Microbial Pathogens and Infections
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Questions and Answers

The dengue virus multiplies inside a mosquito before being transmitted to a human.

False

Chikungunya virus is transmitted by the same species of mosquito as the malaria parasite.

False

Malaria parasites are transmitted when an infected mosquito bites a human, injecting the parasite into their bloodstream.

True

Tuberculosis is caused by a viral infection that primarily targets the lungs.

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

A persistent cough, chest pain, and weight gain are common symptoms of tuberculosis.

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

Membrane disrupting toxins are mainly secreted by staphylococci and streptococci.

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

Leukocidins target and destroy red blood cells.

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

Hemolysins are toxins that target and kill white blood cells.

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

Superantigens are antigens that trigger a mild immune response.

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

Exotoxins are typically produced by pathogenic bacteria.

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

The uterus and its contents are typically sterile until just before labor.

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

Normal flora is introduced during the birthing process due to the handling of the infant.

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

Exotoxins are always active when they are secreted.

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

Normal microbiota provides an advantage to the host by promoting the growth of pathogens.

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

The A chain of an exotoxin is responsible for binding to and entering the target cell.

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

Exotoxins can only damage blood cells.

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

A lower pH in the vagina usually inhibits the growth of Candida albicans.

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

An increase in vaginal pH, towards pH 7 is not associated with vaginitis.

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

Superantigens are toxins that can disrupt the cell membrane.

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

Commensalism is a symbiotic relationship where both organisms benefit.

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

Staphylococcus epidermis living on the surface of the skin is an example of a mutualistic relationship.

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

Botulinum toxin is commonly known as 'Botox' and is used for cosmetic purposes.

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

Endotoxins are toxins that are released when a cell is healthy.

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

Exotoxins can be inactivated by heat and formaldehyde.

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

1mg of botulinum toxin is enough to kill 10,000 guinea pigs.

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

The composition of endotoxins includes lipopolysaccharides, which are part of Gram-positive cell walls.

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

The A-B toxins are a specific type of exotoxin.

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

Endotoxins are secreted from live cells into the environment.

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

Botulinum toxin is harmless in small doses for cosmetic applications.

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

Exotoxins stimulate the immune system to produce antitoxins.

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

Study Notes

Microbe-Human Interactions

  • This lecture explores the fascinating world of microbes and their interactions with humans
  • The lecture discusses the diverse world of microbes, their roles in maintaining health and causing disease, and the microbiome's influence on various aspects of human well-being.
  • The community of microorganisms is explored

Infectious Disease Resurgence in Malaysia

  • Infectious diseases, previously considered under control, are making a comeback in Malaysia.
  • The presentation explores trends, causes, and challenges associated with this resurgence.

Dengue Fever: A Persistent Threat

  • An infected Aedes mosquito transmits dengue virus.
  • The virus replicates in the body, causing symptoms like fever, headache, and muscle pain.
  • Infected people transmit the virus to other mosquitoes, perpetuating the cycle.

Common Infection Diseases in Malaysia

  • Dengue remains the number one infectious disease in Malaysia, with 71,641 cases in 2023.
  • Other common infectious diseases include Tuberculosis (19,430 cases) , Hand, Foot, and Mouth Disease (HFMD) (26,030 cases), food poisoning (11,281 cases), and measles (6,646 cases).
  • The spread of these diseases is sometimes attributed to foreign workers

Chikungunya: The Comeback Virus

  • An infected Aedes mosquito transmits the Chikungunya virus.
  • The virus replicates in the body, causing symptoms like fever, and joint pain.
  • The infected person transmits the virus to other mosquitoes through bites.
  • Treatment includes Rest, Fluids, Analgesic, Antipyretics, and Non-steroidal anti-inflammatory drugs

Malaria: Combating a Global Scourge

  • An infected female Anopheles mosquito transmits malaria parasites.
  • The parasites develop within the mosquito, reaching the salivary glands.
  • Infected mosquitoes transmit parasites to humans through bites.
  • Treatment options are based on malaria parasite resistant medicine, and the disease's severity.

Tuberculosis: Tackling a Resurgent Disease

  • Tuberculosis (TB) is a bacterial infection primarily affecting the lungs.
  • Transmission occurs via airborne droplets when an infected person coughs, sneezes, or speaks.
  • Symptoms include persistent cough, chest pain, fever, and weight loss.
  • Treatment involves a course of antibiotics like Isoniazid, Rifampicin, Pyrazinamide, Ethambutol, and Streptomycin .

Tuberculosis (Incidence)

  • A graph shows a rising incidence of Tuberculosis per 100,000 people from 2005 to 2016 in Malaysia.

Objectives

  • The objectives listed explain the relationships between microorganisms, the host, and pathogens.
  • The objectives also describe the occurrence and severity of different diseases.
  • Factors that influence the spread of infections are described.
  • The mechanism associated with pathogenesis is described.

Where Do Bacteria Live in My Body

  • Bacteria are present in various parts of the body, excluding specific organs.
  • Examples of locations include the mouth, nasal cavity, under the armpits, stomach, intestines, genitourinary tract, within joints and under the toenails.

Commensal Microbes Coexisting with Humans

  • Skin microbes protect against pathogens and maintain skin health.
  • Gut microbes aid digestion and regulate immune function.
  • Respiratory microbes prevent harmful pathogen colonization and contribute to immune system development.
  • Microbe presence and growth can lead to sickness.

Pathogenic Microbes: Causing Disease

  • Pathogens invade host tissues, multiply, and cause harm.
  • Pathogens damage host cells using mechanisms including toxins, enzymes, and other damaging factors.
  • Some pathogens evade host immune systems to prolong infection.

The Human (Microbiome)

  • The gut microbiome supports digestion and nutrient absorption, influences metabolism, and impacts overall health.
  • Skin microbiome acts as a barrier against pathogens, maintains skin integrity.
  • Respiratory microbiome supports immune functions and lung health.
  • Vaginal microbiome maintains a healthy environment and prevents infections.

Maintenance of the Normal Resident Flora

  • The normal flora plays a crucial role for maintaining a healthy human.
  • The normal microflora creates a protective environment.
  • The normal microflora prevents infections and improves the host's defenses.
  • There are different species of bacteria in different parts of the body.

Relationship between Normal Microbiota and the Host (good microbes)

  • Normal microbiota benefit the host by preventing the overgrowth of pathogens.
  • Normal microbiota can help prevent pathogens by competing for nutrients.
  • Conditions such as pH and available oxygen are affected.

Relationship between Normal Microbiota and the Host: Terms

  • Commensalism occurs when one organism depends on the other without causing any harm.
  • Mutualism occurs when both organisms benefit from the relationship.

Opportunistic Microorganisms

  • Microorganisms like E. coli are harmless in the large intestine but can cause disease when located in other body sites.
  • Opportunistic pathogens cause diseases in different body sites or in immunocompromised individuals.
  • Examples include urinary tract infections, pulmonary infections, and wound abscesses.

Quick Recap of the First Objective

  • Residents and commensals are normal microflora.
  • Transient microbes occupy the body for a short period.
  • All internal organs and fluids are free of microbes.
  • Lactobacilli, Bifidobacteria, and E. coli are common resident flora in the large intestine.
  • E. coli is an opportunistic pathogen in the urinary tract.
  • There is a symbiotic (both beneficial to each other) relationship between resident flora and the host.

Objectives (Microbes and Human Interactions)

  • The objectives concentrate on the occurrence, severity, and patterns of infections associated with various diseases including diseases originating from microorganisms.

Occurrence of a Disease

  • Infection happens when pathogenic microorganisms enter and multiply within host tissues causing diseases including damage or disruption to tissues and organs.
  • Incidence measures the number of new cases within a certain period.
  • Prevalence measures the total number of cases regardless of when they began.

Epidemiologist's Bathtub

  • The bathtub diagram shows the relationship involving incidence of new cases, prevalence, and mortality.

Frequency of Occurrence to Classify Disease

  • Sporadic diseases occur occasionally.
  • Endemic diseases are constantly present in a particular population. (Examples: Common cold).
  • Epidemic diseases occur in high numbers in a geographical are, within a relatively short period. (examples: COIVD19).
  • Pandemic diseases are diseases that involve widespread worldwide spread.

Occurrence of a Disease (Common Coronaviruses)

  • Common coronaviruses include 229E, NL63, OC43, and HKU1, and they appear regularly.
  • Infectious disease incidents like SARS-CoV (2002), MERS-CoV (2013), and COVID-19 (2019) have occurred.

Reproduction Number (R0)

  • Basic reproductive number (R0) is an expected number of secondary cases produced during the infection by one infected person in a susceptible population.
  • It applies to unvaccinated populations, and is used to assess the susceptibility of a person to an infection.
  • Measles has a relatively high R0 (R0 =15), meaning that one infected person can spread it to an average of 15 other people.

R0 (Infection)

  • If R0 is above 1, the number of cases increases as the infection spreads; conversely, when R0 is below 1, the epidemic ends.

Malaysia has Successfully Reduced the R0 Value

  • The conditional movement control order (CMCO) in Malaysia has helped reduce the infectability rate (R0).
  • Projections suggest that without the CMCO, the daily case count of Covid-19 would be above 1000.

Patterns of Infection (host involvement)

  • Mixed infections involve simultaneous growth of multiple microbes at a site (polymicrobial).
  • A primary infection is the initial infection, potentially superseded by a secondary infection caused by different microorganisms.

Patterns of Infection

  • Acute infections have rapid onset, severe effects, and short duration.
  • Chronic infections progress slowly and persist for an extended period.
  • Vaccination against infectious diseases can help reduce their occurrence.
  • Herd immunity occurs when a large portion of a community develops immunity, protecting those who haven't.

Patterns of Infection (localized infection)

  • Localized Infections: microbe enters the body and confines to a specific tissue. (examples: Boils or abscesses)
  • Systemic infections: infection spreads to several sites and fluids usually in the bloodstream. (examples: Measles and influenza).
  • Focal infections: when an infectious agent breaks loose from the initial infection site and spreads elsewhere. (examples: infections originating from tonsils or sinuses.)

Stages of Infection

  • Incubation period: time between initial infection and emergence of symptoms, where pathogen multiplies at the portal of entry; interval could last anywhere from several hours to years.
  • Prodromal period: short-term, early symptoms; period of illness onset. (e.g., headache, muscle pain, stomach upset) .
  • Period of Invasion: most severe phase, marked by high fever, specific signs (e.g., cough, swelling, jaundice) of infection; pathogen multiplies extensively.
  • Convalescence period: the body recovers to its pre-diseased state, where immune response gradually returns normal performance.

Objectives (Spread of Infection)

  • The objectives define reservoirs, transmission patterns, and transmission of diseases. (how pathogens spread).

Terms (Transmission of Infectious Agents)

  • A communicable disease refers to transmission of the infectious agent from one host to another.
  • Highly communicable diseases are considered contagious.
  • Non-communicable diseases do not spread from one host to another.

Sources and Transmission of Microbes

  • Reservoir refers to an organism's primary natural habitat.
  • Reservoirs include humans, animals, soil, water, and plants.

Human Reservoirs

  • A carrier is an individual harbouring a pathogen without developing symptoms yet able to transmit it to others.
  • Asymptomatic carriers show no symptoms resulting in pathogen transmission.
  • Passive carriers are contaminated healthcare providers spreading pathogens from one patient to another.

Animal Reservoirs

  • Zoonosis refers to an infection originating from animals that can be transmitted to humans.
  • 70% of emerging diseases stem from animals.
  • Diseases such as rabies, leptospirosis are zoonotic in nature.

Nipah Virus

  • The Nipah virus is transmitted through fruit contaminated by fruit bats.
  • The virus can spread from one person to another.
  • Pigs act as intermediate hosts.

Super-Spreading Events in Hospitals

  • Super-speading events involve infectious diseases spreading rapidly in hospitals. (examples: SARS)

Patterns of Transmission (Contact transmission)

  • Direct contact involves physical contact between people, without an intermediate host; e.g., sexually transmitted diseases (STDs)
  • Respiratory droplet transmission involves close contact (droplets spread less than 1 metre), like in the case of chickenpox or ebola.
  • Indirect contact/Fomites relies on non-living objects or materials (e.g. handkerchiefs or door handles) to carry infective agents from one host to another.

Patterns of Transmission (Vehicle transmission)

  • Waterborne transmission occurs when pathogens are spread through contaminated water or sewage (e.g. Cholera).
  • Foodborne transmission occurs when pathogens are transmitted through incompletely cooked or contaminated food/water.
  • Airborne transmission involves pathogen transmission via droplet nuclei or aerosols in the air, which can travel more than one meter (e.g. TB and measles).

How Communicable Infectious Diseases are Acquired

  • Respiratory droplets can cause infections.
  • Contact with contaminated objects or fomites can transmit infections.
  • Contaminated food or water can cause infections.
  • Vertical transmission involves transmission from a mother to her child (e.g., HIV and syphilis)
  • Biological vectors transmit diseases (e.g, malaria and West Nile virus).

Common Zoonotic Infections

  • Zoonotic diseases are infectious diseases naturally occurring among animals that can be transmitted to humans (examples: Rabies, West Nile Virus, Rocky Mountain Spotted Fever, Psittacosis, Leptospirosis, Anthrax, Brucellosis, Plague, Salmonellosis, and Tularemia)

Hospital Acquired Infections (nosocomial infections)

  • Nosocomial Infections originate during hospital stays.
  • Microorganisms in the hospital environment act as sources for infections.
  • Drug-resistant microorganisms in hospital environments are capable of transmission through surgical procedures, equipment, and personnel.

Recap: Objectives 2 and 3

  • The recap explains the classification of diseases (sporadic, endemic, epidemic, and pandemic).
  • The description of reservoirs (human, animals), patterns of transmission (direct, indirect, droplet, waterborne, airborne, and foodborne transmission).
  • Specific examples of infectious diseases and their vectors are covered.

Objectives (Microbiological Mechanisms of Pathogenicity)

  • The study notes explain the factors determining infectious development, the mechanisms of portal entry, bacterial pathogen penetration of host defences, and the mechanisms of endotoxins and exotoxins.

Major factors in the Development of an Infection

  • Infection development depends on the pathogen's ability to establish a portal of entry, evade host defenses, produce harms (in terms of toxins and enzymes), and exit the host.

Portals of Entry (Phase 1)

  • Pathogens enter via mucous membranes (respiratory, gastrointestinal, and conjunctiva).
  • The skin, GI tract, respiratory tract, urogenital tract, and endogenous biota are entry points.

Requirement for an Infectious Dose (ID)

  • The minimum number of pathogens needed for an infection to occur is known as the infectious dose.
  • Microbes with smaller infectious doses have higher virulence.
  • A lack of an infectious dose will not result in an infection.

Portals of Entry (Phase 2): Adherence

  • Adhesion is crucial for pathogens to establish infection.
  • Adhesion involves binding of bacterial molecules to host cell receptors.
  • Mechanisms such as fimbriae, glycocalyx, cilia, suckers, and hooks are involved in adherence.

Adhesion Properties of Microbes

  • This table lists various microbes and the mechanisms through which they adhere to the host.

Portals of Entry (Phase 3): Surviving Host Defenses

  • Virulence factors are features that facilitate invasion and establishment of pathogens.
  • Anti-phagocytic factors (like capsules or slime layers) evade host defenses.
  • Enzymes and toxins aid pathogen survival and proliferation within the host.

Enzymes and Toxins

  • Enzymes like hyaluronidase and keratinase aid in bacterial spread. (these substances dissolve the fibers in the connective tissue)
  • Toxins produced at the site of multiplication contribute to disease.

Portals of Entry (Phase 3): Bacterial Toxins

  • Exotoxins are toxins secreted by living bacteria and act on specific target cells.
  • Endotoxins are released components of damaged Gram-negative bacterial cell walls and can cause systemic effects.

A-B Exotoxins

  • A-B toxins are exotoxins with A (active) and B (binding) subunits.
  • The B subunit binds to the host cell, enabling the A subunit's entry to the cell.
  • The A subunit then disrupts normal functions within the host cell.

Endotoxins

  • Fever: endotoxins cause a pyrogenic response by stimulating immune cells to release cytokines, increasing body temperature
  • Pyrogenic response: caused by endotoxins, triggering a cascade of events resulting in fever.

Major Factors in the Development of Infection

  • Critical factors in development of infection are categorized according to phases: finding a portal of entry, attaching firmly, surviving host defenses, causing damage, and exiting the host.

Recap: Objective 4

  • Review the portal of entry, phase 2 adhesion, phase 3 virulence factors (anti-phagocytosis and capsule-slime layers).
  • The recap explains the crucial role of enzymes and toxins in the development of the infection process (especially in relation to exotoxins and endotoxins).

Faecal Contamination and Typhoid Fever

  • The study notes discuss typhoid fever, caused by Salmonella typhi which enters the body through contaminated foods and water, leading to severe intestinal infections that can lead to septicemia. (blood infection)

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Description

This quiz focuses on various microbial pathogens, including viruses and bacteria, and their transmission mechanisms. It covers diseases like dengue, chikungunya, malaria, and tuberculosis, as well as the role of exotoxins and normal flora in human health. Test your knowledge on how these pathogens affect the human body and their means of transmission.

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