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).

Molecular characterization of decreased susceptibility to ceftriaxone and genotyping of Neisseria gonorrheae isolates in New Delhi, India

Data on genetic characteristics of Neisseria gonorrhoeae isolates exhibiting decreased susceptibility to extended-spectrum cephalosporins in India is deficient. In this study, we have sequenced penA, porB, mtrR and ponA and bla_TEM genes in 70 clinical isolates of NG with varying ceftriaxone MICs. Amongst these, 22 (31.4%) were PPNG. Additionally, N. gonorrheae Multiantigen Sequence Typing was performed. Fisher exact and χ² were used to evaluate significance of mutations with MICs. A total of six non-mosaic penA (Penicillin binding protein 2 [PBP2]) amino acid patterns were seen (II, IV, IX, XII, XIX, XXII) of which, pattern IX was significantly associated with decreased susceptibility to ceftriaxone. Other significant associations were noted in porB & mtrR genes. There were no mutations in bla_TEM gene. ST6069 was significantly associated with decreased susceptibility to ceftriaxone. To conclude, development of decreased susceptibility to ceftriaxone in gonococci involves cumulation of different mutations in the four chromosomal genes investigated.

Genetic characterization of coliform bacterial isolates from environmental water in Thailand

INTRODUCTION

In contrast to the study in other part of the world, information about characteristics of plasmids carrying antimicrobial resistance genes (ARGs) in Enterobacteriaceae derived from environmental water in tropical Asian countries including Thailand is limited. This study, therefore, aimed to gain insight into genetic information of antimicrobial resistance in environmental water in Thailand.

METHODS

Coliform bacteria were isolated from environmental water collected at 20 locations in Thailand and identified. Then, susceptibility profiles to ampicillin, cefazoline, cefotaxime, kanamycin, ciprofloxacin, sulfamethoxazole, tetracycline, and nalidixic acid were assessed. In addition, antimicrobial resistant genes integrons, and replicon types were analyzed. And furthermore, plasmids carrying bla_TEM and tetM were identified by S1-PFGE analysis and confirmed transmissibility by transconjugation experiments.

RESULTS

In 130 coliform bacteria isolated, 89 were resistant to cefazoline while 41 isolates were susceptible. Cefazoline-resistant coliform bacteria were found to be significantly resistant to cefotaxime and tetracycline as compared to susceptible isolates. Hence, bla_TEM and tetM correlating with β-lactam antibiotics and tetracycline, respectively, were analyzed found to co-localize on the IncFrepB plasmids in isolates from pig farms' wastewater by S1-PFGE analysis. And furthermore, transmissibility of the plasmids was confirmed.

CONCLUSIONS

Results obtained in this study suggested that ARGs in coliform bacteria may have been spreading on the farm via IncFrepB plasmids. Hence, appropriate use of antimicrobials and good hygiene management on the farm are required to prevent the emergence and spread of resistant bacteria.

IncFII plasmid carrying antimicrobial resistance genes in Shigella flexneri: Vehicle for dissemination

OBJECTIVES

Plasmids harbouring antimicrobial resistance determinants in clinical strains are a significant public-health concern worldwide. The present study investigated such plasmids in clinical isolates of Shigella flexneri.

METHODS

A total of 162 Shigella isolates were obtained from stool specimens in the year 2015. Among the 70 multidrug-resistant (MDR) Shigella spp., 27 S. flexneri isolates were randomly selected for further characterisation. Antimicrobial resistance genes (ARGs) and plasmid incompatibility (Inc) types were analysed.

RESULTS

IncFII plasmids were found in 63% (17/27) of the studied S. flexneri isolates. ARGs such as dhfr1a (81%), sulII (74%), bla_OXA (74%), bla_TEM (33%), bla_AmpC (30%), qnrS (15%) and qnrB (4%) were identified by PCR, whereas bla_CTX-M was not detected. Next-generation sequencing of a representative S. flexneri IncFII-type plasmid (pSF470) revealed the presence of bla_TEM1-B, bla_DHA-1, qnrB10, mphA, sulI, sulII, strA, strB and tetR ARGs along with the intI1 integrase gene. In addition, pMLST analysis showed that the replicon belonged to F2:A-:B- type.

CONCLUSIONS

This study helps to know the prevalent plasmid types in MDR Shigella isolates and will improve our understanding of resistance dissemination among enteric bacteria. ARGs in plasmids further highlight the importance of such studies in enteric bacteria.

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

Background

We investigated the molecular epidemiological characteristics and antimicrobial susceptibility pattern of penicillinase-producing Neisseria gonorrhoeae (PPNG) isolates to monitor the change in distribution of bla_TEM in Korea.

Methods

We collected 804 PPNG isolates from diverse hospitals and clinics mainly located in Seoul, Korea, over a period of 11 years (2005–2015). Isolate susceptibility to seven antimicrobials was determined using the agar dilution test. The molecular epidemiological characteristics of the isolates were determined by Sanger sequencing of bla_TEM, N. gonorrhoeae multiantigen sequence typing (NG-MAST) and plasmid typing.

Results

Among 72 fully sequenced PPNG isolates, sixteen (22.2%) possessed TEM-135. All TEM-135 isolates had a common silent mutation (c.18C>T), which was previously unreported. We observed a pattern of continuous increase in the number of TEM-135 isolates since 2012. The median and 90% minimum inhibitory concentration of azithromycin were substantially lower in the TEM-135 group than in the non-PPNG and TEM-1 groups. All TEM-135 isolates showed different NG-MAST types and predominantly harbored Toronto/Rio (75%) plasmids. A comprehensive comparative analysis of PPNG with TEM-135 according to NG-MAST, plasmid type, and year of isolation revealed a wide distribution.

Conclusions

The proportion of TEM-135 PPNG has continuously increased since 2012, in association with clonal spread. The difference at position 18 of the TEM-135 sequence can be interpreted as the existence of multiple clonal complexes. The possibility that TEM-135 was acquired via foreign plasmids requires careful follow-up and continuous monitoring of TEM-135 to ascertain whether it constitutes a step towards evolutionary change.

Antimicrobial resistance and genetic diversity of Salmonella Infantis isolated from foods and human samples in Morocco

OBJECTIVES

Genotyping of Salmonella strains is an important molecular tool to discriminate isolates and to improve epidemiological studies when an outbreak occurs. Among the DNA-based genotyping methods, pulsed-field gel electrophoresis (PFGE) is currently used to subtype Salmonella isolates. In this study, the feasibility of genotyping Salmonella enterica serotype Infantis strains using XbaI restriction enzyme was evaluated. Separation of restricted fragments was performed by PFGE.

METHODS

To test the possibility of applying this methodology to epidemiological investigation, a collection of 26 Salmonella Infantis strains were tested for their susceptibility to 14 antimicrobial agents and were analysed by XbaI macrorestriction followed by PFGE. Detection of class 1 integrons as well as intI1 and bla_TEM genes in resistant strains was also studied.

RESULTS

Antimicrobial susceptibility testing showed that 84.6% (22/26) of Salmonella Infantis isolates were susceptible to all of the antimicrobials tested, whereas 7.7% (2/26) had low-level resistance to β-lactams and harboured the bla_TEM gene. A class 1 integron (0.8kb) and the intI1 gene (898bp) were detected in one Salmonella Infantis strain. However, five different PFGE profiles were defined by XbaI macrorestriction.

CONCLUSIONS

The PFGE method demonstrated adequate typing ability and represents a powerful tool to discriminate the serotype Salmonella Infantis.

Molecular characterization of extended spectrum β-lactamase-producing Enterobacteriaceae strains isolated from a tertiary care hospital

Infectious diseases caused by ESBL producing Enterobacteriaceae are an emerging problem worldwide which increases the empirical treatment failure, hospital cost, rate of morbidity and mortality. This also leads to the Hospital infection outbreak. Present study was undertaken to determine the frequency of bla_TEM, bla_CTX-M and bla_SHV genes among Enterobacteriaceae. A total of 751 non-repeated clinical isolates of Enterobacteriaceae family were included in this study. Antibiotic susceptibility test was done and minimal inhibitory concentration (MIC) against four antibiotics was carried out. Five hundred fifteen multi drug resistant isolates were tested for ESBL by CLSI confirmatory method. Isolates showing ESBL positive by phenotypic method were screened for bla_TEM, bla_CTX-M and bla_SHV genes by monoplex PCR. Two bla_TEM and two bla_CTX-M amplified products were selected randomly for sequencing. Sequencing data was submitted to NCBI data base. Of the 515 MDR isolates, 140 showed ESBL production by phenotypic method. All the ESBL producing isolates showed resistant to ceftazidime (100%). IMP, TGC and CL drugs could be preferred for the treatment of ESBL producers as these drugs showed a lower rate of resistance. bla_TEM gene was the predominant (96.42%) followed by bla_CTX-M (75%) and bla_SHV (17.85%). All the three bla genes were occurred in 22 (17.14%) isolates. All the phenotypically confirmed ESBL producers were found contain any one of the three bla genes. It is concluded from the study that the bla_TEM was predominantly found in Enterobacteriaceae and bla_CTX-M gene also seemed to emerging.

The influence of the autochthonous wastewater microbiota and gene host on the fate of invasive antibiotic resistance genes

The aim of this study was to assess the fate of invasive antibiotic resistance genes (ARG) discharged in wastewater. With this objective, antibiotic resistant bacteria (ARB) known to harbor specific ARG were inoculated in wastewater (hospital effluent, or municipal raw and treated wastewater) and in ultra-pure sterile water microcosms. Two sets of wastewater ARB isolates were used - set 1, Enterococcus faecalis, Acinetobacter johnsonii, Klebsiella pneumoniae and set 2, Enterococcus faecium, Acinetobacter johnsonii, Escherichia coli. Non-inoculated controls were run in parallel. Samples were collected at the beginning and at the end (15days) of the incubation period and the abundance of the genes 16S rRNA, intI1, bla_TEM and vanA and the bacterial community composition were analyzed. In general, the genes bla_TEM and vanA had lower persistence in wastewater and in ultra-pure water than the genes 16S rRNA or the class 1 integron integrase intI1. This effect was more pronounced in wastewater than in ultra-pure water, evidencing the importance of the autochthonous microbiota on the elimination of invasive ARG. Wastewater autochthonous bacterial groups most correlated with variations of the genes intI1, bla_TEM and vanA were members of the classes Gammaproteobacteria, Bacilli or Bacteroidia. For bla_TEM, but not for vanA, the species of the ARB host was important to determine its fate. These are novel findings on the ecology of ARB in wastewater environments.

Draft genome sequence of blaTEM-1-mediated cephalosporin-resistant Salmonella enterica serovar Typhi from bloodstream infection

Enteric fever is a major cause of concern in developing countries across the globe. The primary choice of antibiotics remains fluoroquinolones, followed by cephalosporins. Resistance to third-generation cephalosporins is rarely reported in Salmonella enterica serovar Typhi. This study reports the whole genome sequence of an S. Typhi isolate resistant to cefixime [minimum inhibitory concentration (MIC)=512μg/mL] by microbroth dilution. Interestingly, the isolate was negative for the cephalosporin resistance gene bla_CTX-M by PCR, which is a known mechanism for higher cephalosporin resistance. The isolate was further subjected to next-generation sequencing that identified bla_TEM-1B and bla_DHA-1 genes in association with qnrB4 and sul1. bla_TEM is a known gene coding for β-lactam resistance. In certain cases, overexpression of bla_TEM was reported to result in cephalosporin resistance. This suggests that the high cefixime MIC would have been contributed by overexpression of bla_TEM-1B. The bla_TEM-1B gene was found to be associated with a promoter Px with -35 and -10 regions as TTAATA and TAAAGT, respectively. The promoter regions were unique, but the -10 region was similar to that found in Pa/Pb (previously reported promoter for bla_TEM) with a single nucleotide change. In addition, an IncN plasmid was identified, which is usually reported in association with the most prevalent extended-spectrum β-lactamase (ESBL), metallo- and non-metallo-carbapenemase, and plasmid-mediated quinolone resistance (PMQR) genes. Plasmids such as IncN might possibly confer resistance and enhance spread. It is imperative to continuously monitor the drug resistance profile and evolving genetic elements.

Diversity of β-lactamases produced by imipenem resistant, Pseudomonas aeruginosa isolates from the bloodstream

INTRODUCTION

The emergence of imipenem non-susceptible Pseudomonas aeruginosa isolates is a matter of great concern because these isolates can become resistant to all available antibiotics. This study conducted to characterize β-lactamase genes in imipenem resistant P. aeruginosa isolates from bloodstream.

METHODS

56 non-duplicate clinical isolates of P. aeruginosa were collected in Tehran hospitals. Antibacterial susceptibility was determined by disk diffusion and MIC methods. ESBL and MBL production was confirmed by combined disk. β-Lactamase classes A, B and D genes were identified by PCR.

RESULTS

Seventeen (30.3%) isolates were imipenem resistant for which 16 isolates simultaneously were resistant to all tested antibiotics. While among 39 imipenem susceptible isolates, only two isolates were resistant to all tested antibiotics. In imipenem resistant isolates, blaTEM, blaSHV and blaOXA-10 were found in 41.1% of isolates and blaVIM, blaIMP and blaPER were identified in 47%, 11.7% and 5.8% of isolates respectively, while in imipenem susceptible isolates, blaTEM, blaSHV and blaOXA-10 were determined in 2.5%, 7.6% and 33.3% of isolates, respectively. The imipenem resistant isolates had been recovered mostly (67.7%) from patients in the Burn hospital.

CONCLUSION

The result of this study indicated the emergence of multidrug resistant MBL and non-MBL producing P. aeruginosa, particularly in the Burn hospital and blaVIM was dominant β-lactamase genes in imipenem resistant isolates. The isolation of carrier patients may lead to prevent a further dissemination.