Clinical Microbiology

Clinical microbiology. It is a branch of systematic biology and ecology that deals with microbes insofar as they are capable of causing disease in man. The viruses are infectious agents subcellular structure that microscopic size are grouped with microorganisms , although currently there are big discussions about their quality of living.


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  • 1 General aspects
  • 2 Objective
  • 3 Diagnosis of infectious disease
  • 4 Important aspects in clinical microbiology
  • 5 Role of the clinical microbiologist
  • 6 Source

General features

Infectious diseases have long been classified on the basis of purely clinical creiteries, although advances in microbiology have led to an etiological classification, and the agent that produces them is now known in almost all cases. Despite the disadvantages of this type of classification, there are so many advantages provided by an etiological classification that has been accepted, scientifically and practically, unanimously.

This classification system is a “natural” system, with very precise limits between one and other groups of causal agents.


The objective of clinical microbiology is to establish the etiology of an infectious disease, identifying an infectious agent, and to treat it to nullify the pathological effects of this microorganism. Among its tasks are diagnosis , epidemiology (study of the spread of disease), pathogenesis (study of the molecular mechanisms that cause disease) or prevention (vaccination and antibiotic treatment). The main human pathogens can be classified into one of these four taxonomic categories:

  • Viruses: HIV(AIDS virus), influenzavirus (of the flu), rotavirus (of acute gastroenteritis ).
  • Bacteria: Vibrio cholerae(causing cholera ), Corynebacterium diphtheriae (from diphtheria ), Clostridium tetani (from tetanus ).
  • Protozoa: Trypanosoma brucei(causing sleeping sickness ), Plasmodium falciparum (from malaria ), Leishmania donovani (from leishmaniasis).
  • Fungi: Candida albicans(from candidiasis ), Aspergillus fumigatus (from aspergillosis ), Trichophyton interdigitale (from ringworm ).

Diagnosis of infectious disease

The diagnosis of infectious diseases is based on two very different aspects:

  • Clinical diagnosis: it is based on the study of the clinical symptoms and signs that the disease produces in the patient
  • Laboratory diagnosis: it is based on the demonstration of the presence of the disease-producing agent or the trace that it has left in contact with the individual’s immune system.

The clinical diagnosis is in many cases quite demonstrative, but this presumptive diagnosis must be confirmed by a laboratory diagnosis. There are cases in which the clinic can only reach the syndromic diagnosis (case of acute meningitis, pleurisy , cystopielitis , among others) and only the Microbiology laboratory can reach a true diagnosis of the causative agent.

On the other hand, the same microorganism can give a great variety of clinical pictures, in one or more locations. The only confirmation of a clinical diagnosis is the etiological diagnosis, which is offered by the Clinical Microbiology Laboratory.

The Microbiology laboratory, when offering help to the clinical doctor against infectious diseases, offers three different paths with well differentiated objectives:

  • From the field of Bacteriologyand Mycology it is possible:
    • Isolate and identify pathogenic bacteria or fungi from clinical specimens.
    • Provide scales of antimicrobial susceptibility that allow the introduction of adequate antibiotics.
  • From the field of Serology itis possible:
    • Determination of the presence of pathogens in the body (direct detection of their antigens)
    • Determination of the footprint that these pathogens leave on the patient’s immune system (detection and quantification of the antibodies that our body produces against said pathogen).
  • From the field of Virology itis possible:
    • Isolate and identify viruses from clinical specimens.

Important aspects in clinical microbiology

  • Signs: are the objective manifestations that the individual presents.
  • Symptoms: The symptoms are the subjective manifestations, therefore the individual says the evaluation of the same.
  • Syndromes: it is the set of symptoms and signs that a certain germcauses .

The handling of specimens carries a risk, and this risk varies according to virulence (pathogenicity) and the type of germ. Therefore, biological safety standards must be taken into account that reduce the risk of handling the hazardous material to an acceptable level. Standards can be rigorous or less demanding.

Role of the clinical microbiologist

The man, as a patient or carrier of infections or infectious diseases, is the central axis of the clinical microbiologist’s work, whose work focuses on its diagnosis, epidemiological study and therapeutic orientation. The activity of the clinical microbiologist is centered in the Microbiology laboratory, whose technology and working methods are totally different from those of other clinical laboratories, and is projected towards the clinic to seek a better solution to human health problems.


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