Case Studies in Clinical Microbiology (Online CE Course)

(based on 1,428 customer ratings)

Authors: Elmer W. Koneman, MD; Christie A. Grueser, MSS, MT
Reviewer: Julie Ann West, PhD, MLS(ASCP)CM, SM(ASCP)CM

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This recently revised and updated course (2023) provides interactive case studies which cover pertinent current topics in clinical microbiology. Numerous images enhance the text and interactive questions help the student master the material.

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Continuing Education Credits

P.A.C.E.® Contact Hours (acceptable for AMT, ASCP, and state recertification): 3 hour(s)
Approved through 1/31/2025
Florida Board of Clinical Laboratory Personnel Credit Hours - General (Microbiology/Mycology/Parasitology): 3 hour(s)
Approved through 1/31/2025


  • Correlate presenting clinical signs and symptoms with the organism identifications for the cases being presented.
  • Outline the presumptive and definitive characteristics for the laboratory identification of the bacterial species being presented.
  • Discuss the diagnostic and therapeutic implications of making a correct organism identification.

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(based on 1,428 customer ratings)

Course Outline

Click on the links below to preview selected pages from this course.
  • Introduction
      • Course Organization
  • Acute Urethral Discharge
      • Case Study: Acute Urethral DischargeA 25-year-old female presents to the emergency room with an acute urethral discharge of two days duration.The imag...
      • Neisseria gonorrhoeae
      • Neiserria gonorrhoeae is the most common cause of septic arthritis among sexually active adults in the United States.
      • Presumptive Laboratory Identification: Neisseria gonorrhoeae
      • Additional Testing Information
      • The positive oxidase reaction as shown in the image (yellow arrow) rules out which of the following two look-alike organisms of N. gonorrhoeae? (Choos...
      • Definitive Laboratory Identification: Neisseria gonorrhoeae
      • The carbohydrate utilization reaction seen in the image will ALONE provide the necessary testing required for a definitive identification of N. gonorr...
  • Acute Onset Pneumonia
      • Case Study: Acute Onset PneumoniaA 70-year-old transient with a productive cough, pleuritic chest pain radiating to the mid back, fever, and chills wa...
      • Case Study, Part Two: Acute Onset PneumoniaA 70-year-old transient with a productive cough, pleuritic chest pain radiating to the mid back, fever, and...
      • Streptococcus pneumoniae
      • Streptococcus pnemoniae is the most common bacterial cause of community-acquired pneumonia.
      • Pneumococcal vaccine is particularly effective in children less than two years of age.
      • Laboratory Identification: Streptococcus pneumoniae
      • Case Study, Part Three: Acute Onset PneumoniaA 70-year-old transient with a productive cough, pleuritic chest pain radiating to the mid back, fever, a...
      • A drop of 10% deoxycholate was placed on an area of growth as shown in the image. This test is often used to differentiate S. pneumoniae from viridans...
      • Susceptibility Testing: Streptococcus pneumoniae
      • The zone of inhibition around the disk shown in the image has been measured at 23 mm. Based on this result, you should:
      • For S. pneumoniae isolates recovered from cerebrospinal fluid (CSF), the oxacillin screen test alone is NOT sufficient for determining susceptibility ...
      • Minimum inhibitory concentration (MIC) susceptibility tests should be performed against other beta lactam antibiotics on important S. pneumoniae isola...
      • Pneumococcal Resistance
  • Gram-Negative Sepsis
      • Case Study: Gram-Negative Sepsis A 67-year-old man is admitted to the hospital with a cough, right lower chest pain accentuated by deep breathing, and...
      • The reactions seen in the portion of the biochemical strip shown in the image effectively rule out Escherichia coli.
      • Extended-Spectrum Beta-Lactamases (ESBLs) Review
      • Isolates of Escherichia coli, Klebsiella pneumoniae, K. oxytoca and clinically significant isolates of Proteus mirabilis may possess extended-spectrum...
      • Extended-Spectrum Beta-Lactamases (ESBLs)
      • Extended-Spectrum Beta-Lactamase (ESBL) Screening by Disk Diffusion and Broth Microdilution
      • Extended-Spectrum Beta-Lactamase (ESBL) Phenotypic Confirmation by Disk Diffusion and Broth Microdilution
      • Extended-Spectrum Beta-Lactamase (ESBL) Activity
      • Carbapenemases in Enterobacterales
      • Which of the following antibiotics is preferred as the most sensitive indicator when detecting carbapenem resistance?
  • Recurrent Urinary Tract Infection (UTI)
      • Case Study: Recurrent Urinary Tract Infection (UTI) A 72-year-old woman had a history of recurrent UTIs over the past several months, for which she ha...
      • Pyrrolidonyl Arylamidase (PYR) Differential
      • The spot test that is helpful in separating Enterococcus species (positive as shown in the image) from the viridans streptococci and S. pneumoniae (bo...
      • Enterococcus Identification
      • Enterococcus faecium Identification
      • Vancomycin Resistance
      • In this image is a quadrant plate containing brain heart infusion (BHI) agar supplemented with 6 μg/mL of vancomycin. The right upper quadrant wa...
      • What is the most important modifiable risk factor for enteric colonization with vancomycin-resistant Enterococcus faecium (VREF)?
  • Acute Enteritis with Sepsis
      • Case Study: Acute Enteritis with Sepsis A 63-year-old man was seen in the emergency room with complaints of sudden onset of fever, chills, and abdomin...
      • The Gram stain shown in the image was prepared from a positive anaerobic blood culture bottle after 36 hours incubation. Based on the morphology of th...
      • Need for Identification and Further Investigation
      • Colony Morphology
      • Use of Quad Plates for Identification
      • Clostridium septicum Micromethod Panel Test
      • It is important to establish a species identification of C. septicum in blood culture isolates because of its close association with carcinoma of the ...
      • Match the frequently associated conditions with their corresponding anaerobes.
      • Each of the following statements is true concerning Clostridium septicum infections EXCEPT:
  • Post Traumatic Wound Infection
      • Case Study: Post Traumatic Wound InfectionAn 18-year-old female incurred a deep penetrating injury of the dorsum of her right foot when a kitchen knif...
      • Staph on Blood Agar
      • The organisms shown in the image were observed in a smear prepared from the colony shown previous to this page. Which of the following tests will help...
      • The tube coagulase test, shown in the image (upper tube positive), should be performed on all S. aureus-suspicious isolates giving a negative slide co...
      • Staphylococcus aureus Mannitol
      • Methicillin (oxacillin)-resistant Staphylococcus aureus: Oxacillin Salt Agar
      • Methicillin (oxacillin)-resistant Staphylococcus Disk Test
      • Cefoxitin Surrogate Test, PBP2a, and Molecular Assays
      • Predisposing Factors to MRSA Infection and Decreasing the Risk of Colonization
      • Factors predisposing infections with methicillin (oxacillin) resistant Staphylococcus aureus (MRSA) include:
      • Decreasing the risk of staphylococcal colonization of indwelling catheters in the future may involve:
      • Patients with MRSA infections have uniformly poorer outcomes than those infected with sensitive strains.
      • Exfoliative Toxins Causing Staphylococcal Scalded-Skin Syndrome (SSSS)
      • The staphylococcal toxins causing the scalded skin syndrome (SSSS) act specifically at the site which involves the following layers of skin:
      • Tests that might help assess methicillin (oxacillin) resistance mechanisms in S. aureus include:
  • Splenic Abscess
      • Case Study: Spleen SpecimenA 23-year-old man had complained of right lower quadrant abdominal pain for approximately one week. Initially, the pain was...
      • Most strains of S. anginosus group (S. milleri group) carry the F antigen (see image of Lancefield typing test). Rare strains that carry the group A a...
      • S. anginosus Group (S. milleri Group): CO2
      • S. anginosus Group (S. milleri Group): Biochemicals
      • Streptococcus anginosus Group (S. milleri Group)
      • Most infections caused by S. anginosus group (S. milleri group) can be effectively treated with penicillin or a first generation cephalosporin.
      • Epidural and subdural abscesses are clinical manifestations uncommon for S. anginosus group (S. milleri group).
      • Which is a clinical condition often associated with Streptococcus anginosus group (S. milleri group)?
  • Cellulitis
      • Case Study: CellulitisA 40-year-old woman with a long history of diabetes mellitus developed swelling and erythema of the left lower leg following sup...
      • Case Study: Cellulitis (continued)Beta hemolytic colonies grew from the blood culture bottle after 18 hours of incubation (see image). Which of the fo...
      • Group A Strep A Disk/SXT
      • Thus, in follow-up to the previous discussion, the reaction shown in the image establishes the identification of a group A, beta hemolytic Streptococc...
      • Invasive Streptococcal Infection
      • Major Factors Related to Strong Resistance of Certain Strains of Group A Streptococci to Phagocytosis
      • What is a major complication of toxic shock syndrome related to group A streptococci, leading to 50% mortality?
      • What factors are related to the strong resistance of certain strains of group A streptococci to phagocytosis?
  • Neonatal Meningitis
      • Case Study: Neonatal Meningitis
      • Case Study: Neonatal Meningitis (continued) A Brown - Brenn modified Gram stain was performed on one of the tissue biopsy specimens. Organisms were se...
      • Case Study: Neonatal Meningitis (continued) The top image of the surface of blood agar after 24 hours of incubation at 35° C in 10% CO2, on which...
      • What test(s) which may be performed to establish a presumptive differential identification between group B streptococci and L. monocytogenes?
      • Listeria Gram Stain
      • Shown in the image are three tubes: (1) motility agar (note subsurface flare shown by arrows); (2) esculin hydrolysis (+), and (3) VP (+). The reactio...
      • Listeria Motility
      • Listeria monocytogenes
      • Listeria monocytogenes Virulence Factors
      • Listeria monocytogenes: Virulence Factors (continued)
      • Which of the following is NOT related to the virulence of Listeria monocytogenes?
      • Which of the following factors has NOT led to the current increase in incidence of listeriosis?
      • A characteristic of the virulence of L. monocytogenes is its unique ability to invade peripheral nerves and rapidly enter into the brain.
  • Cellulitis of the Arm
      • Cellulitis Lesion
      • Eikenella on BAP
      • Eikenella - Catalase & Oxidase
      • Eikenella Biochemicals
      • A bacterial isolate that produces pitting of the agar and has a bleach-like odor is probably E. corrodens. What are the closely related species that m...
      • Which of the following result in most Eikenella cellulitis infections?
      • In view of the feedback to the previous question, what is the most likely reason that the clinical correlation does not seem to fit in this case?
      • Eikenella corrodens Infections and Patients with Insulin-Dependent Diabetes Mellitus (IDDM)
      • Bite Wounds
      • Human bite wound infections are categorically more severe and more often lead to complications than infected bites from other animals.
      • In patients with Insulin-Dependent Diabetes Mellitus (IDDM), all of the following situations can be causes of infection with E. corrodens, EXCEPT? (Se...
  • References

Additional Information

General Information: This recently revised and updated course (2023) provides interactive case studies which cover pertinent current topics in clinical microbiology. Numerous images enhance the text and interactive questions help the student master the material.
Level of Instruction: Intermediate
Intended Audience: Medical technologists, and instructors experienced in bacteriology, graduate students in microbiology, clinical pathologists, and infectious disease physicians.
Author information: Elmer W. Koneman, MD, was Professor Emeritus,  Department of Pathology, University of Colorado School of Medicine for many years until his passing in 2020.  Residing in Breckenridge, CO,  Dr. Koneman was a Board Certified Pathologist and author of numerous journal articles and books, including Koneman’s Color Atlas and Textbook of Diagnostic Microbiology,  7th Edition,  2016 (Jones & Bartlett Learning). Koneman was affiliated with the Colorado Association for Clinical Laboratory Education (CACMLE) and with Instructional Design Consultants, specializing in interactive training and distance learning in clinical microbiology. 
Reviewer information: Dr. Julie Ann West is certified by the American Society for Clinical Pathology (ASCP) as a Medical Laboratory Scientist (MLS) and as a Specialist in Microbiology (SM). In addition, Dr. West has earned a PhD in Public Health - (Infectious Disease) Epidemiology - and is Certified in Public Health (CPH) by the National Board of Public Health Examiners. Dr. West is experienced as a Technical Specialist, Safety Officer, Educator, and Lead in the Veterans Administration Healthcare System, and has prior experience as an Administrative Laboratory Director.

How to Subscribe
MLS & MLT Comprehensive CE Package
Includes 173 CE courses, most popular
$95Add to cart
Pick Your Courses
Up to 8 CE hours
$50Add to cart
Individual course$20Add to cart
Need multiple seats for your university or lab? Get a quote
A Disk

Coag Tube

E. coli on MAC

Strep cellulitis skin

Klebsiella BA/Mac Plate.JPG

Enterococcus faecium biochemicals

Neisseria Gram