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Current Topics in Clinical Microbiology

Elmer W. Koneman, MD; Christie A. Grueser MSS, MT

Nine interactive microbiology case studies by Dr. Elmer Koneman, covering practical topics such as ESBL-producing bacterial strains, MRSA, Clostridium septicum enteritis, and many others. Perfect as CE for busy clinical microbiologists.

Continuing Education (CE) Credits

P.A.C.E. Contact Hours: 6.5 hour(s)
Florida CE: General (Microbiology/Mycology/Parasitology): 6 hour(s)

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Current Topics in Clinical Microbiology Objectives

Overall Objective 1: To provide home access to on-line CLINICAL MICROBIOLOGY case studies.
Overall Objective 2: To correlate the CLINICAL histories of select BACTERIAL INFECTIOUS DISEASES with LABORATORY CULTURE results.
Overall Objective 3: To provide home-base, on-line opportunities to acquire continuing education credits.
Learning Objectives: At the completion of this case study review, the student will be able to:
1. Correlate presenting CLINICAL signs and SYMPTOMS with the ORGANISM IDENTIFICATIONS for the cases being presented.
2. Outline the presumptive and definitive characteristics for the LABORATORY IDENTIFICATION of the BACTERIAL species being presented.
3. Discuss the DIAGNOSTIC and therapeutic implications of making a correct ORGANISM IDENTIFICATION.
4. Recommend key current literature citations for each of the INFECTIOUS DISEASES and BACTERIAL species included in the program.

Current Topics in Clinical Microbiology Outline

ACUTE URETHRAL discharge

CLINICAL history

A 25 year-old female presented in the emergency room with an ACUTE URETHRAL discharge of 2 days duration. A smear for GRAM STAIN was obtained (see accompanying image). Many POLYMORPHONUCLEAR LEUKOCYTES and INTRACELLULAR and extracellular GRAM NEGATIVE DIPLOCOCCI were observed. Based on the CLINICAL history and the GRAM STAIN observation, a DIAGNOSIS of GONORRHEA can be made.

Lab ID presumptive

The positive OXIDASE reaction as shown in the photograph (yellow arrow) rules out the following two look-alike ORGANISMS of N. GONORRHOEAE:
The SUPEROXOL Test

Lab ID definitive

The CARBOHYDRATE utilization reaction seen in the QUADFERM sySTEM shown in the picture provides a definitive IDENTIFICATION of N. GONORRHOEAE:

Literature Reviews and Queries

Review 2
ACUTE GONORRHEA is the most common cause of septic ARTHRITIS in patients under 30 years of age.
The recovery of an OXIDASE-POSITIVE, GRAM-NEGATIVE DIPLOCOCCUS that tests DFA-NONREACTIVE should be tested by alternative methods when establishing a fool-proof DIAGNOSIS of GONORRHEA.

ACUTE onset PNEUMONIA

CLINICAL History

ACUTE Onset PNEUMONIA
The GRAM STAIN report to be issued based on the microscopic characteristics seen in the accompanying picture would most correctly be, "many WBC with"..
Based on the GRAM STAIN MORPHOLOGY observed before, the possible presumptive IDENTIFICATIONS might include "GRAM POSITIVE COCCI consistent with...

LABORATORY IDENTIFICATION

The patient was admitted to the HOSPITAL. The SPUTUM specimen was INOCULATED to sheep BLOOD AGAR. Based on the COLONY MORPHOLOGY seen in the accompanying photograph, the most likely IDENTIFICATION is:
The name of the rapid test as illusTRATEd in this photograph, often used to differentiate S. PNEUMONIAE from VIRIDANS STREPTOCOCCI, in which a drop of 10% DEOXYCHOLATE was placed on an area of growth, is:
The zone of inhibition around the disk shown in the photograph has been measured at 23 mm. Based on this result, you should:
The OXACILLIN screen test alone is not sufficient for determining the susceptibility to PENICILLIN for S. PNEUMONIAE isolates recovered from BLOOD and CSF.
MIC SUSCEPTIBILITY TESTS should also be performed against other select beta lactam ANTIBIOTICS on important S. PNEUMONIAE isolates from BLOOD CULTURES and other STERILE BODY fluids.
PNEUMOCOCCAL Resistance

Literature Reviews and Queries

Review 2
STREPTOCOCCUS PNEMONIAE is the most common cause of fatal community-acquired PNEUMONIA.
Middle ear damage in cases of S. PNEUMONIAE INFECTIONS are caused primarily by:
PNEUMOCOCCAL VACCINE is particularly effective in children less than two years of age.

GRAM-NEGATIVE SEPSIS

CLINICAL History

CLINICAL History

LABORATORY IDENTIFICATION

The COLONies shown in the BLOOD AGAR (upper) and MACCONKEY AGAR (lower) biplate are a 24 hour growth from an AEROBIC BLOOD CULTURE BOTTLE that became positive at 12 hours after INOCULATION. The appearance of the COLONies on MACCONKEY AGAR rules out the following two BACTERIAL species:
The reactions seen in the portion of the API STRIP shown in the photograph, effectively rules out ESCHERICHIA COLI.
CLINICAL isolates of ESCHERICHIA COLI and KLEBSIELLA PNEUMONIAE may possess ESBL activity. Therefore, CLINICAL laboratories should be screening all CLINICALly significant isolates of these two species.
ESBL Activity
Extended SPECTRUM Beta LACTAMASES

Literature Reviews and Queries

Review 1
The prevalence of ESBL's may be underestimated because NCCLS has set resistance break-points too low.
The hands of HOSPITAL personnel represents one of the major reservoirs for the persistence and potential spread of ESBL producing strains of KLEBSIELLA PNEUMONIAE in the HOSPITAL ENVIRONMENT.

Recurrent URINARY tract INFECTION

CLINICAL History

CLINICAL History
The BACTERIAL species shown growing on 5% sheep BLOOD AGAR was recovered from the spun SEDIMENT of a midstream URINE specimen after 24 hours INCUBATION at 35C. Each of the following tests would be useful in supporting the presumptive IDENTIFICATION of ENTEROCOCCUS species except:

LABORATORY IDENTIFICATION

PYR DIFFERENTIAL
The spot test that is helpful in separating ENTEROCOCCUS species (positive as shown in the photograph) from the VIRIDANS STREPTOCOCCI and S. PNEUMONIAE (both negative) is:
ENTEROCOCCUS ID
ENTEROCOCCUS FAECIUM ID
VANCOMYCIN Resistance
IllusTRATEd in this photograph is a quadrant plate containing BRAIN HEART infusion AGAR plate supplemented with 6 ug/ml of VANCOMYCIN. The right upper quadrant was INOCULATED with the test strain of ENTEROCOCCUS FAECIUM. The presence of growth in the INOCULATED quadrant indicates resistance to VANCOMYCIN.

Literature Reviews and Queries

Review 1
Review 2
The most important modifiable risk factor for ENTERIC COLONIZATION with VANCOMYCIN-RESISTANT ENTEROCOCCUS FAECIUM is:

ACUTE ENTERITIS with SEPSIS

CLINICAL History

Case History
Gas GANGRENE may be seen in INFECTIONS with all the following CLOSTRIDIA except:

LABORATORY IDENTIFICATION

The GRAM STAIN shown in the photograph was prepared from a positive ANAEROBIC BLOOD CULTURE BOTTLE after 36 hours INCUBATION. Based on the MORPHOLOGY of the BACTERIAL cells (some with spores--blue arrows), the most likely IDENTIFICATION is:
COLONY MORPHOLOGY
CLOSTRIDIUM Quad Plate
CLOSTRIDIUM SEPTICUM RapID ANA
It is important to establish a species IDENTIFICATION of C. SEPTICUM in BLOOD CULTURE isolates because of its close association with CARCINOMA of the COLON.

Literature Reviews and Queries

Review 1
Review 2
Review 3
Match the species of ANAEROBES and frequently associated conditions.
Each of the following statements is true concerning CLOSTRIDIUM SEPTICUM INFECTIONS except:

Post Traumatic Wound INFECTION

CLINICAL History

CLINICAL History
A GRAM STAIN of the SEROUS EXUDATE is shown in the photograph. The appropriate report would read:

LABORATORY IDENTIFICATION

Staph on BA
The BACTERIAL cells shown in the photograph were observed in a smear prepared from the COLONY shown before. Which of the following tests will help to affirm the IDENTIFICATION of STAPHYLOCOCCUS AUREUS?
The tube COAGULASE test, shown in this picture (upper tube positive), should be performed on all S. AUREUS-SUSPICIOUS isolates giving a negative slide COAGULASE reaction.
Staph AUREUS MANNITOL

Testing for METHICILLIN Resistance

MRSA Screen
MRSA Disk Test

Literature Reviews and Queries

Review 1
Review 2
Review 3
Factors predisposing to INFECTIONS with METHICILLIN resistant STAPHYLOCOCCUS AUREUS (MRSA) include:
Decreasing the risk of STAPHYLOCOCCAL COLONIZATION of indwelling CATHETERS in the future may involve:
Patients with INFECTIONS with MRSA have uniformly poorer outcomes than those infected with sensitive strains.
The STAPHYLOCOCCAL TOXINS causing the SCALDED skin SYNDROME (SSSS) have as their site of action in which of the following layers of skin:

SPLENIC ABSCESS

CLINICAL History

Spleen Specimen

LABORATORY IDENTIFICATION

IllusTRATEd in the upper photograph are tiny pinpoint 24-hour COLONies recovered from one of the SPLENIC ABSCESSES. The wide zones of beta HEMOLYSIS are better seen in the close-in view of the 36 hour CULTURE shown in the lower photograph. STREPTOCOCCUS MILLERI (ANGINOSUS) can be suspected if one of the following odors is detected:
Most strains of S. MILLERI (ANGINOSUS) carry the F ANTIGEN (see photograph). Rare strains that carry the group A ANTIGEN can be differentiated from S. PYOGENES by which of the following LABORATORY tests:
S. MILLERI CO2
S. MILLERI BIOCHEMICALS

Literature Reviews and Queries

Review 1
Review 2
Most INFECTIONS caused by S. MILLERI (S. ANGINOSUS) can be effectively treated with PENICILLIN or a first GENEration CEPHALOSPORIN.
The EPIDURAL and SUBDURAL ABSCESSES in the two patients reported by GELFAND, et al, are CLINICAL manifestations uncommon for S. MILLERI.
A CLINICAL condition often associated with STREPTOCOCCUS MILLERI (ANGINOSUS) is:

CELLULITIS

CLINICAL History

CELLULITIS Skin

LABORATORY IDENTIFICATION

The GRAM STAIN prepared from the positive BLOOD CULTURE is shown in the photograph. The appropriate report is:
Beta HEMOLYTIC COLONies grew from the BLOOD CULTURE BOTTLE after 18 hours INCUBATION (see photograph). The following tests would be helpful in making a preliminary IDENTIFICATION:
Group A Strep A Disk/SXT
Thus, in follow-up to the previous discussion, the reaction shown in the photograph establishes the IDENTIFICATION of a group A, beta HEMOLYTIC STREPTOCOCCUS.

Literature Reviews and Queries

Review 1
Review 2
A major complication of TOXIC shock SYNDROME related to group A STREPTOCOCCI, leading to 50% mortality is:
Factors related to the strong resistance of certain strains of group A STREPTOCOCCI to PHAGOCYTOSIS include:

NEONATAL MENINGITIS

CLINICAL History

CLINICAL History
HISTOLOGY of BRAIN BIOPSY
A BROWN AND BRENN GRAM STAIN was performed on one of the tissue BIOPSY specimens. ORGANISMS were seen as shown in the photograph. Based on the history and the appearance of the BACTERIA, the most likely IDENTIFICATION is:

LABORATORY IDENTIFICATION

COLONY MORPHOLOGY
Shown in the photograph is a close-in view of the COLONY growth after 48 hours INCUBATION. Possible presumptive IDENTIFICATIONS suggested by the COLONies observed include:
The test(s) which may be performed to establish a presumptive DIFFERENTIAL IDENTIFICATION between group B STREPTOCOCCI and L. MONOCYTOGENES is/are:
LISTERIA GRAM STAIN
Shown in the photograph are three tubes-(1) motility AGAR (note subsurface flare--see arrows); (2) ESCULIN HYDROLYSIS (+), and (3) VP (+). The reactions illusTRATEd here are sufficient to rule out ERYSIPELOTHRIX RHUSIOPATHIAE.
LISTERIA motility

Literature Reviews and Queries

Review 1
Review 2
Review 2
Review 3
Each of the following is related to the VIRULENCE of LISTERIA MONOCYTOGENES except:
Each of the following factors has led to the current increase in incidence of LISTERIOSIS except:
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

CLINICAL History

CELLULITIS Lesion

LABORATORY IDENTIFICATION

EIKENELLA BAP
A BACTERIAL isolate that produces pitting of the AGAR and has a bleach-like odor is probably E. corrodens. Closely related species that must be ruled out include:
EIKENELLA - CATALASE & OXIDASE
EIKENELLA BIOCHEMICALS
Most EIKENELLA CELLULITIS INFECTIONS result from:
In view of the feedback to the previous question, the CLINICAL correlation does not seem to fit in this case. Most likely:

Literature Reviews and Queries

Review 1
Review 2
Review 3
Human bite wound INFECTIONS are categorically more severe and more often lead to complications than infected biters from other animals.
To avoid INFECTION with E. corrodens, patients with INSULIN-DEPENDENT DIABETES MELLITIS (IDDM) are advised not to:
We can conclude from ROBINSON & KOURTIS' "Tale of the Toothpick", that, "it is unwise to place a used toothpick in your pocket."

Current Topics in Clinical Microbiology Keywords

Click on a term below to see its use in this Current Topics in Clinical Microbiology course and other available MediaLab courses.

infection (38 occurances)
clinical (33 occurances)
identification (29 occurances)
organism (25 occurances)
pneumoniae (23 occurances)
culture (23 occurances)
blood (23 occurances)
bacterial (22 occurances)
antibiotic (20 occurances)
gram stain (20 occurances)
streptococcus (20 occurances)
streptococci (18 occurances)
agar (18 occurances)
enterococcus (16 occurances)
staphylococcus (16 occurances)
aureus (15 occurances)
clostridium (15 occurances)
septicum (14 occurances)
monocytogenes (14 occurances)
listeria (13 occurances)
laboratory (13 occurances)
eikenella (12 occurances)
disease (12 occurances)
diseases (11 occurances)
penicillin (11 occurances)
virulence (11 occurances)
incubation (10 occurances)
microbiology (10 occurances)
faecium (10 occurances)
gonorrhoeae (9 occurances)
gram-positive (9 occurances)
hemolysis (9 occurances)
hemolytic (9 occurances)
epidemiology (9 occurances)
catalase (9 occurances)
hospital (9 occurances)
pathogen (9 occurances)
pyogenes (8 occurances)
infectious (8 occurances)
milleri (8 occurances)
bacteria (8 occurances)
anginosus (8 occurances)
abscesses (8 occurances)
acute (8 occurances)
colony (8 occurances)
syndrome (8 occurances)
streptococcus milleri (7 occurances)
vancomycin (7 occurances)
coli (7 occurances)
gram-negative (7 occurances)
abscess (7 occurances)
biochemical (7 occurances)
brain (7 occurances)
cephalosporin (7 occurances)
morphology (7 occurances)
protein (7 occurances)
perfringen (6 occurances)
oxidase (6 occurances)
listeriosis (6 occurances)
hydrolysis (6 occurances)
kingae (6 occurances)
kingella (6 occurances)
klebsiella (6 occurances)
clindamycin (6 occurances)
cocci (6 occurances)
carcinoma (6 occurances)
cellulitis (6 occurances)
anaerobic (6 occurances)
bacterium (6 occurances)
gram positive cocci (6 occurances)
fermentation (6 occurances)
glucose (6 occurances)
colon (6 occurances)
diagnosis (6 occurances)
diffusion (5 occurances)
esculin (5 occurances)
drug (5 occurances)
gangrene (5 occurances)
faecalis (5 occurances)
bile (5 occurances)
antimicrobial (5 occurances)
abdominal (5 occurances)
body (5 occurances)
bottle (5 occurances)
intracellular (5 occurances)
inoculated (5 occurances)
lactose (5 occurances)
mrsa (5 occurances)
mucoid (5 occurances)
oxacillin (5 occurances)
pathogenesis (5 occurances)
physician (5 occurances)
polymorphonuclear (5 occurances)
septicemia (5 occurances)
urinary (5 occurances)
subcutaneous (5 occurances)
spectrum (5 occurances)
sterile (5 occurances)
toxin (5 occurances)
staphylococci (5 occurances)
staphylococcal (4 occurances)
vancomycin-resistant (4 occurances)
treatment (4 occurances)
viridan (4 occurances)
septicaemia (4 occurances)
pneumococcal (4 occurances)
pigment (4 occurances)
myonecrosis (4 occurances)
neisseria (4 occurances)
motile (4 occurances)
malignancy (4 occurances)
mannitol (4 occurances)
leukocyte (4 occurances)
inoculation (4 occurances)
identifying (4 occurances)
infection control (4 occurances)
capnocytophaga (4 occurances)
catarrhalis (4 occurances)
coagulase (4 occurances)
aerobic (4 occurances)
ampicillin (4 occurances)
bacitracin (4 occurances)
antibody (4 occurances)
escherichia (4 occurances)
exposure (4 occurances)
gonorrhea (4 occurances)
enterococci (4 occurances)
differential (4 occurances)
contaminated (4 occurances)
clostridial (3 occurances)
colonization (3 occurances)
diabetes (3 occurances)
enteric (3 occurances)
genital (3 occurances)
gastrointestinal (3 occurances)
epidemiological (3 occurances)
fibrinogen (3 occurances)
fragilis (3 occurances)
gram negative (3 occurances)
glomerulonephritis (3 occurances)
hacek (3 occurances)
haemophilus (3 occurances)
hematologic (3 occurances)
bacteremia (3 occurances)
antigen (3 occurances)
bacillus (3 occurances)
bacteroides (3 occurances)
aeruginosa (3 occurances)
agalactiae (3 occurances)
cardiobacterium (3 occurances)
biopsy (3 occurances)
inflammatory (3 occurances)
inhibitor (3 occurances)
injection (3 occurances)
hominis (3 occurances)
meningitis (3 occurances)
methicillin (3 occurances)
methicillin-resistant (3 occurances)
metronidazole (3 occurances)
maltose (3 occurances)
intra-abdominal (3 occurances)
lysis (3 occurances)
macconkey (3 occurances)
mount (3 occurances)
moraxella (3 occurances)
monoclonal (3 occurances)
nccl (3 occurances)
outbreak (3 occurances)
osteomyelitis (3 occurances)
occult (3 occurances)
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needle (3 occurances)
nerve (3 occurances)
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photomicrograph (3 occurances)
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sepsis (3 occurances)
solubility (3 occurances)
pseudomona (3 occurances)
respiratory (3 occurances)
vaccine (3 occurances)
virulent (3 occurances)
toxic (3 occurances)
sputum (3 occurances)
superoxol (3 occurances)
symptom (3 occurances)
taxonomy (3 occurances)
tetrad (3 occurances)
suppurative (2 occurances)
spinal (2 occurances)
stool (2 occurances)
strain-associated (2 occurances)
streptococcal (2 occurances)
subdural (2 occurances)
sucrose (2 occurances)
tuomanen (2 occurances)
urine (2 occurances)
urea (2 occurances)
wbc (2 occurances)
zona (2 occurances)
rhusiopathiae (2 occurances)
robinson (2 occurances)
rocourt (2 occurances)
rouquette (2 occurances)
ruminant (2 occurances)
saliva (2 occurances)
saprophyte (2 occurances)
scalded (2 occurances)
silage (2 occurances)
serotype (2 occurances)
serous (2 occurances)
pneumolysin (2 occurances)
pyogenic (2 occurances)
phenotype (2 occurances)
nitrates (2 occurances)
nitrites (2 occurances)
non-motile (2 occurances)
neutropenia (2 occurances)
ochracea (2 occurances)
nosocomial (2 occurances)
metastatic (2 occurances)
optochin (2 occurances)
otitis (2 occurances)
pasteurella (2 occurances)
penetration (2 occurances)
peptidase (2 occurances)
pathogenic (2 occurances)
pathogenicity (2 occurances)
pathology (2 occurances)
oxidase-positive (2 occurances)
pigmentation (2 occurances)
piscitelli (2 occurances)
phagocytosis (2 occurances)
necrosis (2 occurances)
neonatal (2 occurances)
mueller-hinton (2 occurances)
multocida (2 occurances)
microbiol (2 occurances)
malignancies (2 occurances)
management (2 occurances)
liver (2 occurances)
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lymph (2 occurances)
methicillin-sensitive (2 occurances)
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medicine (2 occurances)
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insulin (2 occurances)
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jedrzeja (2 occurances)
kornbluth (2 occurances)
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indole (2 occurances)
immunity (2 occurances)
immunocompromised (2 occurances)
immunoglobulin-binding (2 occurances)
hydrolyzes (2 occurances)
iddm (2 occurances)
cardiac (2 occurances)
ceftazidime (2 occurances)
cell-mediated (2 occurances)
catheter (2 occurances)
canimorsus (2 occurances)
ciprofloxacin (2 occurances)
adhesin (2 occurances)
adhesion (2 occurances)
acinetobacter (2 occurances)
actinomycetemcomitan (2 occurances)
actinobacillus (2 occurances)
anaerobe (2 occurances)
anaerobes (2 occurances)
aminoglycosides (2 occurances)
antiphagocytic (2 occurances)
aphrophilus (2 occurances)
bacteriology (2 occurances)
beta-lactamase (2 occurances)
baumanii (2 occurances)
arabinose (2 occurances)
arm (2 occurances)
asaccharolytic (2 occurances)
hepatocyte (2 occurances)
hirshow (2 occurances)
granulosa (2 occurances)
griego (2 occurances)
gram negative diplococci (2 occurances)
gram positive (2 occurances)
exudate (2 occurances)
fibrin (2 occurances)
gelfand (2 occurances)
garbutt (2 occurances)
fluorescent (2 occurances)
gene (2 occurances)
genus (2 occurances)
discriminatory (2 occurances)
enterocolitis (2 occurances)
environment (2 occurances)
environmental (2 occurances)
encephalitis (2 occurances)
epidermal (2 occurances)
epidural (2 occurances)
erysipelothrix (2 occurances)
csf (2 occurances)
dfa-nonreactive (2 occurances)
diplococci (2 occurances)
donachie (2 occurances)
concentration (2 occurances)
diagnostic (2 occurances)
diarrhea (2 occurances)