We hand on to the Readers attention the volume consecrated to selected problems of infectious diseases microbiology. Although infectious diseases microbiology belongs to very young medical science domains, has dynamically developed over the last two decades, mainly thanks to application of molecular studies in diagnosis of etiological factors of human and animal diseases. Currently, the classic methods of microorganisms’ cultures have been complemented with fast genetic tests confirming the disease process and important microorganism functions. Molecular epidemiology allows to identify the disease’s transmissions paths, defining risk factors of this transmission, may characterize interactions between the host and the pathogen, detect microorganism, that cannot be cultivated in vitro and allows better understanding of microorganisms pathogenesis on the molecular level.

Presenting the papers discussing modern studies in certain fields of infectious diseases microbiology to the physicians, we hope, that these will contribute to understanding of many directions of currently conducted scientific studies and the modern diagnostics that we dispose will bring benefit to the healthcare process.

Although we live in XXI century, papers concerning diseases induced by bacteria of Mycobacterium species still belong to important healthcare problems among other infectious diseases. Two species – Mycobacterium leprae and Mycobacterium tuberculosis, two of the oldest bacteria in the world still cause death of millions of humans.

Illustrative article on Mycobacterium leprae reminds that the leprosy still remains an important, global health problem, occurring not only in the third-world countries but also in many developed countries including European countries. WHO estimates the number of people affected by leprosy at 10-12 million. Despite its history developing over the centuries, leprosy diagnostics remains difficult, mainly due to many forms and clinical variations of the disease but also because of the lack of in vitro bacteria breeding method. Many phenomenons associated with bacilli survival outside the human body, supposed transmissions between humans, animals and possibly even the environment where bacteria survive, still remain unexplained. Long-term Dapson monotherapy has led to occurrence of forms resistant to medications and only multidrug treatment recommended by WHO in the eighties began to give desirable outcome.

Acknowledging the M.leprae genome in the nineties, provoked the discovery of many unknown bacteria survival features in human environment, and introduction of molecular microbiologic diagnostics to the clinical practice, allowed the identification of specific proteins giving opportunities for immunodiagnostic test development and elaborating new medications and vaccines in the future.

Other disease caused by Mycobacterium tuberculosis – tuberculosis – belongs to the group of the biggest human murderers. Number of deaths caused by tuberculosis, are on the second position after HIV and AIDS, concerning approximately 3 million people annually. Although the tuberculosis has been known as a disease for ages, its causing agent has been known for 100 years now and anti-tuberculosis drugs are available, it does not fall in, on the contrary – it increases in many world regions. Important aggravation of tuberculosis epidemic situation has become a fact and this disease cannot be any longer treated as an “ancient disease”. WHO recognized tuberculosis at the end of the past century as a population health threat of the global scale. Ethnic issues, war conflicts as well as easy touristic or economic population movements contribute to disease’s spread and transmission between humans. Fast patient diagnostics and antibacillary treatment introduction – those two elements belong to the most important methods of fighting tuberculosis. Drug resistant tuberculosis, particularly its MDR-TB and XDR-Tb variants, represent a serious problem of health threat and fight against the diseases on the global scale. Whilst a drug sensitive tuberculosis is a disease completely curable within a standard 6-month period, the treatment of resistant forms often requires 2 years or more and the cure is obtained merely in half of newly diagnosed and in 1/3 of previously treated patients. Also the mortality index is high. Gathering data on the drug resistance tuberculosis prevalence in newly diagnosed (primary drug resistance) and previously treated patients (acquired drug resistance) become an obligation imposed by WHO in the nineties. The paper included in the hereby volume discusses results of 4 consecutive studies conducted according to WHO protocol in Poland.

The serious drawback of drug resistance tests of tuberculosis bacilli, apart from the long result pending period (4 to 5 weeks), is a lack of availability of well standardized methods, which causes difficulties in clinical interpretation of drug resistance phenomenon. Difficulties with tuberculosis bacilli antibiogram standardization constitute only a part of methodical problems concerning also other diagnostic procedures such as: strain cultivation, bacterioscopy and determining the Mycobacterium species. Bacilli drug resistance tests are highly specialized test and according to WHO recommendations should be performed in III referral level laboratories. The next article discusses the above mentioned problems and studies results on the evaluation of a new, automatic cultivation system introduced in Poland in order to breed and test drug resistance of tuberculosis bacilli.

As mentioned above, WHO obliged all countries of the world to conduct regular epidemiologic studies covering four main antibacillary drugs. First choice drug group also includes pyrazinamide (PZA), which has not been tested for drug resistance due to lack of standardized method. The work, that we present, is a part of polish studies on the occurrence of drug resistance to PZA of tuberculosis bacilli in polish patients. The studies conclude that this prevalence is unexpectedly high and concerns not solely the strains isolated from the previously treated, but also from newly diagnosed patients. In view of the above fact, PZA drug resistance test should be included to the standard test panel in Poland.