Fluoroquinolone resistance among Streptococcus pneumoniae in Hong Kong linked to the Spanish 23F clone

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.

Prospective surveillance study of invasive pneumococcal disease among urban children in the Philippines

BACKGROUND

Worldwide, invasive pneumococcal disease (IPD) causes considerable morbidity and mortality among children, but incidence data in Asia are lacking. This 2-year hospital-based, prospective, surveillance study was conducted at 3 study sites in urban areas of the Philippines to estimate IPD and pneumonia incidence in children and describe the serotype distribution of invasive Streptococcus pneumoniae isolates.

METHODS

Children aged 28 days to <60 months residing within the 3 surveillance areas presenting with possible IPD were enrolled. Initial diagnosis, history of pneumococcal vaccine receipt and previous antimicrobial treatment were recorded. Blood specimens were collected for S. pneumoniae identification and serotyping. Final diagnosis was determined for hospitalized subjects, subjects whose culture yielded S. pneumoniae and subjects with clinically suspected meningitis.

RESULTS

A total of 5940 subjects were enrolled, 47 IPD cases identified. IPD site rates were 33.49 per 100,000, 25.38 per 100,000 and 25.85 per 100,000. Chest radiograph-confirmed pneumonia incidence ranged from 633.74 to 1683.59 per 100,000. Highest chest radiograph-confirmed pneumonia incidence occurred in those 28 days to <6 months of age at 2 sites (2166.16 and 3891.94 per 100,000) and those 6-12 months of age at the third site (3847.52 per 100,000). Thirty-five S. pneumoniae isolates were serotyped; most commonly identified were serotypes 1, 2, 5, 6B, 14 and 18F. One serotype 14 isolate was erythromycin resistant. Previous antibiotic therapy was documented in 17-53% of subjects; 2 subjects had received pneumococcal vaccine. At 2 sites, one-third of IPD subjects died.

CONCLUSIONS

IPD is an important cause of morbidity and mortality among urban children in the Philippines. Our data support the expectation that widespread immunization would decrease IPD disease burden.

Increasing genetic relatedness of ciprofloxacin-resistant Streptococcus pneumoniae isolated in Canada from 1997 to 2005

The genetic relatedness of ciprofloxacin-resistant Streptococcus pneumoniae isolates collected from 1997 to 2002 (n = 82) and 2003 to 2005 (n = 123) was compared by pulsed-field gel electrophoresis (PFGE). Increased genetic homogeneity among the isolates from 2003 to 2005 (cluster analysis; P < 0.001) appeared to be due to expansion of existing clonal groups and to introduction of new PFGE types.

Longitudinally tracking fluoroquinolone resistance and its determinants in penicillin-susceptible and -nonsusceptible Streptococcus pneumoniae isolates in Hong Kong, 2000 to 2005

Of 1,388 Streptococcus pneumoniae isolates collected from 2000 to 2005, 10.5% had a ciprofloxacin MIC of >/=4.0 mug/ml and 1.6% (range, 0.8% to 4.3% per year) had a levofloxacin MIC of >/=4.0 mug/ml. Molecular characterization indicated that fluoroquinolone resistance occurred independently in our prevalent Spain(23F)-1 clone, expressing serotypes 23F, 19F, and 14. Rates of resistance to levofloxacin in S. pneumoniae have remained stable at a Hong Kong hospital.

Serotype competence and penicillin resistance in Streptococcus pneumoniae

Enhanced molecular surveillance of virulent clones with higher competence can detect serotype switching.

From 2003 to 2005, we prospectively collected 118 isolates of pneumococci belonging to 7 serotypes to investigate their competence under the influence of the synthetic competence-stimulating peptides. The degree of competence of the various serotypes differed significantly. Serotype 6B had the highest competence, followed by serotypes 14, 19F, 9V, 23F, 3, and 18C. Isolates belonging to serotype 6B had greater genetic diversity than isolates belonging to serotype 3, which has high genetic clustering. Isolates belonging to serotypes 3 and 18C that were 100% sensitive to penicillin were significantly less competent than isolates belonging to serotypes 6B, 14, 19F, 9V, and 23F, which were frequently resistant to penicillin. Under the 7-valent pneumococcal conjugate vaccine program, enhanced molecular surveillance of virulent clones with higher competence to detect serotype switching will become more important.

Molecular evolution perspectives on intraspecific lateral DNA transfer of topoisomerase and gyrase loci in Streptococcus pneumoniae, with implications for fluoroquinolone resistance development and spread

Fluoroquinolones are an important class of antibiotics for the treatment of infections arising from the gram-positive respiratory pathogen Streptococcus pneumoniae. Although there is evidence supporting interspecific lateral DNA transfer of fluoroquinolone target loci, no studies have specifically been designed to assess the role of intraspecific lateral transfer of these genes in the spread of fluoroquinolone resistance. This study involves a comparative evolutionary perspective, in which the evolutionary history of a diverse set of S. pneumoniae clinical isolates is reconstructed from an expanded multilocus sequence typing data set, with putative recombinants excluded. This control history is then assessed against networks of each of the four fluoroquinolone target loci from the same isolates. The results indicate that although the majority of fluoroquinolone target loci from this set of 60 isolates are consistent with a clonal dissemination hypothesis, 3 to 10% of the sequences are consistent with an intraspecific lateral transfer hypothesis. Also evident were examples of interspecific transfer, with two isolates possessing a parE-parC gene region arising from viridans group streptococci. The Spain 23F-1 clone is the most dominant fluoroquinolone-nonsusceptible clone in this set of isolates, and the analysis suggests that its members act as frequent donors of fluoroquinolone-nonsusceptible loci. Although the majority of fluoroquinolone target gene sequences in this set of isolates can be explained on the basis of clonal dissemination, a significant number are more parsimoniously explained by intraspecific lateral DNA transfer, and in situations of high S. pneumoniae population density, such events could be an important means of resistance spread.

Antimicrobial resistance in developing countries. Part I: recent trends and current status

The global problem of antimicrobial resistance is particularly pressing in developing countries, where the infectious disease burden is high and cost constraints prevent the widespread application of newer, more expensive agents. Gastrointestinal, respiratory, sexually transmitted, and nosocomial infections are leading causes of disease and death in the developing world, and management of all these conditions has been critically compromised by the appearance and rapid spread of resistance. In this first part of the review, we have summarised the present state of resistance in these infections from the available data. Even though surveillance of resistance in many developing countries is suboptimal, the general picture is one of accelerating rates of resistance spurred by antimicrobial misuse and shortfalls in infection control and public health. Reservoirs for resistance may be present in healthy human and animal populations. Considerable economic and health burdens emanate from bacterial resistance, and research is needed to accurately quantify the problem and propose and evaluate practicable solutions. In part II, to be published next month, we will review potential containment strategies that could address this burgeoning problem.

Antimicrobial susceptibility of Streptococcus pneumoniae in eight European countries from 2001 to 2003

Susceptibility testing results for Streptococcus pneumoniae isolates (n = 2,279) from eight European countries, examined in the PneumoWorld Study from 2001 to 2003, are presented. Overall, 24.6% of S. pneumoniae isolates were nonsusceptible to penicillin G and 28.0% were resistant to macrolides. The prevalence of resistance varied widely between European countries, with the highest rates of penicillin G and macrolide resistance reported from Spain and France. Serotype 14 was the leading serotype among penicillin G- and macrolide-resistant S. pneumoniae isolates. One strain (PW 158) showed a combination of an efflux type of resistance with a 23S rRNA mutation (A2061G, pneumococcal numbering; A2059G, Escherichia coli numbering). Six strains which showed negative results for mef(A) and erm(B) in repeated PCR assays had mutations in 23S rRNA or alterations in the L4 ribosomal protein (two strains). Fluoroquinolone resistance rates (levofloxacin MIC > or = 4 microg/ml) were low (Austria, 0%; Belgium, 0.7%; France, 0.9%; Germany, 0.4%; Italy, 1.3%; Portugal, 1.2%; Spain, 1.0%; and Switzerland, 0%). Analysis of quinolone resistance-determining regions showed eight strains with a Ser81 alteration in gyrA; 13 of 18 strains showed a Ser79 alteration in parC. The clonal profile, as analyzed by multilocus sequence typing (MLST), showed that the 18 fluoroquinolone-resistant strains were genetically heterogeneous. Seven of the 18 strains belonged to new sequence types not hitherto described in the MLST database. Europe-wide surveillance for monitoring of the further spread of these antibiotic-resistant S. pneumoniae clones is warranted.

Levofloxacin-resistant invasive Streptococcus pneumoniae in the United States: evidence for clonal spread and the impact of conjugate pneumococcal vaccine

The emergence of fluoroquinolone resistance in sterile-site isolates of Streptococcus pneumoniae is documented in this study characterizing all invasive levofloxacin-resistant (MIC, > or = 8 mg/liter) S. pneumoniae isolates (n = 50) obtained from the Centers for Disease Control and Prevention Active Bacterial Core Surveillance from 1998 to 2002. Resistance among all isolates increased from 0.1% in 1998 to 0.6% in 2001 (P = 0.008) but decreased to 0.4% in 2002, while resistance among vaccine serotypes continued to increase from 0.3% in 1998 to 1.0% in 2002, suggesting that fluoroquinolones continue to exert selective pressure on these vaccine serotypes. Only 22% of resistant isolates were not covered by the conjugate vaccine serogroups. Multilocus sequence typing revealed that 58% of resistant strains were related to five international clones identified by the Pneumococcal Molecular Epidemiology Network, with the Spain(23F)-1 clone being most frequent (16% of all isolates). Thirty-six percent of the isolates were coresistant to penicillin, 44% were coresistant to macrolides, and 28% were multiresistant to penicillin, macrolides, and fluoroquinolones. Fifty percent of the isolates were resistant to any three drug classes. Ninety-four percent of the isolates had multiple mutations in the quinolone resistance-determining regions of the gyrA, gyrB, parC, and parE genes. In 16% of the isolates, there was evidence of an active efflux mechanism. An unusual isolate was found that showed only a single parE mutation and for which the ciprofloxacin MIC was lower (2 mg/liter) than that of levofloxacin (8 mg/liter). Our results suggest that invasive pneumococcal isolates resistant to levofloxacin in the United States show considerable evidence of multiple resistance and of clonal spread.

High prevalence of antimicrobial resistance among clinical Streptococcus pneumoniae isolates in Asia (an ANSORP study)

A total of 685 clinical Streptococcus pneumoniae isolates from patients with pneumococcal diseases were collected from 14 centers in 11 Asian countries from January 2000 to June 2001. The in vitro susceptibilities of the isolates to 14 antimicrobial agents were determined by the broth microdilution test. Among the isolates tested, 483 (52.4%) were not susceptible to penicillin, 23% were intermediate, and 29.4% were penicillin resistant (MICs >/= 2 mg/liter). Isolates from Vietnam showed the highest prevalence of penicillin resistance (71.4%), followed by those from Korea (54.8%), Hong Kong (43.2%), and Taiwan (38.6%). The penicillin MICs at which 90% of isolates are inhibited (MIC(90)s) were 4 mg/liter among isolates from Vietnam, Hong Kong, Korea, and Taiwan. The prevalence of erythromycin resistance was also very high in Vietnam (92.1%), Taiwan (86%), Korea (80.6%), Hong Kong (76.8%), and China (73.9%). The MIC(90)s of erythromycin were >32 mg/liter among isolates from Korea, Vietnam, China, Taiwan, Singapore, Malaysia, and Hong Kong. Isolates from Hong Kong showed the highest rate of ciprofloxacin resistance (11.8%), followed by isolates from Sri Lanka (9.5%), the Philippines (9.1%), and Korea (6.5%). Multilocus sequence typing showed that the spread of the Taiwan(19F) clone and the Spain(23F) clone could be one of the major reasons for the rapid increases in antimicrobial resistance among S. pneumoniae isolates in Asia. Data from the multinational surveillance study clearly documented distinctive increases in the prevalence rates and the levels of antimicrobial resistance among S. pneumoniae isolates in many Asian countries, which are among the highest in the world published to date.

Telithromycin- and fluoroquinolone-resistant Streptococcus pneumoniae in Taiwan with high prevalence of resistance to macrolides and beta-lactams: SMART program 2001 data

There is a high prevalence of beta-lactam- and macrolide-resistant Streptococcus pneumoniae in Taiwan. To understand the in vitro susceptibilities of recent isolates of S. pneumoniae to fluoroquinolones and telithromycin (which is not available in Taiwan), the MICs of 23 antimicrobial agents for 936 clinical isolates of S. pneumoniae isolated from different parts of Taiwan from 2000 to 2001 were determined by the agar dilution method. Overall, 72% of isolates were not susceptible to penicillin (with 61% being intermediate and 11% being resistant) and 92% were resistant to erythromycin. Telithromycin MICs were >or=1 microg/ml for 16% of the isolates, and for 99% of these isolates the MICs of all macrolides tested were >or=256 microg/ml; all of these isolates had the constitutive macrolide-lincosamide-streptogramin B phenotype. Eighty-eight percent of the isolates were resistant to three or more classes of drugs. The ciprofloxacin MICs were >or=4 microg/ml for six (0.6%) isolates from five patients collected in 2000 and 2001, and the levofloxacin MICs were >or=8 microg/ml for five of these isolates. Seven isolates for which ciprofloxacin MICs were >or=4 microg/ml, including one isolate recovered in 1999, belonged to three serotypes (serotype 19F, five isolates; serotype 23A, one isolate; and serotype 23B, one isolate). The isolates from the six patients for which ciprofloxacin MICs were >or=4 microg/ml had different pulsed-field gel electrophoresis profiles and random amplified polymorphic DNA patterns, indicating that no clonal dissemination occurred over this time period. Despite the increased rate of fluoroquinolone use, the proportion of pneumococcal isolates for which ciprofloxacin MICs were elevated (>or=4 microg/ml) remained low. However, the occurrence of telithromycin resistance is impressive and raises concerns for the future.

Report from a WHO Working Group: standard method for detecting upper respiratory carriage of Streptococcus pneumoniae

BACKGROUND

Numerous studies evaluating the efficacy of conjugate pneumococcal vaccines are being conducted or planned throughout the world. Some of these studies are evaluating the effect of vaccine on nasopharyngeal (NP) carriage.

METHODS

The World Health Organization established a Working Group comprised of representatives from these trials and other NP colonization experts to establish core, standardized methods for the study of pneumococcal NP colonization that could be used in these trials. The intent was to reduce or eliminate variability in key methods which themselves could contribute to variability of observed pneumococcal NP colonization. In this way variability of vaccine effects between trials on NP colonization could more easily be analyzed for population or vaccine differences without the confounding effect caused by differences in study methodology.

RESULTS

This paper presents the evidence base supporting the need for standardized NP colonization study methods, the methods themselves (Core Consensus Methods), including collection techniques, culture media, equipment, serotyping, storage of specimens and transport of isolates agreed on by the Working Group as well as a discussion of research priorities.

CONCLUSIONS

The Core Consensus Methods provide a common methodology to conduct pneumococcal NP colonization studies with minimum interstudy method variability. The intention is to allow more meaningful comparisons of study results from conjugate pneumococcal vaccine trials.

Report from a WHO working group: standard method for detecting upper respiratory carriage of Streptococcus pneumoniae

BACKGROUND

Numerous studies evaluating the efficacy of conjugate pneumococcal vaccines are being conducted or planned throughout the world. Some of these studies are evaluating the effect of vaccine on nasopharyngeal (NP) carriage.

METHODS

The World Health Organization established a Working Group composed of representatives from these trials and other NP colonization experts to establish core, standardized methods for the study of pneumococcal NP colonization that could be used in these trials. The intent was to reduce or eliminate variability in key methods which themselves could contribute to variability of observed pneumococcal NP colonization. In this way variability of vaccine effects between trials on NP colonization could more easily be analyzed for population or vaccine differences without the confounding effect caused by differences in study methodology.

RESULTS

This paper presents the evidence base supporting the need for standardized NP colonization study methods, the methods themselves (Core Consensus Methods found in the electronic version of this article at www.pidj.com and on the WHO website at http://www.who.int/vaccines-research/rd/docsrd.shtml), including collection techniques, culture media, equipment, serotyping, storage of specimens and transport of isolates agreed on by the Working Group as well as a discussion of research priorities.

CONCLUSIONS

The Core Consensus Methods provide a common methodology to conduct pneumococcal NP colonization studies with minimum interstudy method variability. The intention is to allow more meaningful comparisons of study results from conjugate pneumococcal vaccine trials.

Surveillance of resistance in bacteria causing community-acquired respiratory tract infections

Bacterial resistance to antibiotics in community-acquired respiratory tract infections is a serious problem and is increasing in prevalence world-wide at an alarming rate. Streptococcus pneumoniae, one of the main organisms implicated in respiratory tract infections, has developed multiple resistance mechanisms to combat the effects of most commonly used classes of antibiotics, particularly the beta-lactams (penicillin, aminopenicillins and cephalosporins) and macrolides. Furthermore, multidrug-resistant strains of S. pneumoniae have spread to all regions of the world, often via resistant genetic clones. A similar spread of resistance has been reported for other major respiratory tract pathogens, including Haemophilus influenzae, Moraxella catarrhalis and Streptococcus pyogenes. To develop and support resistance control strategies it is imperative to obtain accurate data on the prevalence, geographic distribution and antibiotic susceptibility of respiratory tract pathogens and how this relates to antibiotic prescribing patterns. In recent years, significant progress has been made in developing longitudinal national and international surveillance programs to monitor antibiotic resistance, such that the prevalence of resistance and underlying trends over time are now well documented for most parts of Europe, and many parts of Asia and the Americas. However, resistance surveillance data from parts of the developing world (regions of Central America, Africa, Asia and Central/Eastern Europe) remain poor. The quantity and quality of surveillance data is very heterogeneous; thus there is a clear need to standardize or validate the data collection, analysis and interpretative criteria used across studies. If disseminated effectively these data can be used to guide empiric antibiotic therapy, and to support-and monitor the impact of-interventions on antibiotic resistance.

Antimicrobial resistance in Streptococcus pneumoniae, Taiwan

Taiwan has one of the highest levels of antibiotic-resistant pneumococcus in the world. Pneumococcal isolates not susceptible to penicillin first appeared in Taiwan in 1986; in 1995 an increase in the prevalence of nonsusceptibility to penicillins, extended-spectrum cephalosporins, trimethoprim-sulfamethoxazole, and macrolides as well as multidrug resistance began to be recognized. With the persistence of antibiotic selective pressure, resistance in some antibiotics reached a high plateau (beta-lactam antibiotics) or continued to increase (macrolides), while novel resistance (fluoroquinolones) emerged in the last 3 years. Widespread distribution of some novel resistant 23F and 19F clones (and the international epidemic of 23F clones) contributes further to the rapid increase of resistance. Because Streptococcus pneumoniae is a major pathogen that causes community-acquired lower respiratory tract infections and meningitis in adults and children, antibiotic-resistance in this organism is a serious problem.