5 Control of Microbial Growth

physical

[__] methods of controlling bacteria growth include

• heat

• irradiation

• filtration

• mechanical removal

chemical

[__] methods of controlling bacteria growth include use of antimicrobial chemicals

Sterilization

Treatment that destroys all microbes (including endospores and viruses)

Disinfection

Treatment that removes most microbes, but not all

Done through:

• Disinfectants: chemicals used on inanimate objects and surfaces

• Antiseptics: chemicals used on living tissues

Pasteurization

Brief heating to destroy spoiled organisms and pathogens to prolong food life and ensure that we don’t get sick

Preservation

Process to delay spoilage of perishable products

done through

• adjusting storage conditions → putting food in fridge

• adding preservatives: chemical additives to prevent spoilage

hand washing

Routine control done daily by routinely washing and scrubbing with soaps and detergents

• mechanically removes microbes

• beneficial skin microbiota not adversely affected by regular use

• [__] with soap and water most important step in stopping spread of many infectious diseases

health-care associated infections

Important to minimize infection in hospitals due to [__]: diseases people acquire when they go to health care facilities

in addition to the fact that

• hospital patients are more susceptible to infection

• some patients undergo invasive surgery

  • instruments must be sterilized to avoid introducing infection to deep tissues

  • operating room must be cleaned critically

• pathogens found in hospital are very resistant to antimicrobial agents

aseptic techniques

In microbiology laboratories, we undergo [__]: practices we do to prevent contamination of samples, self, and laboratory

• must treat media before and after use

  • before treatment » eliminates unwanted organisms

  • after treatment » prevents contamination of environment

Heat

The most common method to destroy, remove, or inhibit contaminating microbes for food. Increases shelf-life

• can alter flavor and appearance of products

done in addition to:

• irradiation → approved to treat certain foods

• preservatives: chemical additives to prevent spoilage

chlorine

In Water Treatment Facilities, control involves ensuring that water is free of pathogens

This is done through adding [____], a traditional disinfectant of water

Cryptosporidium parvum

Some organisms are resistant to chemical disinfectants in the water. eg. [____]: a protozoan that causes diarrhea, and is resistant to chlorine.

No.1 cause of diarrhea is when someone with [___]-caused diarrhea goes swimming, and chlorinated swimming pools cannot rid of the protozoan

ideal

Selection of effective procedure is complicated; an [___] method does not exist

depends on numerous factors:

• type and no. of microbes

  • most important, as microbes can be highly resistant

• environmental conditions

• risk of infection

• composition of infected item

Bacterial endospores

Type of microorganism that is most resistant

Only extreme heat or chemical treatment can destroy them

Protozoan cysts and oocysts

Type of microorganism that is resistant to disinfectants.

Excreted in feces, causes diarrheal disease if ingested

Mycobacterium species

This genus’ species has waxy cell walls, which makes them resistant to many chemical treatments

Pseudomonas species

This genus’ species is resistant to and can actually grow in some disinfectants