Solutions manual to microbiology fundamentals a clinical approach 2nd edition cowan bunn

Solutions Manual to Microbiology Fundamentals A Clinical Approach 2nd Edition Cowan Bunn Instructor Solutions Manual, Supplemental Case Studies Answer Key , Answers to Chapter 2 Visual

Solutions Manual to Microbiology Fundamentals A Clinical Approach 2nd Edition Cowan Bunn

Instructor Solutions Manual, Supplemental Case Studies Answer Key , Answers to

Chapter 2 Visual Connections Answer

In using the quadrant streak plate method to isolate bacteria from a very dilute broth culture, one would expect to see isolated colonies in quadrant 3, since a regular culture will show isolation in quadrant 4 A very dilute broth would show isolation sooner Extremely dilute cultures may even form isolated colonies

in quadrant 2

Chapter 2 Critical Thinking Answers

1 Identification of a microbial agent is the final “I” of the five I’s of microbiology Thus, to

identify the possible pathogen causing the patient’s skin lesion, it is necessary to work through the stages leading to identification First, a sample is obtained from the patient’s wound, using a sterile swab Once a sample is obtained, the first of the five I’s, inoculation, is carried out Inoculation occurs when the sample is placed into a container of sterile medium to encourage the growth of microorganisms

The inoculated medium is then incubated, which is the placement of the medium in a temperature

Chapter 2 Tools of the Laboratory: The Methods for Studying Microorganisms

macroscopically For example, on solid media, the appearance of bacteria and fungi is in the form

of colonies

Once growth is observed, the next stage is to isolate the organism of interest Samples obtained from a patient are often mixed samples containing many organisms In this case, you are most interested in the organism causing the skin lesion Isolation of an organism can involve several techniques and tools Techniques include the streak plate, loop dilution, and spread plate

Selective media can also be used to encourage growth of the organism of interest

As the organism of interest is isolated from others in the original sample, the final two “I’s”, inspection and identification, can be instituted Inspection can involve a variety of means Examining the culture with one’s own eyes is often the first step Microscopic examination can

be utilized, as can biochemical tests Immunological and genetic protocols can also be used to aid

in the specific identification of microorganisms

2 a Blood agar can help identify Streptococcus species based on hemolytic abilities

b MacConkey agar could be used to isolate and identify pathogens present in a urine sample, as

the agar differentiates between lactose-fermenters such as E coli and other bacteria

c Enteroccoccus faecalis broth can be used to isolate enteric organisms

d Transport media is required to maintain the nasal swab specimen for further analysis

3 a Figure 2.9 shows methods for isolating organisms, through use of the streak plate, loop

dilution, or spread plate methods These methods are successful in separating samples so that individual colonies can be identified, and thus can also be used to determine the total number of cells present in a patient’s sample A viable plate count uses loop dilutions combined with spread plate or pour plate methods to estimate the number of viable cells in a sample

b The fact that growth was noticed in the first quadrant of the streak plate indicates that the bacterial sample is capable of growing on this medium, and that bacterial organisms were present

in the original sample

The fact that growth was not observed in the remaining quadrants may have resulted from several possible errors First, an inadequate amount of the sample from quadrant 1 may have been

streaked into quadrant 2 and beyond, preventing observable amounts of growth from appearing

If an inoculating loop was used to streak the sample into other quadrants and the loop was not cooled sufficiently between streaks, the bacterial sample may have been killed by the heated loop Finally, the preparer of the streak plate may have simply overlooked the completion of the

procedure and did not streak the later quadrants

4 a The use of a stain such as Lactophenaol cotton blue enhances the contrast of a specimen to be viewed under a microscope Unstained cells can be indistinct when viewed under a microscope,

no matter how strong the magnification or powerful the resolution Staining a sample enables the development of a contrast between the sample and the background, making for easier

visualization

b Viruses are too small to be observed with light microscopy Thus, other forms of microscopy, such as fluorescence microscopy, must be utilized In fluorescent microscopy, the viral particles are made observable through the use of fluorescent stains

The visualization of multiple organisms within a specimen can be accomplished using light microscopy Bacteria and fungi are large enough to be observed using this technique If viral particles are to be observed in the sample, other forms of microscopy would need to be used Depending on the specimen, dark field microscopy may be used, as it permits rapid recognition of the cell’s structure

To view cellular structures such as organelles, phase contrast microscopy is one technique that can be utilized As light passes through cellular structures of differing densities, the light is altered and this pattern can be used to produce an image An electron microscope can also be used to view organelles, given the size of these structures

5 The Gram stain is a differential stain This staining procedure uses two different dye colors to differentiate between gram-positive and gram-negative bacteria When a Gram stain results in both pink and purple cells, the results indicate a mixed sample of both positive and

gram-In order to identify the pathogen further, selective and differential media may be utilized

Selective media, such as MacConkey agar, encourage the growth of gram-negative bacteria, while mannitol salt agar selects for certain gram-positive organisms The resulting growth on selective media can help the clinician begin to determine the possible pathogen Differential media also helps clinicians identify organisms in mixed samples For example, blood agar helps

to identify certain bacteria based on the hemolytic activity Additional tools for identification, such as biochemical tests and genetic analysis, can also be employed

Therefore, although the original Gram stain results showed a mixed culture of gram-positive and gram-negative bacteria, further tools are available to help identify the pathogen

Chapter 2 Instructor Manual

Many microorganisms can be cultured on artificial media, but some, such as viruses, can only be

cultured in living tissues or in cells Artificial media are classified by their physical state (liquid, semisolid, liquefiable solid, or nonliquefiable solid); by their chemical composition (defined or complex); or by their function (enriched, selective, differential, transport, and so on)

Microbiologists use five basic techniques to manipulate, grow, examine, and characterize

microorganisms in the laboratory These techniques are called the “Five I’s”: inoculation,

incubation, isolation, inspection, and identification The steps can be viewed as summaries of the laboratory procedures used in microbiology

Inoculation involves the introduction of a sample into sterile medium Following inoculation,

cultures are incubated at a specified temperature to encourage growth Isolated colonies that

originate from single cells are composed of large numbers of cells piled up together A culture

may be pure, containing only one species or type of microorganism; mixed, containing two or more known species; or contaminated, containing both known and unknown (unwanted)

microorganisms

During inspection, the cultures are examined and evaluated macroscopically and

microscopically Microorganisms are identified in terms of their macroscopic or immunologic

morphology, their microscopic morphology, their biochemical reactions, and their genetic

characteristics

Magnification, resolving power, and contrast all influence the clarity of specimens viewed through the optical microscope The maximum resolving power of the optical microscope is 200

nm, or 0.2 μm This resolution is sufficient to see the internal structures of eukaryotes and the morphology of most bacteria

Of the six types of optical microscopes, four use visible light for illumination: bright-field, dark-field, phase-contrast, and interference microscopes The fluorescence microscope uses UV light for illumination The confocal microscope can use UV light or visible light reflected from

specimens Electron microscopes (EM) use electrons, not light waves, as an illumination source

to provide high magnification (5,000× to1,000,000×) and high resolution (0.5 nm) Specimens viewed through optical microscopes can be either alive

or dead, depending on the type of specimen preparation, but all EM specimens must be dead because they are viewed in a vacuum

Staining of sample is an important technique in microbiology Stains increase the contrast of specimens and they can be designed to differentiate cell shape, structure, and biochemical

composition of the specimens being viewed The Gram stain is an immensely useful differential stain that divides bacteria into two main groups, gram-positive and gram-negative Some

bacteria, such as those that cause tuberculosis, do not fall in either of these categories The bacteria can be identified with other staining procedures, such as acid-fast staining

Pre-Class Ideas for Chapter 2

Below are suggested activities to assign before covering the material of Chapter Two in class The activities are designed to provide opportunities for students to engage with the topics prior

to class Some activities also have students preparing materials that will enable students to teach one another in class

1 Assign one of the 5 I’s to groups of students Have the student groups teach the class about their assigned 5 I

2 Provide students a list of different media (TSA, blood agar, mannitol salt, MacConkey, urea broth, TSA broth, birdseed, tomato juice agar, chocolate, etc.) Have students create

a chart and for each medium address the following: the physical state, whether

chemically-defined or complex, and the functional type

3 Using simple drawings (in color), students show how organisms appear on the following: general purpose media, selective media, differential media, streak plate, loop dilution, spread plate

4 Assign student groups to demonstrate to the class using appropriate materials: inoculation

of a plate, inoculation of a broth tube, streak plate, loop dilution plate, spread plate, smearing a sample, fixing a sample, hanging drop

5 Assign the following figures to student(s) and have them prepare an explanation to teach the class: Figure 2.2, Figure 2.3, Figure 2.5, Figure 2.6, Figure 2.7, and Figure 2.9

6 In simple drawings (in color), have students create examples of mixed cultures, pure culture, positive stain, negative stain, simple stain, differential stain, endospore stain, capsule stain

7 Have students write descriptions for Figures 2.17, 2.18, 2.19 in their own words

8 Students label a diagram of a microscope

9 Using their own words and simple drawings, students demonstrate an understanding of magnification, resolution, and contrast

10 In groups, students create an activity to teach the metric system to classmates

Activities Associated with Learning Objectives for Chapter 2

Lecture Suggestions and Guidelines for Section 2.1

1 The 5 I’s are critical to microbiology and students will encounter these topics repeatedly throughout the semester It is helpful to relate each of the 5 I’s to “real world” scenarios

2 The classification of media can be confusing to students at first Students need to

understand that media is classified according to its physical state, chemical composition, and function

3 Introduction of specific media and their role in a microbiology laboratory is aided by presenting the material in a way that relates it to infectious diseases

In-Class Activities for Section 2.1

1 In a role play situation, have students walk through the 5 I’s in the following scenario: a patient presents at doctor’s office with severe cough, fever, and sore throat

2 Provide pictures of cultures growing on identified media Have students use class time to research growth appearances on a given medium type and give a guess of the type of organisms inoculated on the plates

3 Bring in examples of different forms of media and allow students to discuss the

classification of the media and the purpose of the media

4 Bringing in appropriate materials, have students demonstrate the following techniques to the class: inoculation of a plate, inoculation of a broth tube, streak plate, loop dilution plate, spread plate, smearing a sample, fixing a sample, hanging drop

Additional Research Issues for Section 2.1

1 Have students research situations in which an infectious disease was, at first, incorrectly identified What issues may have contributed to the misidentification?

2 Ask students to research a current infectious disease scenario in the news

 Have the students examine how the 5 I’s of microbiology are being applied in this situation

 Ask students to research which of the 5 I’s may be the most difficult to complete given the situation Have students provide an explanation for their reasoning

Critical Thinking Issues for Section 2.1

1 Can the 5 I’s of microbiology be completed for every disease?

2 Where may potential mistakes be made in regards to the incorporation of the

5 I’s? How may these mistakes affect our understanding of a disease? What can be done

to reduce these errors?

3 Not all microorganisms can be grown on media What effect does this fact have on treatment and prevention of these infectious diseases?

Lecture Suggestions and Guidelines for Section 2.2

1 Students will likely have been taught the metric system before, although some may continue struggle with the concepts

2 Emphasis on the three basic principles of microscopy will help students understand the different forms of microscopy

3 Staining procedures play a large role in microbiology It is important that students can confidently engage with the terminology associated with staining, in order that the student can apply this knowledge to specific staining procedures and the purpose of such procedures

In-Class Activities for Section 2.2

1 Hands-on activities for the metric system should be incorporated These may include student presentations and/or the use of examples of metric devices to measure, weigh, and determine volume

2 Examples showing resolution, contrast, and magnification in regards to microscopy should be incorporated into the classroom These may include drawings created by

3 Have a microscope (or several) available in the classroom so students can see the

microscope components rather than looking at an image of a microscope

4 Provide a list of different items (human cells, bacteria, protozoa, organelles, viral

particles) and have students discuss which form of microscopy would be best suited for viewing these items

5 Create a discussion chart that outlines how the different forms of microscopy are used to diagnosis infectious diseases

6 Have on hand items typically used in microbial staining procedures so students become familiar with these materials

Additional Research Issues for Section 2.2

1 Research countries in the world in regards to which use the metric system and which do not

2 Research current developments in microscopy Predict how these developments may be applied to microbiology, specifically infectious diseases

3 Viable but nonculturable (VBNC) bacteria have been discovered in human tissue What are these bacteria and what role may they play in disease and health?

Critical Thinking Issues for Section 2.2

1 The Gram stain was developed in 1884 Why is this procedure still used today? What (if any) changes have been made to the procedure in modern times?

2 How would the identification and treatment of infectious agents change if all bacteria truly did look and act the “same”?

Answer Key to Supplemental Case Studies

Case Study 1 / Answers

1 b

2 b

3 d

4 b

Case Study 2 / Answers

1 Lyme Disease

2 Working in the Wisconsin woods, the bull’s eye rash, fever, cardiac changes, joint pain

3 Antibiotic therapy with Ampicillin and ceftriaxone or erythromycin; monitor for long-term cardiac and joint problems and treat symptomatically

Case Study 3 / Answers

1 streptococcal pharyngitis Classical symptoms, pus on tonsil and pharynx, fever

2 culture and sensitivity from throat swab, rapid strep test

3 penicillin or erythromycin for 10 days; treatment is important to prevent scarlet fever and

rheumatic fever with their associated heart problems and kidney problems that could occur later

in life

4 the clinical picture, clear lungs, pus on tonsils and pharynx, fever and history

Case Study 4 / Answers

1 adenoviral pharyngitis, croup

2 No, the Strep test was negative and the overall picture indicates a viral infection

3 viral disease; little or no pus on pharynx, good response to warm vapor to clear congestion

4 more vapor treatment, decongestant, and analgesic; antibiotics should be reserved unless Strep of Hib shows on culture

Case Study 5 / Answers

1 influenza; fever, moderate pain in lungs (chest), headache, no pneumonia, tight productive cough,

no evidence of Strep

2 bacterial pneumonia may follow severe influenza

3 fluids, bed rest, fever-reducing medicine

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