Selenomethionine Inhibits NF-κB-mediated Inflammatory Responses of Bovine Mammary Epithelial Cells Caused by Klebsiella pneumoniae by Increasing Autophagic Flux.

Klebsiella pneumoniae (K. pneumoniae) is one of the major pathogens causing bovine clinical mastitis. Autophagy maintains cellular homeostasis and resists excessive inflammation in eukaryotic organisms. Selenomethionine (Se-Met) is commonly used as a source of selenium supplementation for dairy cows. This study aimed to investigate the effects of Se-Met on inflammatory responses mediated by nuclear factor-kappa B (NF-κB) through autophagy. We infected bovine mammary epithelial cell line (MAC-T) with K. pneumoniae and examined the expression of autophagy-related proteins and changes in autophagic vesicles, LC3 puncta, and autophagic flux at various intervals. The results showed that K. pneumoniae activated the early-stage autophagy of MAC-T cells. The levels of LC3-II, Beclin1, and ATG5, as well as the number of LC3 puncta and autophagic vesicles, increased after 2 h post-treatment. However, the late-stage autophagic flux was blocked. Furthermore, the effect of autophagy on NF-κB-mediated inflammation was investigated with different autophagy levels. The findings showed that enhanced autophagy inhibited the K. pneumoniae-induced inflammatory responses of MAC-T cells. The opposite results were found with the inhibition of autophagy. Finally, we examined the effect of Se-Met on NF-κB-mediated inflammation based on autophagy. The results indicated that Se-Met alleviated K. pneumoniae-induced autophagic flux blockage, inhibited NF-κB-mediated inflammation, and decreased the adhesion of K. pneumoniae to MAC-T cells. The inhibitory effect of Se-Met on NF-κB-mediated inflammation could be partially blocked by the autophagy inhibitor chloroquine (CQ). Overall, Se-Met attenuated K. pneumoniae-induced NF-κB-mediated inflammatory responses by enhancing autophagic flux.

Optimization of sequence and chiral content enhances therapeutic potential of tilapia piscidin peptides.

Because antimicrobial peptides (AMPs) often exhibit broad-spectrum bactericidal potency, we sought to develop peptide-based antimicrobials for potential clinical use against drug-resistant pathogens. To accomplish this goal, we first optimized the amino acid sequence of a broad-spectrum AMP known as Tilapia Piscidin 4 (TP4). Then, we used the optimized sequence to create a pair of heterochiral variants (TP4-α and TP4-ß) with different percentages of D-enantiomers, as poly-L peptides often exhibit poor pharmacokinetic profiles. The conformations of the peptide pair exhibited inverted chirality according to CD and NMR spectroscopic analyses. Both heterochiral peptides displayed enhanced stability and low hemolysis activities. Irrespective of their different d-enantiomer contents, both heterochiral peptides exhibited bactericidal activities in the presence of human serum or physiological enzymes. However, the peptide with higher d-amino acid content (TP4-ß) caused better bacterial clearance when tested in mice infected with NDM-1 K. pneumoniae. In addition, we observed a relatively higher hydrogen bonding affinity in a simulation of the interaction between TP4-ß and a model bacterial membrane. In sum, our results demonstrate that the current design strategy may be applicable for development of new molecules with enhanced stability and in vivo antimicrobial activity.

D-amino Acids Ameliorate Experimental Colitis and Cholangitis by Inhibiting Growth of Proteobacteria: Potential Therapeutic Role in Inflammatory Bowel Disease.

BACKGROUND & AIMS: D-amino acids, the chiral counterparts of protein L-amino acids, were primarily produced and utilized by microbes, including those in the human gut. However, little was known about how orally administered or microbe-derived D-amino acids affected the gut microbial community or gut disease progression. METHODS: The ratio of D- to L-amino acids was analyzed in feces and blood from patients with ulcerative colitis (UC) and healthy controls. Also, composition of microbe was analyzed from patients with UC. Mice were treated with D-amino acid in dextran sulfate sodium colitis model and liver cholangitis model. RESULTS: The ratio of D- to L-amino acids was lower in the feces of patients with UC than that of healthy controls. Supplementation of D-amino acids ameliorated UC-related experimental colitis and liver cholangitis by inhibiting growth of Proteobacteria. Addition of D-alanine, a major building block for bacterial cell wall formation, to culture medium inhibited expression of the ftsZ gene required for cell fission in the Proteobacteria Escherichia coli and Klebsiella pneumoniae, thereby inhibiting growth. Overexpression of ftsZ restored growth of E. coli even when D-alanine was present. We found that D-alanine not only inhibited invasion of pathological K. pneumoniae into the host via pore formation in intestinal epithelial cells but also inhibited growth of E. coli and generation of antibiotic-resistant strains. CONCLUSIONS: D-amino acids might have potential for use in novel therapeutic approaches targeting Proteobacteria-associated dysbiosis and antibiotic-resistant bacterial diseases by means of their effects on the intestinal microbiota community.

Crippling of Klebsiella pneumoniae virulence by metformin, N-acetylcysteine and secnidazole.

INTRODUCTION: The emergence of multidrug-resistant Klebsiella pneumoniae in hospitals represents a serious threat to public health. Infections caused by Klebsiella pneumoniae are widespread in healthcare institutions, mainly pneumonia, bloodstream infections, and infections affecting neonates in intensive care units; so, it is necessary to combat this pathogen with new strategies. Targeting virulence factors necessary to induce host damage and disease is a new paradigm for antimicrobial therapy with several potential benefits that could lead to decreased resistance. BACKGROUND: The influence of metformin, N-acetylcysteine, and secnidazole on Klebsiella pneumoniae virulence factors production was tested. The production of Klebsiella pneumoniae virulence factors such as biofilm formation, urease, proteases, hemolysins, and tolerance to oxidative stress was evaluated phenotypically using sub-inhibitory concentration (1/8 MIC) of metformin, N-acetylcysteine, and secnidazole. For more confirmation, qRT-PCR was used to assess the relative expression level of rmpA, wcaG, fimH-1, mrkD, ureA, and khe genes regulating virulence factors production. RESULTS: Metformin, N-acetylcysteine, and secnidazole were all found to have a powerful inhibitory effect on the production of virulence factors phenotypically. Our results showed a significant reduction in the expression level of rmpA, wcaG, fimH-1, mrkD, ureA, and khe genes. Furthermore, the tested drugs were investigated in vivo to inform their ability to protect mice against Klebsiella pneumoniae pathogenesis. CONCLUSIONS: Metformin, N-acetylcysteine, and secnidazole inhibited the virulence of Klebsiella pneumoniae. Besides combating resistant Klebsiella pneumoniae, the tested drugs could also serve as an adjuvant to traditional antibiotics.

Efficacy and safety of intravenous fosfomycin for the treatment of carbapenem-resistant Klebsiella pneumoniae.

The aim of the study was to evaluate clinical and microbiological efficacy and safety of intravenous fosfomycin for the treatment of carbapenem-resistant K. pneumoniae infections. All adult inpatients receiving 48 h of intravenous fosfomycin, alone or combined with other antibiotics were included in the study. Overall favorable clinical response rate was 75.3% among 94 patients. Clinical response rates were 92.3%, 72.2% and 56.0% for urinary tract infections, bacteremia and pneumonia, respectively. Microbiological eradication was achieved in 55 of 86 patients. 30-day mortality was 33.0%. Adverse events were generally mild. Common adverse events were hypokalemia (37.2%) and hypernatremia (22.3%). Intravenous fosfomycin is an effective antibiotic option with a good safety profile for the treatment of carbapenem-resistant K. pneumoniae infections. The most favorable clinical and microbiological responses are obtained in urinary tract infections. The efficacy of the drug in more severe infections, such as pneumonia and bacteremia, is comparable to the literature.

Astragaloside IV alleviates lung inflammation in Klebsiella pneumonia rats by suppressing TGF-β1/Smad pathway

Astragaloside IV is a biologically active substance derived from the traditional Chinese medicine Astragalus mambranaceus Bunge, and has antioxidant, anti-inflammatory, and anti-apoptotic properties. In this study, we aimed to investigate the effects of astragaloside IV on Klebsiella pneumonia rats and the underlying mechanisms. Klebsiella pneumoniae (K. pneumoniae) rats were treated with different dosages of astragaloside IV (5, 10, and 20 mg/kg) by intragastric administration. The levels of pro-inflammatory cytokines interleukin (IL)-6, IL-1β, and tumor necrosis factor (TNF)-α in bronchoalveolar lavage fluid (BALF) were determined. Pathological changes of lung tissue were inspected by HE staining. The expression of transforming growth factor (TGF)-β1 in lung tissue was determined with immunohistochemistry, and the expression levels of TGF-β1, p-Smad2/Smad2, p-Smad3/Smad3, IκBα/p-IκBα, and p65/p-p65 in lung tissue were determined by western blot. The mechanism was further investigated with TGF-β1 inhibitor SB-431542. Astragaloside IV reduced the elevated levels of pro-inflammatory cytokines caused by K. pneumoniae and improved lung tissue damage in a dose-dependent manner. Astragaloside IV also decreased the expression of TGF-β1/Smad signaling pathway-related proteins and decreased the protein levels of inflammation-related p-IκBα and p65 in lung tissues induced by K. pneumoniae. Additionally, it was found that the effects of 20 mg/kg astragaloside IV were similar to SB-431542, which could improve pulmonary fibrosis induced by K. pneumoniae, decrease the levels of TGF-β1/Smad signaling pathway-related proteins in lung, and reduce inflammation at the same time. Astragaloside IV could alleviate the inflammation of rat pneumonia induced by K. pneumoniae through suppressing the TGF-β1/Smad pathway.

Combination of isothiocyanates and antibiotics increases susceptibility against Acinetobacter baumannii, Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis and Serratia marcescens.

BACKGROUND: The development and spread of multidrug-resistant organisms (MDRO) is evolving rapidly worldwide. Although effective antibiotics are still available, some infections are difficult to treat. Among MDROs, S. marcescens and A. baumannii are among the difficult-to-treat pathogens causing for instance sepsis and urinary tract infections (UTI). Isothiocyanates (ITC) are natural plant products. The antimicrobial properties of ITC appear to be more effective in combination with some antibiotics. PURPOSE: We investigated a mixture of ITC from nature-identical plant extracts of nasturtium and horseradish in different combined concentrations with broad-spectrum antibiotics against S. marcescens, A. baumannii, E. coli, K. pneumoniae and P. mirabilis. METHODS: First, we investigated the antibacterial activity of the compounds by standard agar disc diffusion test. Next, we evaluated the minimum inhibitory concentrations (MIC) via broth dilution tests. Checkerboard technique was used to assess antimicrobial effects against sulfamethoxazole-trimethoprim, ampicillin-sulbactam, nitrofurantoin, Fosfomycin, ciprofloxacin and imipenem combined with various concentrations of ITC. RESULTS: S. marcescens strains 1-3 showed reversal of resistance at >0.075 µg/mL ITC in combination with nitrofurantoin, whereas 0.05 µg/mL ITC increased antimicrobial susceptibility. Combination of fosfomycin with 0.003 µg/mL ITC resulted in increased efficacy against resistant S. marcescens strains, E. coli, K. pneumoniae and P. mirabilis. Remarkable additive antimicrobial activity was observed at 0.03 µg/mL and 0.06 µg/mL ITC in combination with 0.125 µg/mL imipenem (FIC > 0.5). CONCLUSION: The combination of ITC and antibiotics is a promising approach for the treatment of UTI caused by MDRO. The ITC combination with selected antibiotics had synergistic and additive effects.

Impact of Ceftazidime-Avibactam Treatment in the Emergence of Novel KPC Variants in the ST307-Klebsiella pneumoniae High-Risk Clone and Consequences for Their Routine Detection.

The emergence of Klebsiella pneumoniae isolates carrying novel blaKPC variants conferring ceftazidime-avibactam (CAZ/AVI) resistance is being increasingly reported. We evaluated the accuracy of phenotypic methods commonly used in routine clinical laboratories in the detection of novel K. pneumoniae carbapenemase (KPC) enzymes. Additionally, we characterized by whole-genome sequencing (WGS) the KPC-ST307-K. pneumoniae isolates recovered in our hospital before and after CAZ/AVI therapy. Rectal colonization or infection by carbapenem-resistant KPC-3 K. pneumoniae isolates (imipenem MIC, 16 mg/L; meropenem MIC, 8 to >16 mg/L) and CAZ/AVI-susceptible isolates (CAZ/AVI MIC, 1 to 2 mg/L) were first detected in three intensive care unit (ICU) patients admitted between March 2020 and July 2020. KPC K. pneumoniae isolates with increased CAZ/AVI MICs (8 to 32 mg/L) and carbapenem susceptibility (imipenem and meropenem MIC, <1 mg/L) were recovered within 6 to 24 days after CAZ/AVI treatment. WGS confirmed that all KPC K. pneumoniae isolates belonged to the sequence type 307 (ST307) high-risk clone and carried identical antimicrobial resistance genes and virulence factors. The presence of the novel blaKPC-46, blaKPC-66, and blaKPC-92 genes was confirmed in the K. pneumoniae isolates with increased CAZ/AVI MICs and restored carbapenem activity. KPC production was confirmed by immunochromatography, the eazyplex Superbug CRE system, and the Xpert Carba-R assay in all KPC K. pneumoniae isolates, but not in any isolate using chromogenic agar plates for carbapenemase producers (ChromID-CARBA), the KPC/MBL/OXA-48 Confirm kit, and the ß-CARBA test. Nevertheless, all grew in chromogenic agar plates for extended-spectrum ß-lactamase (ESBL) producers (ChromID-ESBL). We report the failure of the most common phenotypic methods used for the detection of novel KPC carbapenemases but not of rapid molecular or immunochromatography assays, thus highlighting their relevance in microbiology laboratories.

Breaking antimicrobial resistance by disrupting extracytoplasmic protein folding.

Antimicrobial resistance in Gram-negative bacteria is one of the greatest threats to global health. New antibacterial strategies are urgently needed, and the development of antibiotic adjuvants that either neutralize resistance proteins or compromise the integrity of the cell envelope is of ever-growing interest. Most available adjuvants are only effective against specific resistance proteins. Here, we demonstrate that disruption of cell envelope protein homeostasis simultaneously compromises several classes of resistance determinants. In particular, we find that impairing DsbA-mediated disulfide bond formation incapacitates diverse ß-lactamases and destabilizes mobile colistin resistance enzymes. Furthermore, we show that chemical inhibition of DsbA sensitizes multidrug-resistant clinical isolates to existing antibiotics and that the absence of DsbA, in combination with antibiotic treatment, substantially increases the survival of Galleria mellonella larvae infected with multidrug-resistant Pseudomonas aeruginosa. This work lays the foundation for the development of novel antibiotic adjuvants that function as broad-acting resistance breakers.

Antibiotics, like penicillin, are the foundation of modern medicine, but bacteria are evolving to resist their effects. Some of the most harmful pathogens belong to a group called the 'Gram-negative bacteria', which have an outer layer ­ called the cell envelope ­ that acts as a drug barrier. This envelope contains antibiotic resistance proteins that can deactivate or repel antibiotics or even pump them out of the cell once they get in. One way to tackle antibiotic resistance could be to stop these proteins from working. Proteins are long chains of building blocks called amino acids that fold into specific shapes. In order for a protein to perform its role correctly, it must fold in the right way. In bacteria, a protein called DsbA helps other proteins fold correctly by holding them in place and inserting links called disulfide bonds. It was unclear whether DsbA plays a role in the folding of antibiotic resistance proteins, but if it did, it might open up new ways to treat antibiotic resistant infections. To find out more, Furniss, Kaderabkova et al. collected the genes that code for several antibiotic resistance proteins and put them into Escherichia coli bacteria, which made the bacteria resistant to antibiotics. Furniss, Kaderabkova et al. then stopped the modified E. coli from making DsbA, which led to the antibiotic resistance proteins becoming unstable and breaking down because they could not fold correctly. Further experiments showed that blocking DsbA with a chemical inhibitor in other pathogenic species of Gram-negative bacteria made these bacteria more sensitive to antibiotics that they would normally resist. To demonstrate that using this approach could work to stop infections by these bacteria, Furniss, Kaderabkova et al. used Gram-negative bacteria that produced antibiotic resistance proteins but could not make DsbA to infect insect larvae. The larvae were then treated with antibiotics, which increased their survival rate, indicating that blocking DsbA may be a good approach to tackling antibiotic resistant bacteria. According to the World Health Organization, developing new treatments against Gram-negative bacteria is of critical importance, but the discovery of new drugs has ground to a halt. One way around this is to develop ways to make existing drugs work better. Making drugs that block DsbA could offer a way to treat resistant infections using existing antibiotics in the future.

Antibacterial effect of Rubus chingii flower extract against multidrug-resistant bacteria.

Rubus chingii is a well reputed member of Chinese traditional medicine system and is used for managing different ailments since historic times. The present report elucidates the growth impeding effect of R. chingii flower extract against multidrug resistant Escherichia coli, Klebsiella pneumoniae and Staphylococcus aureus. The extracts were prepared using standard Soxhlet extraction method using ethanol, methanol and acetone as a solvent. The extracts were further subjected to agar streak method and the stains that showed their sensitivity were further evaluated for minimum inhibitor concentration (MIC) assessment through TCC method. Subsequently the MIC was further used for well diffusion assay. All the strains used in the study showed their sensitivity towards R. chingii flowers extract in respective solvents. Highest antibacterial activity was seen against E. coli. and S. aureus whereas the lowest activity was recorded against K. pneumoniae. Thus the study reported herewith provided an insight into the antibacterial efficacy of R. chingii flower extract against MDR E. coli., S. aureus and K. pneumoniae.

Carbapenem-resistant K. pneumoniae exhibiting clinically undetected amikacin and meropenem heteroresistance leads to treatment failure in a murine model of infection.

Heteroresistance is a poorly understood mechanism of resistance which refers to a phenomenon where there are different subpopulations of seemingly isogenic bacteria which exhibit a range of susceptibilities to a particular antibiotic. In the current study, we identified a multidrug-resistant, carbapenemase-positive K. pneumoniae strain SWMUF35 which was classified as susceptible to amikacin and resistant to meropenem by clinical diagnostics yet harbored different subpopulations of phenotypically resistant cells, and has the ability to form biofilm. Population analysis profile (PAP) indicated that SWMUF35 showed heteroresistance towards amikacin and meropenem which was considered as co-heteroresistant K. pneumoniae strain. In vitro experiments such as dual PAP, dual Times-killing assays and checkerboard assay showed that antibiotic combination therapy (amikacin combined with meropenem) can effectively combat SWMUF35. Importantly, using an in vivo mouse model of peritonitis, we found that amikacin or meropenem monotherapy was unable to rescue mice infected with SWMUF35. Antibiotic combination therapy could be a rational strategy to use clinically approved antibiotics when monotherapy would fail. Furthermore, our data warn that antibiotic susceptibility testing results may be unreliable due to undetected heteroresistance which can lead to treatment failure and the detection of this phenotype is a prerequisite for a proper choice of antibiotic to support a successful treatment outcome.

Emergence of ceftazidime-avibactam resistance through distinct genomic adaptations in KPC-2-producing Klebsiella pneumoniae of sequence type 39 during treatment.

Three ceftazidime-avibactam-resistant KPC-2-producing Klebsiella pneumoniae strains of ST39 were isolated in Greece, from rectal swabs of three patients after 10-15 days of treatment. The patients were treated with ceftazidime-avibactam as monotherapy or in combination with colistin. Two of these strains harbored a D179Y or a D179V substitution in the Ω loop of KPC-2, corresponding to KPC-33, or to the novel KPC-57, respectively. The third strain had a 15 amino acid insertion after position 259 in the KPC-2, corresponding to KPC-44.

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.

In vitro and in vivo Antibacterial Activity of Cheilocostus speciosus Rhizome Extract on Resistant Bacteria.

BACKGROUND AND OBJECTIVE: Cheilocostus speciosus has traditionally been used in alternative medicine for different therapeutic purposes in different countries, including as an anti-infective agent. Antimicrobial properties of C. speciosus against standard bacterial strains have been reported before, however, complementary in vivo investigations, as well as, its antimicrobial activity against multi drug-resistant (MDR) bacteria are insufficient, if not lacking. In our study, in vitro and in vivo methods were used to test its antimicrobial activities on prominent clinical MDR isolates. MATERIALS AND METHODS: Cheilocostus speciosus rhizome extracts (CSRE) were prepared using different solvents; methanol, hexane, petroleum ether, ethylene glycol and water. The bactericidal activity of CSRE was tested on methicillin resistant S. aureus (MRSA), A. baumannii, K. pneumoniae serotype K2 (Kp K2), MDR P. aeruginosa, S. typhimurium and MDR E. coli. The standard disc diffusion and the broth micro-dilution methods were used to confirm the efficacy of CSRE against the tested microorganisms. In vitro results proved a potent bactericidal effect on MRSA and Kp K2 and a pronounced bacteriostatic effect against E. coli. RESULTS: We further confirmed the antibacterial activity of CSRE using BALB/c mice, animals were infected with Kp K2 or MRSA along with their standard strains; the extract was found to significantly reduce the bacterial load in mice lungs, liver and spleen. In addition, extracts were found to be more effective on the MDRs than the standard strains. CONCLUSION: It is concluded that CSRE could be a potential source for new antibiotics, further investigations are required to identify the bioactive components.

The new perspective of old antibiotic: In vitro antibacterial activity of TMP-SMZ against Klebsiella pneumoniae.

BACKGROUND/PURPOSE: Trimethoprim-sulfamethoxazole (TMP-SMZ) is broadly administered to treat multiple infections, and the paucity of effective treatment alternatives for infections caused by Klebsiella pneumoniae has led to a renewed interest in TMP-SMZ. The aim of this study is to evaluate the antibacterial efficacy of TMP-SMZ against K. pneumoniae. METHODS: The resistance genes of K. pneumoniae clinical isolates were investigated by PCR, followed by conjugation experiments and multilocus sequence typing. RESULTS: The resistance rate of K. pneumoniae to TMP-SMZ decreased over the collection period from 26.7% (88/330) to 16.9% (56/332). The high carrying rates (173/175, 98.9%) of resistance determinants (sul genes or dfr genes) were the main mechanisms of TMP-SMZ resistance isolates, with sul1 (142/175, 81.1%) and dfrA1 (119/175, 68.0%). Only class 1 integron was detected, the prevalence of which in TMP-SMZ resistant K. pneumoniae was 63.4% (111/175). CONCLUSION: These results provided insights into the antimicrobial efficacy of TMP-SMZ against K. pneumoniae, also illustrating the wide distribution of SMZ and TMP resistance genes among resistant K. pneumoniae. Simultaneously, the present study highlights the significance of reasonable administration and effective continued monitoring.

Emergence of colistin resistance during treatment of recurrent pneumonia caused by carbapenemase producing Klebsiella pneumoniae.

A 60-year-old woman received meropenem/colistin treatment for bilateral pneumonia caused by a ST15 carbapenemase producing Klebsiella pneumoniae. The patient recovered but re-infection with the same (ST15), but now colistin-resistant K. pneumoniae, occurred. The molecular mechanism of the emerged colistin resistance was identified as mgrB gene modification by insertion element (IS) IS903B.

Biologically Synthesized Silver Nanoparticles for Enhancing Tetracycline Activity Against Staphylococcus aureus and Klebsiella pneumoniae

Abstract Phytochemical content of plant extracts can be used effectively to reduce the metal ions to nanoparticles in one-step green synthesis process. In this study, six plant extracts were used for the synthesis of silver nanoparticles (AgNPs). Biologically synthesized AgNPs was characterized using UV-Vis Spectrophotometer, Field Emission Scanning Electron Microscope (FE-SEM), X-ray diffraction (XRD), Energy Dispersive X-ray spectroscopy (EDX) and Fourier Transform Infrared (FTIR) spectroscopy. The individual and combined effects of AgNPs and tetracycline against S. aureus and K. pneumoniae were assessed. Ginger, onion and sidr extracts supported AgNPs formation while arak, garlic and mint extracts failed to convert the silver ions to AgNPs. The present findings revealed significant differences between the tested plant extracts in supporting AgNPs synthesis. AgNPs synthesized by ginger showed the highest individual and combined activity against tested strains followed by AgNPs prepared by sidr then that synthesized by onion. AgNPs significantly enhanced tetracycline activity (p≤0.05) against S. aureus and K. pneumoniae. The results of this study demonstrated that the combination of tetracycline and biologically synthesized AgNPs presented a useful therapeutically method for the treatment of bacterial infection and counterattacking bacterial resistance.

RS sample: Can be guide for empirical treatment of haematological malignancy patients?

Neutropenia due to intensive chemotherapy in haematological malignancy patients leaves the host vulnerable and makes them susceptible to infections. Infections are the most important cause of morbidity and mortality especially in haematological malignancy and chemotherapy patients. In addition, the use of multiple or inappropriate antibiotics leads to the development of resistant microorganisms. Therefore, the choice of empirical treatment is of vital important in these patient groups. Escherichia coli, Acinetobacter baumannii and Klebsiella pneumoniae are among the most frequently isolated Gram negative bacteria in neutropenic patients. Rectal swab (RS) samples were obtained from haematological malignancy patients not yet on chemotherapy or have no infection on chemotherapy period, E. coli was isolated from these samples, and A. baumannii and K. pneumoniae colonization were investigated. Susceptibilities of bacteria against antibiotics used in empirical treatment and prophylaxis were determined by using Gradient test strips according to the EUCAST recommendation. All isolates were sensitive against colistin. The resistant rates of antibiotics were detected as 39.1%, 9.4%, 6.8%, 35.1%, 31%, 39.1% for ciprofloxacin, meropenem, imipenem, piperacillin-tazobactam, cefepime, ceftazidime respectively The clonal relationship between Gram negative bacteria of intestinal flora and infection agents of same patient was investigated by Pulsed-Field gel electrophoresis. Twenty-three of the 30 patients (76.6%) were found to have a clonal relationship between the bacterial isolates before and after infection. It was determined that it can be able to predict with RS samples about possible agents of infection and their antibiotic susceptibility patterns.

Intra-hospital differences in antibiotic use correlate with antimicrobial resistance rate in Escherichia coli and Klebsiella pneumoniae: a retrospective observational study.

Background: Monitoring antimicrobial use and resistance in hospitals are important tools of antimicrobial stewardship programs. We aimed to determine the association between the use of frequently prescribed antibiotics and the corresponding resistance rates in Escherichia coli and Klebsiella pneumoniae among the clinical departments of a tertiary care hospital. Methods: We performed a retrospective observational study to analyse the use of nine frequently prescribed antibiotics and the corresponding antimicrobial resistance rates in hospital acquired E. coli and K. pneumoniae isolates from 18 departments of our institution over 9 years (2008-2016). The main cross-sectional analysis assessed the hypothetical influence of antibiotic consumption on resistance by mixed logistic regression models. Results: We found an association between antibiotic use and resistance rates in E. coli for amoxicillin-clavulanic acid (OR per each step of 5 defined daily dose/100 bed-days 1.07, 95% CI 1.02-1.12; p = 0.004), piperacillin-tazobactam (OR 2.11, 95% CI 1.45-3.07; p < 0.001), quinolones (OR 1.52, 95% CI 1.25-1.86; p < 0.001) and trimethoprim-sulfamethoxazole (OR 1.59, 95% CI 1.19-2.13; p = 0.002). Additionally, we found a significant association when all nine antibiotics were combined in one analysis. The association between consumption and resistance rates was stronger for nosocomial than for community strains. In K. pneumoniae, we found an association for amoxicillin-clavulanic acid (OR 1.07, 95% CI 1.01-1.14; p = 0.025) and for trimethoprim-sulfamethoxazole (OR 2.02, 95% CI 1.44-2.84; p < 0.001). The combined analysis did not show an association between consumption and resistance (OR 1.06, 95% CI 0.99-1.14; p = 0.07). Conclusions: We documented an association between antibiotic use and resistance rate for amoxicillin-clavulanic acid, piperacillin-tazobactam, quinolones and trimethoprim-sulfamethoxazole in E. coli and for amoxicillin-clavulanic acid and trimethoprim-sulfamethoxazole in K. pneumoniae across different hospital departments. Our data will support stewardship interventions to optimize antibiotic prescribing at a department level.

Could Frequent Carbapenem Use Be a Risk Factor for Colistin Resistance?

AIMS: The antibiotic colistin, which had been previously abandoned, is being brought back as a last line of defense against bacterial infection. However, colistin resistance was reported shortly after its reintroduction. This study evaluated the risk factors for colonization/infections due to colistin-resistant Acinetobacter baumannii (ColR-Ab) and Klebsiella pneumoniae (ColR-Kp) strains and characterized the molecular epidemiology of these two strains. RESULTS: Age, previous hospitalization duration, and previous use of carbapenem and colistin were risk factors for ColR-Kp, whereas previous use of carbapenem and colistin was a risk factor for ColR-Ab. According to pulsed-field gel electrophoresis analysis, most ColR-Kp strains could be grouped into two major pulsotypes. This appears to be an indicator of cross contamination of ColR-Kp strain, since different isolates appeared to be belonging to the same clones. The existence of colistin-susceptible (ColS) and colistin-resistant (ColR) strains in the same pulsotypes might also be an indicator of the recent emergence of resistance mechanisms. CONCLUSIONS: The results highlight the emergence of ColR pathogens in Turkey, which is considered to be developing country, and that carbapenem use coupled with insufficient infection control measures might increase the risk of ColR outbreaks.