Emergence of multidrug-resistant Streptococcus pneumoniae: report from the SENTRY Antimicrobial Surveillance Program (1999–2003)

Laboratory surveillance of antimicrobial resistance and multidrug resistance among Streptococcus pneumoniae isolated in the Kinki region of Japan, 2001-2015

The 7-valent pneumococcal conjugate vaccine (PCV7) was introduced among children in Japan in 2010. There are no long-term multicenter surveillance studies of antimicrobial resistance in S. pneumoniae before and after the introduction of PCV7. Therefore, we examined chronological trends in antimicrobial resistance among 4534 strains of S. pneumoniae isolated from both children and adults in the Kinki region of Japan during 2001-2015. High-level penicillin and third-generation cephalosporin resistance in S. pneumoniae increased among both children and adults during the period before the introduction of PCV7 (2001-2010). Besides penicillin and cephalosporin, pneumococcal carbapenem and macrolide resistance increased among children. The rate of resistance to these antibiotics was higher among children than among adults. The introduction of PCV7 decreased the rate of non-susceptibility to β-lactam antibiotics and the rate of multidrug resistant S. pneumoniae among children, but not among adults.

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.

Emerging resistant serotypes of invasive Streptococcus pneumoniae

BACKGROUND

Streptococcus pneumoniae is the leading cause of meningitis and sepsis. The aim of the study was to analyze the distribution, vaccine serotype coverage, and antibiotic resistance of S. pneumoniae serotypes isolated from patients with invasive diseases, after the introduction of pneumococcal 7-valent conjugated vaccine (PCV-7).

METHODS

A total of 134 isolates were collected from blood and cerebrospinal fluid specimens at Hamad Hospital during the period from 2005 to 2009. Isolate serotyping was done using the Quellung reaction. The prevaccination period was considered before 2005.

RESULTS

The most common serotypes for all age groups were 3 (12.70%), 14 (11.90%), 1 (11.90%), 19A (9.00%), 9V (5.20%), 23F (5.20%), and 19F (4.50%). Coverage rates for infant <2 years for PCV-7, the 10-valent conjugated vaccine (PCV-10), and the 13-valent conjugated vaccine (PCV-13) were 34.78%, 52.17%, and 78.26%, respectively. Coverage rates of these vaccines were 50%, 67.86%, and 75% for the 2-5 years age group; 27.12%, 40.68%, and 64.41% for the age group 6-64 years; and 25%, 33.33%, and 66.67% for the ≥65 years age group, respectively. The percentage of nonsusceptible isolates to penicillin, cefotaxime, and erythromycin were 43.86%, 16.66%, and 22.81%, respectively. Thirty-seven isolates (32.46%) were multidrug resistant (MDR) and belonged to serotypes 14, 19A, 19F, 23F, 1, 9V, 12F, 4, 6B, 3, and 15A. Compared to previous results before the introduction of PCV-7, there was a significant reduction in penicillin-nonsusceptable S. pneumoniae from 66.67% to 43.86%, and a slight insignificant reduction in erythromycin nonsusceptible strains from 27.60% to 22.8%, while there was a significant increase in cefotaxime nonsusceptible strains from 3.55% to 16.66%.

CONCLUSION

Invasive pneumococcal strains and the emergence of MDR serotypes is a global burden that must be addressed through multiple strategies, including vaccination, antibiotic stewardship, and continuous surveillance.

Infection biomarkers in primary care patients with acute respiratory tract infections-comparison of Procalcitonin and C-reactive protein

BACKGROUND

There is a lack of studies comparing the utility of C-reactive protein (CRP) with Procalcitonin (PCT) for the management of patients with acute respiratory tract infections (ARI) in primary care. Our aim was to study the correlation between these markers and to compare their predictive accuracy in regard to clinical outcome prediction.

METHODS

This is a secondary analysis using clinical and biomarker data of 458 primary care patients with pneumonic and non-pneumonic ARI. We used correlation statistics (spearman's rank test) and multivariable regression models to assess association of markers with adverse outcome, namely days with restricted activities and persistence of discomfort from infection at day 14.

RESULTS

At baseline, CRP and PCT did not correlate well in the overall population (r(2) = 0.16) and particularly in the subgroup of patients with non-pneumonic ARI (r(2) = 0.08). Low correlation of biomarkers were also found when comparing cut-off ranges, day seven levels or changes from baseline to day seven. High baseline levels of CRP (>100 mg/dL, regression coefficient 1.6, 95 % CI 0.5 to 2.6, sociodemographic-adjusted model) as well as PCT (>0.5ug/L regression coefficient 2.0, 95 % CI 0.0 to 4.0, sociodemographic-adjusted model) were significantly associated with larger number of days with restricted activities. There were no associations of either biomarker with persistence of discomfort at day 14.

CONCLUSIONS

CRP and PCT levels do not well correlate, but both have moderate prognostic accuracy in primary care patients with ARI to predict clinical outcomes. The low correlation between the two biomarkers calls for interventional research comparing these markers head to head in regard to their ability to guide antibiotic decisions.

TRIAL REGISTRATION

Current Controlled Trials, ISRCTN73182671.

Management of patients with respiratory infections in primary care: procalcitonin, C-reactive protein or both?

Use of inflammatory biomarkers to guide antibiotic decisions has shown promising results in the risk-adapted management of respiratory tract infections, mainly in the inpatient setting. Several observational and interventional trials have investigated the benefits of procalcitonin (PCT) and C-reactive protein (CRP) testing in primary care. Both markers have shown promising results, although CRP is an inflammatory biomarker while PCT is more specific for bacterial infections. For CRP, point-of-care testing is widely established. Recently, sensitive point-of-care testing for PCT has also become available. A high-quality trial comparing these two markers for the management of patients in primary care is currently lacking. The aim of this paper is to review the existing literature investigating the use of PCT and CRP in primary care. The authors compare their performance for guiding antibiotic stewardship and analyze the cut-off values and endpoints to put these parameters into context in a low-acuity environment.

Multidrug-Resistant Streptococcus pneumoniae Isolates from Healthy Ghanaian Preschool Children

Streptococcus pneumoniae is the cause of high mortality among children worldwide. Antimicrobial treatment and vaccination are used to control pneumococcal infections. In Ghana, data on antimicrobial resistance and the prevalence of multidrug-resistant pneumococcal clones are scarce; hence, the aim of this study was to determine the antibiogram of S. pneumoniae recovered from Ghanaian children younger than six years of age and to what extent resistances were due to the spread of certain sero- and multilocus sequence typing (MLST) types. The susceptibility of 115 pneumococcal isolates, recovered in a previous study, to six antimicrobials was determined by disk diffusion test. Overall, 90.4% of isolates were intermediate penicillin resistant, 99.1% were trimethoprim resistant, 73.0% were tetracycline resistant, and 33.9% were sulfamethoxazole resistant. Low resistance was recorded for erythromycin (2.6%) and cefotaxime (5.2%). Overall, 72.2% of isolates were resistant to penicillin (I or R) and at least two other antimicrobials. MLST of 20 isolates showing resistance to at least four antimicrobials revealed a high diversity documented by 16 different clones, none of which had previously been associated with multidrug resistance. The resistances found may have emerged due to nonprudent antimicrobial use practices and there is a need to monitor and promote prudent antimicrobial usage in Ghana.

High prevalence of Streptococcus pneumoniae in adenoids and nasopharynx in preschool children with recurrent upper respiratory tract infections in Poland--distribution of serotypes and drug resistance patterns

BACKGROUND

Streptococcus pneumoniae is one of the major bacterial pathogens colonizing nasopharynx, and often causes upper respiratory tract infections in children. We investigated the prevalence of S. pneumoniae in nasopharynx and adenoid core in 57 children aged 2-5 years who underwent adenoidectomy for recurrent pharyngotonsillitis, and we determined serotypes and antibiotic resistance patterns of the isolated pneumococci.

MATERIAL/METHODS

The nasopharyngeal specimens obtained before adenoidectomy and the adenoids after the surgery were cultured for pneumococci. All isolates were serotyped by means of Quellung reaction. Susceptibility to antibiotics was determined according to EUCAST recommendations.

RESULTS

S. pneumoniae colonization was observed in 40 (70.2%) children. From 29 (50.9%) children S. pneumoniae was isolated both from nasopharynx and adenoid core; 2 or 3 different isolates were identified in 8 (14.0%) children. In 8 (14.0%) children pneumococci were obtained from adenoid core only and in 3 (5.3%) children from nasopharynx only. Among the isolates, 35.3% were susceptible to all tested antimicrobials and 45.1% had decreased susceptibility to penicillin. Multidrug resistance was present in 52.9% of the isolates. The most frequent was serotype 19F (25.5%). The prevalence of serotypes included in pneumococcal conjugate vaccines PCV10 and PCV13 was 51.0% and 62.7%, respectively.

CONCLUSIONS

The adenoids, like the nasopharynx, can be regarded as a reservoir of pneumococci, including multidrug resistant strains, especially in children with indication for adenoidectomy due to recurrent respiratory tract infections refractory to antibiotic therapy. Good vaccine coverage among the isolated pneumococci confirmed the validity of the routine immunization by PCVs in young children.

Pharmacotherapy for pneumococcal infections: an update

INTRODUCTION

The management of pneumococcal diseases still places a significant burden on medical and economic resources. The subjects at greatest risk of pneumococcal infections are children.

AREAS COVERED

The aim of this review is to analyse the best current therapeutic approach to pneumococcal resistance, taking into account the level of susceptibility of Streptococcus pneumoniae, and the pharmacokinetics and pharmacodynamics of different antibiotics in the various pneumococcal diseases.

EXPERT OPINION

Antibiotic treatment of a number of pneumococcal diseases remains difficult or impossible due to the presence of strains resistant to commonly used antibiotics. In children the problem is significantly more important than in adults due to the reduced number of licenced drugs for subjects in the first years of life. The new conjugate pneumococcal vaccines containing 10 (PCV10) and 13 serotypes (PCV13), which include most of the recently emerging strains, might reduce the incidence of pneumococcal infections and the circulation of resistant pathogens. However, it is likely that optimal results will only be reached after the development of effective vaccines based on conserved proteins that are capable of preventing all pneumococcal infections, regardless of the serotype of the causative organism.

Characteristics of Streptococcus pneumoniae strains colonizing upper respiratory tract of healthy preschool children in Poland

Antibiotic resistant and invasive pneumococci may spread temporally and locally in day care centers (DCCs). We examined 267 children attending four DCCs located in the same city and 70 children staying at home in three seasons (autumn, winter, and spring) to determine prevalence, serotype distribution, antibiotic resistance patterns, and transmission of pneumococcal strains colonizing upper respiratory tract of healthy children without antipneumococcal vaccination. By pheno- and genotyping, we determined clonality of pneumococci, including drug-resistant strains. The average carriage of pneumococci in three seasons was 38.2%. 73.4% and 80.4% of the isolates belonged to serotypes present in 10- and 13-valent conjugate vaccine, respectively. Among the pneumococcal strains, 33.3% were susceptible to all antimicrobial tested and 39.2% had decreased susceptibility to penicillin. Multidrug resistance was common (35.7%); 97.5% of drug-resistant isolates represented serotypes included to 10- and 13-valent conjugate vaccine. According to BOX-PCR, clonality definitely was observed only in case of serotype 14. Multivariate analysis determined DCC attendance as strongly related to pneumococcal colonization in all three seasons, but important seasonal differences were demonstrated. In children attending DCCs, we observed dynamic turnover of pneumococcal strains, especially penicillin nonsusceptible and multidrug resistant, which were mostly distributed among serotypes included to available pneumococcal conjugate vaccines.

Pneumonia in adults: the practical emergency department perspective

In those patients who are hospitalized with pneumonia, mortality is 15%. Close to 90% of deaths attributed to pneumonia are in patients older than 65 years. This article provides the emergency physician with an understanding of how to make the diagnosis, initiate early and appropriate antibiotic therapy, risk stratify patients with respect to the severity of illness, and recognize indications for admission. The discussion is balanced with an emphasis on cost-effective management, an understanding of the changing spectrum of pathogenesis, and a cognizance toward variable and less common presentations.

Changing trends in antimicrobial resistance and serotypes of Streptococcus pneumoniae isolates in Asian countries: an Asian Network for Surveillance of Resistant Pathogens (ANSORP) study

Antimicrobial resistance in Streptococcus pneumoniae remains a serious concern worldwide, particularly in Asian countries, despite the introduction of heptavalent pneumococcal conjugate vaccine (PCV7). The Asian Network for Surveillance of Resistant Pathogens (ANSORP) performed a prospective surveillance study of 2,184 S. pneumoniae isolates collected from patients with pneumococcal infections from 60 hospitals in 11 Asian countries from 2008 to 2009. Among nonmeningeal isolates, the prevalence rate of penicillin-nonsusceptible pneumococci (MIC, ≥ 4 μg/ml) was 4.6% and penicillin resistance (MIC, ≥ 8 μg/ml) was extremely rare (0.7%). Resistance to erythromycin was very prevalent in the region (72.7%); the highest rates were in China (96.4%), Taiwan (84.9%), and Vietnam (80.7%). Multidrug resistance (MDR) was observed in 59.3% of isolates from Asian countries. Major serotypes were 19F (23.5%), 23F (10.0%), 19A (8.2%), 14 (7.3%), and 6B (7.3%). Overall, 52.5% of isolates showed PCV7 serotypes, ranging from 16.1% in Philippines to 75.1% in Vietnam. Serotypes 19A (8.2%), 3 (6.2%), and 6A (4.2%) were the most prominent non-PCV7 serotypes in the Asian region. Among isolates with serotype 19A, 86.0% and 79.8% showed erythromycin resistance and MDR, respectively. The most remarkable findings about the epidemiology of S. pneumoniae in Asian countries after the introduction of PCV7 were the high prevalence of macrolide resistance and MDR and distinctive increases in serotype 19A.

Efficacy and safety of garenoxacin in the treatment of upper respiratory tract infections

OBJECTIVE

To determine the efficacy and safety of garenoxacin, a new generation of quinolone antimicrobial agent, in the treatment of adult upper respiratory tract infections.

METHODS

A total of 113 subjects were enrolled in this study. Garenoxacin (400mg/day) was administered to patients with pharyngolaryngitis, tonsillitis, and otitis media for 5-7 days and to those with sinusitis for 7-10 days. Clinical symptoms and findings were examined and quantitatively evaluated using a scoring system.

RESULTS

We found 80 to 100% improvement rate in symptoms and findings for each infection. In addition, we found significant improvement in subjective evaluations from patient questionnaires even in the early stage of the treatment. X-ray examination for acute sinusitis demonstrated that the clinical efficacy was 84% (27/32) and 76% (19/25) patients were already improved within seven days. Among the detected 84 bacteria, 75 (89%) were identified as the major pathogenic bacteria of respiratory tract infections such as Streptococcus pneumoniae (27 strains) and Haemophillus influenzae (14 strains). Garenoxacin administration completely eradicated bacteria in 53 out of 54 cases (98%). There were 8 adverse events (8.3%) including 3 diarrhea cases (3.1%).

CONCLUSION

These results suggest that garenoxacin is a highly effective and safe antimicrobial agent in the treatment of community-acquired upper respiratory infections. Additionally, garenoxacin did not induce the growth of resistant bacteria because of its strong antimicrobial activity.

High proportion of nontypeable Streptococcus pneumoniae isolates among sporadic, nonoutbreak cases of bacterial conjunctivitis

PURPOSE

Outbreaks of bacterial conjunctivitis have been linked to nontypeable strains of Streptococcus pneumoniae that lack a capsule, a key virulence factor for invasive infections. In contrast, isolates from sporadic, nonoutbreak cases of conjunctivitis were thought to be similar to invasive or nasopharyngeal isolates with respect to their capsular serotype and antibiotic resistance profile. This hypothesis was tested for 302 strains isolated during three prospective, multicenter clinical studies of bacterial conjunctivitis.

MATERIALS AND METHODS

S. pneumoniae capsular serotypes were determined by agglutination assay and confirmed by the Statens Serum Institute. The presence of the cpsAB capsule genes was determined by polymerase chain reaction (PCR). Minimum inhibitory concentrations were measured for 17 antibacterial drugs by the broth microdilution method.

RESULTS

Only 25 (8.3%) isolates reacted with the capsule-specific antisera and only one (0.3%) of these serotypes was covered by the capsule-specific PCV7 vaccine. The remaining 277 (91.7%) isolates were nontypeable, suggesting that they did not produce a capsule. PCR analysis indicated the loss of the capsule operon in 24/25 randomly selected nontypeable strains. Resistance rates were highest for azithromycin, trimethoprim, and tetracycline, while no resistance was detected for the fluoroquinolones, linezolid, and vancomycin. Antibiotic resistance rates were generally lower than those reported for invasive isolates, although some highly resistant or multidrug-resistant isolates were identified.

CONCLUSIONS

The prevalence of nontypeable strains of S. pneumoniae was higher than expected, while the number of isolates responsive to the PCV7 vaccine was surprisingly low. These results highlight the need for new vaccines that can target all S. pneumoniae strains regardless of the presence or nature of a capsule. In addition, resistance to azithromycin, erythromycin, tetracycline, and trimethoprim was greater than 10%, which may be relevant when selecting empiric treatments for ocular surface infections.

Monitoring antibiotic resistance in ocular microorganisms: results from the Antibiotic Resistance Monitoring in Ocular micRorganisms (ARMOR) 2009 surveillance study

PURPOSE

To determine the antibacterial susceptibility profile of bacterial pathogens from ocular infections against relevant aminoglycoside, β-lactam, cephalosporin, chloramphenicol, fluoroquinolone, glycopeptide, lincosamide, and macrolide antibacterial agents.

DESIGN

Laboratory investigation.

METHODS

Isolates from patients with bacterial eye infections were collected prospectively by 34 institutions across the United States and were submitted to a central laboratory for inclusion in the Antibiotic Resistance Monitoring in Ocular micRorganisms (ARMOR) study. Minimum inhibitory concentrations were determined by microbroth dilution for 200 Staphylococcus aureus (S. aureus), 144 coagulase-negative staphylococci, 75 Streptococcus pneumoniae (S. pneumoniae), 73 Haemophilus influenzae (H. influenzae), and 100 Pseudomonas aeruginosa (P. aeruginosa) isolates.

RESULTS

A large proportion of S. aureus and coagulase-negative staphylococci isolates were resistant to oxacillin/methicillin, azithromycin, or fluoroquinolones; 46.5% of S. aureus, 58.3% of coagulase-negative staphylococci, 9.0% of P. aeruginosa, and 9.3% of pneumococcal isolates were nonsusceptible to 2 or more antibacterial drug classes. Only 2.7% of H. influenzae isolates were nonsusceptible to 1 of the agents tested. Methicillin-resistant staphylococci were statistically more likely (all P < .0038) also to be resistant to fluoroquinolones, aminoglycosides, and macrolides.

CONCLUSIONS

Resistance to 1 or more antibiotics is prevalent among ocular bacterial pathogens. Current resistance trends should be considered before initiating empiric treatment of common eye infections.

Antimicrobial susceptibility of invasive and lower respiratory tract isolates of Streptococcus pneumoniae, 1998 to 2007

Previous surveys of antimicrobial resistance in Streptococcus pneumoniae have found differences depending on source of isolate (eg, higher resistance in lower respiratory tract [LRT] versus invasive isolate) and age (higher resistance in children versus adults). Susceptibility profiles in the Calgary Health Region (approximately 1.25 million population) over a 10-year period were studied. Prospective laboratory-based population surveillance for S pneumoniae disease has been conducted since 1998. Patient demographics and susceptibility testing were analyzed. In total, 2382 patient isolates were available for analysis from 1998 to 2007. Of these, 1170 isolates were invasive while 496 were LRT. Patient age distribution was: younger than five years, 14%; five to 17 years, 6%; 18 to 64 years, 56%; and 65 years or older, 24%. Mean patient age was 44.8 years and 60.0% were male. The overall incidence of nonsusceptibility was: penicillin, 8.2%; amoxicillin, 0.3%; cefuroxime, 6.2%; ceftriaxone, 1.7%; erythromycin, 8.8%; trimethoprim-sulfamethoxazole (TMP-SMX), 25.6%; clindamycin, 2.3%; and levofloxacin, 0.2%. Overall resistance rates were stable, except for increasing erythromycin resistance from 5.4% (1998) to a high of 14.2% (2004) (P=0.007). Isolates that were nonsusceptible to penicillin or TMP-SMX were more likely to be multidrug resistant (P<0.001) compared with penicillin- or TMP-SMX-susceptible isolates. Compared with invasive isolates, LRT isolates showed more resistance to penicillin, TMP-SMX, cefuroxime and erythromycin, and were more likely to be multidrug resistant. Isolates from children younger than five years of age are more likely to be multidrug resistant and resistant to erythromycin and cefotaxime. Ongoing surveillance of S pneumoniae isolates is important because resistance rates vary by source and patient age among health care regions.

The newer fluoroquinolones

Clinicians have enthusiastically used fluoroquinolones owing to their good safety profile and wide range of indications. This article reviews fluoroquinolone pharmacology, pharmacodynamic principles, and fluoroquinolone resistance mechanisms, highlighting recent trends in the epidemiology of fluoroquinolone resistance among gram-negative organisms and Streptococcus pneumonia. Important fluoroquinolone safety concerns are discussed, along with indications for the most commonly used fluoroquinolones--ciprofloxacin, levofloxacin, and moxifloxacin.

Ceftaroline fosamil: a new broad-spectrum cephalosporin

Ceftaroline fosamil, the prodrug of the active metabolite, ceftaroline, is a new, broad-spectrum cephalosporin recently approved in the USA for the treatment of acute bacterial skin and skin structure infections (ABSSSIs) and community-acquired bacterial pneumonia (CABP). Ceftaroline has potent in vitro activity against Gram-positive organisms, including methicillin-resistant Staphylococcus aureus and Streptococcus pneumoniae, as well as common Gram-negative organisms. The high affinity of ceftaroline for penicillin-binding proteins is responsible for the potent activity observed against clinically relevant pathogens. With respect to the treatment of CABP, the activity of ceftaroline against pathogens such as S. pneumoniae, S. aureus, Haemophilus influenzae and Moraxella catarrhalis demonstrates coverage across a broad range of pathogens typically encountered in clinical practice. Ceftaroline is also very active against common pathogens seen in ABSSSIs such as S. aureus (methicillin-susceptible S. aureus and methicillin-resistant S. aureus) and Streptococcus pyogenes. Ceftaroline exhibits a dose-proportional pharmacokinetic profile, similar to other renally excreted cephalosporins, and has a well-tolerated safety profile consistent with the cephalosporin class. Ceftaroline fosamil is compatible via Y-site administration with many other commonly administered parenteral drugs.

Potential role of tigecycline in the treatment of community-acquired bacterial pneumonia

Tigecycline is a member of the glycylcycline class of antimicrobials, which is structurally similar to the tetracycline class. It demonstrates potent in vitro activity against causative pathogens that are most frequently isolated in patients with community-acquired bacterial pneumonia (CABP), including (but not limited to) Streptococcus pneumoniae (both penicillin-sensitive and -resistant strains), Haemophilus influenzae and Moraxella catarrhalis (including β-lactamase-producing strains), Klebsiella pneumoniae, and ‘atypical organisms’ (namely Chlamydophila pneumoniae, Mycoplasma pneumoniae, and Legionella pneumophila). Comparative randomized clinical trials to date performed in hospitalized patients receiving tigecycline 100 mg intravenous (IV) × 1 and then 50 mg IV twice daily thereafter have demonstrated efficacy and safety comparable to the comparator agent. Major adverse effects were primarily gastrointestinal in nature. Tigecycline represents a parenteral monotherapy option in hospitalized patients with CABP (especially in patients unable to receive respiratory fluoroquinolones). However, alternate and/or additional therapies should be considered in patients with more severe forms of CABP in light of recent data of increased mortality in patients receiving tigecycline for other types of severe infection.

Emerging antibiotic resistance in ocular infections and the role of fluoroquinolones

Resistance to antibiotic agents is becoming increasingly prevalent among ocular infections. Between 19% and 60% of Streptococcus pneumoniae and Staphylococcus aureus isolates have been shown to be resistant to macrolide antibiotic agents, penicillin, and older fluoroquinolones. Although topical fluoroquinolones are considered first-line treatment of ocular infections, as much as 85% of methicillin-resistant S aureus isolates are resistant to ophthalmic fluoroquinolones, including the newer 8-methoxy fluoroquinolones, gatifloxacin and moxifloxacin. Besifloxacin, an 8-chlorofluoroquinolone, has a lower minimum inhibitory concentration against multidrug-resistant staphylococcal strains than other fluoroquinolones and less selective pressure for resistance development because of the lack of a systemic counterpart. In addition to the development of new antibacterial agents, antibiotic resistance in ocular infections may be reduced by following the same strategies used to minimize antimicrobial resistance in systemic infections.

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.

The newer fluoroquinolones

Clinicians have enthusiastically used fluoroquinolones owing to their good safety profile and wide range of indications. This article reviews fluoroquinolone pharmacology, pharmacodynamic principles, and fluoroquinolone resistance mechanisms, highlighting recent trends in the epidemiology of fluoroquinolone resistance among gram-negative organisms and Streptococcus pneumonia. Important fluoroquinolone safety concerns are discussed, along with indications for the most commonly used fluoroquinolones-ciprofloxacin, levofloxacin, and moxifloxacin.

Efficacy and safety of tigecycline versus levofloxacin for community-acquired pneumonia

BACKGROUND

Tigecycline, an expanded broad-spectrum glycylcycline, exhibits in vitro activity against many common pathogens associated with community-acquired pneumonia (CAP), as well as penetration into lung tissues that suggests effectiveness in hospitalized CAP patients. The aim of the present study was to compare the efficacy and safety of intravenous (IV) tigecycline with IV levofloxacin in hospitalized adults with CAP.

METHODS

In this prospective, double-blind, non-inferiority phase 3 trial, eligible patients with a clinical diagnosis of CAP supported by radiographic evidence were stratified by Fine Pneumonia Severity Index and randomized to tigecycline or levofloxacin for 7-14 days of therapy. Co-primary efficacy endpoints were clinical response in the clinically evaluable (CE) and clinical modified intent-to-treat (c-mITT) populations at test-of-cure (Day 10-21 post-therapy).

RESULTS

Of the 428 patients who received at least one dose of study drug, 79% had CAP of mild-moderate severity according to their Fine score. Clinical cure rates for the CE population were 88.9% for tigecycline and 85.3% for levofloxacin. Corresponding c-mITT population rates were 83.7% and 81.5%, respectively. Eradication rates for Streptococcus pneumoniae were 92% for tigecycline and 89% for levofloxacin. Nausea, vomiting, and diarrhoea were the most frequently reported adverse events. Rates of premature discontinuation of study drug or study withdrawal because of any adverse event were similar for both study drugs.

CONCLUSION

These findings suggest that IV tigecycline is non-inferior to IV levofloxacin and is generally well-tolerated in the treatment of hospitalized adults with CAP.

TRIAL REGISTRATION

NCT00081575.

Influence of antidrug antibodies on plectasin efficacy and pharmacokinetics

Plectasin is a 4.4-kDa antimicrobial peptide with the potential to be a treatment of infections caused by gram-positive bacteria. Since plectasin is a large molecule compared to conventional antibiotics, the development of antidrug antibodies (ADAs) could be anticipated. The immunogenic properties of plectasin were assessed through immunization studies. In mice treated for 5 days with one to two daily subcutaneous doses of plectasin, no antibody response was observed. If the animals were immunized again, after a rest period, low levels of antibodies developed in approximately half the animals. Additionally, mice were immunized with plectasin in Freund's incomplete adjuvant (FIA). Ninety-two percent of these mice developed ADAs after repeated immunizations, with two-thirds having high levels of antibodies. An agar diffusion bioassay showed that sera from animals immunized with plectasin did not inhibit the efficacy of the drug, while hyperimmune sera from animals in which an immune response was provoked by immunization with plectasin in FIA reduced the efficacy of plectasin at the lowest concentration tested. Studies in the murine peritonitis model showed an excellent efficacy of plectasin for the treatment of Streptococcus pneumoniae infections both in naïve animals and in animals with ADAs. No difference in bacterial counts was seen when the animals were treated with plectasin at 2.5 mg/kg of body weight, a dose below the expected therapeutic level. When animals were treated with plectasin at 0.625 mg/kg, the effect was reduced but not neutralized in animals with high levels of ADAs. No animals showed signs of hypersensitivity or injection site reactions toward plectasin, and the half-life of the compound did not vary between animals with and without antibodies.

Efficacy of pneumococcal vaccination in children younger than 24 months: a meta-analysis

CONTEXT

Pneumococcal conjugate bacterial vaccines that are able to prevent invasive disease and mucosal infections have been developed.

OBJECTIVE

A meta-analysis of published data from trials on pneumococcal conjugate vaccine was performed to determine the efficacy in reducing the incidence of invasive disease caused by Streptococcus pneumoniae, pneumonia, and acute otitis media in healthy infants younger than 24 months.

METHODS

A systematic search of the literature was conducted. Controlled clinical trials had to compare the protective efficacy of the pneumococcal conjugate vaccine in reducing the incidence of invasive disease caused by S pneumoniae, pneumonia, and acute otitis media in healthy infants with placebo or control vaccines. Information was extracted by using a standardized protocol.

RESULTS

The efficacy of pneumococcal conjugate vaccine in the reduction of invasive pneumococcal disease was 89% involving vaccine serotypes in both the intention-to-treat and per-protocol analyses and ranged from 63% to 74% for all serotypes. The efficacy to prevent acute otitis media sustained by vaccine serotypes was 55% in the intention-to-treat and 57% in the per-protocol analyses, whereas it was 29% to prevent otitis involving all serotypes in the per-protocol analysis. Finally, in the intention-to-treat and per-protocol analyses, the efficacy to prevent clinical pneumonia was 6% and 7%, respectively, whereas for the prevention of radiograph-confirmed pneumonia it was 29% and 32%, respectively.

CONCLUSIONS

The pneumococcal conjugate vaccine produces a significant effect regarding prevention of invasive pneumococcal disease. Results on prevention of otitis or pneumonia have been less striking, but considering the high burden of these diseases in infants, even a low efficacy has potential for tremendous impact on the health of infants in developing and industrialized countries.

Levofloxacin versus azithromycin on the oropharyngeal carriage and selection of antibacterial- resistant streptococci in the microflora of healthy adults

OBJECTIVE

To determine the proportion of subjects with oropharyngeal streptococci resistant to either levofloxacin or azithromycin prior to and during antibacterial exposure, and to follow temporal changes in the proportion of resistant and susceptible isolates through 6 weeks post-exposure. This randomized, open-label, single-center study is registered with ClinicalTrials.gov (identifier: NCT00821782).

RESEARCH DESIGN AND METHODS

A total of 143 healthy volunteers (levofloxacin, n = 71; azithromycin, n = 72) without antibacterial exposure in the previous 90 days received either levofloxacin 750 mg once daily for 5 days or azithromycin 500 mg once daily on day 1 and 250 mg once daily on days 2 through 5. Oropharyngeal cultures were obtained pre-exposure, at day 5, and at 2, 4, and 6 weeks post-dosing. Bacterial strains were identified and the minimum inhibitory concentrations for levofloxacin and azithromycin were determined.

RESULTS

At study entry 117 streptococci were isolated from 72 subjects randomized to azithromycin and 53 (45.3%) were azithromycin-resistant. None of the 121 streptococci isolated from 71 subjects randomized to.levofloxacin were colonized by a levofloxacin-resistant microorganism prior to dosing. At the end of dosing, the number of subjects with resistant streptococci (S. mitis, S. salivarius, S. sanguis, or alpha streptococcus species [spp.]) increased in azithromycin-exposed subjects and resistant isolates remained through 6 weeks post-dosing. In contrast, a small number of levofloxacin-resistant streptococci were observed at the end of dosing but decreased by week 2 post-dosing and continued to decrease through the 6-week evaluation period (p < 0.001 azithromycin vs. levofloxacin for S. mitis, S. salivarius, S. sanguis and alpha streptococcus spp. at week 6). Limitations of this study included the fact that, since previous antibiotic use was self-reported, genetic typing was not done. The results of this study may not be completely generalizable, because subjects in this study received study drug under directly-observed conditions, thus ensuring compliance.

CONCLUSIONS

Both antibacterial agents were well tolerated. Levofloxacin 750 mg administered for 5 days was associated with less microbial resistance than that observed with azithromycin in healthy subjects.

Combination of daptomycin plus ceftriaxone is more active than vancomycin plus ceftriaxone in experimental meningitis after addition of dexamethasone

We examined the cerebrospinal fluid penetration of daptomycin after the addition of dexamethasone and its bactericidal efficacy with and without ceftriaxone in an experimental rabbit model of pneumococcal meningitis. The combination of daptomycin with ceftriaxone was the most efficacious regimen for pneumococcal meningitis. The previous addition of dexamethasone affected the antibacterial activity of daptomycin only marginally, either as monotherapy or combined with ceftriaxone, although the penetration of daptomycin into inflamed meninges was significantly reduced from 6 to 2%. Daptomycin with ceftriaxone might be a potential candidate for the empirical therapy of bacterial meningitis, although the activity of this regimen against Listeria monocytogenes remains to be demonstrated.

Levofloxacin for the treatment of pneumonia caused by Streptococcus pneumoniae including multidrug-resistant strains: pooled analysis

OBJECTIVE

To determine the clinical and microbiologic efficacy of levofloxacin for the treatment of subjects with pneumonia caused by multidrug-resistant (MDR) Streptococcus pneumoniae (MDRSP) and non-MDRSP strains.

RESEARCH DESIGN AND METHODS

A pooled analysis was conducted using data from ten clinical studies in pneumonia: five comparative studies and five noncomparative studies conducted from 1992 to 2002. This analysis included data from levofloxacin-treated subjects with S. pneumoniae isolated at study entry. Susceptibility of S. pneumoniae isolated from subjects at study entry was determined against representative agents from five antimicrobial classes: tetracyclines, sulfonamides, second-generation cephalosporins, penicillins, and macrolides. Isolates were classified as MDRSP (based on resistance to two or more antimicrobial classes) or non-MDRSP (intermediate resistance or susceptible to all classes or resistant to 1 antimicrobial class). Clinical and microbiologic efficacy of levofloxacin (i.v., p.o., or i.v./p.o. for 5 to 14 days) in the microbiologically evaluable population was determined at post-therapy; a test for homogeneity of the odds ratio of the difference in clinical success for comparative versus noncomparative studies was performed.

MAIN OUTCOME MEASURES AND RESULTS

The main outcome measures were clinical success rates and microbiologic eradication rates of 419 microbiologically evaluable levofloxacin-treated subjects with MDRSP or non-MDRSP. Clinical success rates were 96.3% (52/54) and 95.1% (347/365), respectively (difference -1.2; 95% confidence interval [CI]: -6.7, 4.3). Similarly, per pathogen microbiologic eradication rates for MDRSP and non-MDRSP were 96.3% (52/54) and 95.6% (350/366), respectively (difference -0.7; 95% CI: -6.1, 4.8). Study limitations include the use of data from comparative and noncomparative studies. A test for homogeneity of the odds ratios for clinical success in comparative versus noncomparative studies showed no significant difference (p = 0.27).

CONCLUSIONS

These data support the use of levofloxacin for patients with community-acquired pneumonia caused by S. pneumoniae, including MDR strains.

Susceptibilities of Haemophilus influenzae, Streptococcus pneumoniae, including serotype 19A, and Moraxella catarrhalis paediatric isolates from 2005 to 2007 to commonly used antibiotics

OBJECTIVES

The aim of this study was to evaluate susceptibility to common paediatric antibiotics for Streptococcus pneumoniae, non-typeable Haemophilus influenzae and Moraxella catarrhalis isolated from 2005 through 2007.

METHODS

Microdilution MIC assays were performed using CLSI-approved methods. S. pneumoniae 19A strains were identified by quellung reaction.

RESULTS

Among 143 non-typeable H. influenzae, 42% produced beta-lactamase. By 2007 breakpoints (PK/PD:CLSI), percentage susceptibility for non-typeable H. influenzae was: ceftriaxone = cefixime = high-dose amoxicillin/clavulanate (all 100%:100%) > standard-dose amoxicillin/clavulanate (91.6%:100%) > cefuroxime axetil (88.1%:99.3%) > cefdinir (83.9%:100%) > trimethoprim/sulfamethoxazole (73.4%:73.4%) >high-dose amoxicillin (58%:58%) > standard-dose amoxicillin (55.2%:58%) > cefprozil (28.7%:83.2%) > cefaclor (3.5%:83.2%) > azithromycin (0%:87.4%). Of 208 S. pneumoniae (42 serotype 19A), 86 were penicillin-susceptible, 60 were penicillin-intermediate and 62 were penicillin-resistant by 2007 CLSI breakpoints. Percentage susceptibility for all S. pneumoniae/19A by PD breakpoints was: ceftriaxone (95.2%/86.1%) > high-dose amoxicillin (89.4%/58.3%) > clindamycin (85%/58.3%) > standard-dose amoxicillin (73.5%/33.3%) > cefuroxime axetil (69.2%/36.1%), cefprozil (67.3%/33.3%) > cefdinir (59.1%/33.3%) > cefixime (57.7%/33.3%) > azithromycin (56.7%/33.3%) > trimethoprim/sulfamethoxazole (50.5%/25%) > penicillin (41.3%/19.4%) > cefaclor (28.8%/8.3%). Percentage M. catarrhalis (n = 62) susceptibility by PK/PD breakpoints was: high-dose amoxicillin/clavulanate = cefixime (100%) > azithromycin (98.4%) > ceftriaxone (96.8%) > standard-dose amoxicillin/clavulanate (88.7%) > cefdinir (80.6%) > cefprozil = cefuroxime axetil (37.1%) > high-dose amoxicillin (11.2%) > cefaclor (6.5%) > standard-dose amoxicillin (4.8%).

CONCLUSIONS

Despite high rates of beta-lactamase production among non-typeable H. influenzae and M. catarrhalis, multiple oral treatment options exist for non-typeable H. influenzae and M. catarrhalis. Multidrug-resistant serotype 19A S. pneumoniae ( approximately 20%) limits treatment options for ambulatory S. pneumoniae respiratory disease.

Antibacterial activity of telithromycin and comparators against pathogens isolated from patients with community-acquired respiratory tract infections: the Prospective Resistant Organism Tracking and Epidemiology for the Ketolide Telithromycin study year 5 (2003-2004)

The activity of telithromycin and comparator antibacterials was examined in isolates of Streptococcus pneumoniae and Haemophilus influenzae isolated from patients with community-acquired pneumonia (CAP), acute exacerbations of chronic bronchitis (AECB), or sinusitis during year 5 (2003-2004) of the Prospective Resistant Organism Tracking and Epidemiology for the Ketolide Telithromycin global resistance surveillance study. Among S. pneumoniae, penicillin nonsusceptibility and erythromycin resistance were 35.7% and 36.0%, respectively. beta-Lactamase was produced by 12.3% of H. influenzae isolates. beta-Lactamase-negative ampicillin-resistant strains, mainly from Japan, comprised 5.2% of global H. influenzae isolates. Telithromycin and levofloxacin were the most active agents tested against S. pneumoniae and H. influenzae (>99% of isolates susceptible) isolated from patients with CAP, AECB, or bacterial sinusitis. Amoxicillin-clavulanate, levofloxacin, and telithromycin were the most active agents against multidrug-resistant S. pneumoniae.

Quantitative models of in vitro bacteriophage-host dynamics and their application to phage therapy

Phage therapy is the use of bacteriophages as antimicrobial agents for the control of pathogenic and other problem bacteria. It has previously been argued that successful application of phage therapy requires a good understanding of the non-linear kinetics of phage-bacteria interactions. Here we combine experimental and modelling approaches to make a detailed examination of such kinetics for the important food-borne pathogen Campylobacter jejuni and a suitable virulent phage in an in vitro system. Phage-insensitive populations of C. jejuni arise readily, and as far as we are aware this is the first phage therapy study to test, against in vitro data, models for phage-bacteria interactions incorporating phage-insensitive or resistant bacteria. We find that even an apparently simplistic model fits the data surprisingly well, and we confirm that the so-called inundation and proliferation thresholds are likely to be of considerable practical importance to phage therapy. We fit the model to time series data in order to estimate thresholds and rate constants directly. A comparison of the fit for each culture reveals density-dependent features of phage infectivity that are worthy of further investigation. Our results illustrate how insight from empirical studies can be greatly enhanced by the use of kinetic models: such combined studies of in vitro systems are likely to be an essential precursor to building a meaningful picture of the kinetic properties of in vivo phage therapy.

Cefepime: a reappraisal in an era of increasing antimicrobial resistance

Cefepime is a 'fourth-generation' cephalosporin with an in vitro extended-spectrum of activity against Gram-negative and Gram-positive pathogens. Cefepime is approved for the treatment of moderate-to-severe infections, such as pneumonia, uncomplicated and complicated urinary tract infections, skin and soft-tissue infections, intra-abdominal infections and febrile neutropenia. In this article, we provide a critical review of pharmacodynamics, clinical management, pharmacokinetics, metabolism, pharmacodynamic target analyses, clinical efficacy, safety and tolerability of cefepime after more than a decade of clinical use.

Clinical studies of garenoxacin

Garenoxacin mesylate hydrate (GRN) is a novel oral des-fluoro(6) quinolone with potent antimicrobial activity against common respiratory pathogens, including resistant strains. It has favourable pharmacokinetic profiles for maximum plasma concentration (Cmax) and area under the plasma concentration-time curve (AUC), with good penetration into sputum and otorhinolaryngological tissues. In clinical studies, the efficacy of GRN ranged from 92% to 96% in patients with bacterial pneumonia, mycoplasma pneumonia, chlamydial pneumonia and acute bronchitis. Efficacy was 85% in acute infectious exacerbations of chronic respiratory disease and ranged from 81% to 95% in otorhinolaryngological infections. Bacterial eradication was 90.9% for Staphylococcus aureus, 99.2% for Streptococcus pneumoniae, 98.2% for Haemophilus influenzae, 96.6% for Moraxella catarrhalis, 100% for penicillin-resistant S. pneumoniae, 100% for beta-lactamase-negative ampicillin-resistant H. influenzae and beta-lactamase-positive H. influenzae, and 96.2% for beta-lactamase-positive M. catarrhalis. Garenoxacin concentrations in plasma and tissues using GRN 400mg once a day were higher than the MIC90 (minimum inhibitory concentration for 90% of the organisms) of major causative pathogens. The trough concentration (Cmin) in plasma was 1.92 microg/mL, a level that was higher than the mutant prevention concentration, suggesting that GRN is unlikely to induce the selection of resistant strains during treatment. In clinical studies, GRN did not produce class adverse effects of fluoroquinolones such as QTc prolongation, blood glucose abnormality or severe liver damage. No serious adverse events were observed during the trials. The results indicate that GRN is very effective in treating patients with upper and lower respiratory tract infections.

Antibiotic resistance: a guide for effective prescribing in women's health

Current national and international trends in antibiotic resistance are becoming a public health crisis. Multi-drug resistant organisms are more prevalent in hospital settings and, alarmingly, are now being identified in the community. Over-reliance on broad-spectrum antibiotics, as well as inappropriate prescribing practices, play a significant role in encouraging the emergence of resistant organisms. This article reviews the mechanisms of bacterial resistance, current trends in national and international antibiotic resistance, and examines approaches to combat pathogens while sparing benign microbes.

Streptococcus pneumoniae: An Update on Resistance Patterns in the United States

Streptococcus pneumoniae represents an important pathogen in numerous community-acquired respiratory infections. Penicillin resistance to Streptococcus pneumoniae in the United States has approached 35%. Additionally, there has been a significant increase in Streptococcus pneumoniae resistance among many other antimicrobial agents such as cephalosporins, macrolides, trimethoprim–sulfamethoxazole, clindamycin, tetracyclines, and chloramphenicol. Several nationwide surveillance programs have been implemented to quantify the prevalence of Streptococcus pneumoniae resistance in the United States. Overall, beta-lactam, macrolide, trimethoprim–sulfamethoxazole, and tetracycline resistance has increased over the past decade while later generation fluoroquinolones (levofloxacin and moxifloxacin) resistance has remained low. Controlling the spread of resistant pneumococcal isolates and preventing the development of both fluoroquinolone and multidrug resistant isolates will require a multidisciplinary approach involving physicians, pharmacists, microbiologists, and epidemiologists.

Clinical efficacy and time to symptom resolution of 5-day telithromycin versus 10-day amoxicillin-clavulanate in the treatment of acute bacterial sinusitis

OBJECTIVE

This study compared the clinical efficacy, time to symptom resolution, and tolerability of a 5-day regimen of telithromycin with a 10-day regimen of high-dose amoxicillin-clavulanate in acute bacterial sinusitis (ABS).

RESEARCH DESIGN AND METHODS

In this multinational (41 centers in Canada, Germany, Greece, Portugal, and Turkey), open-label, noninferiority study, patients >/=18 years old (n=298) with a clinical (>7 days' symptoms) and radiological (air/fluid level, total opacification, mucosal thickening >/=10 mm) diagnosis of ABS were randomized to receive telithromycin 800 mg once daily for 5 days or amoxicillin-clavulanate 875/125 mg twice daily for 10 days. Clinical efficacy and tolerability were assessed at the test-of-cure visit (days 17-21). Time to symptom resolution was based on patients' daily diary assessment of individual symptoms.

RESULTS

The per-protocol clinical success rate (primary endpoint) with telithromycin (88.6% (109/123)) was noninferior to that with amoxicillin-clavulanate (88.8% (111/125)) (95% confidence interval: -8.9 to 8.5). In the modified intention-to-treat (mITT) population, the median time for 50% reduction of total symptom scores was significantly shorter for telithromycin (4 days) vs. amoxicillin-clavulanate (5 days; p=0.044); median times for 75% reduction of total symptom scores were: telithromycin, 7 days; amoxicillin-clavulanate, 8 days (p=0.115). The median time for reduction of total symptom scores to the absent/very mild category (mITT population) was 6 days for telithromycin vs. 8 days for amoxicillin-clavulanate (p=0.04). All treatment-emergent adverse events (TEAEs) were mostly gastrointestinal and occurred in 20.7% (30/145) of telithromycin-treated patients vs. 31.8% (47/148) of amoxicillin-clavulanate-treated patients (p=0.034). One serious AE was reported in the telithromycin group, but it was considered not to be related to treatment.

CONCLUSIONS

This open-label, randomized study demonstrated that treatment of ABS with telithromycin resulted in comparable clinical efficacy, shorter times to symptom resolution, and fewer total TEAEs than treatment with amoxicillin-clavulanate.

Increasing penicillin and trimethoprim-sulfamethoxazole resistance in nasopharyngeal Streptococcus pneumoniae isolates from Guatemalan children, 2001--2006

OBJECTIVES

We aimed to determine nasopharyngeal colonization rates and antibiotic resistance patterns of Streptococcus pneumoniae isolated from Guatemalan children, and to determine risk factors for colonization and antibiotic nonsusceptibility.

METHODS

Isolates were obtained from children aged 5 to 60 months attending public and private outpatient clinics and daycare centers during August 2001--June 2002 and outpatient clinics during November 2005--February 2006 in Guatemala City. Minimal inhibitory concentrations of penicillin, trimethoprim-sulfamethoxazole (TMS), cefotaxime, and erythromycin were determined using the E-test.

RESULTS

The overall nasopharyngeal colonization rate for S. pneumoniae was 59.1%. From 2001/2 to 2005/6 TMS nonsusceptibility increased from 42.4% to 60.8% (p<0.05) in public clinics and from 51.4% to 84.0% (p=0.009) in private clinics, and penicillin nonsusceptibility increased from 1.5% to 33.3% in public clinics (p<0.001). Reported antibiotic use was not strictly associated with nonsusceptibility to that same antibiotic. Resistance to three or four antibiotics increased in public clinics from 2001/2 (0%) to 2005/6 (10.7%; p<0.001). Risk factors for nasopharyngeal colonization with penicillin- or TMS-nonsusceptible S. pneumoniae were low family income, daycare center attendance, and recent penicillin use.

CONCLUSIONS

Increasing antibiotic nonsusceptibility rates in nasopharyngeal S. pneumoniae isolates from Guatemalan children reflect worldwide trends. Policies encouraging more judicious use of TMS should be considered.

Antimicrobial activity of cefditoren tested against contemporary (2004-2006) isolates of Haemophilus influenzae and Moraxella catarrhalis responsible for community-acquired respiratory tract infections in the United States

Among orally administered cephalosporins, aminopenicillins (+/- clavulanate), and macrolides, cefditoren was the most potent agent against Haemophilus influenzae (MIC(50/90), < or =0.008/0.03 microg/mL; 316 isolates including 100 beta-lactamase-positive and 10 beta-lactamase-negative ampicillin-resistant [BLNAR]) and was 32-, 64-, and 512-fold more potent than cefdinir, cefuroxime, and cefprozil, respectively. Cefditoren (MIC(50), 0.03 microg/mL) was also > or =32-fold more active against BLNAR phenotypes, although newer macrolides provided complete coverage against these strains. All Moraxella catarrhalis isolates were inhibited by cefditoren (0.5 microg/mL), including beta-lactamase producers (MIC(50), 0.12 vs < or =0.008 microg/mL). Cefditoren retains potent activity against respiratory tract isolates in the United States, including those with resistance phenotypes.

Common variable immunodeficiency in children

PURPOSE OF REVIEW

Common variable immunodeficiency is the most common primary immunodeficiency that needs medical attention. Symptoms may occur at any time, with two major peaks of onset at 5-10 and 20-30 years. We present the different clinical phenotypes of common variable immunodeficiency, review recent genetic findings and point to current treatment strategies.

RECENT FINDINGS

Five genes, ICOS, CD19, TNFRSF13B, TNFRSF13C and MSH5, have been found to be mutated in patients with common variable immunodeficiency. Additional possible genetic loci for autosomal dominant forms were detected on chromosomes 4q and 16q. These findings illustrate the heterogeneous molecular basis of common variable immunodeficiency and indicate the value of genetic linkage studies, thereby improving the genetic diagnosis.

SUMMARY

In young patients with unusually frequent bacterial infections, common variable immunodeficiency should always be considered as a differential diagnosis. The compulsory individual work-up should comprise a family history in order to document siblings and additional family members suffering from common variable immunodeficiency and/or selective IgA deficiency. Since the recently found gene defects affect a minority of patients with common variable immunodeficiency only, future genetic research is required to identify further susceptibility genes involved in the pathogenesis of this condition.

National and regional assessment of antimicrobial resistance among community-acquired respiratory tract pathogens identified in a 2005-2006 U.S. Faropenem surveillance study

Surveillance studies conducted in the United States over the last decade have revealed increasing resistance among community-acquired respiratory pathogens, especially Streptococcus pneumoniae, that may limit future options for empirical therapy. The objective of this study was to assess the scope and magnitude of the problem at the national and regional levels during the 2005-2006 respiratory season (the season when community-acquired respiratory pathogens are prevalent) in the United States. Also, since faropenem is an oral penem being developed for the treatment of community-acquired respiratory tract infections, another study objective was to provide baseline data to benchmark changes in the susceptibility of U.S. respiratory pathogens to the drug in the future. The in vitro activities of faropenem and other agents were determined against 1,543 S. pneumoniae isolates, 978 Haemophilus influenzae isolates, and 489 Moraxella catarrhalis isolates collected from 104 U.S. laboratories across six geographic regions during the 2005-2006 respiratory season. Among S. pneumoniae isolates, the rates of resistance to penicillin, amoxicillin-clavulanate, and cefdinir were 16, 6.4, and 19.2%, respectively. The least effective agents were trimethoprim-sulfamethoxazole (SXT) and azithromycin, with resistance rates of 23.5 and 34%, respectively. Penicillin resistance rates for S. pneumoniae varied by region (from 8.7 to 22.5%), as did multidrug resistance rates for S. pneumoniae (from 8.8 to 24.9%). Resistance to beta-lactams, azithromycin, and SXT was higher among S. pneumoniae isolates from children than those from adults. beta-Lactamase production rates among H. influenzae and M. catarrhalis isolates were 27.4 and 91.6%, respectively. Faropenem MICs at which 90% of isolates are inhibited were 0.5 mug/ml for S. pneumoniae, 1 mug/ml for H. influenzae, and 0.5 mug/ml for M. catarrhalis, suggesting that faropenem shows promise as a treatment option for respiratory infections caused by contemporary resistant phenotypes.

TARGETed surveillance: susceptibility of Streptococcus pneumoniae isolated from community-acquired respiratory tract infections in 2003 to fluoroquinolones and other agents

We assessed antibiotic resistance in Streptococcus pneumoniae collected worldwide in 2003. Resistance to clarithromycin was the highest overall (34.1%) followed by penicillin G (22.1%). Patient age and/or country of origin had the greatest effect on susceptibility. Resistance was highest in children<6 years of age and in patients from South Africa or France. Resistance to penicillin or amoxicillin/clavulanic acid decreased in adults and was low in Germany. Fluoroquinolone resistance was very low overall, but 3.0% levofloxacin resistance (2.6% gatifloxacin and 0.4% moxifloxacin) was observed in Italy. Interestingly, many isolates with minimum inhibitory concentrations (MICs) at the top of the fluoroquinolone susceptibility breakpoints possessed single quinolone resistance-determining region (QRDR) mutations. Care should be taken when treating fluoroquinolone-susceptible isolates with a higher MIC, which are likely to harbour QRDR mutations and may become fully resistant and cause treatment failure. We concur with the conclusions of other recent studies that suggest fluoroquinolone breakpoints should be lowered to ensure these isolates are categorised as resistant. Fluoroquinolones would still remain an important alternative treatment for respiratory tract infections (albeit for adults only), with moxifloxacin being the most potent fluoroquinolone tested in this study.

Retrospective analysis of electrocardiographic changes after administration of oral or intravenous garenoxacin in five phase I, placebo-controlled studies in healthy volunteers

BACKGROUND

Certain fluoroquinolones and macrolide antibiotics have been associated with prolongation of the corrected QT (QTc) interval or QT dispersion, leading to cardiac arrhythmias. Garenoxacin is a des-F(6)-quinolone with broad-spectrum antimicrobial activity and a favorable pharmacokinetic/pharmacodynamic profile. Its effects on electrocardiographic (ECG) parameters in healthy volunteers have not been reported.

OBJECTIVE

The cardiac safety profile of garenoxacin was further examined using data from healthy volunteers enrolled in 5 dose-ranging and comparative Phase I clinical studies.

METHODS

This was a retrospective analysis of 5 randomized, double-blind, placebo-controlled studies in which 224 healthy volunteers received oral or intravenous garenoxacin (50-1200 mg/d) for 1 to 28 days' dosing duration (<or=14 days' therapeutic duration). The effects of garenoxacin on the QT interval corrected using Bazett's formula (QTcB) and Fridericia's formula (QTcF) and the PR interval were assessed by counts of outliers, linear regressions, and exposure-response plots. Absence of a concentration-dependent effect of garenoxacin on changes from baseline ECG parameters was concluded if the 95% CI for the linear regression slopes of derived QTc- or PR-interval parameters relative to Cmax and C(avg0-12) (average garenoxacin plasma concentration from 0-12 hours after dosing) values for garenoxacin contained zero.

RESULTS

No clinically relevant changes in the QTc or PR intervals were observed over a range of garenoxacin plasma concentrations (Cmax: 0.5-38.6 microg/mL, oral dose range; 3.36-21.4 microg/mL, intravenous dose range). No volunteer had a prolongation from baseline that exceeded established thresholds for the QTcB or QTcF interval (>450 milliseconds for men, >470 milliseconds for women) or the PR interval (>250 milliseconds). One subject had a change in QTcB of 67 milliseconds 4 hours after administration of garenoxacin 400 mg PO on day 7, but the actual value was 418 milliseconds (baseline, 351 milliseconds); the corresponding change in QTcF was 49 milliseconds (actual, 408 milliseconds; baseline, 359 milliseconds). The means for other derived ECG parameters were generally similar between garenoxacin-treated volunteers and placebo controls.

CONCLUSION

In this retrospective analysis of data from healthy volunteers, garenoxacin had no clinically relevant dose-, route-of-administration-, or concentration-dependent effects on the QTc or PR interval across a dose range from 50 to 1200 mg/d.