Bacterioscopy is a diagnostic technique that allows you to quickly and simply identify the occurrence of infections, because through specific staining techniques, it is possible to visualize bacterial structures under the microscope.
This test can be done with any biological material, and the doctor must indicate which material is to be collected and analyzed, and the result indicates whether the presence of bacteria was verified or not, as well as its quantity and visualized characteristics.
What is it for
Bacterioscopy is a diagnostic test that can be done with any biological material and can be used to quickly identify bacterial infections:
- Sexually transmitted diseases, such as gonorrhea and chlamydia, for example, with penile or vaginal secretion being used for this purpose. The collection is made through the use of a sterile swab and it is contraindicated to perform the cleaning of the genital region 2 hours before the exam and not to have sex in the 24 hours before the collection; Tonsillitis, because through the collection of throat secretion, it is possible to identify gram-positive bacteria responsible for inflammation in the amygdala, with streptococcus-type bacteria usually being identified; Infections in the urinary system, which is done by analyzing first-stream urine; Tuberculosis, in which sputum is analyzed; Infections in surgical wounds, as it is common for infections to occur after operations due to the decrease in the person's immune system. Thus, the collection of secretion from the wound can be indicated with a sterile swab to verify the possible presence of bacteria in the area; Skin or nail lesions, which consists of collecting a superficial sample, being indicated not to use creams and enamels at least 5 days before the exam. Although bacterioscopy can be performed, fungi are usually observed when analyzing the nail sample, for example.
In addition, bacterioscopy can be used to assist in the diagnosis of bacterial meningitis, respiratory and gastrointestinal diseases, and can be done through biopsy or material from the anal region.
Thus, bacterioscopy is a laboratory technique that can be used in clinical practice to diagnose diseases caused by bacteria, indicating the characteristics of the causative agent of the disease and, thus, allowing the doctor to start treatment even before identification in the laboratory, which can take about 1 week.
How it is done
The bacterioscopy exam is done in the laboratory and the material collected from the patient is analyzed under a microscope to investigate the absence or presence of bacteria, in addition to their characteristics.
The preparation for taking the exam depends on the material that will be collected and analyzed. In the case of vaginal material, it is not recommended that the woman clean 2 hours before the exam and do not have sex in the last 24 hours, while in the case of collection of material from the nail or skin, for example, it is recommended not to pass enamel, creams or substances on the skin before the exam.
In the case of a sample of vaginal discharge, for example, the swab that was used to perform the collection is passed in circular movements on a slide, which must be identified with the patient's initials, and then stained with Gram. In the case of sputum samples, for example, which is the material collected mainly to check for the presence of the bacteria responsible for tuberculosis, the color used in bacterioscopy is that of Ziehl-neelsen, which is more specific for this type of microorganism.
Usually when the presence of bacteria is verified, the laboratory performs the identification of the microorganism and the antibiogram, giving a more complete result.
How Gram stain is done
Gram staining is a simple and fast staining technique that allows bacteria to differentiate according to their characteristics, allowing bacteria to be differentiated into positive or negative according to their color, allowing them to be viewed under the microscope.
This staining method uses two main dyes, a blue and a pink, which may or may not stain the bacteria. Blue-stained bacteria are said to be gram-positive, while pink bacteria are called gram-negative. Based on this classification, it is possible for the doctor to start preventive treatment, even before having the identification of the microorganism.
Understand how Gram stain is done
Bacterial identification by means of gram staining is quick, practical and inexpensive to perform, being essential for doctors, since specific characteristics of these groups of bacteria are already known, and the doctor may indicate a preventive treatment based only on gram staining.
This staining is based on the differentiation of bacteria according to the characteristics of the cell wall. Gram-positive bacteria have more than one thick peptideoglycan wall, being able to retain the first dye well, while gram-negative bacteria have a thinner wall, which can be easily discolored when exposed to alcohol.
Gram staining is done in 5 main steps, but the protocol may vary depending on the laboratory:
- Cover the slide with the violet crystal dye and let it act for about 1 minute; Wash the slide with a stream of running water and cover the slide with lugol, which aims to fix the blue dye, and let it act for 1 minute. Both types of bacteria can absorb the complex formed by the dye and the lugol, turning blue; Then, wash the slide with running water and apply 95% alcohol, leaving it to act for 30 seconds. Alcohol is responsible for dissolving the lipid membrane that forms gram-negative bacteria and, thus, removing the complex formed between the dye and the lugol, discoloring these bacteria. However, in the case of gram-positive bacteria, the alcohol dehydrates the cell wall of the gram-positive bacteria, causing the pores to contract and making them impermeable; then, wash in running water and cover the slide with the second dye., fuchsin or safranin and let it act for 30 seconds; then, the slide should be washed with running water and allowed to dry at room temperature.
As soon as the slide is dry, it is possible to place a drop of immersion oil and observe the slide in the microscope with a 100x objective, being possible to check the presence or absence of bacteria, as well as the presence of yeasts and epithelial cells.
What the result means
The result of bacterioscopy aims to indicate whether there is presence or absence of microorganisms, characteristics and quantity, in addition to the material that was analyzed.
The result is said negative when microorganisms are not observed and positive when microorganisms are visualized. The result is usually indicated by crosses (+), where 1 + indicates that 1 to 10 bacteria were seen in 100 fields, which may be indicative of an initial infection, for example, and 6 + represents the presence of more than 1000 bacteria per observed field, representing a more chronic infection or bacterial resistance, for example, indicating that the treatment is not being effective.
In addition, the color used was reported in the report, which may be Gram or Ziehl-neelsen, for example, in addition to the characteristics of the microorganism, such as shape and arrangement, whether in clusters or in chains, for example.
Normally, when the result is positive, the laboratory identifies the microorganism and antibiogram, indicating which antibiotic is most recommended to treat infection by a certain bacterium.
