Antimicrobial-resistant Streptococcus pneumoniae: trends and management

Comparative genomics analysis of Streptococcus iniae isolated from Trachinotus ovatus: novel insight into antimicrobial resistance and virulence differentiation

BACKGROUND

Streptococcus iniae is an important fish pathogen that cause significant economic losses to the global aquaculture industry every year. Although there have some reports on the genotype of S.iniae and its relationship with virulence, no genome-scale comparative analysis has been performed so far. In our previous work, we characterized 17 isolates of S.iniae from Trachinotus ovatus and divided them into two genotypes using RAPD and rep-PCR methods. Among them, BH15-2 was classified as designated genotype A (in RAPD) and genotype 1 (in rep-PCR), while BH16-24 was classified as genotype B and genotype 2. Herein, we compared the differences in growth, drug resistance, virulence, and genome between BH15-2 and BH16-24.

RESULTS

The results showed that the growth ability of BH16-24 was significantly faster than that of BH15-2 at the exponential stage. Antimicrobial tests revealed that BH15-2 was susceptible to most of the tested antibiotics except neomycin and gentamycin. In contrast, BH16-24 was resistant to 7 antibiotics including penicillin, sulfasomizole, compound sulfamethoxazole tablets, polymyxin B, spectinomycin, rifampin and ceftazidime. Intraperitoneal challenge of T.ovatus, showed that the LD50 value of BH15-2 was 4.0 × 102 CFU/g, while that of BH16-24 was 1.2 × 105 CFU/g. The genome of S.iniae BH15-2 was 2,175,659 bp with a GC content of 36.80%. Meanwhile, the genome of BH16-24 was 2,153,918 bp with a GC content of 36.83%. Comparative genome analysis indicated that compared with BH15-2, BH16-24 genome had a large-scale genomic inversion fragment, at the location from 502,513 bp to 1,788,813 bp, resulting in many of virulence and resistance genes differentially expression. In addition, there was a 46 kb length, intact phage sequence in BH15-2 genome, which was absent in BH16-24.

CONCLUSION

Comparative genomic studies of BH15-2 and BH16-24 showed that the main difference is a 1.28 Mbp inversion fragment. The inversion fragment may lead to abnormal expression of drug resistant and virulence genes, which is believed to be the main reason for the multiple resistance and weakened virulence of BH16-24. Our study revealed the potential mechanisms in underlying the differences of multidrug resistance and virulence among different genotypes of S.iniae.

Host Cell Oxidative Stress Promotes Intracellular Fluoroquinolone Persisters of Streptococcus pneumoniae

Bacterial persisters represent a small subpopulation that tolerates high antibiotic concentrations without acquiring heritable resistance, and it may be generated by environmental factors. Here, we report the first antibiotic persistence mechanism in Streptococcus pneumoniae, which is induced by oxidative stress conditions and allows the pneumococcus to survive in the presence of fluoroquinolones. We demonstrated that fluoroquinolone persistence is prompted by both the impact of growth arrest and the oxidative stress response induced by H2O2 in bacterial cells. This process protected pneumococci against the deleterious effects of high ROS levels induced by fluoroquinolones. Importantly, S. pneumoniae develops persistence during infection, and is dependent on the oxidative stress status of the host cells, indicating that its transient intracellular life contributes to this mechanism. Furthermore, our findings suggest persistence may influence the outcome of antibiotic therapy and be part of a multistep mechanism in the evolution of fluoroquinolone resistance. IMPORTANCE In S. pneumoniae, different mechanisms that counteract antibiotic effects have been described, such as vancomycin tolerance, heteroresistance to penicillin and fluoroquinolone resistance, which critically affect the therapeutic efficacy. Antibiotic persistence is a type of antibiotic tolerance that allows a bacterial subpopulation to survive lethal antimicrobial concentrations. In this work, we used a host-cell infection model to reveal fluoroquinolone persistence in S. pneumoniae. This mechanism is induced by oxidative stress that the pneumococcus must overcome to survive in host cells. Many fluoroquinolones, such as levofloxacin and moxifloxacin, have a broad spectrum of activity against bacterial pathogens of community-acquired pneumonia, and they are used to treat pneumococcal diseases. However, the emergence of fluoroquinolone-resistant strains complicates antibiotic treatment of invasive infections. Consequently, antibiotic persistence in S. pneumoniae is clinically relevant due to prolonged exposure to fluoroquinolones likely favors the acquisition of mutations that generate antibiotic resistance in persisters. In addition, this work contributes to the knowledge of antibiotic persistence mechanisms in bacteria.

Allele-specific collateral and fitness effects determine the dynamics of fluoroquinolone resistance evolution

A promising strategy to overcome the evolution of antibiotic-resistant bacteria is to use collateral sensitivity-informed antibiotic treatments that rely on cycling or mixing of antibiotics, such that that resistance toward one antibiotic confers increased sensitivity to the other. Here, focusing on multistep fluoroquinolone resistance in Streptococcus pneumoniae, we show that antibiotic resistance induces diverse collateral responses whose magnitude and direction are determined by allelic identity. Using mathematical simulations, we show that these effects can be exploited via combination treatment regimens to suppress the de novo emergence of resistance during treatment.

Collateral sensitivity (CS), which arises when resistance to one antibiotic increases sensitivity toward other antibiotics, offers treatment opportunities to constrain or reverse the evolution of antibiotic resistance. The applicability of CS-informed treatments remains uncertain, in part because we lack an understanding of the generality of CS effects for different resistance mutations, singly or in combination. Here, we address this issue in the gram-positive pathogen Streptococcus pneumoniae by measuring collateral and fitness effects of clinically relevant gyrA and parC alleles and their combinations that confer resistance to fluoroquinolones. We integrated these results in a mathematical model that allowed us to evaluate how different in silico combination treatments impact the dynamics of resistance evolution. We identified common and conserved CS effects of different gyrA and parC alleles; however, the spectrum of collateral effects was unique for each allele or allelic pair. This indicated that allelic identity can impact the evolutionary dynamics of resistance evolution during monotreatment and combination treatment. Our model simulations, which included the experimentally derived antibiotic susceptibilities and fitness effects, and antibiotic-specific pharmacodynamics revealed that both collateral and fitness effects impact the population dynamics of resistance evolution. Overall, we provide evidence that allelic identity and interactions can have a pronounced impact on collateral effects to different antibiotics and suggest that these need to be considered in models examining CS-based therapies.

Designing cyclic competence-stimulating peptide (CSP) analogs with pan-group quorum-sensing inhibition activity in Streptococcus pneumoniae

Streptococcus pneumoniae is an opportunistic human pathogen that utilizes the competence regulon, a quorum-sensing circuitry, to acquire antibiotic resistance genes and initiate its attack on the human host. Interception of the competence regulon can therefore be utilized to study S. pneumoniae cell-cell communication and behavioral changes, as well as attenuate S. pneumoniae infectivity. Herein we report the design and synthesis of cyclic dominant negative competence-stimulating peptide (dnCSP) analogs capable of intercepting the competence regulon in both S. pneumoniae specificity groups with activities at the low nanomolar range. Structural analysis of lead analogs provided important insights as to the molecular mechanism that drives CSP receptor binding and revealed that the pan-group cyclic CSPs exhibit a chimeric hydrophobic patch conformation that resembles the hydrophobic patches required for both ComD1 and ComD2 binding. Moreover, the lead cyclic dnCSP, CSP1-E1A-cyc(Dap6E10), was found to possess superior pharmacological properties, including improved resistance to enzymatic degradation, while remaining nontoxic. Lastly, CSP1-E1A-cyc(Dap6E10) was capable of attenuating mouse mortality during acute pneumonia caused by both group 1 and group 2 S. pneumoniae strains. This cyclic pan-group dnCSP is therefore a promising drug lead scaffold against S. pneumoniae infections that could be administered individually or utilized in combination therapy to augment the effects of current antimicrobial agents.

The Epidemiology and Biostatistics of Pneumococcus

Invasive infections caused by Streptococcus pneumoniae, such as pneumonia, meningitis, and bacteremia, are a major cause of morbidity and mortality in young children and older adults worldwide. The introduction of pneumococcal conjugate vaccines into national childhood immunization programs has led to large and sustained reductions in the incidence of invasive pneumococcal disease across all age groups. Here we describe the epidemiology and biostatistics of pneumococcal disease as well as the impact of vaccination on the burden of pneumococcal disease globally.

Sublethal β-lactam antibiotics induce PhpP phosphatase expression and StkP kinase phosphorylation in PBP-independent β-lactam antibiotic resistance of Streptococcus pneumoniae

StkP and PhpP of Streptococcus pneumoniae have been confirmed to compose a signaling couple, in which the former is a serine/threonine (Ser/Thr) kinase while the latter was annotated as a phosphotase. StkP has been reported to be involved in penicillin-binding protein (PBP)-independent penicillin resistance of S. pneumoniae. However, the enzymatic characterization of PhpP and the role of PhpP in StkP-PhpP couple remain poorly understood. Here we showed that 1/4 minimal inhibitory concentration (MIC) of penicillin (PCN) or cefotaxime (CTX), the representatives of β-lactam antibiotics, could induce the expression of stkP and phpP genes and phosphorylation of StkP in PCN/CTX-sensitive strain ATCC6306 and three isolates of S. pneumoniae (MICs: 0.02-0.5 μg/ml). The product of phpP gene hydrolyzed PP2C type Ser/Thr phosphotase-specific RRA (pT)VA phosphopeptide substrate with the Km and Kcat values of 277.35 μmoL/L and 0.71 S^-1, and the hydrolytic activity was blocked by sodium fluoride, a PP2C type Ser/Thr phosphatase inhibitor. The phosphorylation levels of StkP in the four phpP gene-knockout (ΔphpP) mutants were significantly higher than that in the wild-type strains. In particular, the MICs of PCN and CTX against the ΔphpP mutants were significantly elevated as 4-16 μg/ml. Therefore, our findings confirmed that sublethal PCN and CTX act as environmental inducers to cause the increase of phpP and stkP gene expression and StkP phosphorylation. PhpP is a PP2C type Ser/Thr protein phosphatase responsible for dephosphorylation of StkP. Knockout of the phpP gene results in a high level of StkP phosphorylation and PBP-independent PCN/CTX resistance of S. pneumoniae.

Guidelines for the Antibiotic Use in Adults with Acute Upper Respiratory Tract Infections

These guidelines were developed as part of the 2016 Policy Research Servicing Project by the Korea Centers for Disease Control and Prevention. A multidisciplinary approach was taken to formulate this guideline to provide practical information about the diagnosis and treatment of adults with acute upper respiratory tract infection, with the ultimate aim to promote the appropriate use of antibiotics. The formulation of this guideline was based on a systematic literature review and analysis of the latest research findings to facilitate evidence-based practice, and focused on key questions to help clinicians obtain solutions to clinical questions that may arise during the care of a patient. These guidelines mainly cover the subjects on the assessment of antibiotic indications and appropriate selection of antibiotics for adult patients with acute pharyngotonsillitis or acute sinusitis.

Refractory status epilepticus due to pneumococcal meningitis in an infant with congenital immunodeficiency

Pneumococcal meningitis remains a life-threatening infection, with varied presentations. A 3 month-old-baby with pneumococcal meningitis presented with clusters of seizures evolving into refractory status epilepticus despite standard antibiotic and aggressive anticonvulsant therapy. Progressive illness despite antibiotic initially suggested possible antibiotic resistance and resulted in addition of another antibiotic. Nonresponse to standard treatment and previous history of abscess in the back of neck pointed to some underlying congenital immunodeficiency. Further evaluation showed a deficiency of complement factor C3. This case underlines the need to consider underlying immunodeficiency in cases of refractory status epilepticus due to bacterial meningitis. Gram-staining of cerebrospinal fluid sample showing plenty of Gram-positive bacteria and comparatively fewer pus cells is a clue regarding some underlying immunodeficiency.

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.

Molecular characteristics of penicillin-binding protein 2b, 2x and 1a sequences in Streptococcus pneumoniae isolates causing invasive diseases among children in Northeast China

Streptococcus pneumoniae is one of the common pathogens causing severe invasive infections in children. This study aimed to investigate the serotype distribution and variations of penicillin-binding proteins (PBPs) 2b, 2x and 1a in S. pneumoniae isolates causing invasive diseases in Northeast China. A total of 256 strains were isolated from children with invasive pneumococcal disease (IPD) from January 2000 to October 2014. All strains were serotyped and determined for antibiotic resistance. The amplicons of penicillin-binding domains in pbp1a, pbp2b and pbp2x genes were sequenced for variation identification. The most prevalent serotypes of isolates in IPD children were 19A, 14, 19F, 23F and 6B. 19A and 19F were the most frequent serotypes of penicillin-resistant S. pneumoniae (PRSP), which present with high resistance to amoxicillin, cefotaxime, ceftriaxone and meropenem. The numbers of amino acid substitutions of penicillin-non-susceptible S. pneumoniae (PNSP) isolates were higher than those of penicillin-sensitive S. pneumoniae isolates in all the PBP genes (p < 0.01). The patterns of amino acid mutation in PBP2b, PBP2x and PBP1a were unique and different from those of other countries. All of the serotype 19A and 19F PRSP isolates carried 25 amino acid mutations, including Ala618 → Gly between positions 560 and 675 in PBP2b and Thr338 → Ala substitutions in PBP2x. The amino acid alterations in PBP2b, PBP2x and PBP1a from S. pneumoniae were closely associated with resistance to β-lactam antibiotics. This study provides new data for further monitoring of genetic changes related to the emergence and spread of resistance to β-lactam antibiotics in China.

Acute otitis media

Acute otitis media (AOM) is a common problem facing general practitioners, paediatricians and otolaryngologists. This article reviews the aetiopathogenesis, epidemiology, presentation, natural history, complications and management of AOM. The literature was reviewed by using the PubMed search engine and entering a combination of terms including 'AOM', 'epidemiology' and 'management'. Relevant articles were identified and examined for content. What is the take-home message? AOM is a very common problem affecting the majority of children at least once and places a large burden on health care systems throughout the world. Although symptomatic relief is often enough for most children, more severe and protracted cases require treatment with antibiotics, especially in younger children.

Safety, tolerability and immunogenicity of 15-valent pneumococcal conjugate vaccine in toddlers previously vaccinated with 7-valent pneumococcal conjugate vaccine

BACKGROUND

Widespread use of 7-valent pneumococcal conjugate vaccine (PCV7) in children has led to significant reduction in pneumococcal disease in children and adults. However, diseases caused by serotypes not included in PCV7 have increased. A 15-valent pneumococcal conjugate vaccine (PCV15) containing serotypes in PCV7 and 8 additional serotypes (1, 3, 5, 6A, 7F, 19A, 22F, 33F) was developed and evaluated in toddlers 12 to 15 months of age.

METHODS

Ninety toddlers who completed an infant series with PCV7 received a single dose of either aluminum-adjuvanted PCV15, nonadjuvanted PCV15, or PCV7. Injection-site and systemic adverse events (AEs) were collected for 14 days postvaccination and serious AEs (SAEs) were collected for 30 days postvaccination. Solicited AEs included local (pain/tenderness, swelling, nodule and redness) and systemic (fatigue, arthralgia and myalgia) AEs. Serotype-specific immunoglobulin G (IgG) and opsonophagocytic (OPA) responses were measured immediately prior and 30 days postvaccination.

RESULTS

Incidences of local and systemic AEs were comparable across vaccine groups. The majority of reported events, regardless of vaccine received, were transient and of mild to moderate intensity. No clinically significant differences were observed when comparing duration and severity of AEs. No vaccine-related SAEs or discontinuations from the study due to AEs were reported. Pneumococcal IgG concentrations and OPA titers increased postvaccination, with appreciable fold rises for all serotypes. Antibody levels were comparable between both PCV15 formulations and generally comparable to PCV7 for the shared serotypes.

CONCLUSION

Both formulations of PCV15 display acceptable safety profiles and induce IgG and OPA responses to all vaccine serotypes.

Otitis media: an update on current pharmacotherapy and future perspectives

INTRODUCTION

Acute otitis media (AOM) is the most common childhood bacterial infection and also the leading cause of conductive hearing loss in children. Currently, there is an urgent need for developing novel therapeutic agents for treating AOM.

AREAS COVERED

Structured search of current literature. PubMed was searched for published literature in areas of pharmacotherapeutics, preventive therapies and complementary treatments for OM. The intent of this review is to provide a comprehensive evaluation of therapeutics for AOM, including preventive modalities and complementary medicine.

EXPERT OPINION

the management of AOM in young children is still evolving and depends on patterns of bacterial colonization and antimicrobial resistance in the community. The introduction of vaccinations against potential respiratory tract pathogens has altered the frequency of recovery of pathogens causing ear infections in children. Even though not all patients require antimicrobial therapy to overcome their infection, these agents improve symptoms faster and lead to fewer treatment failures. Further studies are warranted to evaluate which patients would best benefit from antimicrobial therapy.

Role of pneumococcal vaccination in prevention of pneumococcal disease among adults in Singapore

The burden of disease associated with Streptococcus pneumoniae infection in adults can be considerable but is largely preventable through routine vaccination. Although substantial progress has been made with the recent licensure of the new vaccines for prevention of pneumonia in adults, vaccine uptake rates need to be improved significantly to tackle adult pneumococcal disease effectively. Increased education regarding pneumococcal disease and improved vaccine availability may contribute to a reduction in pneumococcal disease through increased vaccination rates. The increase in the elderly population in Singapore as well as globally makes intervention in reducing pneumococcal disease an important priority. Globally, all adult vaccines remain underused and family physicians give little priority to pneumococcal vaccination for adults in daily practice. Family physicians are specialists in preventive care and can be leaders in ensuring that adult patients get the full benefit of protection against vaccine-preventable diseases. They can play a key role in the immunization delivery of new and routine vaccines by educating the public on the risks and benefits associated with vaccines. Local recommendations by advisory groups on vaccination in adults will also help to tackle vaccine preventable diseases in adults.

Clinical practice guideline for the diagnosis and management of acute bacterial sinusitis in children aged 1 to 18 years

OBJECTIVE

To update the American Academy of Pediatrics clinical practice guideline regarding the diagnosis and management of acute bacterial sinusitis in children and adolescents.

METHODS

Analysis of the medical literature published since the last version of the guideline (2001).

RESULTS

The diagnosis of acute bacterial sinusitis is made when a child with an acute upper respiratory tract infection (URI) presents with (1) persistent illness (nasal discharge [of any quality] or daytime cough or both lasting more than 10 days without improvement), (2) a worsening course (worsening or new onset of nasal discharge, daytime cough, or fever after initial improvement), or (3) severe onset (concurrent fever[temperature ≥39°C/102.2°F] and purulent nasal discharge for at least 3 consecutive days). Clinicians should not obtain imaging studies of any kind to distinguish acute bacterial sinusitis from viral URI, because they do not contribute to the diagnosis; however, a contrast-enhanced computed tomography scan of the paranasal sinuses should be obtained whenever a child is suspected of having orbital or central nervous system complications. The clinician should prescribe antibiotic therapy for acute bacterial sinusitis in children with severe onset or worsening course. The clinician should either prescribe antibiotic therapy or offer additional observation for 3 days to children with persistent illness. Amoxicillin with or without clavulanate is the firstline treatment of acute bacterial sinusitis. Clinicians should reassess initial management if there is either a caregiver report of worsening(progression of initial signs/symptoms or appearance of new signs/symptoms) or failure to improve within 72 hours of initial management.If the diagnosis of acute bacterial sinusitis is confirmed in a child with worsening symptoms or failure to improve, then clinicians may change the antibiotic therapy for the child initially managed with antibiotic or initiate antibiotic treatment of the child initially managed with observation.

CONCLUSIONS

Changes in this revision include the addition of a clinical presentation designated as “worsening course,” an option to treat immediately or observe children with persistent symptoms for 3 days before treating, and a review of evidence indicating that imaging is not necessary in children with uncomplicated acute bacterial sinusitis.

The changing epidemiology of childhood pneumococcal disease in Korea

The wide use of antimicrobial agents and 7-valent pneumococcal conjugate vaccine (PCV7) has led to major changes in the epidemiology of childhood pneumococcal diseases. In Korea, data on the population-based incidence of childhood invasive pneumococcal diseases (IPD) are not available; however, institution-based surveillance data suggest a substantial burden of childhood IPD. Following the introduction of the PCV7 in Korea in 2003, the proportion of IPD caused by vaccine-type pneumococci has decreased, while non-PCV7 serotypes, especially serotypes 19A and 6A, whose proportions had been increasing before the introduction of the vaccine, became predominant among childhood IPD isolates. This article reviews the overall impact of PCV7 utilization and summarizes the results obtained so far. Continuous monitoring and gathering of scientific evidence for the epidemiological transition of pneumococcal carriage and IPD will be important for the management of pneumococcal infections in Korea.

Acute sinusitis in children

Acute rhinosinusitis is a common illness in children. Viral upper respiratory tract infection is the most common presentation of rhinosinusitis. Most children resolve the infection spontaneously and only a small proportion develops a secondary bacterial infection. The proper choice of antibiotic therapy depends on the likely infecting pathogens, bacterial antibiotic resistance, and pharmacologic profiles of antibiotics. Amoxicillin-clavulanate is currently recommended as the empiric treatment in those requiring antimicrobial therapy. Isolation of the causative agents should be considered in those who failed the initial treatment. In addition to antibiotics, adjuvant therapies and surgery may be used in the management of acute bacterial rhinosinusitis.

The diagnosis and management of acute otitis media

This evidence-based clinical practice guideline is a revision of the 2004 acute otitis media (AOM) guideline from the American Academy of Pediatrics (AAP) and American Academy of Family Physicians. It provides recommendations to primary care clinicians for the management of children from 6 months through 12 years of age with uncomplicated AOM. In 2009, the AAP convened a committee composed of primary care physicians and experts in the fields of pediatrics, family practice, otolaryngology, epidemiology, infectious disease, emergency medicine, and guideline methodology. The subcommittee partnered with the Agency for Healthcare Research and Quality and the Southern California Evidence-Based Practice Center to develop a comprehensive review of the new literature related to AOM since the initial evidence report of 2000. The resulting evidence report and other sources of data were used to formulate the practice guideline recommendations. The focus of this practice guideline is the appropriate diagnosis and initial treatment of a child presenting with AOM. The guideline provides a specific, stringent definition of AOM. It addresses pain management, initial observation versus antibiotic treatment, appropriate choices of antibiotic agents, and preventive measures. It also addresses recurrent AOM, which was not included in the 2004 guideline. Decisions were made on the basis of a systematic grading of the quality of evidence and benefit-harm relationships. The practice guideline underwent comprehensive peer review before formal approval by the AAP. This clinical practice guideline is not intended as a sole source of guidance in the management of children with AOM. Rather, it is intended to assist primary care clinicians by providing a framework for clinical decision-making. It is not intended to replace clinical judgment or establish a protocol for all children with this condition. These recommendations may not provide the only appropriate approach to the management of this problem.

Saturated alanine scanning mutagenesis of the pneumococcus competence stimulating peptide identifies analogs that inhibit genetic transformation

Antibiotic resistance is a major challenge to modern medicine. Intraspecies and interspecies dissemination of antibiotic resistance genes among bacteria can occur through horizontal gene transfer. Competence-mediated gene transfer has been reported to contribute to the spread of antibiotic resistance genes in Streptococcus pneumoniae. Induction of the competence regulon is mediated by a 17-amino acid peptide pheromone called the competence stimulating peptide (CSP). Thus, synthetic analogs that competitively inhibit CSPs may reduce horizontal gene transfer. We performed saturated alanine scanning mutagenesis and other amino acid substitutions on CSP1 to screen for analogs that disable genetic transformation in S. pneumoniae. Substitution of the glutamate residue at the first position created analogs that could competitively inhibit CSP1-mediated competence development in a concentration-dependent manner. Additional substitutions of the negatively-charged glutamate residue with amino acids of different charge, acidity and hydrophobicity, as well as enantiomeric D-glutamate, generated analogs that efficiently outcompeted CSP1, suggesting the importance of negative charge and enantiomericity of the first glutamate residue for the function of CSP1. Collectively, these results indicate that glutamate residue at the first position is important for the ability of CSP1 to induce ComD, but is dispensable for the peptide to bind the receptor. Furthermore, these results demonstrate the potential applicability of competitive CSP analogs to control horizontal transfer of antibiotic resistance genes in S. pneumoniae.

Streptococcal pharyngitis: a prospective study of compliance and complications

Background. Uncertainty exists concerning the necessity of 10-day antibiotic treatment of group A beta hemolytic streptococcus (GABHS) pharyngitis. Objective. To assess the incidence of GABHS recurrence and suppurative and nonsuppurative complications in relation to compliance. Methods. (Design). Prospective cohort observational study. (Subjects). 2,000 children aged 6 months to 18 years with sore throat and positive GABHS culture. (Main Outcome Measures). Recurrence of symptomatic culture positive GABHS pharyngitis, incidence of suppurative, and long-term, regional, nonsuppurative complications of GABHS pharyngitis, over a ten year period. Results. 213 (11%) of the children received no treatment. Most children received antibiotics for only 4-6 days (in correlation with the duration of fever, which in most cases lasted up to 3 days). Three hundred and six (15.3%) children had clinically diagnosed recurrent tonsillopharyngitis; 236 (12.3%) had positive GABHS findings within 10 to 14 days and thirty-four (1.7%) within 21-30 days after the index positive GABHS culture. The remaining 1.3% had no positive culture despite the clinical findings. Almost all recurrences [236 (11.6%)] occurred within 14 days and 156 (7.6%) in the fully treated group. The presence of fever during the first 3 days of the disease was the most significant predictor for recurrence. Other predictors were the age younger than 6 years and the presence of cervical lymphadenitis. No increase in the incidence of nonsuppurative or suppurative complications was noted during the 10-year follow-up period, compared to the past incidence of those complications in Israel. Conclusions. Our data suggests that the majority of children discontinue antibiotics for GABHS tonsillopharyngitis a day or two after the fever subsides. The incidence of complications in our study was not affected by this poor compliance.

IDSA Clinical Practice Guideline for Acute Bacterial Rhinosinusitis in Children and Adults

Evidence-based guidelines for the diagnosis and initial management of suspected acute bacterial rhinosinusitis in adults and children were prepared by a multidisciplinary expert panel of the Infectious Diseases Society of America comprising clinicians and investigators representing internal medicine, pediatrics, emergency medicine, otolaryngology, public health, epidemiology, and adult and pediatric infectious disease specialties. Recommendations for diagnosis, laboratory investigation, and empiric antimicrobial and adjunctive therapy were developed.

Inhibition of competence development, horizontal gene transfer and virulence in Streptococcus pneumoniae by a modified competence stimulating peptide

Competence stimulating peptide (CSP) is a 17-amino acid peptide pheromone secreted by Streptococcus pneumoniae. Upon binding of CSP to its membrane-associated receptor kinase ComD, a cascade of signaling events is initiated, leading to activation of the competence regulon by the response regulator ComE. Genes encoding proteins that are involved in DNA uptake and transformation, as well as virulence, are upregulated. Previous studies have shown that disruption of key components in the competence regulon inhibits DNA transformation and attenuates virulence. Thus, synthetic analogues that competitively inhibit CSPs may serve as attractive drugs to control pneumococcal infection and to reduce horizontal gene transfer during infection. We performed amino acid substitutions on conserved amino acid residues of CSP1 in an effort to disable DNA transformation and to attenuate the virulence of S. pneumoniae. One of the mutated peptides, CSP1-E1A, inhibited development of competence in DNA transformation by outcompeting CSP1 in time and concentration-dependent manners. CSP1-E1A reduced the expression of pneumococcal virulence factors choline binding protein D (CbpD) and autolysin A (LytA) in vitro, and significantly reduced mouse mortality after lung infection. Furthermore, CSP1-E1A attenuated the acquisition of an antibiotic resistance gene and a capsule gene in vivo. Finally, we demonstrated that the strategy of using a peptide inhibitor is applicable to other CSP subtype, including CSP2. CSP1-E1A and CSP2-E1A were able to cross inhibit the induction of competence and DNA transformation in pneumococcal strains with incompatible ComD subtypes. These results demonstrate the applicability of generating competitive analogues of CSPs as drugs to control horizontal transfer of antibiotic resistance and virulence genes, and to attenuate virulence during infection by S. pneumoniae.

Streptococcus pneumoniae is a major cause of pneumonia, ear infection and meningitis. Antibiotic resistance among S. pneumoniae isolates is increasingly a major clinical problem. The acquisition of antibiotic resistance genes in S. pneumoniae is controlled by a peptide pheromone called competence-stimulating peptide (CSP). CSP binds to a receptor called ComD, which in turn activates its cognate transcription factor ComE to initiate DNA uptake and integration into the S. pneumoniae genome. CSP-ComD/E also regulates the expression of virulence factors required for infection. In this study, multiple synthetic analogues of CSP pheromone were examined for their ability to inhibit acquisition of exogenous DNA, and to control infection by S. pneumoniae in mice. Two of these analogues, CSP1-E1A and CSP2-E1A, competitively inhibit the ability of S. pneumoniae to acquire the streptomycin resistance rpsL gene and the capsule gene cap3A during mouse models of acute pneumonia and bacteremia. CSP1-E1A also reduces mouse mortality during lung infection by S. pneumoniae. This is the first demonstration of the use of CSP analogues to attenuate virulence and to inhibit acquisition of an antibiotic resistance gene in S. pneumoniae. Because the CSP-ComD/E system is conserved among many pathogenic bacteria, CSP analogues may be applicable to reduce the spread of antibiotic resistance genes and to treat infections.

What are the properties that make an antibiotic acceptable for therapy of community-acquired pneumonia?

The factors associated with identifying an appropriate dose and schedule of an antimicrobial agent for treatment of hospitalized, seriously ill patients with pneumonia are straightforward. Information is required about the potency of the agent for typical pathogens likely to be encountered with pneumonia. It is helpful to understand the utility of the agent against pathogens that express resistance to older antimicrobial agents. The agent must be able to gain access to the site of infection at the dose and schedule chosen and at concentrations high enough to attain microbiologically effective targets [e.g. 1 or 2 log(10) (cfu/g) bacterial cell kill, accounting for between-patient variability]. Finally, therapeutic concentrations should be attained quickly at the primary site of infection to optimize clinical outcomes. When considering all of these factors, it is expected that ceftaroline fosamil will be a valuable addition to the therapeutic armamentarium for management of community-acquired pneumonia.

Changing needs of community-acquired pneumonia

Community-acquired pneumonia (CAP) is a serious condition associated with significant morbidity and potential long-term mortality. Although the majority of patients with CAP are treated as outpatients, the greatest proportion of pneumonia-related mortality and healthcare expenditure occurs among the patients who are hospitalized. There has been considerable interest in determining risk factors and severity criteria assessments to assist with site-of-care decisions. For both inpatients and outpatients, the most common pathogens associated with CAP include Streptococcus pneumoniae, Haemophilus influenzae, group A streptococci and Moraxella catarrhalis. Atypical pathogens, Gram-negative bacilli, methicillin-resistant Staphylococcus aureus (MRSA) and viruses are also recognized aetiological agents of CAP. Despite the availability of antimicrobial therapies, the recent emergence of drug-resistant pneumococcal and staphylococcal isolates has limited the effectiveness of currently available agents. Because early and rapid initiation of empirical antimicrobial treatment is critical for achieving a favourable outcome in CAP, newer agents with activity against drug-resistant strains of S. pneumoniae and MRSA are needed for the management of patients with CAP.

Compensatory evolution of pbp mutations restores the fitness cost imposed by β-lactam resistance in Streptococcus pneumoniae

The prevalence of antibiotic resistance genes in pathogenic bacteria is a major challenge to treating many infectious diseases. The spread of these genes is driven by the strong selection imposed by the use of antibacterial drugs. However, in the absence of drug selection, antibiotic resistance genes impose a fitness cost, which can be ameliorated by compensatory mutations. In Streptococcus pneumoniae, β-lactam resistance is caused by mutations in three penicillin-binding proteins, PBP1a, PBP2x, and PBP2b, all of which are implicated in cell wall synthesis and the cell division cycle. We found that the fitness cost and cell division defects conferred by pbp2b mutations (as determined by fitness competitive assays in vitro and in vivo and fluorescence microscopy) were fully compensated by the acquisition of pbp2x and pbp1a mutations, apparently by means of an increased stability and a consequent mislocalization of these protein mutants. Thus, these compensatory combinations of pbp mutant alleles resulted in an increase in the level and spectrum of β-lactam resistance. This report describes a direct correlation between antibiotic resistance increase and fitness cost compensation, both caused by the same gene mutations acquired by horizontal transfer. The clinical origin of the pbp mutations suggests that this intergenic compensatory process is involved in the persistence of β-lactam resistance among circulating strains. We propose that this compensatory mechanism is relevant for β-lactam resistance evolution in Streptococcus pneumoniae.

Evolving trends in Streptococcus pneumoniae resistance: implications for therapy of community-acquired bacterial pneumonia

Pneumonia is a major infectious disease associated with significant morbidity, mortality and utilisation of healthcare resources. Streptococcus pneumoniae is the predominant pathogen in community-acquired pneumonia (CAP), accounting for 20-60% of bacterial cases. Emergence of multidrug-resistant S. pneumoniae has become a significant problem in the management of CAP. Although pneumococcal conjugate vaccine usage in children has led to significant decreases in morbidity and mortality due to S. pneumoniae in all age groups, disease management has been further complicated by the unexpected increase in resistant serotypes, such as 19A, in some regions. Until rapid and accurate diagnostic tests become available, initial treatment of CAP will remain empirical. Thus, selection of appropriate antimicrobial therapy for CAP must be based on prediction of the most likely pathogens and their local antimicrobial susceptibility patterns. This article reviews information on antimicrobial resistance patterns amongst S. pneumoniae and implications for managing CAP.

Methicillin-resistant Staphylococcus aureus in community-acquired and health care-associated pneumonia: incidence, diagnosis, and treatment options

Pneumonia is one of the leading causes of death in the United States. As health care has expanded into community settings, including outpatient clinics, long-term care facilities, and dialysis centers, a new category of pneumonia-health care-associated pneumonia (HCAP)-has been defined. Bacterial resistance to antibiotics is rising among community-acquired infections, and the emergence of community-associated methicillin-resistant Staphylococcus aureus (MRSA) infections, particularly the severe form of necrotizing pneumonia mediated by USA 300 in young and healthy individuals, warrants attention. Although Streptococcus pneumoniae remains the most prevalent causative pathogen in community-acquired pneumonia (CAP), S aureus infections are increasingly being reported in community settings, especially in patients with HCAP. Recent surveillance of community-dwelling adults with pneumonia admitted to United States hospitals has demonstrated a steady increase in S aureus isolates. Thus, MRSA should be considered in severe pneumonia associated with influenza-like symptoms, particularly when accompanied by hemoptysis or leukopenia. However, MRSA pneumonia also can develop in the absence of preceding influenza-like illness. Effective empiric therapy for pneumonia, whether CAP or HCAP, mandates selection of an agent with coverage against all likely pathogens. Failure to provide adequate initial antimicrobial coverage has been associated with an increased risk of death. The spread of resistant pathogens in the community challenges currently available antimicrobial agents for effective treatment of MRSA-mediated pneumonia. Approval of newer antimicrobials with MRSA activity may provide additional options for the management of pneumonia. This article provides a review of the role of MRSA as a causative pathogen in CAP and HCAP.

Microbiology of the middle ear fluid in Costa Rican children between 2002 and 2007

BACKGROUND

Because the microbiology and susceptibility patterns of middle ear fluid pathogens in children with otitis media change over time, an active surveillance is recommended to establish appropriate therapeutic guidelines.

OBJECTIVE

To analyze the microbiology and susceptibility pattern of middle ear pathogens obtained from Costa Rican children with acute otitis media (AOM), recurrent otitis media (ROM) and therapeutic failure otitis media (OMTF) between 2002 and 2007.

PATIENTS AND METHODS

1108 children aged 2-92 months who participated in various otitis media clinical trials between the years 2002 and 2007.

RESULTS

Among the study population, 880 were children with AOM (61% <24 months of age), 138 were children with ROM (54% <24 months of age) and 90 were children with OMTF (67% <24 months of age). Bilateral otitis media was more frequent in children with OMTF (44%) than in children with AOM (37%) (P=0.19) and ROM (27%) (P=0.009). Presence of siblings <8 years of age was more frequently observed in children with OMTF (73%) than in children with ROM (65%) (P=0.0001) and AOM (47%) (P=0.000002). Overall Streptococcus pneumoniae (44%) was the most common pathogen isolated followed by Haemophilus influenzae (37%), Moraxella catarrhalis (11%) and Streptococcus pyogenes (4%). S. pneumoniae was the most common pathogen in AOM (44%) and ROM (47%), however, H. influenzae was the most common pathogen in OMTF (40%). Among all H. influenzae, an increase in the number of β-lactamase producing strains was observed from 5.2% in 2001 to 14% (P=0.04) in 2007 and this was associated with an increase in the use of amoxicillin. An increase in the number of M. catarrhalis was also observed, from 3% (9/350) in 2001 to 11% (71/628) (P=0.000003) in 2007. During the study period the incidence of penicillin non-susceptible S. pneumoniae was 42/211 (20%) in children with AOM; 5/35 (17%) in children with ROM and 5/17 (42%) in children with OMTF. M. catarrhalis cases increased from 8% in 2004 to 17% in 2007 (P=0.0005) and S. pyogenes decreased from 7% in 2002-2004 to 1% in 2005-2007 (P=0.001).

CONCLUSIONS

In Costa Rica, S. pneumoniae remains the most common pathogen in children with AOM and ROM whereas non-typable H. influenzae remains the most common pathogen in children with OMTF. A significant increase in the number of β-lactamase positive H. influenzae and M. catarrhalis has been observed in recent years.

Lost in transcription--inhibition of RNA polymerase

Form and function: The natural product myxopyronin A provides the key to understanding the inhibition of bacterial RNA polymerase and should spark new ideas for the design of new antibiotics against tuberculosis and other infectious diseases.