Comparison of Kinetics of Antibody Avidity and IgG Subclasses' Response in Patients with COVID-19 and Healthy Individuals Vaccinated with the BNT162B2 (Comirnaty, Pfizer/BioNTech) mRNA Vaccine.

There are limited reports concerning the levels of antibodies in IgG subclasses and the avidity of IgG, which is the functional strength with which an antibody binds to an antigen in serum samples obtained at different times after infection or vaccination. This study investigated the kinetics of antibody avidity and the IgG antibody response within IgG1-IgG4 subclasses in individuals vaccinated with the BNT162B2 mRNA vaccine and in COVID-19 patients. Serum samples were collected from individuals vaccinated with three doses of the BNT162B2 (Comirnaty, Pfizer/BioNTech) vaccine and from unvaccinated COVID-19 patients. This study revealed that IgG1 was a dominating subclass of IgG both in COVID-19 patients and in vaccinated individuals. The level of IgG4 and IgG avidity significantly increased 7 months after the first two doses of the vaccine and then again after the third dose. IgG2 and IgG3 levels were low in most individuals. Investigating IgG avidity and the dynamics of IgG subclasses is essential for understanding the mechanisms of protection against viral infections, including COVID-19, especially in the context of immunization with innovative mRNA vaccines and the possible future development and application of mRNA technology.

Seroprevalence of Helicobacter pylori infections in children and adults in Poland in the years 2020-2023.

Introduction: Helicobacter pylori is a common cause of gastrointestinal infections in people around the world. Various microbiological methods are used in the laboratory diagnosis of infections, including determining the presence of specific antibodies in the serum. Serological tests can also be used in epidemiological studies aimed at determining the incidence of H. pylori infections. Objective: The aim of the study was to obtain insight into the incidence of antibodies to H. pylori in subjects of different ages living in Poland in the years 2020-2023. Material and methods: The research used serum samples obtained between January 2020 and September 2023 from 600 subjects living in Poland. The Anti-Helicobacter pylori ELISA IgG enzyme immunoassay from Euroimmun was used to test the level of IgG antibodies to H. pylori antigens. Additionally, selected serum samples were tested for the presence of antibodies to the most important protein virulence factors of H. pylori by Western Blot. Results: IgG antibodies to H. pylori, at a diagnostically significant level, were detected in 28.3% of the examined persons. Antibodies to H. pylori were least frequently detected in children under 10 years of age (12.1%) and teenagers (13.2%). In adults aged 20 to 50, these antibodies were more common (23.9% to 29.5%). Statistically, H. pylori antibodies were most often detected in subjects over 50 years of age (52.3%). There were no statistically significant differences in the frequency of antibodies to H. pylori depending on the gender of the examined persons. In most serum samples tested by Western Blot, the presence of antibodies to the CagA protein was detected (66.7%). Conclusions: The conducted research and analysis of literature data showed a similar percentage of serum samples with a diagnostically significant level of antibodies to H. pylori in people living in Poland as in people living in other European countries. The epidemiology of infections is also very similar, characterized by low morbidity in children and adolescents and an increase in the incidence of infections with the age of the examined persons. Importantly, compared to research conducted in our country several years ago, the percentage of positive results is much lower, which may be due to the improvement of social and living conditions and hygiene habits.

Detection of SARS-CoV-2 Using Reverse Transcription Helicase Dependent Amplification and Reverse Transcription Loop-Mediated Amplification Combined with Lateral Flow Assay.

Rapid and accurate detection and identification of pathogens in clinical samples is essential for all infection diseases. However, in the case of epidemics, it plays a key role not only in the implementation of effective therapy but also in limiting the spread of the epidemic. In this study, we present the application of two nucleic acid isothermal amplification methods-reverse transcription helicase dependent amplification (RT-HDA) and reverse transcription loop-mediated amplification (RT-LAMP)-combined with lateral flow assay as the tools for the rapid detection of SARS-CoV-2, the etiological agent of COVID-19, which caused the ongoing global pandemic. In order to optimize the RT-had, the LOD was 3 genome copies per reaction for amplification conducted for 10-20 min, whereas for RT-LAMP, the LOD was 30-300 genome copies per reaction for a reaction conducted for 40 min. No false-positive results were detected for RT-HDA conducted for 10 to 90 min, but false-positive results occurred when RT-LAMP was conducted for longer than 40 min. We concluded that RT-HDA combined with LFA is more sensitive than RT-LAMP, and it is a good alternative for the development of point-of-care tests for SARS-CoV-2 detection as this method is simple, inexpensive, practical, and does not require qualified personnel to perform the test and interpret its results.

Comparison of anti-SARS-CoV-2 IgG and IgA antibody responses post complete vaccination, 7 months later and after 3rd dose of the BNT162b2 vaccine in healthy adults.

BACKGROUND: The mRNA Covid-19 vaccine (BNT162b2) is administered in two doses with 21 days interval. On 4th October 2021 European Medicines Agency approved administration of a booster dose in at least 6 months after the second dose for people aged 18 years and older. OBJECTIVES: In the present study we compare the anti-SARS-COV-2 IgG and IgA antibody responses post complete vaccination, 7 months later and after the 3rd (booster) dose of the BNT162B2 vaccine in healthy adults. STUDY DESIGN: The levels of vaccine IgG and IgA antibodies to SARS-CoV-2 were assessed in serum samples obtained from individuals vaccinated with two doses and a booster of BNT162b2 vaccine. Samples were tested using the SARS-CoV-2 receptor-binding domain (RCB) IgG and IgA semi-quantitative commercial ELISA assay. RESULTS: The geometric mean of the anti-SARS-COV-2 IgG and IgA antibody level 7 months after vaccination of 90 healthy adults with BNT162B2 vaccine decreased significantly from 12.0 to 5.4 and 5.6 to 2.3, respectively. After the third dose of the same vaccine, the antibody level increased again, to values higher than at the beginning after the second dose. CONCLUSIONS: Significant decrease of antibody levels within a few months after full vaccination could result in the higher risk of SARS-CoV-2 infection, especially when new variants of the virus emerge. The booster could be crucial for protection against new SARS-CoV-2 variants. The antibody level seems to decrease slower in vaccinated individuals with history of COVID-19 and in younger individuals.

Tularaemia - a diagnostic challenge.

INTRODUCTION AND OBJECTIVE: Tularaemia is an infrequently occurring disease in Poland. It has therefore rarely been taken into account in the differential diagnosis of skin lesions, lymphadenitis, or soft tissue abscesses. This fact, accompanied by non-specific initial presentation, may lead to a delay in diagnosis and a more severe course of the disease. Objective. The aim of the study is to present the current state of knowledge on tularaemia and convince medical professionals to take it into consideration in the diagnosis of skin lesions, lymphadenitis, and tissue abscesses. REVIEW METHODS: A literature review using PubMed and other online resources, using terms including 'tularaemia', 'lymphadenitis', etc., was undertaken. Papers were reviewed for relevance and scientific merit. ABBREVIATED DESCRIPTION OF THE STATE OF KNOWLEDGE: Tularaemia, also known as 'rabbit fever', is a zoonotic infection caused by Francisella tularensis, an aerobic, facultative intracellular, gram-negative bacteria. In Europe, it is mainly spread via tick bites and contact with wild animals such as lagomorphs and rodents. Clinical presentation may differ depending on the transmission route; the ulceroglandular and glandular forms of disease predominate. An early diagnosis and implementation of appropriate antibiotic therapy are the cornerstones of successful treatment and make it possible to avoid a surgical incision and drainage of suppurative complications. SUMMARY: Raised awareness and knowledge on tularaemia among health care professionals are required for timely diagnosis and treatment. Arrival from endemic areas, contact with wild animals, tick bites, and exclusion of more common etiologies of presenting signs should prompt consideration of tularaemia. More research is needed for a better understanding of the burden of the disease and its impact on public health in Poland.

Duration of protection against Bordetella pertussis infection elicited by whole-cell and acellular vaccine priming in Polish children and adolescents.

BACKGROUND: In the context of reported resurgence of pertussis in the last decade, researchers hypothesized that acellular (aP) pertussis vaccines elicit a shorter-lived protection compared to whole-cell (wP) pertussis vaccines. However, in the studies seeking to demonstrate this hypothesis, exposure to each vaccine type was not concurrent, and contradictory epidemiologic modeling questioned its validity. The context of pertussis vaccination history in Poland, with both vaccine types used concurrently in comparable proportions, provided an opportunity to investigate this hypothesis. We sought to compare waning of protection by primary series vaccine type by measuring anti-pertussis toxin antibody concentrations as proxy for recent infection. MATERIALS AND METHODS: Serological samples from 2,745 children and adolescents aged ≥5 years and <16 years and with completed 5-dose pertussis vaccination series were tested by ELISA for pertussis toxin (PT) antibodies. Participants were stratified by type of priming vaccine (wP or aP). Vaccination timeliness and priming-specific trends in anti-PT antibody levels by time since last vaccine dose were analyzed. RESULTS: A total of 1,161 (42.5%) children received wP vaccines, and 1,314 (48.1%) received aP vaccines for their primary series and toddler booster. Overall, 53.57% of the subjects received doses 2-4 in a timely manner, while only 41.52% received all 5 doses at the recommended intervals. Using GMCs or seropositivity measures, both priming groups showed a re-increase in anti-PT antibody levels signing infection in recent years from 8 years after the school-entry booster onward. Comparisons did not show any significant differences between the two groups in the timing or intensity of this re-increase. CONCLUSION: Our results clearly confirm that vaccine-elicited immunity against pertussis wanes among adolescents even after a complete infant, toddler and school-entry vaccination series. The timing and intensity of the waning of protection appear similar with whole-cell as with acellular pertussis vaccines.

The level of protective post-vaccination antibodies in NIPH-NIH employees after administration of Pfizer vaccine against COVID-19.

INTRODUCTION: The new SARS-CoV-2 coronavirus, first recognized in China in 2019, within a few months caused a global pandemic of a disease called COVID-19. The high incidence and mortality of COVID-19 was the reason for the beginning of intensive work on the development of an effective vaccine. In Poland, mass vaccinations against this disease began at the end of December 2020. OBJECTIVES: The aim of the presented study was to determine the effectiveness of stimulating the production of specific antibodies for SARS-CoV-2 by the Pfizer vaccine. MATERIAL AND METHODS: The presence of IgA and IgG antibodies to the spike (S protein) of SARSCoV-2 was tested by the ELISA/Euroimmun in serum samples obtained from 140 the employees of NIPH-NIH (137 were vaccinated). In addition, the presence of IgG antibodies to S protein, nucleoprotein, and mixture of both in selected serum samples was tested by the newly developed in NIPH-NIH in-house ELISA assay. RESULTS: IgA and IgG antibodies to the S protein of the SARS-CoV-2 were detected by ELISA/Euroimmun, respectively in 136 and in all 137 vaccinated persons. There were no statistically significant differences in the level of antibodies depending on the sex and age of the vaccinated persons. Slightly higher levels of antibodies have been demonstrated in vaccinated subjects with documented preexisting SARS-CoV-2 immunity compared to subjects without COVID-19 history. The presence of IgA and IgG antibodies was found in respectively, 18 (45.0%) and all 40 (100.0%) tested vaccinated persons by the in-house ELISA with mixture antigen. The study showed that ELISA assay with N protein as an antigen may enable the distinction between antibodies acquired after infection and after vaccination. CONCLUSIONS: The results obtained in the presented study clearly demonstrate the high effectiveness of the Pfizer vaccine in stimulation of the human immune system to produce antibodies specific for the S protein of the SARS-CoV-2. It is necessary to continue testing vaccine antibody levels at various times after vaccination to determine the potential duration of humoral immunity.

Pertussis seroprevalence among adults of reproductive age (20-39 years) in fourteen European countries.

The reported incidence of pertussis in European countries varies considerably. We aimed to study specific Bordetella pertussis seroprevalence in Europe by measuring serum IgG antibody levels to pertussis toxin (anti-PT IgG). Fourteen national laboratories participated in this study including Belgium, Denmark, Finland, Greece, Hungary, Italy, Lithuania, Malta, Norway, Poland, Portugal, Romania, Spain, and Sweden. Each country collected approximately 250 samples (N = 7903) from the age groups 20-29 years (N = 3976) and 30-39 years (N = 3927) during 2010-2013. Samples were anonymous residual sera from diagnostic laboratories and were analyzed at the national laboratories by a Swedish reference method, a commercial ELISA kit, or were sent to Sweden for analysis. The median anti-PT IgG concentrations ranged from 4 to 13.6 IU/mL. The proportion of samples with anti-PT IgG ≥100 IU/mL, indicating a recent infection ranged from 0.2% (Hungary) to 5.7% (Portugal). The highest proportion of sera with anti-PT IgG levels between 50 and <100 IU/mL, indicating an infection within the last few years, was found in Portugal (12.3%) and Italy (13.9%). This study shows that the circulation of B. pertussis is quite extensive in adults, aged 20-39 years, despite well-established vaccination programs in Europe.

Characteristics and assessment of the usefulness of serological tests in the diagnostic of infections caused by coronavirus SARS-CoV-2 on the basis of available manufacturer's data and literature review.

Recognized in 2019 in Wuhan, China, the new SARS-CoV-2 coronavirus is responsible for the occurrence of a global pandemic disease called COVID-19. So far, confirmation of infection is based on the detection of virus RNA in a sample taken from a person meeting the suspected case definition. However, in the laboratory diagnosis of SARS-CoV-2 infections, in addition to genetic tests, serological methods can also be used to detect specific antibodies of the IgM, IgG and IgA class produced after contact with antigens or to detect viral antigen. Currently, a number of rapid immunochromatographic, chemiluminescent and ELISA immunoassay tests developed by different manufacturers for the diagnosis of COVID-19 are available on the market. Despite this fact, so far there is no WHO or ECDC recommendations or even reliable research regarding the usefulness of serological investigations in the laboratory diagnosis of infections caused by SARS-CoV-2.

Development and Evaluation of a Latex Agglutination Test for the Identification of Francisella tularensis Subspecies Pathogenic for Human.

Francisella tularensis are highly infectious bacteria causing a zoonotic disease called tularemia. Identification of this bacterium is based on antigen detection or PCR. The paper presents a latex agglutination test (LAT) for rapid identification of clinically relevant F. tularensis subspecies. The test can be performed within three minutes with live or inactivated bacteria. The possibility to test the inactivated samples reduces the risk of laboratory acquired infection and allows performing the test under BSL-2 conditions.

Francisella tularensis/Rickettsia spp. co-infections in patients with skin changes and lymphadenopathy.

INTRODUCTION: Tularemia and spotted fever group rickettsioses (SFG) can be transmitted by ticks and have a number of common clinical symptoms. Most characteristic are a maculopapular or vesicular rash or an eschar at the site of the tick or insect bite accompanied by painful lymph nodes. The aim of this study was to determine whether Rickettsia spp./Francisella tularensis mixed infections occurred in patients with similar symptoms who were diagnosed with either Rickettsia spp. or F. tularensis infection. MATERIAL AND METHODS: Thirty-six cases from 2011-2014, including 15 individuals with clinically and serologically recognized SFG and 21 with tularemia, were analyzed retrospectively using immunofluorescence for detection of Rickettsia spp. or ELISA for detection of F. tularensis. RESULTS: Of the 36 cases examined, specific high titers of antibodies to Rickettsia spp. were found in 1 (4.4%) patient with tularemia and specific high titers of antibodies to F. tularensis were detected in 1 (6.7%) patient with SFG. CONCLUSIONS: The results of our study show that in infections with fever, enlarged lymph nodes and skin lesions after tick and insect bites, laboratory testing of both diseases - SFG rickettsiosis and tularemia - should be implemented. Identification of F. tularensis and Rickettsia spp. mixed infections is crucial in order to administer appropriate antibiotics and to avoid treatment failure and relapse.

Development and evaluation of latex agglutination tests for the detection of human antibodies to the lipopolysaccharides of verocytotoxin-producing Escherichia coli (VTEC) serogroups O157 and non-O157.

Latex agglutination tests (LAT) were developed and evaluated for the rapid detection of LPS antibodies against E. coli serogroup O157, O26, O104, O111 and O145. The latex tests have been proved to be sensitive, fast, easy-to-perform and cost-efficient tools for the screening serodiagnosis of VTEC infections causing haemolytic-uraemic syndrome.

[The occurrence of infections caused by Francisella tularensis in humans in Poland and laboratory diagnosis of tularemia].

Tularemia is a serious infectious zoonotic disease, caused by Gram-negative bacterium Francisella tularensis. Natural reservoir of infection are small mammals such a mice, voles, squirrels and rabbits. Transmission to humans occurs through contact with infected animals or contaminated environments, or through arthropod vectors. Because of its extreme infectivity it is a dangerous biological agent to human health. Tularemia has a broad geographical distribution, however is mainly in the northern hemisphere, in areas with cooler climates particularly in North America, Europe, Russia and Japan. Most of the cases among European countries have been reported in the Scandinavian region. The prevalence rate of tularemia in Poland is small, although in recent years stable increase has been observed. According to official epidemiological data during the years 2010-2016 only 61 cases of tularemia were reported in Poland. A laboratory diagnosis of tularemia is based on serological investigation, classical microbiology and molecular biology. The aim of this study was to evaluate the prevalence of infections caused by Francisella tularensis in humans in Poland and present characteristics of laboratory diagnosis of tularemia.

Usefulness of in-house obtained recombinant proteins Yop of Yersinia enterocolitica as highly specific antigens in ELISA and recom-dot performed in the serodiagnosis of yersiniosis.

INTRODUCTION: Proper analysis of the human immune response is crucial in the laboratory diagnosis of many bacterial infections-The current serological diagnosis of yersiniosis often is carried out using ELISA with native antigens. However, recombinant proteins increase the specificity of the serological assays, particularly in patients with chronic, non- specific infections. The aim of the present study was to evaluate the usefulness of in-house obtained recombinant proteins Yop of Yersinia enterocolitica as highly specific antigens in ELISA and recom-dot performed in the serodiagnosis of yersiniosis. MATERIALS AND METHODS: Recombinant YopD, YopB, YopE and V-Ag proteins of Y enterocolitica were expressing in E. coli BL21 (DE3) using the pET-30 Ek/LIC expression vector (Novagen). Purification was accomplished by immobilized metal (Ni2) affinity column chromatography (His-trap). The proteins were used as antigens in standard ELISA and recom-dot assay, which was performed on nitrocellulose strips. The study population, used for characterization of the humoral immune response to the recombinant proteins, consisted of 74 patients suspected for Y enterocolitica infection and 41 clinically healthy blood donors. Some of the results obtained by ELISA and recom-dot were compared with results obtained by commercial western-blot Yersinia (Virotech). RESULTS: In the group of patients suspected for yersiniosis in clinical investigation the most positive results were obtained in ELISA with the recombinant protein YopD (IgA respectively 25 (42.4%), IgG 41 (69.5%), IgM 24 (40.7%). The percentage ofpositive results in the group of blood donors did not exceed 10.0% in IgG and 5.0% in IgA/IgM classes of immunoglobulin. The results obtained in the recom-dot assay showed that among 74 tested serum samples obtained from individuals suspected of yersiniosis the most common IgA, IgG and IgM antibodies were found for recombinant protein YopD (respectively IgG in 60.8%, IgA in 37.8% and IgM in 33.8% of serum samples). IgG antibodies to the protein V-Ag were observed in 32.4%, protein YopB in 27.0% and for the protein YopE in 18.9% serum samples. Immunoglobulin A, and M for the recombinant proteins were found much less frequently than IgG antibodies (respectively 12.2% and 10.8% for V protein-Ag in 10.8% and 14.9% protein and_YopB 2,7% and 10.8% for the protein YopE). Further studies showed that results obtained in recom-dot assay with recombinant protein YopD were comparable with the results of commercial western-blot Yersinia. CONCLUSIONS: The study showed that in-house obtained recombinant proteins can be used as highly specific antigens in ELISA and recom-dot performed in the serodiagnosis of yersiniosis. The most useful was the protein YopD.

[Use of selected recombinant proteins in serodiagnosis of infections caused by verotoxigenic Escherichia coli (VTEC) in humans].

INTRODUCTION: Verocytotoxin-producing E. coli (VTEC) are a significant cause of haemor- rhagic colitis (HC) and haemolytic uremic syndrome (HUS) in humans. Because VTEC isolates are usually present in patients' feces for only a limited period of time serodiagnosis based on the purified antigens have become the useful tool for laboratory diagnosis and monitoring of prevalence of VTEC infections. The aim of the present study was to evaluate the usefulness of in-house obtained recombinant proteins Tir, intymin and verocytotoxin 2b of E. coli as highly specific antigens in ELISA performed in the serodiagnosis of infec- tions caused by VTEC in humans. MATERIALS AND METHODS: The study population, used for characterization of the humoral immune response to the recombinant proteins, consisted of37 patients suspected for VTEC infection, mainly with clinical manifestation of HUS. Additionally serum samples from 78 clinically healthy persons and 96 patients with different bacterial infections (control group) were tested. Recombinant proteins were expressing in E. coli BL21 (DE3) using the pET-30 Ek/LIC expression vector (Novagen). Purification was accomplished by immobilized metal (Ni(2+)) affinity column chromatography (His-trap). RESULTS: The antibodies against recombinant proteins were detected using the ELISA in about half of the tested patients suspected in clinical investigation for VTEC infection. Most of the antibodies belong to the IgG and IgA class of immunoglobulins. Statistical analysis of the results showed that the frequency of detecting antibodies among patients with HUS was significantly higher in relation to the clinically healthy persons. However, the percentage of positive results in the control group were also much higher than in healthy persons what may indicate for presence of non-specific reactions. The least non-specific response was detected by ELISA with the protein Tir as antigen. CONCLUSIONS: The study showed that recombinant proteins Tir, intimin and verocytotoxin 2b of E. coli may be used as antigens in routine diagnosis of VTEC infections. The most specific antigen is a recombinant protein Tir.

Molecular Characterization of Shiga Toxin-Producing Escherichia coli Strains Isolated in Poland.

Shiga toxin-producing Escherichia coli (STEC) strains also called verotoxin-producing E. coli (VTEC) represent one of the most important groups of food-borne pathogens that can cause several human diseases such as hemorrhagic colitis (HC) and hemolytic - uremic syndrome (HUS) worldwide. The ability of STEC strains to cause disease is associated with the presence of wide range of identified and putative virulence factors including those encoding Shiga toxin. In this study, we examined the distribution of various virulence determinants among STEC strains isolated in Poland from different sources. A total of 71 Shiga toxin-producing E. coli strains isolated from human, cattle and food over the years 1996-2010 were characterized by microarray and PCR detection of virulence genes. As stx1a subtype was present in all of the tested Shiga toxin 1 producing E. coli strains, a greater diversity of subtypes was found in the gene stx2, which occurred in five subtypes: stx2a, stx2b, stx2c, stx2d, stx2g. Among STEC O157 strains we observed conserved core set of 14 virulence factors, stable in bacteria genome at long intervals of time. There was one cattle STEC isolate which possessed verotoxin gene as well as sta1 gene encoded heat-stable enterotoxin STIa characteristic for enterotoxigenic E. coli. To the best of our knowledge, this is the first comprehensive analysis of virulence gene profiles identified in STEC strains isolated from human, cattle and food in Poland. The results obtained using microarrays technology confirmed high effectiveness of this method in determining STEC virulotypes which provides data suitable for molecular risk assessment of the potential virulence of this bacteria. virulence factors including those encoding Shiga toxin. In this study, we examined the distribution of various virulence determinants among STEC strains isolated in Poland from different sources. A total of 71 Shiga toxin-producing E. coli strains isolated from human, cattle and food over the years 1996-2010 were characterized by microarray and PCR detection of virulence genes. As stx1a subtype was present in all of the tested Shiga toxin 1 producing E. coli strains, a greater diversity of subtypes was found in the gene stx2, which occurred in five subtypes: stx2a, stx2b, stx2c, stx2d, stx2g. Among STEC O157 strains we observed conserved core set of 14 virulence factors, stable in bacteria genome at long intervals of time. There was one cattle STEC isolate which possessed verotoxin gene as well as sta1 gene encoded heat-stable enterotoxin STIa characteristic for enterotoxigenic E. coli. To the best of our knowledge, this is the first comprehensive analysis of virulence gene profiles identified in STEC strains isolated from human, cattle and food in Poland. The results obtained using microarrays technology confirmed high effectiveness of this method in determining STEC virulotypes which provides data suitable for molecular risk assessment of the potential virulence of this bacteria.

Characterisation of Yersinia Secretion Apparatus--Pathogenicity Island (Ysa-PI) of Yersinia enterocolitica 1B/O8 in Poland: an Idle Ysa is a Specific Hallmark of the Epidemic Sensu Stricto Strain.

Yersinia secretion apparatus (Ysa), the chromosomal type three secretion system (T3SS) is considered to contribute to virulence of high-pathogenicity Yersina enterocolitica biovar 1B. DNA-sequence of Ysa pathogenicity island was determined for clinical isolate DM0110 of Y enterocolitica 1B/08 with origin in Poland. We found a premature stop-codon in the regulatory gene ysrR (mutation at position 269). Altered ysrR was detected in all tested 78 isolates of Y enterocolitica 1B/O8 collected from clinical samples in Poland from 2004 to 2013. Since aberrations in YsrR are considered to inactivate Ysa, our findings may suggest Ysa is not indispensable for Y enterocolitica 1B/O8 to infect humans.

Increasing role of arthropod bites in tularaemia transmission in Poland - case reports and diagnostic methods.

The study describes four cases of tularaemia - one developed after contact with rabbits and three developed after an arthropod bite. Due to non-specific clinical symptoms, accurate diagnosis of tularaemia may be difficult. The increasing contribution of the arthropod vectors in the transmission of the disease indicates that special effort should be made to apply sensitive and specific diagnostic methods for tularaemia, and to remind health-care workers about this route of Francisella tularensis infections. The advantages and disadvantages of various diagnostic methods - molecular, serological and microbiological culture - are discussed. The PCR as a rapid and proper diagnostic method for ulceroglandular tularaemia is presented.