Recent Increase in the Incidence of TEM-135 β-Lactamase-harboring Neisseria gonorrhoeae in Korea

Rejuvenating the Activity of Usual Antibiotics on Resistant Gram-Negative Bacteria: Recent Issues and Perspectives

Antibiotic resistance continues to evolve and spread beyond all boundaries, resulting in an increase in morbidity and mortality for non-curable infectious diseases. Due to the failure of conventional antimicrobial therapy and the lack of introduction of a novel class of antibiotics, novel strategies have recently emerged to combat these multidrug-resistant infectious microorganisms. In this review, we highlight the development of effective antibiotic combinations and of antibiotics with non-antibiotic activity-enhancing compounds to address the widespread emergence of antibiotic-resistant strains.

Molecular epidemiology of penicillinase-producing <i>Neisseria gonorrhoeae</i> isolates and their <i>bla</i>_TEM-135 gene variant in Bangkok, Thailand, 2015–2017

Penicillinase-producing Neisseria gonorrhoeae (PPNG) possessing bla_TEM-135 is a serious public health threat. With only a single change in the amino acid sequence, bla_TEM-135 could evolve into a TEM-type extended-spectrum beta-lactamase (ESBL), which hydrolyzes extended-spectrum cephalosporins, including ceftriaxone and cefixime. We investigated the molecular epidemiological characteristics, types of plasmids in PPNG isolates, and prevalence of PPNG clinical isolates producing TEM-135 beta-lactamases. N. gonorrhoeae multi-antigen sequence typing (NG-MAST) was used to determine the molecular epidemiological characteristics of 99 PPNG isolates collected from 2015 to 2017. A mismatch amplification mutation assay was used to examine the bla_TEM-135 gene prevalence. Of the 89 identified NG-MAST sequence types, 65 (73.0%) were novel. Only 17.7% (43/243) of PPNG isolates belonged to 16 genogroups. The most frequent plasmid was African, followed by Rio/Toronto, and Asian. The bla_TEM-135 allele was found in Rio/Toronto plasmids. The bla_TEM-135 allele was present in 23.2% (23/99) of the PPNG isolates. PPNG isolates expressing TEM-135 beta-lactamase exhibited significantly higher penicillin MIC (minimum inhibitory concentration) values than TEM-1 PPNG isolates. The PPNG isolates showed high genetic diversity and a high proportion of bla_TEM-135 alleles. Mutation of the bla_TEM-135 allele is worrisome as only one mutation could cause TEM-1 to evolve into an ESBL variant that degrades ceftriaxone. Ongoing surveillance of bla_TEM-135 and new PPNG isolates is imperative.

High prevalence of blaTEM-135 and genetic epidemiology of blaTEM-135-carrying Neisseria gonorrhoeae isolates in Shandong, China, 2017-19

BACKGROUND

Only one additional specific SNP in blaTEM-135 in penicillinase-producing Neisseria gonorrhoeae (PPNG) isolates is required for TEM-135 to evolve into an ESBL that is capable of degrading all extended-spectrum cephalosporins (ESCs).

METHODS

Identification of the blaTEM-135 gene was achieved by performing a mismatch amplification mutation assay PCR. PPNG isolates were then genotyped using MLST and N. gonorrhoeae multiantigen sequence typing (NG-MAST) techniques. Finally, phylogenetic analyses based on MLST and NG-MAST were performed on all of the PPNG isolates, and genogroups were classified according to the phylogenetic relatedness on the basis of each MLST and NG-MAST gene typing and the blaTEM allele varieties.

RESULTS

Among the 197 PPNG isolates, one (0.5%) isolate possessed the blaTEM-220 allele, 90 (45.7%) possessed the blaTEM-135 allele, and 106 (53.8%) possessed the blaTEM-1 allele. Among the blaTEM-135-carrying PPNG isolates, MLST ST8109 (n = 30) and NG-MAST ST12199 (n = 5), ST12754 (n = 5) and ST15073 (n = 5) were the most prevalent in the Shandong province of China. The phylogenetic analyses revealed that MLST ST8109, ST8140 and ST14417, mainly carrying the blaTEM-135 allele, belonged to the same genogroup, G1, while NG-MAST ST12199 and ST15073, mainly carrying the blaTEM-135 allele, belonged to the same genogroup, Ga.

CONCLUSIONS

This study has shown that the molecular epidemiology of PPNG isolates carrying the blaTEM-135 allele in Shandong has a dynamically changing status. Therefore, it is very pressing to continuously monitor the prevalence and mutation of the blaTEM-135 allele and the genetic epidemiology of PPNG isolates carrying the blaTEM-135 allele in this district.

Molecular characteristics and antimicrobial susceptibility of penicillinase-producing Neisseria gonorrhoeae isolates in Fukuoka, Japan, 1996-2018

OBJECTIVES

The objective of this study was to investigate the molecular characteristics and antimicrobial susceptibility of penicillinase-producing Neisseria gonorrhoeae (PPNG) isolates collected in Fukuoka, Japan, from 1996-2018.

METHODS

Antimicrobial susceptibility to seven antibiotics was determined by the agar dilution method. Molecular characteristics were determined by Sanger sequencing of the bla_TEM allele, plasmid typing and N. gonorrhoeae multiantigen sequence typing (NG-MAST). Furthermore, full sequences of the penA gene, encoding penicillin-binding protein 2 (PBP2), of PPNG isolates with reduced susceptibility to cefixime were analysed.

RESULTS

Among 50 PPNG isolates, 17 and 33 were collected during 1996-2006 and 2007-2018, respectively. In 1996-2006, bla_TEM-1 in African plasmid was most frequent (64.7%), followed by bla_TEM-1 in Asian plasmid (29.4%) and bla_TEM-135 in Toronto/Rio plasmid (5.9%). In 2007-2018, bla_TEM-135 in Toronto/Rio plasmid was predominant (54.5%), followed by bla_TEM-1 in African plasmid (36.4%) and bla_TEM-135 in Asian plasmid (6.1%). Among isolates with the bla_TEM-135-carrying Toronto/Rio plasmid in 2007-2018, a novel genogroup G15576 was predominant (66.7%). Isolates with the TEM-135 β-lactamase were more resistant to ciprofloxacin but were more susceptible to ceftriaxone and tetracycline than isolates with TEM-1. Seven PPNG isolates less susceptible to cefixime possessed the plasmidic bla_TEM-1 allele and had mosaic or non-mosaic alterations within PBP2.

CONCLUSION

The proportion of PPNG with the bla_TEM135-carrying Toronto/Rio plasmid increased during the last 12 years. The increase in PPNG carrying the bla_TEM-135 allele is of particular concern as it is considered a possible direct precursor of an extended-spectrum β-lactamase (ESBL).

Role of Synonymous Mutations in the Evolution of TEM β-Lactamase Genes

Nonsynonymous mutations are well documented in TEM β-lactamases. The resulting amino acid changes often alter the conferred phenotype from broad spectrum (2b) conferred by TEM-1 to extended spectrum (2be), inhibitor resistant (2br), or both extended spectrum and inhibitor resistant (2ber). The encoding bla _TEM genes also deviate in numerous synonymous mutations, which are not well understood. bla _TEM-3 (2be), bla _TEM-33 (2br), and bla _TEM-109 (2ber) were studied in comparison to bla _TEM-1 bla _TEM-33 was chosen for more detailed studies because it deviates from bla _TEM-1 by a single nonsynonymous mutation and three additional synonymous mutations. Genes encoding the enzymes with only nonsynonymous or all (including synonymous) mutations plus all permutations between bla _TEM-1 and bla _TEM-33 were expressed in Escherichia coli cells. In disc diffusion assays, genes encoding TEM-3, TEM-33, and TEM-109 with all synonymous mutations resulted in higher resistance levels than genes without synonymous mutations. Disc diffusion assays with the 16 genes carrying all possible nucleotide change combinations between bla _TEM-1 and bla _TEM-33 indicated different susceptibilities for different variants. Nucleotide BLAST searches did not identify genes without synonymous mutations but did identify some without nonsynonymous mutations. Energies of possible secondary mRNA structures calculated with mfold are generally higher with synonymous mutations, suggesting that their role could be to destabilize the mRNA and facilitate its unfolding for efficient translation. In summary, our data indicate that transition from bla _TEM-1 to other variant genes by simply acquiring the nonsynonymous mutations is not favored. Instead, synonymous mutations seem to support the transition to other variant genes with nonsynonymous mutations leading to different phenotypes.