mb w8 (fungi & protozoa infects)

Fungi and Fungal Infections

• Fungal structure and characteristics

• Yeasts, moulds, and dimorphism

• Fungal reproduction and classification

• Opportunistic fungal infections

• Oral candidiasis and predisposing factors

• Antifungal medications and their targets

Protozoa and Parasitic Infections

• Protozoan characteristics and classification

• Locomotion and life-cycle stages

• Transmission and prevention of protozoan infections

• Waterborne protozoan pathogens

• Malaria; Plasmodium species

• Water purification methods and limitations

Infection Control and Clinical Applications

• Principles of asepsis and infection prevention

• Dental unit waterlines and microbial contamination

• Microbial transmission and patient susceptibility

• Epidemiological terminology and basic calculations

• Application of microbiology to dental hygiene practice

characters & growth of fungi

• eukaryotic (true nucleus & membound orgs)

• lack chlorophyll → no photosynth

• chemoheterotrophs → get nutr from organic compounds

• absorb their nutr

• cell wall has chitin & complex polysaccs

• most grow best in slight acidic, aerobic environ

they may live as…

• saprophytes = obtain nutr from dead matter

• parasites = nutr from living host

• opportunistic pathogen = cause disease when host defenses weakened

• changes in local environ contrib to fungal overgrowth

types & reprod of fungi

1. yeast = unicellular

• unicellular

• round/oval

• reprod by budding

• ex: candida albicans

2. moulds= multicellular

• hyphae = braching filaments it forms

• reprod by forming spores

3. dimorphic fungi= exist as yeast/mould

• form depend on environ cond

• budding & spores

4. fungal spores= conidia

• conidia = asexual, nonmotile spores

• easy disperse in air

• can inhale in rep tract

• harmless to healthy

• opportunistic infect in immunocomp

• larger mushrooms = fleshy fungi

pathogenicity of fungi

• most dont prod exotoxins (prod by gram neg/pos bact) or endotoxins (outer mem of gram neg)

fungal infect often…

• slow growing

• chronic

• opportunistic

• spores carried by air/water to places suitable for germination + growth

Bact vs. Fungi

• antibiotics target bact structures

• ^cell wall (peptidoglycan) & bact ribosomes

• antifungals target fungal structs

• ^ergosterol & fungal cell mem

ANTIBIOTICS DONT TREAT FUNGAL INFECT

ribosomes = resp for protein synth

• svedberg unit (S) = rate of sedimentation during centrifugation (based on differences in structure)

bact ribosome = 70S

fungal ribosome = 80S

explains why some antibiotis can selectively target bacterial ribosomes

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Which characteristic best distinguishes fungi from bacteria?

A. Fungi contain peptidoglycan in their cell wall

B. Fungi are prokaryotic organisms

C. Fungi contain a true nucleus and membrane-bound organelles D. Fungi reproduce only by binary fission

Which fungal cell wall component is commonly targeted when distinguishing fungi from bacteria?

A. Lipopolysaccharide

B. Peptidoglycan

C. Chitin

D. Mycolic acid

A yeast differs from a mould because yeasts:

A. form hyphae

B. are multicellular

C. reproduce by binary fission only

D. are unicellular and reproduce by budding

A fungus obtains nutrients from decaying organic material. How would this fungus be classified?

A. Parasite

B. Opportunistic pathogen

C. Saprophyte

D. Dimorphic fungus

antifungal agents

polyene antifungals

• nyastatin

• amphotericin B

polyenes bind to ergosterol (fungal struct along fungal cell mem)

& disrupt the cell wall/membrane** destroy cell wall kill

azoles (imidazoles)

• miconazole

• clotrimazole

• fluconazole

azoles inhibit ergosterol synthesis**

• used to treat fungal infect like candidiasis

• these target fungal specific structures

Antifungal therapy = based on organism & site/severity of infect

Nyastatin (polyene antifungal) → for ORAL CANDIDIASIS

Miconazole/Clotrimazole (azole antifungal) → topical/local fungal infects

Fluconazole (azole antifungal) → systemic/more extensive Candida

Amphotericin B (polyene antifungal) → serious systemic fungal infect, signif toxicity

• some fungi show drug resistance (ex: candida auris)

Candida Albicans = opportunistic fungal pathogen

• normal commensal (org) in oral cav, GI, fem genital tract

• present in ~50% of healthy individuals

• usually endogenous (grow within cell/system) in origin

characts & virulence factors

• yeast that reprod by budding

• form pseudohyphae & hypahe → tissue invade

• adhere > tissue + denture → biofilm formation

• changes surf antigens → evade immune detect

• produce extracell enzymes (phospholipase, proteinase, haemolysin)

Candidiasis - type of infect

superficial presenting

• Oral thrush

• Erythematous candidiasis

• Hyperplastic candidiasis

• Angular cheilitis

• Skin and mucosal infections

treat w topical fungals

• nystatin

• clotrimazole

• miconazole

systemic (deep)

• Candida in bloodstream or organs

• Seen mainly in immunocompromised patients

systemic antifungals

• fluconazole

• amphotericin B

Candidiasis - common clinical forms

Pseudomembranous candidiasis (Thrush)**

• white plaque (can wipe)

• leave erythematous/bleeding surf

Erythematous candidiasis**

• red smooth depapillated tongue

• may involve hard palate

Angular chelitis**

• cracking and erythema at mouth corners

Hyperplastic candidiasis

• white NON removable plaque

Chronic mucocutaneous candidiasis

• persistent candida infects involving mucosa, skin, nail

Systematic Candidiasis (CANDIDA AURIS)**

• emerging yeast species

• cause human candidiasis

• assoc w healthcare setting & immunocomps

can cause invasive candidiasis (candidaemia) affecting…

• blood stream

• CNS

• internal orgs

important bc = frequently multidrug resistant

• difficult to identify & assoc w hospital outbreak

• serious opportunistic infect

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Cryptococcus Neoformans**

• encapsulated pathogenic yeast

• in soil contam by PIGEON DROPPINGS

• transmit = inhale (prim affect lungs)

• opportunistic for immunocomps

major virulence fact = thick polysacc capsule

• help evade host defence (like bact capsule)

• diagnose = culture & antigen testing

• treat = antifungal therap (amphotericin B & fluconazole)

review

Conidia are best described as:

A. bacterial spores

B. sexual reproductive organs of fungi

C. asexual fungal spores spread through air

D. fungal toxins

Candida albicans is considered an opportunistic pathogen because it:

A. always causes disease in healthy people

B. commonly causes infection after mosquito bites

C. normally exists as commensal flora but can overgrow when host defenses weaken

D. produces potent exotoxins

Which factor increases the risk of oral candidiasis?

A. Good salivary flow

B. Recent antibiotic therapy

C. Increased oxygen exposure

D. Low sugar intake

Which clinical form of candidiasis presents as white plaques that can be wiped away?

A. Hyperplastic candidiasis

B. Angular cheilitis

C. Pseudomembranous candidiasis

D. Erythematous candidiasis

Hyperplastic candidiasis differs from pseudomembranous candidiasis because the lesion:

A. is painful

B. involves the tongue only

C. wipes off easily

D. forms a non-removable white plaque

Cryptococcus neoformans is commonly associated with exposure to:

A. contaminated seafood

B. pigeon droppings

C. mosquito bites

D. untreated milk

Lichen Planus - NOT candidiasis

• chronic inflam mucocutaneous condition

• may affect oral mucosa + skin

• NOT FUNGAL, algal, or infectious

• immune mediated

oral features = white lacy lesions (Wickham striae)

• may be erosive/ulcerative

• can hurt

diagnose = clinical appearance, biopsy may be required

management = topical corticosteroids

• not infectious lesion like candidiasis

Fungal disease - Mycoses (get gist)

1. Superficial / Cutaneous

• Affect the skin, hair, or nails

• Examples: – Tinea (ringworm) – Cutaneous candidiasis (athlete foot)

2. Subcutaneous

• Involve deeper tissues beneath the skin

• Often enter through traumatic implantation

• Examples include infections caused by environmental fungi

3. Deep / Systemic

• Can spread to internal organs and tissues

• Often acquired through inhalation of fungal spores

• Examples: – Histoplasmosis – Cryptococcosis – Pneumocystis pneumonia (PCP_

Pneumocystis jirovecii fungus (PCP)

opportunistic infect in

• immunocomp

• AIDS ppl

• transplant recepients

transmission = airborne

pneumonia like symptoms = fever cough short breath

Apthous ulcer (canker sore) NOT FUNGAL

Which virulence factor helps Cryptococcus neoformans evade host defenses?

A. Exotoxin production

B. Thick polysaccharide capsule

C. Flagella

D. Endospore formation

Which statement about lichen planus is CORRECT?

A. It is caused by Candida species

B. It is highly contagious

C. It is considered an immune-mediated condition

D. It is treated with antibiotics

Athlete’s foot is classified as which type of fungal disease?

A. Deep mycosis

B. Systemic candidiasis

C. Cutaneous mycosis

D. Opportunistic protozoal infection

Pneumocystis jirovecii pneumonia (PCP) is most commonly associated with:

A. healthy adolescents

B. immunocompromised patients

C. food poisoning

D. skin trauma

Which medication is commonly used to treat Pneumocystis jirovecii pneumonia?

A. Fluconazole

B. Metronidazole

C. Trimethoprim-sulfamethoxazole (TMP-SMX)

D. Penicillin

Candida auris is clinically important because it is often:

A. harmless normal flora

B. spread by mosquitoes

C. multidrug-resistant

D. easily identified in laboratories

Protozoan Infections

• unicellular, eukaryotic, heterotrophic

• some are important human pathogens

can cause infect in…

• intestine, blood, lung, liver, brain

classified by

• mode of motility

• cell struct

found in

• water, marine environ, moist soil

feed on = bacteria, algae, other protozoa

typically lack

• cell wall

• photosynthetic pigments

Protozoa Stages

Trophozoite

• active motile feeding stage

• resp for growth & tissue damage

Cyst

• dormant protective stage (can still go to host)

• often the infective stage transmitted to human

• can convert back to trophozoite after ingest

Reprod

Asexual = fission or budding or schizogony (mult fission)

Sexual = (some) conjugation

Plasmodium & Malaria (aka #1 parasitic killer)

• plasmodium (parasitic protozoa) → cause malaria

asexual reprod occur in

• liver cells

• RBC

sexual in

• fem Anopheles mosquito

sporozoans

• complex life cycle

• parasitic protozoa

• gen non-motile when mature

• life cycle need mosquito vector & human host

5 species of Plasmodium

• P.malarie

• P.vivax (most common)

• P.falciparium (most deadly)

• P.ovale

• P.knowlesi

Malaria - transmission, symptom, management

transmit

• (prim) bite of infected fem anopheles mosquito

• (less common) blood, share needle, congenital

symptom

• in cycles every 2-3 days

• fever chills headache nausea sweating

diagnosis

• parasites idntified on thick or thick blood smears

• Giemsa stain

treat

• Artemisinin-based combination therapy (ACT)

• chloroquine in sensitive region

prev

• mosquito control

• vaccine avail in some places (partial protect)

• drug resistance is increasing

P.vivax (most common)

• most widespread outside africa

• can remain dormant in liver as hypnozoites

• can relapse (month/year) and reactivate if stress/immune supression

• global health prob (partic children)

P.falciparum (most deadly)

• fem mosquito inject sporozoites during blood meal

• parasite infect liver → then RBC

• some parasite taken up by another mosquito to contiue cycle

Vax

Leishmaniasis

• cause by leishmania species (protozoan parasite)

• visceral (kala-azar & black fever) most severe form

parasites invade

• liver, spleen, bone marrow

symptom

• fever, weight loss, anemia, enlarged spleen/liver

untreated fatal

Amoebas & Flagellates

photo

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review

Protozoa are best classified as:

A. prokaryotic bacteria

B. unicellular eukaryotes

C. multicellular fungi

D. obligate viruses

Which structure is primarily used by amoebas for movement and feeding?

A. Flagella

B. Cilia

C. Pseudopodia

D. Hyphae

Which pairing is correct?

A. Entamoeba histolytica — cilia

B. Giardia lamblia — flagella

C. Balantidium coli — pseudopodia

D. Trypanosoma — cilia

Immunocompromised

• some protozoan infect become more severe in immunocomp

• opportunistic protozoa can cause life threat disease to weak host

Protozoa opportunistic pathogens in AIDS are:

• Cryptosporidium parvum

• Entamoeba histolytica

• Giardia lamblia

• Cystoisospora belli

• Toxoplasma gondii

Trichomoniasis (trichomonas vaginalis)

• STD protozoan infect

• more common and symptomatic in fem

• bc of vag pH = acidic

symptom

• itch inflam

• frothy yellow green discharge

• irritate uncomfy

Assoc w inc risk of HIV infect

Intestinal Protozoan Infects

left out treatment

1. Amoebiasis

• org = entamoeba histolytica

• transmit = fecal-oral (ingest of cystin contam food/wat)

• site = large int (diarrhea w/ dysentery (blood) and when severe can cause liver abscess

2. Giardiasis

• org = giardia lamblia

• transmit = fecal-oral (ingest of cyst in food wat)

• site = duodenum/jejunum where watery diarrhea malabsorp

3. Cryptosporidiosis

• org = cryptosporidium parvum

• transmit = fecal oral (ingest oocyst in food/wat)

• site = GI tract (watery diarrhea)

Eyes Toxoplasmosis (protozoan infect)

• eti = toxoplasma gondii

• transmit = undercook meat, cat feces, cong transmission across placenta

• symptom = blurred vision, pain, photophobia, and exudative retinitis due to the protozoan multiplying and encysts in the retina. (typically seen in immunosuppressed) eyes

• dissemunated toxoplasmosis seen w inc freq in aids patients

A patient develops watery diarrhea, marked bloating and flatulence, and signs of malabsorption after drinking contaminated water. Which protozoan is the most likely cause?

A. Entamoeba histolytica

B. Giardia lamblia

C. Cryptosporidium

D. Balantidium coli

What is the primary mode of transmission for Giardia lamblia?

A. Respiratory droplets

B. Mosquito bites

C. Fecal–oral transmission through contaminated water or food

D. Direct skin contact

Which symptom is MOST characteristic of giardiasis?

A. Hemorrhagic rash

B. Watery diarrhea with bloating and flatulence

C. Paralysis

D. Productive cough

Which medication is commonly used to treat giardiasis?

A. Penicillin

B. Nystatin

C. Metronidazole

D. Ciprofloxacin

Entamoeba histolytica causes disease through ingestion of:

A. spores

B. trophozoites only

C. cysts in contaminated food or water

D. bacterial toxins

Which condition is strongly associated with invasive Entamoeba histolytica infection?

A. Otitis media

B. Liver abscesses

C. Meningitis

D. Pneumonia

Cryptosporidium parvum is clinically important because it:

A. is easily destroyed by chlorination

B. causes severe disease mainly in plants

C. is highly resistant to many disinfectants

D. only infects animals

wont ask like this ^

Which group is MOST at risk for severe cryptosporidiosis?

A. Healthy teenagers

B. Individuals with AIDS

C. Athletes

D. Patients with hypertension

Which symptom is commonly seen in cryptosporidiosis?

A. Bloody sputum

B. Watery diarrhea

C. Vesicular rash

D. Muscle paralysis

Toxoplasma gondii infection may occur after exposure to:

A. aerosolized fungi

B. contaminated needles

C. cat feces or undercooked meat

D. insect bites

Water assoc Pathogens

• contam water can cause disease thru ingest or inhale of contam aerosols

• DUWL (dental unit water line)

• biofilms in DUWL can accum & protect microorgs

• including opportunistic pathogens from disinfect

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3 process of water purif

1. Sedimentation

• allow larger particles to settle

• removes particulate matter before further treatment

2. Filtration

• phys removes smaller particles/microorgs

• membrane filtration can remove Giardia cysts & Cryptosporidium oocysts

3. Chlorination

• MOST COMMON CHEM DISINFECT

• effective against many microorg

• less effective against some protozoan cyst/oocyst

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Limitations

why not 100% effective

• some protozoan cyst/oocyst resistant to chlorination

• ^Giardia & Cryptosporidium

• ^mem filtration can phys remove these resistant forms

• water can become contam after treat (ex: pipe leak, groundwater contam, untreated water source)

• detection of giardia and crypto challenging

• testing may underestimate contam & dont determ whether orgs are infectious

• take sev days

Calculating infectivity, pathogenicity, & virulence

• all percentages

Infectivity = ability of pathogen to establish infect

infected ÷ exposed x 100

Pathogenicity = ability of infectious agent to cause disease

symptomatic ÷ infected x 100

Virulence = severity of disease among symptomatic ppl

severe death cases ÷ symptomatic x 100

ex:

100 ppl exposed

80 became infected

40 dev symptoms

5 die

infectivity = 80/100 = 0.8 x 100 = 80%

pathogenicity = 40/80 = 0.5 × 100 = 50%

virulence = 5/40 = 0.125 × 100 = 12.5%

Which statement regarding dental unit waterlines is CORRECT?

A. Biofilms cannot develop in waterlines

B. Biofilms may protect microorganisms from disinfection

C. Waterlines are sterile environments

D. Protozoa cannot survive in water systems

Which microorganism associated with water systems is linked to Legionnaires’ disease?

A. Giardia lamblia

B. Shigella spp.

C. Legionella pneumophila

D. Candida albicans

Which process physically removes particulate matter during municipal water purification?

A. Chlorination

B. Sedimentation

C. Oxidation

D. Pasteurization

Why is filtration an important part of water treatment when Giardia and Cryptosporidium are present?

A. They are resistant to all forms of filtration

B. Their cysts/oocysts may be relatively resistant to chlorination

C. Chlorination causes them to reproduce

D. They are viruses and cannot be chemically disinfected

Membrane filtration is particularly useful because it can remove:

A. viruses only

B. fungal hyphae only

C. Giardia cysts and Cryptosporidium oocysts

D. dissolved salts only

Why is chlorination alone sometimes insufficient for water purification?

A. Chlorine evaporates immediately

B. Protozoan cysts such as Giardia may resist chlorine

C. Chlorine only kills fungi

D. Chlorination increases protozoal growth

During an outbreak, 200 people were exposed to a microorganism. 120 people became infected 90 infected individuals developed symptoms 30 symptomatic individuals died What is the pathogenicity of the microorganism?

A. 15%

B. 25%

C. 75%

D. 90%