MMP 201: Bacteria of Medical Importance and Antigens

Overview

Conducted by: Stephen, David Adesoye, B.Sc (Ilorin), M.Sc (Ibadan), PhD in view (12/11/2025)

Staphylococcus aureus

Classification:
- Gram-positive
- Facultative anaerobic bacterium (grows under both aerobic and anaerobic conditions)
Mode of Infection:
- Infection occurs through entry via skin or body through:
- Cuts
- Scrapes
- Wounds
- Contaminated food
- Spread occurs through:
- Contact with pus from infected wounds
- Skin-to-skin contact with infected individuals
- Objects used by infected person (e.g., towels, sheets, clothing)
Mode of Treatment:
- Prevention with good hygiene practices
- Commonly prescribed antibiotics:
- Cefazolin
- Nafcillin
- Daptomycin
- Vancomycin

Escherichia coli

Classification:
- Predominant motile (flagellated) facultative anaerobic gram-negative rods
Diseases Caused:
- Extraintestinal illnesses in humans
- Urinary tract infections
- Abdominal and pelvic infections
- Pneumonia
- Meningitis
Metabolic Capability:
- Utilizes simple carbon sources (e.g., glucose, acetate)
- Capable of fermenting lactose and glucose
Habitat:
- Found in the intestines of infected humans and animals
- Present in water and certain foods
Symptoms of Infection:
- Diarrhea (often bloody)
- Vomiting
- Severe stomach cramps
Mode of Transmission:
- Not air- or surface-borne; spreads through consumption of contaminated foods:
- Raw or undercooked meat
- Raw milk
- Contaminated raw vegetables
Mode of Treatment:
- No current treatments to cure infection or prevent complications
- Symptomatic management includes:
- Rest
- Increased fluid intake to prevent dehydration
- Recommended antibiotics include:
- Azithromycin
- Cefixime
- Ceftriaxone
- Ciprofloxacin

Neisseria gonorrhoeae

Classification:
- Gram-negative coccus
- Causes gonorrhea (sexually transmitted disease)
Mode of Infection:
- Infects mucous membranes of reproductive tract:
- Cervix
- Uterus
- Urethra
- Fallopian tubes in women
Mode of Transmission:
- Spread through:
- Vaginal, oral, and anal sex
Symptoms:
- Pain or burning sensation when urinating
- Green or yellow discharge from male reproductive organs
Mode of Treatment:
- Can be cured with appropriate treatment
- Recommended treatment by CDC:
- Single dose of 500 mg ceftriaxone (intramuscular injection)

Salmonella Typhi

Classification:
- Gram-negative bacterium
- Responsible for typhoid fever
Mode of Infection:
- Infects intestinal tract, liver, spleen, and bloodstream
- Spread through:
- Food or water contaminated with S. Typhi
- Close contact with an infected person
Symptoms Include:
- High fever
- Headache
- Stomach pain
- Constipation
- Diarrhea
- Muscle aches
- Nausea
- Cough
Mode of Treatment:
- Many recover without specific treatment
- Severe cases require antibiotics:
- Ciprofloxacin
- Azithromycin
- Cefixime
- Carbapenems
- Increased fluid intake recommended; hospitalization may be needed for severe diarrhea

Shigella dysenteriae

Classification:
- Rod-shaped, Gram-negative, non-spore forming, facultative anaerobic, non-motile bacteria
Cause of Disease:
- Shigellosis
Mode of Infection:
- Transmission occurs from feces or soiled fingers to mouth (including during sexual activity)
- Reports of outbreaks among gay and bisexual men
Symptoms Include:
- Diarrhea (often bloody)
- Abdominal pain
- Stomach cramps
- Fever
Mode of Treatment:
- Treated with:
- Ciprofloxacin
- Azithromycin

Vibrio cholerae

Classification:
- Gram-negative, facultative anaerobic, comma-shaped bacteria
Cause of Disease:
- Cholera, an acute diarrheal infection
Mode of Infection:
- Caused by ingesting food or water contaminated with V. cholerae
- Contamination usually from feces of infected individuals
- Spread through consumption of raw or undercooked shellfish

Prevention of Cholera

Key Measures:
- Good hygiene practices
- Access to clean drinking water
- Sanitation facilities
- Hand washing before meals and after using the toilet
- Avoid eating exposed food

Treatment of Cholera

Primary Treatment:
- Replenishment of fluids and electrolytes due to dehydration
- Oral Rehydration Solution (ORS) recommended by WHO:
- Contains powders of salts and glucose that dissolve in clean water
- Antibiotics can also be used to reduce severity

Clostridium tetani

Classification:
- Rod-shaped, Gram-positive bacterium
- Causative agent of tetanus
Characteristics:
- Obligate anaerobic, saprophytic bacteria, known for toxin production
- Spore-forming organisms; resistant to heat and disinfectants
- Tetanus spores can survive for years in the environment

Mode of Infection:

Source:
- Most infections from wounds; also from:
- Burns
- Surgical abscesses
- Intravenous drug abuse
- Neonatal tetanus results from unsanitary umbilical cord cutting during delivery
Mechanism:
- Multiplication leads to release of tetanospasmin (neurotoxin), which interferes with signals from brain to spinal cord causing muscular symptoms

Symptoms of Tetanus

Muscle Symptoms:
- Spasms and stiffness (starts with chewing muscles)
- Lockjaw
- Spasms spreading to neck and throat, causing swallowing difficulties
- Breathing difficulties due to neck and chest tension
Other Symptoms Include:
- Bloody stools
- Diarrhea
- Fever
- Headache
- Sensitivity to touch
- Sore throat
- Sweating
- Rapid heartbeat due to neurotoxin effects

Prevention and Treatment for Tetanus

Wound Management:
- Clean all cuts or wounds thoroughly
- Tetanus-prone wounds require immediate medical attention
- Definition of a tetanus-prone wound:
- Surgical interventions delayed over 6 hours
- Extensive tissue removal
- Puncture wounds in contact with soil/manure
- Serious fractures with exposed bone
Post-Wound Care:
- Tetanus immunoglobulin (TIG) recommended for at-risk patients
- Contains antibodies to kill C. tetani
- Antimicrobials prescribed:
- Penicillin or metronidazole to prevent bacterial multiplication and toxin production
- Alternative for penicillin-allergic patients: Tetracycline

Muscle Spasms and Stiffness Management

Medications Prescribed:
- Anticonvulsants (e.g., Diazepam) to relax muscles and reduce anxiety
- Muscle relaxants (e.g., Baclofen) to suppress nerve signals and lessen tension
- Neuromuscular blocking agents (e.g., Pancuronium, Vecuronium) to block signals from nerves to muscles
Surgical Intervention:
- Debridement for large wounds to remove contaminated tissue

Vaccination for Tetanus

Immunization Schedule:
- DTaP vaccine routinely given to children:
- 5 shots:
  - 2 months
  - 4 months
  - 6 months
  - 15-18 months
  - 4-6 years
- Booster doses:
- Recommended between 11-18 years
- Every 10 years thereafter

Bacteria Antigens

Definition of Antigen:
- An antigen is any substance that causes an immune response in another organism. This response can include an increase of inflammatory factors or activation of the adaptive immune system leading to antibody production.
Antigen Types:
- Vary based on origin and immune response:
- Foreign to one's immune system
- Produced by infectious microorganisms within a host
- Produced by the host itself

Bacteria Antigens and Immune System

Role of Antigens:
- Antigens trigger immune responses, varied in shapes and sizes:
- Immunity:
- Ability of the body to fight infection
- The system responsible is the immune system
Primary Immune Cells:
- White blood cells, specifically lymphocytes (types of leukocytes produced in the bone marrow):
- B lymphocytes
- T lymphocytes
Function of Lymphocytes:
- Effective elimination of foreign substances from the body

Immune Response Mechanism

Initial Response to Antigens:
- Upon entering the body, antigens alert the immune system:
- B-Cells Role:
- B-lymphocytes tag intruding antigens
- They reside in bone marrow, activated upon antigen detection
Antibody Production:
- Upon tagging, B cells create antibodies that specifically lock onto antigens
- Chemical signals are sent to coordinate the immune response
Subsequent Immune Response:
- T cells take over, targeting and destroying the antigen
- Role of Phagocytes:
- Additional white blood cells that consume and eliminate antigens

Antibodies

Definition of Antibodies:
- Proteins produced by the immune system to neutralize antigens
- Post-production, antibodies remain ready for subsequent infections by the same antigen
Example:
- Chicken Pox virus: once antibodies are formed during the initial infection, they persist to combat future invocations of the virus.

Acknowledgment

Thank you for engaging with this material.

Overview

Conducted by: Stephen, David Adesoye, B.Sc (Ilorin), M.Sc (Ibadan), PhD in view (12/11/2025)

Staphylococcus aureus

Classification:
- Gram-positive, arranged in grape-like clusters
- Facultative anaerobic bacterium (grows under both aerobic and anaerobic conditions)
- Biochemical Characteristics: Catalase-positive and Coagulase-positive (distinguishes it from other Staphylococci)
Mode of Infection:
- Infection occurs through entry via skin or body through:
- Cuts
- Scrapes
- Wounds
- Contaminated food (causes rapid-onset food poisoning due to heat-stable enterotoxins)
- Spread occurs through:
- Contact with pus from infected wounds
- Skin-to-skin contact with infected individuals
- Objects used by infected person (e.g., towels, sheets, clothing)
Mode of Treatment:
- Prevention with good hygiene practices
- Commonly prescribed antibiotics (though resistance is common in MRSA strains):
- Cefazolin
- Nafcillin
- Daptomycin
- Vancomycin

Escherichia coli

Classification:
- Predominant motile (flagellated) facultative anaerobic gram-negative rods
- Serotypes: Includes specific pathogenic strains like O157:H7 which causes severe hemorrhagic colitis
Diseases Caused:
- Extraintestinal illnesses in humans
- Urinary tract infections (UTIs) — the most common cause globally
- Abdominal and pelvic infections
- Pneumonia
- Neonatal meningitis
Metabolic Capability:
- Utilizes simple carbon sources (e.g., glucose, acetate)
- Capable of fermenting lactose and glucose; produces a metallic green sheen on Eosin Methylene Blue (EMB) agar
Habitat:
- Found in the intestines of infected humans and animals
- Present in water and certain foods
Symptoms of Infection:
- Diarrhea (often bloody in EHEC infections)
- Vomiting
- Severe stomach cramps
Mode of Transmission:
- Not air- or surface-borne; spreads through consumption of contaminated foods:
- Raw or undercooked meat
- Raw milk
- Contaminated raw vegetables
Mode of Treatment:
- No current treatments to cure infection or prevent complications; antibiotics are often avoided in EHEC due to risk of Hemolytic Uremic Syndrome (HUS)
- Symptomatic management includes:
- Rest
- Increased fluid intake to prevent dehydration
- Recommended antibiotics for specific extraintestinal infections include:
- Azithromycin
- Cefixime
- Ceftriaxone
- Ciprofloxacin

Neisseria gonorrhoeae

Classification:
- Gram-negative diplococcus, often described as kidney or coffee-bean shaped
- Fastidious organism requiring nutrient-rich media like Thayer-Martin agar
- Causes gonorrhea (sexually transmitted disease)
Mode of Infection:
- Infects mucous membranes of reproductive tract:
- Cervix
- Uterus
- Urethra
- Fallopian tubes in women
Mode of Transmission:
- Spread through:
- Vaginal, oral, and anal sex
- Vertical transmission from mother to baby during childbirth (causing ophthalmia neonatorum)
Symptoms:
- Pain or burning sensation when urinating
- Green or yellow discharge from male reproductive organs
Mode of Treatment:
- Can be cured with appropriate treatment; however, antimicrobial resistance is a major concern
- Recommended treatment by CDC:
- Single dose of 500 mg ceftriaxone (intramuscular injection)

Salmonella Typhi

Classification:
- Gram-negative bacterium, aerobic and motile
- Responsible for typhoid fever, a systemic disease
Mode of Infection:
- Infects intestinal tract, liver, spleen, and bloodstream
- Spread through:
- Food or water contaminated with S. Typhi (fecal-oral route)
- Close contact with an infected person
Symptoms Include:
- High fever (often rising step-wise)
- Headache
- Stomach pain
- Constipation or "pea soup" diarrhea
- Muscle aches
- Rose spots (faint pink spots on the trunk)
Mode of Treatment:
- Many recover without specific treatment, but carriers may persist
- Severe cases require antibiotics:
- Ciprofloxacin
- Azithromycin
- Cefixime
- Carbapenems
- Increased fluid intake recommended; hospitalization may be needed for severe symptoms

Shigella dysenteriae

Classification:
- Rod-shaped, Gram-negative, non-spore forming, facultative anaerobic, non-motile bacteria
- Produces Shiga toxin, which inhibits protein synthesis in host cells
Cause of Disease:
- Shigellosis (bacillary dysentery)
Mode of Infection:
- Transmission occurs from feces or soiled fingers to mouth (including during sexual activity)
- Very low infectious dose (as few as 10 to 100 organisms can cause disease)
Symptoms Include:
- Diarrhea (frequently containing blood and mucus)
- Abdominal pain
- Stomach cramps
- Tenesmus (feeling the need to pass stools even when bowels are empty)
Mode of Treatment:
- Primarily hydration; antibiotics shorten the duration of shedding
- Treated with:
- Ciprofloxacin
- Azithromycin

Vibrio cholerae

Classification:
- Gram-negative, facultative anaerobic, comma-shaped bacteria with a single polar flagellum
- Serogroups: O1 and O139 are responsible for epidemics
Cause of Disease:
- Cholera, an acute diarrheal infection leading to rapid dehydration
Mode of Infection:
- Caused by ingesting food or water contaminated with V. cholerae
- Mechanism involves the Cholera Toxin (CT), which causes hypersecretion of water and electrolytes into the intestinal lumen
- Spread through consumption of raw or undercooked shellfish

Prevention of Cholera

Key Measures:
- Good hygiene practices
- Access to clean drinking water
- Sanitation facilities and proper sewage disposal
- Hand washing before meals and after using the toilet

Treatment of Cholera

Primary Treatment:
- Immediate replenishment of fluids and electrolytes
- Oral Rehydration Solution (ORS) recommended by WHO:
- Contains powders of salts (NaCl, KCl, Citrate) and glucose
- Antibiotics (e.g., Doxycycline) can be used to reduce stool volume and duration

Clostridium tetani

Classification:
- Rod-shaped, Gram-positive bacterium
- Causative agent of tetanus
Characteristics:
- Obligate anaerobic; appears as "drumsticks" due to terminal spores
- Spore-forming organisms; highly resistant to environmental stressors
Mechanism:
- Secretes tetanospasmin, a potent neurotoxin that blocks the release of inhibitory neurotransmitters (GABA and Glycine)

Mode of Infection

Source:
- Soil, dust, and animal manure
- Most infections from wounds, burns, or surgical abscesses
- Neonatal tetanus results from unsanitary umbilical cord care

Symptoms of Tetanus

Muscle Symptoms:
- Risus sardonicus (characteristic facial grin)
- Lockjaw (trismus)
- Opisthotonos (arching of the back due to muscle spasms)
Other Symptoms:
- High blood pressure and rapid heartbeat (autonomic instability)

Prevention and Treatment for Tetanus

Wound Management:
- Debridement: Surgical removal of dead or contaminated tissue
Post-Wound Care:
- Tetanus immunoglobulin (TIG) to neutralize unbound toxin
- Antibiotics: Penicillin G or Metronidazole

Vaccination for Tetanus

Immunization Schedule (DTaP):
- 5 doses given at: 2 months, 4 months, 6 months, 15-18 months, and 4-6 years
- Tdap booster recommended at 11-12 years and then Td boosters every 10 years

Bacteria Antigens

Definition of Antigen:
- Any substance (immunogen) that triggers an immune response. They contain specific sites called epitopes (antigenic determinants) that are recognized by antibodies.
Antigen Types:
- Exogenous Antigens: Entered the body from the outside (e.g., bacteria, viruses)
- Endogenous Antigens: Generated within cells due to normal metabolism or intracellular infection
- Autoantigens: Host proteins recognized as foreign in autoimmune diseases

Bacteria Antigens and Immune System

Components:
- Innate Immunity: Non-specific first line of defense
- Adaptive Immunity: Specific response involving memory
Primary Immune Cells:
- Lymphocytes (B and T cells)
- Phagocytes (Neutrophils and Macrophages) that engulf antigens

Immune Response Mechanism

B-Cells Role: Recognize antigens via B-cell receptors (BCR); differentiate into plasma cells to secrete antibodies
T-Cells Role:
- Cytotoxic T-cells (CD8^+): Directly kill infected cells
- Helper T-cells (CD4^+): Coordinate the immune response by releasing cytokines

Antibodies

Definition: Also known as Immunoglobulins (Ig), these are Y-shaped proteins that neutralize pathogens
Classes:
- IgM: Produced first during an infection
- IgG: Most abundant; provides long-term immunity and crosses the placenta
- IgA: Found in mucosal secretions (saliva, breast milk)

Acknowledgment

Thank you for engaging with this material.