Determination of penicillin resistance in Streptococcus pneumoniae isolates from southern Brazil by PCR

Theoretical pneumococcal vaccine coverage: analysis of serotypes isolated from inpatients at a tertiary care hospital

Objective:

To evaluate Streptococcus pneumoniae serotypes isolated from an inpatient population at a tertiary care hospital, in order to determine the theoretical coverage of the 13-valent pneumococcal conjugate vaccine (PCV13) and the 23-valent pneumococcal polysaccharide vaccine (PPV23).

Methods:

This was a cross-sectional study involving 118 inpatients at the Hospital São Lucas, in the city of Porto Alegre, Brazil, whose cultures of blood, cerebrospinal fluid, or other sterile body fluid specimens, collected between January 2005 and December 2016, yielded pneumococcal isolates. The theoretical vaccine coverage was studied in relation to the serotypes identified in the sample and their relationship with those contained in the pneumococcal vaccines available in Brazil.

Results:

The majority of the population was male (n = 66; 55.9%), with a median age of 57 years (interquartile range: 33-72 years). The most common manifestation was pneumonia, and the pneumococcus was most commonly isolated from blood cultures. More than one fourth of the study population had some degree of immunosuppression (n = 34; 28.8%). Of the total sample, 39 patients (33.1%) died. There were no significant associations between mortality and comorbidity type, ICU admission, or need for mechanical ventilation. The theoretical vaccine coverage of PPV23 alone and PCV13 plus PPV23 was 31.4% and 50.8%, respectively.

Conclusions:

If the patients in this sample had been previously vaccinated with PCV13 plus PPV23, theoretically, 50.8% of the cases of invasive pneumococcal disease that required hospital admission could potentially have been prevented. Invasive pneumococcal disease should be prevented by vaccination not only of children and the elderly but also of adults in their economically productive years, so as to reduce the socioeconomic costs, morbidity, and mortality still associated with the disease, especially in underdeveloped countries.

Biological and Epidemiological Features of Antibiotic-Resistant Streptococcus pneumoniae in Pre- and Post-Conjugate Vaccine Eras: a United States Perspective

Streptococcus pneumoniae inflicts a huge disease burden as the leading cause of community-acquired pneumonia and meningitis. Soon after mainstream antibiotic usage, multiresistant pneumococcal clones emerged and disseminated worldwide. Resistant clones are generated through adaptation to antibiotic pressures imposed while naturally residing within the human upper respiratory tract. Here, a huge array of related commensal streptococcal strains transfers core genomic and accessory resistance determinants to the highly transformable pneumococcus. β-Lactam resistance is the hallmark of pneumococcal adaptability, requiring multiple independent recombination events that are traceable to nonpneumococcal origins and stably perpetuated in multiresistant clonal complexes. Pneumococcal strains with elevated MICs of β-lactams are most often resistant to additional antibiotics. Basic underlying mechanisms of most pneumococcal resistances have been identified, although new insights that increase our understanding are continually provided. Although all pneumococcal infections can be successfully treated with antibiotics, the available choices are limited for some strains. Invasive pneumococcal disease data compiled during 1998 to 2013 through the population-based Active Bacterial Core surveillance program (U.S. population base of 30,600,000) demonstrate that targeting prevalent capsular serotypes with conjugate vaccines (7-valent and 13-valent vaccines implemented in 2000 and 2010, respectively) is extremely effective in reducing resistant infections. Nonetheless, resistant non-vaccine-serotype clones continue to emerge and expand.

Evidence of involvement of the mannose receptor in the internalization of Streptococcus pneumoniae by Schwann cells

BACKGROUND

The ability of S. pneumoniae to generate infections depends on the restrictions imposed by the host's immunity, in order to prevent the bacterium from spreading from the nasopharynx to other tissues, such as the brain. Some authors claim that strains of S. pneumoniae, which fail to survive in the bloodstream, can enter the brain directly from the nasal cavity by axonal transport through the olfactory and/or trigeminal nerves. However, from the immunological point of view, glial cells are far more responsive to bacterial infections than are neurons. This hypothesis is consistent with several recent reports showing that bacteria can infect glial cells from the olfactory bulb and trigeminal ganglia. Since our group previously demonstrated that Schwann cells (SCs) express a functional and appropriately regulated mannose receptor (MR), we decided to test whether SCs are involved in the internalization of S. pneumoniae via MR.

RESULTS

Immediately after the interaction step, as well as 3 h later, the percentage of association was approximately 56.5%, decreasing to 47.2% and 40.8% after 12 and 24 h, respectively. Competition assays by adding a 100-fold excess of mannan prior to the S. pneumoniae infection reduced the number of infected cells at 3 and 24 h. A cytochemistry assay with Man/BSA-FITC binding was performed in order to verify a possible overlap between mannosylated ligands and internalized bacteria. Incubation of the SCs with Man/BSA-FITC resulted in a large number of intracellular S. pneumoniae, with nearly complete loss of the capsule. Moreover, the anti-pneumococcal antiserum staining colocalized with the internalized man/BSA-FITC, suggesting that both markers are present within the same endocytic compartment of the SC.

CONCLUSIONS

Our data offer novel evidence that SCs could be essential for pneumococcal cells to escape phagocytosis and killing by innate immune cells. On the other hand, the results also support the idea that SCs are immunocompetent cells of the PNS that can mediate an efficient immune response against pathogens via MR.

Olfactory ensheathing cells as putative host cells for Streptococcus pneumoniae: evidence of bacterial invasion via mannose receptor-mediated endocytosis

Olfactory ensheathing cells (OECs) are a special glia that ensheath olfactory receptor axons that enter the brain via olfactory phila, thus, providing a potential route for access of pathogens. Streptococcus pneumoniae (Sp), that has a capsule rich in mannosyl residues, is the most common cause of rhinosinusitis that may evolve to meningitis. We have tested whether OECs in vitro express the mannose receptor (MR), and could internalize Sp via MR. Cultures were infected by a suspension of Sp (ATCC 49619), recognized by an anti-Sp antibody, in a 100:1 bacteria:cells ratio. Competition assays, by means of mannan, showed around a 15-fold reduction in the number of internalized bacteria. To verify whether MR could be involved in Sp uptake, OECs were reacted with an antibody against the MR C-terminal peptide (anti-cMR) and bacteria were visualized with Sytox Green. Selective cMR-immunoreaction was seen in perinuclear compartments containing bacteria whereas mannan-treated cultures showed an extremely low percentage of internalized bacteria and only occasional adhered bacteria. Our data suggest the involvement of MR in adhesion of bacteria to OEC surface, and in their internalization. Data are also coherent with a role of OECs as a host cell prior to (and during) bacterial invasion of the brain.

Antimicrobial susceptibility of Streptococcus pneumoniae and genotypic characterization of erythromycin-resistant strains in porto alegre, Brazil

The antimicrobial susceptibility of 64 strains of S. pneumoniae obtained from three hospitals in Porto Alegre, Brazil, isolated between 2004 and 2005. was determined, using the agar-dilution method. The prevalence of resistant (intermediate and full resistance) strains to trimethoprim/sulphamethoxazole, penicillin, tetracycline, erythromycin, chloramphenicol, and ceftriaxone were 68%, 28%, 18%, 15%, 3%, and 1%, respectively. All strains were susceptible to vancomycin. Among 18 penicillin-resistant strains, 7 were resistant to at least two other antimicrobial drugs. All erythromycin-resistant strains, except one, contained the erm(B) and/or mef(A/E) genes, with a predominance of the former. The resistance rate to penicillin and erythromycin in Porto Alegre remained stable. The combination of trimethoprim/ sulphamethoxazole should not be recommended to treat pneumococcal infections, because of the high rate of resistant strains.