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BACKGROUND: Vaccination is one of the most effective life-saving medical interventions, and the introduction of SARS-CoV-2 vaccines was intended to prevent the serious implications of COVID-19. The objectives of the study were (i) to observe the humoral immune response to the BNT162b2 vaccine and SARS-CoV-2 infection (mainly breakthrough infections), (ii) to demonstrate the persistence of anti-SARS-CoV-2 antibodies over time in relation to the number of received vaccine doses and the course of infection, and (iii) to determine the adverse effects after primary vaccine doses. METHODS: To assess the humoral response, IgG and IgA anti-S1 antibodies were quantified by ELISA assays. In total, the tests were carried out seven times in almost two years. RESULTS: We demonstrated strong immunogenicity (compared to levels before primary vaccination, 150- and 20-fold increases in IgG and IgA, respectively) of the BNT162b2 vaccine. Over time, we observed a systematic decline in antibody levels, which may have contributed to breakthrough infections. Although they caused seroconversion similar to the booster, antibody levels in such patients fell more rapidly than after re-vaccination. On the other hand, in individuals who did not receive booster(s) and who did not present breakthrough infection, anti-SARS-CoV-2 antibodies returned to pre-vaccination levels after 20 months. The most commonly recognized adverse effects were injection site redness and swelling. CONCLUSION: Vaccination is highly effective in preventing the most severe outcomes of COVID-19 and should be performed regardless of prior infection. Booster doses significantly enhance anti-SARS-CoV-2 antibody levels and, in contrast to those obtained by breakthrough infection, they remain longer.

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INTRODUCTION: The genus Streptococcus comprises a number of species characterized by a differential pathogenic potential. These bacteria can be considered as members of microbial physiological flora but they can also cause mild infections or severe, life threatening conditions. The majority of infections of streptococcal etiology are caused by beta-hemolysing species. The predominant causative agent of bacterial pharyngitis is Streptococcus pyogenes. This species usually doesn't give rise to any identification difficulties due to the introduction the well determined diagnostic schemes. Problems concerning laboratory identification can be, however, associated with other species of beta-hemolysing streptococci isolated from patients with pharyngitis. These streptococci can demonstrate features similar to those of S. pyogenes and share the group antygen A, such as some strains of Streptococcus anginosus and Streptococcus dysgalactiae subsp. equisimilis. The determination of sensitivity to bacitracin, which is a feature typical of S. pyogenes, is the basic test useful for its preliminary identification. Nevertheless, the identification of some strains by this test can give rise to incompatibility. The aim of the study was characterisation of beta-hemolysing streptococci resistant to bacitracin isolated from patients with pharyngitis. The examined bacterial strains caused identification problems by the use of routine diagnostic methods. METHODS: The material included 14 streptococcal strains resistant to bacitracin which were isolated from adult patients suffering from pharyngitis. The bacteria were cultured on media dedicated for the species. The following routine diagnostic tests were used for the bacterial identification: sensitivity to bacitracin (0.04 U/disc), CAMP test, determination of the group antigens A, B, C, D, F and G (Slidex Strepto-Kit), and determination of biochemical features by the API 20 STREP test (bioMèrieux). The sensitivity of streptococcal isolates to antibiotics (penicillin, clindamycin, erythromycin, tetracycline, vancomycin, ofloxacin) and trimethoprim/sulfamethoxazole, was determined by the disc diffusion method on the Mueller-Hinton agar with 5% sheep blood (the inoculum-0.5 McFarland). RESULTS: Among the 14 isolates resistant to bacitracin, 6 isolates of S. pyogenes, 6 isolates of S. constellatus, and 2 isolates of S. dysgalactiae subsp. equisimilis were identified. All isolates were sensitive to penicillin and vancomycin. One isolate ofS. pyogenes demonstrated constitutive MLSB resistance mechanism. Seven isolates were resistant to tetracycline: S. dysgalactiae subsp. equisimilis (3 isolates), S. constellatus (3), and S. pyogenes (1). The number of isolates resistant to trimethoprim/sulfamethoxazole was as follows: S. pyogenes (6) and S. dysgalactiae subsp. equisimilis (1), whereas four isolates were resistant to ofloxacin. CONCLUSIONS: The bacitracin test cannot be used as the only test for the laboratory identification of S. pyogenes even if it is combined with the determination of the Lancefield group antigen due to the existence of bacitracin resistant S. pyogenes strains. Therefore, it is necessary to perform biochemical commercial tests in addition to routine phenotypic tests. Isolation of beta-hemolysing streptococci other than S. pyogenes from patients with pharyngitis confirms their role in the etiology of this infection. Taken into account the significance of determination of sensitivity to bacitracin for the preliminary identification of S. pyogenes, it is necessary to standardize this test, which will make obtaining of the comparability of results possible.

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In this study, clonal relatedness of 202 Staphylococcus aureus (mostly methicillin-resistant) isolates recovered in 29 Polish hospitals was investigated by multiple-locus variable number tandem repeat fingerprinting (MLVF) and spa typing. Our analysis yielded 69 MLVF patterns and 34 spa types. Almost all isolates (97.4%) identical by MLVF were also indistinguishable by spa typing. Therefore, the MLVF method can be a cheap and fast screen before spa typing. Moreover, results obtained by MLVF suggest a set of simple criteria for grouping of spa types. The proposed algorithm groups isolates into the same cluster when spa sequences differ by a single mutation event: i) a single deletion or insertion of repeat unit(s) at the X region of the protein A gene or ii) a single nucleotide polymorphism within a repeat sequence. The combined use of these 2 methods, MLVF in local laboratories and spa typing of selected isolates in reference centers, can improve the monitoring of hospital-to-hospital strain transmission events and public health interventions on a huge scale.

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Despite the growing number of scientific reports showing different markers of infection caused by Chlamydia pneumoniae in patients with advanced atherosclerosis, there is still no clear confirmation of a pathogenetic link between this infection and atherogenesis. The aim of the present study was to investigate the presence C. pneumoniae DNA in peripheral blood mononuclear cells and carotid endarterectomy samples obtained from patients with advanced atherosclerosis according to the presence specific antibodies against C. pneumoniae in serum. The levels of IgG, IgM and IgA antibodies to C. pneumoniae were determined by enzyme immunoassay (EIA) in sera of 36 patients with advanced atherosclerosis undergoing carotid endarterectomy. The presence of C. pneumoniae DNA in the carotid samples and in peripheral blood mononuclear cells was investigated by a nested polymerase chain reaction (PCR). We have not confirm the presence of C. pneumoniae DNA either in the carotid endarterectomy samples or in peripheral blood mononuclear cells, both in patients having the specific antibodies against C. pneumoniae and in seronegative patients. In the studied group of patients with advanced carotid atherosclerosis there was no correlation between the presence of specific antibodies against C. pneumoniae and the presence of C. pneumoniae DNA in endarterectomy samples and peripheral blood mononuclear cells.

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