The Molecular Epidemiology and Genetic Environment of Carbapenemases Detected in Africa

Occurrence of beta-lactamases in bacteria

Our study highlights the escalating issue of beta-lactam resistance in nosocomial pathogens, driven by the broad spectrum of antibiotic-degrading enzymes and plasmid exchange. We catalogued known beta-lactamases across 230 bacterial genera, identified 2349 potential beta-lactamases across over 673 genera, and anticipate discovering many new types, underscoring the need for targeted gene analysis in combating resistance. This study also elucidates the complex relationship between the diversity and frequency of beta-lactamase genes across bacterial genera, highlighting the need for genus-specific approaches in combating antibiotic resistance and emphasizing these genes' significant global distribution and host-specific prevalence. We report many transcriptional regulators, transposases and other factors in the genomes of 20 different bacterial isolates, some of which are consistent with the ability of these species to adapt to different environments. Although we could not determine precisely which factors regulate the presence of beta-lactamases in specific bacteria, we found that the proportion of regulatory genes, the size of the genome, and other factors are not decisive. Further studies are needed to elucidate key aspects of this process.

Emergence of carbapenem resistant gram-negative pathogens with high rate of colistin resistance in Egypt: A cross sectional study to assess resistance trends during the COVID-19 pandemic

The current study investigated the temporal phenotypic and genotypic antimicrobial resistance (AMR) trends among multi-drug resistant and carbapenem-resistant Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa recovered from Egyptian clinical settings between 2020 and 2021. Bacterial identification and antimicrobial sensitivity of 111 clinical isolates against a panel of antibiotics were performed. Molecular screening for antibiotic resistance determinants along with integrons and associated gene cassettes was implemented. An alarming rate (98.2%) of these isolates were found to be phenotypically resistant to carbapenem. Although 23.9 % K. pneumoniae isolates were phenotypically resistant to colistin, no mobile colistin resistance (mcr) genes were detected. Among carbapenem-resistant isolates, blaNDM and blaOXA-48-like were the most prevalent genetic determinants and were significantly overrepresented among K. pneumoniae. Furthermore, 84.78% of K. pneumoniae isolates co-produced these two carbapenemase genes. The plasmid-mediated quinolone resistance genes (qnrS and qnrB) were detected among the bacterial species and were significantly more prevalent among K. pneumoniae. Moreover, Class 1 integron was detected in 82% of the bacterial isolates. This study alarmingly reveals elevated resistance to last-resort antibiotics such as carbapenems as well as colistin which impose a considerable burden in the health care settings in Egypt. Our future work will implement high throughput sequencing-based antimicrobial resistance surveillance analysis for characterization of novel AMR determinants. This information could be applied as a step forward to establish a robust antibiotic stewardship program in Egyptian clinical settings, thereby addressing the rising challenges of AMR.

Molecular epidemiology of antimicrobial resistance in central africa: A systematic review

Background

In Central Africa, it is difficult to tackle antibiotic resistance, because of a lack of data and information on bacterial resistance, due to the low number of studies carried out in the field. To fill this gap, we carried out a systematic review of the various studies, and devised a molecular epidemiology of antimicrobial resistance from humans, animals and the environmental samples.

Method

A systematic search of all publications from 2005 to 2020 on bacterial resistance in Central Africa (Gabon, Cameroon, Democratic Republic of Congo, Central African Republic, Chad, Republic of Congo, Equatorial Guinea, São Tomé and Príncipe, Angola) was performed on Pubmed, Google scholar and African Journals Online (AJOL). All circulating resistance genes, prevalence and genetic carriers of these resistances were collected. The study area was limited to the nine countries of Central Africa.

Results

A total of 517 studies were identified through a literature search, and 60 studies carried out in eight countries were included. Among all articles included, 43 articles were from humans. Our study revealed not only the circulation of beta-lactamase and carbapenemase genes, but also several other types of resistance genes. To finish, we noticed that some studies reported mobile genetic elements such as integrons, transposons, and plasmids.

Conclusion

The scarcity of data poses difficulties in the implementation of effective strategies against antibiotic resistance, which requires a health policy in a 'One Health' approach.

A systematic review of the current status of carbapenem resistance in Nigeria: Its public health implication for national intervention

Carbapenem antibiotics are considered one of the most effective and the last-resort antibiotics for the treatment of infections caused by multidrug-resistant Gram-negative bacteria. However, with the advent of carbapenem resistance, it becomes obvious that quality health-care delivery will be hampered if adequate measure is not put in place. This review assessed the prevalence of carbapenem-resistant Gram-negative bacteria (CR-GNB) and also provided an up-to-date position on carbapenem resistance (CR) in Nigeria. Three electronic databases (Google Scholar, PubMed and African Journal online) were searched for relevant literatures, and 38 articles published between January 2013 and June 2022 that met the criteria for inclusion were recruited into the study. The mean prevalence of CR in Nigeria stands at 21.3%, with the southern and northern regions documenting a mean prevalence of 22.0% and 20.9%, respectively. Most of the reviewed articles were from clinical settings (81.6%), with urine samples (38.7%) constituting the most prevalent clinical sample in which CR-GNB were detected. The preponderance of phenotypic methods (55.3%) over molecular method (44.7%), particularly the use of disk diffusion test breakpoint and Modified Hodge test was documented. The most prevalent carbapenem-resistant bacteria were Escherichia coli (50.0%) and Klebsiella pneumoniae (26.3%). The blaNDM and blaVIM were the major reported carbapenemase-encoded genes, particularly among E. coli, K. pneumoniae and Pseudomonas species. This systematic review revealed a mean prevalence of CR-GNB in Nigeria that required urgent attention. Furthermore, the detection of clinically and epidemiologically important carbapenemase coding genes is of public health importance.

Beta-lactamase resistance genes in Enterobacteriaceae from Nigeria

Background

Beta-lactamase genes are one of the most important groups of antimicrobial resistance genes in human and animal health. Therefore, continuous surveillance of this group of resistance genes is needed for a better understanding of the local epidemiology within a country and global dissemination.

Aim

This review was carried out to identify different beta-lactamase resistance genes reported in published literature from Nigeria.

Methods

Systematic review and meta-analysis was carried out on eligible Nigerian articles retrieved from electronic literature searches of PubMed^®, African Journals Online, and Google Scholar published between January 1990 and December 2019. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses method was adopted to facilitate clarity and transparency in reporting review findings.

Results

Fifty-seven articles were included. All beta-lactamases reported were detected from Gram-negative bacteria, particularly from Enterobacteriaceae. Thirty-six different beta-lactamase genes were reported in Nigeria. These genes belong to the narrow-spectrum, AmpC, extended-spectrum and carbapenemase beta-lactamase resistance genes. The pooled proportion estimate of extended-spectrum beta-lactamase genes in Nigeria was 31% (95% confidence interval [CI]: 26% – 36%, p < 0.0001), while the estimate of the bla_CTX-M-15 gene in Nigeria was 46% (95% CI: 36% – 57%, p < 0.0001). The proportion estimate of AmpC genes was 32% (95% CI: 11% – 52%, p < 0.001), while the estimate for carbapenemases was 8% (95% CI: 5% – 12%, p < 0.001).

Conclusion

This study provides information on beta-lactamase distribution in Nigeria. This is necessary for a better understanding of molecular epidemiology of clinically important beta-lactamases, especially the extended-spectrum beta-lactamases and carbapenemases in Nigeria.

Infections Due to Acinetobacter baumannii-calcoaceticus Complex: Escalation of Antimicrobial Resistance and Evolving Treatment Options

Bacteria within the genus Acinetobacter (principally A. baumannii-calcoaceticus complex [ABC]) are gram-negative coccobacilli that most often cause infections in nosocomial settings. Community-acquired infections are rare, but may occur in patients with comorbidities, advanced age, diabetes mellitus, chronic lung or renal disease, malignancy, or impaired immunity. Most common sites of infections include blood stream, skin/soft-tissue/surgical wounds, ventilator-associated pneumonia, orthopaedic or neurosurgical procedures, and urinary tract. Acinetobacter species are intrinsically resistant to multiple antimicrobials, and have a remarkable ability to acquire new resistance determinants via plasmids, transposons, integrons, and resistance islands. Since the 1990s, antimicrobial resistance (AMR) has escalated dramatically among ABC. Global spread of multidrug-resistant (MDR)-ABC strains reflects dissemination of a few clones between hospitals, geographic regions, and continents; excessive antibiotic use amplifies this spread. Many isolates are resistant to all antimicrobials except colistimethate sodium and tetracyclines (minocycline or tigecycline); some infections are untreatable with existing antimicrobial agents. AMR poses a serious threat to effectively treat or prevent ABC infections. Strategies to curtail environmental colonization with MDR-ABC require aggressive infection-control efforts and cohorting of infected patients. Thoughtful antibiotic strategies are essential to limit the spread of MDR-ABC. Optimal therapy will likely require combination antimicrobial therapy with existing antibiotics as well as development of novel antibiotic classes.

Genetic support of carbapenemases: a One Health systematic review and meta-analysis of current trends in Africa

Antimicrobial resistance (AMR) is a public health threat globally. Carbapenems are β-lactam antibiotics used as last-resort agents for treating antibiotic-resistant infections. Mobile genetic elements (MGEs) play an important role in the dissemination and expression of antimicrobial resistance genes (ARGs), including the mobilization of ARGs within and between species. The presence of MGEs around carbapenem-hydrolyzing enzymes, called carbapenemases, in bacterial isolates in Africa is concerning. The association between MGEs and carbapenemases is described herein. Specific plasmid replicons, integrons, transposons, and insertion sequences were found flanking specific and different carbapenemases across the same and different clones and species isolated from humans, animals, and the environment. Notably, similar genetic contexts have been reported in non-African countries, supporting the importance of MGEs in driving the intra- and interclonal and species transmission of carbapenemases in Africa and globally. Technical and budgetary limitations remain challenges for epidemiological analysis of carbapenemases in Africa, as studies undertaken with whole-genome sequencing remained relatively few. Characterization of MGEs in antibiotic-resistant infections can deepen our understanding of carbapenemase epidemiology and facilitate the control of AMR in Africa. Investment in genomic epidemiology will facilitate faster clinical interventions and containment of outbreaks.

Co-Existence of Certain ESBLs, MBLs and Plasmid Mediated Quinolone Resistance Genes among MDR E. coli Isolated from Different Clinical Specimens in Egypt

The emergence of multi-drug resistant (MDR) strains and even pan drug resistant (PDR) strains is alarming. In this study, we studied the resistance pattern of E. coli pathogens recovered from patients with different infections in different hospitals in Minia, Egypt and the co-existence of different resistance determinants. E. coli was the most prevalent among patients suffering from urinary tract infections (62%), while they were the least isolated from eye infections (10%). High prevalence of MDR isolates was found (73%) associated with high ESBLs and MBLs production (89.4% and 64.8%, respectively). bla_TEM (80%) and bla_NDM (43%) were the most frequent ESBL and MBL, respectively. None of the isolates harbored bla_KPC and bla_OXA-48 carbapenemase like genes. Also, the fluoroquinolone modifying enzyme gene aac-(6′)-Ib-cr was detected in 25.2% of the isolates. More than one gene was found in 81% of the isolates. Azithromycin was one of the most effective antibiotics against MDR E. coli pathogens. The high MAR index of the isolates and the high prevalence of resistance genes, indicates an important public health concern and high-risk communities where antibiotics are abused.

Klebsiella spp. cause severe and fatal disease in Mozambican children: antimicrobial resistance profile and molecular characterization

Background

Klebsiella spp. are important pathogens associated with bacteremia among admitted children and is among the leading cause of death in children < 5 years in postmortem studies, supporting a larger role than previously considered in childhood mortality. Herein, we compared the antimicrobial susceptibility, mechanisms of resistance, and the virulence profile of Klebsiella spp. from admitted and postmortem children.

Methods

Antimicrobial susceptibility and virulence factors of Klebsiella spp. recovered from blood samples collected upon admission to the hospital (n = 88) and postmortem blood (n = 23) from children < 5 years were assessed by disk diffusion and multiplex PCR.

Results

Klebsiella isolates from postmortem blood were likely to be ceftriaxone resistant (69.6%, 16/23 vs. 48.9%, 43/88, p = 0.045) or extended-spectrum β-lactamase (ESBL) producers (60.9%, 14/23 vs. 25%, 22/88, p = 0.001) compared to those from admitted children. bla_CTX-M-15 was the most frequent ESBL gene: 65.3%, 9/14 in postmortem isolates and 22.7% (5/22) from admitted children. We found higher frequency of genes associated with hypermucoviscosity phenotype and invasin in postmortem isolates than those from admitted children: rmpA (30.4%; 7/23 vs. 9.1%, 8/88, p = 0.011), wzi-K1 (34.7%; 8/23 vs. 8%; 7/88, p = 0.002) and traT (60.8%; 14/23 vs. 10.2%; 9/88, p < 0.0001), respectively. Additionally, serine protease auto-transporters of Enterobacteriaceae were detected from 1.8% (pic) to 12.6% (pet) among all isolates. Klebsiella case fatality rate was 30.7% (23/75).

Conclusion

Multidrug resistant Klebsiella spp. harboring genes associated with hypermucoviscosity phenotype has emerged in Mozambique causing invasive fatal disease in children; highlighting the urgent need for prompt diagnosis, appropriate treatment and effective preventive measures for infection control.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-06245-x.

Mechanistic Insight into Antimicrobial and Antioxidant Potential of Jasminum Species: A Herbal Approach for Disease Management

Drug resistance among microbial pathogens and oxidative stress caused by reactive oxygen species are two of the most challenging global issues. Firstly, drug-resistant pathogens cause several fatalities every year. Secondly aging and a variety of diseases, such as cardiovascular disease and cancer, are associated with free radical generated oxidative stress. The treatments currently available are limited, ineffective, or less efficient, so there is an immediate need to tackle these issues by looking for new therapies to resolve resistance and neutralize the harmful effects of free radicals. In the 21st century, the best way to save humans from them could be by using plants as well as their bioactive constituents. In this specific context, Jasminum is a major plant genus that is used in the Ayurvedic system of medicine to treat a variety of ailments. The information in this review was gathered from a variety of sources, including books, websites, and databases such as Science Direct, PubMed, and Google Scholar. In this review, a total of 14 species of Jasminum have been found to be efficient and effective against a wide variety of microbial pathogens. In addition, 14 species were found to be active free radical scavengers. The review is also focused on the disorders related to oxidative stress, and it was concluded that Jasminum grandiflorum and J. sambac normalized various parameters that were elevated by free radical generation. Alkaloids, flavonoids (rutoside), terpenes, phenols, and iridoid glucosides are among the main phytoconstituents found in various Jasminum species. Furthermore, this review also provides insight into the mechanistic basis of drug resistance, the generation of free radicals, and the role of Jasminum plants in combating resistance and neutralizing free radicals.

Molecular Characterization of Carbapenemase-Producing Klebsiella pneumoniae Isolated from Egyptian Pediatric Cancer Patients Including a Strain with a Rare Gene-Combination of β-Lactamases

PURPOSE

Healthcare-associated infections caused by multi-drug-resistant (MDR) pathogens are a global threat. We aim to assess the clonal relatedness among carbapenemase-producing Klebsiella pneumoniae (CPKP) strains infecting Egyptian pediatric cancer patients.

MATERIALS AND METHODS

Identification and antimicrobial susceptibility testing of 149 Gram-negative isolates obtained from pediatric cancer patients were performed by VITEK 2. Genes encoding carbapenemases and extended-spectrum β-lactamases were detected by PCR and verified by DNA sequencing of representative samples. The transferability of the plasmids harboring bla OXA-48, from representative clinical samples, was evaluated by performing a conjugation experiment followed by PCR and MIC shift determination. Clonal relationships among the bla OXA-48-harboring K. pneumoniae isolates were determined by enterobacterial repetitive intergenic consensus (ERIC)-PCR and pulsed-field gel electrophoresis (PFGE).

RESULTS

Carbapenem resistance was observed in 59% of the isolates. The most prevalent species was K. pneumoniae (45.6%) and 57% of them were isolated from ICU. Fifty-nine % of the K. pneumoniae isolates were carbapenemase-producers and bla OXA-48 was detected in (58%) of them. One isolate co-harbored bla OXA-48, bla NDM-1, and bla IMP-1 genes for the first time in Egypt. PCR and meropenem MIC shift confirmed the success of the transferability of representative plasmids to E. coli K12. ERIC and PFGE identified 93% and 100% of the K. pneumoniae with a similarity coefficient ≥85%, respectively, including strains with indistinguishable patterns, suggesting possible clonal dissemination.

CONCLUSION

Our findings underline the dissemination of diverse clones of MDR CPKP among Egyptian pediatric cancer patients. Hence, routine molecular characterizations followed by strict implementation of infection control measures are crucial to tackling this threat.

Tigecycline antibacterial activity, clinical effectiveness, and mechanisms and epidemiology of resistance: narrative review

Tigecycline is unique glycylcycline class of semisynthetic antimicrobial agents developed for the treatment of polymicrobial infections caused by multidrug-resistant Gram-positive and Gram-negative pathogens. Tigecycline evades the main tetracycline resistance genetic mechanisms, such as tetracycline-specific efflux pump acquisition and ribosomal protection, via the addition of a glycyclamide moiety to the 9-position of minocycline. The use of the parenteral form of tigecycline is approved for complicated skin and skin structure infections (excluding diabetes foot infection), complicated intra-abdominal infections, and community-acquired bacterial pneumonia in adults. New evidence also suggests the effectiveness of tigecycline for the treatment of severe Clostridioides difficile infections. Tigecycline showed in vitro susceptibility to Coxiella spp., Rickettsia spp., and multidrug-resistant Neisseria gonnorrhoeae strains which indicate the possible use of tigecycline in the treatment of infections caused by these pathogens. Except for intrinsic, or often reported resistance in some Gram-negatives, tigecycline is effective against a wide range of multidrug-resistant nosocomial pathogens. Herein, we summarize the currently available data on tigecycline pharmacokinetics and pharmacodynamics, its mechanism of action, the epidemiology of tigecycline resistance, and its clinical effectiveness.

Emerging Transcriptional and Genomic Mechanisms Mediating Carbapenem and Polymyxin Resistance in Enterobacteriaceae: a Systematic Review of Current Reports

The spread of carbapenem- and polymyxin-resistant Enterobacteriaceae poses a significant threat to public health, challenging clinicians worldwide with limited therapeutic options. This review describes the current coding and noncoding genetic and transcriptional mechanisms mediating carbapenem and polymyxin resistance, respectively.

The spread of carbapenem- and polymyxin-resistant Enterobacteriaceae poses a significant threat to public health, challenging clinicians worldwide with limited therapeutic options. This review describes the current coding and noncoding genetic and transcriptional mechanisms mediating carbapenem and polymyxin resistance, respectively. A systematic review of all studies published in PubMed database between 2015 to October 2020 was performed. Journal articles evaluating carbapenem and polymyxin resistance mechanisms, respectively, were included. The search identified 171 journal articles for inclusion. Different New Delhi metallo-β-lactamase (NDM) carbapenemase variants had different transcriptional and affinity responses to different carbapenems. Mutations within the Klebsiella pneumoniae carbapenemase (KPC) mobile transposon, Tn4401, affect its promoter activity and expression levels, increasing carbapenem resistance. Insertion of IS26 in ardK increased imipenemase expression 53-fold. ompCF porin downregulation (mediated by envZ and ompR mutations), micCF small RNA hyperexpression, efflux upregulation (mediated by acrA, acrR, araC, marA, soxS, ramA, etc.), and mutations in acrAB-tolC mediated clinical carbapenem resistance when coupled with β-lactamase activity in a species-specific manner but not when acting without β-lactamases. Mutations in pmrAB, phoPQ, crrAB, and mgrB affect phosphorylation of lipid A of the lipopolysaccharide through the pmrHFIJKLM (arnBCDATEF or pbgP) cluster, leading to polymyxin resistance; mgrB inactivation also affected capsule structure. Mobile and induced mcr, efflux hyperexpression and porin downregulation, and Ecr transmembrane protein also conferred polymyxin resistance and heteroresistance. Carbapenem and polymyxin resistance is thus mediated by a diverse range of genetic and transcriptional mechanisms that are easily activated in an inducing environment. The molecular understanding of these emerging mechanisms can aid in developing new therapeutics for multidrug-resistant Enterobacteriaceae isolates.

Epigenomics, genomics, resistome, mobilome, virulome and evolutionary phylogenomics of carbapenem-resistant Klebsiella pneumoniae clinical strains

Carbapenem-resistant Klebsiella pneumoniae (CRKP) remains a major clinical pathogen and public health threat with few therapeutic options. The mobilome, resistome, methylome, virulome and phylogeography of CRKP in South Africa and globally were characterized. CRKP collected in 2018 were subjected to antimicrobial susceptibility testing, screening by multiplex PCR, genotyping by repetitive element palindromic (REP)-PCR, plasmid size, number, incompatibility and mobility analyses, and PacBio's SMRT sequencing (n=6). There were 56 multidrug-resistant CRKP, having blaOXA-48-like and blaNDM-1/7 carbapenemases on self-transmissible IncF, A/C, IncL/M and IncX3 plasmids endowed with prophages, traT, resistance islands, and type I and II restriction modification systems (RMS). Plasmids and clades detected in this study were respectively related to globally established/disseminated plasmids clades/clones, evincing transboundary horizontal and vertical dissemination. Reduced susceptibility to colistin occurred in 23 strains. Common clones included ST307, ST607, ST17, ST39 and ST3559. IncFIIk virulent plasmid replicon was present in 56 strains. Whole-genome sequencing of six strains revealed least 41 virulence genes, extensive ompK36 mutations, and four different K- and O-loci types: KL2, KL25, KL27, KL102, O1, O2, O4 and O5. Types I, II and III RMS, conferring m6A (GATC, GATGNNNNNNTTG, CAANNNNNNCATC motifs) and m4C (CCWGG) modifications on chromosomes and plasmids, were found. The nature of plasmid-mediated, clonal and multi-clonal dissemination of blaOXA-48-like and blaNDM-1 mirrors epidemiological trends observed for closely related plasmids and sequence types internationally. Worryingly, the presence of both blaOXA-48 and blaNDM-1 in the same isolates was observed. Plasmid-mediated transmission of RMS, virulome and prophages influence bacterial evolution, epidemiology, pathogenicity and resistance, threatening infection treatment. The influence of RMS on antimicrobial and bacteriophage therapy needs urgent investigation.

Phenotypic and Genotypic Features of Klebsiella pneumoniae Harboring Carbapenemases in Egypt: OXA-48-Like Carbapenemases as an Investigated Model

This study aimed at the characterization of carbapenem-resistant Klebsiella pneumoniae isolates focusing on typing of the bla_OXA-48-like genes. Additionally, the correlation between the resistance pattern and biofilm formation capacity of the carbapenem-resistant K. pneumoniae isolates was studied. The collected isolates were assessed for their antimicrobial resistance and carbapenemases production by a modified Hodge test and inhibitor-based tests. The carbapenemases encoding genes (bla_KPC, bla_NDM, bla_VIM, bla_IMP, and bla_OXA-48-like) were detected by PCR. Isolates harboring bla_OXA-48-like genes were genotyped by Enterobacterial Repetitive Intergenic Consensus-Polymerase Chain Reaction (ERIC-PCR) and plasmid profile analysis. The discriminatory power of the three typing methods (antibiogram, ERIC-PCR, and plasmid profile analysis) was compared by calculation of Simpson's Diversity Index (SDI). The transferability of bla_OXA-48 gene was tested by chemical transformation. The biofilm formation capacity and the prevalence of the genes encoding the fimbrial adhesins (fimH-1 and mrkD) were investigated. The isolates showed remarkable resistance to β-lactams and non-β-lactams antimicrobials. The coexistence of the investigated carbapenemases encoding genes was prevalent except for only 15 isolates. The plasmid profile analysis had the highest discriminatory power (SDI = 0.98) in comparison with ERIC-PCR (SDI = 0.89) and antibiogram (SDI = 0.78). The transferability of bla_OXA-48 gene was unsuccessful. All isolates were biofilm formers with the absence of a significant correlation between the biofilm formation capacity and resistance profile. The genes fimH-1 and mrkD were prevalent among the isolates. The prevalence of carbapenemases encoding genes, especially bla_OXA-48-like genes in Egyptian healthcare settings, is worrisome and necessitates further strict dissemination control measures.

Genomic and Resistance Epidemiology of Gram-Negative Bacteria in Africa: a Systematic Review and Phylogenomic Analyses from a One Health Perspective

Antibiotic resistance (AR) is one of the major public health threats and challenges to effective containment and treatment of infectious bacterial diseases worldwide. Here, we used different methods to map out the geographical hot spots, sources, and evolutionary epidemiology of AR. Escherichia coli, Klebsiella pneumoniae, Salmonella enterica, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter spp., Neisseria meningitis/gonorrhoeae, Vibrio cholerae, Campylobacter jejuni, etc., were common pathogens shuttling AR genes in Africa. Transmission of the same clones/strains across countries and between animals, humans, plants, and the environment was observed. We recommend Enterobacter spp. or K. pneumoniae as better sentinel species for AR surveillance.

Antibiotic resistance (AR) remains a major threat to public and animal health globally. However, AR ramifications in developing countries are worsened by limited molecular diagnostics, expensive therapeutics, inadequate numbers of skilled clinicians and scientists, and unsanitary environments. The epidemiology of Gram-negative bacteria, their AR genes, and geographical distribution in Africa are described here. Data were extracted and analyzed from English-language articles published between 2015 and December 2019. The genomes and AR genes of the various species, obtained from the Pathosystems Resource Integration Center (PATRIC) and NCBI were analyzed phylogenetically using Randomized Axelerated Maximum Likelihood (RAxML) and annotated with Figtree. The geographic location of resistant clones/clades was mapped manually. Thirty species from 31 countries and 24 genera from 41 countries were analyzed from 146 articles and 3,028 genomes, respectively. Genes mediating resistance to β-lactams (including bla_TEM-1, bla_CTX-M, bla_NDM, bla_IMP, bla_VIM, and bla_OXA-48/181), fluoroquinolones (oqxAB, qnrA/B/D/S, gyrA/B, and parCE mutations, etc.), aminoglycosides (including armA and rmtC/F), sulfonamides (sul1/2/3), trimethoprim (dfrA), tetracycline [tet(A/B/C/D/G/O/M/39)], colistin (mcr-1), phenicols (catA/B, cmlA), and fosfomycin (fosA) were mostly found in Enterobacter spp. and Klebsiella pneumoniae, and also in Serratia marcescens, Escherichia coli, Salmonella enterica, Pseudomonas, Acinetobacter baumannii, etc., on mostly IncF-type, IncX_3/4, ColRNAI, and IncR plasmids, within IntI1 gene cassettes, insertion sequences, and transposons. Clonal and multiclonal outbreaks and dissemination of resistance genes across species and countries and between humans, animals, plants, and the environment were observed; Escherichia coli ST103, K. pneumoniae ST101, S. enterica ST1/2, and Vibrio cholerae ST69/515 were common strains. Most pathogens were of human origin, and zoonotic transmissions were relatively limited.

IMPORTANCE Antibiotic resistance (AR) is one of the major public health threats and challenges to effective containment and treatment of infectious bacterial diseases worldwide. Here, we used different methods to map out the geographical hot spots, sources, and evolutionary epidemiology of AR. Escherichia coli, Klebsiella pneumoniae, Salmonella enterica, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter spp., Neisseria meningitis/gonorrhoeae, Vibrio cholerae, Campylobacter jejuni, etc., were common pathogens shuttling AR genes in Africa. Transmission of the same clones/strains across countries and between animals, humans, plants, and the environment was observed. We recommend Enterobacter spp. or K. pneumoniae as better sentinel species for AR surveillance.

Epidemiology and prevalence of extended-spectrum β-lactamase- and carbapenemase-producing Enterobacteriaceae in humans, animals and the environment in West and Central Africa

Extended-spectrum β-lactamase-producing Enterobacteriaceae (ESBL-E) and carbapenemase-producing Enterobacteriaceae (CPE) are widespread. Here we used the 'One Health' approach to determine knowledge gaps on ESBL-E and CPE in West and Central Africa. We searched all articles on ESBL-E and CPE in these African regions published in PubMed, African Journals Online and Google Scholar from 2000 onwards. Among the 1201 articles retrieved, we selected 165 studies (West Africa, 118; Central Africa, 47) with data from 22 of the 26 West and Central Africa countries. Regarding the settings, 136 articles focused only on humans (carriage and/or infection), 6 articles on humans and animals, 13 on animals, 1 on humans and the environment, 8 on the environment and 1 on humans, animals and environments. ESBL-E prevalence ranged from 11-72% in humans and 7-79% in aquatic environments (wastewater). In animals, ESBL-E prevalence hugely varied: 0% in cattle, 11-36% in chickens, 20% in rats, 21-71% in pigs and 32-75% in dogs. The bla_CTX-M-15 gene was the predominant ESBL-encoding gene and was associated with plasmids of incompatibility groups F, H, K, Y, N, I1 and R. CPE were studied only in humans. Class B metallo-β-lactamases (NDM) and class D oxacillinases (OXA-48 and OXA-181) were the most common carbapenemases. Our results show major knowledge gaps, particularly on ESBL and CPE in animals and the environment, that might limit antimicrobial resistance management in these regions. The results also emphasise the urgent need to improve active surveillance programmes in each country and to support antimicrobial stewardship.

Prevalence and Molecular Characterization of Extended Spectrum β-Lactamase, Plasmid-Mediated Quinolone Resistance, and Carbapenemase-Producing Gram-Negative Bacilli in Burkina Faso

The spreading of carbapenemase-producing gram-negative bacilli (GNB) must be considered as an "urgent" threat. The aim of this study was to determine the prevalence of extended spectrum β-lactamase (ESBL), plasmid-mediated quinolone resistance (PMQR), and carbapenemase-producing GNB and to characterize the supporting genes in GNB specimens isolated from patients and healthy volunteers in Burkina Faso. From April to June 2016, carbapenemase-producing GNB screening was performed in 1,230 consecutive clinical specimens, and 158 fecal samples from inpatients and healthy volunteers without digestive pathology at Souro Sanou University Hospital, Bobo Dioulasso. Strains were identified by matrix-assisted laser desorption ionization-time of flight and antimicrobial susceptibility was tested with the disk diffusion method on Müller-Hinton agar. The presence of carbapenemase, ESBL, and PMQR genes was assessed by multiplex PCR. The molecular epidemiological study was performed using multilocus sequence typing analysis. From the 1,230 clinical samples, 443 GNB strains were isolated among which 4 (0.9%) were carbapenemase-producing isolates (Escherichia coli, n = 1; Acinetobacter baumannii, n = 3). Among the 158 fecal samples tested for carbapenemase-producing Enterobacteriaceae carriage, 13 (8.2%) were carbapenemase-producing isolates (E. coli, n = 4; Klebsiella pneumoniae, n = 6; A. baumannii, n = 2; Acinetobacter nosocomialis, n = 1; Acinetobacter bereziniae, n = 1). The strains from the two groups were resistant to broad-spectrum cephalosporins (100% for both), gentamicin (100% and 64.3%), levofloxacin (100% and 85.7%), and to amikacin (0% and 7.1%). The carbapenemase-encoding genes bla_NDM-1, bla_Oxa-58, bla_Oxa-181, and bla_VIM-2 were detected in clinical and in fecal samples. The majority (10/11) of the enterobacterial strains carried also bla_CTX-M-15. The majority of the strains belonged to ST692 for E. coli, to ST147 for K. pneumoniae and to ST2 for A. baumannii. This study confirms the presence of carbapenemase-producing GNB in samples from patients and healthy volunteers. More effective active surveillance activities are needed.

Carbapenem Resistant Enterobacteriaceae in Africa

Carbapenems are regarded as unique among the �-lactam antibiotics due to their broad spectrum of activity and ability to resist �-lactamase hydrolysis. Carbapenems are the only �-lactam antibiotics with efficacy in severe infections caused by extended-spectrum beta-lactamase (ESBL) producing bacteria. However, recent reports of carbapenem resistance particularly among members of Enterobacteriaceae that are responsible for diseases such as gastrointestinal infections, septicemia, pneumonia, meningitis, peritonitis as well as urinary tract infections, call for concerns. In Africa, the problem of carbapenem-resistant Enterobacteriaceae (CRE) is aggravated by factors such as the high rate of infections, poor diagnostic tools, sub-optimal disease surveillance, and abuse of antibiotics. Besides, the problem of CRE in Africa is understudied. This review distills available literature on the spread of CRE in Africa, CRE genes in circulation, and the need to pay attention to this emerging threat to lives in developing countries.

Emergence of mcr-9.1 in Extended-Spectrum-β-Lactamase-Producing Clinical Enterobacteriaceae in Pretoria, South Africa: Global Evolutionary Phylogenomics, Resistome, and Mobilome

Extended-spectrum-β-lactamase (ESBL)-producing Enterobacteriaceae are critical-priority pathogens that cause substantial fatalities. With the emergence of mobile mcr genes mediating resistance to colistin in Enterobacteriaceae, clinicians are now left with few therapeutic options. Eleven clinical Enterobacteriaceae strains with resistance to cephems and/or colistin were genomically analyzed to determine their resistomes, mobilomes, and evolutionary relationships to global strains. The global phylogenomics of mcr genes and mcr-9.1-bearing genomes were further analyzed. Ten isolates were ESBL positive. The isolates were multidrug resistant and phylogenetically related to global clones but distant from local strains. Multiple resistance genes, including bla _CTX-M-15 bla _TEM-1, and mcr-9.1, were found in single isolates; ISEc9, IS19, and Tn3 transposons bracketed bla _CTX-M-15 and bla _TEM-1 Common plasmid types included IncF, IncH, and ColRNAI. mcr-9 was of close sequence identity to mcr-3, mcr-5, mcr-7, mcr-8, and mcr-10. Genomes bearing mcr-9.1 clustered into six main phyletic groups (A to F), with those of this study belonging to clade B. Enterobacter species and Salmonella species are the main hosts of mcr-9.1 globally, although diverse promiscuous plasmids disseminate mcr-9.1 across different bacterial species. Emergence of mcr-9.1 in ESBL-producing Enterobacteriaceae in South Africa is worrying, due to the restricted therapeutic options. Intensive One Health molecular surveillance might discover other mcr alleles and inform infection management and antibiotic choices.IMPORTANCE Colistin is currently the last-resort antibiotic for difficult-to-treat bacterial infections. However, colistin resistance genes that can move from bacteria to bacteria have emerged, threatening the safe treatment of many bacterial infections. One of these genes, mcr-9.1, has emerged in South Africa in bacteria that are multidrug resistant, further limiting treatment options for clinicians. In this work, we show that this new gene is disseminating worldwide through Enterobacter and Salmonella species through multiple plasmids. This worrying observation requires urgent action to prevent further escalation of this gene in South Africa and Africa.

Pathogenomics and Evolutionary Epidemiology of Multi-Drug Resistant Clinical Klebsiella pneumoniae Isolated from Pretoria, South Africa

Antibiotic-resistant Klebsiella pneumoniae is increasingly being implicated in invasive infections worldwide with high mortalities. Forty-two multidrug resistant (MDR) K. pneumoniae isolates were collected over a 4-month period. Antimicrobial susceptibility was determined using Microscan. The evolutionary epidemiology, resistome, virulome and mobilome of the isolates were characterised using whole-genome sequencing and bioinformatics analysis. All isolates contained the bla_CTX-M gene, whilst 41/42(97%) contained bla_TEM, 36/42(86%) contained bla_OXA and 35/42(83%) harboured bla_SHV genes. Other resistance genes found included bla_LEN, aac(6′)-lb-cr, qnrA, qnrB, qnrS, oqxAB, aad, aph, dfr, sul1, sul2, fosA, and cat genes. Fluoroquinolone and colistin resistance-conferring mutations in parC, gyrAB, pmrAB, phoPQ and kpnEF were identified. The bla_LEN gene, rarely described worldwide, was identified in four isolates. The isolates comprised diverse sequence types, the most common being ST152 in 7/42(17%) isolates; clone-specific O and K capsule types were identified. Diverse virulence genes that were not clone-specific were identified in all but one isolate. IncF, IncH and IncI plasmid replicons and two novel integrons were present. The bla_CTX-M-15 and bla_TEM-1 genes were bracketed by Tn3 transposons, ISEc9, a resolvase and IS91 insertion sequence. There were 20 gene cassettes in 14 different cassette arrays, with the dfrA and aadA gene cassettes being the most frequent. Phylogenetic analysis demonstrated that the isolates were evolutionarily associated with strains from both South Africa and abroad. These findings depict the rich resistome, mobilome and virulome repertoire in clinical K. pneumoniae strains, which are mainly transmitted by clonal, multiclonal and horizontal means in South Africa.

Genomic Analysis of Carbapenemase-Producing Extensively Drug-Resistant Klebsiella pneumoniae Isolates Reveals the Horizontal Spread of p18-43_01 Plasmid Encoding blaNDM-1 in South Africa

Whole-genome sequence (WGS) analyses were employed to investigate the genomic epidemiology of extensively drug-resistant Klebsiella pneumoniae strains, focusing on the carbapenem resistance-encoding determinants, mobile genetic support, clonal and epidemiological relationships. A total of ten isolates were obtained from patients admitted to the intensive care unit (ICU) in a public hospital in South Africa. Five isolates were from rectal swabs of colonized patients and five from blood cultures of patients with invasive carbapenem-resistant infections. Following microbial identification and antibiotic susceptibility tests, the isolates were subjected to WGS on the Illumina MiSeq platform. All the isolates showed genotypic resistance to tested β-lactams (NDM-1, OXA-1, CTX-M-15, TEM-1B, SHV-1) and other antibiotics. All but one isolate belonged to the ST152 with a novel sequence type, ST3136, differing by a single-locus variant. The isolates had the same plasmid multilocus sequence type (IncF[K12:A-:B36]) and capsular serotype (KL149), supporting the epidemiological linkage between the clones. Resistance to carbapenems in the 10 isolates was conferred by the bla_NDM-1 mediated by the acquisition of multi-replicon [ColRNAI, IncFIB(pB171), Col440I, IncFII, IncFIB(K) and IncFII(Yp)] p18-43_01 plasmid. These findings suggest that the acquisition of bla_NDM-1-bearing plasmid structure (p18-43_01), horizontal transfer and clonal dissemination facilitate the spread of carbapenemases in South Africa. This emphasizes the importance of targeted infection control measures to prevent dissemination.

First Identification and genomic characterization of multidrug-resistant carbapenemase-producing Enterobacteriaceae clinical isolates in Malawi, Africa

Purpose. Carbapenemase-producing Enterobacteriaceae (CPE) have become a global concern and a serious threat to human health due to their resistance to multiple antibiotics. In this study, we identified and characterized CPE for the first time in Malawi, southeastern Africa.Methodology. We investigated the possible presence of carbapenemases among a collection of 200 ceftriaxone-nonsusceptible Gram-negative clinical isolates obtained from five Malawian hospitals between January 2016 and December 2017, using both phenotypic and genotypic tests. Molecular typing of CPE was done by PFGE, multilocus sequence typing (ST) or phylogenetic grouping. Resistant plasmids were characterized by S1 PFGE, Southern blotting and conjugation assays.Results. Out of 200 isolates, we detected 16 (8 %) CPE of which all originated from one referral hospital, Kamuzu Central Hospital, in the Central part of Malawi. Of 16 isolates, seven Klebsiella pneumoniae ST340/CC258 carried bla _KPC-2, two Escherichia coli ST636 (phylogroup B2) carried bla _NDM-5, six E. coli ST617 (phylogroup A) and one Klebsiella variicola carried bla _OXA-48. All carbapenemases were plasmid-encoded, but only bla _NDM-5-carrying plasmids could be conjugated. Most isolates co-harboured other β-lactamases and consequently exhibited a wider spectrum of resistance to commonly used antibiotics. We observed indistinguishable genetic profiles between strain types, despite originating from different wards, suggesting acquisition during admission and intra-hospital spread.Conclusion. This report strongly suggests a probable existence of highly resistant various types of CPE organisms in Malawi including KPC-2-producing K. pneumoniae ST340/CC258, a known high-risk epidemic lineage.

Plasmid evolution in carbapenemase-producing Enterobacteriaceae: a review

Carbapenem-resistant Enterobacteriaceae (CRE) have been listed by the WHO as high-priority pathogens owing to their high association with mortalities and morbidities. Resistance to multiple β-lactams complicates effective clinical management of CRE infections. Using plasmid typing methods, a wide distribution of plasmid replicon groups has been reported in CREs around the world, including IncF, N, X, A/C, L/M, R, P, H, I, and W. We performed a literature search for English research papers, published between 2013 and 2018, reporting on plasmid-mediated carbapenem resistance. A rise in both carbapenemase types and associated plasmid replicon groups was seen, with China, Canada, and the United States recording a higher increase than other countries. bla_KPC was the most prevalent, except in Angola and the Czech Republic, where OXA-181 (n = 50, 88%) and OXA-48-like (n = 24, 44%) carbapenemases were most prevalent, respectively; bla_KPC-2/3 accounted for 70% (n = 956) of all reported carbapenemases. IncF plasmids were found to be responsible for disseminating different antibiotic resistance genes worldwide, accounting for almost 40% (n = 254) of plasmid-borne carbapenemases. bla_CTX-M , bla_TEM , bla_SHV , bla_OXA-1/9 , qnr, and aac-(6')-lb were mostly detected concurrently with carbapenemases. Most reported plasmids were conjugative but not present in multiple countries or species, suggesting limited interspecies and interboundary transmission of a common plasmid. A major limitation to effective characterization of plasmid evolution was the use of PCR-based instead of whole-plasmid sequencing-based plasmid typing.

Genomic analysis of methicillin-resistant Staphylococcus aureus isolated from poultry and occupational farm workers in Umgungundlovu District, South Africa

This study detected methicillin-resistant Staphylococcus aureus (MRSA) isolates circulating in poultry and farm workers at an intensive poultry production system in uMgungundlovu, South Africa and established the genetic relatedness and characteristics of the isolates using whole genome sequencing (WGS). A total of 145 S. aureus were isolated from poultry (120) and occupational workers (25) in the "farm to fork" continuum (farm, transport, slaughterhouse, and retail points). Twelve MRSA (12/145; 8.3%) isolates were found in the poultry food-chain. MRSA isolates were subjected to antibiotic susceptibility testing against a panel of 20 antibiotics using the broth dilution method and their whole genome was sequenced via the Illumina MiSeq. All the MRSA isolates were multi-drug resistant (MDR) and carried the mecA gene on the SCCmec mobile genetic element (MGE). The majority (11/12) of the MRSA isolates circulating between humans and animals in the continuum belonged to a human-associated clone, ST612-CC8-t1257-SCCmec_IVd (2B), previously reported in South Africa. Other MGEs present in the isolates included: plasmid replicons based on Rep 7 and 20, insertion sequences (IS1182), and prophages (phi2958PVL). Genomic analysis identified a distinct acquired antibiotic resistome in the clone, which accurately predicted the phenotypic antibiograms. Phylogenetic analysis clustered the isolates within the major cluster (I), suggesting the spread of the local dominant multidrug resistance MRSA clone ST612-CC8-t1257-SCCmec_IVd (2B) between humans and animals along the 'farm to fork' continuum. The findings of this study suggest the need to establish appropriate control measures to curb the spread of MDR-MRSA in the food chain.

1,4,7-Triazacyclononane Restores the Activity of β-Lactam Antibiotics against Metallo-β-Lactamase-Producing Enterobacteriaceae: Exploration of Potential Metallo-β-Lactamase Inhibitors

Metallo-β-lactamase (MBL)-producing Enterobacteriaceae are of grave clinical concern, particularly as there are no metallo-β-lactamase inhibitors approved for clinical use. The discovery and development of MBL inhibitors to restore the efficacy of available β-lactams are thus imperative. We investigated a zinc-chelating moiety, 1,4,7-triazacyclononane (TACN), for its inhibitory activity against clinical carbapenem-resistant Enterobacteriaceae MICs, minimum bactericidal concentrations (MBCs), the serum effect, fractional inhibitory concentration indexes, and time-kill kinetics were determined using broth microdilution techniques according to Clinical and Laboratory Standards Institute (CSLI) guidelines. Enzyme kinetic parameters and the cytotoxic effects of TACN were determined using spectrophotometric assays. The interactions of the enzyme-TACN complex were investigated by computational studies. Meropenem regained its activity against carbapenemase-producing Enterobacteriaceae, with the MIC decreasing from between 8 and 64 mg/liter to 0.03 mg/liter in the presence of TACN. The TACN-meropenem combination showed bactericidal effects with an MBC/MIC ratio of ≤4, and synergistic activity was observed. Human serum effects on the MICs were insignificant, and TACN was found to be noncytotoxic at concentrations above the MIC values. Computational studies predicted that TACN inhibits MBLs by targeting their catalytic active-site pockets. This was supported by its inhibition constant (Ki ), which was 0.044 μM, and its inactivation constant (Kinact), which was 0.0406 min-1, demonstrating that TACN inhibits MBLs efficiently and holds promise as a potential inhibitor.IMPORTANCE Carbapenem-resistant Enterobacteriaceae (CRE)-mediated infections remain a significant public health concern and have been reported to be critical in the World Health Organization's priority pathogens list for the research and development of new antibiotics. CRE produce enzymes, such as metallo-β-lactamases (MBLs), which inactivate β-lactam antibiotics. Combination therapies involving a β-lactam antibiotic and a β-lactamase inhibitor remain a major treatment option for infections caused by β-lactamase-producing organisms. Currently, no MBL inhibitor-β-lactam combination therapy is clinically available for MBL-positive bacterial infections. Hence, developing efficient molecules capable of inhibiting these enzymes could be a promising way to overcome this phenomenon. TACN played a significant role in the inhibitory activity of the tested molecules against CREs by potentiating the activity of carbapenem. This study demonstrates that TACN inhibits MBLs efficiently and holds promises as a potential MBL inhibitor to help curb the global health threat posed by MBL-producing CREs.

In vitro potentiation of carbapenems with tannic acid against carbapenemase-producing enterobacteriaceae: exploring natural products as potential carbapenemase inhibitors

AIMS

We hypothesized and confirmed that tannic acid (TA) reverses carbapenem resistance by inhibiting carbapenemases in class A and B carbapenemase-producing Enterobacteriaceae.

METHODS AND RESULTS

Minimum inhibitory concentrations of carbapenems in the presence and absence of TA and other efflux pump inhibitors, TA-carbapenemases inhibition assays and computational studies showed that TA had the greatest effect on metallo-β-lactamases (MBLs) followed by class A serine-β-lactamases (SBLs). TA completely reversed the MICs of MBL producers from between 32 and ≥512 mg l^-1 to susceptible values (<4 mg l^-1 ) while substantially reducing the MICs of SBLs from between 16 and >512 mg l^-1 to <4 to 16 mg l^-1 . Tolerable cytotoxic effect was observed for the concentrations tested (8-1024 mg l^-1 ). TA inhibited enzymes with a marked difference of ≈50% inhibition (IC₅₀ ) for NDM-1 (270 μmol l^-1 ) and KPC-2 (15  μmol l^-1 ).

CONCLUSION

TA inhibited both MBLs and SBLs by targeting their hydrophobic sites. Moreover, TA had a stronger binding affinity for MBLs than SBLs as the MBLs, specifically VIM-1 (-43·7220 ± 0·4513 kcal mol^-1 ) and NDM-1(-44·2329 ± 0·3806 kcal mol^-1 ), interact with a larger number of their catalytic active-site residues than that of OXA-48 (-22·5275 ±  0·1300 kcal mol^-1 ) and KPC-2 (-22·1164 ± 0·0111 kcal mol^-1 ).

SIGNIFICANCE AND IMPACT OF THE STUDY

Tannic acid or its analogues could be developed into carbapenemase-inhibiting adjuvants to restore carbapenem activity in CRE infections, save many lives and reduce healthcare associated costs.

Detection of the carbapenemase gene blaVIM-5 in members of the Pseudomonas putida group isolated from polluted Nigerian wetlands

There are increasing concerns about possible dissemination of clinically relevant antibiotic resistance genes, including genes encoding for carbapenemases in the environment. However, little is known about environmental distribution of antibiotic resistance in Africa. In this study, four polluted urban wetlands in Nigeria were investigated as potential reservoirs of carbapenem-resistant bacteria (CRB). CRB were isolated from the wetlands, characterized by Blue-Carba test, MIC determinations and whole genome sequencing (WGS). Nine of 65 bacterial isolates identified as members of the Pseudomonas putida group (P. plecoglossicida and P. guariconensis, respectively) harboured the metallo-beta-lactamase gene bla_VIM-5. WGS revealed the bla_VIM-5 in three novel Tn402-like class 1 integron structures containing the cassette arrays aadB|bla_VIM-5|bla_PSE-1, aadB|bla_VIM-5|aadB|bla_PSE-1, and bla_VIM-5|aadB|tnpA|bla_PSE-1|smr2|tnpA, respectively. Strains carrying the aadB|bla_VIM-5|bla_PSE-1 cassette also carried an identical integron without bla_VIM-5. In addition_, the strains harboured another Tn402-like class 1 integron carrying bcr2, several multidrug resistance efflux pumps, and at least one of ampC, aph(3”)-lb, aph(6)-ld, tetB, tetC, tetG, floR, and macAB. This is the first report of a carbapenemase gene in bacteria from environmental sources in Nigeria and the first report of bla_VIM-5 in environmental bacteria isolates. This result underscores the role of the Nigerian environment as reservoir of bacteria carrying clinically relevant antibiotic resistance genes.

Screening and Characterization of Multidrug-Resistant Gram-Negative Bacteria from a Remote African Area, São Tomé and Príncipe

The occurrence of resistance to last-resort antibiotics was evaluated among Enterobacteriaceae isolates recovered from hospitalized children in a remote African archipelago, São Tomé and Príncipe, where there is limited access to those antibiotics. Fifty patients were screened for colonization by carbapenem-, pan-aminoglycoside-, or polymyxin-resistant Enterobacteriaceae A total of 36 isolates (including 30 Escherichia coli and 4 Klebsiella pneumoniae) were recovered from 23 patients, including 26 isolates harboring the bla_OXA-181 carbapenemase gene, a single isolate harboring the 16S rRNA methylase gene rmtB encoding pan-resistance to aminoglycosides, and 8 isolates coharboring both genes. A single isolate possessed the plasmid-borne colistin resistance gene mcr-1 A high clonal relationship was found for OXA-181-producing E. coli (4 clones), and conversely, three of the four OXA-181-producing K. pneumoniae isolates were clonally unrelated. This study overall showed a high prevalence of resistance to last-resort antibiotics in this country, where no epidemiological data were previously available.

Spread of Plasmid-Encoded NDM-1 and GES-5 Carbapenemases among Extensively Drug-Resistant and Pandrug-Resistant Clinical Enterobacteriaceae in Durban, South Africa

Whole-genome sequence analyses revealed the presence of bla_NDM-1 (n = 31), bla_GES-5 (n = 8), bla_OXA-232 (n = 1), or bla_NDM-5 (n = 1) in extensively drug-resistant and pandrug-resistant Enterobacteriaceae organisms isolated from in-patients in 10 private hospitals (2012 to 2013) in Durban, South Africa. Two novel NDM-1-encoding plasmids from Klebsiella pneumoniae were circularized by PacBio sequencing. In p19-10_01 [IncFIB(K); 223.434 bp], bla_NDM-1 was part of a Tn1548-like structure (16.276 bp) delineated by IS26 The multireplicon plasmid p18-43_01 [IncR_1/IncFIB(pB171)/IncFII(Yp); 212.326 bp] shared an 80-kb region with p19-10_01, not including the bla_NDM-1-containing region. The two plasmids were used as references for tracing NDM-1-encoding plasmids in the other genome assemblies. The p19-10_01 sequence was detected in K. pneumoniae (n = 7) only, whereas p18-43_01 was tracked to K. pneumoniae (n = 4), Klebsiella michiganensis (n = 1), Serratia marcescens (n = 11), Enterobacter spp. (n = 7), and Citrobacter freundii (n = 1), revealing horizontal spread of this bla_NDM-1-bearing plasmid structure. Global phylogeny showed clustering of the K. pneumoniae (18/20) isolates together with closely related carbapenemase-negative ST101 isolates from other geographical origins. The South African isolates were divided into three phylogenetic subbranches, where each group had distinct resistance and replicon profiles, carrying either p19-10_01, p18-10_01, or pCHE-A1 (8,201 bp). The latter plasmid carried bla_GES-5 and aacA4 within an integron mobilization unit. Our findings imply independent plasmid acquisition followed by local dissemination. Additionally, we detected bla_OXA-232 carried by pPKPN4 in K. pneumoniae (ST14) and bla_NDM-5 contained by a pNDM-MGR194-like genetic structure in Escherichia coli (ST167), adding even more complexity to the multilayer molecular mechanisms behind nosocomial spread of carbapenem-resistant Enterobacteriaceae in Durban, South Africa.

Genomic insights into nitrofurantoin resistance mechanisms and epidemiology in clinical Enterobacteriaceae

Aim:

Multidrug-resistant enterobacteria are highly associated with invasive devices and intensive care units. Increasing resistance to carbapenems is leading to the use of older and neglected antibiotics such as nitrofurantoin (NFT). The genomics of NFT resistance was investigated.

Results & conclusion:

High-level resistance to NFT (minimum inhibitory concentration ≥128–512 mg/l) was recorded in 31/36 isolates (89.6%), many of which were from intensive care units (n = 20), urine (n = 17) or invasive procedures (n = 10). Efflux pump inhibitors had little effect on NFT's minimum inhibitory concentrations albeit oqxAB was prevalent in most isolates (n = 32). Various species- and clone-specific mutations mediating high-level NFT resistance were detected in nfsA, nfsB and ribE proteins through comparative genomics. Global phylogenomics showed local and independent emergence of NFT resistance in Enterobacteriaceae. NFT stewardship is advised.

Nitrofurantoin (NFT) is an important antibiotic indicated for uncomplicated urinary tract infections. Resistance to NFT is slow and uncommon, making it an important drug for treating urinary tract infections resistant to common and last-resort antibiotics such as cephalosporins, fluoroquinolones, aminoglycosides and carbapenems. Increasing resistance to most antibiotics among uropathogens makes NFT a key choice for clinicians. Thus, the high-level NFT resistance in extradrug- and pandrug-resistant uropathogens found in this study is exceptionally worrying as treatment options will be extremely limited. Mutations in nfsA, nfsB and ribE genes in the same and different strains emerged locally and independently to confer NFT resistance.

Emerging mechanisms of antimicrobial resistance in bacteria and fungi: advances in the era of genomics

Bacteria and fungi continue to develop new ways to adapt and survive the lethal or biostatic effects of antimicrobials through myriad mechanisms. Novel antibiotic resistance genes such as lsa(C), erm(44), VCC-1, mcr-1, mcr-2, mcr-3, mcr-4, bla _KLUC-3 and bla _KLUC-4 were discovered through comparative genomics and further functional studies. As well, mutations in genes that hitherto were unknown to confer resistance to antimicrobials, such as trm, PP2C, rpsJ, HSC82, FKS2 and Rv2887, were shown by genomics and transcomplementation assays to mediate antimicrobial resistance in Acinetobacter baumannii, Staphylococcus aureus, Enterococcus faecium, Saccharomyces cerevisae, Candida glabrata and Mycobacterium tuberculosis, respectively. Thus, genomics, transcriptomics and metagenomics, coupled with functional studies are the future of antimicrobial resistance research and novel drug discovery or design.

First report on bla NDM-1-producing Acinetobacter baumannii in three clinical isolates from Ethiopia

Background

Multidrug-resistant Gram-negative bacterial infections are recognized as one of the major threats to global health. In this study, we describe for the first time bla_NDM-1 gene carrying organisms from Ethiopia consisting of three Acinetobacter baumannii isolates from patients in Jimma.

Methods

Besides phenotypic antimicrobial susceptibility testing, molecular strain typing and sequencing was performed to describe the phylogenetic relation of the Ethiopian isolates in detail in relation to published isolates from all over the globe.

Results and discussion

Three multi-resistant, bla_NDM-1-positive Acinetobacter baumannii isolates, most likely a local clonal diffusion, were isolated. Two of the three isolates described within this study were untreatable with the locally available antimicrobials and were only susceptible to polymyxin B and amikacin. The genome sequences confirmed the isolates to be distinct from the outbreak strains reported from Kenya, the only other characterized bla_NDM-1 positive Acinetobacter baumannii strains in East Africa so far. Up to date, no other bacterial species were found to harbour the gene cassette in Jimma and conjugation to E. coli was not successful under laboratory conditions. However, natural transmission to other bacteria seems likely, given the evident lack of hygienic precautions due to limited resource settings.

Conclusions

The detected isolates could solely be the tip of the iceberg regarding the presence of NDM-1 producing organisms in the region, as only a limited number of bacterial isolates were evaluated so far and until recently, susceptibility testing and isolation of bacteria could hardly be performed in clinical patient care. These multi-drug resistant organisms pose a serious threat to antimicrobial treatments in Jimma, Ethiopia.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-017-2289-9) contains supplementary material, which is available to authorized users.

Carbonyl Cyanide m-Chlorophenylhydrazine (CCCP) Reverses Resistance to Colistin, but Not to Carbapenems and Tigecycline in Multidrug-Resistant Enterobacteriaceae

Background: Carbapenems (CAR), colistin (CST), and tigecycline (TGC) alone or in combination therapy has become the last-resort antibiotics for treating infections caused by multidrug resistant (MDR) bacteria. However, resistance to these reserve antibiotics are increasingly being reported worldwide. Hence, the quest to find other agents that will synergistically restore the efficacy of these antibiotics have increased. Methods: Sixty-three clinical Enterobacteriaceae isolates comprising of Klebsiella pneumoniae (n = 24), Enterobacter spp. (n = 15), Serratia marcescens (n = 12), Citrobacter freundii (n = 8), Escherichia coli (n = 2), and K. oxytoca/michiganensis (n = 2) with known carbapenem resistance mechanisms and undescribed CST and TGC resistance mechanisms were subjected to broth microdilution and meropenem (MEM) disc synergy test in the presence and absence of carbonyl cyanide m-chlorophenylhydrazine (CCCP), a H⁺ conductor (protonophore). Results and conclusions: Susceptibility to MEM, imipenem (IMP), CST, and TGC was found in only 2, 0, 17, and 9 isolates respectively. Addition of CCCP reversed resistance to CST, TGC, IMP, and MEM in 44, 3, 0, and 0 isolates respectively; CST had the highest mean minimum inhibitory concentration (MIC) fold change (193.12; p < 0.0001) post CCCP compared to that of MEM (1.70), IMP (1.49) and TGC (1.16). Eight isolates tested positive for the MEM-CCCP disc synergy test. We concluded that CCCP reverse CST resistance in CST-resistant Enterobacteriaceae. Although CCCP is an experimental agent with no therapeutic value clinically, further studies are necessary to decipher the mechanisms underlying the CST-CCCP synergy to inform the development of adjuvants that could be therapeutically effective in CST-resistant infections.

High Carbapenem Resistance in Clinical Gram-Negative Pathogens Isolated in Egypt

The emergence and spread of carbapenem-resistant gram-negative bacteria poses a serious threat to human health worldwide. Currently, little is known about the molecular mechanisms underlying carbapenem resistance and their prevalence among gram-negative bacteria in Egypt. In this study, we analyzed carbapenemase production in gram-negative bacteria isolated from hospitalized patients in Egypt in 2014. All isolates were subjected to phenotypic and genotypic susceptibility testing for carbapenem resistance. Our results indicated a high level of carbapenem-resistant gram-negative bacteria in Egypt, with 50.8% of the isolates harboring at least one carbapenem resistance gene. OXA-48-like and NDM-1 were the most prevalent carbapenemases, being detected in 49.2%, and 47.7% of carbapenemase-positive isolates, respectively, whereas Verona integron-encoded metallo-β-lactamase (VIM) was detected in only 26.2% of carbapenemase-positive isolates. This study reports for the first time carbapenemase-producing Serratia marcescens, Morganella morganii, and bla_VIM-1-like-producing Pseudomonas aeruginosa in Egypt. It is also the first demonstration of the coexistence of different carbapenemases, being detected in 21.5% of carbapenemase-positive isolates. Effective antibiotic supervision, regional surveillance, and early detection of carbapenemase producers are imperative to prevent their future spread to epidemic levels.

Five-Year Antimicrobial Susceptibility Trends Among Bacterial Isolates from a Tertiary Health-Care Facility in Kigali, Rwanda

Antimicrobial resistance (AMR) is a global public health threat. There is limited information from Rwanda on AMR trends. This longitudinal study aimed to describe temporal trends of antibiotic susceptibility among common bacteria. We collated the antimicrobial susceptibility results of bacteria cultured from clinical specimens collected from inpatients and outpatients and submitted to the microbiology laboratory at King Faisal Hospital, Kigali, Rwanda, from January 1, 2009, to December 31, 2013. Differences in antimicrobial susceptibility between the first and fifth year of the study for each bacterial species was assessed using χ² test. Of 5,296 isolates collected, 46.7% were Escherichia coli, 18.4% were Klebsiella spp., 5.9% were Acinetobacter spp., 7.1% were Pseudomonas spp., 11.7% were Staphylococcus aureus, and 10.3% were Enterococcus spp. Colistin and imipenem had greatest activity against gram-negative bacteria. Acinetobacter spp. showed the greatest resistance profile to antimicrobials tested, relative to other gram-negative bacteria. Vancomycin retained excellent activity against S. aureus and Enterococcus species (average susceptibility was 100% and 99.4%, respectively). Trend analysis determined that resistance to imipenem increased significantly among Klebsiella, E. coli, Pseudomonas, and Acinetobacter isolates; there was also rising resistance to colistin among E. coli and Pseudomonas species. Only E. coli demonstrated increased resistance to gentamicin. For gram-positive pathogens, vancomycin susceptibility increased over time for Enterococcus species, but was unchanged for S. aureus Our data suggest that resistance to imipenem and colistin are rising among gram-negative bacteria in Rwanda. Proper infection control practices and antimicrobial stewardship will be important to address this emerging threat.

Current State of Resistance to Antibiotics of Last-Resort in South Africa: A Review from a Public Health Perspective

A review of the literature was undertaken to delineate the current level and mechanisms of resistance to carbapenems, colistin, and tigecycline in South Africa. Thirty-two English publications and 32 National Institute of Communicable Diseases communiqués identified between early January 2000 and 20 May, 2016 showed substantial reports of NDM (n = 860), OXA-48 (n = 584), VIM (n = 131), and IMP (n = 45) carbapenemases within this period, mainly in Klebsiella pneumoniae (n = 1138), Acinetobacter baumannii (n = 332), Enterobacter cloacae (n = 201), and Serratia marcescens (n = 108). Colistin and tigecycline resistance was prevalent among K. pneumoniae, A. baumannii, S. marcescens, and E. cloacae. The first mcr-1 colistin resistance gene to be detected in South Africa was reported in Escherichia coli from livestock as well as from hospitalized and outpatients. There are increasing reports of NDM and OXA-48 carbapenemases among Enterobacteriaceae and A. baumannii in South Africa. Mcr-1 is now present in South African patients and livestock. Resistance to carbapenems, colistin, and tigecycline restricts infection management options for clinicians.

Colistin and tigecycline resistance in carbapenemase-producing Gram-negative bacteria: emerging resistance mechanisms and detection methods

A literature review was undertaken to ascertain the molecular basis for tigecycline and colistin resistance mechanisms and the experimental basis for the detection and delineation of this resistance particularly in carbapenemase-producing Gram-negative bacteria. Pubmed, Google Scholar and Science Direct were searched with the keywords colistin, tigecycline, resistance mechanisms and detection methods. Trans-complementation and comparative MIC studies, mass spectrometry, chromatography, spectrofluorometry, PCR, qRT-PCR and whole genome sequencing (WGS) were commonly used to determine tigecycline and colistin resistance mechanisms, specifically modifications in the structural and regulatory efflux (acrAB, OqxAB, kpgABC adeABC-FGH-IJK, mexAB-XY-oprJM and soxS, rarA robA, ramRAB marRABC, adeLRS, mexRZ and nfxb) and lipid A (pmrHFIJFKLM, lpxA, lpxC lpxD and mgrB, pmrAB, phoPQ,) genes respectively. Mutations in the ribosomal 16S rRNA operon rrnBC, also yielded resistance to tigecycline through target site modifications. The mcr-1 gene conferring resistance to colistin was identified via WGS, trans-complementation and a murine thigh infection model studies. Common detection methods are mainly antibiotic sensitivity testing with broth microdilution while molecular identification tools are mostly PCR and WGS. Spectrofluorometry, MALDI-TOF MS, micro-array and real-time multiplex PCR hold much promise for the future as new detection tools.