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

Consideration in treatment decisions for refractory Mycoplasma pneumoniae pneumonia

Mycoplasma pneumoniae (MP) is the most common cause of childhood bacterial pneumonia. Although macrolide is known to be effective as a first-line therapy, the proportion of macrolide resistance in MP pneumonia has strikingly increased during recent 2 decades in East Asia. This is challenging to physicians since they have to decide more often whether to use secondary treatment. Diagnostic methods to detect macrolide-resistance of MP are currently not available in Korean hospitals. Even in the diagnosis of MP infection, both serologic and molecular test have limitation: inability to differentiate current illness from carriage or asymptomatic infection. Combining these 2 diagnostic methods and excluding infection caused by other respiratory pathogens allow a more reliable diagnosis. This effort is even more demanding in recent years to keep children from unnecessary exposure to secondary antibiotics. Although several observational studies have reported that tetracycline and fluoroquinolone, which are considered in the treatment of refractory MP pneumonia, have efficacy of shortening the duration of fever and respiratory symptoms, those findings need to be proven by well-designed prospective studies. The use of tetracycline and fluoroquinolone in children is generally tolerable, as supported by many observational data. However, since concerns about side effects still remain, careful consideration about benefits and risks is needed to decide their use.

Emergence of Haemophilus influenzae with low susceptibility to quinolones isolated from pediatric patients in Japan

INTRODUCTION

In 2010, oral fluoroquinolone tosufloxacin (TFX) granules were released as the first oral respiratory quinolone for children in Japan.

METHODS

To investigate the recent trend of H. influenzae strains with low susceptibility to quinolones in children, we analyzed the gene sequences of quinolone resistance-determining regions (QRDRs) of gyrA, gyrB, parC, and parE of 23 clinical isolates from 15 patients aged <15 years with an MIC of ≥0.5 μg/mL for TFX from 2010 to 2018.

RESULTS

Amino acid substitutions were observed in both GyrA and ParC in 13 strains (81%, 13/16), except two strains with a TFX MIC of 0.5 μg/mL with amino acid substitution in only GyrA and one strain with a TFX MIC of 1 μg/mL with no amino acid substitution. Four ST422 strains were observed in 2018, the detection age range was wide (0-7 years), and the residential city was varied. A total of 3/15 patients had a clear history of TFX treatment.

CONCLUSIONS

Even for the strain with an MIC of 0.5 μg/mL for TFX, it is highly possible that it harbors a mutation in gyrA, which is the first step toward quinolone resistance, and it may also harbor mutations in both gyrA and parC. Furthermore, several specific sequence type quinolone-resistant H. influenzae strains, particularly ST422, may be widespread among children in Japan. It is necessary to investigate changes in resistance both at the MIC and gene levels. The continuous monitoring of strains and the use of antimicrobial drugs in treatment should be carefully observed.

Nationwide surveillance of bacterial pathogens isolated from children conducted by the surveillance committee of Japanese Society of Chemotherapy, the Japanese Association for Infectious Diseases, and the Japanese Society for Clinical Microbiology in 2017: General overview of pathogenic antimicrobial susceptibility

A nationwide surveillance of the antimicrobial susceptibility of pediatric patients to bacterial pathogens was conducted by Japanese Society of Chemotherapy, the Japanese Association for Infectious Diseases, and the Japanese Society for Clinical Microbiology in Japan in 2017. The isolates were collected from 18 medical facilities between March 2017 and May 2018 by the three societies. Antimicrobial susceptibility testing was conducted at the central laboratory (Infection Control Research Center, Kitasato University, Tokyo) according to the methods recommended by the Clinical Laboratory Standards Institute. Susceptibility testing was evaluated in 926 strains (331 Streptococcus pneumoniae, 360 Haemophilus influenzae, 216 Moraxella catarrhalis, 5 Streptococcus agalactiae, and 14 Escherichia coli). The ratio of penicillin-resistant S. pneumoniae was 0% based on CLSI M100-ED29 criteria. However, three meropenem or tosufloxacin resistant S. pneumoniae isolates were obtained. Among H. influenzae, 13.1% of them were found to be β-lactamase-producing ampicillin resistant strains, while 20.8% were β-lactamase non-producing ampicillin-resistant strains. No capsular type b strains were detected. In M. catarrhalis, 99.5% of the isolates were β-lactamase-producing strains. All S. agalactiae and E. coli strains were isolated from sterile body sites (blood or cerebrospinal fluid). The ratio of penicillin-resistant S. agalactiae was 0%, while that of extended spectrum β-lactamase-producing E. coli was 14.3%.

First report on multidrug-resistant non-encapsulated Streptococcus pneumoniae isolated from a patient with pneumonia

The non-encapsulated Streptococcus pneumoniae (NESp) has emerged and increased in the clinical setting. The majority of NESp strains have been isolated from the nasopharynxes of healthy carriers and from respiratory specimens of patients with otitis media. NESp strains were shown to be more effective than encapsulated counterparts at forming biofilms. Therefore, NESp should become one of the leading causes of emerging refractory respiratory disease after the introduction of pneumococcal conjugate vaccines. We report the first case of multidrug-resistant - including fluoroquinolone-resistant - NESp isolated from the intrabronchial aspirate of a patient with pneumonia. Drug-resistant NESp infections can possibly emerge as a clinical problem and thus the continuous monitoring of NESp infections is of utmost importance.

Panel 7 - Pathogenesis of otitis media - a review of the literature between 2015 and 2019

OBJECTIVE

To perform a comprehensive review of the literature from July 2015 to June 2019 on the pathogenesis of otitis media. Bacteria, viruses and the role of the microbiome as well as the host response are discussed. Directions for future research are also suggested.

DATA SOURCES

PubMed database of the National Library of Medicine.

REVIEW METHODS

PubMed was searched for any papers pertaining to OM pathogenesis between July 2015 and June 2019. If in English, abstracts were assessed individually for their relevance and included in the report. Members of the panel drafted the report based on these searches and on new data presented at the 20th International Symposium on Recent Advances in Otitis Media.

CONCLUSIONS

The main themes that arose in OM pathogenesis were around the need for symptomatic viral infections to develop disease. Different populations potentially having different mechanisms of pathogenesis. Novel bacterial otopathogens are emerging and need to be monitored. Animal models need to continue to be developed and used to understand disease pathogenesis.

IMPLICATIONS FOR PRACTICE

The findings in the pathogenesis panel have several implications for both research and clinical practice. The most urgent areas appear to be to continue monitoring the emergence of novel otopathogens, and the need to develop prevention and preventative therapies that do not rely on antibiotics and protect against the development of the initial OM episode.

Molecular typing, antibiotic susceptibility, and biofilm production in nonencapsulated Streptococcus pneumoniae isolated from children in Japan

The prevalence of nonencapsulated Streptococcus pneumoniae (NESp) has increased with the introduction of pneumococcal conjugate vaccines in children; however, the bacteriological characteristics of NESp have not been sufficiently clarified. In this study, NESp strains isolated from the nasopharyngeal carriage of children from four nursery schools in Japan were analyzed for molecular type, antibiotic susceptibility, and biofilm productivity. A total of 152 putative S. pneumoniae strains were identified by optochin-susceptibility analysis, of which 21 were not serotypeable by slide agglutination, quellung reaction, or multiplex PCR. Among these 21 strains, three were lytA-negative and, therefore, not S. pneumoniae. The remaining 18 strains were positive for lytA, ply, pspK, and bile solubility and were confirmed as NESp. Therefore, the isolation rate of NESp in the S. pneumoniae strains in this study was 12.0% (18/149). Molecular-typing analyses classified five strains as two existing sequence types (STs; ST7502 and ST7786), and 13 strains formed four novel STs. Horizontal spread was suspected, because strains with the same ST were often isolated from the same nursery school. The NESp isolates were generally susceptible to most antimicrobials, with the exception of macrolides; however, all isolates possessed more than one abnormal penicillin-binding protein gene. Furthermore, NESp strains were more effective than encapsulated counterparts at forming biofilms, which showed obvious differences in morphology. These data indicated that NESp strains should be continuously monitored as emerging respiratory pathogens.

Emergence of Haemophilus influenzae with low susceptibility to quinolones and persistence in tosufloxacin treatment

BACKGROUND

The use of non-β-lactam agents has increased in Japan due to the prevalence of β-lactam-resistant pathogens. This study aimed to clarify the recent trend of antimicrobial susceptibility and molecular epidemiological features in Haemophilus influenzae.

METHODS

Fifty-seven Haemophilus influenzae isolated from a Japanese teaching hospital in 2017 were characterised, and the data were compared with those of a previous study. The MICs were determined using the broth dilution method. Genetic backgrounds were compared by multilocus sequence typing. The bactericidal activity of tosufloxacin at, or near, the therapeutic Cmax was determined in vitro, with susceptible isolates and quinolone low-susceptible isolates by time-kill assay.

RESULTS

The results of the susceptibility tests showed that >90% of isolates were susceptible to cephalosporins and carbapenems, whereas ampicillin-susceptible and clarithromycin-susceptible isolates decreased. Regarding quinolones, low-susceptible isolates were noted in 2017, although all isolates were judged as susceptible. All low-susceptible isolates had an amino acid substitution in GyrA, and two isolates had an additional substitution in ParC. These isolates had different genetic backgrounds. Furthermore, the time-kill kinetic assay using the Cmax of tosufloxacin indicated that the low-susceptible isolates could persist for at least 8hours.

CONCLUSIONS

This study revealed that Haemophilus influenzae has demonstrated multidrug low-susceptibility in recent years. The low-susceptible isolates had genetic diversity, meaning that resistance occurred independently.

Double-Serine Fluoroquinolone Resistance Mutations Advance Major International Clones and Lineages of Various Multi-Drug Resistant Bacteria

The major international sequence types/lineages of methicillin-resistant Staphylococcus aureus (MRSA), extended-spectrum β-lactamase (ESBL)-producing Klebsiella pneumoniae and ESBL-producing E. coli were demonstrated to have been advanced by favorable fitness balance associated with high-level resistance to fluoroquinolones. The paper shows that favorable fitness in the major STs/lineages of these pathogens was principally attained by the capacity of evolving mutations in the fluoroquinolone-binding serine residues of both the DNA gyrase and topoisomerase IV enzymes. The available information on fitness balance incurred by individual and various combinations of mutations in the enzymes is reviewed in multiple species. Moreover, strong circumstantial evidence is presented that major STs/lineages of other multi-drug resistant bacteria, primarily vancomycin-resistant Enterococcus faecium (VRE), emerged by a similar mechanism. The reason(s) why the major ST/lineage strains of various pathogens proved more adept at evolving favorable mutations than most isolates of the same species remains to be elucidated.