Infectious Diseases

SHORT QUIZ   

After the lecture Closed notes ¼ piece of paper

Pathology - Diseases 

Non-Infectious Diseases   



Inflammatory Vascular Tumor

Infectious Diseases 

By an infectious agent  Microorganism  Microbiology

Microbiology Edgel May C. Bayag, M.D.

Microbial Groups 

Prions  Proteins Viruses  Nucleic Acids (DNA & RNA)



Prokaryotes







Bacteria

Eukaryotes  

Fungi Parasites

Prions  



Noncellular infectious proteins Naked proteins with the same amino acid sequence as certain normal cellular proteins, but are folded differently Subacute Spongiform Encephalopathies 



Creutzfelt-Jakob Disease

Cannibalism

Prion Gains Entry into Human Cells 

Modify the folding of normal PrPc



Turn proteins into additional prions



Eventually neurologic degeneration

Prions Sites of Replication & Transport

Viruses 

Obligate intracellular organisms 



Noncellular  





take over host cells use the viral nucleic acid to direct the synthesis and assembly of viral components make new virus

RNA or DNA 



cannot be grown outside host cell

various proteins

Envelope 

may or may not have

Viral Structure 

Viral Genomes 



Proteins 



Structural and Enzymes

Viral Nucleocapsid (Genomic nucleic acid + proteins) 



DNA or RNA

Icosahedral or Helical

Naked or Enveloped 

(host’s membrane as an envelope)

Viral Replication     

Infection thru Viral Binding Early Macromolecular Synthesis Replication of Genome Assembly Release

Bacteria  





Prokaryotic cells Complex cell walls of peptidoglycan (except for Mycoplasmas) No sterols (except in Mycoplasma membranes) Divide asexually or binary fission

Staining Property & Cell-Envelope Features:   

Gram Positive Gram Negative Poorly or Non-Gram Staining (Acid fast, Obligate Intracellular, No peptidoglycan, Weakly GramNegative)

Shapes 

Coccus 



Bacillus 

 

round rod

Spirilla Spirochetes   

spiral-shaped Thin Do not show up well in light microscopy

O2 requirement: Aerobes and Anaerobes (aerobic respiration or fermentation) 

Obligate aerobes (Tube1) 



Anaerobes (ABCs) (Tube2)   



Grow better with O2

Microaerophilic bacteria (Tube4) 



Actinomyces Bacteroides Clostridium

Facultative anaerobes (Tube3) 



aerobic respiration

require O2 at low levels

Aerotolerant Anaerobe (Tube5) 

Do not need O2 for Growth

Pathogens vs Commensals 

Disease-causing bacteria 



pathogens or parasites

Commensals    

normal flora colonizes the human body’s internal and external surfaces low virulence kept in balance by our surface defense mechanisms

Normal Flora 

1. Reduce the risk of pathogen colonization   



modifying pH blocking binding sites producing antibacterial compounds (bacteriocins)

2. Infection from normal flora  

carried into normally sterile tissues (trauma) immunocompromised patients

BACTER Skin IUM

Conjunctiva

Nose

Pharynx Mouth

Lower GI

Ant. ure- Vagina thra

Staphylococcus epidermidis (1)

++

+

++

++

++

+

++

++

Staphylococcus aureus* (2)

+

+/-

+

+

+

++

+/-

+

Streptococcus mitis

+

++

+/-

+

+

Streptococcus salivarius

++

++

Streptococcus mutans* (3)

+

++

Enterococcus faecalis* (4)

+/-

+

++

+

+

+

+

+

+

+

++

+

+

++

+

+/-

+/-

+

Streptococcus pneumoniae* (5) Streptococcus pyogenes* (6) Neisseria sp. (7)

+/+/-

+/+

Neisseria meningitidis* (8) Enterobacteria ceae*(Escheric hia coli) (9)

+/-

+/-

++ = nearly 100 percent +/- = rare (less than 5%)

+/+/-

+/+

+ +

++

+

+ = common (about 25 percent) * = potential pathogen

+

BACTER Skin IUM

Conjunctiva

Nose

Pharynx Mouth

Lower GI

Ant. ure- Vagina thra

Proteus sp.

+/-

+

+ +/-

+ +/-

+ +

+ +/-

+

+/-

+

+

+

Bacteroides sp.*

++

+

+/-

Bifidobacteriu m bifidum (12)

++

Pseudomonas aeruginosa* (10) Haemophilus influenzae* (11)

+

Lactobacillus sp. (13) Clostridium sp.* (14)

++

++

+/-

++

Clostridium tetani (15)

++

+/-

Corynebacteri a (16)

++

Mycobacteria

+

+

++

+

+/-

+/+ + +

Actinomycetes Spirochetes Mycoplasmas

++ = nearly 100 percent +/- = rare (less than 5%)

+ + ++ +

+

+

+

+

++ +

+/-

+ = common (about 25 percent) * = potential pathogen

+

+

Pathogenicity  

a. Survival in the Environment b. Colonization of the human body 

   

By normal flora & pathogens

c. Traumatic implantation into the human host d. Evasion of the Immediate host defense system e. Production of toxins f. Intracellular Growth

Fungi  

Eukaryotic organisms Complex carbohydrate cell walls 



chitin, glucans, and mannans

Fungal membranes  

Ergosterol as the major sterol treatment with  

   

imidazoles polyene drugs

Yeasts Filamentous molds Dimorphic fungi Mushrooms

Structures    

Hyphae (filamentous cells) Yeasts (oval to spherical cells replicate by budding) Dimorphic fungi (cold/mold  yeast in body) Pseudohyphae (buds remain attached and elongate  look like hyphae with constrictions at each cell-cell juncture)

Parasites  

Eukaryotic cells Protozoans, Worms, and Insects 



Sterols in their cell membranes 





Live on other organisms

do not have cell walls

Organism that lives in or on another organism (the host) Does some damage to the host in the process

Types of Parasites 

Facultative 



Obligate 



can live in association with its host or separately cannot live free of the host for at least some stage of the life cycle

With Complex Life Cycle 

requires more than one host

Hosts: organisms that provide nutrition and place for the parasite to replicate 

Reservoir host – maintains a parasite and may be the source for human infection. An essential reservoir host is one without which the parasite cannot exist



Intermediate host – either maintains the asexual stages of a parasite or allows development of the parasite to proceed only to the larval stage



Definitive host – which the adult or sexual parasites develop

Vectors: biological systems that spread parasites 

Biological vector  



vector and host for the replicative stage of a parasite Anopheles mosquito in malaria

Mechanical vector   

transmits parasite without being a host flies “tracking” Chlamydia trachomatis from one eye to the next)

Major Groups 

Protozoa 



Roundworms 



Amebas, Flagellates, Plasmodium Ascaris, Enterobius

Flatworms 

Flukes, Tapeworms

Quiz 

1-5. What are the 5 major microbial groups that cause infectious diseases?



6.Which of the microbial groups are noncellular infectious proteins?



7. Which among the microbial groups are obligate intracellular organisms with either DNA or RNA as their genome?



8. What component of the prokaryotic cell wall that determines whether it is gram positive or negative?



9. What is the sterol that composes the fungal membrane?



10. What is the biological system that spread parasites?

Infectious Diseases Edgel May C. Bayag, M.D.

By Organ System         

Eye and Ear Infections Respiratory Tract Infections Nervous System Infections Gastrointestinal and Hepatobiliary Diseases Cardiovascular Infections and Septicemia Bone or Joint Infections Genitourinary Tract Infections Cancers with Infections Skin and Subcutaneous Infections

1. Eye and Ear Infections 

Stye (hordeolum) 



Conjuctivitis 



S.aureus (red eye)

Acute otitis media

2. Respiratory Tract Infections 

Upper Respiratory Tract Infection, Bronchitis, Pneumonia

Pneumonia

3. Nervous System Infections 

Meningitis, Brain Abscesses, Encephalitis, Neurotoxins by microbes, Prion disease

4. Gastrointestinal and Hepatobiliary Disease 

 



Vomiting and Diarrhea by Ingestion of Microbial Toxin Noninflammatory Diarrhea (Virus) Inflammatory diarrhea and dysentery (Ameba) Hepatobiliary Disease (Ascaris, Schistosoma)

Dehydration in Diarrhea & Vomiting

5. Cardiovascular Infections; Septicemias; and Blood Cell Changes in Infection  

Native valve endocarditis, Pericarditis, Myocarditis Septicemia & Shock

6. Bone or Joint Infections 

Septic Arthritis, Osteomyelitis

7. Genitourinary Tract Infections   

Cystitis Blood in Urine Reproductive Tract Infections

8. Skin and Subcutaneous Infections; Rashes           

Surgical wounds or carbuncles, Furuncles Dermatitis, Impetigo, Tetatus Infection, Cellulitis   Rash Chickenpox Measles Shingles Scarlet fever Slapped cheek fever Exanthem subitum Neisseria meningitidis (meningococcemia and meningitis)

Tetanus

Furuncle

Carbuncle

Dermatitis

Measles (Rubeola)

Slapped-Cheek Rash

Scarlet Fever Rash

Chickenpox (Varicella Zoster)

Shingles (Herpes Zoster)

Exanthem Subitum (Roseola)

Meningococcemia

9. Cancers Associated with Infections 

Viruses    

 

Cervical Ca – HPV Burkitts lymphoma – EBV Liver ca – Hepa B&C Human T-cell Leukemias or lymphomas – HTLV

  Parasites  

Bladder Ca – Schistosoma hematobium Burkitt’s Lymphoma - Plasmodium

Disease Patterns & Transmission Edgel May C. Bayag, M.D.

Disease Patterns 

Acute 



Chronic 



Short and sharp course

Long duration and slow progression

Latent   

Not manifest but potentially discernible Period of apparent inactivity From the time stimulus is presented until a response occurs

Transmitted in two ways 

Horizontal disease transmission  

one individual to another in the same generation peers in the same age group  



direct contact (licking, touching, biting) indirect contact (vectors or fomites without physical contact)

Vertical disease transmission   

from parent to offspring mother transmits the disease bodily fluid, breast milk

Disease Transmission 

Droplet contact 



Direct physical contact 



coughing or sneezing on another person

touching an infected person, including sexual contact

Indirect contact 

touching soil contamination or a contaminated surface

Disease Transmission 

Airborne transmission 



Fecal-oral transmission 



microorganism remain in the air for long periods

contaminated food or water sources

Vector borne transmission 

insects or other animals

Locus Point on the body where a pathogen enters 

Droplet contact and other Airborne transmission 



Direct physical and Indirect contact  



wound in the skin mucous membrane

Fecal-oral transmission 



respiratory system

mouth

Vector borne transmission 

bite or sting of the vector

Diseases by Droplet Contact          

Bacterial Meningitis Chickenpox Common cold Influenza Mumps Strep throat Tuberculosis Measles Rubella Whooping cough

Diseases by Viral Droplet Nuclei      

Common cold Influenza A & B Mumps Measles Rubella SARS

Viral Droplet Nuclei 



When viruses are shed by an infected person through coughing or sneezing into the air, the mucus coating on the virus starts to evaporate Once this mucus shell evaporates the remaining virion is called a droplet nucleus or quanta

Diseases via Fecal-Oral Transmission     

Cholera Hepatitis A Polio Rotavirus Salmonellosis

Fecal-Oral Transmission  

Direct contact is rare in this route, for humans at least. More common are the indirect routes; 



foodstuffs or water become contaminated (by people not washing their hands before preparing food, or untreated sewage being released into a drinking water supply) the people who eat and drink them become infected

Diseases thru Sexual Transmission      

HIV/AIDS Chlamydia Genital warts Gonorrhea Hepatitis B Syphilis

Sexual Transmission 

Disease that can be caught during sexual activity with another person, including vaginal or anal sex or (less commonly) through oral sex

Diseases thru Oral Sexual Transmission  

HIV Herpes Simplex Virus 1

Diseases thru Oral Transmission   

Cytomegalovirus infections Herpes simplex virus (especially HSV-1) Infectious mononucleosis

Diseases by Direct Contact    

Athlete's foot Impetigo Syphilis Warts

Transmission by Direct Contact    

Diseases that can be transmitted by direct contact are called contagious Contagious is not the same as Infectious All contagious diseases are infectious, Not all infectious diseases are contagious

Diseases by Vertical Transmission   

HIV Hepatitis B Syphilis

Vertical Transmission 

This is from mother to child, often in utero, as a result of the incidental exchange of bodily fluids (mostly blood) during childbirth or (rarely) through breast milk.

Diseases by Iatrogenic Transmission 

Creutzfeldt-Jakob Disease 



Injection of contaminated human growth hormone

MRSA infection 

Acquired as a result of a stay in hospital

Iatrogenic Transmission 



Transmission due to medical procedures, such as injection or transplantation of infected material. Some diseases that can be transmitted iatrogenically include:

Diseases by Vector-borne Transmission  

Dengue Malaria

Vector borne transmission 

A vector is an organism that does not cause disease itself but that transmits infection by conveying pathogens from one host to another

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