Microbiology Quiz: Infections and Ulcers

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Questions and Answers

What is the primary cause of decubitus ulcers?

Fungi in the air

Viruses

Parasites in the skin

Bacteria near the rectum (correct)

Which organism is NOT associated with diabetic foot ulcers?

S.aureus

Pseudomonas aeruginosa

Streptococci

Borrelia burgdorferi (correct)

What is a recommended specimen type for culture in suspected anaerobic infections?

Sputum samples

Urine samples

Tissue aspirates (correct)

Swab samples

Which of the following is a key feature of microscopic examination using Gram stain?

Can determine specimen quality Signup and view all the answers

Which culture method is NOT typically used for anaerobic infections?

Swab culture in transport medium Signup and view all the answers

Which organism is primarily associated with Staphylococcal scalded-skin syndrome?

Staphylococcus aureus Signup and view all the answers

What type of transport media is recommended for specimens collected for anaerobic culture?

Anaerobic transport media Signup and view all the answers

What condition is characterized by inflammation with pus and often includes the Group A streptococci?

Impetigo Signup and view all the answers

Which of the following conditions is linked with erythema migrans?

Lyme disease Signup and view all the answers

Which of the following organisms is commonly associated with human bite wound infections?

S.aureus Signup and view all the answers

What type of infection is characterized by a diffuse infection in deep epidermis and subcutaneous tissue?

Cellulitis Signup and view all the answers

Which organism is specifically associated with gas gangrene?

C.perfringens Signup and view all the answers

An infection that results from the obstruction of oil or sweat glands is likely to be classified as which of the following?

Folliculitis Signup and view all the answers

What is the primary causative organism of erysipelas, a painful superficial skin infection?

Group A streptococci Signup and view all the answers

Which organism is linked to infections from contaminated hot tubs?

P.aeruginosa Signup and view all the answers

Which of the following types of bacteria are part of the normal skin flora?

Corynebacterium Signup and view all the answers

What is the typical incubation period for Tularemia?

1 - 21 days Signup and view all the answers

Which of the following descriptions pertains to the appearance of colonies on SBA for the bacteria responsible for Tularemia?

Fried egg colonies Signup and view all the answers

What is the mortality rate for untreated Tularemia?

30% Signup and view all the answers

What primary animal is associated with the transmission of Francisella tularensis?

Rabbits Signup and view all the answers

Which of the following conditions is NOT related to Tularemia?

Bubonic plague Signup and view all the answers

Which feature characterizes Brucellosis as described?

Profuse sweating and malaise Signup and view all the answers

What is the infective dose for Tularemia?

10 - 50 organisms Signup and view all the answers

How long can the Tularemia organism persist in moist soil?

Months Signup and view all the answers

What is the most common organism associated with osteomyelitis?

Staphylococcus aureus Signup and view all the answers

Which specimen collection method is used to diagnose conjunctivitis?

Swab of the conjunctiva Signup and view all the answers

What type of culture is primarily recommended for malignant otitis externa?

All of the above Signup and view all the answers

Which condition is characterized by inflammation of the cornea?

Keratitis Signup and view all the answers

What distinguishes an overt bioterrorism event from a covert one?

It has immediate impact and early recognition. Signup and view all the answers

Which organism is commonly involved in malignant otitis externa?

Pseudomonas aeruginosa Signup and view all the answers

In which situation is bone marrow culture primarily indicated?

For identifying Brucella or Mycobacteria Signup and view all the answers

What is the main characteristic of endophthalmitis?

Inflammation of the eyeball's interior Signup and view all the answers

What is one of the first signs of a biological attack?

Human illness Signup and view all the answers

Which of the following is a characteristic of bioterror agents?

Odorless and tasteless Signup and view all the answers

What is the cost of anthrax compared to conventional weapons for achieving 50% casualties over a 1 sq/km area?

$1 Signup and view all the answers

What method can biological agents be delivered via?

Food or water contamination Signup and view all the answers

Which organization established the Laboratory Response Network (LRN)?

CDC Signup and view all the answers

In which laboratory level does confirmatory testing take place within the LRN?

Reference Labs Signup and view all the answers

What is a significant factor that affects the dissemination of biological agents?

Weather conditions Signup and view all the answers

Which category does Yersinia pestis fall under in the CDC classification of biological agents?

Category A Signup and view all the answers

Which example represents a characteristic of Category B biological agents?

E. coli Signup and view all the answers

What is a potential impact of a bioterror attack classified as Category A?

High public panic and social disruption Signup and view all the answers

What is the most common form of anthrax exposure?

Cutaneous anthrax Signup and view all the answers

What is the mortality rate associated with gastrointestinal anthrax?

50% Signup and view all the answers

What type of specimen is collected for diagnosing inhalation anthrax?

Sputum Signup and view all the answers

Which symptoms are NOT associated with inhalation anthrax?

Nausea and vomiting Signup and view all the answers

What form of plague is characterized by infected lymph nodes?

Bubonic plague Signup and view all the answers

Which of the following anthrax types requires ingestion of spores for infection?

Gastrointestinal anthrax Signup and view all the answers

Which type of plague is considered the deadliest due to its transmissibility?

Pneumonic plague Signup and view all the answers

What is NOT a common symptom of pneumonic plague?

Rash Signup and view all the answers

What type of bacterium is responsible for anthrax?

Bacillus anthracis Signup and view all the answers

What is a laboratory method used to identify Bacillus anthracis?

Gram staining Signup and view all the answers

Study Notes

Skin and Soft Tissue

Skin is the outermost layer, comprising epidermis (outermost layer), dermis (hair follicles, sebaceous glands, sweat glands), subcutaneous layer (fat), fascia (fibrous tissue), and muscles.
Wound infections can result from trauma, blockage of glands, hair follicle inflammation.
Infecting organisms can be endogenous (normal flora) or exogenous (outside the body).
Single or multiple organisms can cause infections.
Identifying and isolating colony types is crucial for mixed cultures.
Normal skin flora includes staphylococci (S. epidermidis & S. aureus), diphtheroids (Corynebacterium), micrococci, streptococci (non-hemolytic), Propionibacterium acnes, anaerobes, and yeast.
Dermatitis is skin inflammation, caused by Candida spp., S. aureus, coliforms, Corynebacterium spp., and molds (Dermatophytes).
Pyoderma is inflammation with pus, including Impetigo (blister-like infection, Group A streptococci, S. aureus), Erysipelas (superficial, painful, Group A streptococci, S. aureus), Anthrax (rarely).
Erysipeloid is superficial soft-tissue infection, associated with animal products, caused by Erysipelothrix rhusiopathiae.
Cellulitis is deep epidermis and subcutaneous tissue infection, caused by Group A streptococci, S. aureus.
Folliculitis is infected hair follicles (sometimes P. aeruginosa).
Furuncles (boils) are deep hair follicle infections.
Carbuncles involve multiple hair follicles.
Abscesses are pus collections in skin and subcutaneous tissue.
Soft tissue (wound) infections involve injured tissue (surgery, burns, bites) caused by various organisms, including S. aureus, streptococci, and anaerobes. Also, burn wounds are caused by S. aureus, and P. aeruginosa
Animal bites can cause infection due to Pasteurella multocida, Capnocytophaga canimorsus, S. aureus, anaerobes, and rabies.
Human bites can cause infection due to S. aureus, alpha.
Myonecrosis is severe muscle infection (gas gangrene) caused by C. perfringens.
Necrotizing fasciitis is very severe fascia infection caused by Group A strep, and S. aureus.
Decubitus ulcers are bedsores caused by bacteria near the rectum (Enterobacteriaceae, Pseudomonas, Enterococci).
Diabetic foot ulcers take a long time to heal, caused by S. aureus, streptococci, enterococci, Enterobacteriaceae, Pseudomonas aeruginosa, and anaerobes.
Nodular lymphangitis has causative agents Sporothrix schenckii, Nocardia spp., Actinomyces spp., and Mycobacteria.
Dermatological manifestations of systemic infections include rashes from Borrelia burgdorferi (erythema migrans), T. pallidum, Rickettsiae, Leptospira, and Mycobacterium leprae.
Viral causes include measles (Rubeola and Rubella), chickenpox/shingles (Varicella-Zoster Virus), Herpes Simplex Virus, and Warts (HPV)
Toxin-mediated skin diseases, include Staphylococcal scalded-skin syndrome, Toxin shock syndrome, S. aureus and S. pyogenes, and Scarlet fever (S. pyogenes).
Specimen collection and transport methods include avoiding surface contamination, decontaminating skin or mucous membranes, using tissue/pus aspirates instead of swabs, and keeping samples moist for transport. Swabs are typically less desirable, and anaerobic infections require specific transport media.
Microscopic examination includes Gram stains for detection of clinically significant organisms, quality control of specimens (reject if many epithelial cells), and wet mounts with KOH and calcofluor white, and acid-fast stains.
Routine cultures use BAP, CHOC, MAC, and PEA media, and CO2 incubation at 35°C.
Anaerobic cultures are recommended for closed wounds and abscesses.
Other cultures may include Lowenstein-Jensen, Middlebrook (for mycobacteria, viral culture, and shell vials and Sabouraud's agar). Additional cultures may include Eye, Bone, BM, and External ear samples.
Eye cultures often involve NF of the mucous membrane, Corynebacterium, Viridans strep., Moraxella catarrhalis, staphylococci (S. aureus and CONS), Haemophlius influenzae, anaerobes, and GNR.
Conjunctivitis, keratitis, and endophthalmitis are eye diseases. Eye specimen collection includes conjunctival swabs and corneal scrapings with special spatulas. Eye chamber fluid can be used for endophthalmitis. Processing may involve gram staining, and MAC, CHOC, BAP culture, and anaBAP.
Osteomyelitis is a bone infection often caused by S. aureus. Bone cultures are commonly performed in enriched broth and on agar media (CHO). Bone marrow cultures are conducted for detecting Brucella or Mycobacteria.
External Ear infections and cultures, often from Moisture-related otitis externa ("swimmer's ear") and malignant otitis externa (severe, sometimes with underlying conditions like diabetes). Specimens may involve debris from the ear canal, collected with swabs, followed by gram stain and BAP, CHOC, and MAC culture growth.
Agents of Bioterrorism are harmful microorganisms or toxins used in unlawful attacks.

Bioterrorism

Bioterrorism is the intentional use or threat of living organisms or toxins to harm humans, animals, or plants.
The goal is to instigate fear and intimidate governments or societies.
Bioterrorism can have immediate, overt impacts or delayed, covert responses.
The past has seen incidents involving rye ergot, Bacillus anthracis, Pseudomonas mallei, salmonella, and Bacillus anthracis in recent history.
Bioterrorist agents are frequently inexpensive and easy to produce, causing widespread fear.
Traits of bioterrorist agents include being odorless, colorless, or tasteless and affecting humans first through illness.
Common delivery methods include food/water contamination, aerosol dispersal, using vehicle sprayers, hand sprayers, aircraft sprayers, and mail systems.

Laboratory Response Network (LRN)

The LRN was developed by the CDC in 1999.
The LRN is a network of labs designed to respond to biological or chemical threats, following predetermined protocols and providing timely, accurate test results.
LRN laboratories are organized as sentinel laboratories (clinical) and reference laboratories.
Sentinel labs receive specimens, recognize potential issues, rule out certain things, and then refer to reference labs of the LRN. Reference labs provide confirmatory testing, while more specialized national labs (CDC, Military, Bioforensics) conduct definitive characterization.

Category A, B, and C Biological Agents

Category A agents have high mortality, ease of spread, and potential for mass panic; they include anthrax, smallpox, botulism, and plague.
Category B agents are moderately easy to spread with moderate illness but with lower mortality; they include E. coli O157:H7, staphylococcus enterotoxins, ricin.
Category C agents are emerging threats that have the potential to quickly spread and become serious health threats; they include Nipah virus, hantavirus, and others

Anthrax (Bacillus anthracis)

Anthrax is a gram-positive, spore-forming bacillus, occurring in different forms (cutaneous, gastrointestinal, inhalational).
Cutaneous anthrax presents as a skin lesion evolving over 2-6 days, initially as a papule, progressing to a vesicle and a black eschar.
Gastrointestinal anthrax involves spores with an incubation period of 2–5 days, marked by nausea, vomiting, bloody diarrhea, and death. Mortality is about 50%
Inhalation anthrax involves spores, a brief prodrome resembling a viral respiratory illness, and radiographic evidence of mediastinal widening; flu-like symptoms, respiratory failure, and meningitis can develop. The mortality rate is high (50–80% untreated).

Plague (Yersinia pestis)

Plague is an acute bacterial infection spread mainly by fleas.
It can manifest in different forms (bubonic, septicemic, or pneumonic).
Bubonic plague is characterized by swollen lymph nodes (buboes) with flu-like symptoms.
Septicemic plague has symptoms similar to bubonic, with no lymph node swelling, and is marked by bloodborne organisms.
Pneumonic plague, marked by rapid transmission, fever, hemoptysis (coughing up blood), lymphadenopathy, and cough, has the highest mortality rate.
Specimens for plague include sputum, bronchial washings/aspirates, environmental samples, and fleas.
Gram-negative bacteria (GNR) identification includes safety pin appearance, slow growth, non-motile colonies on MacConkey agar (MAC) and slow growth in general.

Tularemia (Francisella tularensis)

Tularemia is a zoonotic infection spread to humans from animals (rabbits, ticks).
Its manifestations include localized swelling, ulcers, or a flu-like illness that spreads systemically
A person can contract tularemia through various ways including ticks, water-rats, or deer-flies
Specimens for tularemia analysis include serum, tissue, lesion aspirates, sputum, and environmental samples.
Identifying tularemia involves using pleomorphic, small gram-negative rods, slow growth, non-motile colonies on special media like SBA, CHOC, and MTM, and lack of oxidase, urea, or indole activity.

Brucellosis (Brucella species)

Brucellosis (Malta fever or undulant fever) is an infection that involves unpasteurized dairy products, or direct skin contact, often in occupations like farming or veterinary practices.
It exhibits a long incubation period (5 days - 6 months).
The characteristic symptoms can include fever, profuse sweating, malaise, and muscle/back pain and No person-to-person transmission, and mortality rate is less than 5 percent.
Specimens for analysis span blood, bone marrow, tissue, spleen, liver, and environmental or evidentiary material.
Identifying Brucella involves using slow-growing, aerobic bacteria that can be cultured on BAP and CHOC media exhibiting catalase, oxidase, and urea positivity.

Burkholderia Species (B. mallei and B. pseudomallei)

Burkholderia Species include B. mallei (glanders) and B. pseudomallei (meliodosis), transmitted through direct contact or occupational hazards; animal contact, and direct exposure.
These species have incubation times ranging from 1 to 2 weeks, presenting in different manners with cutaneous, systemic, or pneumonia-type symptoms.
Specimens include blood, bone marrow, sputum, bronchial alveolar lavage, abscess material, urine, and serum samples.

Q Fever (Coxiella burnetii)

Q fever is an infection caused by inhaling infected animals or their excretions.
Symptoms include a flu-like illness, pneumonia, and hepatitis.
The mortality rate is approximately 2%.
Specimens include blood, serum, body fluids, visceral tissue, biopsy, and autopsy samples.

Smallpox (Variola major)

Smallpox is an orthopoxvirus-borne disease involving a DNA virus.
It's now eradicated around the world, with only a couple labs holding reference specimens.
The virus has a brick-like structure, a relatively short incubation period (8 - 16 days), and is spread via droplets.
Clinical forms include ordinary smallpox (high mortality), modified smallpox, flat smallpox, and hemorrhagic smallpox.
Smallpox starts with flu-like symptoms and then develops a rash, spreading through the body, turning into raised lesions, and eventually scabs. Specimens, usually with the onset of the rash, would include materials collected from the lesions.

Botulism (Clostridium botulinum)

Botulism is a neuroparalytic illness from a toxin; characterized by different types of botulinum toxin.
Botulism can occur from food poisoning, wound infections, or infections from injected substances (like heroin).

Ricin

Ricin is a toxin derived from castor bean waste, occurring in various forms (mist, powder, pellets).
It is a remarkably stable substance, easily inhaled, or ingested, leading to significant morbidity.

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Description

Test your knowledge on the causes and characteristics of various infections, including decubitus ulcers, diabetic foot ulcers, and anaerobic infections. This quiz covers key features of microorganisms, culture methods, and associated conditions, providing a comprehensive review of clinical microbiology concepts.