Antibiotic susceptibility according to genotype of penicillin-binding protein and macrolide resistance genes, and serotype of Streptococcus pneumoniae isolates from community-acquired pneumonia in children

Burden of illness associated with pneumococcal infections in Japan - a targeted literature review

INTRODUCTION

Pneumococcal diseases (PDs) are among the leading causes of mortality and morbidity worldwide. However, the evidence on epidemiology, health economic, and patient-reported outcomes has not been systematically reviewed and published in Japan. This study aimed to assess the burden, treatment adherence and compliance, and serotype distribution associated with PDs in Japan.

METHOD

One hundred and eight studies were identified between January 2005 and June 2020. The identified studies were mostly regional and with a limited scale, clinical settings, and populations.

RESULTS

In 2013-2017, invasive PD incidence rates were 4.98-9.47/100,000 in <4-year-olds, 0.36/100,000 in 5-14-year-olds, 0.46/100,000 in 15-64-year-olds, and 1.50-5.38/100,000 in the elderly. The incidence of invasive PDs in children decreased from 24.6/100,000 in 2008 to 10.7/100,000 in 2013 after the introduction of PCV7 and further declined to 10.3/100,000 in 2014 after PCV13 was introduced. From 2014, the prevalence of PCV13 serotypes decreased across all age groups along with a decrease of PPV23 serotypes, but an increase of PPV23 serotypes not included in PCV13 among adults and the elderly. No study reported health-related quality-of-life data for PDs. In children, direct costs were 340,905-405,978 JPY (3,099-3,691 USD) per pneumococcal bacteraemia, 767,447-848,255 JPY (6,977-7,711 USD) per pneumococcal meningitis, and 79,000 JPY (718 USD) per pneumococcal acute otitis media episodes. In adults and the elderly, the direct cost of pneumococcal pneumonia was 348,280-389,630 JPY (3,166-3,542 USD). The average hospital stay length was 7.2-31.9 days in children, 9.0 days in adults and 9.0-28.7 days in adults and the elderly.

CONCLUSIONS

The epidemiological burden of PDs remains high in Japan, especially among children and the elderly with invasive PDs accounting for a very small proportion of all PDs. A significant impact of the PCV13 vaccine program was reported, while the PPV23's impact remains unclear. A substantial decrease in quality-adjusted life years in adults and the elderly and a high economic burden may exist.

Assessment of the local clonal spread of Streptococcus pneumoniae serotype 12F caused invasive pneumococcal diseases among children and adults

BACKGROUND

We conducted active surveillance to elucidate the distribution of Streptococcus pneumoniae serotypes causing invasive pneumococcal disease (IPD) and clarified the genetic relatedness among the isolates in Kobe City, Japan.

METHODS

Forty-five IPD-causing S. pneumoniae strains were analyzed from March 2016 to May 2018 through active surveillance in Kobe City, Hyogo, Japan. Serotypes were determined by multiplex serotyping PCR and the Quellung reaction with pneumococcal antisera. Fourteen Sp12F strains were subjected to whole-genome sequencing (WGS).

RESULTS

Among 45 isolates, the most frequent serotypes were 12F (n=14, 31%), 24F (n=5, 11%), and 10A (n=4, 9%). Multilocus sequence typing (MLST) analysis of 14 isolates of Sp12F divided them into ST4846 (n=4) and ST6495 (n=10). WGS showed clonality of the 10 isolates of ST6495, with only 13 single nucleotide polymorphisms in the genomes. Meanwhile, ST4846 strains in Kobe differed from only the outbreak strains of Sp12F ST4846 in Tsuruoka, Japan, reported on 2018.

CONCLUSIONS

Serotype monitoring showed Sp12F to be the predominant serotype in Kobe, and WGS revealed the clonal spread of Sp12F ST6495 in this city. Thus, the spread of Sp12F could become a serious public health problem in Japan, warranting thorough monitoring in future.

Ten-Year Trends and Clinical Relevance of the Antimicrobial Resistance Genotype in Respiratory Isolates of Streptococcus pneumoniae

Background: Antimicrobial resistance of Streptococcus pneumoniae, especially against β-lactam antibiotics, is a global concern. We aimed to analyze a 10-year trend in the antimicrobial resistance genotype of respiratory isolates of S. pneumoniae and to clarify whether resistance genotypes were correlated with phenotypic drug susceptibility, pathogenicity, and host clinical background. Methods: Respiratory isolates of S. pneumoniae from 2003 to 2012 were analyzed with polymerase chain reaction for the presence of β-lactam resistance gene mutations on pbp1a, pbp2x, and pbp2b. Sixty-eight strains isolated from different patients in 2012 were particularly analyzed for the association between genotypes and clinical data. Results: The 10-year trend analysis showed a recent increase in gPRSP (genotypic penicillin-resistant S. pneumoniae) with all 3 β-lactam resistance genes (from 21.7 to 35.3% in 3 years) and a steady level of gPSSP (genotypic penicillin-susceptible S. pneumoniae) without any β-lactam resistance genes (13.2% in 2012). This resistance trend in genotypes was more prominent than resistance phenotypes determined with a drug susceptibility test. The probability of being a causative pathogen did not differ in gPSSP (55.6%), gPISP (genotypic penicillin-intermediate resistant S. pneumoniae; 54.3%), and gPRSP (54.2%). There was no significant difference in the ratio of patients who presented with respiratory failure in respiratory infection caused by gPSSP, gPISP, or gPRSP. Host clinical characteristics including age and gender were not different among resistance genotypes. Conclusions: There was no difference in pathogenicity or clinical background between gPSSP, gPISP, and gPRSP. Antimicrobial resistance in respiratory isolates of S. pneumoniae was more prevalent in genotypes than in phenotypes.

Emergence of quinolone-resistant strains in Streptococcus pneumoniae isolated from paediatric patients since the approval of oral fluoroquinolones in Japan

Tosufloxacin (TFLX) is a fluoroquinolone antimicrobial agent. TFLX granules for children were initially released in Japan in 2010 to treat otitis media and pneumonia caused by drug-resistant bacteria, e.g. penicillin-resistant Streptococcus pneumoniae and beta-lactamase-negative, ampicillin-resistant Haemophilus influenzae. The evolution of bacterial resistance since TFLX approval is not known. To clarify the influence of quinolones administered to children since their approval, we examined the resistance mechanism of TFLX-resistant S. pneumoniae isolated from paediatric patients as well as patient clinical characteristics. TFLX-resistant strains (MIC ≥ 2 mg/L) were detected among clinical isolates of S. pneumoniae derived from children (≤15 years old) between 2010 and 2014. These strains were characterised based on quinolone resistance-determining regions (QRDRs), i.e. gyrA, gyrB, parC, and parE. In addition, the antimicrobial susceptibility, serotype, and multilocus sequence type of strains were determined, pulsed-field gel electrophoresis was performed, and patient clinical characteristics based on medical records were assessed for cases with underling TFLX-resistant strains. Among 1168 S. pneumoniae isolates, two TFLX-resistant strains were detected from respiratory specimens obtained from paediatric patients with frequent exposure to TFLX. Both strains had mutations in the QRDRs of gyrA and parC. One case exhibited gradual changes in the QRDR during the clinical course. This is the first study of quinolone-resistant S. pneumoniae isolated from children, including clinical data, in Japan. These data may help prevent increases in infections of quinolone-resistant S. pneumoniae in children; specifically, the results emphasise the importance of administering fluoroquinolones only in appropriate cases.

Theory and strategy for Pneumococcal vaccines in the elderly

Pneumonia is the fourth-leading cause of death globally, and Streptococcus pneumoniae is the most important causative pathogen. Because the incidence of pneumococcal diseases is likely to increase with the aging society, we should determine an optimal strategy for pneumococcal vaccination. While consensus indicates that 23-valent pneumococcal polysaccharide vaccine prevents invasive pneumococcal diseases (IPD), its effects on community-acquired pneumonia (CAP) remain controversial. Recently, a 13-valent pneumococcal conjugate vaccine (PCV13) was released. The latest clinical study (CAPiTA study) showed that PCV13 reduced vaccine-type CAP and IPD. Based on these results, the Advisory Committee on Immunization Practices recommended initial vaccination with PCV13 for the elderly. Scientific evidence regarding immunosenescence is needed to determine a more ideal vaccination strategy for the elderly with impaired innate and adaptive immunity. Continuing research on the cost effectiveness of new vaccine strategies considering constantly changing epidemiology is also warranted.

Streptococcus pneumoniae Serotype Distribution and Pneumococcal Conjugate Vaccine Serotype Coverage among Pediatric Patients in East and Southeast Asia, 2000-2014: a Pooled Data Analysis

Pneumococcal infection is one of the leading causes of death worldwide, especially in children of developing and underdeveloped countries. Capsular polysaccharide-based vaccines are available for the prevention of this disease. A 7-valent pneumococcal conjugate vaccine (PCV7) was licensed in 2000 for use in children less than two years of age. Subsequently, to broaden the protection, 10-valent (PCV10) and 13-valent (PCV13) vaccines were licensed in 2009 and 2010, respectively. All of these conjugate vaccines elicit an immune response that only provides protection against the infection of S. pneumoniae serotypes included in the formulation. Profiles of S. pneumoniae serotype distribution and serotype coverage for both PCV7 and PCV13 have been reported in some Asian countries/territories. But the published results cannot provide conclusive information due to the difference in studied population and geographic areas. The goals of this review are to obtain an accurate estimate of serotype coverage for PCV7, PCV10, and PCV13 and examine the change in the S. pneumoniae serotype distribution after PCV7 use among pediatric patients in East and Southeast Asia through the analysis of pooled data that were published in the English literature between 2000 and 2014.

Immunogenicity and safety of the 10-valent pneumococcal nontypeable Haemophilus influenzae protein D conjugate vaccine (PHiD-CV) co-administered with DTPa vaccine in Japanese children: A randomized, controlled study

This phase III, randomized, open-label, multicenter study (NCT01027845) conducted in Japan assessed the immunogenicity, safety, and reactogenicity of 10-valent pneumococcal nontypeable Haemophilus influenzae protein D conjugate vaccine (PHiD-CV, given intramuscularly) co-administered with diphtheria-tetanus-acellular pertussis vaccine (DTPa, given subcutaneously). Infants (N=360 ) were randomized (2:1) to receive either PHiD-CV and DTPa (PHiD-CV group) or DTPa alone (control group) as 3-dose primary vaccination (3–4–5 months of age) and booster vaccination (17–19 months of age). Immune responses were measured before and one month after primary/booster vaccination and adverse events (AEs) were recorded. Post-primary immune responses were non-inferior to those in pivotal/efficacy European or Latin American pneumococcal protein D-conjugate vaccine studies. For each PHiD-CV serotype, at least 92.6% of infants post-primary vaccination and at least 97.7% of children post-booster had pneumococcal antibody concentrations ≥0.2 μg/ml, and at least 95.4% post-primary and at least 98.1% post-booster had opsonophagocytic activity (OPA) titers ≥8 . Geometric mean antibody concentrations and OPA titers (except OPA titer for 6B) were higher post-booster than post-priming for each serotype. All PHiD-CV-vaccinated children had anti-protein D antibody concentrations ≥100 EL.U/ml one month post-primary/booster vaccination and all were seroprotected/seropositive against each DTPa antigen. Redness and irritability were the most common solicited AEs in both groups. Incidences of unsolicited AEs were comparable between groups. Serious AEs were reported for 47 children (28 in PHiD-CV group); none were assessed as vaccine-related. In conclusion, PHiD-CV induced robust immune responses and was well tolerated when co-administered with DTPa in a 3-dose priming plus booster regimen to Japanese children.

Changes in capsule and drug resistance of Pneumococci after introduction of PCV7, Japan, 2010-2013

We aimed to clarify changes in serotypes and genotypes mediating β-lactam and macrolide resistance in Streptococcus pneumoniae isolates from Japanese children who had invasive pneumococcal disease (IPD) after the 7-valent pneumococcal conjugate vaccine (PCV7) was introduced into Japan; 341 participating general hospitals conducted IPD surveillance during April 2010-March 2013. A total of 300 pneumococcal isolates were collected in 2010, 146 in 2011, and 156 in 2012. The proportion of vaccine serotypes in infectious isolates decreased from 73.3% to 54.8% to 14.7% during the 3 years. Among vaccine serotype strains, genotypic penicillin-resistant S. pneumoniae strains also declined each year. Among nonvaccine serotype strains, 19A, 15A, 15B, 15C, and 24 increased in 2012. Increases were noted especially in genotypic penicillin-resistant S. pneumoniae isolates of serotypes 15A and 35B, as well as macrolide resistance mediated by the erm(B) gene in 15A, 15B, 15C, and 24.

[Genetic analysis of multidrug-resistant Streptococcus pneumoniae including meropenem resistance that was isolated from elderly residents with pneumonia in nursing-care facilities]

From February to December 20XX, penicillin-resistant Streptococcus pneumoniae (PRSP) showing MICs of 16-32 microg/mL to cefotaxime (CTX) and 4-8 microg/mL to meropenem (MEPM) were isolated from 6 patients hospitalized at the general hospital S (2 cases) and hospital A (4 cases), close to the hospital S. Five elderly patients among these six cases came from nursing care facilities or nursing care-related medical facilities. All elderly persons (mean age: 81.7 years) were diagnosed as having pneumonia at the time of admission and the problematic PRSP was isolated from sputum samples collected on admission. Notably, all of these PRSP isolates simultaneously showed high resistance to macrolide agents mediated by an erm (B) gene and to fluoroquinolone agents via mutations in the gyrA and parC genes. Eventually, they were identified as multidrug-resistant S. pneumoniae (MDRSP) with high resistance to many agents. The capsule type of all strains was serotype 19F and multilocus sequence typing (MLST) revealed that they belonged to clonal complex (CC) 7993, which has not been reported before. It was thus concluded that the MDRSP that had spread within the nursing facilities was transmitted to the general hospitals via the elderly inpatients with pneumonia caused by these agents. Although one case finally had a poor outcome, the pneumococcal infection was not the direct trigger of the event. The current ratio of MDRSP is concluded to be very low. However, general hospitals that accept patients for therapeutic purposes from nursing-care facilities have to share epidemiological information in a timely manner with the nursing homes to prevent nosocomial infections.

Serotype distribution and susceptibility to penicillin and erythromycin among noninvasive or colonization isolates of Streptococcus pneumoniae in northern Japan: a cross-sectional study in the pre-PCV7 routine immunization period

Distribution of serotypes, prevalence of resistance to penicillin and/or erythromycin (EM), and its genetic traits were analyzed for a total of 1,061 noninvasive or colonization isolates of Streptococcus pneumoniae (998 and 61 isolates from children and adults, respectively) in Hokkaido, northern main island of Japan, in the year 2011, the pre-PCV7 routine immunization period. Serotype deduction was performed by sequential multiplex polymerase chain reaction (PCR), employing mutagenic PCR-restriction fragment length polymorphism for discrimination of 6A/C and 6B/D. Unaltered three PBP genes and macrolide resistance genes erm(B) and mef(A/E) were detected by multiplex PCR. Among isolates from children, 25 serotypes, including the prevalent types 6B (17.5%), 19F (15.6%), 23F (12.2%), and 6C (11.6%), were identified, revealing the PCV7 and PCV13 coverage rates as 48.2% and 60.3%, respectively, while serotype 3 was the most frequent (19.0%) among isolates from adults. Most of the pediatric isolates (96.8%) exhibited resistance to EM (minimum inhibitory concentration [MIC], ≥1 μg/ml), with a higher prevalence of erm(B) (67.2%) than mef(A/E) (39.7%). erm(B) was associated with high-level EM resistance (MIC, ≥128 μg/ml) and distributed at high detection rates to major serotypes 23F (85.2%) and 6B (85.1%), as well as minor serotypes 3, 10A, 14, 15B, 15C, 19A, and 23A (>90%). While penicillin-resistant S. pneumoniae (PRSP) (penicillin G-MIC, 2-3 μg/ml) was detected in 7.8% of isolates from children, the most common PBP gene genotype was gPRSP (three altered genes pbp1a, 2x, and 2b; 38.3%), which was detected at higher rates (>60%) in the dominant serotypes 23F, 6B, and 19F, and minor serotypes 6D and 15A. Dominant serotypes in the S. pneumoniae isolates were generally similar to those reported for invasive strains, despite lower coverage rates by PCV7/13. The importance of further surveillance on incidence and drug resistance in the post-PCV7 period was suggested for non-PCV7/13 serotypes 6C, 6D, 10A, 15A, 15B, 15C, 23A, and 35B.

Amycolamicin: a novel broad-spectrum antibiotic inhibiting bacterial topoisomerase

The abuse of antibacterial drugs imposes a selection pressure on bacteria that has driven the evolution of multidrug resistance in many pathogens. Our efforts to discover novel classes of antibiotics to combat these pathogens resulted in the discovery of amycolamicin (AMM). The absolute structure of AMM was determined by NMR spectroscopy, X-ray analysis, chemical degradation, and modification of its functional groups. AMM consists of trans-decalin, tetramic acid, two unusual sugars (amycolose and amykitanose), and dichloropyrrole carboxylic acid. The pyranose ring named as amykitanose undergoes anomerization in methanol. AMM is a potent and broad-spectrum antibiotic against Gram-positive pathogenic bacteria by inhibiting DNA gyrase and bacterial topoisomerase IV. The target of AMM has been proved to be the DNA gyrase B subunit and its binding mode to DNA gyrase is different from those of novobiocin and coumermycin, the known DNA gyrase inhibitors.

Rapid effectiveness of minocycline or doxycycline against macrolide-resistant Mycoplasma pneumoniae infection in a 2011 outbreak among Japanese children

BACKGROUND

Mycoplasma pneumoniae is a major pathogen causing community-acquired pneumonia in children and young adults. Outbreaks typically occur at intervals of several years. In 2011, a widespread outbreak was associated with macrolide-resistant M. pneumoniae (MRMP) in Japanese children, often those of school age.

METHODS

Two hundred fifty-eight children were diagnosed with M. pneumoniae-associated pneumonia based on chest radiography, real-time polymerase chain reaction (PCR), and antibody titers between January and December 2011. Mycoplasma pneumoniae cultures obtained from nasopharyngeal samples using appropriate broth were subjected to real-time PCR, by which decreases in M. pneumoniae in patients treated with minocycline (MIN), doxycycline (DOX), or tosufloxacin (TFX) were calculated. Mutations of the 23S ribosomal RNA gene that confer high resistance to macrolides in M. pneumoniae were identified by DNA sequencing.

RESULTS

Among 202 M. pneumoniae isolates from M. pneumoniae-associated pneumonia patients, 176 (87.1%) were MRMP. Macrolide-resistant M. pneumoniae infection was significantly related to school age (P < .01) and initial administration of macrolides (P < .01). Minocycline or DOX (n = 125) or TFX or levofloxacin (n = 15) was used for definitive treatment of MRMP patients. Minocycline or DOX was significantly more effective than TFX (P ≤ .05) in achieving defervescence within 24 hours and in decreasing numbers of M. pneumoniae DNA copies 3 days after initiation.

CONCLUSIONS

Macrolides are inappropriate as first-choice agents against MRMP in terms of shortening the clinical course and decreasing M. pneumoniae. Control and prevention of MRMP outbreaks in children require early decreases in M. pneumoniae as well as improvement of clinical findings.

A challenge to appropriate antibiotic use in children with respiratory infections: a 5-year single-institution experience

BACKGROUND

We have studied the rate of emergence of antibiotic-resistant Streptococcus pneumoniae (S. pneumoniae) and Haemophilus influenzae (H. influenzae) and the subsequent antibiotic use in host patients of those isolates at the Department of Pediatrics, Soma General Hospital, Fukushima. Moreover, we carried out several studies investigating the risks and benefits of antibiotic-free treatment for children with respiratory infections. In this report, we summarize our research and suggest better treatment options for pediatric patients with respiratory infections.

METHODS

We investigated the necessity of antibiotic use in the treatment of pediatric inpatients with respiratory syncytial virus (RSV) infection, and tested our hypothesis that antibiotic-free treatment for common cold will reduce the number of resistant S. pneumoniae strains in the pediatric nasopharynx. Therefore, we restricted prescribing antibiotics for pediatric patients with respiratory infections. The rates of resistant S. pneumoniae and H. influenzae and the medication history of the host patients before and after the intervention were compared.

RESULTS

We found that most of the RSV-infected patients recovered without antibiotic treatment, and that the antibiotic-free treatment inhibited the emergence of antibiotic-resistant strains. The rate of penicillin-resistant S. pneumoniae decreased but the rate of ampicillin-resistant H. influenzae did not change significantly during the study.

CONCLUSION

We concluded that patients with respiratory infections can be treated without antibiotics, under careful examination and observation. Continued monitoring of such new interventions as well as recommending their use to other caregivers and physicians will help inhibit the spread of resistant strains.

S-carboxymethylcysteine inhibits adherence of Streptococcus pneumoniae to human alveolar epithelial cells

Streptococcus pneumoniae is a major pathogen of respiratory infections that utilizes platelet-activating factor receptor (PAFR) for firm adherence to host cells. The mucolytic agent S-carboxymethylcysteine (S-CMC) has been shown to exert inhibitory effects against infection by several respiratory pathogens including S. pneumoniae in vitro and in vivo. Moreover, clinical studies have implicated the benefits of S-CMC in preventing exacerbation of chronic obstructive pulmonary disease, which is considered to be related to respiratory infections. In this study, to assess whether the potency of S-CMC is attributable to inhibition of pneumococcal adherence to host cells, an alveolar epithelial cell line stimulated with interleukin-1α was used as a model of inflamed epithelial cells. Despite upregulation of PAFR by inflammatory activation, treatment with S-CMC efficiently inhibited pneumococcal adherence to host epithelial cells. In order to gain insight into the inhibitory mechanism, the effects of S-CMC on PAFR expression were also investigated. Following treatment with S-CMC, PAFR expression was reduced at both mRNA and post-transcriptional levels. Interestingly, S-CMC was also effective in inhibiting pneumococcal adherence to cells transfected with PAFR small interfering RNAs. These results indicate S-CMC as a probable inhibitor targeting numerous epithelial receptors that interact with S. pneumoniae.

Serotype distribution and antibiotic resistance of 140 pneumococcal isolates from pediatric patients with upper respiratory infections in Beijing, 2010

In the present study, the serotype distribution and antibiotic resistance of S. pneumoniae from pediatric patients with upper respiratory infections in Beijing, 2010 were described. 140 pneumococcal isolates were obtained, and the prevailing five serotypes were 19F (18.6%), 23F (9.3%), 14 (9.3%), 15 (9.3%), and 6A (7.1%). The vaccine coverage of PCV7, PCV10, and PCV13 were 43.6%, 43.6%, and 60.0%, respectively. According to the CLSI 2010 criteria, 99.3% of the S. pneumoniae isolates were susceptible to penicillin. The resistance rates to erythromycin and azithromycin were 96.4% and 97.1%, respectively. Meanwhile, 64.3% (90/140) of all pneumococcal isolates were multidrug-resistant S. pneumoniae (MDRSP). PCV13 covered 68.9% (62/90) of MDRSP strains, whereas it was 47.8% (43/90) for PCV7. ErmB was the dominant macrolide-resistance gene, whereas 30.4% pneumococcal isolates expressed both ermB and mefA. No isolate expressed ermTR. The potential coverage of PCV13 is higher than PCV7 and PCV10 because high rates of serotypes 6A and 19A, and the conjugate vaccines could prevent the spread of MDRSP. S. pneumoniae is still sensitive to penicillin. The resistance rate of S. pneumoniae to macrolides is high and ermB is the dominant macrolide-resistance gene in China, so continued surveillance of the antimicrobial susceptibility of S. pneumoniae may be necessary.

Non-antibiotic treatment for pediatric outpatients with common cold inhibits the emergence of drug resistant pneumococci

The occurrence of drug resistant Streptococcus pneurmoniae (S. pneumoniae) is very high in Japan. Unnecessary use of antibiotics had been thought to cause this problem but previous studies had not clearly showed that the decreasing rate of antibiotic use had been related to the reduction of the prevalence of resistant strains. In this study, we tried to prove that non-antibiotic treatment for common cold would reduce the antibiotic resistant S. pneumoniae in nasopharynx in children. Forty-five children with the common cold were randomly selected from pediatric patients who had taken antibiotics within the past three months. We collected nasopharyngeal swabs from all of the participants and once again after a period of 2 to 3 months without using any antibiotics. Twenty-four of these patients had the S. pneumoniae strains isolated. Then these strains were undergone a susceptibility test and drug-resistant gene detection. The susceptibility test reveled that patients with penicillin-resistant strains decreased from 17 to 7 (p < 0.01). The test also reveled that the decreased number of patients had strains that were resistant to cefditren. The gene detection revealed that none of the patients acquired a higher resistance to penicillin. Our study suggests that the treatment without antibiotics reduces the drug-resistant S. pneumoniae. Controlled antibiotic use in children might prevent children from carrying the antibiotic resistant S. pneumoniae.

Nasopharyngeal Streptococcus pneumoniae carriage in Japanese children attending day-care centers

OBJECTIVES

We conducted a prospective bacteriological survey to investigate antibiotic resistance-related genetic characteristics and the turnover of nasopharyngeal Streptococcus pneumoniae carriage in healthy children in day-care centers (DCCs).

METHODS

A total of 363 nasopharyngeal mucus samples were collected from children aged 0 to 6 years attending two DCCs in the summer of 2004 (n=181) and the following winter (n=182). We obtained 157 S. pneumoniae isolates and analyzed them by antibiotic susceptibility testing, PCR assay for the penicillin-binding protein (PBP) genes and macrolide-resistance gene, and pulsed-field gel electrophoresis (PFGE).

RESULTS

The overall carriage rate was 43.3% (157/363). The percentages of penicillin-intermediately resistant S. pneumoniae (PISP) strains, penicillin-resistant S. pneumoniae (PRSP) strains, erythromycin-intermediately resistant S. pneumoniae strains and erythromycin-resistant S. pneumoniae strains were 35.7% (56/157), 0.6% (1/157), 1.9% (3/157), and 69.4% (109/157), respectively. The percentages of S. pneumoniae strains with the pbp mutation(s) and mefA and/or ermB gene(s) were 92.4% (145/157) and 71.3% (112/157), respectively. Fifty strains with different PFGE patterns were obtained from among the 157 isolates. Thirteen strains were observed in both seasons, but only one of these strains was isolated from the same carrier. Twenty-one strains (42.0%) were isolated from two or more children, and 17 of these were each isolated from children attending the same DCC.

CONCLUSIONS

These results indicate the spread of S. pneumoniae, particularly those with antibiotic-resistance genes, and the vigorous genetic turnover and substantial horizontal transmission of this pathogen in healthy children attending DCCs in Japan.

Specific inhibitions of annonaceous acetogenins on class II 3-hydroxy-3-methylglutaryl coenzyme A reductase from Streptococcus pneumoniae

3-Hydroxy-3-methylglutaryl coenzyme A reductase (class II HMGR) could serve as a potential target to discover drugs fighting against the invasive diseases originated from Streptococcus pneumoniae, one of the major causes of bacterial disease in human. However, no strongly effective inhibitors of class II HMGR have been found so far. In the present study, for the first time, four annonaceous acetogenins (ACGs) were explored for the inhibition on S. pneumoniae HMGR. The results showed that the ACGs had higher inhibitory activities against S. pneumoniae HMGR with K(i) values in the range of 6.45-20.49 μM than the statin drug lovastatin (K(i)=116.25 μM), a classical inhibitor of class I HMGR. Then, three-dimensional modeling and docking simulations analyzed the possible binding mode of ACGs to S. pneumoniae HMGR and suggested a kind of novel structural and binding mode for designing promising inhibitor candidates of the targeted enzyme S. pneumoniae II HMGR.

Nationwide surveillance of bacterial respiratory pathogens conducted by the Japanese Society of Chemotherapy in 2008: general view of the pathogens' antibacterial susceptibility

For the purpose of nationwide surveillance of the antimicrobial susceptibility of bacterial respiratory pathogens collected from patients in Japan, the Japanese Society of Chemotherapy conducted a third year of nationwide surveillance during the period from January to April 2008. A total of 1,097 strains were collected from clinical specimens obtained from well-diagnosed adult patients with respiratory tract infections. Susceptibility testing was evaluable with 987 strains (189 Staphylococcus aureus, 211 Streptococcus pneumoniae, 6 Streptococcus pyogenes, 187 Haemophilus influenzae, 106 Moraxella catarrhalis, 126 Klebsiella pneumoniae, and 162 Pseudomonas aeruginosa). A total of 44 antibacterial agents, including 26 β-lactams (four penicillins, three penicillins in combination with β-lactamase inhibitors, four oral cephems, eight parenteral cephems, one monobactam, five carbapenems, and one penem), three aminoglycosides, four macrolides (including a ketolide), one lincosamide, one tetracycline, two glycopeptides, six fluoroquinolones, and one oxazolidinone were used for the study. Analysis was conducted at the central reference laboratory according to the method recommended by the Clinical and Laboratory Standard Institute (CLSI). The incidence of methicillin-resistant S. aureus (MRSA) was as high as 59.8%, and those of penicillin-intermediate and penicillin-resistant S. pneumoniae (PISP and PRSP) were 35.5 and 11.8%, respectively. Among H. influenzae, 13.9% of them were found to be β-lactamase-non-producing ampicillin (ABPC)-intermediately resistant (BLNAI), 26.7% to be β-lactamase-non-producing ABPC-resistant (BLNAR), and 5.3% to be β-lactamase-producing ABPC-resistant (BLPAR) strains. A high frequency (76.5%) of β-lactamase-producing strains was suspected in Moraxella catarrhalis isolates. Four (3.2%) extended-spectrum β-lactamase-producing K. pneumoniae were found among 126 strains. Four isolates (2.5%) of P. aeruginosa were found to be metallo β-lactamase-producing strains, including three (1.9%) suspected multidrug-resistant strains showing resistance to imipenem, amikacin, and ciprofloxacin. Continual national surveillance of the antimicrobial susceptibility of respiratory pathogens is crucial in order to monitor changing patterns of susceptibility and to be able to update treatment recommendations on a regular basis.

Characteristic findings of pediatric inpatients with pandemic (H1N1) 2009 virus infection among severe and nonsevere illnesses

We analyzed the clinical features of inpatients at a Japanese pediatric department who were infected with pandemic (H1N1) 2009 virus. Study participants included 46 children hospitalized from July 2009 to January 2010. Infection with the virus was confirmed using real-time reverse transcriptase polymerase chain reaction (RT-PCR). The epidemic month was October 2009; 34 patients were boys, and median age was 7 years. Pandemic influenza-associated respiratory diseases included pneumonia (n = 42), bronchitis (n = 3), and pharyngitis (n = 1). The median time from onset to admission was 3 days. Children were divided into those with severe (n = 32) versus nonsevere illnesses (n = 14) according to Japanese guidelines. Significant features in the severe group were younger age, previous asthmatic attack, exacerbation of asthma, decreased oxygen saturation, elevated white blood cell/neutrophil counts and serum lactate dehydrogenase, and longer times from admission to being afebrile and discharged. Both groups showed lymphopenia at admission. Additional infection with Streptococcus pneumoniae was frequent in the severe group. Whereas 44 patients received antiviral therapy (median times from onset to initiation 2 days), 32 received antibiotics (median duration 7 days). All children recovered, with a median hospital stay of 8 days. Our observations suggest that history of asthma and preschool age might be risk factors for severe illness. Prompt initiation of antiviral and antibiotic treatments should be considered to prevent development of severe illness.

Clonal spread of beta-lactamase-producing amoxicillin-clavulanate-resistant (BLPACR) strains of non-typeable Haemophilus influenzae among young children attending a day care in Japan

OBJECTIVE

Resistant strains of non-typeable Haemophilus influenzae (NTHi) are one of the principal causes of recurrent acute otitis media (otitis prone), rhinosinusitis, and pneumonia in young children. Beta-lactamase-nonproducing ampicillin-resistant (BLNAR) strains are particularly common in Japan, and beta-lactamase-producing amoxicillin-clavulanate resistant (BLPACR) strains are now emerging. We investigated the nasopharyngeal carriage status of these resistant strains among children attending a same day care center during a 10-year period.

METHODS

From 1999 to 2008, we obtained nasopharyngeal swab specimens from young children attending a same day care center and examined the incidence of resistant strains of NTHi. Antimicrobial resistance of NTHi was identified based on PCR analysis of mutation of the penicillin binding protein (PBP) genes. Pulsed-field gel electrophoresis (PFGE) was performed to examine the clonal relationship of each resistant strain.

RESULTS

The prevalence of resistant strains of NTHi among the children attending this day care has significantly increased during the past 10 years and most of this day care children recently have resistant strains with PBP gene mutations in their nasopharynx. Genetically BLPACR (gBLPACR) strains have rapidly increased since 2007 and PFGE analysis demonstrated that all gBLPACR were clonally identical. This is the first report of apparent clonal dissemination of gBLPACR strains of NTHi occurring in a certain environment such as day care.

CONCLUSIONS

The rapidly increasing prevalence of resistant strains, in particular gBLPACR, in this day care center may predict a high incidence of these resistant bacteria from clinical isolates in the near future and potential serious medical problems worldwide.

Summary of invasive pneumococcal disease burden among children in the Asia-Pacific region

Invasive pneumococcal disease (IPD) burden is significant in the Asia-Pacific region. This review describes the epidemiology and Streptococcus pneumoniae (SP) serotype distribution of IPD in children in the Asia-Pacific region from studies published from 1999 to 2010. IPD incidence varies widely in Asia-Pacific countries depending on the method of surveillance, the population studied, and the time period. Incidences are highest for younger children, with rates near 100-200 cases per 100,000 children aged <1 or 2 years. Incidences of preventable disease are estimated to be 6-200 cases per 100,000. Heptavalent pneumococcal conjugate vaccine (PCV7) serotype coverage shows a very wide range over the Asia-Pacific region. Ten countries have high vaccine serotype coverage (>70%), and six countries have low vaccine serotype coverage (<50%). The majority of SP serotypes in children with IPD in most countries in the Asia-Pacific region are susceptible to penicillin (intermediate and resistant <50%); a few countries have SP serotypes with high level resistance to penicillin (intermediate and resistant >50%). Japan, Taiwan, and Thailand have high PCV7 serotype coverage. Countries with low pneumococcal resistance to antimicrobials have shown increasingly higher nonsusceptibility with time. National vaccination programmes that include PCV7, 10-valent pneumococcal conjugate vaccine (PCV), or 13-valent PCV would significantly affect IPD burden in children aged <5 years in the Asia-Pacific region, as well as the burden of penicillin-nonsusceptible IPD.

Trends in antimicrobial susceptibility of Streptococcus pneumoniae in the Tohoku district of Japan: a longitudinal analysis from 1998 to 2007

Streptococcus pneumoniae is a common cause of respiratory tract infections (RTIs). The prevalence of Streptococcus pneumoniae strains with reduced susceptibility to antimicrobial agents has dramatically increased worldwide. Susceptibility to nine antimicrobial agents and serotypes were determined among 1,644 Streptococcus pneumoniae strains isolated from patients with RTIs in the Tohoku district of Japan from October to December every year from 1998 to 2007. The prevalence of penicillin G-nonsusceptible Streptococcus pneumoniae (PNSP) strains increased gradually from 48.5% in 1998, reached a statistical peak in 2004 (65.1%) and then decreased to 51.5% in 2007. Streptococcus pneumoniae strains with each serotype 3, 6, 19 and 23 were constantly detected, and the distribution of these serotypes in PNSP strains did not significantly change during the study period. A trend of Streptococcus pneumoniae strains nonsusceptible to other beta-lactams tested was similar to that of PNSP strains, except for cefditoren, to which the resistance rate was < 20% throughout the analysis period. The prevalence of strains nonsusceptible to erythromycin and minocycline were consistently > 60%. Almost all penicillin G-resistant Streptococcus pneumoniae (PRSP) strains were resistant to both erythromycin and minocycline throughout the analysis period. The prevalence of strains resistant to fluoroquinolones tested were < 3% over the study period. Our longitudinal surveillance demonstrated for the first time that decreased prevalence of both beta-lactam- and multidrug-resistant strains has been occurring since 2004 in a region of Japan. Careful monitoring of antimicrobial susceptibility of Streptococcus pneumoniae should be continued.

Purulent pericarditis due to Streptococcus pneumoniae diagnosed by pneumococcal urinary antigen assay and 16S rDNA sequence of the pericardial fluid

A 57-year old woman was admitted to our hospital with massive pericardial fluid. Culture of the pericardial fluid was negative, however, Binax NOW Streptococcus pneumoniae urinary antigen test was positive in pericardial fluid. 16S rDNA sequencing and PCR for lyt(A) gene of the pericardial fluid sample confirmed the microbiological diagnosis of S. pneumoniae. The patient was treated with surgical drainage and continuous intravenous infusion of penicillin G and its concentration in the serum and pericardial effusion was monitored. Incorporation of molecular methods such as antigen testing and nucleic acid sequencing would benefit the management of infectious diseases especially in culture negative cases.

[A case of empyema in a previously healthy child caused by Streptococcus pneumoniae serotype 1]

A 6-year-old boy admitted for empyema was found to have Streptococcus pneumoniae serotype 1 isolated from both blood and drainage fluid. The organism had no mutated genes encoding penicillin-binding proteins and was susceptible to all antibiotics. Empyema caused by S. pneumoniae serotype 1 in childhood has not, to our knowledge, been reported in Japan. In many countries where nanovalent pneumococcal conjugate vaccine (PCV7) has been introduced, serotype 1 frequency is especially high and empyema prevalence has increased. Monitoring of this S. pneumoniae serotype may be more important in invasive pneumococcal disease (IPD) than previously thought, especially in empyema, even after PCV7 is introduced in Japan.

Streptococcus pneumoniae and Haemophilus influenzae at the initial stage of influenza

BACKGROUND

Streptococcus pneumoniae and Haemophilus influenzae infections in children with influenza have been noted because of the severity of co-infection. In Japan, vaccination against S. pneumoniae and H. influenzae infections has been listed in the vaccine program in 2008, but the characteristics of the two organisms, colonizing at the initial stage of influenza infection, have not been investigated in detail.

METHODS

Nasopharyngeal swabs from children with influenza (flu(+)) (n= 236; mean age, 6.2 years) were examined for bacterial pathogens, including S. pneumoniae and H. influenzae. They were then examined for serotypes, drug susceptibilities, and resistance genes (or gene mutations). As a reference, children with upper respiratory tract infection (URTI(+), flu(-); n = 189; mean age, 6.2 years) were also examined.

RESULTS

S. pneumoniae, beta-streptococci (groups A, B, and G), methicillin-susceptible and -resistant S. aureus, Moraxella catarrhalis, and H. influenzae were isolated. For S. pneumoniae, nine serotypes were detected with prevalent types of 3, 6, 19 and 23. Penicillin resistance was detected in types 19 and 23, while resistance to macrolide and clindamycin was found in various types. For H. influenzae, only b serotype was detected, with marked ampicillin resistance. The majority was non-typeable. Very similar results were obtained even in URTI(+) (flu(-)) cases.

CONCLUSION

Multiple drug-resistant S. pneumoniae with major serotypes, for example, 19 and 23 and H. influenzae with serotype b were already present at the initial stage of influenza infection, similar to URTI(+) flu(-) cases. They could be prevented by current vaccines, but drug-resistant non-typeable H. influenzae is troubling.

Susceptible bacteria increased with limited usage of antibiotics: data with emphasis on defined daily doses

BACKGROUND

Resistant bacteria Haemophilus influenzae and Streptococcus pneumoniae are the primary causative organisms of bacterial respiratory tract infections and meningitis in children.

METHODS

This study was carried out over 4 years. Specimens from the pharynges and sputum of children were collected. H. influenzae and S. pneumoniae were cultured, and the sensitivity to antibiotics were measured. The dosages of major antibiotics for children were calculated.

RESULTS

A total of 920 samples of H. influenzae and 128 samples of S. pneumoniae collected from the specimens from the pharynges and sputum were cultured. The level of non-sensitive H. influenzae for cefaclor decreased from 62.1% to 50.3% (P= 0.0398). The level of non-sensitive S. pneumoniae for amoxicillin decreased sharply from 31.6% to 0.0%. Finally, the total amount of antibiotics was reduced to 40.5% of the first period.

CONCLUSION

It is possible to reduce the levels of non-susceptible bacteria by limited usage of antibiotics for daily treatment.

Serotype and antibiotic resistance of isolates from patients with invasive pneumococcal disease in Japan

Invasive pneumococcal disease (IPD) is of concern in Japan, where the heptavalent pneumococcal conjugate vaccine (PCV7) is unavailable. We determined serotypes, genotypes indicating beta-lactam resistance, and antibiotic susceptibilities of 496 isolates from normally sterile sites in patients (193 children, 303 adults) from 186 institutions between August 2006 and July 2007. Disease presentations included sepsis (46.2%), pneumonia (31.5%), and meningitis (17.5%). Mortality was 1.4% in children and 22.1% in adults, many of whom had underlying diseases. In children, serotype 6B (22.5%) was followed by 19F (14.1%), and 14 (13.1%); potential coverages of PCV7 and PCV13 were 75.4% and 93.7%, respectively. In adults, serotype 12F (14.3%) was followed by 3 (11.3%), and 6B (10.3%); 23-valent polysaccharide vaccine (PPV23) coverage was 85.4%. Most serotype 12F strains were gPISP, with pbp2b gene alteration; carbapenem had an excellent MIC90. PCV7 is recommended for children and PPV23 for adults to increase prevention against IPD.

Expression, purification, characteristics and homology modeling of the HMGS from Streptococcus pneumoniae

OBJECTIVE

To understand the molecular basis for a potential reaction mechanism and develop novel antibiotics with homology modeling for 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) synthase (HMGS).

METHODS

The genetic engineering technology and the composer module of SYBYL7.0 program were used, while the HMGS three-dimensional structure was analyzed by homology modeling.

RESULTS

The mvaS gene was cloned from Streptococcus pneumoniae and overexpressed in Escherichia coli from a pET28 vector. The expressed enzyme (about 46 kDa) was purified by affinity chromatography with a specific activity of 3.24 micromol/min/mg. Optimal conditions were pH 9.75 and 10 mmol/L MgCl2 at 37 degrees C. The V(max) and K(m) were 4.69 micromol/min/mg and 213 micromol/L respectively. The 3D model of S. pneumoniae HMGS was established based on structure template of HMGS of Enterococcus faecalis.

CONCLUSION

The structure of HMGS will facilitate the structure-based design of alternative drugs to cholesterol-lowering therapies or to novel antibiotics to the Gram-positive cocci, whereas the recombinant HMGS will prove useful for drug development against a different enzyme in the mevalonate pathway.

Prevention and treatment of penicillin-resistant Streptococcus pneumoniae meningitis after intracraniofacial surgery with distraction osteogenesis

The prevalence of penicillin-resistant Streptococcus pneumoniae (PRSP) meningitis has increased worldwide, particularly in East Asia and the United States. We recently experienced a case of PRSP meningitis that developed during frontofacial distraction. The patient was a 7-year-old girl with Crouzon disease who was treated by frontofacial monobloc/Le Fort IV minus glabellar osteotomy with quadruple internal distraction devices. Penicillin-resistant Streptococcus pneumoniae meningitis was diagnosed after surgery and treated successfully with meropenem (a carbapenem) at 120 mg kg d every 8 hours, ceftriaxone (a third-generation cephalosporin) at 100 mg kg d every 12 hours, and vancomycin (a glycopeptide) at 45 mg kg d every 6 hours. This case indicates that severe and fatal bacterial meningitis may occur as a postoperative complication due to multidrug-resistant bacteria indigenous to the nasal cavity after simultaneous osteotomy of the cranium and facial bone in intracraniofacial surgery, such as that for syndromic craniosynostosis and hypertelorbitism. In such cases, preventive strategies should include preoperative administration of pneumococcal vaccine, preoperative screening of nasal bacterial flora by nasal culture test, and prior administration of a carbapenem with good cerebrospinal fluid transfer or a third- or fourth-generation cephem covering PRSP. Postoperatively, suspected meningitis may be treated with a combination of the 3 drugs used in our case, in parallel with emergency cephalic contrast computed tomography and culture tests of blood and cerebrospinal fluid. Our experience suggests that these measures will facilitate a successful outcome in frontofacial distraction osteogenesis.

Capsular type and antibiotic resistance in Streptococcus agalactiae isolates from patients, ranging from newborns to the elderly, with invasive infections

Streptococcus agalactiae isolates (n = 189) from patients with invasive infections were analyzed for capsular type by PCR, for antimicrobial susceptibility, and for the presence of resistance genes. In contrast to the predominance of capsular type III in children, types Ib and V were most common among adults. All 45 levofloxacin-resistant strains had two amino acid substitutions, Ser(81)Leu in the gyrA gene and Ser(79)Phe in the parC gene, and showed similar pulsed-field gel electrophoresis patterns.

Comprehensive detection of causative pathogens using real-time PCR to diagnose pediatric community-acquired pneumonia

We have developed a real-time reverse transcription-PCR (RT-PCR) method to detect 13 respiratory viruses: influenza virus A and B; respiratory syncytial virus (RSV) subgroup A and B; parainfluenza virus (PIV) 1, 2, and 3; adenovirus; rhinovirus (RV); enterovirus; coronavirus (OC43); human metapneumovirus (hMPV); and human bocavirus (HBoV). The new method for detection of these viruses was applied simultaneously with real-time PCR for the detection of six bacterial pathogens in clinical samples from 1700 pediatric patients with community-acquired pneumonia (CAP). Of all the patients, 32.5% were suspected to have single bacterial infections; 1.9%, multiple bacterial infections; 15.2%, coinfections of bacteria and viruses; 25.8%, single viral infections; and 2.1%, multiple viral infections. In the remaining 22.6%, the etiology was unknown. The breakdown of suspected causative pathogens was as follows: 24.4% were Streptococcus pneumoniae, 14.8% were Mycoplasma pneumoniae, 11.3% were Haemophilus influenzae, and 1.4% were Chlamydophila pneumoniae. The breakdown of viruses was as follows: 14.5% were RV, 9.4% were RSV, 7.4% were hMPV, 7.2% were PIV, and 2.9% were HBoV. The new method will contribute to advances in the accuracy of diagnosis and should also result in the appropriate use of antimicrobials.

Serotype distribution and penicillin resistance of Streptococcus pneumoniae isolates from middle ear fluids of pediatric patients with acute otitis media in Japan

Out of 175 pneumococcal isolates from middle ear fluids, 26.3% were penicillin-resistant S. pneumoniae (PRSP). Serotypes 19F and 23F occurred most frequently among PRSP strains. The 7-valent pneumococcal conjugate vaccine (PCV) showed better coverage of PRSP strains (87.0%). The 7-valent PCV may reduce the prevalence of PRSP in Japan.

The first nationwide surveillance of bacterial respiratory pathogens conducted by the Japanese Society of Chemotherapy. Part 1: a general view of antibacterial susceptibility

The Japanese Society of Chemotherapy (JSC) conducted the first nationwide surveillance of bacterial respiratory pathogens during the period from January to August 2006. With the cooperation of 32 medical institutions throughout Japan, a total of 924 strains belonging to seven clinically relevant bacterial species were collected from adult patients with well-diagnosed respiratory tract infections (RTIs). Antimicrobial susceptibility testing of the 887 evaluable strains (205 Staphylococcus aureus, 200 Streptococcus pneumoniae, 9 Streptococcus pyogenes, 165 Haemophilus influenzae, 91 Moraxella catarrhalis, 74 Klebsiella pneumoniae, and 143 Pseudomonas aeruginosa) to 42 antibacterial agents was conducted at the Central Laboratory of the Research Center for Anti-infective Drugs of the Kitasato Institute, according to recommendations issued by the Clinical and Laboratory Standards Institute (CLSI). The antibacterial agents employed were 25 beta-lactams, three aminoglycosides, four macrolides (including one azalide and one ketolide), one lincosamide, one tetracycline, two glycopeptides, five fluoroquinolones, and one oxazolidinone. The incidence of methicillin-resistant S. aureus (MRSA) was 63.4%, and the incidences of penicillin-intermediately resistant S. pneumoniae (PISP) and penicillin-resistant S. pneumoniae (PRSP) were 35.0% and 4.0%, respectively. Among H. influenzae, 21.2% of the strains were found to be beta-lactamase-nonproducing ampicillin (ABPC)-intermediately resistant (BLNAI), 29.1% to be beta-lactamase-nonproducing ABPC-resistant (BLNAR), and 4.8% to be beta-lactamaseproducing ABPC-resistant (BLPAR) strains. The incidence of extended-spectrum beta-lactamase-producing K. pneumoniae was 2.7% (2 of 74 strains). Three (2.1%) of the 143 P. aeruginosa strains were found to be metallo-beta-lactamaseproducing, including 1 (0.7%) multidrug-resistant strain. Through the nationwide surveillance, we obtained fundamental antimicrobial susceptibility data of clinically relevant bacterial pathogens in adult RTI to various antibacterial agents. These data will be a useful reference for future periodic surveillance studies, as well as for investigations to control antimicrobial-resistant pathogens.

Positive selection in penicillin-binding proteins 1a, 2b, and 2x from Streptococcus pneumoniae and its correlation with amoxicillin resistance development

The efficacy of beta-lactam antibiotics in Streptococcus pneumoniae has been compromised because of the development of altered penicillin-binding proteins (PBPs), however, this has been less so for amoxicillin than for penicillin. Recently, there have been a number of important methods developed to detect molecular adaptation in protein coding genes. The purpose of this study is to employ modern molecular selection approaches to predict sites under positive selection pressure in PBPs, derived from a large international S. pneumoniae collection of amoxicillin resistant and susceptible isolates, and encompassing a comparative data set of 354 pbp1a, 335 pbp2b, and 389 pbp2x gene sequences. A correspondence discriminant analysis (CDA) of positively selected pbp sites and amoxicillin MIC (minimum inhibitory concentration) values is then used to detect sites under positive selection pressure that are important in discriminating different amoxicillin MICs. Molecular adaptation was evident throughout PBP2X, with numerous positively selected sites in both the transpeptidase (TP) and C-terminal domains, strongly correlated with discriminating amoxicillin MICs. In the case of PBP1A positive selection was present in the glycosyltransfer (GT), TP and C-terminal domains. Sites within the TP domain tended to be correlated with the discrimination of low from intermediate MICs, whereas sites within the C-terminal tail, with a discrimination of intermediate from fully resistant. Most of the positively selected sites within PBP2B were in the N-terminal domain and were not correlated with amoxicillin MICs, however, several sites taken from the literature for the TP domain were strongly associated with discriminating high from intermediate level amoxicillin resistance. Many of the positively selected sites could be directly associated with functional inferences based on the crystal structures of these proteins. Our results suggest that clinical emphasis on TP domain sequences of these proteins may result in missing information relevant to antibiotic resistance development.

Multidrug-resistant Streptococcus pneumoniae infections: current and future therapeutic options

Antibacterial resistance in Streptococcus pneumoniae is increasing worldwide, affecting principally beta-lactams and macrolides (prevalence ranging between approximately 1% and 90% depending on the geographical area). Fluoroquinolone resistance has also started to emerge in countries with high level of antibacterial resistance and consumption. Of more concern, 40% of pneumococci display multi-drug resistant phenotypes, again with highly variable prevalence among countries. Infections caused by resistant pneumococci can still be treated using first-line antibacterials (beta-lactams), provided the dosage is optimised to cover less susceptible strains. Macrolides can no longer be used as monotherapy, but are combined with beta-lactams to cover intracellular bacteria. Ketolides could be an alternative, but toxicity issues have recently restricted the use of telithromycin in the US. The so-called respiratory fluoroquinolones offer the advantages of easy administration and a spectrum covering extracellular and intracellular pathogens. However, their broad spectrum raises questions regarding the global risk of resistance selection and their safety profile is far from optimal for wide use in the community. For multi-drug resistant pneumococci, ketolides and fluoroquinolones could be considered. A large number of drugs with activity against these multi-drug resistant strains (cephalosporins, carbapenems, glycopeptides, lipopeptides, ketolides, lincosamides, oxazolidinones, glycylcyclines, quinolones, deformylase inhibitors) are currently in development. Most of them are only new derivatives in existing classes, with improved intrinsic activity or lower susceptibility to resistance mechanisms. Except for the new fluoroquinolones, these agents are also primarily targeted towards methicillin-resistant Staphylococcus aureus infections; therefore, demonstration of their clinical efficacy in the management of pneumococcal infections is still awaited.

Meta-analysis of antibiotic susceptibility and the genotype of penicillin-binding proteins in Streptococcus pneumoniae

To further understanding of the mechanisms of development of resistance to penicillin in Streptococcus pneumoniae, and the role of penicillin-binding proteins (PBPs) mutations to antibiotics resistance a meta-analysis was performed. Major databases, Pubmed, Current Contents, Biosis previews, Web of Science, were searched for studies that published within 1997 through to 2007, and reported the penicillin MIC and the alteration of PBP 1a, 2b and 2x (genes or proteins) of clinical S. pneumoniae isolates. Papers were reviewed by 2 persons and used standard criteria to enroll them. Meta-analysis was performed using a random-effects model. Overall, 20 studies were included in the meta-analysis. For the included 1771 clinical S. pneumoniae isolates, the susceptibility to penicillin decreased in inverse proportion to the presence of mutated pbp genes. The mutations of the conserved amino acid motifs STMK and SRNVP of PBP 1A, STMK and LKSG of PBP2X, and SSNT of PBP2B are critical for the penicillin resistance. Those motifs can be used as markers for the penicillin susceptibility of S. pneumoniae. These results are useful in helping define the mechanism of penicillin resistance in S. pneumoniae.

High prevalence of erythromycin resistance and macrolide-resistance genes, mefA and ermB, in Streptococcus pneumoniae isolates from the upper respiratory tracts of children in the Sapporo district, Japan

Our previous study demonstrated that the frequency of penicillin-resistant Streptococcus pneumoniae (PRSP) was lower in our district than in districts in other Japanese studies. In this study, we investigated the prevalence of erythromycin resistance. The susceptibility to erythromycin and the distribution of the macrolide-resistance genes, mefA and ermB, were examined in S. pneumoniae isolates from the upper respiratory tracts of children in four cities in the Sapporo district, Hokkaido prefecture, Japan. Of the 156 isolates, 27 (17.3%) were erythromycin-sensitive, 6 (3.9%) were erythromycin-intermediately resistant, and 123 (78.9%) were erythromycin-resistant. Fifty-nine (37.8%) had the mefA gene, 89 (57.1%) had the ermB gene, and 129 (82.7%) had the mefA and/or the ermB gene. The ermB-positive isolates tended to show high resistance to erythromycin. Erythromycin-resistant isolates and the macrolide-resistance genes were often present in infants or younger children. The frequency of erythromycin-resistant isolates in the four cities was very high, ranging from 76.3% to 83. 3%, as high as the national average. Although erythromycin-resistant isolates generally tend to show cross-resistance to penicillin, the frequency of PRSP was very low in this study, as compared with other Japanese studies. Erythromycin resistance was frequently recognized not only in PRSP but also in penicillin-sensitive S. pneumoniae (PSSP) as well. In Japan, erythromycin resistance may have already become widespread, even in local areas where penicillin resistance is not especially prevalent.

Recurrence of occult pneumococcal bacteremia by an identical strain in an apparently healthy child

This is the first report to describe an apparently healthy girl, who developed recurrent occult bacteremia by the same Streptococcus pneumoniae strain, at 11 and 15 months of age. The two separately isolated organisms were demonstrated to have the identical serotype (type 6B), antibiotic susceptibility (intermediately penicillin-resistant), genotypes of penicillin-binding proteins, and patterns of pulse-field gel electrophoresis. The serum levels of anti-type 6B antibodies showed poor responses after both bacteremic episodes, but other immunological workups did not demonstrate any abnormalities. This case indicates that occult bacteremia may recur due to an identical pneumococcal strain in an immunocompetent infant, and that early introduction of pneumococcal conjugate vaccine is necessary in Japan.

Bactericidal activities of parenteral antibiotics and genotype of penicillin-binding protein in Streptococcus pneumoniae and Haemophilus influenzae isolated from children's blood

A total of 16 isolates of Streptococcus pneumoniae and 18 isolates of Haemophilus influenzae were obtained from the blood of children admitted to the pediatric wards of hospitals in Hokkaido Kamikawa subprefecture between January 2003 and December 2005. The ages of the patients with S. pneumoniae or H. influenzae infection ranged from 2 months to 9 years and from 1 month to 4 years, respectively. The diagnoses of S. pneumoniae infection were as follows: pneumonia in 8 patients, occult bacteremia in 5 patients, and meningitis in 3 patients. The diagnoses of H. influenzae were: meningitis in 6 patients, pneumonia in 4 patients, occult bacteremia in 4 patients, epiglotitis in 2 patients, and facial cellulitis in 2 patients. Out of 16 S. pneumoniae isolates, penicillin-resistant strains with a mutation of 3 genes were observed in 7 children, and penicillin intermediate-resistant strains with a mutation of 1 or 2 genes were observed in 8 children. Out of 18 H. influenzae isolates, the beta-lactamase-negative ampicillin-resistant strain with a substitution of 2 points in the ftsI gene was revealed in 2 children, the beta-lactamase-negative ampicillin-resistant strain with a substitution of 1 point in the ftsI gene was observed in 4 children, the beta-lactamase-positive amoxicillin/clavulanic acid-resistant strain with blaTEM-1 and ftsI with 2 substitutions in the ftsI gene was observed in 3 children, and the beta-lactamase-positive ampicillin-resistant strain with blaTEM-1was not observed. The MBC90s of ampicillin, ceftriaxone, cefotaxime, meropenem, panipenem, and vancomycin against S. pneumoniae were 8 microg/ml, 1 microg/ml, 1 microg/ml 1 microg/ml, 0.25 microg/ml, and 0.5 microg/ml, respectively. Those of ampicillin, piperacillin, ceftriaxone, cefotaxime, meropenem, and panipenem against H. influenzae were >128 microg/ml, >128 microg/ml, 0.25 microg/mL, 1 microg/ml, 0.12 microg/ml, and 0.5 g/ml, respectively. It is suggest that the minimum bactricidal concentration (MBC) was dissociated from the minimum inhibitory concentration (MIC) in S. pneumoniae and H. influenzae with abnormal pbp genes.

Alterations of pbp1a, pbp2b, and pbp2x in Streptococcus pneumoniae isolates from children with otolaryngological infectious disease in the Sapporo district of Japan

Evaluation of beta-lactam susceptibility and polymerase chain reaction (PCR)-based genotyping of penicillin-binding proteins (PBP) 1A, 2B, and 2X were performed for Streptococcus pneumoniae isolates from children with otolaryngological infectious disease in the Sapporo district, Hokkaido Prefecture, Japan. Of 174 S. pneumoniae isolates, 14 (8%) were penicillin-resistant S. pneumoniae (PRSP), 87 (50%) were penicillin-intermediately-resistant, and 73 (42%) were penicillin-sensitive. Seventy-six (44%) had alterations in all of the three genes examined (pbp1a, pbp2b, and pbp2x), 81 (47%) had alterations in one or two of the genes, and 17 (10%) had no alterations. Isolates with alterations in all three genes showed low susceptibility to penicillin, while, in contrast, isolates with no alteration showed relatively high susceptibility to penicillin. Similar relationships were observed for other beta-lactams. The prevalence of PRSP in our study ranged from 5% to 12.8% (average, 8%), and there was much variation in the prevalence of PBP gene alterations among the cities. The results suggest that local differences in patterns of PBP gene alterations can be observed even at the district level. PCR-based genotyping of PBP genes is rapid, convenient, and useful to investigate genetic susceptibility to beta-lactams. Further, not only nationwide or prefectural surveys but also local surveillance at the district level is important for determining antimicrobial susceptibility status in daily practice.