Bacteriogenic synthesis of morphologically diverse silver nanoparticles and their assessment for methyl orange dye removal and antimicrobial activity.

Nanotechnology and nanoparticles have gained massive attention in the scientific community in recent years due to their valuable properties. Among various AgNPs synthesis methods, microbial approaches offer distinct advantages in terms of cost-effectiveness, biocompatibility, and eco-friendliness. In the present research work, investigators have synthesized three different types of silver nanoparticles (AgNPs), namely AgNPs-K, AgNPs-M, and AgNPs-E, by using Klebsiella pneumoniae (MBC34), Micrococcus luteus (MBC23), and Enterobacter aerogenes (MBX6), respectively. The morphological, chemical, and elemental features of the synthesized AgNPs were analyzed by using UV-Vis spectroscopy (UV-Vis), Fourier transform-infrared spectroscopy (FTIR), X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and energy-dispersive spectroscopy (EDX). UV-Vis absorbance peaks were obtained at 475, 428, and 503 nm for AgNPs-K, AgNPs-M, and AgNPs-E, respectively. The XRD analysis confirmed the crystalline nature of the synthesized AgNPs, having peaks at 26.2°, 32.1°, and 47.2°. At the same time, the FTIR showed bands at 599, 963, 1,693, 2,299, 2,891, and 3,780 cm-1 for all the types of AgNPs indicating the presence of bacterial biomolecules with the developed AgNPs. The size and morphology of the AgNPs varied from 10 nm to several microns and exhibited spherical to porous sheets-like structures. The percentage of Ag varied from 37.8% (wt.%) to 61.6%, i.e., highest in AgNPs-K and lowest in AgNPs-M. Furthermore, the synthesized AgNPs exhibited potential for environmental remediation, with AgNPs-M exhibiting the highest removal efficiency (19.24% at 120 min) for methyl orange dye in simulated wastewater. Further, all three types of AgNPs were evaluated for the removal of methyl orange dye from the simulated wastewater, where the highest dye removal percentage was 19.24% at 120 min by AgNPs-M. Antibacterial potential of the synthesized AgNPs assessment against both Gram-positive (GPB) Bacillus subtilis (MBC23), B. cereus (MBC24), and Gram-negative bacteria Enterococcus faecalis (MBP13) revealed promising results, with AgNPs-M, exhibiting the largest zone of inhibition (12 mm) against GPB B. megaterium. Such investigation exhibits the potential of the bacteria for the synthesis of AgNPs with diverse morphology and potential applications in environmental remediation and antibacterial therapy-based synthesis of AgNPs.

Molecular Epidemiology of Carbapenem-Resistant Klebsiella aerogenes in Japan.

Information regarding Klebsiella aerogenes haboring carbapenemase in Japan is limited. A comprehensive nationwide survey was conducted from September 2014 to December 2022, and 67 non-duplicate strains of carbapenem-resistant K. aerogenes were isolated from 57 healthcare facilities in Japan. Through genetic testing and whole-genome sequencing, six strains were found to possess carbapenemases, including imipenemase (IMP)-1, IMP-6, New Delhi metallo-ß-lactamase (NDM)-1, and NDM-5. The strain harboring blaNDM-5 was the novel strain ST709, which belongs to the clonal complex of the predominant ST4 in China. The novel integron containing blaIMP-1 featured the oxacillinase-101 gene, which is a previously unreported structure, with an IncN4 plasmid type. However, integrons found in the strains possessing blaIMP-6, which were the most commonly identified, matched those reported domestically in Klebsiella pneumoniae, suggesting the prevalence of identical integrons. Transposons containing blaNDM are similar or identical to the transposon structure of K. aerogenes harboring blaNDM-5 previously reported in Japan, suggesting that the same type of transposon could have been transmitted to K. aerogenes in Japan. This investigation analyzed mobile genetic elements, such as integrons and transposons, to understand the spread of carbapenemases, highlighting the growing challenge of carbapenem-resistant Enterobacterales in Japan and underscoring the critical need for ongoing surveillance to control these pathogens.

Comparative Genomic Analysis and Phenotypic Characterization of Bronchoscope-Associated Klebsiella aerogenes.

Bronchoscopes have been linked to outbreaks of nosocomial infections. The phenotypic and genomic profiles of bronchoscope-associated Klebsiella aerogenes isolates are largely unknown. In this work, a total of 358 isolates and 13 isolates were recovered from samples after clinical procedures and samples after decontamination procedures, respectively, over the five months. Antimicrobial susceptibility testing found seven K. aerogenes isolates exhibiting a low-level resistance to antimicrobial agents. Among seven K. aerogenes isolates, we found five sequence types (STs) clustered into three main clades. Collectively, this study described for the first time the phenotypic and genomic characteristics of bronchoscope-associated K. aerogenes.

Activity of ceftazidime/avibactam, meropenem/vaborbactam and imipenem/relebactam against carbapenemase-negative carbapenem-resistant Enterobacterales isolates from US hospitals.

We investigated the prevalence, resistance mechanisms and activity of ceftazidime/avibactam, meropenem/vaborbactam, imipenem/relebactam and comparator agents against carbapenem-resistant Enterobacterales (CRE) that did not carry carbapenemase genes. Among 304 CRE isolates collected in US hospitals during 2016-2018 (1.1% of the overall Enterobacterales), 45 (14.8%) isolates did not carry carbapenemases. These isolates were mainly Klebsiella aerogenes (n = 11), Enterobacter cloacae (n = 11) and Klebsiella pneumoniae (n = 10). Isolates harboured one to six ß-lactam resistance mechanisms (median, three mechanisms). Acquired ß-lactamase genes were detected in 21 isolates; blaCTX-M-15 was the most common acquired ß-lactamase gene found (14 isolates). All 11 K. aerogenes and 6 E. cloacae isolates overexpressed AmpC. Only one isolate belonging to these species carried acquired ß-lactamase genes. Disruptions or reduced expression of both outer membrane proteins (ompC/ompK36 and ompF/ompK35) were detected among 20 isolates. AcrAB-TolC was modestly expressed or overexpressed among 19 isolates from six species. One E. coli isolate produced a CTX-M-15 variant that displayed an increased meropenem minimum inhibitory concentration (MIC) when expressed in a clean background. Most ß-lactam agents had limited activity against CRE isolates that did not carry carbapenemases. Ceftazidime/avibactam inhibited all isolates, while imipenem/relebactam and meropenem/vaborbactam inhibited 93.0% (88.9% if Proteus mirabilis is included) and 93.3% of tested isolates at current breakpoints. The resistance mechanisms among CRE isolates that did not produce carbapenemases are complex; ß-lactam/ß-lactamase inhibitor combinations might have different activity against these isolates depending on their resistance mechanisms and the bacterial species.

A Transferable IncC-IncX3 Hybrid Plasmid Cocarrying blaNDM-4, tet(X), and tmexCD3-toprJ3 Confers Resistance to Carbapenem and Tigecycline.

Tigecycline is a last-resort antimicrobial against carbapenemase-producing Enterobacterales (CPE). However, mobile tigecycline resistance genes, tet(X) and tmexCD-toprJ, have emerged in China and have spread possibly worldwide. Tet(X) family proteins function as tigecycline-inactivating enzymes, and TMexCD-TOprJ complexes function as efflux pumps for tigecycline. Here, to the best of our knowledge we report a CPE isolate harboring both emerging tigecycline resistance factors for the first time. A carbapenem- and tigecycline-resistant Klebsiella aerogenes strain, NUITM-VK5, was isolated from an urban drainage in Vietnam in 2021, and a plasmid, pNUITM-VK5_mdr, cocarrying tet(X) and tmexCD3-toprJ3 along with the carbapenemase gene blaNDM-4 was identified in NUITM-VK5. pNUITM-VK5_mdr was transferred to Escherichia coli by conjugation and simultaneously conferred high-level resistance against multiple antimicrobials, including carbapenems and tigecycline. An efflux pump inhibitor reduced TMexCD3-TOprJ3-mediated tigecycline resistance, suggesting that both tigecycline resistance factors independently and additively contribute to the high-level resistance. The plasmid had the IncX3 and IncC replicons and was estimated to be a hybrid of plasmids with different backbones. Unlike IncX3 plasmids, IncC plasmids are stably maintained in an extremely broad range of bacterial hosts in humans, animals, and the environment. Thus, the future global spread of multidrug resistance plasmids such as pNUITM-VK5_mdr poses a public health crisis. IMPORTANCE Tigecycline is important as a last-resort antimicrobial and effective against antimicrobial-resistant bacteria, such as carbapenem-producing Enterobacterales (CPE), whose infections are difficult to treat with antimicrobials. Since 2019, mobile tigecycline resistance genes, tet(X) and tmexCD-toprJ, and their variants have been reported mainly from China, and it has become important to understand their epidemiological situation and detailed genetic mechanisms. In this study, we identified a bacterial isolate coharboring tet(X) and tmexCD-toprJ on the same plasmid. A Klebsiella aerogenes isolate in Vietnam carried both these tigecycline resistance genes on a transferable plasmid leading to high-level resistance to multiple clinically important antimicrobials, including carbapenem and tigecycline, and could actually transfer the plasmid to other bacteria. The spread of such a multidrug resistance plasmid among bacterial pathogens should be of great concern because there are few antimicrobials to combat bacteria that have acquired the plasmid.

Impact of pH on citric acid antimicrobial activity against Gram-negative bacteria.

The antimicrobial activity of citric acid (CA) is often evaluated without pH adjustment or control and its impact on micro-organisms is better understood in acidic conditions. However, the biocidal action of the fully ionized CA molecule, predominantly available at higher pH, has not been previously investigated. The objective of this study was to evaluate the antimicrobial effect of high (10%) and low (1%) concentrations of CA, each adjusted over a wide range of pH values (4·5, 6·5 and 9·5) relative to the controls exposed to corresponding pH levels alone (no CA). The viability and morphology of Escherichia coli and Klebsiella aerogenes were evaluated using a culture-based enumeration assay in parallel with direct SEM imaging. Overall, the highest membrane damage and loss in viability were achieved with 10% CA at pH 9·5, which yielded at least 4·6 log10 CFU per ml (P < 0·001) reductions in both organisms. Insight into the superior efficacy of CA at high pH is proposed based on zeta potential measurements which reveal a more negatively charged bacterial surface at higher pH. This pH-dependent increase in surface charge may have rendered the cells potentially more sensitive towards chelants such as CA3- that interact with membrane-stabilizing divalent metals.

Colorimetric detection of residual quaternary ammonium compounds on dry surfaces and prediction of antimicrobial activity using bromophenol blue.

Controlling and monitoring the residual activity of quaternary ammonium compounds (QACs) are critical for maintaining safe yet effective levels of these agents in the environment. This study investigates the utility of bromophenol blue (BPB) as a safe, rapid and user-friendly indicator to detect in situ residual QACs dried on hard, non-porous surfaces, as well a means to assess their antimicrobial efficacy. At pH 7, BPB has a purple colour which turns blue upon its complexation with QACs such as didecyldimethylammonium chloride (DDAC). BPB itself has no antimicrobial properties up to 400 ppm. Within the range of 0-400 ppm, BPB colour change was tied to specific DDAC antimicrobial performances with a detection threshold of 100 ppm. BPB concentration and application volume could be adjusted such that a colour shift from purple to blue correlated with a set percent reduction (>99·9%) in test bacteria (Staphylococcus aureus and Klebsiella aerogenes). The BPB solutions developed in this study yielded similar colour shifts on polycarbonate and stainless steel surfaces and did not cross-react with chemical ingredients commonly found in sanitizers and disinfectant products. Overall, this study suggests that BPB provides a simple solution to safely monitor the post-application level and biocidal activity of residual dried QACs on surfaces.

Polymyxin resistance in carbapenem-resistant Enterobacteriaceae isolates from patients without polymyxin exposure: a multicentre study in China.

Polymyxins were recently approved for the clinical treatment of carbapenem-resistant Enterobacteriaceae (CRE) infections in China. The aim of this study was to determine the prevalence and molecular mechanisms of polymyxin-resistant CRE prior to the clinical application of polymyxin and to evaluate the potential for emerging polymyxin resistance in China. A total of 504 unique CRE isolates were collected from six tertiary-care hospitals in China between October 2016 and September 2017. All isolates underwent antimicrobial susceptibility testing. Clinical, demographic, antimicrobial exposure and infection data were collected from patients' medical charts. PCR detection, Sanger sequencing and reverse transcription real-time fluorescence quantitative PCR (RT-qPCR) were used to investigate the molecular mechanism of polymyxin resistance. A total 19 (3.8%) polymyxin-resistant isolates were identified, including Klebsiella pneumoniae, Escherichia coli, Klebsiella aerogenes and Enterobacter cloacae. Genetic analysis in K. pneumoniae strains identified insertion sequence (IS) elements (n = 3), a stop codon (n = 1) and gene deletion (n = 2) in mgrB and a pmrB missense mutation (T157P) (n = 1). Two E. coli isolates contained mcr-1 and an E. cloacae strain harboured a frameshift in mgrB. Further transcriptional analysis showed that pmrA, pmrB, pmrC and pmrK were significantly upregulated in polymyxin-resistant isolates. Despite the lack of polymyxin exposure, 3.8% of CRE were resistant to polymyxin in China. Both chromosomal and plasmid-encoded mechanisms were identified. Our study suggests that clinical practice should be alert to pre-existing polymyxin resistance among CRE isolates to avoid further dissemination of polymyxin resistance.

7X multiplexed, optofluidic detection of nucleic acids for antibiotic-resistance bacterial screening.

Rapid and accurate diagnosis of bacterial infections resistant to multiple antibiotics requires development of new bio-sensors for differentiated detection of multiple targets. This work demonstrates 7x multiplexed detection for antibiotic-resistance bacterial screening on an optofluidic platform. We utilize spectrally multiplexed multi-spot excitation for simultaneous detection of nucleic acid strands corresponding to bacterial targets and resistance genes. This is enabled by multi-mode interference (MMI) waveguides integrated in an optofluidic device. We employ a combinatorial three-color labeling scheme for the nucleic acid assays to scale up their multiplexing capability to seven different nucleic acids, representing three species and four resistance genes.

The combined antibacterial and anticancer properties of nano Ce-containing Mg-phosphate ceramic.

AIM: This paper was mainly aimed at synthesis of Ce-containing nano-Mg-phosphate ceramic as a multifunctional material. MATERIALS AND METHODS: Two ceramics based on Mg3(PO4)2 and Ce0.2Mg2.8(PO4)2 formulas (MP and MP-C, respectively) were synthesized. The synthesized powders were characterized by XRD, TEM, Zeta potential, and FTIR. Also, their dissolution behavior was tested in Tris-HCl buffer solution. Moreover, the antimicrobial efficacy was evaluated against gram-positive bacteria (Bacillus sphaericus MTCC 511 &Staphylococcus aureus MTCC 87) and gram-negative bacteria (Enterobacter aerogenes MTCC 111 &Pseudomonas aeruginosa MTCC 1034) using dick diffusion assay and microdilution method. Furthermore, the cell viability test was performed for the ceramics on Vero cells (African green monkey kidney cells), and their antitumor activity was determined by PC3 cell line (prostatic cancer). Also, the cellular uptake was determined by the flow cytometry. KEY FINDINGS: The results showed that the substitution of Mg by Ce decreased the particle size from 40 to 90 nm for MP sample to 2-10 nm for MP-C sample and increased the degradation rate. Both samples showed excellent antimicrobial activities. Moreover, MP demonstrated more cell viability than MP-C on Vero cells at high concentrations, whereas, MP-C showed more antitumor activity on PC3 cells than MP sample. Moreover, MP-C showed a higher cell uptake than MP due to its smaller size and more negative charge. SIGNIFICANCE: Mg-phosphate ceramic can be used in this study successfully as a delivery system for cerium ions and showed a high antitumor activity, which makes it highly recommended as safe and effective cancer treatment materials.

Ceftazidime-avibactam activity against a challenge set of carbapenem-resistant Enterobacterales: Ompk36 L3 alterations and ß-lactamases with ceftazidime hydrolytic activity lead to elevated MIC values.

INTRODUCTION: This study examined ceftazidime-avibactam activity against carbapenem-resistant Enterobacterales (CRE) clinical isolates and resistance mechanisms among non-metallo ß-lactamase (MBL) producers displaying ceftazidime-avibactam MIC values at 4 mg/L. METHODS: CRE isolates (286 of 8161 Enterobacterales) collected in Asia-Pacific, Europe and Latin America during 2016 were screened for carbapenemase genes. Selected isolates were susceptibility tested for ceftazidime-avibactam in the presence or absence of phenylalanine-arginyl ß-naphthylamide (PAßN) and polymyxin B nonapeptide (PMBN). Genome sequences were investigated for the integrity of outer membrane protein (OMP) genes and multilocus sequence typing. qRT-PCR assays were conducted to determine expression of acrA, ampC, and OMP genes. RESULTS: Ceftazidime-avibactam inhibited 99.2% of the Enterobacterales, 22 (78.7%) of the 286 CRE and 226 (100%) non-MBL producers. Among carbapenemase producers (85.3%; 244 of 286), the most common gene was blaKPC (76 blaKPC-3 and 46 blaKPC-2), followed by blaOXA-48-like (60 isolates) and blaNDM (37). Ceftazidime-avibactam MIC values at 4 mg/L were noted among 14 Klebsiella pneumoniae (13 carrying blaKPC and 1 blaCTX-M-15) mostly from Italy and Brazil and 1 Klebsiella aerogenes overexpressing ampC. PAßN did not significantly decrease ceftazidime-avibactam results, but adding PMBN did significantly decrease the MIC results for the combination. All K. pneumoniae isolates had a premature stop codon at OmpK35 and most isolates had L3 alterations of OmpK36, low expression of this gene, or OmpC disruption (K. aerogenes). Nine K. pneumoniae isolates belonged to clonal complex 258 and displayed intrahospital clonality. CONCLUSION: Ceftazidime-avibactam is an important addition to the armamentarium against multidrug-resistant organisms, and elevated MIC results for this combination seem to be associated with L3 OmpK36 alterations and ß-lactamases able to hydrolyze ceftazidime.

Dual Valorization of Olive Mill Wastewater by Bio-Nanosynthesis of Magnesium Oxide and Yarrowia lipolytica Biomass Production.

This research investigates an efficient dual valorization of olive mill wastewater in the biosynthesis of magnesium oxide nanoparticles and in the depollution of the effluent by Yarrowia lipolytica growth evaluation. After removal of polyphenols, the recovered biophenols were reacted with the magnesium precursor to provide magnesium oxide nanoparticles. In order to confirm the biosynthesized magnesium oxide nanoparticles, several analyses were undertaken. The Fourier transform infrared spectrum gives a broad absorption at 658 cm-1 confirming the presence of the magnesium oxide nanoparticles, while the UV/VIS absorption spectroscopy reveals an intense transition with a maximum absorption at 300 nm. The X-ray diffraction and transmission electron microscopy analyses show that nanoparticles are in pure cubic crystalline with spherical and hexagonal shapes (average size is 19.4 nm). The zeta potential analysis illustrates a negative potential proving a good stability of the biosynthesized nanoparticles. Nanoparticles were assigned for their in vitro antibacterial activity against Escherichia coli, Enterobacter aerogenes, Salmonella typhimurium, Staphylococcus cohnii, and Bacillus niacini. The evaluation of the growth of Yarrowia lipolytica on the recovered olive mill wastewater after removal of polyphenols yielded 3.2 g/L of the Yarrowia biomass in 72 h without nutriment additions, providing an important decrease of chemical oxygen demand (73 %).

Green Synthesis of Silver Nanoparticles Using Artocarpus hirsutus Seed Extract and its Antibacterial Activity.

AIMS: To evaluate the antibacterial activity of Artocarpus hirsutus mediated seed extract for nanoparticle synthesis. BACKGROUND: Gastrointestinal bacteria are known for causing deadly infections in humans. They also possess multi-drug resistance and interfere with clinical treatments. Applied nanotechnology has been known to combat such infectious agents with little interference from their special attributes. Here we synthesize silver nanoparticles from Artocarpus hirsutus seed extract against two gastro-intestinal bacterial species: Enterobacter aerogenes and Listeria monocytogenes. OBJECTIVE: To collect, dry, and process seeds of Artocarpus hirsutus for nanoparticle synthesis. To evaluate the morphological interaction of silver nanoparticles with bacteria. METHODS: Artocarpus hirsutus seeds were collected and processed and further silver nanoparticles were synthesized by the co-precipitation method. The synthesized nanoparticles were characterized using XRD, UV, FTIR, and SEM. These nanoparticles were employed to study the antibacterial activity of nanoparticles against Enterobacter aerogenes and Listeria monocytogenes using well diffusion method. Further, morphological interaction of silver nanoparticles on bacteria was studied using SEM. RESULTS: Silver nanoparticles were synthesized using Artocarpus hirsutus seed extract and characterization studies confirmed that silver nanoparticles were spherical in shape with 25-40 nm size. Antibacterial study exhibited better activity against Enterobacter aerogenes with a maximum zone of inhibition than on Listeria monocytogenes. SEM micrographs indicated that Enterobacter aerogenes bacteria were more susceptible to silver nanoparticles due to the absence of cell wall. Also, the size and charge of silver nanoparticles enable easy penetration of the bacterial cell wall. CONCLUSION: In this study, silver nanoparticles were synthesized using the seed extract of Artocarpus hirsutus for the first time exploiting the fact that Moraceae species have high phytonutrient content which aided in nanoparticle synthesis. This nanoparticle can be employed for large scale synthesis which when coupled with the pharmaceutical industry can be used to overcome the problems associated with conventional antibiotics to treat gastrointestinal bacteria.

Occurrence of CTX-M-15- and MCR-1-producing Enterobacterales in pigs in Portugal: Evidence of direct links with antibiotic selective pressure.

AIMS: To undertake a prospective analysis of the occurrence of colistin-resistant and extended-spectrum ß-lactamase (ESBL)-producing Enterobacterales colonizing pigs at two farms in Portugal, and to evaluate the putative correlations with usage of different antibiotics. MATERIALS AND METHODS: One hundred and two faecal samples recovered from two different Portuguese pig farms were screened for polymyxin-resistant and ESBL-positive Enterobacterales. The authors had undertaken a study at one of the farms previously, but the use of colistin has since been banned; zinc oxide and amoxicillin are used as prophylactic and curative drugs, respectively, at this farm. The other farm included in this study used zinc oxide alone. RESULTS: Ninety-three ESBL-producing isolates (62 Escherichia coli, 29 Klebsiella pneumoniae, one Enterobacter aerogenes and one Enterobacter cloacae) and 17 colistin-resistant isolates (12 E. coli, four K. pneumoniae and one E. cloacae) were recovered. Among the ESBL producers, the majority (84%) produced CTX-M-15, while the others produced CTX-M-1 or CTX-M-9. Many different strain and plasmid backgrounds were identified, ruling out a massive dissemination of one major clone. In total, 17 colistin-resistant isolates were recovered, all from the first farm. All produced MCR-1, corresponding to 12 E. coli (10 clones) and three K. pneumoniae (two clones). The MCR-1 producers were all recovered from the farm where colistin had been used 2 years previously. CONCLUSION: This study showed a surprisingly high rate of CTX-M-15 producers at two Portuguese pig farms. A link was found between antibiotic selective pressure (ß-lactam or polymyxin) and the corresponding resistance rate.

Susceptibility evolution to antibiotics of Enterobacter cloacae, Morganella morganii, Klebsiella aerogenes and Citrobacter freundii involved in urinary tract infections: an 11-year epidemiological surveillance study. / Evolución de la sensibilidad a los antibióticos de Enterobacter cloacae, Morganella morganii, Klebsiella aerogenes y Citrobacter freundii causantes de infecciones del tracto urinario: un estudio de vigilancia epidemiológica de 11 años.

INTRODUCTION: The objective of this study was to analyse the susceptibility to antibiotic of Citrobacter freundii, Klebsiella aerogenes, Enterobacter cloacae, Serratia marcescens, Providencia stuartii and Morganella morganii (CESPM group), detected in urine cultures. METHODS: Between 2006 and 2016 we analyzed CESPM group Enterobacteria isolated from urine cultures from both primary health-care centers and Hospital Virgen de las Nieves (Granada). We studied the susceptibility to aminoglycosides, fosfomycin, nitrofurantoin, quinolones, piperacillin/tazobactam, cefepime, imipenem and trimethoprim/sulfamethoxazole following CLSI interpretation criteria. RESULTS: A total of 736 isolates were studied: 30.57% E. cloacae, 23.50% M. morganii, 20.38% K. aerogenes, 10.32% C. freundii, 8.83% S. marcescens and 6.38% P. stuartii. A significant decrease in the antibiotic susceptibility was observed. Gentamicin, ciprofloxacin, imipenem and cefepime showed susceptibility over 80%. CONCLUSIONS: E. cloacae, M. morganii and K. aerogenes were the most common isolates. Cefepime and imipenem are still a good empiric therapeutic alternative given its activity in vitro.

Outbreak of Efficiently Transferred Carbapenem-Resistant blaNDM-Producing Gram-Negative Bacilli Isolated from Neonatal Intensive Care Unit of an Indian Hospital.

The emergence of blaNDM particularly in Gram-negative bacteria is a burden on the health care system in developing countries. Hence, this study was initiated to screen New Delhi Metallo-ß-lactamase (NDM)-producing Gram-negative bacterial strains from neonatal intensive care unit (NICU) of an Indian Hospital. A total of 18 blaNDM-producing isolates were detected in the present study. Out of 18 blaNDM variant isolates, 6 were Klebsiella pneumoniae, 4 Escherichia coli, 2 Enterobacter aerogenes, 1 Acinetobacter lwoffii, 1 Enterobacter cloacae, 3 Acinobacter baumannii, and 1 Cedecea davisae from NICU, showing resistance against all antibiotics, except colistin and polymixin. The transferability of resistance determinants was tested by conjugation. Transfer of blaNDM-producing strains was successful in all 18 strains. In the case of transconjugants, the minimum inhibitory concentration values were found to decrease. The blaNDM-producing isolates contained detectable plasmids of size 66, 38, and 6 kb. Plasmi/d-based replicon typing revealed the incompatibility types Inc (A/C, FIIA, FIC, K, F, W, FIA, P, X, FIB, B/O) in blaNDM-carrying isolates. This study revealed the outbreak of multiple variants of blaNDM (13 NDM-1, 4 NDM-5, and 1 NDM-7). Moreover, other resistance markers, viz. blaOXA-1, blaCMY-1, blaVIM-1, and blaSHV-1 coassociated with blaNDM were also found. In this study, we reported NDM-producing C. davisae as a first report to the best of our knowledge. This study is an attempt to reveal the dissemination of blaNDM isolated from neonates in NICU and their efficient transferability among Gram-negative bacilli through horizontal gene transfer.

Synthesis and characterization of nanoparticles and composites as bactericides.

In the present study, SiO2-TiO2 hybrid nanomaterial and zeolite-TiO2 (Z-TiO2) composites were synthesized by the sol-gel method. Then, the antibacterial activity of the above-mentioned synthesized materials, SiO2 and zeolite (Z) was investigated by the disk diffusion method using Echerichia coli and Enterobacter aerogenes as test microorganisms. All the materials showed antibacterial activity against E. coli with 7.2, 10.7, 3.5 and 8.2 mm of inhibition zone for SiO2-TiO2 hybrid nanomaterial, SiO2, zeolite and Z-TiO2 composite, respectively. However, none of them showed antibacterial activity against E. aerogenes. The obtained results pointed out that these natural-based materials (i.e. Z, SiO2, Z-TiO2 and SiO2-TiO2), known to be noncarcinogenic and nontoxic, can be used as disinfectants against E. coli (an important indicator of the bacteriological quality of water) as safe and eco-friendly alternatives to chlorine.

Genomic analysis unveils important aspects of population structure, virulence, and antimicrobial resistance in Klebsiella aerogenes.

Klebsiella aerogenes is an important pathogen in healthcare-associated infections. Nevertheless, in comparison to other clinically important pathogens, K. aerogenes population structure, genetic diversity, and pathogenicity remain poorly understood. Here, we elucidate K. aerogenes clonal complexes (CCs) and genomic features associated with resistance and virulence. We present a detailed description of the population structure of K. aerogenes based on 97 publicly available genomes by using both multilocus sequence typing and single-nucleotide polymorphisms extracted from the core genome. We also assessed virulence and resistance profiles using Virulence Finder Database and Comprehensive Antibiotic Resistance Database, respectively. We show that K. aerogenes has an open pangenome and a large effective population size, which account for its high genomic diversity and support that negative selection prevents fixation of most deleterious alleles. The population is structured in at least 10 CCs, including two novel ones identified here, CC9 and CC10. The repertoires of resistance genes comprise a high number of antibiotic efflux proteins as well as narrow- and extended-spectrum ß-lactamases. Regarding the population structure, we identified two clusters based on virulence profiles because of the presence of the toxin-encoding clb operon and the siderophore production genes, irp and ybt. Notably, CC3 comprises the majority of K. aerogenes isolates associated with hospital outbreaks, emphasizing the importance of constant monitoring of this pathogen. Collectively, our results may provide a foundation for the development of new therapeutic and surveillance strategies worldwide.