microbiology chapter 26

The purpose of decontamination methods is to eliminate microbial growth.

f

The quinolones are synthetic antibacterial compounds that

A) inhibit bacterial DNA gyrase.

Of all the known antibiotics that have been identified in nature, ________ are clinically useful.

A) <1%

Semisynthetic antibiotics

A) are natural antibiotics that have been chemically modified in the laboratory.

Polyoxins interfere with

A) cell membrane synthesis.

In the agar diffusion method of studying antimicrobial action, the ________ is measured.

A) diameter of the zone of inhibition

Interferon is specific to the

A) host cell.

Compared with decontamination, disinfection is

A) more aggressive.

Erythromycin acts as a(n)

A) protein synthesis inhibitor at the level of the 50S subunit of the ribosome.

The process by which macromolecules lose their structure and ability to function is called

A)denaturation

Highly active anti-retroviral therapy (HAART), which involves a combination of nucleoside analogs and protease inhibitors, is most commonly used to treat infections of

B) HIV.

Agents that kill bacteria are said to be

B) bacteriocidal.

The action of some bacteriolytic chemical agents can be observed by noting a(n)

B) decrease in the turbidity of the medium.

UV radiation is antimicrobial, because

B) energy present causes modifications or breaks in the DNA molecules.

The Beta-lactam antibiotics

B) inhibit cell wall synthesis.

The most successful agents used for antiviral chemotherapy are

B) nucleoside analogs.

The complete elimination of all microorganisms, including viruses, is called

B) sterilization.

Which of the following antimicrobial treatments is affective only on exposed surfaces?

B) ultraviolet rays

A ________ filter is most often used to filter sterilize liquids.

B)membrane

Common radioactive isotopes for sterilization are

C) cobalt and cesium.

Cold sterilization is performed using

C) compounds such as ethylene oxide.

The time required for a tenfold reduction of the viability of a microbial population at a given temperature is called the ________ time

C) decimal reduction.

Ergosterol inhibitors specifically target

C) fungi.

Neuraminidase inhibitors such as oseltamivir and zanamivir are used to treat which type of infection?

C) influenza virus

A ________ filter is most often used in scanning electron microscopy.

C) nucleation track

At present, the penicillins and the cephalosporins account for ________ of all the antibiotics produced and used worldwide.

C) over 50%

The vegetative cells of Mycobacterium tuberculosis are resistant to many germicides because of

C) the waxy nature of the cell wall.

The thermal death time is the

C) time it takes to kill all cells at a given temperature.

Which is NOT a reason why microorganisms may have an inherent natural resistance to an antibiotic?

D) The organism may be protected from the drug by its nuclear membrane.

Which statement is TRUE about heat sterilization?

Microbial death is more rapid at an acidic pH. High concentrations of sugars and salts influence sterilization time. The amount of water in a substance is a major factor in heat resistance. D) All of the above are true.

Pasteurization is synonymous with sterilization; the only difference is that the term pasteurization is used with heat sensitive foods.

f

Because of their limited range of effectiveness, the fluoroquinolones are used primarily in treating infections caused by gram-positive Bacteria.

f

Because of their particulate nature, electrons are not considered a form of electromagnetic radiation.

f

Cephalosporins contain a double -lactam ring, whereas the penicillins contain a single -lactam ring. (Beta)

f

Drug resistance to the sulfonamides has remained low while many other types of antibiotics have remained constant.

f

In general, vegetative cells are more heat resistant than bacterial endospores.

f

Many countries, such as Australia, France, Germany, and the United States, decontaminate and sterilize certain foods with ionizing radiation.

f

Which of the following are classified as electromagnetic radiation?

microwaves ultraviolet rays X-rays and gamma rays D) all of the above

Antimicrobial drugs are often grouped according to

molecular structure. spectrum of antimicrobial activity. mechanism of action. D) all of the above.

Important targets of antibiotics in Bacteria are

the cell wall. the cytoplasmic membrane. DNA replication and transcription elements. D) all of the above.

A thermometer can be sterilized using a cold sterilization method.

t

Antiseptics may either kill or inhibit the growth of microorganisms and are sufficiently nontoxic to be applied to living tissues.

t

Bacteriolytic agents can inhibit cell wall synthesis.

t

Bacteriostatic agents inhibit bacterial growth but do not specifically kill the organisms against which they are directed.

t

Both cephalosporins and penicillins have the same mode of action, despite the two having different chemical structures.

t

Endospore heat resistance is determined by the concentration of small acid-soluble proteins (SASPs) and water content of the endospore.

t

Growth factor analogs that resemble nucleic acids are used in the treatment of viral and fungal infections.

t

In practice, sterility is difficult to achieve.

t

Isoniazid interferes with the synthesis of the mycobacterial-specific mycolic acid cell wall material.

t

Many Neisseria gonorrhoeae strains have developed -lactamases that cleave the -lactam rings, which provides them with resistance to certain antibiotics.

t

Most attempts at chemical control of viruses result in toxicity for the host.

t

Radiation is a decontamination measure approved by the World Health Organization (WHO) for foods particularly susceptible to microbial contamination.

t

Semisynthetic penicillins are generally more broad-spectrum than natural penicillins.

t

The CDC has developed a 12-step prevention program for the prevention of resistance to antimicrobial agents aimed primarily for hospitalized individuals.

t

The antimicrobial effects of microwaves are due, at least in part, to thermal effects.

t

The first widely used growth factor analogs specifically designed to inhibit bacterial growth were the sulfa drugs.

t

The term antimicrobial agent includes both fungicidal and fungistatic agents.

t

The tetracyclines are protein synthesis inhibitors that specifically disrupt the function of bacterial 30S ribosomes.

t