Microbiology Chapter on Disease-Causing Bacteria

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Questions and Answers

Which of the following bacteria is commonly associated with food poisoning and gastrointestinal infections?

Escherichia coli (correct)

Corynebacterium diphtheriae

Clostridium perfringens (correct)

Staphylococcus aureus

What disease is caused by Clostridium botulinum?

Food poisoning with progressive muscle paralysis (correct)

Diphtheria

Typhoid fever

Shigellosis

Which organism is linked to urinary tract infections and meningitis?

Clostridium difficile

Klebsiella organisms (correct)

Corynebacterium diphtheriae

Pseudomonas aeruginosa (correct)

Which of the following bacteria is primarily responsible for causing pertussis?

Bordetella pertussis Signup and view all the answers

Identify the bacteria responsible for causing pneumonia and upper respiratory infections.

S.pneumoniae Signup and view all the answers

What type of infection is primarily associated with Escherichia coli?

Cystitis Signup and view all the answers

Which of these bacteria is associated with nosocomial infections?

S.epidermidis Signup and view all the answers

Which bacteria are known to be involved in causing pink eye?

Haemophilus aegyptius Signup and view all the answers

Which organism is known for being resistant to all ß-lactam antibiotics and aztreonam?

Organisms producing extended-spectrum ß-lactamases (ESBLs) Signup and view all the answers

What is the primary purpose of active surveillance testing for multidrug-resistant organisms?

To identify colonized patients for contact precautions Signup and view all the answers

Which antibiotic class can effectively treat infections caused by organisms that produce Klebsiella pneumoniae carbapenemase (KPC)?

Tigecycline and colistimethate sodium Signup and view all the answers

Approximately what percentage of community-acquired staphylococcal infections are due to MRSA?

50% Signup and view all the answers

Which factor is considered the most significant method of preventing healthcare-associated infections?

Frequent handwashing Signup and view all the answers

Why are newer antibiotics developed for treating MRSA and VRE?

To combat the growing resistance to existing antibiotics Signup and view all the answers

What is a potential consequence of MRSA becoming resistant to all available antibiotics?

Increase in mortalities from common infections Signup and view all the answers

Which of the following infections is primarily associated with Vancomycin-resistant Enterococcus (VRE)?

Urinary tract infections (UTIs) Signup and view all the answers

What distinguishes gram-positive bacteria from gram-negative bacteria?

Gram-positive bacteria stain purple due to a thick cell wall. Signup and view all the answers

How do bacteria damage host tissues during an infection?

By secreting enzymes that damage tissues. Signup and view all the answers

What role do exotoxins play in bacterial infections?

They directly damage host cells. Signup and view all the answers

Which morphological type of bacteria is rod-shaped?

Bacilli Signup and view all the answers

What condition allows non-pathogenic bacteria to become harmful?

When the normal flora is disrupted. Signup and view all the answers

What is the main characteristic of prokaryotes such as bacteria?

Lack of a nucleus. Signup and view all the answers

Which statement about systemic infections is accurate?

They can spread throughout the body via blood. Signup and view all the answers

What factor primarily influences the choice of antibiotic therapy for a bacterial infection?

The Gram stain response of the bacteria. Signup and view all the answers

Which of the following is NOT a typical sign of infection?

Increased appetite Signup and view all the answers

What is the impact of a compromised host defense system on infection risk?

It increases the likelihood of microorganisms causing infection. Signup and view all the answers

Study Notes

Systemic Signs and Symptoms

Pain and swelling
Increased WBC
Formation of pus

Common Disease-Causing Bacteria

Clostridium organisms
- C. botulinum: Food poisoning with progressive muscle paralysis
- C. difficile: Diarrhea, colitis
- C. perfringens: Food poisoning, gangrene
- C. tetani: Tetanus (lockjaw)
Corynebacterium diphtheriae: Diphtheria
Escherichia coli: Urinary tract infections, cystitis, peritonitis, inflammatory gastrointestinal infections
Haemophilus organisms
- H. aegyptius: Pink eye
- H. influenzae: Nasopharyngitis, meningitis, pneumonia, otitis media, upper respiratory tract infections
- H. pertussis: Pertussis (whooping cough)
Helicobacter pylori: Peptic ulcers, gastritis
Klebsiella and Enterobacter organisms: Urinary tract infections, peritonitis, pneumonia
Proteus organisms: Urinary tract infections, meningitis
Pseudomonas aeruginosa: Urinary tract infections, meningitis
Salmonella organisms
- S. typhi: Typhoid fever
- Other Salmonella organisms: food poisoning, gastroenteritis
Shigella organisms: Shigellosis, diarrhea with abdominal pain and fever (dysentery)
Staphylococcus aureus: Skin infections, pneumonia, urinary tract infections, acute osteomyelitis, toxic shock syndrome
Streptococcus organisms
- S. epidermidis: Nosocomial sepsis
- S. faecalis: Genitourinary infection, infection of surgical wounds
- S. pneumoniae: Pneumococcal pneumonia, otitis media

Infection

Invasion of the body by a pathogen/microorganism
Signs and symptoms develop in response to invasion
Most common causes: bacteria, fungi, protozoa, viruses
Classified as localized (limited to a small area) or systemic (widespread throughout the body, often spread via the blood)

Bacteria

One-celled microorganisms found everywhere on earth
Involved in fermentation, putrefaction, infectious diseases, and nitrogen fixation
Can be harmful or beneficial:
- Non-pathogenic: Usually do not cause disease, part of normal flora, often beneficial
- Pathogens: Disease-causing microbes

Bacteria and Disease

Bacteria can cause disease in two ways:
- They can enter the body and grow inside human cells: e.g., tuberculosis
- They can secrete toxins that damage cells:
  - Exotoxins: Usually produced by gram-positive bacteria
  - Endotoxins: Present in the cell wall of gram-negative bacteria, released on death of bacterium, vasoactive compounds that can cause septic shock
  - Enzymes: Damage tissues and promote the spread of infection

Bacteria: Morphology

Bacteria take on different shapes (morphology)
Grouped based on their shape:
- Bacilli: Rod-shaped organisms
- Spirochetes: Include spiral forms and vibrio
- Cocci: Spherical forms
  - Diplococci
  - Streptococci

Bacteria: Classification

Classified as prokaryotes
No nuclear membrane, no nucleus
Function metabolically and reproduce by binary fission
Complex cell wall structure
Do not require living tissues to survive
Vary in size and shape

Bacteria: Gram Staining

Most important categorization: Gram stain procedure
Guides the choice of antibiotic therapy
- Gram-positive bacteria: Purple, thick cell wall, thick outer capsule
- Gram-negative bacteria: More complex cell wall structure, more difficult to treat, drug molecules have a hard time penetrating cell wall

Bacterial Infection

Host defenses are compromised; susceptible to infection
Microorganism invades and multiplies in body tissues
Infectious process can overwhelm the body’s defense system
Classic signs and symptoms: Fever, chills, sweating, redness
Different types of infection:
- Nosocomial infections (HAI): acquired in the healthcare setting (e.g., MRSA, VRE)
- Community-acquired infections: acquired outside of the healthcare setting
Other sources of infection: Mechanical ventilators, intravenous infusion lines, dialysis equipment

Multidrug-Resistant Organisms (MDRO)

Organisms resistant to one or more classes of antimicrobial drugs:
- Methicillin-resistant Staphylococcus aureus (MRSA)
- Vancomycin-resistant Enterococcus (VRE)
- Organisms producing extended-spectrum ß-lactamases (ESBLs)
- Organisms producing Klebsiella pneumoniae carbapenemase (KPC)
Active surveillance testing by swabbing nares and/or rectal/perirectal area
Purpose is to appropriately place colonized patients into contact precautions

Multidrug-Resistant Organisms (MDRO): MRSA

Threat of MRSA becoming resistant to all antibiotics
No longer only seen in hospitals, spread to community setting
Approximately 50% of staphylococcal infections in the community involve MRSA
VRE: Usually seen in urinary tract infections (UTIs)

Multidrug-Resistant Organisms: New Antibiotics

Newer antibiotics developed to treat VRE and MRSA

Multidrug-Resistant Organisms: Extended-Spectrum ß-Lactamase (ESBL)

Organisms producing ESBL are resistant to all ß-lactam antibiotics and aztreonam
Can be treated only with carbapenems or sometimes quinolones
Some bacteria have become resistant to carbapenems: Klebsiella pneumoniae
Klebsiella pneumoniae carbapenemase (KPC)
Treatment for difficult cases: tigecycline or colistimethate sodium

Health Care-Associated Infection (HAI)

Over 70% of health care-associated infections are preventable
Most commonly transmitted by direct contact
Handwashing: The single most important method of prevention
Disinfectants are essential

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Description

This quiz covers systemic signs and symptoms of bacterial infections as well as common disease-causing bacteria. It delves into specific bacteria such as Clostridium, Corynebacterium, Escherichia, and others, discussing their associated diseases. Test your knowledge and understanding of these important microbiological concepts.