Microbiology Quiz on Enterococci and Streptococci
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Questions and Answers

What are the nonenterococci members of Group D that colonize other animals and occasionally humans?

  • Enterococcus faecium
  • Streptococcus bovis (correct)
  • Streptococcus equinus (correct)
  • Enterococcus durans

    • In which population does E. faecalis infections commonly arise?

  • Young children
  • Immunocompromised patients
  • Pregnant women
  • Elderly patients undergoing surgery (correct)

    • What is the primary reason enterococci are considered emerging nosocomial opportunists?

  • They are resistant to all antibiotics.
  • Rising incidence of multidrug-resistant strains. (correct)
  • They are found in animal intestines.
  • They have virulence factors similar to more virulent streptococci.

    • What type of infections are most frequently caused by Streptococcus pneumoniae?

    <p>Bacterial pneumonias</p> Signup and view all the answers

    Where is Streptococcus pneumoniae commonly found as part of the human microbiota?

    <p>Nasopharynx</p> Signup and view all the answers

    What characteristic makes Streptococcus pneumoniae unique among other streptococci?

    <p>It was formerly called Diplococcus.</p> Signup and view all the answers

    What factors contribute to the virulence of viridans streptococci?

    <p>Most are opportunistic pathogens.</p> Signup and view all the answers

    What is a potential mode of transmission for Streptococcus pneumoniae infections?

    <p>Direct contact with respiratory secretions</p> Signup and view all the answers

    What is the most serious pathogen among the Staphylococcus species mentioned?

    <p>Staphylococcus aureus</p> Signup and view all the answers

    What is the typical carriage rate for Staphylococcus aureus in healthy adults?

    <p>20% to 60%</p> Signup and view all the answers

    Which of the following groups is most often associated with MRSA outbreaks?

    <p>Prison inmates</p> Signup and view all the answers

    What percentage of deaths in the U.S. is attributed to infections caused by staphylococci annually?

    <p>Approximately 80,000</p> Signup and view all the answers

    In what type of environments can Staphylococcus aureus be commonly found?

    <p>Human frequented environments</p> Signup and view all the answers

    Which species of Staphylococcus is primarily associated with opportunistic infections?

    <p>Staphylococcus epidermidis</p> Signup and view all the answers

    What is the typical arrangement of Staphylococcus bacteria?

    <p>In irregular clusters and short chains</p> Signup and view all the answers

    Staphylococcus aureus is a common cause of infections in which settings?

    <p>Newborn nurseries and surgical wards</p> Signup and view all the answers

    What characteristic makes yeasts more invasive than hyphal forms of fungi?

    <p>Yeasts grow more rapidly and spread through tissues</p> Signup and view all the answers

    Why is accurate and speedy diagnosis critical for the immunocompromised patient?

    <p>They require prompt antifungal chemotherapy to prevent death</p> Signup and view all the answers

    What is a characteristic of opportunistic fungal pathogens?

    <p>They require impaired host defenses to establish an infection.</p> Signup and view all the answers

    Which of the following specimens is NOT suitable for diagnosing mycotic infections?

    <p>Hair samples</p> Signup and view all the answers

    What is the dominant opportunistic pathogen associated with invasive infections?

    <p>Candida</p> Signup and view all the answers

    How do most fungal pathogens complete their life cycles?

    <p>They can reproduce independently in the environment.</p> Signup and view all the answers

    What is typically the most infectious component of fungi?

    <p>Spores</p> Signup and view all the answers

    What is the primary cause of candidiasis?

    <p>Candida albicans</p> Signup and view all the answers

    Where do the majority of primary mycoses enter the body?

    <p>Via respiratory routes from inhaled spores.</p> Signup and view all the answers

    Which method is NOT routinely used in laboratory procedures for fungal identification?

    <p>Chemical synthesis</p> Signup and view all the answers

    Which fungus is primarily associated with lung infections as an opportunistic pathogen?

    <p>Aspergillus</p> Signup and view all the answers

    Which factor significantly increases the virulence of certain fungi?

    <p>Thermal dimorphism that allows tolerance of body temperatures.</p> Signup and view all the answers

    What distinguishes true fungal pathogens from opportunistic ones?

    <p>True pathogens are distributed in predictable patterns based on environmental factors.</p> Signup and view all the answers

    Which of the following genera was once considered a harmless air contaminant but is now appearing more often in clinical isolates?

    <p>Torulopsis</p> Signup and view all the answers

    What type of routes do fungi typically enter the body through?

    <p>Respiratory, mucosal, and cutaneous routes.</p> Signup and view all the answers

    Which of the following is an example of a characteristic of opportunistic mycoses?

    <p>They may cause mild superficial diseases.</p> Signup and view all the answers

    What is a significant factor that predisposes patients to pneumonia?

    <p>Old age</p> Signup and view all the answers

    Which bacterium is primarily associated with epidemic cerebrospinal meningitis?

    <p>Neisseria meningitidis</p> Signup and view all the answers

    What historical confusion existed regarding gonorrhea?

    <p>It was confused with syphilis</p> Signup and view all the answers

    What is a cardinal manifestation of human brucellosis?

    <p>Undulant fever</p> Signup and view all the answers

    What is the primary pathogenic species of the Family Neisseriaceae?

    <p>Neisseria</p> Signup and view all the answers

    Which mechanism allows Brucella to survive within the host?

    <p>Ability to grow inside macrophages</p> Signup and view all the answers

    How does gonorrheal infection affect the male reproductive tract?

    <p>It can create scar tissue and blockage in sperm ducts</p> Signup and view all the answers

    Alcaligenes faecalis is primarily associated with which of the following?

    <p>Opportunistic infections</p> Signup and view all the answers

    Which of the following are characteristics of members of the Family Neisseriaceae?

    <p>Residents of mucous membranes</p> Signup and view all the answers

    What was the original belief about the cause of gonorrhea attributed to Claudius Galen?

    <p>An excess flow of semen</p> Signup and view all the answers

    Which characteristic differentiates coliforms from noncoliforms in the Enterobacteriaceae family?

    <p>Ability to ferment lactose</p> Signup and view all the answers

    During which season is the rate of pneumonia infection highest?

    <p>Winter</p> Signup and view all the answers

    What is the most prevalent species of Enteric Bacillus found in humans?

    <p>Escherichia coli</p> Signup and view all the answers

    Which of the following bacteria is primarily found in soil and water habitats?

    <p>Alcaligenes</p> Signup and view all the answers

    What describes the population proportion of E. coli relative to anaerobic bacteria in the human intestine?

    <p>1 to 9</p> Signup and view all the answers

    What is NOT a symptom associated with human brucellosis?

    <p>Weight gain</p> Signup and view all the answers

    Signup and view all the answers

    Study Notes

    Major Viral, Fungal, and Bacterial Diseases

    • This is a general topic covering various microbial diseases.
    • Learning objectives for the lecture are not detailed.

    Gram-Positive and Gram-Negative Cocci of Medical Importance

    • Staphylococcus aureus is a common inhabitant of skin and mucous membranes.
    • It is a primary cause of "staph" infections.
    • Staphylococcus cells are primarily arranged in irregular clusters.
    • Currently, 47 species exist in the genus Staphylococcus.
    • The most important human pathogens are S. aureus, S. epidermidis, S. capitis, S. hominis, and S. saprophyticus.
    • S. aureus is the most serious pathogen, implicated in significant human infections and nearly 80,000 deaths per year.
    • It also accounts for a substantial percentage of nosocomial infections.
    • Pathogenic gram-positive and negative cocci result in various infections. A table includes these various organisms and their corresponding infections (page 7).

    Epidemiology and Pathogenesis of S. aureus

    • S. aureus is surprisingly a common human associate, readily isolated from fomites.
    • The carriage rate of healthy adults ranges from 20% to 60%.
    • S. aureus is the third most frequent cause of infections for new-borns and those undergoing surgical procedures.
    • The rise of methicillin-resistant S. aureus (MRSA) is causing concerns about community-based infections, especially in prison inmates, athletes, and schoolchildren.

    Invasive Group A Streptococci and "Flesh-Eating" Syndrome

    • Streptococcal infections usually follow a routine, uncomplicated course.
    • Necrotizing fasciitis is a significant complication of S. pyogenes infection, also known as "flesh-eating disease."
    • The infection can begin with an innocuous cut and rapidly spread to nearby tissues, causing severe disfigurement and death.

    Beta-Hemolytic Streptococcus: Streptococcus pyogenes

    • Streptococcus pyogenes is the most severe streptococcal pathogen for humans.
    • It is a relatively strict pathogen inhabiting the throat, nasopharynx, and occasionally, the human skin.
    • The involvement of this species in severe human disease is due to multiple factors, including various surface antigens, toxins, and enzymes.
    • The prevalence in humans is 5-15%.

    Epidemiology and Pathogenesis of Streptococcus pyogenes

    • The bacteria gain a foothold primarily in the skin or pharynx, subject to environmental factors like climate and season.
    • Humans are the only significant reservoir.
    • Infection is usually transmitted through direct contact, droplets, or fomites.
    • A concern arose from the increase in community-based infections of a strain of S. aureus called MRSA. (methicillin-resistant S. aureus

    Streptococcus pneumoniae: The Pneumococcus

    • This is a significant pathogen.
    • It was formerly known as Diplococcus, given its genetic similarity to streptococci.
    • The infection is primarily in immunocompromised individuals.
    • Accounts for most bacterial pneumonitis.

    Epidemiology and Pathogenesis of the Pneumococcus

    • Most people who carry S. pneumoniae are part of their healthy microbiome in the nasopharynx.
    • Infection is frequently acquired endogenously from one's own microflora, although it can also be from direct contact with respiratory secretions or droplets.
    • Streptococcal pneumoniae is delicate and does not survive long outside its natural habitat.
    • Risk factors include age, other lung diseases, viral infections, and living in densely populated areas.

    Pathogen Profile #3: Streptococcus pneumoniae (pneumococcus)

    • The species is gram-positive, lancet-shaped cells arranged in pairs or short chains.
    • Gram staining and catalase tests can distinguish this species.
    • It resides in the nasopharynx of 5% to 15% of individuals.
    • The virulence factor is the capsule; nonencapsulated strains are avirulent.
    • Above 90 different capsular serotypes exist.

    The Family Neisseriaceae: Gram-Negative Cocci

    • Members of this family reside primarily in the mucous membranes of warm-blooded animals.
    • Most species are harmless commensals.
    • Neisseria genus is of significant clinical significance.

    Neisseria gonorrhoeae: The Gonococcus

    • Gonorrhea has been known as a sexually transmitted disease since ancient times.
    • It is caused by the bacterium Neisseria gonorrhoeae.
    • The bacterium is known in cultivation as the gonococcus that proves to be the sole etiologic agent for gonorrhea.

    Neisseria meningitidis: The Meningococcus

    • Neisseria meningitidis is a serious human pathogen.
    • Common cause of epidemic cerebrospinal meningitis.
    • Its reservoir of infection is humans harboring the bacterium in their nasopharynx.

    Epidemiology and Pathogenesis of Meningococcal Disease

    • The disease of Neisseria meningitidis has sporadic or epidemic incidence in late winter to early spring seasons.
    • Humans are the primary reservoir, with the pathogen harboring in the nasopharynx.
    • The secondary cause concerns the transmissibility to others.
    • It is the second leading cause of meningitis in adults after Streptococcus pneumoniae.

    Gram-Positive Spore-Forming Bacilli

    • Most spore-forming bacteria are gram-positive and rod-shaped.
    • The genera Bacillus and Clostridium contain endospores, dense survival units forming in vegetative cells in response to nutrient deprivation.
    • Their extreme resistance (to heat, drying, radiation, and chemicals) is of significant medical concern.
    • This creates a survival and longevity ecological niche for them, influencing their pathogenesis.

    Bacillus anthracis and Anthrax

    • Bacillus anthracis is a large, nonmotile rod with centrally located spores.
    • It can result from spores entering the body through accidental puncture wounds, burns, umbilical infections, frostbite, or crushed body parts.
    • It has exotoxins that produce edema and cell death.
    • It produces one of the most poisonous toxins found on Earth, millions of times more toxic than strychnine.

    Other Bacillus Species Involved in Human Disease

    • Bacillus cereus arises commonly as an airborne and dust-borne contaminant.
    • It multiplies in cooked food like rice, potatoes, and meat dishes.
    • Its spores are capable of surviving short periods of cooking and are the result of the food being stored at room temperature.
    • Enterotoxins are released by the germination of spores.
    • The symptoms are nausea, vomiting, and diarrhea and symptoms usually disappear within 24 hours
    • There is no specific treatment.

    The Genus Clostridium

    • Clostridium is another gram-positive, spore-forming rod genus.
    • It is differentiated from Bacillus as it is strictly anaerobic and catalase-negative.
    • Clostridia produce oval or spherical spores.
    • The spores develop only in anaerobic conditions.
    • Their complex nutrient requirements allow them to decompose a variety of substrates.

    The Role of Clostridia in Infection and Disease

    • Clostridial diseases span wound and tissue infections, including myonecrosis, antibiotic-associated colitis, tetanus; and food intoxications—those caused by Clostridium perfringens, type A; Clostridium botulinum
    • Potent exotoxins are responsible for the spectrum of diseases.
    • These toxins act on precise cellular targets and are extremely poisonous, many times more potent than strychnine or arsenic.

    Gas Gangrene/Myonecrosis

    • Clostridium perfringens, C. novyi, and C. septicum are the most common causes of tissue and wound infections.
    • Their spores are found in soil, on human skin, and in the human intestine and vagina.
    • The common name, gas gangrene, arises from the gas the bacteria produce in tissues.

    Tetanus, or Lockjaw

    • Tetanus is a neuromuscular disease, also known by lockjaw as it affects the jaw muscle.
    • The etiologic agent is Clostridium tetani, a common resident of cultivated soil and the gastrointestinal tracts of animals.
    • Spores usually enter the body via accidental puncture wounds, burns, umbilicus, frostbite, or crushed body parts.

    Clostridium difficile-Associated Disease (CDAD)

    • CDAD is a clostridial disease called antibiotic-associated (or pseudomembranous) colitis.
    • Clostridium difficile is a normal resident of the intestine.
    • Infection occurs when normal microbiota is disrupted, which can be brought about by antibiotic use.
    • Symptoms range from diarrhea to severe colon inflammation, perforation, and death.

    Other Bacillus Species Involved in Human Disease

    • Clostridium perfringens produces several exotoxins, including alpha toxin.
    • The toxins cause red blood cell rupture, edema, and tissue destruction.
    • The gas formed by fermentation of carbohydrates can also destroy muscle structure.

    Clostridial Food Poisoning

    • Two Clostridium species are involved in food poisoning:
    • Clostridium botulinum (severe intoxication usually from home bottled foods).
    • Clostridium perfringens (mild intestinal illness).

    Epidemiology of Botulism

    • Clostridium botulinum is a spore-forming anaerobe that commonly inhabits soil and water
    • Botulism is an intoxication often linked to canned or preserved foods.
    • It was once frequently fatal but modern techniques have reduced incidence and mortality rate
    • It causes disease through intoxication, usually from home-preserved foods, rather than direct infection.

    Botox: No Wrinkles, No Headaches, No Worries?

    • Botox is a medical form of botulinum toxin type A.
    • It's used for reducing wrinkle appearance.
    • It causes facial paralysis as a result of poorly targeted injections.

    Aerobic Gram-Negative Nonenteric Bacilli

    • The aerobic gram-negative bacteria of medical significance include soil bacteria, zoonotic pathogens, and bacteria mainly infecting humans.
    • Pseudomonas and Burkholderia; Brucella and Francisella; Bordetella and Legionella
    • Lipopolysaccharide (LPS) is a notable component found in the outer membrane of gram-negative bacteria cell walls.
    • It acts as an endotoxin
    • Gram-negative septicemias from LPS release can have a severe pathophysiological effect.

    Pseudomonas aeruginosa

    • A common inhabitant of soil, water, and even the human intestinal tract.
    • It can be isolated from saliva or even the skin.
    • It is resistant to common disinfectants, drugs, drying, soaps, and dyes.
    • A frequent contaminant of ventilators, IV solutions, and anesthesia equipment.

    Gram-Negative Sepsis and Endotoxic Shock

    • Gram-negative bacteria release endotoxins in the bloodstream, which causes significant pathophysiological effects.
    • Shock includes low blood pressure, diminished blood flow to vital organs (particularly brain, heart, and kidneys), nausea, rapid heartbeat, cold and clammy skin, a weak pulse.
    • Septic shock symptoms include circulation failure, tissue damage, hypotension, and shock.

    Burkholderia cepacia

    • Burkholderia cepacia is a common isolate from moist environments.
    • It plays an important ecological role in controlling fungal diseases on plants and is also active in biodegradation of toxic substances.
    • It has the potential to cause opportunistic infections in the respiratory, urinary, and occasionally skin tissues.

    Burkholderia pseudomallei

    • Burkholderia pseudomallei is a relative of B. cepacia.
    • It resides in soil and water of tropical climates.
    • Chronic infection of B. pseudomallei may progress through septicemia, endotoxic shock, and abscesses in organs like the liver and brain.

    Stenotrophomonas maltophilia

    • A prominent clinical isolate found in respiratory, blood, spinal fluid, and ophthalmic specimens.
    • It's commonly associated with respiratory, blood, and/or ophthalmic specimens.

    Brucella and Brucellosis

    • Brucella enters via damaged skin or mucous membranes
    • It is primarily implicated in the digestive tract, conjunctiva, and respiratory tract.
    • Infected macrophages transport the pathogen into the bloodstream, creating focal lesions in the liver, spleen, bone marrow, and kidneys.
    • The major symptom is undulant fever.

    Bordetella pertussis

    • Bordetella pertussis causes whooping cough.
    • The species is gram-negative and nonmotile.
    • The pathogen involves inhaling spores into the air and forming into fungus balls in the lungs; these can also infect the sinuses, ear canals, and conjunctiva.
    • Primary infections are generally self-limiting, but in 40% of those infected, the disease will progress to more severe cases.
    • Complications include compromised respiration.

    Coliform Organisms and Diseases

    • Coliforms are gram-negative bacteria that ferment lactose rapidly (within 48 hours).
    • The Enterobacteriaceae family is divided into two categories, Coliforms (which ferment lactose rapidly) and Noncoliforms.
    • Escherichia coli is the best-known coliform, frequently used as an indicator of fecal contamination in water, food, and dairy products.
    • It's frequently used as a laboratory study subject.

    Escherichia coli: The Most Prevalent Enteric Bacillus

    • Escherichia coli is the most prevalent coliform.
    • It is frequently used as a laboratory study subject.
    • Although it is one of the most prevalent colon bacteria, E.coli is outnumbered by strictly anaerobic bacteria.

    The Six Pathotypes of E. coli

    • Enterohemorrhagic E. coli (EHEC) causes hemorrhagic colitis and may lead to hemolytic uremic syndrome (HUS).
    • Enterotoxigenic E. coli (ETEC) causes a severe diarrheal illness.
    • Enteroinvasive E. coli (EIEC) is similar to dysentery, caused by Shigella.
    • Enteropathogenic E. coli (EPEC) is linked to infantile diarrhea.
    • Enteroaggregative E. coli (EAEC) causes diarrhea by aggregating and colonizing the intestinal mucosa.
    • Diffusely adherent E. coli (DAEC) is a minor cause of pediatric diarrhea.

    Clinical Diseases of E. coli

    • Most E. coli diseases are transmitted exclusively among humans.
    • Infantile diarrhea is a major cause of death worldwide (15% of childhood deaths).
    • Infection rates are high in crowded tropical regions where sanitation is poor.

    The Role of Escherichia coli in Food Infections

    • A specific strain of E. coli (O157:H7) is most often associated with foodborne diseases from hamburgers.
    • Some infections occur through direct contact or fomites, etc

    Miscellaneous Infections

    • Escherichia coli frequently invades locations other than the intestine—causing 50-80% of urinary tract infections in healthy adults.
    • The short male urethra facilitates ascending infection to the bladder (cystitis) and kidneys in women.

    E. coli and the Coliform Count

    • E. coli is a common resident of the intestine and a good indicator for fecal contamination in water, food, and dairy products.
    • Its presence frequently indicates the potential presence of other pathogens, including protozoa.

    Pathogen Profile #4: Escherichia coli

    • This is a common inhabitant of the digestive tracts of all warm-blooded animals.
    • It possesses a capsule and LPS endotoxin, and individual serotypes possess additional virulence factors, including the fimbriae, and toxins (heat-labile (LT) and heat-stable (ST)) that stimulate increased secretion and fluid loss.
    • An enteroinvasive disease of the large intestine that result in a significant degree of inflammation in the intestine
    • The species accounts for roughly 70% of traveler's diarrhea.
    • Some strains have a higher degree of virulence leading to more severe complications like enteroinvasive disease, ulceration of the large intestine, and in rare instances, hemolytic uremic syndrome (HUS).

    True Enteric Pathogens: Salmonella and Shigella

    • The salmonellae and shigellae are separated from the coliforms and Proteus group.
    • Developed virulence factors are present.
    • Not considered normal intestinal inhabitants in humans.
    • Resulting diseases are diarrhea, gastrointestinal infections, and sometimes other infections.

    Typhoid Fever and Other Salmonelloses

    • Typhoid fever is named for its superficial resemblance to typhus, a rickettsial disease
    • It is a relatively significant bacterial disease caused by S. typhi.
    • Salmonella serotype Paratyphi also causes paratyphoid, a similar disease,

    Shigella and bacillary dysentery

    • Shigella species are primarily human pathogens.
    • The infections can vary in intensity but are marked by fever, nausea, and abdominal cramps.
    • Frequent diarrhea characterizes the disease with bloody or mucus-containing stools, typical of bacterial dysentery.

    Pathogen Profile #5: Salmonella typhi, Salmonella enterica

    • This profile focuses on S. typhi and related species' role in human disease, primarily typhoid fever.
    • A significant characteristic of this species are both double- and single-stranded DNA.
    • The most common type in reported cases is S. enterica.
    • The pathogen is primarily identified by its gram reaction, morphology, and biochemical/serological tests.

    Pathogen Profile #6: Shigella sonnei, S. flexneri, S. boydii

    • Shigella is a primary pathogen of humans.
    • Shigellosis, the clinical disease, results from Shigella invasion and inflammation of the large intestine.
    • The bacterium can be detected via microscopic morphology, Gram reaction, biochemical test, differential tests, and also through the identification of their toxin-associated characteristics.

    Pathogen Profile #7: Yersinia pestis

    • Yersinia pestis is the etiologic agent of plague and also the causative agent of the bubonic, septicemic, and pneumonic plague forms of the disease.
    • The primary reservoirs of this species are rodents.
    • The infection primarily affects humans as a result of the bite of an infected flea or the handling of infected animals.
    • The disease commonly occurs through inhalation of droplets.
    • Treatment with antibiotics is recommended for the disease to improve long-term survival.

    Miscellaneous Bacterial Pathogens

    • Various bacteria cause a variety of diseases.
    • Specific infections are accompanied by symptoms and signs affecting multiple systems.
    • A table presents a summary of the organisms, related infections, and impacted systems. (page 109)

    Fungi of Medical Importance

    • A wide spectrum of fungi can cause diseases in humans.
    • Primary/true fungal pathogens can invade and survive in a healthy host.

    Primary/True Fungal Pathogens

    • Primary fungal pathogens' behavior is contrary to the metabolism and adaptation of fungi
    • They are able to survive and multiply in a warm-blooded animal.
    • They have a striking adaptation characterized by a switch from hyphal cells to yeast cells.

    Emerging Fungal Pathogens

    • Opportunistic fungal pathogens are different from primary fungal pathogens. They have minimal invasive qualities that require compromised host defenses for survival and multiplication.
    • There is an absence of a predictable geographical distribution.
    • The species has both mycelial and yeast phases in its life cycle.

    Epidemiology of the Mycoses

    • Most fungal pathogens lack host requirements for completion of their life cycles.
    • These pathogens are mostly not communicable but can be transmitted, for instance, by dermatophytes.

    Pathogenesis of the Fungi

    • Fungal infections involve complex interactions among various aspects.
    • They enter through respiratory, mucous, and cutaneous routes.

    Diagnosis of Mycotic Infections

    • Correct and timely diagnosis for mycotic infections is critical.
    • Immunocompromised individuals' needs are prioritized for prompt care to avoid severe complications such as death in infections that affect multiple organs.
    • Suitable specimens are chosen for the patient's level of symptoms, such as sputum, skin scrapings, biopsies, cerebrospinal fluid, blood, tissue exudates, urine, or vaginal samples.
    • Diagnostic procedures typically include isolation of the pathogen, microscopic examination, macroscopic examination, histological staining, serology, animal inoculation, and genetic testing.

    Pathogen Profile #1: Histoplasma capsulatum

    • It is a dimorphic fungus.
    • It is endemic in the Ohio and Mississippi River valleys and other areas.
    • The predominant fungal pathogen isolated from soil.
    • It resides within macrophages and reproduces inside phagocytic cells.

    Pathogen Profile #2: Coccidioides immitis

    • It is a dimorphic fungus endemic to areas with high aridity and elevated temperatures.
    • The pathogen produces tiny spores that are easily airborne, resulting in infection.
    • It is commonly isolated from soil and decaying vegetation.
    • It has a predisposition toward infection for people who live in or visit endemic regions.
    • Infection through inhalation generally causes a localized infection in the lungs but can cause spread to other organs and tissues.

    Pathogen Profile #3: Blastomyces dermatitidis

    • It is a dimorphic fungus, endemic to the eastern United States, specifically related to moist soils, decaying wood, and animal manure.
    • It primarily afflicts immunocompromised individuals, and the infection can occur through inhalation and may affect other tissues besides the lungs.

    The Dermatophyte Genera and Diseases

    • This table details dermatophytes, their pathogenic mechanisms, and the resulting symptoms in humans.

    Opportunistic Mycoses

    • Candida, Aspergillus, Cryptococcus, Alternaria, Paecilomyces, Fusarium, Rhizopus, and Torulopsis are opportunistic fungi commonly isolated (previously considered harmless contaminants).
    • Their presence can lead to the most pervasive invasive infections.

    Infections by Candida: Candidiasis

    • Candida albicans is the major cause of candidiasis, a fungal infection.
    • Infection ranges from superficial skin irritations to severe systemic diseases.
    • Localized infections occur in areas such as the oral cavity, throat, and other moist areas of skin.

    Pathogen Profile #4: Candida albicans

    • A widespread yeast, frequently a commensal in humans, but can become pathogenic.
    • It can exist as yeast or pseudohyphae in various anatomical locations.
    • It can be transmitted with fomites and through direct contact.

    Aspergillosis: Diseases of the Genus Aspergillus

    • Aspergillosis is a fungal disease resulting from mold Aspergillus species.
    • The pathogen is widely distributed and is frequently isolated from dust, air, and compost matter.
    • It is more common in immunocompromised individuals.
    • Respiratory infections are common—causing infections in the lungs in particular.

    Mucormycosis

    • Mucormycosis, also known as zygomycosis, is a common infection caused by molds in the genera Rhizopus, Mucor, and Absidia.

    Systems Profile 22.1: Fungal Pathogens

    • A table summarizes various fungal pathogens and their associated diseases and affected systems. (page 144)

    Viruses that Infects Humans: The DNA Viruses

    • This section introduces DNA viruses that infect humans.
    • Viruses are composed of RNA or DNA encased in a protein coat.
    • They rely on the host cell's machinery to replicate and release new viruses.

    Pathogenic DNA Viruses

    • This table details various DNA viruses, tissues they affect, and symptoms experienced. (page 148)

    Enveloped DNA Viruses: Poxviruses

    • Poxviruses cause eruptive skin pustules called pocks
    • Smallpox and vaccinia are examples.
    • They form sites (factory areas) for viral multiplication in the cytoplasm, which gives rise to pox lesions.

    Classification and Structure of Poxviruses

    • Poxviruses are large, complex animal viruses that infect the cytoplasm of epidermal cells in the epithelium in particular.

    Smallpox: A Perspective

    • The causative agent of smallpox is variola.
    • Characteristic of poxviruses, lesions produce skin eruptions followed by pocks or scars.

    Enveloped DNA Viruses: The Herpesviruses

    • Herpesviruses are characterized by a tendency for the resulting rashes to spread.
    • The different viruses in the Herpes family are associated with various diseases:
      • Herpes simplex viruses (HSV) 1 and 2 (fever blisters, genital infections)
      • Varicella-zoster (chickenpox, shingles)
      • Epstein-Barr virus (EBV)
      • Human herpesviruses (HHV) 6 and 7 (roseola)
      • Herpesvirus 8 (KSHV) (Kaposi sarcoma)

    Herpes Simplex Virus 1 and 2 (HSV-1, HSV-2): Pathogens

    • Herpes simplex viruses (HSV) types 1 and 2 cause a disease termed herpes, characterized by cutaneous, oropharyngeal, or genital lesions.
    • HSV-1 usually affects the oropharynx area, whereas HSV-2 primarily affects the genitalia.
    • Both can result in neonatal herpes.

    Life-Threatening Complications of Herpes

    • Herpes simplex encephalitis, a rare but serious complication of HSV-1 infection.
    • Initial infection and viral dissemination along nerve pathways reaching the brain and spinal cord, where it triggers a range of symptoms and signs.
    • Untreated cases have high fatality rates, typically exceeding 70%.

    Herpetic Whitlows

    • Herpetic infections of fingers and hands, specifically among those in the dental and medical personnel professions is a very painful disease occurring from infection with HSV.

    Diagnosis of Herpesvirus Infections

    • Herpesviruses are diagnosed by observing the clinical presentation of the affected tissues, such as a scraping of lesions or stained specimens.

    Pathogen Profiles: Hepatitis B Virus (HBV)

    • HBV is commonly transmitted in blood (or blood products), leading to liver infection.
    • It can remain infective in dried blood or serum at room temperature or for several months in frozen samples.

    The Viral Agents of Hepatitis

    • The causative agents for hepatitis are typically viruses.
    • Symptoms include jaundice and can progress to severe liver damage or cancer.

    Viruses That Infects Humans: The RNA Viruses

    • This section covers RNA viruses that infect humans.
    • RNA viruses are composed of RNA molecules encased in a protein coat.
    • They multiply using their host cells genetic machinery.

    Enveloped Segmented Single-Stranded RNA Viruses

    • Orthomyxoviruses, specifically influenza viruses, are spherical particles with a segmented single-stranded RNA genome.
    • The virus has three distinct types (A, B, and C), with type A causing the most cases of human infection.

    Emerging Avian Influenza Viruses

    • The 2003 H5N1 strain, an avian influenza virus (bird flu) caused a high mortality rate.
    • 2013 H7N9 appeared in Chinese patients, causing significant outbreaks in Asia and some parts of the world.

    Pathogen Profile #1: Influenza virus

    • Influenza is a significant respiratory illness.
    • It results from the death of ciliated cells in the respiratory tract.
    • Symptoms include fever, headaches, myalgia (muscle pain)

    Morbillivirus (Measles Virus)

    • Results in a maculopapular rash, a characteristic symptom, accompanied by fever and other symptoms.
    • It develops within 10 to 12 days.

    Rhabdoviruses

    • The rhabdoviruses are a family of bullet-shaped viruses.
    • The rabies virus, one of the most notable rhabdoviruses, has a helical nucleocapsid and spikes.

    Epidemiology of Rabies

    • Rabies is a progressive, often fatal zoonotic disease affecting mammals, particularly canids, skunks, raccoons, cats, and bats.
    • It is characterized by a fatal meningoencephalitis.

    Severe Acute Respiratory Syndrome-Associated Coronavirus

    • A novel coronavirus emerged in humans in 2003, leading to the disease called SARS.
    • This disease causes severe acute respiratory illness.
    • The causative agent was sequenced and identified as a novel type of coronavirus,
    • The epidemic was contained in 2003 but caused significant outbreaks in multiple regions.

    Pathogen Profile #3: Epstein-Barr virus (EBV)

    • EBV causes mononucleosis, a disease marked by sore throat, high fever, and cervical lymphadenopathy.
    • It leads to a gradual decline in CD4 cells which can result in serious complications like Burkitt lymphoma or nasopharyngeal carcinoma
    • EBV infection is carried by the lymphoid tissue and salivary glands in most people (90%)

    The Viral Agents of Hepatitis

    • There are several viruses involved, including HAV (Hepatitis A virus), HBV (Hepatitis B virus), and HCV (Hepatitis C virus), all known to affect the human liver.

    Pathogen Profile #4: Hepatitis B virus (HBV)

    • HBV typically causes an initial infection that typically lasts 2-7 weeks.
    • It can also lead to chronic liver disease and cancer.
    • Symptoms often include the onset of jaundice, liver disorder, soreness, fever, etc.

    Nonenveloped Single-Stranded DNA Viruses: The Parvoviruses

    • B19 is a common infectious disease among children that sometimes causes a distinctive 'slapped cheek' rash.
    • The virus is spread through bodily fluids like saliva and droplets.

    Papilloma- and Polyomaviruses

    • The distinction between papillomaviruses and polyomaviruses: both have circular DNA and cause persistent infections and tumors but differ in size and genome composition.

    Epidemiology and Pathology of the Human Papillomaviruses

    • Papillomaviruses are responsible for warts.
    • Common forms include common warts, plantar warts, and genital warts.
    • Different strains affect different tissues (common warts on fingers and toes).
    • An associated risk is cancer development.

    Pathogen Profile #5 Human papillomavirus (HPV)

    • HPV causes various lesions, including common and plantar warts as well as genital warts
    • It is a common feature of all infections.
    • The pathogen may persist within epithelial cells along with integration into the genome leading to an increased risk of cancer.

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