Infection Evaluation Quiz

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Questions and Answers

What is the patient's chief complaint?

Severe left knee pain, swelling and redness (correct)

Recent left knee arthroscopy

Fever, chills, difficulty bearing weight on the affected leg

History of diabetes mellitus

Which of the following is NOT a vital sign mentioned in the case?

Blood Pressure

Oxygen Saturation (correct)

Temperature

Respiratory Rate

Based on the provided information, what is the most likely cause of the patient's septic arthritis?

Fungal infection

Autoimmune disease

Viral infection

Bacterial infection (correct)

What is the significance of the elevated ESR and CRP levels in this case?

They suggest an inflammatory process (C) Signup and view all the answers

Which of the following is NOT a possible bacterial cause of septic arthritis in this case?

Mycobacterium tuberculosis (A) Signup and view all the answers

What does the term "neutrophilic predominance" refer to in the laboratory findings?

A high number of neutrophils in the blood (B) Signup and view all the answers

What is the significance of the Gram-positive cocci in the joint fluid?

It suggests a bacterial infection (D) Signup and view all the answers

What is the likely next step in the patient's management?

Antibacterial therapy (C) Signup and view all the answers

Which of the following factors is NOT considered in the pre-analytics stage of evaluating infection?

Susceptibility report (D) Signup and view all the answers

What is a crucial factor in the pre-analytics stage of infection evaluation, ensuring the sample's integrity and usefulness for analysis?

Sterile technique during specimen collection (D) Signup and view all the answers

Which of the following factors is assessed in the post-analytics stage of infection evaluation?

The identification of the pathogen (C) Signup and view all the answers

What is a key component of evaluating infection in the analytics stage?

Evaluating the susceptibility of the pathogen to antibiotics (D) Signup and view all the answers

Which of the following is considered a pre-analytics factor in the evaluation of infection?

The type of agar plates used (A) Signup and view all the answers

Which of these factors is assessed during the post-analytics stage of infection evaluation?

The clarity of the report and its impact on patient management (A) Signup and view all the answers

During the analytics stage, what specific aspect of the infection is evaluated?

The identification and susceptibility of the pathogen to antibiotics (A) Signup and view all the answers

What is one of the main considerations during the post-analytics phase of infection evaluation?

Whether the public health authorities were notified if the infection is notifiable (D) Signup and view all the answers

Which of the following is a common clinical manifestation of Staphylococcus epidermidis infections?

Prosthetic valve endocarditis (C) Signup and view all the answers

Which of the following is a virulence factor specifically associated with Staphylococcus saprophyticus that contributes to urinary tract infections?

Protein hemagglutinin/fimbrae (A) Signup and view all the answers

What is the typical presentation of Staphylococcus aureus infections?

Treatment regimens similar to methicillin-sensitive Staphylococcus aureus (MSSA) infections (D) Signup and view all the answers

Which of the following bacteria is commonly associated with medical device implantation infections?

Staphylococcus haemolyticus (D) Signup and view all the answers

Which of the following is a distinguishing feature of Staphylococcus lugdunensis infections?

Frequently leads to native valve endocarditis (A) Signup and view all the answers

Which of the following species is commonly associated with community-acquired urinary tract infections (CA-UTIs) in young women?

Staphylococcus saprophyticus (A) Signup and view all the answers

Which of the following factors is commonly used to differentiate between contamination and true infection with Coagulase Negative Staphylococci (CNST) in blood cultures?

Number of positive blood culture bottles (D) Signup and view all the answers

Which of the following bacterial species is commonly found as part of the normal skin flora?

Staphylococcus epidermidis (B) Signup and view all the answers

What is the primary focus of pre-analytics in the testing process?

Effective specimen collection (C) Signup and view all the answers

Which type of agar is used for identifying MRSA?

Chrom agar (B) Signup and view all the answers

What characteristic is NOT assessed during the analytics phase of bacteriology?

Patient's medical history (D) Signup and view all the answers

Why is a larger volume of specimen collection generally preferred?

It increases the likelihood of detecting pathogens (A) Signup and view all the answers

Which of the following is an example of a pathogen that demonstrates beta hemolysis?

Staphylococcus aureus (C) Signup and view all the answers

Which phase of the testing process has the highest rate of errors?

Pre-analytics (A) Signup and view all the answers

What role does the Gram stain play in bacteriology analytics?

It guides treatment decisions (A) Signup and view all the answers

What is a common morphology characteristic of Klebsiella?

Mucoid colonies (A) Signup and view all the answers

What is the primary virulence factor of Group A Streptococcus that aids in adherence and immune evasion?

M-protein (C) Signup and view all the answers

Which clinical condition is a consequence of untreated strep throat that involves a red rash and red 'strawberry tongue'?

Scarlet Fever (C) Signup and view all the answers

Which Group of Streptococcus is primarily associated with pneumonia?

S.mitis group (D) Signup and view all the answers

What percentage of untreated Group A Streptococcus infections may lead to Acute Rheumatic Fever?

0.3-3% (C) Signup and view all the answers

Which streptococcal condition is characterized by purulent lesions and is often found on the skin?

Impetigo (D) Signup and view all the answers

What is the risk factor for developing Streptococcal Toxic Shock Syndrome?

Diabetes (A) Signup and view all the answers

What condition describes extensive, rapid necrotic spread of tissue, commonly linked to polymicrobial infections?

Necrotizing fasciitis (B) Signup and view all the answers

Which strain of Streptococcus is linked to the risk of colorectal cancer?

S.bovis (A) Signup and view all the answers

What is the most likely source of Group B Streptococcus infection in a 5-day-old infant with symptoms of lethargy and poor feeding?

Intrauterine infection (C) Signup and view all the answers

Which of the following is a virulence factor associated with S.pneumoniae?

Capsule (A) Signup and view all the answers

What is the primary cause of meningitis in patients older than 3 months according to the content?

S.pneumoniae (C) Signup and view all the answers

Which of the following is a typical clinical manifestation of lower respiratory tract infection caused by S.pneumoniae?

Acute fever and shortness of breath (C) Signup and view all the answers

Which laboratory method is utilized to grow S.pneumoniae?

Blood agar (A) Signup and view all the answers

What is the significance of finding a catalase-negative result in the laboratory identification of S.pneumoniae?

Helps differentiate it from Staphylococcus species (A) Signup and view all the answers

What is the first line therapy recommended for conditions caused by S.pneumoniae?

Penicillin (B) Signup and view all the answers

What kind of infection is empyema, which is commonly associated with S.pneumoniae?

Accumulation of fluid in the pleural space (D) Signup and view all the answers

Study Notes

Gram-Positive Cocci Infections & Fever

Gram-positive cocci are bacteria characterized by their shape (cocci) and their reaction to Gram staining (positive). This presentation focuses on infections and fever caused by these type of bacteria.
Slides included images of gram-positive cocci and gram-negative cocci, highlighting the differences in their reactions to gram stains (wear pink on Wednesday).
The presenter, Robert M. Taylor, PhD, FCCM, presented a case study involving a 52-year-old female with a history of diabetes and a recent knee arthroscopy, experiencing significant knee pain, swelling, and redness for three days.
Other case study details: fever, chills, and difficulty bearing weight on the affected leg, denies recent trauma or travel history. Blood pressure and other vital signs were also noted.

Disclosures

No disclosures were made.

Treaty Land Acknowledgment

The presentation acknowledged the traditional territories of diverse Indigenous groups on which Memorial University's campuses are located.
Recognition of the Beothuk, Mi'kmaq, Innu, and Inuit peoples and their histories.
A picture of a Beothuk woman was displayed in the slide.

Case

A 52-year-old female with diabetes had a left knee arthroscopy.
Symptoms included severe knee pain, swelling, redness, fever, chills and limited weight bearing.
No recent travel or trauma were reported.

Laboratory Findings

White blood cell (WBC) count of 15,000/μL (neutrophilic predominance)
Elevated erythrocyte sedimentation rate (ESR)
Elevated C-reactive protein (CRP)
Pending blood cultures
Joint aspiration revealed turbid yellow fluid, with a high leukocyte count (85,000/µL) with 90% neutrophils.
Gram stain indicated the presence of polymorphonuclear cells and gram-positive cocci.

Differential Diagnosis for Septic Arthritis

The most likely pathogens causing septic arthritis were Staphylococcus aureus, Staphylococcus lugdunensis, group A Streptococcus, group B Streptococcus, Streptococcus anginosus and Enterococcus faecalis/faecium.

Objectives

Identify the characteristics that distinguish pathogens from contaminants.
Explain the various stages of bacteriology testing.
Distinguish characteristics of staphylococci, streptococci, and enterococci species
Predict organism identity based on select diagnostic findings
Learn about other clinical characteristics of various bacterial species : S. aureus, S. lugdunensis, S. saprophyticus, Streptococcus pneumoniae, Group A Streptococci, Group B Streptococci and Enterococcus spp., epidemiology, pathogenesis, disease manifestations, diagnostic techniques, first-line treatment and public health responses.

How Humans are Dirty

Various body sites have different microbial densities and compositions. The mouth has a massive amount of bacteria, followed by the skin (differing levels of density depending on the area and skin folds).
The lower digestive tract has the highest density of organisms. Sterile sites include the bladder, lungs, liver, etc.

What is Infection?

Infection is the invasion and growth of germs in the body. Several factors influence infection, including:
Epidemiology of the pathogen, patient risk factors, pre-analytic factors, analytic factors, and post-analytic factors (tests performed on collected samples of suspected infectious material).

Pre-Analytics

Proper specimen collection is critical, with volume being an important factor. Multiple sites and sets are recommended for blood cultures.

Analytics (Bacteriology)

Diagnostic techniques depend on the type of specimen.
Gram stain is a fundamental tool to guide work-up and treatment.
Different types of media (enriched, selective, differential) are used according to individual pathogen requirements in order to effectively identify pathogens.

Analytics (Morphology)

Gram-positive cocci can be single, in pairs (diplococci), chains (streptococci), or clusters of varying shapes.
Hemolysis (patterns of RBC lysis on blood agar) can help identify specific species of gram-positive bacteria.

Analytics (Biochemical Testing)

Biochemical testing includes tests like coagulase, catalase, and urease, helps identify bacteria. Commercial techniques like MALDI-TOF (Mass Spectrometry) are increasingly common.

Gram-What?

The Gram stain is the initial test to determine if an organism is gram-positive or gram-negative, based on cell wall structure. There are fundamental differences in cell wall composition that lead to different outcomes.

Gram Morphologies

Bacterial species have characteristic shapes, as determined by their cell wall features.

Question 1 (Most Important Pre-analytic Factor for Bacteremia Diagnosis)

The most important pre-analytic factor is the volume of blood collected for blood culture.

Question 2 (Hemolysis Pattern of S. aureus)

S. aureus displays a beta hemolysis pattern on blood agar.

Staphylococcus Species

Coagulase Positive Staphylococci (includes S. aureus)
Coagulase Negative Staphylococci (includes S. lugdunensis, S. saprophyticus)

S. aureus Complex

Worldwide distribution
Common cause of skin infections (SSTIs)
Commonly found in hospital settings
MRSA is increasingly difficult to treat.

Pathogenesis

S. aureus colonizes skin/mucous membranes.
Invasins, toxins and adhesins contribute to S. aureus pathogenicity.

Clinical Disease

S. aureus is involved in various localized and systemic infections including Skin infections, bacteremia, pneumonia, endocarditis, SSTIs, and more.
S. aureus is a key player in causing community-acquired pneumonia.

Diagnostics

MRSA screening with nasal swabs is a common procedure.
Gram stains, media (blood agar, mannitol agar), and biochemical tests (coagulase and catalase) are helpful in identifying and differentiating these species.

Question 3 (Key Biochemical Tests for Staphylococci ID)

Catalase and coagulase.

Antibiotics 101 & Susceptibility Testing

Antibiotics target different bacterial structures and functions (e.g., cell wall synthesis, protein synthesis, DNA synthesis, metabolic processes).
Minimum Inhibitory Concentration (MIC) is the lowest drug concentration that inhibits visible growth.

Penicillinases

Penicillinases are enzymes produced by some bacteria to break down penicillin.
A nitrocefin disk or penicillin zone edge test can detect the presence of penicillinase activity.

mec A - S. aureus

mec A encodes a penicillin-binding protein.
This is associated with methicillin resistance (MRSA).

Susceptibility Testing

The majority of S. aureus is resistent to penicillin.
MRSA is resistant to most penicillin-related drugs. Ceftaroline/Ceftobiprole bind differently to the penicillin-binding protein, potentially being used for treating MRSA.

Question 4 (Protein Ceftaroline Binds To in MRSA)

PBP-2a

S. lugdunensis

Similar global distribution compared to S. aureus.
Often associated with infections in sterile sites.
Important to consider in infections involving native valves.

S. saprophyticus

Often associated with urinary tract infections (UTIs), particularly in women.

Question 5 (Clinical Feature Associated with S. lugdunensis Infection)

Native valve endocarditis.

Other Coagulase-Negative Staphylococci (CONS)

CONS are a heterogeneous group with diverse pathogenic roles.
The most commonly seen species, S. epidermidis, is mostly a normal flora. However they can also cause infections particularly when seen in the blood stream.

Question 6 (Most Likely Explanation for S. hominis Isolation)

Contamination during sample collection.

Question 7 (Pathogens of Concern & Treatment in Blood Culture)

S. aureus and S. lugdunensis are the major potential pathogens. Broad spectrum antibiotic therapy like vancomycin should be used if suspected MRSA, later confirmed via drug sensitivity.

Group B Streptococcus (GBS)

GBS is commonly found in the lower GI tract and genital tract in many animals.
It is often asymptomatic in otherwise healthy adults and children.
During pregnancy, it can cause considerable problems in newborns.
Chemoprophylaxis with antibiotics can prevent GBS transmission from mother to baby.

S. pneumoniae

Causes many infections, particularly respiratory infections (pneumonia, otitis media, meningitis).
Globally ubiquitous and common in the respiratory tract (normal flora).

Question 8 (Most Likely Source of GBS Infection in Newborn)

Early-onset neonatal sepsis.

Question 9 (Enterococci Species Commonly Associated with VRE)

E. faecium.

Enterococci

Enterococci are common gut bacteria that cause a variety of infections, including bacteremia, endocarditis, and UTIs.
They are frequently resistant to large classes of antibiotics.

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Description

Test your knowledge on the evaluation of infections, focusing on septic arthritis and the interpretation of laboratory findings. This quiz covers vital signs, laboratory results, and management strategies related to infection. Perfect for healthcare students and professionals to enhance their understanding.