Prevalence of Ile-460-Val/ParE Substitution in Clinical Streptococcus pneumoniae Isolates That Were Less Susceptible to Fluoroquinolones

Highly Resistant Serotype 19A Streptococcus pneumoniae of the GPSC1/CC320 Clone from Invasive Infections in Poland Prior to Antipneumococcal Vaccination of Children

INTRODUCTION

The introduction of pneumococcal conjugate vaccines (PCV) into the national immunization programs (NIPs) has significantly reduced the number of pneumococcal infections. However, infections caused by isolates of non-vaccine serotypes (NVT) started spreading shortly thereafter and strains of NVT 19A have become the main cause of invasive pneumococcal disease burden worldwide. The aim of the study was to characterize serotype 19A invasive pneumococci of GPSC1/CC320 circulating in Poland before the introduction of PCV into the Polish NIP in 2017 and to compare them to isolates from other countries where PCVs were implemented much earlier than in Poland.

METHODS

All the GPSC1/CC320 isolates were analyzed by serotyping, susceptibility testing, and whole genome sequencing followed by analyses of resistome, virulome, and core genome multilocus sequence typing (cgMLST), including comparative analysis with isolates with publicly accessible genomic sequences (PubMLST).

RESULTS

During continuous surveillance the NRCBM collected 4237 invasive Streptococcus pneumoniae isolates between 1997 and 2016, including 200 isolates (4.7%) of serotype 19A. The most prevalent among 19A pneumococci were highly resistant representatives of Global Pneumococcal Sequence Cluster 1/Clonal Complex 320, GPSC1/CC320 (n = 97, 48.5%). Isolates of GPSC1/CC320 belonged to three sequence types (STs): ST320 (75.2%) ST4768 (23.7%), and ST15047 (1.0%), which all represented the 19A-III cps subtype and had complete loci for both PI-1 and PI-2 pili types. On the basis of the cgMLST analysis the majority of Polish GPSC1/CC320 isolates formed a group clearly distinct from pneumococci of this clone observed in other countries.

CONCLUSION

Before introduction of PCV in the Polish NIP we noticed an unexpected increase of serotype 19A in invasive pneumococcal infections, with the most common being representatives of highly drug-resistant GPSC1/CC320 clone, rarely identified in Europe both before and even after PCV introduction.

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

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

Molecular Investigation of Quinolone Resistance of Quinolone Resistance-Determining Region in Streptococcus pneumoniae Strains Isolated from Iran Using Polymerase Chain Reaction-Restriction Fragment Length Polymorphism Method

Objectives

The resistance of Streptococcus pneumoniae to the recently available antibiotic treatment has been a growing problem. The aim of the study was to determine the quinolone-resistant strains and detect the presence of mutations in the quinolone resistance-determining regions of the gyrA, parE, and parC genes.

Methods

In this study, for the first time in Iran, the polymerase chain reaction–restriction fragment length polymorphism (PCR-RFLP) method was used to investigate the presence of mutations at quinolone resistance-determining regions of topoisomerase IV and DNA gyrase on 82 S. pneumoniae strains, among them 45 clinical samples were from patients and 37 from healthy carriers (control group).

Results

In clinical samples, 34 (75.56%) strains contained mutations in the parC gene, 31 (68.89%) carried mutations in the gyrA gene, and 14 (31.11%) had parE gene mutations. Antibiotic susceptibility test was performed using the CLSI (Clinical and Laboratory Standards Institute) criteria on three different generations of quinolone family, with nalidixic acid (82.22%) showing the highest resistance and levofloxacin (42.22%) the least resistance.

Conclusion

Results indicated that there is a significant correlation between quinolone resistance development and mutations in the parE gene as well as in the parC and gyrA genes.

High prevalence of multiresistance in levofloxacin-nonsusceptible Streptococcus pneumoniae isolates in Korea

Korea exhibits the highest rates of multidrug resistance among Streptococcus pneumoniae. The increasing use of levofloxacin has raised concern about the dissemination of levofloxacin resistance in dominant multidrug-resistant (MDR) clones of our pneumococcal population. A total of 50 levofloxacin-nonsusceptible S. pneumoniae (MIC, ≥4 μg/mL) collected from a multihospital network from 1996 to 2006 were analyzed for serotype, antibiotic resistance profile, quinolone resistance-determining region mutation, and multilocus sequence type. Most levofloxacin-nonsusceptible S. pneumoniae (94.0%) exhibited an MDR phenotype. This phenotype was closely associated with a limited number of epidemic MDR clones that are well-known key agents of the global spread of antimicrobial resistance in S. pneumoniae. However, the clonal dissemination of levofloxacin-nonsusceptible S. pneumoniae was rare. Levofloxacin-nonsusceptible clones with nonvaccine serotypes increased during the post-vaccine era in this study. This result suggests that Korean clinicians must be aware of the levofloxacin resistance trend and need to be more prudent for the first choice of fluoroquinolone for empiric treatment of respiratory tract infections in clinical setting. Moreover, the emergence of new clones and their variations may be more frequently associated with resistance under this selective pressure, such as the introduction of a 7-valent pneumococcal conjugate vaccine into our community.

Dual-targeting properties of the 3-aminopyrrolidyl quinolones, DC-159a and sitafloxacin, against DNA gyrase and topoisomerase IV: contribution to reducing in vitro emergence of quinolone-resistant Streptococcus pneumoniae

OBJECTIVES

DC-159a (a novel quinolone) and sitafloxacin (DU-6859a) are structurally related quinolones, bearing a 3-aminopyrrolidyl substitution. We investigated the relationship between the target preferences of these 3-aminopyrrolidyl quinolones, in vitro potencies and emergence of quinolone-resistant mutants in Streptococcus pneumoniae, compared with other quinolones.

METHODS

MICs, resistance frequencies and mutant prevention concentrations (MPCs) were determined using quinolone-susceptible strains and first-step parC mutant strains of S. pneumoniae. Target preferences were tested by the following two methods: antibacterial activities against gyrA or parC mutants and in vitro enzyme assays for the determination of 50% inhibition (IC(50)) values.

RESULTS

DC-159a and sitafloxacin exhibited potent antibacterial activities, low frequencies of mutant selection, low MPCs and narrow mutant selection windows against both quinolone-susceptible strains and first-step parC mutants of S. pneumoniae, compared with gatifloxacin, moxifloxacin and other quinolones tested. DC-159a and sitafloxacin showed relatively low MIC ratios against single gyrA or parC mutants relative to the wild-type strain and low IC(50) ratios against DNA gyrase and topoisomerase IV.

CONCLUSIONS

DC-159a and sitafloxacin demonstrated a more balanced dual-targeting activity than gatifloxacin, moxifloxacin and other quinolones tested. In addition, DC-159a and sitafloxacin have a lower propensity for selecting first- and second-step resistant mutants.

Emergence of fluoroquinolone resistance in group B streptococcal isolates in Taiwan

Of 1,994 group B streptococcal isolates collected, 26 (1.3%) of the isolates were resistant to levofloxacin, and cross-resistance to other fluoroquinolones was observed. The emergence and prevalence of high-level fluoroquinolone resistance in genetically unrelated isolates were linked to the presence of gyrA, parC, and parE triple mutations in each isolate.

Emergence and epidemiology of fluoroquinolone-resistant Streptococcus pneumoniae strains from Italy: report from the SENTRY Antimicrobial Surveillance Program (2001–2004)

Fluoroquinolones are key antimicrobials in the treatment of more serious pneumococcal infections, especially for treating infections caused by penicillin-resistant strains. Increased use of newer fluoroquinolones should be accompanied by greater surveillance efforts to monitor resistance development as well as clonal dissemination. Streptococcus pneumoniae (n=551) collected from 3 medical centers in Italy (Catania, Genoa, and Rome) over a period of 4 years (2001-2004) as part of the SENTRY Antimicrobial Surveillance Program were susceptibility tested against >30 antimicrobials using reference broth microdilution methods. Mutations in the quinolone resistance-determining region (QRDR) were characterized by PCR and sequencing of parC, parE, and gyrA. Epidemiological relationships among levofloxacin-resistant isolates were determined using ribotyping, PFGE, serotyping combined with antimicrobial resistance profiles augmented by QRDR mutation patterns. Eighty-three (15.1%) isolates showed reduced susceptibility to ciprofloxacin (MIC>or=4 microg/mL) and 31 (5.6%) were resistant to levofloxacin. In 2001, all pneumococcal isolates were susceptible to levofloxacin and resistance rapidly emerged in all 3 medical centers in 2002. The overall rates of levofloxacin resistance in 2002-2004 were the following: Catania 10.9%, Genoa 3.3%, and Rome 6.5%. All resistant strains showed at least one mutation in parC and gyrA. Each isolate from Genoa with a unique resistance phenotype also showed distinct ribotype/PFGE, serotype, and QRDR mutation patterns. All isolates from Catania (n=19) showed an identical ribotype/PFGE pattern (333.3/A1); however, 3 distinct clusters could be identified based on further resistance phenotype, serotypes, and QRDR mutation pattern analysis. Two clusters were documented among isolates from Rome based on ribotype/PFGE. One isolate from Genoa shared ribotype/PFGE (333.3/A1) and serotype (9 not V) results with clusters from the other 2 institutions monitored, indicating clonal dissemination between the geographically diverse cities. In conclusion, fluoroquinolone resistance rates have increased among S. pneumoniae recovered in Italian medical centers evaluated by the SENTRY Program. Although resistance has emerged in many epidemiologically distinct strains, clonal dissemination seems to be a key contributing factor for increasing resistance to fluoroquinolones among pneumococci in this nation.