneumonia

278
Q

A microbiologist is reading a sputum culture on the bench. There is growth on the SBA and chocolate (CHOC) plates, but no growth on the MacConkey (MAC) plate. The colonies growing on the SBA have produced a wide, deep, clear zone of B-hemolysis around and under the colonies. What organism could this be?

A

Streptococcus pyogenes

279
Q

A microbiologist is reading a vaginal culture on the bench. There is growth on the SBA and CHOC plates but no growth on the MAC plate. The colonies growing on the SBA have produced a narrow, diffuse zone of B-hemolysis around and under the colonies. What organism could this be?

A

Streptococcus agalactiae

MLT Microbiology (9 decks)

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