Etiology and Classification of Disorders
Disruptions in the body's microecology rarely occur spontaneously. Major risk factors include iatrogenic interventions (uncontrolled antibiotic therapy, consequences of chemo- and radiotherapy, major surgical procedures), poor nutrition (dietary factor), as well as environmental influences and severe stress.
Classification of dysbiotic states is based on several principles:
- By etiology: Proteus-associated, staphylococcal, fungal, and other types of disorders depending on the dominant pathogen.
- By localization: Lesions can affect the oral cavity, vagina, or intestines.
Intestinal disorders have specific features. Isolated colon dysbiosis is distinguished from specific small intestine pathology known as SIBO (small intestinal bacterial overgrowth, or Bacterial overgrowth syndrome).
Such flora disturbances are associated with a vast spectrum of diseases. Gastrointestinal manifestations include diarrhea or constipation, gastritis, colitis, peptic ulcer disease, and malabsorption syndrome. Systemic disturbances include blood pressure fluctuations (hypo- and hypertension) and cholesterol levels, urolithiasis, and allergies. Furthermore, flora imbalance increases the risk of dental caries, liver lesions, arthritis, and even malignancies.
Methods of Microbiocenosis Diagnostics
To accurately assess the state of the flora, a comprehensive approach is used. The clinician's and microbiologist's arsenal includes three basic methods:
- Bacteriological (classical culture of material).
- Molecular-genetic (PCR diagnostics).
- Instrumental-analytical (chromatography-mass spectrometry).
Metabolite analysis holds a special place. Using gas-liquid chromatography (GLC), specialists determine the level of short-chain fatty acids, which serve as markers of anaerobic bacterial activity.
Biochemical diagnostics relies on searching for specific metabolic products (aldehydes, enzymes, hydroxy fatty acids) indicating imbalance. A classic example is the detection of dipeptides ($eta$-aspartyl-glycine and $eta$-aspartyl-lysine) in patient stool. Normally, these substances are fully metabolized by healthy anaerobic flora, so their presence in the assay reliably indicates a disruption of intestinal microbiocenosis.
Bacteriological Method and Selective Media
Classical microbiological diagnostics aims to determine the quantitative and species composition of a biotope (oropharynx, skin, intestine). The impression method or seeding of dilutions of the studied material onto nutrient media is used for this purpose.
It is crucial for students to memorize the correspondence of specific microorganism groups to elective media for their cultivation:
- Bifidobacteria: Blaurock's medium.
- Lactobacilli: MRS-2 medium.
- Bacteroides: Anaerobic blood agar.
- Enterobacteria: Levin's or Endo media.
- Enterococci: Bile-blood agar.
- Streptococci and Haemophilus: Blood agar.
- Pseudomonas aeruginosa: Meat-peptone agar (MPA) supplemented with furagin.
- Fungi: Sabouraud medium.
Treatment Principles and Drug Groups
The foundation of dysbacteriosis correction is selective decontamination of pathogens and oral administration of specialized preparations to restore normoflora.
Several key drug groups are distinguished:
- Prebiotics. These are microbial components or non-microbial substances that stimulate the growth of beneficial host flora. Chemically, they are low-molecular-weight carbohydrates (oligosaccharides, fructooligosaccharides). They are naturally found in food products and breast milk.
- Probiotics (eubiotics). Live bacteria-based preparations. Divided into two subgroups. The first contains members of normal flora (bifidobacteria, lactobacilli, Escherichia coli — e.g., bifidumbacterin or colibacterin). The second group consists of self-eliminating antagonists. They do not normally inhabit the body, but effectively suppress pathogens and are then completely excreted (examples: Bacillus subtilis bacteria or yeast fungi Saccharomyces boulardii).
- Synbiotics. Combined agents simultaneously containing live bacteria (probiotic) and a nutrient medium for them (prebiotic).
- Enterosorbents. Used for binding and excreting toxic metabolites and opportunistic microorganisms from the intestinal lumen (e.g., enterosgel or activated charcoal).