Microbiology Hub

Introduction to Microbiology and Common Microorganism

By Arvind Sharma, B.Pharm, M.Pharm, Assistant Professor, MUIT

Introduction to Microbiology and Common Microorganisms

1.1 What is Microbiology?

Microbiology is the branch of science that studies microscopic living organisms (microorganisms) — those too small to be seen with the naked eye.Think of it as 'the study of the tiny world that affects our health every day.'Simple Definition: Micro = small | Bio = life | Logy = study → Study of small life forms

1.2 Types of Microorganisms

MNEMONIC: "BPFVAP"
B – Bacteria (e.g., TB, cholera, typhoid)
P – Protozoa (e.g., malaria, amoeba)
F – Fungi (e.g., ringworm, candida)
V – Viruses (e.g., COVID-19, HIV, measles)
A – Algae (mostly harmless, rarely cause disease)
P – Parasites/Helminths (e.g., roundworm, tapeworm)

Microorganism	Cell Type	Example	Disease Caused
Bacteria	Prokaryote	Mycobacterium tuberculosis	Tuberculosis (TB)
Virus	Non-cellular (acellular)	SARS-CoV-2	COVID-19
Fungi	Eukaryote	Candida albicans	Oral thrush
Protozoa	Eukaryote	Plasmodium falciparum	Malaria
Helminths	Eukaryote (multicellular)	Ascaris lumbricoides	Ascariasis (worm)

1.3 Beneficial vs Harmful Microorganisms

Not all microorganisms are harmful! Many are essential for life.

Beneficial: Lactobacillus (in yogurt/gut), Nitrogen-fixing bacteria (soil), Yeast (bread/beer)
Harmful (Pathogens): Cause infections, diseases, and epidemics

Pharmacist Connection: Pharmacists must understand microorganisms to counsel on antibiotics, vaccines, hygiene, and infection prevention.

1.4 Bacterial Structure (Easy Overview)

Cell wall – gives shape and is the target of antibiotics like Penicillin
Cell membrane – controls what enters/exits the cell
DNA – genetic material (no nucleus in bacteria)
Flagella – helps bacteria move
Pili – helps bacteria attach to surfaces (important in infection)

MNEMONIC: "CWMDP = Can We Make Delicious Pastry?"
C – Cell wall
W – Wall membrane
M – Material (DNA)
D – Displace by Flagella (movement)
P – Pili (attachment)

1.5 Virus Structure (Key Points)

Viruses are NOT cells — they are simpler than bacteria
They have: Genetic material (DNA or RNA) + Protein coat (Capsid)
Some have an outer lipid envelope (e.g., HIV, Influenza, COVID-19)
Viruses can only reproduce INSIDE a host cell

Why important?: Soap destroys lipid envelopes of viruses like COVID-19. That's the science behind handwashing!

1.6 Normal Flora of Human Body

Our body has millions of bacteria that live on us normally and protect us — called Normal Flora.

Skin: Staphylococcus epidermidis
Gut: E. coli, Lactobacillus
Mouth: Streptococcus viridans

Tip: When antibiotics kill normal flora, harmful organisms like Candida can overgrow — causing 'superinfection.'

Epidemiology: Introduction and Key Terms

2.1 What is Epidemiology?

Epidemiology is the study of how diseases spread in populations — who gets them, when, where, and why — so we can prevent and control them.
Simple analogy: If a disease is a fire, epidemiology is the investigation that finds the source, tracks where it spread, and puts it out.

2.2 Key Epidemiological Terms (Must Know!)

Term	Simple Definition	Example
Epidemic	Sudden increase of a disease in a specific area/population beyond normal expected levels	COVID-19 in Wuhan city (2019)
Pandemic	Epidemic that spreads worldwide across countries and continents	COVID-19 (declared pandemic March 2020)
Endemic	Disease that is constantly present at a normal/expected level in a specific area	Malaria in parts of Africa, India
Outbreak	Sudden occurrence of a disease in a specific small community/area (smaller than epidemic)	Food poisoning at a school canteen
Quarantine	Restricting movement of people EXPOSED to a disease (but not yet sick)	Keeping COVID contacts at home for 14 days
Isolation	Separating people who ARE ALREADY SICK from others	COVID-positive patient in hospital room
Incubation Period	Time between exposure to pathogen and appearance of first symptoms	COVID-19: 2–14 days
Contact Tracing	Finding people who came in contact with an infected person to monitor/test them	Tracing COVID close contacts
Morbidity	The rate of people who become ILL due to a disease in a population	Morbidity rate of dengue in Kerala 2023
Mortality	The rate of DEATHS caused by a disease in a population	COVID-19 mortality rate: ~2%

MNEMONIC: "EE POQi ICM = 'Every Epidemic Produces Questions: Isolation Controls More'"
E – Epidemic
E – Endemic
P – Pandemic
O – Outbreak
Q – Quarantine
i – Isolation
I – Incubation period
C – Contact tracing
M – Morbidity & Mortality

2.3 Applications of Epidemiology

Identify causes (etiology) of disease outbreaks
Measure the magnitude of disease in population
Plan and evaluate health programs and interventions
Identify risk factors for diseases
Guide vaccination and preventive strategies
Monitor disease trends and emerging infections

Pharmacist Role in Epidemiology: Pharmacists report adverse drug reactions, unusual prescription patterns, and support surveillance. They are frontline workers during outbreaks.

2.4 Mode of Transmission

How does disease spread from one person/source to another?

Direct Transmission

Person to person contact (touching, kissing, sexual contact)
Droplet spread (sneezing, coughing within 1 meter)
Direct contact with soil (tetanus)

Indirect Transmission

Vehicle-borne: contaminated food, water (cholera, typhoid)
Vector-borne: through insects (mosquitoes – malaria, dengue)
Air-borne: droplet nuclei suspended in air (TB, COVID-19)
Fomite-borne: contaminated objects like doorknobs, utensils

MNEMONIC: "DVAFo = 'Diseases Visit After Flying over'"
D – Direct contact
V – Vehicle-borne (food/water)
A – Airborne
F – Fomite-borne
o – (Vector-borne) Organism/insect

Communicable Diseases – Respiratory Infections

3.1 Introduction

Respiratory infections spread mainly through droplets (sneezing, coughing) or airborne particles. They are among the most common causes of illness worldwide.

Chickenpox (Varicella)

Causative Agent: Varicella-Zoster Virus (VZV)
Mode of Transmission: Droplet spread; direct contact with rash/blisters (highly contagious)
Incubation Period: 14–21 days
Clinical Features: Fever, then itchy blister-like rash (starts on chest/back, spreads to face and limbs). Crops of blisters at different stages.
Prevention: Varicella vaccine (2 doses); avoid contact with infected persons; keep child home until all blisters have crusted

Pharmacist Role: Counsel parents to vaccinate children; advise calamine lotion for itching; warn not to use aspirin (risk of Reye's syndrome); educate on when to return to school

Measles (Rubeola)

Causative Agent: Measles Virus (Paramyxovirus family)
Mode of Transmission: Highly airborne — can linger in air for 2 hours after infected person leaves room
Incubation Period: 10–14 days
Clinical Features: 3 Cs: Cough, Coryza (runny nose), Conjunctivitis (red eyes). Then high fever and red rash spreading from face downward. Koplik spots (white spots inside mouth) — pathognomonic.
Prevention: MMR vaccine at 9 months and 15 months (India schedule); vitamin A supplementation

MNEMONIC: "3 Cs of Measles = 'Can Cats Run?'"
C – Cough
C – Coryza (runny nose)
C – Conjunctivitis (red eyes)

Pharmacist Role: Counsel on MMR vaccination; explain Koplik spots for early identification; promote vitamin A for children in deficiency areas

Rubella (German Measles)

Causative Agent: Rubella Virus (Togavirus family)
Mode of Transmission: Droplet spread; direct contact
Incubation Period: 14–21 days
Clinical Features: Mild fever, swollen lymph nodes (especially behind ears), pink-red rash starting on face. VERY DANGEROUS in pregnancy — causes Congenital Rubella Syndrome (CRS): deafness, blindness, heart defects in baby.
Prevention: MMR vaccine; women should be vaccinated before pregnancy

🔑 Pharmacist Role: Critical: Educate pregnant women and women of childbearing age to get vaccinated BEFORE pregnancy. Counsel that vaccination is safe pre-pregnancy but NOT during pregnancy.

Mumps

Causative Agent: Mumps Virus (Paramyxovirus)
Mode of Transmission: Droplet spread; direct contact
Incubation Period: 16–18 days
Clinical Features: Fever, headache, then painful swelling of parotid (salivary) glands — 'chipmunk cheeks.' Can cause orchitis (testicular swelling) in males — may lead to infertility.
Prevention: MMR vaccine

Pharmacist Role: Advise MMR vaccination; counsel parents that orchitis (in adolescent males) is a complication that needs immediate medical attention

Influenza (Flu)

Causative Agent: Influenza Virus (Types A, B, C) — Type A most severe
Mode of Transmission: Droplet spread; airborne; contaminated surfaces
Incubation Period: 1–4 days
Clinical Features: Sudden onset: high fever, severe body aches, headache, dry cough, sore throat. Different from common cold — much more sudden and severe.
Prevention: Annual flu vaccine (virus mutates yearly); hand hygiene; masks; avoid crowded places during flu season

Pharmacist Role: Promote annual flu vaccination (especially elderly, pregnant women, healthcare workers); dispense antiviral oseltamivir (Tamiflu) within 48 hours of symptoms; educate on flu vs cold differences

Special Influenza Variants

Disease	Pathogen	Key Feature	Pharmacist Tip
Avian Flu (H5N1)	Influenza A H5N1	Spread from birds to humans. High mortality (~60%). No easy human-to-human spread.	Advise avoiding contact with sick birds; report unusual deaths in poultry
Swine Flu (H1N1)	Influenza A H1N1	2009 pandemic. Spread human-to-human. Pregnant women at high risk.	Oseltamivir is drug of choice; vaccinate high-risk groups
SARS	SARS-CoV-1 (Coronavirus)	2002–2003 outbreak. Severe pneumonia; 10% mortality. Spread by droplets.	Advise isolation; no specific antiviral; supportive care
MERS	MERS-CoV (Coronavirus)	Middle East Respiratory Syndrome. Spread from camels to humans. ~35% mortality.	Advise against contact with camels in affected areas
COVID-19	SARS-CoV-2	2020 pandemic. Droplet + airborne spread. Variants (Delta, Omicron). Range from asymptomatic to death.	Vaccination (primary + booster); masks; handwashing; dispense antivirals per guidelines

Diphtheria

Causative Agent: Corynebacterium diphtheriae (bacterium)
Mode of Transmission: Droplet spread; direct contact with discharge
Incubation Period: 2–5 days
Clinical Features: Sore throat, fever, and formation of a GREY PSEUDOMEMBRANE on the tonsils/throat that can block airway (life-threatening). Also produces toxin affecting heart and nerves.
Prevention: DPT vaccine (Diphtheria, Pertussis, Tetanus); treatment with antitoxin + antibiotics (penicillin/erythromycin)

Pharmacist Role: Emphasize DPT vaccination in children; recognize pseudomembrane as emergency; counsel complete antibiotic course

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