We are placing the issue of „Medical Science Advances” into the hands of readers, prepared by specialists of different fields of medical microbiology. The set of articles relates to many aspects of bacterial infections. When presenting these articles to you, we wanted to draw attention to advance made in the clinical microbiology due to adopting molecular methods in diagnosis of microorganisms.

Last 15 years of the achievements of the Polish medical microbiology have significantly accelerated and increased the sensitivity of detection methods and contributed to a possibility of monitoring the ways of transmission of pathogenic factors. Without their implementation, the knowledge of medical services in Poland would be much poorer, not only within the understanding of pathogenicity of microorganisms but also within the rational diagnosis and treatment of patients. However, it should be added with sadness that micro and macro bacterial epidemics only when causing deaths among people, are receiving the media publicity for some period of time which calms very quickly and does not result in further financing of thorough examinations in the field of transmission, diagnosis and treatment.

In our issue we present also the matter of cross infections which are not only the problem of mycological laboratories and general bacteriology but also of TB laboratories. A misleading microbiological diagnosis which can be caused by laboratory cross infections results in mistakes in diagnosing a disease and consequently in a wrong therapy. All microbiological laboratories are threatened with errors resulting from cross-contaminations which are very difficult to counter. In daily work it is particularly important to be aware of an easy spread of bacteria by means of bacterial aerosols between examined samples from different patients. It is important to be aware that a proper supervision though allows for minimising the risk of those contaminations but it will not eliminate them completely.

Incorrect diagnosis of tuberculosis which is a consequence of cross-contamination during diagnostic procedures in TB laboratories is a known and described phenomenon and its prevalence is estimated at approximately 0.1-4%. Rapid detection and confirmation of cross infection requires from the microbiologist a thorough analysis of positive test results for tuberculosis.

The authors of the article highlight the importance of running a detailed microbiological documentation which allows for a precise indication of a way which was taken by a clinical material from the moment of collecting the material and its delivery to laboratory to the ending stage of diagnosis and presenting the result.

The authors of the article, while discussing this issue, acquaintance us with the works of foreign authors and on the basis of own experiences i.e. detection of strains of Mycobacterium tuberculosis, namely the „false” ones in TB laboratory, propose the algorithm of examinations verifying the correctness of performing the procedures of microbiological diagnosis and methods of preventing the contaminations.

Further articles refer to the problem of a drug-resistant tuberculosis. The presence of tubercular bacilli among the sick inhabiting 4 regions of Poland called the „Eastern Wall” was the subject of molecular examinations. It was discovered that about 80% of analysed patients excreted the strains of the tubercular bacilli belonging to molecular formula previously registered in Poland and at our neighbours – in Czech Republic, Latvia and in Russia.