Chapter 23 mini quizzes

Describe glycocalyx, slime layers, and capsules

Glycocalyx: its a kind of protective coating of bacterial cell wall. Its a macromolecular polyusaccharide layer of polymer. It makes process of infection easy. Slime layer: sometimes glycocalyx is present in the form of loose layer that keeps cells embedded inside. It also helps cell from losing its nutrients and water. Capsule: enhances pathogenicity of pathogen. Sometimes glycocalyx is present in the form of detectable solid outer layer that helps in protecting bacterial cell from host defense mechanism.

Why do gram-positive bacteria not produce endotoxins

Gram pos do not produce endotoxin as their cell wall is mostly peptidoglycan.

What is the importance of Lactobacillus found in the urogenital tract of healthy adult women.

An adult vagina is fairly acidic with pH<5 and contains significant quanity of glycogen. Lactobacillus is able to ferment the glycogen polysaccharide and synthesize lactic acid. Lactic acid results in local acidic environment. The acidic environment helps to control growth of potentially pathogenic micro-organisms.

What circumstances can contribute to attenuation of a pathogen

Attenuation is the decrease of a pathogen virulence. They can be attenuated in case of isolation of pathogen from diseased animals as lab cultures.

Why is it necessary to test for endotoxin in water used for injectable drug preparations

Because endotoxins induce fever. also to prevent gram negative bacterial contamination.

Identify host factors that limit or accelerate infection of a micro-organism at selected local sites

Optimum inoculum is necessary to initiate infection: First sign of infection is noticed only when a pathogen is well grown and start absorbing nutrients from its host. Host tissue must be invaded to initiate disease Low host immunity (susceptible) fails to prevent infection.

Compare the microbial environments in the oral cavity in newborns and adults

Oral cavity of newborns in nearly microbe free until it comes into contact with the mother. Its later colonized by facultative and aerobic organisms. They get gram positive cocci from breast milk and gran negative bacilli from bottle. In adults, oral microflora comprises both of gram pos/neg, fungi, etc... most common bacteria in adult oral cavity is Streptococcus and Staphlococcus

Identify physical and chemical barriers to pathogens. How might these barriers be compromised.

Skin is an efficient physical barrier. The acidity of skin is lowered due to fatty acid secretion. This lowered pH inhibits colonization on by by pathogens. Chemicals barriers are like conditions in the stomach where the pH is around 2.

Identify several essential compounds made by indigenous intestinal micro-organisms

Some of the products produced are essential to maintain health and to protect us from bad Micro flora. The products are: B12, vitamin K, steroids, gaseous odoriferous substances, nitrogen, hydrogen, and carbon dioxide.

How do streptokinase and coagulase promote bacterial infection and invasion.

Streptokinase is an enzyme released that has fibrinolytic properties. Its harmful for the host but helps in further invasion. Coagulase is a cell associated diffusible enzyme. It converts fibrinogen to fibrin. Fribrin causes blood clotting. They both promote bacterial infection by weaking of host blood clotting mechanism and protecting from host defenses.

Identify factors that influence susceptibility to infection and can controlled by the host.

There are many host factors that can influence disease ability of pathogens. Factors like: Stress and a off balance of hormones, poor diet. Major injuries like spinal punctures. or surgeries. Life choices like smoking, high alcohol intake, or drug use.

What key features are shared by all AB exotoxins

They have two subunits A and B They can be of three type

How can LD50 test be used to define virulence of a pathogen

LD50 is the lethal dose of a pathogen to kill 50% of test animal.

Identify factors necessary to support colonization of body by normal microflora

Normal microflora are ones that do do not cause harm to host. They can be found everywhere on the body but the major ones are: Skin Respiratory tract Urinary tract Digestive tract

Identify factors that influence susceptibility to infectious disease in infants and the aged

In very young infants the intestinal flora is not built up and is susceptible to pathogenic flora to invade. adults over 65 are more susceptible to respiratory tract infections and may result from influenza virus. A swollen prostate can lead to urinary tract infections due to the decrease in urine flow.

Describe host specificity for pathogens

Most of the pathogens prefer to colonize at certain host tissues only and not others. This is termed as tissue specificity and is affected by properties of both pathogen and host

Why might the small intestine be more suitable for growth of facultative aerobes than the large intestine.

The intestinal environment changes from oxygen rich to oxygen deficient gradually on descending down the intestinal tract. So Facultative aerobes can live in the small intestine. Upon reaching to the large intestine it becomes almost anoxic, thus supports exclusively obligate anaerobes.

Why do potential pathogens often found in the normal flora of the upper respiratory tract not cause disease in most cases

When we breathe most micro-organisms get trapped in the mucus membranes and expelled with nasal secretions or are swallowed. Also these pathogens are in competition by other resident flora to survive. This competition limits pathogenic activities. The immune system also plays a major role.