FUNDAMENTALS OF MICROBIOLOGY - E. Yu. Tyumentseva - 2015

TOPIC 8. PATHOGENIC MICROORGANISMS

Infection (from Late Latin infectio - contamination) is the invasion and multiplication of microorganisms within a macroorganism, accompanied by The Development of Various Forms of interaction, ranging from pathogen carriage to clinically apparent disease.

Based on the localization of microorganisms, L. V. Gromashevsky proposed a Classification of infectious diseases. According to this primary criterion, all infectious diseases are divided into 4 groups:

1) intestinal infections;

2) respiratory tract infections;

3) Blood-borne infections;

4) integumentary (Skin and mucous membrane) infections.

Depending on their ability to cause disease, Bacteria are classified into:

1) pathogenic;

2) opportunistic (conditional pathogens);

3) saprophytic.

Pathogenic species are potentially capable of causing infectious diseases.

Pathogenicity is the ability of microorganisms, upon entering the body, to induce pathological changes in its Tissues and Organs. This is a qualitative species-specific trait determined genetically. A pathogen is any microorganism (including Fungi, Viruses, and bacteria) as well as a principal proteinaceous infectious particle, or prion, capable of causing a pathological state (disease) in another living Organism. In a broader sense, a pathogen is understood as any environmental factor capable of causing damage to bodily systems or triggering the development of diseases.

Foodborne toxicoinfections (FTI) represent a broad group of acute intestinal infections that develop after consuming foods contaminated with pathogens and their toxins.

Foodborne toxicoinfections can be caused by: 1) Salmonella; 2) Shigella; 3) opportunistic microorganisms (P. vulgaris, P. mirabilis, enterococci); 4) enterotoxigenic strains of staphylococci (St. aureus, St. albus); 5) streptococci (Group A beta-hemolytic streptococci); 6) spore-forming anaerobes (Clostridium perfringens); 7) spore-forming aerobes (Bac. cereus); 8) halophilic vibrios (Vibrio parahaemolyticus), etc.

Laboratory Procedure

Objective: To investigate hand hygiene (cleanliness of hands).

Materials, Reagents, and Equipment: Microscope; bacteriological loops and dissecting needles; spirit burner; metal tweezers; immersion oil; filter paper; test tubes containing 9 cm³ of sterile Water; Petri dishes; test tubes with sterile nutrient media: meat-peptone Agar (MPA) or medium for determining total viable count (TVC); Sabouraud agar or wort agar; Kessler's medium with Fermentation tubes (Durham tubes); set of Gram stains; iodine-starch solution (a mixture of 6% potassium iodide solution and 4% soluble starch solution in equal proportions); indicator paper for coliform bacteria (coliform group); filter paper; Glass microscope slides and cover slips; incubators; sterile 1 cm³ pipettes; 96% ethanol.

Experiment No. 1. Investigation of Hand Cleanliness

A sterile swab secured in metal tweezers is moistened with sterile water (or physiological saline) and used to wipe the palms, the back of the hands, under the fingernails, and between the fingers of both hands. The swab is then immersed in the test tube with water used for moistening, and the Contents of the tube are thoroughly

agitated, after which 1 cm³ is withdrawn to prepare serial dilutions (1:10 and 1:100).

To determine the total viable count (TVC), the dilutions are inoculated into Petri dishes containing meat-peptone agar, followed by incubation at 37 °C for 48 hours. The remainder of the wash fluid, along with the swab, is inoculated into test tubes containing 5 cm³ of Kessler's medium and cultured at 43 °C for 24 hours.

Recording of Results. Hand cleanliness is evaluated by the number of microorganisms per 1 cm³ of wash fluid in the absence of gas production in the Kessler medium tube with a fermentation tube (indicating the absence of Escherichia coli). When assessing the condition of the hands based on the content of mesophilic aerobic and facultatively anaerobic microorganisms (TVC) in the wash water, researchers follow the description provided in Table 4.

Class="center">Table 4. Evaluation of Hand Cleanliness

Hand cleanliness can also be tested using indicator papers designed to detect coliform bacteria. To do this, the indicator paper is moistened with sterile water and applied to the hand. The paper is then placed in a pouch, sealed, and incubated at 37 °C for 12 hours. The appearance of pink spots indicates the presence of coliforms.

During food handling operations, the effectiveness of hand sanitization with bleaching powder is periodically checked. For this purpose, specific areas of the hands are wiped with a cotton swab moistened with an iodine-starch solution (a 1:1 mixture of 6% potassium iodide solution and 4% soluble starch solution). If the swab and the skin surfaces in contact with it turn a blue-brown color, this indicates the presence of chlorine ions.

Recording and analysis of test results

Examine hand cleanliness, record the test results, and draw a Conclusion.

Upon completing this topic, students will master Methods for Assessing hand cleanliness, which is essential for ensuring safety in food production and handling.

Review Questions

1. What are the characteristic features and PROPERTIES OF PATHOGENIC microorganisms?

2. What are microbial toxins, and how potent are their effects?

3. What is an infection, and what are its SOURCES AND ROUTES of transmission?

4. What conditions are necessary for the onset and development of infectious diseases?

5. Which diseases are classified as foodborne, and how do foodborne infections differ from microbial food poisoning?

6. What are toxicoinfections?

7. How is the MICROBIOLOGICAL CONTROL OF workers' hand cleanliness conducted?

8. How is the effectiveness of hand sanitization with bleaching powder monitored?