Bacterial Intro

Question 2

Classify bacteria on the basis of O₂ requirement and temp. requirement & examples.

Answer 2

On the basis of O₂ requirement:

① Obligate aerobes: They require O₂ & cannot survive without it.
eg: Pseudomonas, M. Tuberculosis.

② Facultative anaerobe: Grows with or without O₂.
eg: Staphylococci, E. coli.

③ Obligate anaerobes: Grows only in the absence of O₂.
eg: Clostridium species.

④ Aerotolerant anaerobes: Grows in the presence of O₂ but does not use it.

⑤ Micro-aerophilic: Grows in low O₂ concentration.
eg: Campylobacter jejuni, H. pylori.

On the basis of temperature:
Psychrophilic: Grows best at low temp (15°-20°C) Moraxella, Vibrio
Mesophilic: Grows best at body temp (30-37°C) Staph aureus, E.coli
Thermophilic: Grows best at high temp: (50-60°C) Bacillus stearothermophilus.

Question 3

Q3. Enlist the essential & non-essential structures of bacteria

Answer 3

Essential:
1. CELL WALL
2. CYTOPLASMIC MEMBRANE
3. RIBOSOME
4. NUCLEOID
5. PERIPLASM
6. MESOSOME

Non-essential:
1. Capsule
2. Pili
3. Flagella
4. Spore
5. Plasmid
6. Glycocalyx
7. Granule

Question 4

Q4. Mention the function of bacterial capsule

Answer 4

1. Protection against attack by antibacterial agent
2. Protection against ingestion by phagocytes
   Because capsular polysaccharide has -ve charges that repels (-vely) charged cell membrane of neutrophil
3. Role in adherence of bacteria
4. Specific identification of organism by using antiserum against capsular polysaccharide.
   In presence of antibody, capsule will swell
   It is known as Quellung rxn. eg. S. pneumoniae, N. meningitidis, H. inf

Question 5

Mention the composition of bacterial capsule

Answer 5

It is a condensed, well-defined layer closely surrounding the cell that includes particles such as India ink.
It is composed of:
Water: 97%
Sucrose: 2%
Polysaccharide
Polypeptide
Hyaluronic acid

Question 6

Q. Write down functions of bacterial cell wall:

Answer 6

Peptidoglycan: Gives rigid support.
1. Supports the weak cytoplasmic membrane.
2. Maintains characteristic shape of bacteria.
3. Serves as a primer for its own biosynthesis.
4. Plays a role in all division.
5. LPS of gram-ve cell wall is responsible for its endotoxic activity.

Question 7

Q. Ennumerate the structural components of gram +ve bacterial cell wall.

Answer 7

Gram +ve:

Peptidoglycan layer (Murein)
Teichoic acid.
Teichuronic acid.

Gram -ve:

Peptidogycan (Murein)
Lipoprotein
Phospholipid bilayer with proteins of different functions.
Periplasmic space.
Lipopolysaccharide of outer membrane.
Lipid A.
Polysaccharide (Antigen O)

Question 8

Q: Differentiate cell wall of gram +ve and gram -ve bacteria with diagram.

Answer 8

Gram +ve

Thicker peptidoglycan (30-40 Layer)
Teichoic acid is present
Outer memb. (lipopolysaccharid) is absent
Periplasmic space Absent
More sensitive to cell wall inhibiting antis.
On grem staining: Stains vilet due to crystal violet

Gram -ve

Thinner peptidoglycan (single layer)
Absent technical acid
Present outer memb
Present periplasmic space
Less sensitive to cell wall inh antibiotics
Red due to carbol fuschin

Question 9

Q: Functions of cell membrane

Answer 9

1.Selective toxicity and transport of solutes
2.Electron transport and oxidative phosphorylation.
3. Excretion of hydrolytic enzyme.
4.Bearing enzyme and carries molecule.
5.Bearing receptors, and other protein for chemo tactic or other sensory transduction system.

Question 10

Q: What is plasmid. Medical imp. of plasmid…

Answer 10

Ans. Plasmids are double stranded circular DNA molecules that are capable of replicating independently of the bacterial chromosome.

CLINICAL IMPORTANCE:
They carry genes for:

1.Antibiotic resistance. - enzymes.
2.Exotoxins- Enterotoxin.
3.Pili.- Adherence to bacterial cell.
4.Resistance to heavy metals eg Hg:. Reductase enzyme
5.Resistance to ultraviolet rays:
DNA repair enzyme

FUNCTIONS:

Plasmids encode genes for some enzymes that can destroy a particular drug, e.g. β-lactamase enzyme destroys β-lactam drugs.
Plasmid encodes gene called (R-factor) resistance factor, which controls formation of enzymes capable of altering function of a drug.
Plasmid encodes gene for sex pili.
Plasmid encodes genes for some transport proteins which mediate drug resistance.

Question 11

Give functions of pili / fimbriae:

Answer 11

They mediate attachment of bacteria to specific receptors on human cell surface.

Sex pili help in transfer of genetic material from donor to recipient bacteria after conjugation.

Transfer of genes of drug resistance from one bacteria to another.

Antigenicity of the pili.

Question 12

Define flagella

Answer 12

Flagella are long thin filamentous thread-like structures originating from cytoplasmic membrane of bacterial cell…
It is composed of protein flagellin.

Types:

Peritrichous: eg. E. coli, Salmonella
Amphitrichous: Pseudomonas
Lophotrichous: Spirillum
Monotrichous: Vibrio cholera

Question 13

Func of flagella

Answer 13

FUNCTIONS:

① Motility: Organ of locomotion.

② Chemotaxis: Flagella moves bacteria towards nutrients & other attractants.

③ Antigenic: Antigenic structure of flagella is used for identification & classification of salmonella.

④ Pathogenic: It propels the bacteria upto the urethra into the bladder. eg. In UTI by Ecoli & proteus.

Question 14

Spore

Answer 14

Spore: A dormant structure capable of surviving for prolonged periods, endowed with the capacity to re-establish the vegetative stage of growth under appropriate environmental conditions.

Composition:

① Bacterial DNA

② Small amt of cytoplasm

③ Peptidoglycan

④ Very little water & thick keratin like membrane

Question 15

Parts of a spore

Answer 15

Parts of a spore:

Core: It is the spore protoplast containing a complete nucleus, protein synthesis and energy generating systems, homologous to protoplast of veg. cell.
Spore wall: It is the inner most layer, surrounding the core containing normal peptidoglycan homologous to cell wall of veg. cell.
Cortex: It is the thickest layer of cell envelope. It contains an unusual type of peptidoglycan. Extremely sensitive to lysozyme and its autolysis. It plays a role in cell germination.
Coat: It is composed of keratin like protein. Protects against antibacterial agents.
Exosporium: It is a lipoprotein membrane, stabilizes the outer membrane.

Question 16

Classify spores

Answer 16

Classify spores:

(A) Exospore: The spore that is formed outside the parent vegetative cell. eg. Fungal spores.

(B) Endospore: The spore that is formed inside the parent vegetative cell. eg. Bacterial spores.

→ Acc. to shape: - Oval. Spherical.

→ Acc. to position:
. Terminal
. Sub-terminal
. Central

→ Acc. to size:
. Bulging
. Non - bulging.

Question 17

classify spore bearing bacteria!

Answer 17

→ (Gram positive bacilli

Clostridium tetany
Clostridium botulism
Clostridium perfringens
Bacillus anthracis
Bacillus subtilis

→ Gram +ve cocci: sporosarcina

Gram negative cocco bacilli: Coxiella burnetti

Draw & label

Exosporium
spore coat
Inner membrane
spore cortex
Spore core

Question 18

Process of sporulation

Answer 18

Process of sporulation:

The process of formation of spore from vegetative form of bacteria from adverse environmental conditions is called sporulation.

Formation of axial filament.
Forespore septum formation.
Engulfment of forespore.
Cortex synthesis.
Coat deposition.
Maturation.
Lysis of mother cell.
Newly formed spore.

Medical imp.:

① Highly resistant to antibiotics, chemicals or heat.
② Spores are infective form of many bacteria eg. Clostridium tetany.
③ Spores are used as indicator of sterilization.
④ Spores can be destroyed by autoclaving

Question 19

Draw the label bacterial growth curve with clinical imp of each phase.

Answer 19

If a small number of bacteria is inoculated into a liquid nutrient medium, and bacterial is counted at frequent intervals and a graphical demonstration is produced by putting log no. of cells along the Y-axis and time along X-axis, then it shows bacterial growth curve.

Phases:

Lag phase / preparatory phase.
Log phase / exponential phase.
Stationary phase.
Decline phase (death phase).

In chemostat log phase persists.

Question 20

Clinical imp of each phase of bacterial growth curve

Answer 20

Importances

[Lag phase]:
Membrane acting antibiotic such as polymyxins, amphotericin -B can be used in this phase.
Detergents, soaps and other surface acting agents act better in lag phase.

Log phase:

Antibiotic act better in this phase as cell wall gronte is very active during this phase.
At this phase, disease producing capability of bacteria is highest.

[Stationary phase]:
Release of exotoxin starts
Spore forming bacteria starts spore formation.
Cell wall acting antibiotic may be used.
Gram +ve bacteria may be transformed into gram -ve by erosion of peptidoglycan layer.

Decline

Exotoxin of C. diphtheriae is produced.
Bacteria may form L- forms resistant to antibiotics.
Sporulation starts in some bacteria.

Question 21

Q Why anaerobic bacteria can’t grow in presence of O2?

Answer 21

In certain bacteria,

Oxygen acts as the hydrogen acceptor in the final step of energy production catalysed by flavoprotein and cytochromes.

During metabolism, O2 generates 2 toxic molecules.

O2⁻ (superoxide) - free radical.
H202
Bacteria requires 2 enzymes to neutralize them.

Superoxide dismutase
2O2- +2H+____sod____ H2O2 +O2

Catalase
2H2O2 _____catalase____ 2H2O + O2

Certain bacteria eg. Clostridium tetani lack one or both of these enzymes and so it cannot neutralize the toxic metabolites of O2 & therefore cannot live in presence of O2.

Question 22

Q. What do you mean by growth & death of the bacteria?

Answer 22

→ Bacterial growth means development of a bacterium into its mature pathogenic form.

Bacterial death: They are considered to be dead when they are incapable of growing in a suitable media. Under influence of antibacterial agents bacteria die in installments i.e. at each time interval a definite percentage of organisms undergo death - %age law.

Question 23

Q. Discuss briefly about endotoxic shock:

Answer 23

It results from severe, generalized inflammatory response induced by endotoxin released in blood from gram -ve bacteria.
Mech: Fever: By IL-1 & 6.
Hypotension: TNF, NO, Bradykinin.
Inflammation: C5a produced by alternate pathway of complement activation.
DIC: Activation of tissue factor.

Question 24

Growth and death of bacteria

Answer 24

Bacterial growth means development of a bacterium into its mature pathogenic form.

Bacterial death: They are considered to be dead when they are incapable of growing in a suitable media. Under influence of antibacterial agents bacteria die in installments i.e. at each time interval a definite percentage of organisms undergo death - %age law.

Question 25

Why anaerobic bacteria can't grow in presence of 02

Answer 25

Q Why anaerobic bacteria can't grow in presence of O2? → In certain bacteria, Oxygen acts as the hydrogen acceptor in the final step of energy production catalysed by flavoprotein and cytochromes. During metabolism, O2 generates 2 toxic molecules. O2⁻ (superoxide) - free radical. Bacteria requires 2 enzymes to neutralize them. Superoxide dismutase 2O2+ 2H+____sod____ H2O2+ O2 Catalase 2H2O2___catalase___ 2H20 +02 Certain bacteria eg. Clostridium tetani lack one or both of these enzymes and so it cannot neutralize the toxic metabolites of O2 & therefore cannot live in presence of O2.

Question 26

Q. Discuss briefly about endotoxic shock:

Answer 26

It results from severe, generalized inflammatory response induced by endotoxin released in blood from gram -ve bacteria. Mech: Fever: By IL-1 & 6. Hypotension: TNF, NO, Bradykinin. Inflammation: C5a produced by alternate pathway of complement activation. DIC: Activation of tissue factor.Clinical features Clinical features Patients typically present with fever and hypotension. Increased heart rate and respiratory rate. Organ dysfunction secondary to perfusion abnormalities. Patients may present to oliguria, lactic acidosis, and DIC.

Question 27

Enumerate the virulence factors of gram +ve bacteria:

Answer 27

1.Adherence factors: Pili Capsule Glycocalyx 2.Invasiveness Enzymes: Collagenase, Hyaluronidase of Strep. pyogens, coagulase in Staph. aureus 3.Antiphagocytic factors: Capsule Pili Protein Aj coagulase enzyme ④ Enzymes: IgA protease - S. pneumoniae. Tissue degrading enzyme: Hyaluronidase, lecithinase. ⑤ Toxins: Endotoxin: Enterotoxin, tetamospasmin, botulinum toxin

Question 28

Q Pathophysiology of endotoxic shock

Answer 28

Endotoxin (lipid A) ① Activates macrophages. a) IL-1 → fever. 5) TNF → Fever & hypotension. c) NO → Hypotension. ② Activates complements: ① C3a → Hypotension & edema. ② C5a → Neutrophil chemotaxis. ③ Activates tissue factor: → Coagulation cascade → DIC cell injury

Question 29

Functions of each component of gram -ve cell wall

Answer 29

.Phospholipid bilayer ☆☆☆. It consists of 3 parts: 1.Peptidoglycan layer: gives rigid support and protects against osmotic pressure 2.Outer membrane - Phospholipid bilayer lipid A: it acts as endotoxin Polysaccharide : antigen O lipoprotein 3.Periplasmic space: Binding protein Hydrolytic enzyma β lactamase

Question 30

Capsulated bact

Answer 30

Capsulated bacteria Neisseria meningitidis Bordatella pertussis Strep. Pneumoniae * Klebsiella Pneumoniae * Haemophilus influenzae *

Question 31

Q. What are the methods of transfer of genetic information from one bacteria to another.

Answer 31

1.Conjugation: Transfer of DNA from donor to recipient cell mediated by plasmids, transmitted through sex pili. 2.Transduction: Process of DNA transfer by means of a bacteriophage. 3.Transformation: It is an active uptake of DNA from one bacteria by another. 4.Transposition: Some genes (transposons) jump from chromosome to plasmid or to a β bacteriophage through which to another bacterial cell. 5.Through plasmid.

Question 32

Name some gram positive rods.

Answer 32

Spore forming - aerobic: Bacillus - anaerobic: clostridium Non spore forming - filamentous : actinomyces, noxardia - Non filamentous: cornyebacterium Listeria

Question 33

Gram positive cocci

Answer 33

Streptococcus Staphylococcus

Question 34

Gram neg cocci

Answer 34

Neiserria

Question 35

Gram neg bacilli

Answer 35

1.Aerobic: pseudomonas 2.Anaerobic; bacteroides 3.Facultative: -curved- helicobacter Campylobacter Vibrio -Straight; hemophilus bordatella Brucella pasteurella escherichia Klebseilla

Question 36

Define prokaryotes and eukaryotes.

Answer 36

Prokaryotes Prokaryotes are unicellular organisms without a true nucleus or membrane-bound organelles. Their genetic material (DNA) is located in a region called the nucleoid, not enclosed by a membrane. Examples: Bacteria and Archaea Key Features: Genetic element is nucleoid No membrane-bound organelles Smaller in size (1–10 µm) Cell wall usually present (e.g., peptidoglycan in bacteria) Plasmid may or may not be present 70 s ribosomes Cell wall contains peptidoglycan Eukaryotes are organisms whose cells contain a true nucleus and membrane-bound organelles. Key Features: True nucleus (DNA enclosed within nuclear membrane) Linear DNA organized into chromosomes Membrane-bound organelles (e.g., mitochondria, ER, Golgi) Larger in size (10–100 µm) May be unicellular or multicellular Human cell Plasmid is always absent 80s ribosomes Cell wall does not contain peptidoglycan Sterol in Cell membrane

Question 37

Koch postulates

Answer 37

Robert koch (1843-1910), German Bacteriologist published "Koch's Postulates" (1884), the critical test fore the involvement of microorganism in a disease The postulates are: 1.The micro-organism must be found in abundance in all' organisms suffering from the disease, but not in healthy organisms. 2.The agent must be isolated and cultured in vitro 3.The disease must be reproduced when a pure culture of the agent is inoculated into a susceptible host. 4.The agent must be recoverable from the experimentally infected host.

Question 38

Organisms that violate Koch postulates

Answer 38

1.koch abandoned the second part of the firest postulate due to asymptomatic carriers of: - Cholera - Typhoid fever - Polio - Herpes simplex - HIV - Hepatitis-C 2. Violation of 2nd postulates • The particulare bacteria (Mycobacterium leprae cause leprosy) can't be grown in pure culture in the laboratory. • There is no animal model of infection with that particular bacteria. 3.The 3nd postulete specifies "Should", not "must", because as koch himself proved in regard to both tuberculosis and cholera. • Not all organisms exposed to an infectious agent will acquire the infection because of: host immune system Acquired Immunity. Genetic Immunity. • A harmless bacteria may cause disease because of: -Acquired extra virulence Factori, - Gain access to deep tissue - Immunocrompomised host.

Question 39

Define nucleioid

Answer 39

region within a prokaryotic cell where the genetic material (DNA) is located containing a single chromosome. It is not surrounded by a nuclear membrane, unlike the nucleus in eukaryotic cells.

Question 40

Differences btw nucleus and nucleoid

Answer 40

1. Presence of Membrane The nucleus is enclosed by a double-layered nuclear membrane, which separates the genetic material from the rest of the cell. In contrast, the nucleoid has no surrounding membrane; it is an open region within the cytoplasm. --- 2. Type of Cell A nucleus is found only in eukaryotic cells (like those of plants, animals, and fungi). On the other hand, a nucleoid is present only in prokaryotic cells (like bacteria and archaea). --- 3. DNA Structure Inside the nucleus, the DNA is linear and arranged into chromosomes. In the nucleoid, the DNA is usually circular and not organized into true chromosomes. --- 4. Internal Structures The nucleus contains additional components like the nucleolus and nuclear pores, which help in producing ribosomes and exchanging materials. The nucleoid has no such internal structures; it is just a dense region with DNA. --- 6. Function the nucleus also regulates gene expression, cell division, and metabolism. The nucleoid mainly serves as the site where the DNA is stored and transcribed, with less regulation compared to the nucleus.

Question 41

Name some capsular vaccines

Answer 41

Capsular vaccines are made using the polysaccharide capsule of certain bacteria. 🛡️ 1. Pneumococcal Vaccine Organism: Streptococcus pneumoniae 🛡️ 2. Meningococcal Vaccine Organism: Neisseria meningitidis 🛡️ 3. Haemophilus influenzae type b (Hib) Vaccine Organism: Haemophilus influenzae type b

Question 42

What is spheroplast and protoplast

Answer 42

A protoplast is a bacterial or fungal cell that has had its entire cell wall completely removed, leaving only the plasma membrane and the inner contents (cytoplasm, nucleus/genetic material). Formed mainly from Gram-positive bacteria. Created using enzymes like lysozyme, which digest the thick peptidoglycan wall. More fragile because it lacks the protective cell wall. Osmotically sensitive and must be kept in an isotonic environment. 🧪 Example: A Streptococcus cell treated with lysozyme becomes a protoplast. 🧫 Spheroplast: A spheroplast is a cell that has had its cell wall only partially removed, meaning some of the wall material still remains. Usually formed from Gram-negative bacteria, which have a thin peptidoglycan layer and an outer membrane. Treated with lysozyme to weaken the wall. Also osmotic-sensitive, but not as fragile as protoplasts due to residual wall structure. 🧪 Example: A E. coli cell treated with lysozyme becomes a spheroplast.

Question 43

L forms

Answer 43

If cells like protoplast or spheroplasts are able to grow or divide they are called l forms L forms are difficult to cultivate Some l forms can revert to normal bacillary form upon the removal of inducing stimulus. L forms are relatively resistant to antibiotic treatment L forms in host may produce chronic infection Reversion of l form to normal form can result in relapse of infection.

Question 44

Factors for spore survival

Answer 44

1. Presence of impermeable spore coat or cortex 2. Low metabolic or enzymatic activity 3. Low water content in cytoplasm 4. High level of Calcium dipicolinate

Question 45

Pyogenic bacteria

Answer 45

Staphylococcus aureus Streptococcus pyogens Neiseria gonorrhea Pseudomonas aeroginosa

Question 46

Exotoxin producing bacteria

Answer 46

1.Ecoli Enterotoxin Shiga like toxin 2. Cornyebacterium diptheriae Diptheria toxin 3. Clostridium tetany Tetanospasmin Tetanolysin 4. Clostridium botulinum Botulinum toxin 5. Vibrio cholera Cholera toxin 6. Staphylococcus aureus Enterotoxin Toxic shock syndrome toxin Exfoliatin

Question 47

Toxin mediated diseases

Answer 47

Corynebacterium diphtheriae → Diphtheria.. dip toxin • Clostridium tetani → Tetanus Tetanospasmin • Clostridium botulinum → Botulism.. botulinum toxin • Clostridium difficile → Pseudomembranous colitis • Clostridium perfringens → Gas gangrene • Bacillus anthracis → Anthrax • Staphylococcus aureus.. → Toxic shock syndrome( tsst) food poisoning(enterotoxin), scalded skin syndrome( exfoliatin) • Streptococcus pyogenes → Scarlet fever • Escherichia coli → Watery diarrhoea, bloody diarrhoea

Question 48

Steps of pathogenesis of bacteria

Answer 48

1. Transmission from an external source into the portal of entry. 2. Evasion of primary host defenses such as skin or stomach acid. 3. Adherence to mucous membranes, usually by bacterial pili. 4. Colonization by growth of the bacteria at the site of adherence. 5. Disease symptoms caused by toxin production or invasion accompanied by inflammation. 6. Host responses, both nonspecific and specific (immunity), during step 3, 4 & 5. 7. Progression or resolution of the disease.

Question 49

Diff btw exotoxin and endotoxin

Answer 49

Traits 1. Source Exotoxin : Certain species of some Gram positive & Gram negative bacteria. Endotoxin: Cell wall of most Gram negative bacteria. 2. Secreted from cell Exotoxin : Yes Endotoxin : no 3. Chemistry Exotoxin : Protein or polypeptide Endotoxin : lipopolysaccharide 4. Solubility Exotoxin : Soluble substance. Endotoxin : indoluble 5. Location of gene Exotoxin : Plasmid or bacteriophage Endotoxin :Bacterial chromosome. 6. Toxicity Exotoxin : high Endotoxin : low 7. Clinical effects Exotoxin : Various effects. Endotoxin : Fever and shock 8. Mode of action Exotoxin : various modes Endotoxin : Includes TNF (tumour necrosis factor) & IL-1.

Question 50

Mechanism of exotoxin

Answer 50

ADP-ribosylation: Stimulates adenylate cyclase by ADP-ribosylation. • Super-antigen: Binds to class II MHC protein and T-cell receptor; induces IL-1 and IL-2. • Protease: Cleaves desmoglein in desmosomes. • Lecithinase: Lecithinase hydrolyzes lecithin in the cell membrane, resulting in destruction membrane and widespread cell death.

Question 52

On the basis of ph classify bacteria

Answer 52

Best ph: 7.2- 7.4 Acidophils: grows high acid media ie. 4-4.5 eg lactobacilli Alkalophils: 8-9 v. cholera

Question 53

Halophilic bact

Answer 53

Halophilic bacteria are microorganisms that thrive in high-salt (NaCl) environments. The word "halophilic" comes from Greek: "halos" = salt and "philos" = loving — so they are literally "salt-loving" bacteria. Eg.vibrio spp 2-5% NaCl Salt lakes Salty foods

Question 54

Why death rate and growth rate is same in stationary phase

Answer 54

1. Depletion of nutrients 2. Accumulation of toxic products And cells are still dividing

Question 55

Log phase imp

Answer 55

Antibiotic act better at this phase as cell wall growth is very active during this phase. At this phase disease-producing capability of bacteria is highest, and if not treated the disease properly at this stage, dreadful condition like septicaemia can result.

Question 56

Imp of decline phase.

Answer 56

The death rate is greater than the multiplication rate. Accumulation of toxic product occurs. Time requires few hours to days. Importance: Exotoxin of C. diphtheria is produced in this phase. Bacteria may develop L-forms, which are resistant to antibiotics. Sporulation starts in some bacteria. Spores are meant to survive the decline phase. It’s the vegetative cells that die. Spores only die if extreme or artificial conditions are used.

Question 57

What are persisters. When do they grow

Answer 57

Bacteria may develop l forms Which are resistant to antibiotics These are the persisters Are found in decline phase of the growth cycle.

Question 58

What is normal flora

Answer 58

The human microbiome (Normal flora) is the term used to describe the distinct microbial communities that inhabit different host environments on the body's skin and mucosal surfaces. 2 types 1. Resident flora: These are micro-organisms regularly present in the region, e.g. Viridans streptococci in mouth and throat, E. coli in intestine. 2. Transient flora: The micro-organisms are present only of hours to weeks, e.g. Streptococcus pyogenes in throat.

Question 59

Benefits of normal flora

Answer 59

1. Prevention of colonization of pathogenic organism : in mouth and lower bowel an invading pathogen may fail to compete for the nutrients with normal flora. Thus normal flora prevents infection, 2. Production of antimicrobial substances: Some bacteria produce bacteribeins or antibiotics, which also prevent infection by pathogenic bacteri 3. Antigenic stimulation by normal flora; in new born, IgA that is secreted through mucus Membranes and gives protection. 4.Nutritional function; Bacteria of the gut provide important nutrients, such as vitamin k

Question 60

Hoe normal flora causes disease

Answer 60

1) When the organisms are displaced from their normal site in the body to an abnormal site. example is the introduction of the normal skin flora S. epidermidis into the bloodstream where it can colonize catheters and neart valves, resulting in bacterial endocarditis. 2) When potential pathogens gain a competitive advantage due to diminished populations of harmless competitors. For example, when normal bowel flora is depleted by antibiotic therapy leading to overgrowth by the resistant Ct. difficile, which can cause severe colitis 3) When harmless commonly ingested food substances are converted into carcinogenic derivatives by bacteria in the colon. 4) When individuals are immunocompromised, normal lora can overgrow and become pathogenic.

Question 61

Benefits of normal flora

Answer 61

1. Prevention of colonization of pathogenic organism. In mouth and lower bowel an invader or pathogen may fail to compete with normal flora for nutrition and receptor sites. Thus normal flora prevents infection, 2. Production of antimicrobial substances: Some bacteria produce bacteribeins or antibiotics, which also prevent infection by pathogenic bacteria. 3. Antigenic stimulation by normal flora. In new borns, bacteria act as powerful stimulus for development of immune response. leads to production of IgA that is secreted through mucus membranes & give protection. Nutritional function; Bacteria of the gut provide important nutrients, such as vitamin K,

Question 62

Where normal flora are present

Answer 62

Skin mouth throat colon vagina

Question 63

Throat normal flora

Answer 63

1.Viridans Streptococci Extra Strep pyogens Strep pneumonia

Question 64

Colon normal flora

Answer 64

Bacteroides fragilis E coli

Question 65

How normal flora is maintained in healthy indivisual

Question 66

How normal flora is maintained in healthy indivisual

Answer 66

2. Local Environmental Conditions Factors such as pH, temperature, oxygen levels, moisture, and nutrient availability in each niche determine which microbes thrive. For example, acidic vaginal pH supports Lactobacillus, while the gut environment (reduced oxygen, high nutrients) favors dense anaerobic populations . Microbial Interactions and Competition Flora microorganisms compete with pathogens for space and resources, produce inhibitory substances (like lactic acid or bacteriocins), and create colonization resistance, greatly lowering the risk of infection .