extra cellular microbes

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EXTRA CELLULAR MICROBES DR.AMITHBABU.C.B MScD-ENDO

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Page 1: Extra Cellular Microbes

EXTRA CELLULAR MICROBES

DR.AMITHBABU.C.B

MScD-ENDO

Page 2: Extra Cellular Microbes

General features of immune responses to microbes

Defense against microbes is mediated by the effector mechanisms of innate and adaptive immunity.

The immune system responds in distinct and specialized ways to different types of microbes to most effectively combat these infectious agents.

Page 3: Extra Cellular Microbes

The survival and pathogenicity of microbes in a host are critically influenced by the ability of the microbes to evade or resist the effector mechanisms of immunity.

In many infections, tissue injury and disease may be caused by the host response to the microbe and its products rather than by the microbe itself

Page 4: Extra Cellular Microbes

WHAT ARE MICROBES LIKE?Our bodies are made up of cells and extra-cellular tissue and matrix. Some microbes invade our bodies and live in between the cells in the extra-cellular tissues and matrix. Those are extracellular microbes.

Other microbes, once they invade our bodies, target certain cells, gain access to their interior live and multiply inside them. Those are intracellular microbes

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DIVISION

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Small extracellular microbes are microbes that can be phagocytosed by a phagocytic cell and include bacteria

Large extracellular microbes are microbes that are too large that they cannot be phagocytosed by a phagocytic cell and include helminth parasites.

intracellular microbes cancer cells as cancer cells operate at an intracellular level, specifically at the level of the nucleus, which is the same level at which typical intracellular microbes, viruses,

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Immune evasion by extracellular bacteria

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Adaptive Immunity to Extracellular Bacteria

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STAPHYLOCOCCUSStaphylococcus is a genus of Gram-positive bacteria. Under the microscope they appear round (cocci), and form in grape-like clusters.

The Staphylococcus genus includes at least forty species. Of these, nine have two subspecies and one has three subspecies

.Most are harmless and reside normally on the skin and mucous membranes of humans and other organisms.

they are a small component of soil microbial flora.

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STAPHYLOCOCCI

Gram-positive

cluster-forming coccus

nonmotile, nonsporeforming facultative anaerobe

fermentation of glucose produces mainly lactic acid

catalase positive

coagulase positive

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golden yellow colony on agar

normal flora of humans found on nasal passages, skin and mucous membranes

pathogen of humans, causes a wide range of suppurative infections, as well as food poisoning and toxic shock syndrome

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Gram stain of Staphylococcus

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Species of Staphylococci

Three species of staphyloccoci have medical importance:

S. aureus: Pathogenic & commensal found in nose (nares)

S. epidermidis: non pathogenic & common commensal in nares & skin

S. saprophyticus: Cause UTI in female & occasionally commensally found skin

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S. aureus expresses many potential virulence factors

surface proteins that promote colonization of host tissues

invasins that promote bacterial spread in tissues (leukocidin, kinases, hylauronidase)

surface factors that inhibit phagocytic engulfment (capsule, Protein A)

biochemical properties that enhance their survival in phagocytes (carotenoids, catalase production)

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(5) immunological disguises (Protein A, coagulase, clotting factor);

(6) membrane-damaging toxins that lyse eukaryotic cell membranes (hemolysins, leukotoxin, leukocidin;

(7) exotoxins that damage host tissues or otherwise provoke symptoms of disease

(8) inherent and acquired resistance to antimicrobial agents.

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STAPHYLOCOCCAL INFECTIONS

usually remain localized at the portal of entry by the normal host defenses

The portal may be a hair follicle.

Another portal of entry is the respiratory tract

Serious consequences of staphylococcal infections occur when the bacteria invade the blood stream

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STREPTOCOCCI

Streptococcus is a genus of spherical Gram-positive bacteria belonging to the phylum Firmicutes and the lactic acid bacteria group. Cellular division occurs along a single axis in these bacteria, and thus they grow in chains or pairs

Contrast this with staphylococci, which divide along multiple axes and generate grape-like clusters of cells. Streptococci are oxidase- and catalase-negative, and many are facultative anaerobes

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Streptococci are facultatively anaerobic.

Gram-positive organisms that often occur as chains or pairs and are catalase-negative (in contrast, staphylococci are catalase positive)

Streptococci are subdivided into groups by antibodies that recognize surface antigens ..

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Streptococci classification

These groups may include one or more species. The most important groupable streptococci are A, B and D.

Among the groupable streptococci, infectious disease (particularly pharyngitis) is caused by group A which is thus emphasized here

Streptococcus pneumoniae (a major cause of human pneumonia) and Streptococcus mutans and other so-called viridans streptococci (among the causes of dental caries) do not possess group antigens

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Three types of hemolysis reaction (alpha, beta, gamma) are seen after growth of streptococci on sheep blood agar

alpha-partial hemolysis with a green coloration

(from production of an unidentified

product of hemoglobin).

Beta-refers to complete clearing.

gamma- there is no lysis.

Group A

group B beta hemolytic

D -alpha or gamma.

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Streptococcus in chains (Gram stain)

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Pathogenic determinants

M- protein

Precipitate fibrinogen

Clump platelets and WBC

Toxin

Hemolysin- streptolysin O

Erythrogenic toxin/pyrogenic toxin

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b-hemolytic S. pyogenes

Most serious streptococcal pathogen

Strict parasite

Inhabits throat, nasopharynx, occasionally skin

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Disease associated

pharyngitis (strep throat), scarlet fever (rash),

Impetigo,cellulitis

Invasive, toxigenic infections can result in necrotizing fasciitis, myositis and streptococcal toxic shock syndrome. Patients may also develop immune-mediated post-streptococcal sequelae

Acute rheumatic fever and acute glomerulonephritis, following acute infections caused by Streptococcus pyogenes

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Virulence Factors of b-hemolyticS. pyogenes

Extracellular toxins:

streptolysins – hemolysins; streptolysin O (SLO) and streptolysin S (SLS) – both cause cell and tissue injury

pyogenic toxin (erythrogenic) – induces fever and typical red rash

superantigens – strong monocyte and lymphocyte stimulants; cause the release of tissue necrotic factor

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Extracellular enzymes

streptokinase – digests fibrin clots

hyaluronidase – breaks down connective tissue

DNase – hydrolyzes DNA

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OTHER STREPTOCOCCI

S. sanguis

S. mutans

S. Mitis

S. milleri

S. intermedius

S. sanginosus

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Escherichia coliEscherichia coli is a Gram negative rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms (endotherms).

Most E. coli strains are harmless, but some, such as serotype O157:H7, can cause serious food poisoning in humans, and are occasionally responsible for product recalls.The harmless strains are part of the normal flora of the gut, and can benefit their hosts by producing vitamin K2, and by preventing the establishment of pathogenic bacteria within the intestin

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FEATURESE. coli is Gram-negative, facultative anaerobic and non-sporulating.

Cells are typically rod-shaped and are about 2 micrometres (μm) long and 0.5 μm in diameter, with a cell volume of 0.6 - 0.7 μm3.

Optimal growth of E. coli occurs at 37°C (98.6°F) but some laboratory strains can multiply at temperatures of up to 49°C (120.2°F)

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Role as normal microbiota

E. coli normally colonizes an infant's gastrointestinal tract within 40 hours of birth, arriving with food or water or with the individuals handling the child. In the bowel, it adheres to the mucus of the large intestine. It is the primary facultative anaerobe of the human gastrointestinal tract

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Habitat

E. coli is the most abundant facultatively anaerobic microorganism that is found in the GI tract of humans and mammals.  The average human GI tract contains E. coli in the Intestine of a Human upwards of 1 kg (~2.21 lb) of bacteria, and approximately 0.1-1%, these are E. coli.

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Role in disease

Virulent strains of E. coli can cause gastroenteritis, urinary tract infections, and neonatal meningitis. In rarer cases, virulent strains are also responsible for haemolytic-uremic syndrome, peritonitis, mastitis, septicaemia and Gram-negative pneumonia

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