Multidrug resistance in Gram-negative bacteria that produce extended-spectrum beta-lactamases (ESBLs)

Genome characterization, pathogenicity, and evaluation of therapeutics of Klebsiella aerogenes in Bombyx larvae infection model

Antibiotic resistance against human pathogenic bacteria is a global problem and the issue is becoming increasingly serious. Klebsiella aerogenes, a Gram-negative pathogen, is usually found in soil and water, but there are increasing number of reports in on isolation of antibiotic-resistant strains of it. Here, we report the draft genome of a food-borne Klebsiella aerogenes strain isolated from street food of Dhaka, Bangladesh. The WGS analysis revealed the presence of a number of virulence genes and antibiotic-resistance genes. Using the infection model of the larvae of the silk moth, Bombyx mori, we show that the K. aerogenes strain killed larvae within 72 h of injection into the hemolymph (blood) or midgut. Although the strain showed resistance to ampicillin in vitro among the antibiotics tested, it showed sensitivity to ampicillin in vivo in Bombyx larvae. Direct injection of aqueous extracts of hog plum or Indian gooseberry into the midgut of larvae infected with K. aerogenes increased larval survival rate to ~ 75% after 72 h. These results indicate that Bombyx larvae could be used to carry out in vivo screening of plant extracts with potential therapeutic effects against pathogenic bacteria like K. aerogenes.

Molecular Characterization of Extended-Spectrum ß-Lactamases-Producing Escherichia coli Isolated from a Greek Food Testing Laboratory

Background/Objectives: Over the past decade, extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli have emerged as a significant public health concern due to their potential to spread beyond clinical settings and healthy carriers, in various environments, including in animal source foods. This study seeks to investigate the molecular characteristics of ESBL-producing E. coli strains isolated from food of animal origin, with a focus on chromosomal typing, plasmid typing, and the description of the associated resistance genes' genetic environment. Methods: Ninety-seven food of animal origin samples were tested for E. coli isolates resistant to cefotaxime. The resulting isolates were then subjected to antimicrobial susceptibility testing and PCR analysis to detect beta-lactamase genes. Additional assays, encompassing mating-out procedures, molecular typing utilizing Pulsed-Field Gel Electrophoresis, Multilocus Sequence Typing Analysis, and Oxford Nanopore Technology Lite whole plasmid sequencing, were also conducted. Results:E. coli was detected in 26 raw food specimens, generating a percentage of 27%. Fourteen of the current isolates (14%) were resistant to third generation cephalosporins, producing CTX-M-1, CTX-M-15, CTX-M-55, and SHV-12 beta-lactamases. The respective genes were accompanied by Insertion Sequences ISEcp1 and IS26, facilitating their transfer. Among plasmids harboring ESBL genes, representatives belonging to incI1 incompatibility group prevailed (5/8), followed by IncY and IncX3. Most plasmids proved conjugative. Diversity of molecular fingerprints of ESBL producing E. coli was revealed. Conclusions: To the best our knowledge, this study is the first to describe the molecular characteristics of E. coli isolates producing ESBLs sourced from foods of animal origin in Greece. The prevalence of ESBLs in our confined food collection is primarily associated with the very successful IncI1 plasmids, which were not linked to a specific E. coli genetic background. This lack of association confirms that horizontal plasmid transfer plays a more significant role than clonal dissemination in the spread of ESBL-mediated cephalosporin resistance.

A study at the wildlife-livestock interface unveils the potential of feral swine as a reservoir for extended-spectrum β-lactamase-producing Escherichia coli

Wildlife is known to serve as carriers and sources of antimicrobial resistance (AMR). Due to their unrestricted movements and behaviors, they can spread antimicrobial resistant bacteria among livestock, humans, and the environment, thereby accelerating the dissemination of AMR. Extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae is one of major concerns threatening human and animal health, yet transmission mechanisms at the wildlife-livestock interface are not well understood. Here, we investigated the mechanisms of ESBL-producing bacteria spreading across various hosts, including cattle, feral swine, and coyotes in the same habitat range, as well as from environmental samples over a two-year period. We report a notable prevalence and clonal dissemination of ESBL-producing E. coli in feral swine and coyotes, suggesting their persistence and adaptation within wildlife hosts. In addition, in silico studies showed that horizontal gene transfer, mediated by conjugative plasmids and insertion sequences elements, may play a key role in spreading the ESBL genes among these bacteria. Furthermore, the shared gut resistome of cattle and feral swine suggests the dissemination of antibiotic resistance genes at the wildlife-livestock interface. Taken together, our results suggest that feral swine may serve as a reservoir of ESBL-producing E. coli.

Risk factors for extended-spectrum beta-lactamase (ESBL)-producing E. coli carriage among children in a food animal-producing region of Ecuador: A repeated measures observational study

BACKGROUND

The spread of antibiotic-resistant bacteria may be driven by human-animal-environment interactions, especially in regions with limited restrictions on antibiotic use, widespread food animal production, and free-roaming domestic animals. In this study, we aimed to identify risk factors related to commercial food animal production, small-scale or "backyard" food animal production, domestic animal ownership, and practices related to animal handling, waste disposal, and antibiotic use in Ecuadorian communities.

METHODS AND FINDINGS

We conducted a repeated measures study from 2018 to 2021 in 7 semirural parishes of Quito, Ecuador to identify determinants of third-generation cephalosporin-resistant E. coli (3GCR-EC) and extended-spectrum beta-lactamase E. coli (ESBL-EC) in children. We collected 1,699 fecal samples from 600 children and 1,871 domestic animal fecal samples from 376 of the same households at up to 5 time points per household over the 3-year study period. We used multivariable log-binomial regression models to estimate relative risks (RR) of 3GCR-EC and ESBL-EC carriage, adjusting for child sex and age, caregiver education, household wealth, and recent child antibiotic use. Risk factors for 3GCR-EC included living within 5 km of more than 5 commercial food animal operations (RR: 1.26; 95% confidence interval (CI): 1.10, 1.45; p-value: 0.001), household pig ownership (RR: 1.23; 95% CI: 1.02, 1.48; p-value: 0.030) and child pet contact (RR: 1.23; 95% CI: 1.09, 1.39; p-value: 0.001). Risk factors for ESBL-EC were dog ownership (RR: 1.35; 95% CI: 1.00, 1.83; p-value: 0.053), child pet contact (RR: 1.54; 95% CI: 1.10, 2.16; p-value: 0.012), and placing animal feces on household land/crops (RR: 1.63; 95% CI: 1.09, 2.46; p-value: 0.019). The primary limitations of this study are the use of proxy and self-reported exposure measures and the use of a single beta-lactamase drug (ceftazidime with clavulanic acid) in combination disk diffusion tests for ESBL confirmation, potentially underestimating phenotypic ESBL production among cephalosporin-resistant E. coli isolates. To improve ESBL determination, it is recommended to use 2 combination disk diffusion tests (ceftazidime with clavulanic acid and cefotaxime with clavulanic acid) for ESBL confirmatory testing. Future studies should also characterize transmission pathways by assessing antibiotic resistance in commercial food animals and environmental reservoirs.

CONCLUSIONS

In this study, we observed an increase in enteric colonization of antibiotic-resistant bacteria among children with exposures to domestic animals and their waste in the household environment and children living in areas with a higher density of commercial food animal production operations.

Prevalence of extended-spectrum β-lactamase-producing Enterobacterales in retail sheep meat from Zagazig city, Egypt

Background

The goal of this study was to investigate the prevalence of extended-spectrum β-lactamase production in Enterobacterales isolated from retail sheep meat in Zagazig, Egypt.

Methods

One hundred random samples of sheep meat were collected from different retail butcher shops (n = 5) in the city of Zagazig, Egypt. Bacterial isolates were identified by MALDI-TOF MS and screened for antibiotic susceptibility by disk diffusion; further genotypic characterization of β-lactamase-encoding genes was performed with Real-Time PCR. E. coli strains were phylotyped with the Clermont triplex PCR method.

Results

Of the total of 101 bacterial isolates recovered from retail sheep meat samples, 93 were E. coli, six were Enterobacter cloacae and two were Proteus mirabilis. As many as 17% of these 100 samples showed ESBL phenotypes, all were E. coli. The bla_CTX-M genes were detected in seven isolates (six were bla_CTX-M-15 and one was bla_CTX-M-14), three isolates harboured bla_TEM (all were bla_TEM-one), and two carried genes of the bla_SHV family (both were bla_SHV-12). Eight E. coli isolates expressed ESBL phenotype but no bla_TEM, bla_SHV or bla_CTX-M genes were detected by PCR. ESBL- positive E. coli isolates were nearly equally distributed over the commensal groups A/B1 and the virulent group D.

Conclusion

Nearly one in five sheep meat samples was contaminated with ESBL-E. coli. This further corroborates the potential role played by contaminated meat in the increasing resistance rates that have been reported worldwide.

Virulence characterization and clonal analysis of uropathogenic Escherichia coli metallo-beta-lactamase-producing isolates

Background

Uropathogenic Escherichia coli (UPEC) is a major cause of urinary tract infection (UTI); however, treatment of UTI has been challenging due to increased antimicrobial resistance (AMR). One of the most important types of AMR is carbapenem resistance (CR). CR bacteria are known as an important threat to global public health today. Class B metallo-beta-lactamases (MBLs) are one of the major factors for resistance against carbapenems. We aimed to investigate the characteristics of UPEC isolates producing MBL.

Methods

A cross-sectional study was conducted from October 2018 to December 2019 in Ahvaz; Iran. UPEC isolates were identified by biochemical and molecular methods. Metallo-beta-lactamase-producing isolates were detected using modified carbapenem inactivation method (mCIM) and EDTA-CIM (eCIM) tests. MBL genes, phylogenetic group, and virulence genes profile of carbapenem resistant isolates were determined. Conjugation assay and plasmid profiling were conducted to evaluate the ability of transferring of CR to other E. coli isolates. Clonal similarity of isolates were assessed using Enterobacterial intergenic repetitive element sequence (ERIC)-PCR.

Results

Among 406 UPEC isolates, 12 (2.95%) carbapenem-resistant were detected of which 11 were phenotypically MBL-producing strains. Four isolates were resistant to all investigated antimicrobial agents and were considered possible pandrug-resistant (PDR). bla_NDM, bla_OXA-48, bla_IMP-1, and bla_IMP-2 genes were found in 9, 5, 1, and 1 isolates, respectively. Among 30 virulence genes investigated, the traT, fyuA followed by fimH, and iutA with the frequency of 8 (66.7%), 8 (66.7%), 7 (58.3%), and 7 (58.3%) were the most identified genes, respectively. Siderophore production was the main virulence trait among carbapenem-resistant UPEC isolates. Except for two, all other isolates showed weak to moderate virulence index. In all recovered isolates, CR was readily transmitted via plasmids to other isolates during conjugation experiments.

Conclusion

MBL and carbapenemase genes, especially bla_NDM and bla_OXA-48 are spreading rapidly among bacteria, which can be a threat to global public health. Therefore monitoring the emergence and dissemination of new AMR is necessary to continuously refine guidelines for empiric antimicrobial therapy. Understanding the mechanisms of resistance and virulence in this group of bacteria can play an effective role in providing new therapeutic methods.

Microbiota-Derived Short-Chain Fatty Acids Promote LAMTOR2-Mediated Immune Responses in Macrophages

ABSRTACTKlebsiella pneumoniae is a common cause of human-pneumonia-derived sepsis with high morbidity and mortality. The microbiota promotes and maintains host immune homeostasis. The mechanisms by which the gut microbiota affects the host defenses in the respiratory system systematically, however, remain poorly understood. Here, we show that gut microbiota depletion increases susceptibility to extracellular K. pneumoniae infections in terms of increased bacterial burdens in lung and decreased survival rates. Oral supplementation with gut microbiota-derived short-chain fatty acids (SCFAs), subsequently activating G protein-coupled receptor 43 (GPCR43), enhances a macrophage's capacity to phagocytose invading K. pneumoniae Furthermore, SCFAs and GPR43 increase macrophage bacterial clearance by upregulating LAMTOR2, which is further identified as an antibacterial effector and elucidated to facilitate phagosome-lysosome fusion and extracellular signal-regulated kinase (ERK) phosphorylation. Lastly, conditional ablation of Lamtor2 in macrophages decreases their antimicrobial activity, even though mice were pretreated with exogenous SCFA supplementation.IMPORTANCE These observations highlight that SCFAs promote macrophage elimination of K. pneumoniae via a LAMTOR2-dependent signal pathway and suggest that it is possible to intervene in K. pneumoniae pneumonia by targeting the gut microbiota.

Alterations in the Gut Microbiome and Cecal Metabolome During Klebsiella pneumoniae-Induced Pneumosepsis

Klebsiella (K.) pneumoniae is a common cause of pneumonia-derived sepsis in human and is associated with high morbidity and mortality. The microbiota promotes and maintains host immune homeostasis during bacterial infections. However, the mechanisms by which the gut microbiota affects immune responses in the lung still remain poorly understood. Here, we performed cecal metabolomics sequencing and fecal 16s rRNA sequencing in K. pneumoniae-infected mice and uninfected controls and showed that K. pneumoniae infection led to profound alterations in the gut microbiome and thus the cecal metabolome. We observed that the levels of Lactobacillus reuteri and Bifidobacterium pseudolongum were significantly decreased in K. pneumoniae-infected mice. Spearman correlation analysis showed that alterations in the richness and composition of the gut microbiota were associated with profound changes in host metabolite concentrations. Further, short-chain fatty acids (SCFAs), including acetate, propionate, and butyrate, were detected in cecal contents and serum by gas chromatography-mass spectrometry (GC-MS). We observed that the concentrations of these three SCFAs were all lower in the infected groups than in the untreated controls. Lastly, oral supplementation with these three SCFAs reduced susceptibility to K. pneumoniae infections, as indicated by lower bacterial burdens in the lung and higher survival rates. Our data highlight the protective roles of gut microbiota and certain metabolites in K. pneumoniae-pneumonia and suggests that it is possible to intervene in this bacterial pneumonia by targeting the gut microbiota.

Bacteriocins, Antimicrobial Peptides from Bacterial Origin: Overview of Their Biology and Their Impact against Multidrug-Resistant Bacteria

Currently, the emergence and ongoing dissemination of antimicrobial resistance among bacteria are critical health and economic issue, leading to increased rates of morbidity and mortality related to bacterial infections. Research and development for new antimicrobial agents is currently needed to overcome this problem. Among the different approaches studied, bacteriocins seem to be a promising possibility. These molecules are peptides naturally synthesized by ribosomes, produced by both Gram-positive bacteria (GPB) and Gram-negative bacteria (GNB), which will allow these bacteriocin producers to survive in highly competitive polymicrobial environment. Bacteriocins exhibit antimicrobial activity with variable spectrum depending on the peptide, which may target several bacteria. Already used in some areas such as agro-food, bacteriocins may be considered as interesting candidates for further development as antimicrobial agents used in health contexts, particularly considering the issue of antimicrobial resistance. The aim of this review is to present an updated global report on the biology of bacteriocins produced by GPB and GNB, as well as their antibacterial activity against relevant bacterial pathogens, and especially against multidrug-resistant bacteria.

The Phylogenetic Relatedness of bla NDM-1 Harboring Extended-Spectrum β-Lactamase Producing Uropathogenic Escherichia coli and Klebsiella pneumoniae in the North of Iran

Background

Escherichia coli and Klebsiella pneumoniae as an important part of Enterobacterales family are important causes of both community- and hospital-acquired infections. The present study aimed to investigate the prevalence of antibiotics resistance and molecular characteristics of uropathogenic isolates of E. coli and K. pneumoniae in Iranian patients.

Methods

This cross-sectional study performed on 223 Escherichia coli and 68 Klebsiella pneumoniae isolates obtained from hospitalized patients in the north of Iran. The isolates were identified by standard microbiologic tests and confirmed by API 20E strip. Disk diffusion method was applied to determine antibiotic susceptibility pattern. The presence of β-lactamases encoding genes was evaluated by PCR method. Analysis of the mutations and homology among sequences was done by the CLC sequence viewer (Qiagen, Denmark), and phylogenetic trees were constructed by the neighbor-joining method (Bootstrap: 1000 times).

Results

The overall rates of extended-spectrum β-lactamases (ESBLs)-producing E. coli and K. pneumoniae isolates were 37.7% and 32.4%, respectively. The overall presence of bla_SHV, bla_NDM-1, and bla_OXA-1 genes was detected in 16 (5.5%), 12 (4.1%), and 48 (16.4%) of isolates, respectively. The neighbor-joining analysis for E. coli KU985246.1 strain showed that the most related bla_NDM-1 sequences were from China, Singapore, UK, Thailand, and Bangladesh. While K. pneumoniae KU985245.1 strains were mostly related to bla_NDM-1 sequences form Myanmar, and China.

Conclusion

In summary, the remarkable rate of ESBL-producing uropathogenic Enterobacterales along with the first prevalence of NDM-1 β-lactamases can be a serious concern in our region.

Modulation of antimicrobial resistance in clinical isolates of Enterobacter aerogenes: A strategy combining antibiotics and chemosensitisers

OBJECTIVE

The main focus of this study was to evaluate the antimicrobial susceptibility profiles of a number of human clinical isolates of Enterobacter aerogenes isolates and to explore the effects of selected chemosensitisers on reversal of the resistant phenotype of these isolates.

METHODS

This study design was accomplished by: (i) characterising several multidrug-resistant (MDR) E. aerogenes clinical isolates; (ii) evaluating the contribution of target gene mutations to the resistance phenotype, focusing on fluoroquinolones and chloramphenicol only; (iii) evaluating the contribution of membrane permeability and efflux to the MDR phenotype; (iv) assessing the combined action of selected antimicrobials and chemosensitisers in order to identify combinations with synergistic effects able to reduce the minimum inhibitory concentration (MIC); and (v) understanding how these combinations can modulate the permeability or efflux of these isolates.

RESULTS

Resistance to ciprofloxacin could not be totally reversed owing to pre-existing mutations in target genes. Chloramphenicol susceptibility was efficiently restored by the addition of the selected chemosensitisers. From the modulation kinetics it was clear that phenothiazines were able to increase the accumulation of Hoechst dye.

CONCLUSIONS

Modulation of permeability and efflux in the presence of chemosensitisers can help us to propose more appropriate chemotherapeutic combinations that can set the model to be used in the treatment of these and other MDR infections.

Antimicrobial resistance in Enterobacteriaceae from healthy broilers in Egypt: emergence of colistin-resistant and extended-spectrum β-lactamase-producing Escherichia coli

Background

Poultry remains one of the most important reservoir for zoonotic multidrug resistant pathogens. The global rise of antimicrobial resistance in Gram-negative bacteria is of reasonable concern and demands intensified surveillance.

Methods

In 2016, 576 cloacal swabs were collected from 48 broiler farms located in five governorates in northern Egypt. Isolates of Enterobacteriaceae could be cultivated on different media and were identified by MALDI-TOF MS and PCR. Escherichia coli isolates were genotyped by DNA-microarray-based assays. The antimicrobial susceptibility to 14 antibiotics was determined and resistance-associated genes were detected. The VITEK-2 system was applied for phenotypical confirmation of extended-spectrum β-lactamase-producing isolates. The determination of colistin resistance was carried out phenotypically using E-test and genotypically using PCR for detection of the mcr-1 gene.

Results

Out of 576 samples, 72 representatives of Enterobacteriaceae were isolated and identified as 63 E. coli (87.5%), 5 Enterobacter cloacae (6.9%), 2 Klebsiella pneumoniae (2.8%) and 2 Citrobacter spp. (2.8%). Seven out of 56 cultivated E. coli (12.5%) were confirmed as ESBL-producing E. coli and one isolate (1.8%) as ESBL/carbapenemase-producing E. coli. Five out of 63 E. coli isolates (7.9%) recovered from different poultry flocks were phenotypically resistant to colistin and harboured mcr-1 gene.

Conclusions

This is the first study reporting colistin resistance and emergence of multidrug resistance in Enterobacteriaceae isolated from healthy broilers in the Nile Delta region, Egypt. Colistin-resistant E. coli in poultry is of public health significance. The global rise of ESBL- and carbapenemase-producing Gram-negative bacteria demands intensified surveillance. ESBL-producing E. coli in poultry farms in Egypt are of major concern that emphasizes the possibility of spread of such strains to humans. The results also reinforce the need to develop strategies and to implement specific control procedures to reduce the use of antibiotics.

Molecular characterization of extended spectrum β -lactamases enterobacteriaceae causing lower urinary tract infection among pediatric population

Background

The β-lactam antibiotics have traditionally been the main treatment of Enterobacteriaceae infections, nonetheless, the emergence of species producing β- Lactamases has rendered this class of antibiotics largely ineffective. There are no published data on etiology of urinary tract infections (UTI) and antimicrobial resistance profile of uropathogens among children in Qatar. The aim of this study is to determine the phenotypic and genotypic profiles of antimicrobial resistant Enterobacteriaceae among children with UTI in Qatar.

Methods

Bacteria were isolated from 727 urine positive cultures, collected from children with UTI between February and June 2017 at the Pediatric Emergency Center, Doha, Qatar. Isolated bacteria were tested for antibiotic susceptibility against sixteen clinically relevant antibiotics using phoenix and Double Disc Synergy Test (DDST) for confirmation of extended-spectrum beta-lactamase (ESBL) production. Existence of genes encoding ESBL production were identified using polymerase chain reaction (PCR). Statistical analysis was done using non-parametric Kappa statistics, Pearson chi-square test and Jacquard's coefficient.

Results

201 (31.7%) of samples were confirmed as Extended Spectrum β -Lactamases (ESBL) Producing Enterobacteriaceae. The most dominant pathogen was E. coli 166 (83%) followed by K. pneumoniae 22 (11%). Resistance was mostly encoded by ^bla CTX-M (59%) genes, primarily ^bla CTX-MG1 (89.2%) followed by ^bla CTX-MG9 (7.7%). 37% of isolated bacteria were harboring multiple ^bla genes (2 genes or more). E. coli isolates were categorized into 11 clusters, while K. pneoumoniae were grouped into five clonal clusters according to the presence and absence of seven genes namely ^bla TEM, ^bla SHV, ^bla CTX-MG1, ^bla CTX-MG2, ^bla CTX-MG8 ^bla CTX-MG9,^bla CTX-MG25.

Conclusions

Our data indicates an escalated problem of ESBL in pediatrics with UTI, which mandates implementation of regulatory programs to reduce the spread of ESBL producing Enterobacteriaceae in the community. The use of cephalosporins, aminoglycosides (gentamicin) and trimethoprim/sulfamethoxazole is compromised in Qatar among pediatric population with UTI, leaving carbapenems and amikacin as the therapeutic option for severe infections caused by ESBL producers.

Identification of Ideal Multi-targeting Bioactive Compounds Against Mur Ligases of Enterobacter aerogenes and Its Binding Mechanism in Comparison with Chemical Inhibitors

Enterobacter aerogenes have been reported as important opportunistic and multi-resistant bacterial pathogens for humans during the last three decades in hospital wards. The emergence of drug-resistant E. aerogenes demands the need for developing new drugs. Peptidoglycan is an important component of the cell wall of bacteria and the peptidoglycan biochemical pathway is considered as the best source of antibacterial targets. Within this pathway, four Mur ligases MurC, MurD, MurE, and MurF are responsible for the successive additions of L-alanine and suitable targets for developing novel antibacterial drugs. As an inference from this fact, we modeled the three-dimensional structure of above Mur ligases using best template structures available in PDB and analyzed its common binding features. Structural refinement and energy minimization of the predicted Mur ligases models is also being done using molecular dynamics studies. The models of Mur ligases were further investigated for in silico docking studies using bioactive plant compounds from the literature. Interestingly, these results indicate that four plant compounds Isojuripidine, Atroviolacegenin, Porrigenin B, and Nummularogenin showing better docking results in terms of binding energy and number of hydrogen bonds. All these four compounds are spirostan-based compounds with differences in side chains and the amino acid such as ASN, LYS, THR, HIS, ARG (polar) and PHE, GLY, VAL, ALA, MET (non-polar) playing active role in binding site of all four Mur ligases. Overall, in the predicted model, the four plant compounds with its binding features could pave way to design novel multi-targeted antibacterial plant-based bioactive compounds specific to Mur ligases for the treatment of Enterobacter infections.

EXTENDED-SPECTRUM BETA-LACTAMASE PRODUCING GRAM NEGATIVE BACTERIA IN IRAN: A REVIEW

Background:

The emergence and spread of extended spectrum β-lactamase (ESBL)-producing Gram- negative bacteria (GNB), particularly in Enterobacteriaceae, Acinetobacter baumannii, and Pseudomonas aeruginosa, have increased all over the world. ESBLs are characterized by their ability to hydrolyze β-lactams, early cephalosporins, oxyimino-thiazolyl cephalosporins, and monobactams, but not cephamycins or carbapenems. The rate of nosocomial infections caused by ESBL-producing GNB in Asia Pacific has increased and several studies have identified their prevalence in the region. The aim of this study is to review the prevalence of ESBL-producing GNB in the West Asia and the Middle East with a particular focus on Iran.

Materials and Methods:

The available evidence from various studies (Microbia and clinical studies, retrieved from the PubMed, and Scopus databases) regarding the ESBL producing Gram negative bacteria in Iran were evaluated.

Results:

In almost all parts of the country, high resistance has been observed, especially in the central part of Iran. Up to 89.8% Escherichia coli, 72.1% Klebsiella pneumonia, 84.2% Acinetobacter baumannii, and 83.8% Pseudomonas aeruginosa isolates are ESBL positive.

Conclusion:

The present study showed the increasing prevalence of ESBLs in different regions of Iran, which could be useful to strategic policy towards reducing reduce their prevalence.

Surveillance of Extended-Spectrum Beta-Lactamase-Producing Escherichia coli in Dairy Cattle Farms in the Nile Delta, Egypt

Introduction: Industrial livestock farming is a possible source of multi-resistant Gram-negative bacteria, including producers of extended spectrum beta-lactamases (ESBLs) conferring resistance to 3rd generation cephalosporins. Limited information is currently available on the situation of ESBL producers in livestock farming outside of Western Europe. A surveillance study was conducted from January to May in 2014 in four dairy cattle farms in different areas of the Nile delta, Egypt.

Materials and Methods: In total, 266 samples were collected from 4 dairy farms including rectal swabs from clinically healthy cattle (n = 210), and environmental samples from the stalls (n = 56). After 24 h pre-enrichment in buffered peptone water, all samples were screened for 3rd generation cephalosporin-resistant Escherichia coli using Brilliance™ ESBL agar. Suspected colonies of putatively ESBL-producing E. coli were sub-cultured and subsequently genotypically and phenotypically characterized. Susceptibility testing using the VITEK-2 system was performed. All suspect isolates were genotypically analyzed using two DNA-microarray based assays: CarbDetect AS-1 and E. coli PanType AS-2 kit (ALERE). These tests allow detection of a multitude of genes and their alleles associated with resistance toward carbapenems, cephalosporins, and other frequently used antibiotics. Serotypes were determined using the E. coli SeroGenotyping AS-1 kit (ALERE).

Results: Out of 266 samples tested, 114 (42.8%) ESBL-producing E. coli were geno- and phenotypically identified. 113 of 114 phenotypically 3rd generation cephalosporin-resistant isolates harbored at least one of the ESBL resistance genes covered by the applied assays [blaCTX-M15 (n = 105), blaCTX-M9 (n = 1), blaTEM (n = 90), blaSHV (n = 1)]. Alarmingly, the carbapenemase genes blaOXA-48 (n = 5) and blaOXA-181 (n = 1) were found in isolates that also were phenotypically resistant to imipenem and meropenem. Using the array-based serogenotyping method, 66 of the 118 isolates (55%) could be genotypically assigned to O-types.

Conclusion: This study is considered to be a first report of the high prevalence of ESBL-producing E. coli in dairy farms in Egypt. ESBL-producing E. coli isolates with different underlying resistance mechanisms are common in investigated dairy cattle farms in Egypt. The global rise of ESBL- and carbapenemase-producing Gram-negative bacteria is a big concern, and demands intensified surveillance.

Granzymes A and B Regulate the Local Inflammatory Response during Klebsiella pneumoniae Pneumonia

Klebsiella pneumoniae is a common cause of hospital-acquired pneumonia. Granzymes (gzms), mainly found in cytotoxic lymphocytes, have been implicated as mediators of infection and inflammation. We here sought to investigate the role of gzmA and gzmB in the host response to K. pneumoniae-induced airway infection and sepsis. For this purpose, pneumonia was induced in wild-type (WT) and gzmA-deficient (gzmA-/-), gzmB-/- and gzmAxB-/- mice by intranasal infection with K. pneumoniae. In WT mice, gzmA and gzmB were mainly expressed by natural killer cells. Pneumonia was associated with reduced intracellular gzmA and increased intracellular gzmB levels. Gzm deficiency had little impact on antibacterial defence: gzmA-/- and gzmAxB-/- mice transiently showed modestly higher bacterial loads in the lungs but not in distant organs. GzmB-/- and, to a larger extent, gzmAxB-/- mice displayed transiently increased lung inflammation, reflected in the semi-quantitative histology scores and levels of pro-inflammatory cytokines and chemokines. Most differences between gzm-deficient and WT mice had disappeared during late-stage pneumonia. Gzm deficiency did not impact on distant organ injury or survival. These results suggest that gzmA and gzmB partly regulate local inflammation during early pneumonia but eventually play an insignificant role during pneumosepsis by the common human pathogen K. pneumoniae.

Receptor for Advanced Glycation End Products (RAGE) Serves a Protective Role during Klebsiella pneumoniae - Induced Pneumonia

Klebsiella species is the second most commonly isolated gram-negative organism in sepsis and a frequent causative pathogen in pneumonia. The receptor for advanced glycation end products (RAGE) is expressed on different cell types and plays a key role in diverse inflammatory responses. We here aimed to investigate the role of RAGE in the host response to Klebsiella (K.) pneumoniae pneumonia and intransally inoculated rage gene deficient (RAGE^-/-) and normal wild-type (Wt) mice with K. pneumoniae. Klebsiella pneumonia resulted in an increased pulmonary expression of RAGE. Furthermore, the high-affinity RAGE ligand high mobility group box-1 was upregulated during K. pneumoniae pneumonia. RAGE deficiency impaired host defense as reflected by a worsened survival, increased bacterial outgrowth and dissemination in RAGE^-/- mice. RAGE^-/- neutrophils showed a diminished phagocytosing capacity of live K. pneumoniae in vitro. Relative to Wt mice, RAGE^-/- mice demonstrated similar lung inflammation, and slightly elevated—if any—cytokine and chemokine levels and unchanged hepatocellular injury. In addition, RAGE^-/- mice displayed an unaltered response to intranasally instilled Klebsiella lipopolysaccharide (LPS) with respect to pulmonary cell recruitment and local release of cytokines and chemokines. These data suggest that (endogenous) RAGE protects against K. pneumoniae pneumonia. Also, they demonstrate that RAGE contributes to an effective antibacterial defense during K. pneumoniae pneumonia, at least partly via its participation in the phagocytic properties of professional granulocytes. Additionally, our results indicate that RAGE is not essential for the induction of a local and systemic inflammatory response to either intact Klebsiella or Klebsiella LPS.

A qPCR and multiplex pyrosequencing assay combined with automated data processing for rapid and unambiguous detection of ESBL-producers Enterobacteriaceae

Rapid and specific detection of extended-spectrum β-lactamase-producing (ESBL) bacteria is crucial both for timely antibiotic therapy when treating infected patients as well as for appropriate infection control measures aimed at curbing the spread of ESBL-producing isolates. Whereas a variety of phenotypic methods are currently available for ESBL detection, they remain time consuming and sometimes difficult to interpret while being also affected by a lack of sensitivity and specificity. Considering the longer turnaround time (TAT) of susceptibility testing and culture results, DNA-based ESBL identification would be a valuable surrogate for phenotypic-based methods. Putative ESBL-positive Enterobacteriaceae isolates (n = 330) from clinical specimen were prospectively collected in Bulgaria, Romania and Democratic Republic of Congo and tested in this study. All isolates were assessed for ESBL-production by the E-test method and those giving undetermined ESBL status were re-tested using the combination disk test. A genotypic assay successively combining qPCR detection of blaCTX-M, blaTEM and blaSHV genes with a multiplex pyrosequencing of blaTEM and blaSHV genes was developed in order to detect the most common ESBL-associated TEM and SHV single nucleotides polymorphisms, irrespective of their plasmid and/or chromosomal location. This assay was applied on all Enterobacteriaceae isolates (n = 330). Phenotypic and genotypic results matched in 324/330 (98.2%). Accordingly, real-time PCR combined with multiplex pyrosequencing appears to be a reliable and easy-to-perform assay with high-throughput identification and fast TAT (~5 h).

Resistance to extended-spectrum β-lactamases in Salmonella from a broiler supply Chain

The prevalence of extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae varies worldwide, however, the incidence of ESBL-producing environmental Salmonella isolates is increasing. Salmonella is still one of the most important pathogens that occur in the poultry supply chain. Therefore, this study analyzed the susceptibility of Salmonella isolates collected from a poultry supply chain to β-lactam antibiotics, and examined the phenotypes of the isolates based on enzyme-inducible AmpC β-lactamase analysis. All analysis of the putative positive isolates in the current study confirmed that 27.02% (77/285 analysis) of all ESBL tests realized with the isolates produced a profile of resistance consistent with β-lactamase production. All isolates of S. Minnesota serotype had ESBL phenotype. Aztreonam resistance was the least common amongst the Salmonella isolates, followed by ceftazidime. The presence of inducible chromosomal ESBL was detected in 14 different isolates of the 19 serotypes investigated. These results are very indicatives of the presence of ESBL genes in Salmonella isolates from a broiler supply chain, reaffirming the growing global problem of ESBL resistance.

Hematopoietic but not endothelial cell MyD88 contributes to host defense during gram-negative pneumonia derived sepsis

Klebsiella pneumoniae is an important cause of sepsis. The common Toll-like receptor adapter myeloid differentiation primary response gene (MyD)88 is crucial for host defense against Klebsiella. Here we investigated the role of MyD88 in myeloid and endothelial cells during Klebsiella pneumosepsis. Mice deficient for MyD88 in myeloid (LysM-Myd88(-/-)) and myeloid plus endothelial (Tie2-Myd88(-/-)) cells showed enhanced lethality and bacterial growth. Tie2-Myd88(-/-) mice reconstituted with control bone marrow, representing mice with a selective MyD88 deficiency in endothelial cells, showed an unremarkable antibacterial defense. Myeloid or endothelial cell MyD88 deficiency did not impact on lung pathology or distant organ injury during late stage sepsis, while LysM-Myd88(-/-) mice demonstrated a strongly attenuated inflammatory response in the airways early after infection. These data suggest that myeloid but not endothelial MyD88 is important for host defense during gram-negative pneumonia derived sepsis.

Effect of ceftriaxone on the outcome of murine pyelonephritis caused by extended-spectrum-β-lactamase-producing Escherichia coli

Urinary tract infections (UTIs) due to extended-spectrum-β-lactamase (ESBL)-producing Enterobacteriaceae in children are becoming more frequent, and they are commonly treated initially with a second- or third-generation cephalosporin. We developed a murine model of ascending UTI caused by ESBL-producing Escherichia coli. Using this model, we investigated the renal bacterial burden, interleukin-6 (IL-6) expression, and histopathological alterations caused by ESBL- and non-ESBL-producing bacteria after 1, 2, or 6 days with or without ceftriaxone therapy. The renal bacterial burden, IL-6 concentration, and histological inflammatory lesions were not significantly different between mice infected with ESBL- and non-ESBL-producing bacteria without treatment at any of the time points examined. Following ceftriaxone administration, the bacterial burden was eliminated in the kidneys of mice infected with ESBL- and non-ESBL-producing bacteria on the 6th postinfection day. The histological analysis demonstrated that among mice treated with ceftriaxone, those infected with ESBL-producing bacteria had more profound renal alterations than those infected with non-ESBL-producing bacteria on the 6th day (P < 0.001). In comparison, microbiological outcomes did not differ significantly between mice infected with ESBL- and non-ESBL-producing bacteria at any of the time points examined. The effectiveness of ceftriaxone in mice with UTIs due to ESBL-producing E. coli may have therapeutic implications; it is, however, hampered by limited activity on the histopathological lesions, a finding that needs further investigation.

Treatment options for multidrug-resistant bacteria

As a consequence of antibiotic overuse and misuse, nosocomial infections caused by multidrug-resistant bacteria represent a physician's nightmare throughout the world. No newer antimicrobials active against Pseudomonas aeruginosa, the main multidrug-resistant nosocomial pathogen, are available or under investigation. The only exceptions are linezolid, some newer glycopeptides (dalbavancin, oritavancin and telavancin) and daptomycin (a lipopeptide), which are active against methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE) strains, as well as tigecycline, a potent in vitro glycylcycline against MRSA, VRE, Acinetobacter baumannii and entended-spectrum beta-lactamase (ESBL)+ Enterobacteriaceae. Colistin, an antibiotic of the 1950s has been rediscovered by intensive care unit physicians for use against ESBL+ Enterobacteriaceae, as well as against multidrug-resistant P. aeruginosa and A. baumannii isolates. Although success rates with colistin range between 50 and 73%, almost all studies are retrospective. Immunostimulation efforts against S. aureus are still under development. As antibiotic research and development stagnate, rational policies for prescribing existing antibiotics plus strict infection control are the current mainstay efforts for preventing and combating multidrug-resistant bacterial infections.

Long-term dissemination of acquired AmpC β-lactamases among Klebsiella spp. and Escherichia coli in Portuguese clinical settings

We investigated the occurrence, diversity and molecular epidemiology of genes coding for acquired AmpC β-lactamases (qAmpC) among clinical isolates of Enterobacteriaceae lacking inducible chromosomal AmpCs in Portugal. A total of 675 isolates non-susceptible to broad-spectrum cephalosporins obtained from four hospitals and three community laboratories during a 7-year period (2002-2008) were analysed. The presence of genes coding for qAmpC was investigated by phenotypic criteria, polymerase chain reaction (PCR) and sequencing. Bacterial identification, antibiotic susceptibility testing, conjugation assays and clonal analysis were performed by standard procedures. The presence of bla(qAmpC) genes was detected in 50 % (50/100; 41 Klebsiella pneumoniae, 5 Escherichia coli, 4 Klebsiella oxytoca) of the presumptive qAmpC producers. DHA-1, detected in those species, was the most prevalent qAmpC (94 %, 47/50), being identified since 2003 and throughout the studied period in different institutions. Despite the high clonal diversity observed, three DHA-1-producing Klebsiella spp. clones were more frequently identified. CMY-2 (6 %, 3/50) was observed in B1-E. coli clones. Conjugative transfer was only observed in one (2 %) CMY-2-producing isolate. Most qAmpC producers (94 %, 47/50) co-expressed SHV-type and/or OXA-1 or CTX-M-32 extended-spectrum β-lactamases (ESBLs). To the authors' knowledge, this is the first description of the molecular epidemiology and the long-term dissemination of qAmpC-producing Enterobacteriaceae in Portuguese clinical settings, highlighting an evolution towards a more complex epidemiological situation regarding cephalosporin resistance in Portugal.

High burden of extended-spectrum β-lactamase-producing Enterobacteriaceae in Gabon

OBJECTIVES

Extended-spectrum β-lactamase-producing Enterobacteriaceae (ESBL-E) are sporadically reported from infections in sub-Saharan Africa. Travellers returning from the tropics have a high risk of ESBL-E colonization, which suggests a high prevalence of ESBL-E in Africa. Our objective was to assess the burden of rectal ESBL-E colonization and associated risk factors in Gabon, Central Africa

PATIENTS AND METHODS

We performed a cross-sectional study on 200 hospitalized children in Gabon, Central Africa, on rectal ESBL-E colonization and applied a standardized questionnaire to assess risk factors. The antimicrobial resistance and the type of β-lactamase (SHV, TEM and CTX-M) were analysed for each isolate. Isolates associated with nosocomial spread were further genotyped.

RESULTS

The overall colonization rate of ESBL-E was 45% (n = 90) and increased from 33.6% (n = 37) at admission to 94.1% (n = 16) during hospitalization. Risk factors for ESBL-E carriage were age <5 years, hospitalization for ≥5 days and a hospital stay during the past year. All isolates were susceptible to meropenem, but non-susceptible to ciprofloxacin in 52.8% (n = 57). CTX-M-15 was the predominant β-lactamase. Genotyping revealed a polyclonal structure of nosocomial isolates.

CONCLUSIONS

ESBL colonization in hospitalized children in Gabon is high. The risk of nosocomial transmission of ESBL-E is a challenge in rural Africa and underlines the need for sentinel surveillance in the absence of a broad decentralized microbiology laboratory.

Myeloid-related protein-14 contributes to protective immunity in gram-negative pneumonia derived sepsis

Klebsiella (K.) pneumoniae is a common cause of pneumonia-derived sepsis. Myeloid related protein 8 (MRP8, S100A8) and MRP14 (S100A9) are the most abundant cytoplasmic proteins in neutrophils. They can form MRP8/14 heterodimers that are released upon cell stress stimuli. MRP8/14 reportedly exerts antimicrobial activity, but in acute fulminant sepsis models MRP8/14 has been found to contribute to organ damage and death. We here determined the role of MRP8/14 in K. pneumoniae sepsis originating from the lungs, using an established model characterized by gradual growth of bacteria with subsequent dissemination. Infection resulted in gradually increasing MRP8/14 levels in lungs and plasma. Mrp14 deficient (mrp14^−/−) mice, unable to form MRP8/14 heterodimers, showed enhanced bacterial dissemination accompanied by increased organ damage and a reduced survival. Mrp14^−/− macrophages were reduced in their capacity to phagocytose Klebsiella. In addition, recombinant MRP8/14 heterodimers, but not MRP8 or MRP14 alone, prevented growth of Klebsiella in vitro through chelation of divalent cations. Neutrophil extracellular traps (NETs) prepared from wildtype but not from mrp14^−/− neutrophils inhibited Klebsiella growth; in accordance, the capacity of human NETs to kill Klebsiella was strongly impaired by an anti-MRP14 antibody or the addition of zinc. These results identify MRP8/14 as key player in protective innate immunity during Klebsiella pneumonia.

Neutrophils are phagocytes that are well known for their capacity to engulf and kill microbial pathogens. It has become increasingly clear that neutrophils also kill or inhibit growth extracellularly by releasing neutrophil extracellular traps (NETs), chromatin fibers decorated with neutrophil derived proteins. MRP8/14 has been identified as one of the major antimicrobial proteins herein. Previous investigations have shown that endogenously released MRP8/14 is also sensed by the host as a danger signal and able to potentiate the harmful systemic inflammatory response syndrome. Indeed, in the setting of fulminant systemic inflammation, such as induced by endotoxin or Escherichia coli administration, MRP8/14 contributed to organ injury and mortality. The clinical scenario of sepsis however, involves an initial infection at the primary site followed by bacterial spreading to other organs. In the present setting of pneumonia-derived sepsis using the common human respiratory and sepsis pathogen Klebsiella pneumoniae MRP8/14 clearly served a beneficial role in antimicrobial defense. We here provide a likely mechanism by showing that MRP8/14 plays a role in phagocytosis and that its presence is critical in both murine and human NETs to inhibit bacterial growth.

Differential roles of MyD88 and TRIF in hematopoietic and resident cells during murine gram-negative pneumonia

BACKGROUND

Pneumonia is frequently caused by gram-negative pathogens, among which Klebsiella pneumoniae prominently features. Recognition of pathogen-associated molecular patterns by Toll-like receptors (TLRs) is important for an appropriate immune response during infection. TLR signaling can proceed via 2 distinct routes that are dependent on the adaptor proteins Myeloid differentiation primary response gene (88) (MyD88) and TIR-domain-containing adaptor-inducing interferon-β (TRIF). The aim of the study was to determine the relative contribution of MyD88 and TRIF signaling in resident and hematopoietic cells to host defense during pneumonia.

METHODS

Bone marrow chimeras of MyD88 deficient/wild type and TRIF mutant/wild type mice were created and infected with K. pneumoniae via the airways.

RESULTS

MyD88 in both resident and hematopoietic cells contributed to survival and antibacterial defense in late-stage infection, whereas only TRIF in hematopoietic cells was protective. On the other hand, resident MyD88 and hematopoietic TRIF contributed to distant cellular injury. Resident MyD88 was pivotal for early chemokine release and neutrophil recruitment in the bronchoalveolar space.

CONCLUSIONS

MyD88- and TRIF-dependent signaling has a differential contribution to host defense in different cell types that changes from early- to late-stage gram-negative pneumonia.

Genetic methods for detection of antibiotic resistance: focus on extended-spectrum β-lactamases

BACKGROUND

In 1928, the first antibiotic, penicillin, was discovered. That was the beginning of a great era in the development and prescription of antibiotics. However, the introduction of these antimicrobial agents into clinical practice was accompanied by the problem of antibiotic resistance. Currently, bacterial resistance to antibiotics poses a major problem in both hospital and community settings throughout the world.

METHODS AND RESULTS

This review provides examples of modern genetic methods and their practical application in the field of extended-spectrum β-lactamase detection. Since extended-spectrum β-lactamases are the main mechanism of Gram-negative bacterial resistance to oxyimino-cephalosporins, rapid and accurate detection is requested in common clinical practice.

CONCLUSIONS

Currently, the detection of extended-spectrum β-lactamases is primarily based on the determination of bacterial phenotypes rather than genotypes. This is because therapeutic decisions are based on assessing the susceptibility rather than presence of resistance genes. One of the main disadvantages of genetic methods is high costs, including those of laboratory equipment. On the other hand, if these modern methods are introduced into diagnostics, they often help in rapid and accurate detection of certain microorganisms or their resistance and pathogenic determinants.

High-throughput microarray technology in diagnostics of enterobacteria based on genome-wide probe selection and regression analysis

Background

The Enterobacteriaceae comprise a large number of clinically relevant species with several individual subspecies. Overlapping virulence-associated gene pools and the high overall genome plasticity often interferes with correct enterobacterial strain typing and risk assessment. Array technology offers a fast, reproducible and standardisable means for bacterial typing and thus provides many advantages for bacterial diagnostics, risk assessment and surveillance. The development of highly discriminative broad-range microbial diagnostic microarrays remains a challenge, because of marked genome plasticity of many bacterial pathogens.

Results

We developed a DNA microarray for strain typing and detection of major antimicrobial resistance genes of clinically relevant enterobacteria. For this purpose, we applied a global genome-wide probe selection strategy on 32 available complete enterobacterial genomes combined with a regression model for pathogen classification. The discriminative power of the probe set was further tested in silico on 15 additional complete enterobacterial genome sequences. DNA microarrays based on the selected probes were used to type 92 clinical enterobacterial isolates. Phenotypic tests confirmed the array-based typing results and corroborate that the selected probes allowed correct typing and prediction of major antibiotic resistances of clinically relevant Enterobacteriaceae, including the subspecies level, e.g. the reliable distinction of different E. coli pathotypes.

Conclusions

Our results demonstrate that the global probe selection approach based on longest common factor statistics as well as the design of a DNA microarray with a restricted set of discriminative probes enables robust discrimination of different enterobacterial variants and represents a proof of concept that can be adopted for diagnostics of a wide range of microbial pathogens. Our approach circumvents misclassifications arising from the application of virulence markers, which are highly affected by horizontal gene transfer. Moreover, a broad range of pathogens have been covered by an efficient probe set size enabling the design of high-throughput diagnostics.

Physiological characterisation of the efflux pump system of antibiotic-susceptible and multidrug-resistant Enterobacter aerogenes

Enterobacter aerogenes predominates amongst Enterobacteriaceae species that are increasingly reported as producers of extended-spectrum beta-lactamases. Although this mechanism of resistance to beta-lactams is important, other mechanisms bestowing a multidrug-resistant (MDR) phenotype in this species are now well documented. Amongst these mechanisms is the overexpression of efflux pumps that extrude structurally unrelated antibiotics prior to their reaching their targets. Interestingly, although knowledge of the genetic background behind efflux pumps is rapidly advancing, few studies assess the physiological nature of the overall efflux pump system of this, or for that matter any other, bacterium. The study reported here evaluates physiologically the efflux pump system of an E. aerogenes ATCC reference as well as two strains whose MDR phenotypes are mediated by overexpressed efflux pumps. The activities of the efflux pumps in these strains are modulated by pH and glucose, although the effects of the latter are essentially restricted to pH 8, suggesting the presence of two general efflux pump systems, i.e. proton-motive force-dependent and ABC transporter types, respectively.

Extended-spectrum beta-lactamase-producing Enterobacter cloacae in mobile dialysis units in the medical and surgical departments of a university hospital: a case-control study

The objective of this case-control study was to investigate the source of contamination and risk factors for colonisation and infection during an outbreak of extended-spectrum beta-lactamase (ESBL)-producing Enterobacter cloacae in the University Medical Center Freiburg. A risk factor analysis was performed on 23 patients with ESBL-producing E. cloacae in the medical and surgical departments by comparing them with 46 non-colonised controls, who were matched for ward and length of hospital stay. For these, a risk factor analysis was conducted. Suspected sources for transmission of ESBL were examined and staff received training in infection control measures. The higher risk in colonised patients was attributed to dialysis with mobile units [odds ratio (OR): 4.00; 95% confidence interval (CI): 1.05-15.234; P=0.04]. Dialysis units were examined, but no contamination was found. Improvement in dialysis procedures, additional staff training and renewed training in standard precautions led to a substantial fall in case numbers. Risk factor analysis showed that colonised patients carried more invasive devices than controls (central venous catheter: OR: 2.50; 95% CI: 0.74-8.45; P=0.14; Foley catheter: 5.08; 0.61-42.23; P=0.13) and were given a greater number of different antibiotics (penicillins: 2.52; 0.71-8.89; P=0.15; fluoroquinolones: 2.37; 0.77-7.28; P=0.13). The differences in mobile dialysis frequency and antibiotic use between cases and controls were relevant, although the latter was not statistically significant. It was possible to contain the high frequency of ESBL colonisation or infection by reinforcing infection control measures and training the staff involved.

Ampicillin-sulbactam: an update on the use of parenteral and oral forms in bacterial infections

Ampicillin-sulbactam has a wide range of antibacterial activity that includes Gram-positive and Gram-negative aerobic and anaerobic bacteria. However, the drug is not active against Pseudomonas aeruginosa and pathogens producing extended-spectrum beta-lactamases. The combination could be considered particularly active against Acinetobacter baumannii infections due to the intrinsic activity of sulbactam. The drug is indicated as empirical therapy for a broad range of community acquired infections supervened in adults or children and is effective in either parenteral (ampicillin-sulbactam) or oral (as a mutual prodrug sultamicillin) form. In clinical trials, sultamicillin has proved clinically and bacteriologically effective in adults and children against a variety of frequently encountered infections, including mild upper and lower respiratory tract infections, urinary tract infections, diabetic foot and skin and soft tissue infections. Furthermore, adverse effects rarely occur with the diarrhoea to represent the most commonly reported. The parenteral ampicillin-sulbactam is indicated for community infections of mild-to-moderate severity acquired infections such as intra-abdominal or gynecological. Moreover, it seems to represent the alternative of choice for the treatment of A. baumannii infections for carbapenem-resistant strains in the nosocomial setting. Thus, ampicillin-sulbactam remains a valuable agent in the physician's armamentarium in the management of adult and pediatric infections.

Resistance against broad-spectrum beta-lactams among uropathogens in children

The aim of this study was to investigate the prevalence trends and risk factors for urinary tract infection (UTI) caused by Enterobacteriaceae resistant to broad-spectrum beta-lactams in children. All Enterobacteriaceae uropathogens from children <15 years during the 11-year period 1997-2007 were included, and risk factors were evaluated. Of 523 Enterobacteriaceae isolated from 473 children, 30 (5.73%) were phenotypically resistant to broad-spectrum beta-lactams (18 Escherichia coli, ten Klebsiella spp, one Enterobacter spp, and one Citrobacter spp). The prevalence of resistance increased during the study period (p = 0.031). Resistance to cefoxitin was common (26/30), pointing to AmpC enzyme expression, and 2/30 isolates were resistant to carbapenems. Resistant Enterobacteriaceae were often community acquired (22/30, 73.3%) and related to male gender (p < 0.05), urinary tract abnormalities (p < 0.05), prophylactic antibiotics (p < 0.0001), longer hospitalization (p < 0.001), and UTI recurrences (p < 0.001). Co-resistance was more likely for cotrimoxazole, gentamicin, and ciprofloxacin (p < 0.0001). In conclusion, our study points to increasing prevalence of Enterobacteriaceae uropathogens resistant to broad-spectrum beta-lactams in the community setting, which limits the utility of first-line antibiotics and questions the validity of using prophylaxis after a first UTI episode.

Impact of restriction of third generation cephalosporins on the burden of third generation cephalosporin resistant K. pneumoniae and E. coli in an ICU

OBJECTIVE

To test whether a reduction of third generation cephalosporin (3GC) use has a sustainable positive impact on the high endemic prevalence of 3GC resistant K. pneumoniae and E. coli.

DESIGN

Segmented regression analysis of interrupted time series was used to analyse antibiotic consumption and resistance data 30 months before and 30 after the intervention.

SETTING

Surgical intensive care unit (ICU) with 16-bed unit in a teaching hospital.

INTERVENTION

In July 2004, 3GCs were switched to piperacillin in combination with a beta-lactamase-inhibitor as standard therapy for peritonitis and other intraabdominal infections.

RESULTS

Segmented regression analysis showed that the intervention achieved a significant and sustainable decrease in the use of 3GCs of -110.2 daily defined doses (DDD)/1,000 pd. 3GC use decreased from a level of 178.9 DDD/1,000 pd before to 68.7 DDD/1,000 pd after the intervention. The intervention resulted in a mean estimated reduction in total antibiotic use of 27%. Piperacillin/tazobactam showed a significant increase in level of 64.4 DDD/1,000 pd, and continued to increase by 2.3 DDD/1,000 pd per month after the intervention. The intervention was not associated with a significant change in the resistance densities of 3GC resistant K. pneumoniae and E. coli.

CONCLUSION

Reducing 3GCs does not necessarily impact positively on the resistance situation in the ICU setting. Likewise, replacing piperacillin with beta-lactamase inhibitor might provide a selection pressure on 3GC resistant E. coli and K. pneumoniae. To improve resistance, it might not be sufficient to restrict interventions to a risk area.

Antimicrobial resistance in invasive strains of Escherichia coli from southern and eastern Mediterranean laboratories

From January 2003 to December 2005, 5091 susceptibility test results from invasive isolates of Escherichia coli, collected from blood cultures and cerebrospinal fluid routinely processed within 58 participating laboratories, were investigated. These laboratories in turn serviced 64 hospitals in Algeria, Cyprus, Egypt, Jordan, Lebanon, Malta, Morocco, Tunisia and Turkey. The median proportion of resistance to third-generation cephalosporins for the duration of the project was 18.9% (interquartile range (IQR): 12.5-30.8%), and for fluoroquinolones 21.0% (IQR: 7.7-32.6%). A substantial proportion of strains reported by laboratories in countries east of the Mediterranean exhibited evidence of multiresistance, the highest proportion being from Egypt (31%). There is clearly a need for further investigation of potential causes of the significant resistance identified, as well as for strengthening of national and international surveillance initiatives within this region.;

In vitro profiling of ceftaroline against a collection of recent bacterial clinical isolates from across the United States

This study evaluated the in vitro activity of ceftaroline, a novel cephalosporin with broad-spectrum activity against gram-negative and -positive pathogens, against 4,151 recent clinical isolates collected in the United States. Ceftaroline was very potent against bacteria found in community- and hospital-acquired infections, including methicillin-resistant Staphylococcus aureus, multidrug-resistant Streptococcus pneumoniae, and common Enterobacteriaceae spp.

Prevalence of extended-spectrum beta-lactamase-producing Escherichia coli in a tertiary care hospital in Tehran, Iran

The prevalence of extended-spectrum beta-lactamase (ESBL) production by consecutive, non-repeated Escherichia coli isolates from hospitalised patients was determined over the period from July 2005 to November 2006. A total of 201 E. coli were isolated from various clinical specimens, 135 (67.2%) of which were confirmed as ESBL-positive using the combination disk synergy test. By univariate analysis, male sex, intravascular or urinary catheterisation, recent surgery or hospitalisation and isolation of E. coli from wound or respiratory tube specimens were found to be risk factors for acquisition of resistant bacteria (chi(2) test, P<0.05). However, binary logistic multivariate regression analysis confirmed that isolation of E. coli from urine samples of either males in any hospital ward (odd ratio (OR) 7.52, 95% confidence interval (CI) 1.21-47.62; P=0.031) or patients with prior surgery (OR 13.16, 95% CI 1.81-100.00; P=0.011) were significantly associated with ESBL production. Imipenem, amikacin and piperacillin/tazobactam were found to be highly active against ESBL-positive isolates in vitro (100%, 91.1% and 85.2% susceptibility, respectively). They showed co-resistance with other antibiotics such as fluoroquinolones, gentamicin and trimethoprim/sulfamethoxazole. Of the 135 ESBL-positive isolates, 22 (16.3%) appeared to be of the CTX-M type based on a phenotypic determination method.

A comparative in vitro photoinactivation study of clinical isolates of multidrug-resistant pathogens

Photodynamic inactivation (PDI) has been investigated to cope with the increasing incidence of multidrug-resistant (MDR) pathogens. In Hong Kong, methicillin-resistant Staphylococcus aureus (MRSA) and extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli are the two commonest MDR pathogens. Here, we studied the photodynamic inactivation (PDI) mediated by poly-L-lysine chlorin(e6) conjugate (pL-ce6) and toluidine blue O (TBO) in clinical MRSA and ESBL producing E. coli, together with their corresponding American Type Culture Collection (ATCC) strains. Both pL-ce6 and TBO mediated a light- and drug dose-dependent efficacy for the four pathogens. pL-ce6 was more effective. pL-ce6 at 8 microM, 30 Jcm(-2), attained 5 log killing for ESBL-producing E. coli and E. coli (ATCC 25922); 4 log killing for MRSA, and 3 log killing for S. aureus (ATCC 25923). TBO at 80 microM, 30 Jcm(-2), only exhibited 3 log killing in MRSA and 2 log killing in S. aureus (ATCC 25923). TBO (400 microM, 30 Jcm(-2)) induced equal killing for ESBL-producing E. coli and E. coli (ATCC 25922). Our studied MRSA isolate responded better than S. aureus (ATCC 25923). Thus, pL-ce6-mediated PDI in other MRSA isolates deserves further investigation.

In vitro activity of tigecycline against multiple-drug-resistant, including pan-resistant, gram-negative and gram-positive clinical isolates from Greek hospitals

The in vitro activities of tigecycline and selected antimicrobials were evaluated against a variety of multiple-drug-resistant clinical isolates, including extended-spectrum beta-lactamase- and/or metallo-beta-lactamase-producing gram-negative strains, colistin-resistant strains, vancomycin- and/or linezolid-resistant enterococci, and methicillin-resistant Staphylococcus aureus (MRSA). Tigecycline showed excellent activity against a collection of difficult-to-treat pathogens currently encountered in the hospital setting.

Use of germicides in the home and the healthcare setting: is there a relationship between germicide use and antibiotic resistance?

BACKGROUND

The spread of antibiotic-resistant pathogens represents an increasing threat in healthcare facilities. Concern has been expressed that the use of surface disinfectants and antiseptics may select for antibiotic-resistant pathogens.

OBJECTIVE

To review the scientific literature on whether there is a link between use of germicides (ie, disinfectants and antiseptics) and bacterial resistance to antibiotics. In addition, we will review whether antibiotic-resistant bacteria exhibit altered susceptibility to germicides that are recommended for use as disinfectants or antiseptics.

DESIGN

A review of the appropriate scientific literature.

RESULTS

In the laboratory, it has been possible to develop bacterial mutants with reduced susceptibility to disinfectants and antiseptics that also demonstrate decreased susceptibility to antibiotics. However, the antibiotic resistance described was not clinically relevant because the test organism was rarely a human pathogen, the altered level of antimicrobial susceptibility was within achievable serum levels for the antibiotic, or the antibiotic tested was not clinically used to treat the study pathogen. Similarly, wild-type strains with reduced susceptibility to disinfectants (principally, quaternary ammonium compounds) and antiseptics (principally, triclosan) have been reported. However, because the concentration of disinfectants used in the healthcare setting greatly exceeds the concentration required to kill strains with reduced susceptibility to disinfectants, the clinical relevance of these observations is questionable.

CONCLUSION

To date, there is no evidence that using recommended antiseptics or disinfectants selects for antibiotic-resistant organisms in nature. Disinfectants and antiseptics should be used when there are scientific studies demonstrating benefit or when there is a strong theoretical rationale for using germicides.

Trends in production of extended-spectrum beta-lactamases among enterobacteria of medical interest: report of the second Italian nationwide survey

Results of a 2003 survey carried out in Italy to evaluate the prevalence of extended-spectrum beta-lactamase (ESBL)-producing enterobacteria are presented. Eleven Italian Microbiology Laboratories investigated 9,076 consecutive nonreplicate isolates (inpatients, 6,850; outpatients, 2,226). ESBL screening was performed by MIC data analysis. Confirmation was obtained using the double-disk synergy test and the combination disk test based on CLSI methodology. ESBL determinants were investigated by colony blot hybridization and confirmed by sequencing. Results were compared to those of the 1999 Italian survey (8,015 isolates). The prevalence of ESBL producers was 7.4% among isolates from inpatients (in 1999, 6.3%) and 3.5% among outpatients (no data were available for 1999). Among hospitalized patients, the most prevalent ESBL-positive species was Escherichia coli (Klebsiella pneumoniae in 1999). Proteus mirabilis was the most prevalent ESBL-positive species among outpatients. In both groups, most ESBL-positive pathogens were obtained from urinary tract infections. TEM-type ESBLs were the most prevalent enzymes (45.4%). Non-TEM, non-SHV determinants emerged: CTX-M-type in E. coli and K. pneumoniae, and PER-type in P. mirabilis, Providencia spp., and E. coli. With the exception of 3/163 P. mirabilis isolates and 1/44 Providencia stuartii isolate (all of which were intermediate for imipenem), carbapenems were active against all ESBL-positive enterobacteria. Susceptibility to other drugs was as follows: 84.7% for amikacin, 84.4% for piperacillin-tazobactam, 48.0% for gentamicin, and 32.8% for ciprofloxacin. Carbapenems appear to be the drug of choice. Amikacin and beta-lactam/beta-lactamase inhibitor combinations represent an alternative in non-life-threatening infections. The appearance of ESBL-positive enterobacteria in the community makes it mandatory that family physicians learn how to treat these pathogens.

Acquisition of imipenem-resistant Acinetobacter baumannii in a pediatric intensive care unit: A case-control study

OBJECTIVE

To investigate the risk factors associated with nosocomial acquisition of imipenem-resistant Acinetobacter baumannii (IRAB) among pediatric intensive care patients. A retrospective case control study was conducted in a pediatric intensive care unit (PICU).

PATIENTS AND PARTICIPANTS

Cases were children in whom IRAB was isolated from any clinical specimen obtained at least 48 h following admission to PICU. Controls were children without IRAB matched to cases in 2:1 ratio. Twenty-six cases were matched with 52 controls according to the chronological order of admission.

MEASUREMENTS AND RESULTS

Between July 2001 and December 2003, 52 (62%) of 84 clinical A. baumannii isolates were found nonsusceptible to imipenem (MIC > or = 8 microg/ml). Demographic variables, comorbid conditions, clinical picture at admission, invasive procedures, use of antimicrobials and other drugs were analyzed as potential risk factors. Use of carbapenems and other beta-lactams, aminoglycosides, ranitidine, mechanical ventilation, central venous or urinary catheters and length of stay in PICU were among the factors significantly associated with IRAB acquisition in the univariate analysis. By multivariate analysis, however, only aminoglycoside use and length of stay in the PICU were independent risk factors.

CONCLUSIONS

Acquisition of IRAB by PICU patients was independently associated with aminoglycoside use and prolonged stay in the unit. Studies of evaluation of infection control policies need to be pursued.