Emergence of multidrug-resistant Klebsiella pneumoniae isolates producing VIM-4 metallo-beta-lactamase, CTX-M-15 extended-spectrum beta-lactamase, and CMY-4 AmpC beta-lactamase in a Tunisian university hospital

High Prevalence of blaNDM Among Carbapenem Non-Susceptible Klebsiella pneumoniae in a Tunisian Hospital First Report of blaNDM-9, blaKPC-20, and blaKPC-26 Genes

Fifty-four carbapenem non-susceptible Klebsiella pneumoniae (CNSKP) isolates were collected from a Tunisian hospital over a period of 13 consecutive months. Carbapenemase production and the prevalence of carbapenemase-encoding genes were investigated using combined-disk test (CDT), modified Carba NP (mCarba NP) test, and UV-spectrophotometry method complemented by PCR experiments and sequencing. Carbapenemase production was detected by the mCarba NP test and CDT in 92.59% and 96.29% of the 54 CNSKP isolates, respectively; while imipenem hydrolysis was detected using UV-spectrophotometry in the crude extracts of 44 isolates. bla_NDM, bla_OXA-48-like, and bla_KPC carbapenemase-encoding genes were found in 48, 31, and 22 isolates, respectively. Remarkably, bla_NDM-9, bla_KPC-20, and bla_KPC-26 genes were reported. The co-occurrence of carbapenemase-encoding genes in a single isolate was detected in 62.96% of the isolates. The analysis of clonal relationships between the isolates by pulsed field gel electrophoresis revealed that the majority of them were genetically unrelated. Our investigation provides molecular data on enzymatic mechanism of carbapenem non-susceptibility among 54 CNSKP showing the dominance of bla_NDM, and comprises the first identification of bla_NDM-9, bla_KPC-20, and bla_KPC-26 genes in a Tunisia hospital.

Molecular Mechanism of the β-Lactamase Mediated β-Lactam Antibiotic Resistance of Pseudomonas aeruginosa Isolated From a Chinese Teaching Hospital

Pseudomonas aeruginosa can cause infections in the blood, lungs (pneumonia), or other parts of the body after surgery. To investigate the molecular characteristics of β-lactam antibiotic resistance of P. aeruginosa isolated from a hospital population between 2015 and 2017, in this study, the antimicrobial susceptibility and the resistance gene profile of the bacteria were determined. The Pulsed-field gel electrophoresis (PFGE) was used to characterize the clonal relatedness and sequencing and comparative genomic analysis were performed to analyze the structure of the resistance gene-related sequences. As a result, of the 260 P. aeruginosa strains analyzed, the resistance rates for 6 β-lactam antibiotics ranged from 4.6 to 9.6%. A total of 7 genotypes of 44 β-lactamase genes were identified in 23 isolates (8.9%, 23/260). Four transconjugants from different donors carrying bla_CARB-3 exhibited a phenotype of reduced susceptibility to piperacillin–tazobactam, ceftazidime, and cefepime, and 2 transconjugants harboring bla_IMP-45 exhibited a phenotype of reduced susceptibility to carbapenems. bla_CARB positive isolates (n = 12) presented six PFGE patterns, designated groups A to F. Two bla genes (bla_IMP-45 and bla_OXA-1) in PA1609 related to a class 1 integron (intI1-bla_IMP-45-bla_OXA-1-aac(6′)-Ib7-catB3-qacE∆1-sul1) were encoded on a plasmid (pPA1609-475), while the bla_CARB-3 gene of PA1616 also related to a class 1 integron was located on the chromosome. The results suggest that β-lactam antibiotic resistance and clonal dissemination exist in this hospital population. It indicates the necessity for molecular surveillance in tracking β-lactamase-producing strains and emphasizes the need for epidemiological monitoring.

Prevalence and molecular epidemiology of carbapenem-resistant Gram-negative bacilli and their resistance determinants in the Eastern Mediterranean Region over the last decade

Carbapenem resistance in Enterobacteriaceae, Acinetobacter baumannii and Pseudomonas aeruginosa is increasing worldwide, which has led the World Health Organization (WHO) to list these bacteria in the critical priority pathogens group. Infections by such pathogens pose a serious threat to hospitalised patients and are associated with clinical and economic consequences. What worsens the case is the weak pipeline of available antimicrobial agents to treat such infections and the absence of new drugs. The aim of this review was to shed light on all studies tackling carbapenem resistance in Enterobacteriaceae, A. baumannii and P. aeruginosa in the Eastern Mediterranean region, with indication for each country, description of studies timeline, prevalence of carbapenem resistance, and carbapenem resistance-encoding genes detected in these countries.

Carbapenemase Producing Gram-Negative Bacteria in Tunisia: History of Thirteen Years of Challenge

The wide spread of multidrug-resistant bacteria, particularly carbapenem-resistant Gram-negative bacteria (CR-GNB), constitutes a major public health threat worldwide, owing to the limited therapeutic options. This review will describe and uncover the Tunisian experience in the challenge against carbapenem resistance. Indeed, we illuminate on the dissemination of CR-GNB in different hospitals, animals, and other natural environments in this country. We resumed the different carbapenemase variants detected from various bacterial species and mapped their regional distribution, basing on Tunisian published data during a period extended from 2006, the date of its first description in Tunisia, to February 2019. We also resumed the different mobile genetic elements implicated in their dissemination. This review shows that the majority of the research reports focused in the north and the coastal cities in spite of the fact that KPC and IMP carbapenemases were uncommonly detected in our country. However, VIM, NDM-1, and OXA-48 enzymes were usually reported with the predominance of OXA-48 among Enterobacteriaceae. Furthermore, OXA-23, OXA-51, and OXA-58 carbapenemases constituted the main mechanism conferring carbapenem resistance among Acinetobacter baumannii in Tunisia. Collaborative efforts and raising awareness of the threat of antibiotic resistance are required in order to minimize the spread of multidrug-resistant bacteria.

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.

First report of VIM metallo-β-lactamase production in Escherichia coli and Klebsiella pneumoniae clinical isolates from Gaza Strip, Palestine

Introduction

Even though the increasing incidence of VIM-producing E. coli and K. pneumoniae has been reported worldwide, studies are still lacking in Palestine. The aim of this study was to screen carbapenem-resistant E. coli and K. pneumoniae bacteria in the Gaza Strip, Palestine and further to characterize carbapenemase-producing isolates.

Methods

A total of 69 E. coli and 27 K. pneumoniae isolates were obtained from three Gaza hospitals and recovered from urine, wound swabs, blood and ear discharge. The screening for metallo-β-lactamases (MBLs) was performed by using the imipenem-EDTA disc synergy test. The detection of β-lactamases genes, detection of non-β-lactam genes and the characterization of integrons were performed by PCR and sequencing. The clonal relationship among the isolates was determined by pulsed-field gel electrophoresis (PFGE).

Results

Our study showed that 4 E. coli (5.8%) and 5 K. pneumoniae (18.5%) were positive by the imipenem-EDTA disc synergy test. Bla _VIM-4 was detected in six isolates and bla _VIM-28 was identified in three isolates. The β-lactamases genes in the VIM-producing K. pneumoniae isolates were bla _CTX-M-15 (n=3), bla _CTX-M-14 (n=1), bla _SHV-1 (n=3), bla _SHV-12 (n=1), bla _TEM-1 (n=1) and bla _OXA-1 (n=1). Aac(6')-Ib-cr gene was confirmed in four E. coli and in two K. pneumoniae isolates. QnrS1 was identified in two K. pneumoniae isolates. The class 1 integron was identified with the different gene cassette; dfrA17-aadA5, dfrA5, dfrA12-orf-aadA2 and dfrA17-aadA5 were identified.

Conclusions

Our study indicated for the first time the emergence of multidrug-resistant VIM-containing K. pneumoniae and E. coli isolates of clinical origin in Gaza Strip hospitals.

Faecal indicator bacteria and antibiotic-resistant β-lactamase producing Escherichia coli in blackwater: a pilot study

The aim of this study was to identify and quantify faecal indicator bacteria in blackwater collected from a source separation unit and determine the amount of E. coli isolates resistant to antimicrobials and their potential to produce extended spectrum β-lactamases (ESβLs) and metallo-β-lactamases (MβLs), which hydrolyse the most important antibiotics used in clinical practice. Most of the isolates were resistant to amoxicillin with clavulanic acid (36.4 %), followed by ticarcillin with clavulanic acid (22.7 %) and tetracycline (18.2 %). ESβL-producing genes bla CTX-M and bla TEM were found in three (13.6 %) and four (18.2 %) E. coli strains, respectively, while MβL genes were found in two (9.1 %). By separating at source, this pilot study clearly shows that gastrointestinal bacteria of healthy people can be an important source of antibiotic resistance released into the environment through wastewaters. One way to prevent that is to treat wastewater with a combination of TiO2, UV light, or ozone, as successful methods to remove resistant bacteria and prevent their spread in the environment.

In vitro efficacy of gentamicin released from collagen sponge in eradication of bacterial biofilm preformed on hydroxyapatite surface

Biofilm-related infections of bones pose a significant therapeutic issue. In this article we present in vitro results of the efficacy of gentamicin released from a collagen sponge carrier against Staphylococcus aureus, Pseudomonas aeruginosa and Klebsiella pneumoniae biofilms preformed on hydroxyapatite surface. The results indicate that high local concentrations of gentamicin released from a sponge eradicate the biofilm formed not only by gentamicin-sensitive strains but, to some extent, also by those that display a resistance pattern in routine diagnostics. The data presented in this paper is of high clinical translational value and may find application in the treatment of bone infections.

Epidemiology of resistance and phenotypic characterization of carbapenem resistance mechanisms in Klebsiella pneumoniae isolates at Sahloul University Hospital-Sousse, Tunisia

Objective

To assess the prevalence of ESBL producing and carbapenem resistant Klebsiella pneumoniae isolated from in-come and out-come patients at Sahloul-university hospital.

Methods

A retrospective study over a 3 years period (January 2012 and December 2014) focused on 2160 strains of Klebsiella pneumoniae. Statistical analysis was carried out using SPSS program. ESBL detection was performed using a double disc diffusion method and carbapenemase detection was realized by Rosco-Disk kit.

Results

A total of 2160 Klebsiella pneumoniae strains were isolated during the period of the study, 26.2% (n=566) were ESBL-producers and 15.8% (n=342) showed resistance to carbapenem. The wards most affected by these strains were basically urology and intensive care units. Eighty four percent of studied strains (203/241) were resistant to temocillin, which correlate with the production of a class D (OXA-48-like) carbapenemase and 7% (17/241) showed sensitivity to EDTA and dipicolinic acid, which indicate the production of metallo-enzyme. The rate of resistance to colistin remains low.

Conclusion

Resistance of Enterobacteriaceae, including K. pneumoniae, to third generation cephalosporins (3rd GC) and carbapenem through the mechanism of ESBL and carbapenemases production is becoming increasingly worrying. This suggests a more rational use of antibiotics, as well as the rigorous application of hygiene measurement.

Antimicrobial susceptibility and characterization of metallo-β-lactamases, extended-spectrum β-lactamases, and carbapenemases of Bacillus cereus isolates

The susceptibility of 66 clinical and environmental B. cereus isolates were tested to selected antimicrobials by a broth microdilution method. All strains were resistant to β-lactams and susceptible to gentamicin and imipenem. Sixty-five (98.5%) isolates were susceptible to meropenem and ciprofloxacin and 74.2% to azithromycin. Significant differences in MIC values between environmental and clinical isolates were not demonstrated (p > 0.05). According to the disc diffusion method, 80.3%-98.5% of the strains were resistant to one or more of four cephalosporins. The presence of genes for B. cereus β-lactamases BCI, BCII, BCIII, extended-spectrum β-lactamases from the CTX and TEM family and the carbapenemases belonging to IMP and VIM family was studied. BlaII genes were expressed in all isolates; the PCR products for blaIII were also detected in two strains, but none of them was positive for blaI. The amplicon of the family bla_CTX-M, mostly M-1 and M-15, was confirmed among 68.2% of the isolates, while were bla_VIM-like genes determined in 21.2% of the samples.

Current Trends in Antimicrobial Resistance of Escherichia coli

Escherichia coli is the most common Gram-negative bacterial pathogen, presenting both a clinical and an epidemiological challenge. In the last decade, several successful multidrug-resistant high-risk strains, such as strain E. coli ST131 have evolved, mainly due to the growing selective pressure of antimicrobial use. These strains present enhanced fitness and pathogenicity, effective transmission and colonization abilities, global distribution due to efficient dissemination, and resistance to various antimicrobial resistances. Here, we describe the emerging trends and epidemiology of resistant E. coli, including carbapenemase-producing E. coli, E. coli ST131 and colistin resistant E. coli.

B1-Metallo-β-Lactamases: Where Do We Stand?

Metallo-β-Lactamases (MBLs) are class Bβ-lactamases that hydrolyze almost all clinically-availableβ-lactam antibiotics. MBLs feature the distinctive αβ/βα sandwich fold of the metallo-hydrolase/oxidoreductase superfamily and possess a shallow active-site groove containing one or two divalent zinc ions, flanked by flexible loops. According to sequence identity and zinc ion dependence, MBLs are classified into three subclasses (B1, B2 and B3), of which the B1 subclass enzymes have emerged as the most clinically significant. Differences among the active site architectures, the nature of zinc ligands, and the catalytic mechanisms have limited the development of a common inhibitor. In this review, we will describe the molecular epidemiology and structural studies of the most prominent representatives of class B1 MBLs (NDM-1, IMP-1 and VIM-2) and describe the implications for inhibitor design to counter this growing clinical threat.

Dissemination and genetic support of broad-spectrum beta-lactam-resistant Escherichia coli strain isolated from two Tunisian hospitals during 2004-2012

BACKGROUND

The dissemination of extended-spectrum β-lactamase (ESBL)-producing bacteria presented a great concern worldwide. Gram-negative organisms such as Escherichia coli and Klebsiella pneumoniae are the most frequently isolated pathogens responsible for nosocomial infections.

OBJECTIVES

The aim of this study was to investigate and to follow the emergence of resistance and the characterization of Extended-Spectrum Beta-Lactamases (ESBL) among broad-spectrum beta-lactam-Escherichia coli clinical isolates recovered from the military hospital and Habib Thameur hospital in Tunisia.

METHODS

A total of 113 E.coli isolates obtained during the period 2004 through 2012 showed a significant degree of multi-resistance. Among these strains, the double-disk synergy test confirmed the ESBL phenotype in 46 isolates. These included 32(70%) strains from Hospital A and 14(30%) from Hospital B.

RESULTS

The ESBL was identified as CTX-M-15. The ESBL resistance was transferred by a 60 kb plasmid CTXM-15-producing isolates were unrelated according to the PFGE analysis and characterization of the regions surrounding the blaCTX-M-15 showed the ISEcp1 elements located in the upstream region of the bla gene and 20 of them truncated by IS26.

CONCLUSION

ESBL producing E. coli strains are a serious threat in the community in Tunisia and we should take into consideration any possible spread of such epidemiological resistance.

Dissemination of metallo-β-lactamase in Pseudomonas aeruginosa isolates in Egypt: mutation in blaVIM-4

This study was designed to investigate the prevalence of metallo-β-lactamase (MBL) in Pseudomonas aeruginosa isolates collected from Suez Canal University Hospital in Ismailia, Egypt. Antibiotic susceptibility testing and phenotypic and genotypic screening for MBLs were performed on 147 isolates of P. aeruginosa. MICs were determined by agar dilution method for carbapenem that was ≥2 μg/mL for meropenem. MBL genes were detected by multiplex and monoplex PCR for P. aeruginosa-harbored plasmids. Mutation profile of sequenced MBL genes was screened using online software Clustal Omega. Out of 147 P. aeruginosa, 39 (26.5%) were carbapenem-resistant isolates and 25 (64%) were confirmed to be positive for MBLs. The susceptibility rate of P. aeruginosa toward polymyxin B and norfloxacin was 99% and 88%, respectively. Identification of collected isolates by API analysis and constructed phylogenetic tree of 16S rRNA showed that the isolates were related to P. aeruginosa species. The frequency of blaGIM-1, blaSIM-1, and blaSPM-1 was 52%, 48%, and 24%, respectively. BlaVIM and blaIMP-like genes were 20% and 4% and the sequences confirm the isolate to be blaVIM-1, blaVIM-2, blaVIM-4, and blaIMP-1. Three mutations were identified in blaVIM-4 gene. Our study emphasizes the high occurrence of multidrug-resistant P. aeruginosa-producing MBL enzymes.

The global epidemiology of carbapenemase-producing Enterobacteriaceae

Carbapenemase-producing Enterobacteriaceae (CPE) are an important and increasing threat to global health. Both clonal spread and plasmid-mediated transmission contribute to the ongoing rise in incidence of these bacteria. Among the 4 classes of β-lactamases defined by the Ambler classification system, the carbapenemases that confer carbapenem resistance in Enterobacteriaceae belong to 3 of them: Class A (K. pneumoniae carbapenemases, KPC), Class B (metallo-β-lactamases, MBL including New Delhi metallo-β-lactamases, NDM) and Class D (OXA-48-like carbapenemases). KPC-producing CPE are the most commonly occurring CPE in the United States. MBL-producing CPE have been most commonly associated with the Indian Subcontinent as well as with specific countries in Europe, including Romania, Denmark, Spain, and Hungary. The epicenter of OXA-48-like-producing is in Turkey and surrounding countries. Detailed knowledge of the epidemiology and molecular characteristics of CPE is essential to stem the spread of these pathogens.

Epidemiology of Carbapenem Resistant Klebsiella pneumoniae Infections in Mediterranean Countries

Infections by Carbapenem-Resistant Enterobacteriaceae (CRE), in particular, carbapenem-resistant Klebsiella pneumoniae (CRKp), are a significant public health challenge worldwide. Resistance to carbapenems in enterobacteriaceae is linked to different mechanisms, including the production of the various types of enzymes like KPC, VIM, IMP, NDM, and OXA-48. Despite several attempts to control the spread of these infections at the local and national level, the epidemiological situation for CRKp had worsened in the last years in the Mediterranean area. The rate and types of CRKp isolates greatly differ in the various Mediterranean countries. KPC-producing K. pneumoniae is diffused particularly in the European countries bordering the Mediterranean Sea and is endemic in Greece and Italy. On the contrary, OXA-48-producing K. pneumoniae is endemic in Turkey and Malta and diffused at inter-regional level particularly in some

North African and Middle East countries. The spread of these multiresistant pathogens in the world and the Mediterranean countries has been related to various epidemiological factors including the international transfer of patients coming from endemic areas.

The Molecular Epidemiology and Genetic Environment of Carbapenemases Detected in Africa

Research articles describing carbapenemases and their genetic environments in Gram-negative bacteria were reviewed to determine the molecular epidemiology of carbapenemases in Africa. The emergence of resistance to the carbapenems, the last resort antibiotic for difficult to treat bacterial infections, affords clinicians few therapeutic options, with a resulting increase in morbidities, mortalities, and healthcare costs. However, the molecular epidemiology of carbapenemases throughout Africa is less described. Research articles and conference proceedings describing the genetic environment and molecular epidemiology of carbapenemases in Africa were retrieved from Google Scholar, Scifinder, Pubmed, Web of Science, and Science Direct databases. Predominant carbapenemase genes so far described in Africa include the blaOXA-48 type, blaIMP, blaVIM, and blaNDM in Acinetobacter baumannii, Klebsiella pneumoniae, Enterobacter cloacae, Citrobacter spp., and Escherichia coli carried on various plasmid types and sizes, transposons, and integrons. Class D and class B carbapenemases, mainly prevalent in A. baumannii, K. pneumoniae, E. cloacae, Citrobacter spp., and E. coli were the commonest carbapenemases. Carbapenemases are mainly reported in North and South Africa as under-resourced laboratories, lack of awareness and funding preclude the detection and reporting of carbapenemase-mediated resistance. Consequently, the true molecular epidemiology of carbapenemases and their genetic environment in Africa is still unknown.

Carbapenemase-producing Gram-negative bacteria: current epidemics, antimicrobial susceptibility and treatment options

ABSTRACT 

Carbapenemases, with versatile hydrolytic capacity against β-lactams, are now an important cause of resistance of Gram-negative bacteria. The genes encoding for the acquired carbapenemases are associated with a high potential for dissemination. In addition, infections due to Gram-negative bacteria with acquired carbapenemase production would lead to high clinical mortality rates. Of the acquired carbapenemases, Klebsiella pneumoniae carbapenemase (Ambler class A), Verona integron-encoded metallo-β-lactamase (Ambler class B), New Delhi metallo-β-lactamase (Ambler class B) and many OXA enzymes (OXA-23-like, OXA-24-like, OXA-48-like, OXA-58-like, class D) are considered to be responsible for the worldwide resistance epidemics. As compared with monotherapy with colistin or tigecycline, combination therapy has been shown to effectively lower case-fatality rates. However, development of new antibiotics is crucial in the present pandrug-resistant era.

The spread of carbapenemase-producing bacteria in Africa: a systematic review

BACKGROUND

Carbapenems are the last line of defence against ever more prevalent MDR Gram-negative bacteria, but their efficacy is threatened worldwide by bacteria that produce carbapenemase enzymes. The epidemiology of bacteria producing carbapenemases has been described in considerable detail in Europe, North America and Asia; however, little is known about their spread and clinical relevance in Africa.

METHODS

We systematically searched in PubMed, EBSCOhost, Web of Science, Scopus, Elsevier Masson Consulte and African Journals Online, international conference proceedings, published theses and dissertations for studies reporting on carbapenemase-producing bacteria in Africa. We included articles published in English or French up to 28 February 2014. We calculated the prevalence of carbapenemase producers only including studies where the total number of isolates tested was at least 30.

RESULTS

Eighty-three studies were included and analysed. Most studies were conducted in North Africa (74%, 61/83), followed by Southern Africa (12%, 10/83), especially South Africa (90%, 9/10), West Africa (8%, 7/83) and East Africa (6%, 6/83). Carbapenemase-producing bacteria were isolated from humans, the hospital environment and community environmental water samples, but not from animals. The prevalence of carbapenemase-producing isolates in hospital settings ranged from 2.3% to 67.7% in North Africa and from 9% to 60% in sub-Saharan Africa.

CONCLUSIONS

Carbapenemase-producing bacteria have been described in many African countries; however, their prevalence is poorly defined and has not been systematically studied. Antibiotic stewardship and surveillance systems, including molecular detection and genotyping of resistant isolates, should be implemented to monitor and reduce the spread of carbapenemase-producing bacteria.

Presence of fimH, mrkD, and irp2 virulence genes in KPC-2-producing Klebsiella pneumoniae isolates in Recife-PE, Brazil

Klebsiella pneumoniae strains can produce different virulence factors, such as fimbrial adhesins and siderophores, which are important in the colonization and development of the infection. The aims of this study were to determine the occurrence of fimH, mrkD, and irp2 virulence genes in 22 KPC-2-producing K. pneumoniae isolates as well as 22 not producing-KPC isolates, from patients from different hospitals in Recife-PE, Brazil, and also to analyze the clonal relationship of the isolates by enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR). The genes were detected by PCR and DNA sequencing. The bla KPC-2 gene was identified in 22 KPC-positive isolates. On analyzing the antimicrobial susceptibility profile of the isolates, it was detected that polymyxin and amikacin were the antimicrobials of best activity against K. pneumoniae. On the other hand, five isolates exhibited resistance to polymyxin. In the KPC-positive group, was observed a high rate of resistance to cephalosporins, followed by carbapenems. Molecular typing by ERIC-PCR detected 38 genetic profiles, demonstrating a multiclonal spread of the isolates analyzed. It was observed that the virulence genes irp2, mrkD, and fimH were seen to have together a higher frequency in the KPC-positive group. The accumulation of virulence genes of KPC-positive K. pneumoniae isolates, observed in this study, along with the multi-resistance impose significant therapeutic limitations on the treatment of infections caused by K. pneumoniae.

Epidemiology of carbapenemase-producing Enterobacteriaceae and Acinetobacter baumannii in Mediterranean countries

The emergence and global spread of carbapenemase-producing Enterobacteriaceae and Acinetobacter baumannii are of great concern to health services worldwide. These β-lactamases hydrolyse almost all β-lactams, are plasmid-encoded, and are easily transferable among bacterial species. They are mostly of the KPC, VIM, IMP, NDM, and OXA-48 types. Their current extensive spread worldwide in Enterobacteriaceae is an important source of concern. Infections caused by these bacteria have limited treatment options and have been associated with high mortality rates. Carbapenemase producers are mainly identified among Klebsiella pneumoniae, Escherichia coli, and A. baumannii and still mostly in hospital settings and rarely in the community. The Mediterranean region is of interest due to a great diversity and population mixing. The prevalence of carbapenemases is particularly high, with this area constituting one of the most important reservoirs. The types of carbapenemase vary among countries, partially depending on the population exchange relationship between the regions and the possible reservoirs of each carbapenemase. This review described the epidemiology of carbapenemases produced by enterobacteria and A. baumannii in this part of the world highlighting the worrisome situation and the need to screen and detect these enzymes to prevent and control their dissemination.

blaCTX-M-15-carrying F2:A-:B- plasmid in Escherichia coli from cattle milk in Tunisia

Extended-spectrum β-lactamases (ESBL) are widespread enzymes in animals, and the risk of transmission of ESBL genes to humans has become a major issue. In Tunisia, recent data showed a high prevalence of ESBL-producing Escherichia coli isolates in healthy animals, mostly in chickens. In this study, we report the first data on ESBL in diseased Tunisian animals (chickens and cattle), highlighting a major difference in ESBL prevalence in the infectious versus noninfectious E. coli flora. Interestingly, the only ESBL producer was an ST10 E. coli from a cattle, and not from chicken. Moreover, this E. coli isolate harbored the bla(CTX-M-15) gene on an F2:A-:B- plasmid, a combination frequently found in humans. This plasmid was also highly similar to a bla(CTX-M-15) F2:A-:B- plasmid recently reported in cattle in France. Altogether, this study is also the first report of the bla(CTX-M-15) gene in food animals in Tunisia, and, to our best knowledge, the first report of an ESBL producer in cattle in Africa. Since this plasmid was recognized in cattle in France and worldwide in humans, the question of its origin in Tunisian cattle is open. The detection of ESBL producers in milk in Tunisia may also constitute a risk of ESBL transmission from animals to humans through food consumption.

Multidrug resistance genes, including bla(KPC) and bla(CTX)-M-2, among Klebsiella pneumoniae isolated in Recife, Brazil

INTRODUCTION

The prevalence of cephalosporins and carbapenem-resistant Klebsiella pneumoniae strains is rising in Brazil, with potential serious consequences in terms of patients' outcomes and general care.

METHODS

This study characterized 24 clinical isolates of K. pneumoniae from two hospitals in Recife, Brazil, through the antimicrobial susceptibility profile, analyses of β-lactamase genes (bla(TEM), bla(SHV),bla(CTX-M), bla(KPC), bla(VIM), bla(IMP), and bla(SPM), plasmidial profile and ERIC-PCR (Enterobacterial repetitive intergenic consensus-polymerase chain reaction).

RESULTS

ERIC-PCR and plasmidial analysis grouped the isolates in 17 and 19 patterns, respectively. Six isolates from one hospital presented the same pattern by ERIC-PCR, indicating clonal dissemination. All isolates presented bla(SHV), 62.5% presented bla(CTX)-M-2, 29% bla(TEM), and 41.7% bla(KPC). Metallo-β-lactamase genes bla(VIM), bla(IMP), and bla(SPM) not detected. Eleven isolates were identified carrying at least 3 β-lactamase studied genes, and 2 isolates carried bla(SHV), bla(TEM), bla (CTX-M-2) and bla(KPC) simultaneously.

CONCLUSIONS

The accumulation of resistance genes in some strains, observed in this study, imposes limitations in the therapeutic options available for the treatment of infections caused by K. pneumoniae in Recife, Brazil. These results should alert the Brazilian medical authorities to establish rigorous methods for more efficiently control the dissemination of antimicrobial resistance genes in the hospital environment.

High prevalence of VIM-4 and NDM-1 metallo-β-lactamase among carbapenem-resistant Enterobacteriaceae

The purpose of this study was to identify the mechanisms leading to carbapenem resistance among multidrug-resistant Enterobacteriaceae isolates recovered from hospitalized patients with nosocomial infections in Mubarak Al Kabeer Hospital, Kuwait. Fourteen carbapenem-resistant Enterobacteriaceae isolates were obtained from inpatients in different wards and intensive care units between April 2009 and February 2011. Antibiotic susceptibilities were determined using the E-test method. Genes encoding β-lactamases were characterized by specific PCR amplification, sequencing and conjugation assays. All isolates were identified as metallo-β-lactamase (MBL) producers using phenotypic and molecular methods. Eleven of the 14 isolates produced VIM-4 (six Klebsiella pneumoniae, three Escherichia coli, one Enterobacter cloacae and one Klebsiella oxytoca). Three K. pneumoniae isolates produced the MBL NDM-1 and co-produced the plasmid-encoded AmpC CMY-4. The VIM-4-producing isolates co-produced extended-spectrum β-lactamases including CTX-M-15 and some SHV derivatives. The VIM-4 gene was not transferable by conjugation studies of six selected strains. We demonstrated here the emergence of VIM-4- and NDM-1-producing isolates in the largest teaching hospital in Kuwait.

Antibiotic resistance shaping multi-level population biology of bacteria

Antibiotics have natural functions, mostly involving cell-to-cell signaling networks. The anthropogenic production of antibiotics, and its release in the microbiosphere results in a disturbance of these networks, antibiotic resistance tending to preserve its integrity. The cost of such adaptation is the emergence and dissemination of antibiotic resistance genes, and of all genetic and cellular vehicles in which these genes are located. Selection of the combinations of the different evolutionary units (genes, integrons, transposons, plasmids, cells, communities and microbiomes, hosts) is highly asymmetrical. Each unit of selection is a self-interested entity, exploiting the higher hierarchical unit for its own benefit, but in doing so the higher hierarchical unit might acquire critical traits for its spread because of the exploitation of the lower hierarchical unit. This interactive trade-off shapes the population biology of antibiotic resistance, a composed-complex array of the independent "population biologies." Antibiotics modify the abundance and the interactive field of each of these units. Antibiotics increase the number and evolvability of "clinical" antibiotic resistance genes, but probably also many other genes with different primary functions but with a resistance phenotype present in the environmental resistome. Antibiotics influence the abundance, modularity, and spread of integrons, transposons, and plasmids, mostly acting on structures present before the antibiotic era. Antibiotics enrich particular bacterial lineages and clones and contribute to local clonalization processes. Antibiotics amplify particular genetic exchange communities sharing antibiotic resistance genes and platforms within microbiomes. In particular human or animal hosts, the microbiomic composition might facilitate the interactions between evolutionary units involved in antibiotic resistance. The understanding of antibiotic resistance implies expanding our knowledge on multi-level population biology of bacteria.

Carbapenemases: Partners in crime

Carbapenemases, β-lactamases that inactivate carbapenems and most β-lactam antibiotics, are most widely known for their ability to confer resistance to β-lactams. They include serine carbapenemases, such as the widespread KPC family of enzymes, and the metallo-β-lactamases that contain the IMP, NDM and VIM enzyme families acquired by Gram-negative bacteria on transferable elements. These enzymes are almost always produced by organisms that encode at least one other β-lactamase, with as many as eight different β-lactamase genes detected in a single isolate. This consortium of β-lactamases includes a full spectrum of molecular and biochemical characteristics, providing the producing organism with a range of catalytic activities. In addition to the variety of β-lactamases found in carbapenemase-producing Gram-negative pathogens are multiple other resistance factors, especially aminoglycoside-modifying enzymes and 16S rRNA methylases that confer resistance to aminoglycosides. Other acquired genes encode fluoroquinolone, trimethoprim, sulfonamide, rifampicin and chloramphenicol resistance determinants on mobile elements that travel together with β-lactamase genes. Thus, the recent proliferation of transferable carbapenemases serves to magnify resistance to virtually all antibiotic classes. Judicial use of current antibiotics and a quest for novel antibacterial agents are necessary, as multidrug-resistant bacteria continue to multiply.

Carbapenemases in Klebsiella pneumoniae and other Enterobacteriaceae: an evolving crisis of global dimensions

SUMMARY

The spread of Enterobacteriaceae, primarily Klebsiella pneumoniae, producing KPC, VIM, IMP, and NDM carbapenemases, is causing an unprecedented public health crisis. Carbapenemase-producing enterobacteria (CPE) infect mainly hospitalized patients but also have been spreading in long-term care facilities. Given their multidrug resistance, therapeutic options are limited and, as discussed here, should be reevaluated and optimized. Based on susceptibility data, colistin and tigecycline are commonly used to treat CPE infections. Nevertheless, a review of the literature revealed high failure rates in cases of monotherapy with these drugs, whilst monotherapy with either a carbapenem or an aminoglycoside appeared to be more effective. Combination therapies not including carbapenems were comparable to aminoglycoside and carbapenem monotherapies. Higher success rates have been achieved with carbapenem-containing combinations. Pharmacodynamic simulations and experimental infections indicate that modification of the current patterns of carbapenem use against CPE warrants further attention. Epidemiological data, though fragmentary in many countries, indicate CPE foci and transmission routes, to some extent, whilst also underlining the lack of international collaborative systems that could react promptly and effectively. Fortunately, there are sound studies showing successful containment of CPE by bundles of measures, among which the most important are active surveillance cultures, separation of carriers, and assignment of dedicated nursing staff.

Antimicrobial susceptibility and genetic similarity of ESBL-positive Klebsiella pneumoniae strains

INTRODUCTION

Twenty-eight isolates of extended-spectrum β-lactamase (ESBL)-positive Klebsiella pneumoniae were studied.

MATERIAL AND METHODS

The strains were cultured from different clinical specimens obtained from children hospitalised at the University Hospital in Bydgoszcz. Seventeen strains were isolated from colonization and eleven from clinical infection. Isolation and identification of bacteria were performed using routine methods at the clinical microbiology laboratory. Production of ESBL was assessed using the double disk synergy test. The susceptibility to imipenem and tigecycline was tested by the Etest. The susceptibility to gentamicin and ciprofloxacin was tested by the agar dilution method. The genomic DNA was extracted from the strains separated by pulsed-field gel electrophoresis (PFGE) after digesting with XbaI endonuclease.

RESULTS

Among analysed K. pneumoniae strains all were susceptible to imipenem, 21 (75.0%) were susceptible to tigecycline, 14 (50.0%) to gentamicin and 5 (17.9%) to ciprofloxacin. Molecular typing results revealed a great genetic diversity among K. pneumoniae isolates. All repeated PFGE patterns were detected in seven K. pneumoniae isolates. Among identical K. pneumoniae strains four susceptibility patterns were detected.

CONCLUSIONS

The results of the study suggest that establishing strains' similarity in epidemiological investigations should be based on results obtained by several methods, and that each phenotyping method should be complemented with genetic research.

VIM-4 carbapenemase-producing Enterobacter cloacae in the United Arab Emirates

Screening 34 carbapenem non-susceptible Enterobacteriaceae recovered in Abu Dhabi hospitals identified an Enterobacter cloacae strain carrying bla(VIM-4) , bla(CMY-4) and bla(CTX-M-15) . It was isolated from the urine of an Egyptian patient repeatedly hospitalized and treated with broad-spectrum antibiotics, including carbapenems, in the United Arab Emirates. The bla(VIM-4) coding class I integron, highly similar to In416, was carried on a 175-kilobase non-conjugative incA/C type plasmid also hybridizing with the bla(CMY-4) probe. This is the first detailed report on the isolation of a Verona integron-encoded metallo-β-lactamase (VIM) -producing enteric bacterium in the Arabian Peninsula with characteristics suggestive of spreading from the Mediterranean region.

Extensive dissemination of CTX-M-1- and CMY-2-producing Escherichia coli in poultry farms in Tunisia

We characterized 67 Escherichia coli isolates with reduced susceptibility to cefotaxime obtained from 136 samples of healthy broilers housed in 36 Tunisian farms. All these isolates harboured blaCTX-M-1 and/or blaCMY-2 genes located mostly on self-conjugative IncI1 plasmids. qnrS1, qnrA6 and aac(6')-Ib-cr were detected in six isolates. Considerable genetic diversity was detected among isolates from different farms. To our knowledge, this is the first detailed documentation of a high occurrence of blaCTX-M-1 and blaCMY-2 in E. coli at the poultry farm level in Tunisia as well as the first description of plasmid-mediated quinolone resistance in food animals in Tunisia which may contribute to the dissemination of these genes throughout Tunisia.

First detection of VIM-4 metallo-β-lactamase-producing Escherichia coli in Russia

An Escherichia coli isolate co-producing VIM-4 metallo-β-lactamase and CTX-M-15 extended spectrum β-lactamase was recovered from the urine of a patient with head trauma in Moscow, Russia. The bla(VIM-4) and bla(CTX-M-15) genes were carried, respectively, by transmissible plasmids of IncW and IncI1 groups. The nucleotide sequence of the VIM-4-encoding integron was nearly identical to that of In416, which represent a large group of structurally related integrons previously found in Enterobacteriaceae all around the Mediterranean basin. This is the first report of a metallo-β-lactamase-producing E. coli in Russia.

Nosocomial outbreak of imipenem-resistant Pseudomonas aeruginosa producing VIM-2 metallo-β-lactamase in a kidney transplantation unit

Background

Twenty four non replicate imipenem resistant P. aeruginosa were isolated between January and November 2008, in the kidney transplantation unit of Charles Nicolle Hospital of Tunis (Tunisia). This study was conducted in order to establish epidemiological relationship among them and to identify the enzymatic mechanism involved in imipenem resistance.

Methods

Analysis included antimicrobial susceptibility profile, phenotypic (imipenem-EDTA synergy test) and genotypic detection of metallo-β-lactamase (MBL) (PCR), O-serotyping and pulsed-field gel electrophoresis.

Results

All strains showed a high level of resistance to all antimicrobials tested except to colistin. The presence of MBL showed concordance between phenotypic and genotypic methods. Sixteen isolates were identified as VIM-2 MBL-producers and 13 of them were serotype O4 and belonged to a single pulsotype (A).

Conclusions

This study describes an outbreak of VIM-2-producing P. aeruginosa in a kidney transplantation unit. Clinical spread of bla_VIM-2 gene is a matter of great concern for carbapenem resistance in Tunisia.

Comparative study on occurrence of class A and class C β -lactamase genes and their co-occurrence in Indian Enterobacteriaceae during years 2009 and 2010

OBJECTIVE

To determine the occurrence of class A and class C β-lactamase genes and their co-occurrence in Indian Enterobacteriaceae.

METHODS

52 third generation cephalosporin resistant isolates were phenotypically detected by combination disk method and screened by PCR to identify class A and class C type β-lactamase genes.

RESULTS

Of the 52 isolates, 94.2% (49) were found harboring any of the bla(ESBL(s)). bla(CTX-M), bla(SHV) and bla(TEM) were present in 82.6% (43/52), 59.6% (31/52), and 42.3% (22/52) isolates, respectively. Of the 49 ESBL positive isolates 57.1% (28/49) showed co-occurrence of bla(ampC) with bla(ESBL(s)). On the contrary, the collection from 2009 showed their co-occurrence in 81.4% isolates.

CONCLUSIONS

The comparative study shows a downward trend for co-existence of bla(ESBL(s)) with bla(ampC) from 2009 to 2010. Further large scale studies are needed to address the co-occurrence of class A and class C β-lactamases in India and the resistance trend occurring over a period of time.

In vitro activity of carbapenems alone and in combination with amikacin against KPC-producing Klebsiella pneumoniae

Background

Although carbapenems are the primary treatment strategy for invasive infections caused by ESBL bacteria, case reports of these pathogens with reduced carbapenem susceptibility have emerged. One potential treatment modality is to optimize the use of anti-infectives with combination therapy. We evaluated the activity of carbapenems alone and in combination with amikacin against these clinical isolates.

Methods

Time-kill studies evaluated ertapenem (ETP), imipenem (IPM), meropenem (MEM), and amikacin (AMK) against 4 non-duplicate clinical isolates of Klebsiella pneumoniae that were resistant to these antibiotics. Synergy was defined as ≥ 2 log₁₀ decrease CFU/mL at 24 h for the combination when compared with the most active single agent of the combination, plus the number of surviving organisms for the antimicrobial combination was ≥ 2 log₁₀ less than the initial inoculum.

Results

All isolates carried bla_KPC-3 and genes encoding TEM-1 and SHV-11/-36; and were resistant to carbapenems (MIC at ≥ 8 μg/mL for ETP, MEM and IPM) and AMK (MIC 32 μg/mL) using broth microdilution. As monotherapy, none of the carbapenems nor AMK achieved and maintained bactericidal activity defined as ≥ 99.9% or > 3 log₁₀ killing. From time-kill studies, synergy was demonstrated for MEM and IPM in combination with AMK over the entire 24 h against all isolates. In addition, MEM and IPM with AMK achieved and maintained bactericidal activity (≥ 99.9% killing) at 24 h against 2 and 1 isolate(s), respectively. Bactericidal activity and synergy were not observed for ETP combinations.

Conclusions

The combination of MEM or IPM with AMK displayed synergistic activity against KPC-3-producing K. pneumoniae isolates.

Keywords

ESBL; Klebsiella pneumoniae; KPC; Carbapenemase; Time-kill; Meropenem; Amikacin; Imipenem; Ertapenem; Carbapenem; Synergy

Characterization and molecular epidemiology of extended spectrum beta-lactamase producing Enterobacter cloacae isolated from a Tunisian hospital

In 2009, out of the 66 nonrepetitive Enterobacter cloacae collected at Charles Nicolle hospital in Tunisia, 44 were extended spectrum β-lactamase (ESBL) producers. The aim of the current study was to detect and characterize the genes encoding the ESBLs including blaTEM, blaSHV, and blaCTX-M groups by polymerase chain reaction and sequencing. Pulsed-field gel electrophoresis (PFGE) analysis was used to determine the genetic relatedness between isolates. All strains were susceptible to carbapenems. They were resistant to fluoroquinolones, gentamicin, tobramycin, and trimethoprim+sulfamethoxazole but variably resistant to netilmicin, amikacin, and tetracyclines. Sequence analysis of the polymerase chain reaction products revealed the presence of blaCTX-M-15 (39 strains), blaSHV-12 (6 strains), and blaSHV-27 (1 strain). The coexistence of two ESBLs was observed in two isolates harboring, respectively, SHV-12+CTX-M-15 and SHV-27+CTX-M-15. PFGE revealed 36 unrelated profiles. Diffusion of E. cloacae producing CTX-M-15 ESBL in our hospital is the consequence of dissemination of identical or related plasmids harboring the CTX-M-15 gene.