The objectives of this study were to assess the current incidence of invasive pneumococcal disease (IPD) in Poland (2011-2013), where mass vaccination has not been implemented, and to characterize the Streptococcus pneumoniae isolates responsible for invasive infections by determining their serotype distribution and antimicrobial resistance patterns. For all isolates identification, serotyping and antimicrobial minimal inhibitory concentrations determination were performed based on routine techniques. The highest incidence rates were observed among adults older than 85 years old (4.62/100,000) and children under 1 year of age (4.28/100,000). The general case fatality ratio (CFR) was 25.4%, with the highest CFR in the age group ≥85 years old (59.7%). The most common serotypes were 3, 14, 19A, 4, 9V, 19F, 1, and 23 F (61.3% of all isolates). The 10- and 13-valent pneumococcal conjugated vaccines (PCV) covered 46.0 and 71.8% of all IPD cases, 61.4 and 79.5% of cases in children under two years, and 60.4 and 78.6% of cases involving children under five years of age, respectively. The PCV13 and 23-valent polysaccharide vaccine covered 68.7 and 86.0% of cases in adults >65 years old, respectively. Decreased susceptibility was noted for penicillin (24.8%), cefotaxime (10.0%), meropenem (5.0%), rifampicin (0.8%), chloramphenicol (4.3%), erythromycin (29.7%) and clindamycin (25.6%). Multi-drug resistance characterized 21.6% of the pneumococci tested. Despite deficiencies in the Polish surveillance system and strong underestimation of IPD cases, results of the study showed good theoretical coverage of PCV, which should encourage inclusion of anti-pneumococcal conjugate vaccine into the national immunization program.

BackgroundThe food-borne pathogen Listeria monocytogenes is the causative agent of listeriosis. The β-lactam antibiotics penicillin G and ampicillin are the current drugs of choice for the treatment of listerial infections. While isolates of L. monocytogenes are susceptible to these antibiotics, their action is only bacteriostatic and consequently, this bacterium is regarded as tolerant to β-lactams. In addition, L. monocytogenes has a high level of innate resistance to the cephalosporin family of β-lactams frequently used to treat sepsis of unknown etiology. Given the high mortality rate of listeriosis despite rational antibiotic therapy, it is important to identify genes that play a role in the susceptibility and tolerance of L. monocytogenes to β-lactams.ResultsThe hly-based promoter trap system was applied to identify penicillin G-inducible genes of L. monocytogenes. The results of reporter system studies, verified by transcriptional analysis, identified ten penicillin G-inducible genes. The contribution of three of these genes, encoding a ferritin-like protein (fri), a two-component phosphate-response regulator (phoP) and an AraC/XylS family transcriptional regulator (axyR), to the susceptibility and tolerance of L. monocytogenes to β-lactams was examined by analysis of nonpolar deletion mutants. The absence of PhoP or AxyR resulted in more rapid growth of the strains in the presence of sublethal concentration of β-lactams, but had no effect on the MIC values or the ability to survive a lethal dose of these antibiotics. However, the Δfri strain showed impaired growth in the presence of sublethal concentrations of penicillin G and ampicillin and a significantly reduced ability to survive lethal concentrations of these β-lactams. A lack of Fri also caused a 2-fold increase in the sensitivity of L. monocytogenes to cefalotin and cephradine.ConclusionsThe present study has identified Fri as an important mediator of β-lactam tolerance and innate resistance to cephalosporins in L. monocytogenes. PhoP and AxyR are probably involved in transmitting signals to adjust the rate of growth of L. monocytogenes under β-lactam pressure, but these regulators do not play a significant role in susceptibility and tolerance to this class of antibiotics.

Background Neisseria meningitidis is a leading etiologic agent of severe invasive disease. The objective of the study was to characterise invasive meningococcal disease (IMD) epidemiology in Poland during the last decade, based on laboratory confirmed cases.MethodsThe study encompassed all invasive meningococci collected between 2002 and 2011 in the National Reference Centre for Bacterial Meningitis. The isolates were re-identified and characterised by susceptibility testing, MLST analysis, porA and fetA sequencing. A PCR technique was used for meningococcal identification directly from clinical materials.ResultsIn the period studied, 1936 cases of IMD were confirmed, including 75.6% identified by culture. Seven IMD outbreaks, affecting mostly adolescents, were reported; all were caused by serogroup C meningococci of ST-11. The highest incidence was observed among children under one year of age (15.71/100,000 in 2011). The general case fatality rate in the years 2010–2011 was 10.0%. Meningococci of serogroup B, C, Y and W-135 were responsible for 48.8%, 36.6%, 1.2% and 1.2% of cases, respectively. All isolates were susceptible to third generation cephalosporins, chloramphenicol, ciprofloxacin, and 84.2% were susceptible to penicillin. MLST analysis (2009–2011) revealed that among serogroup B isolates the most represented were clonal complexes (CC) ST-32CC, ST-18CC, ST-41/44CC, ST-213CC and ST-269CC, and among serogroup C: ST-103CC, ST-41/44CC and ST-11CC.ConclusionsThe detection of IMD in Poland has changed over time, but observed increase in the incidence of the disease was mostly attributed to changes in the surveillance system including an expanded case definition and inclusion of data from non-culture diagnostics.

The expression of ten genes of Listeria monocytogenes previously identified as penicillin G-inducible was transcriptionally analyzed in the presence of 0.5 M KCl, pH 5.0 and 42 °C. This study revealed that all the genes are upregulated by osmotic stress, seven by acid stress and four by temperature stress conditions. The contribution of a gene encoding a ferritin-like protein (fri), a two-component phosphate-response regulator (phoP) and an AraC/XylS family transcription regulator (axyR) to temperature, acid and osmotic stress tolerance was further examined by analysis of nonpolar deletion mutants. This revealed that a lack of PhoP or AxyR does not affect the ability to grow under the tested stress conditions. However, the Δfri strain showed slightly delayed growth under osmotic and clearly impaired growth under acid stress conditions, indicating an important role of the ferritin-like protein in acid stress tolerance.

No abstract