Multiresistant Bacterial Strains Research Articles

Urinary tract infections in children with cancer and febrile neutropenia - single center experience

Background/Aim. Urinary tract infection (UTI) in children with febrile neutropenia (FN) after receiving chemotherapy could be followed by atypical symptoms and signs. The absence of routine urine culture (UC) sampling for analysis could lead to undiagnosed disease and inadequate treatment of these patients. The aim of the study was to indicate the importance of sampling UC in children who have developed FN and to point out the most probable causative agents of UTI in children with FN and antibiotic sensitivity/resistance of the isolated strains. Methods. During a five-year observation period, 40 UTIs were registered in 30 patients with FN. In the study group of patients with FN, the number of UTIs, the number of recurrent UTIs, isolated pathogens, their sensitivity to antibiotics, characteristics of urine sediment, the presence of localized symptoms of UTI, and the presence of urosepsis were analyzed. The obtained results were compared with the control group which consisted of children who were healthy prior to hospitalization due to febrile urinary infection. Results. When compared to the control group, significant differences in the presence of symptoms of UTI and urine sediment findings in patients with FN were observed. A higher percentage of resistant strains of Escherichia coli isolated from UC of cancer patients with FN was noted when compared to the control group. Three UTI cases were followed by urosepsis. Conclusion. UC findings are important not only in establishing the diagnosis of UTI and detecting multi-resistant bacterial strains but also in choosing appropriate antibiotics and selecting a subgroup of patients with recurrent UTI who require further monitoring and detecting potential complications in a timely manner.

New lignan glycosides from Justicia secunda Vahl (Acanthaceae) with antimicrobial and antiparasitic properties

Three new lignan glucosides, namely, justisecundosides A (1), B (2a), and C (2b), were isolated from the whole plant of Justicia secunda together with seven known compounds (3−9). Their structures were established based on a comprehensive analysis of HR-ESI-MS, IR, UV, and CD, in conjunction with their 1D and 2D-NMR data. A putative biogenetic pathway of compounds 1−2a,b from coniferyl alcohol was proposed. In addition, the antimicrobial activities of the extract, fractions, and some isolated compounds were assessed against multiresistant bacterial and fungal strains. Furthermore, the antiplasmodial, antileishmanial, and antitrypanosomal activities were assessed against the sensitive (3D7) and multidrug-resistant (Dd2) strains of P. falciparum, promastigote and bloodstream forms of L. donovani, and Trypanosoma brucei, respectively. Compound 4 exhibited moderate antibacterial activity against Staphylococcus aureus SA RN 46003 with a MIC value of 62.5 μg/mL. Besides, compound 6 demonstrated a very good activity against sensitive (IC50Pf3D7: 0.81 μg/mL) and multidrug-resistant (IC50PfDd2: 14.61 μg/mL) strains of P. falciparum while compound 4 displayed good antitrypanosomal activity (IC50: 1.19 μg/mL). Also, compound 1 was the most active on the promastigote form of L. donovani with an IC50 of 13.02 μg/mL.

Investigation of the Efficacy Results of Atmospheric Cold Plasma Against Multi-Resistant Bacterial Strains

Giriş: Amacımız Atmosferik Soğuk Plazma ile muamele edilmiş PBS'nin Gram pozitif ve Gram negatif çoklu ilaca dirençli bakterilere karşı etkinliğini araştırmaktır.
 Gereç ve Yöntemler: Toplam 50 karbapenem dirençli Klebsiella pneumoniae ve 10 vankomisin dirençli Enterococcus faecium suşu çalışmaya dahil edilmiştir. 100 µl bakteri süspansiyonu (107 CFU/ml) üzerine 100 µl (1/2), 300 µl (3/4), 700 µl (7/8), 1500 µl (15/16), 3100 µl (31/32), 6300 µl ACP ile muamele edilmiş PBS eklenmiştir. Süspansiyon pipetlendikten sonra oda sıcaklığında 30 dakika inkübe edilmiş, koyun kanlı agara ekilmiş ve 37°C'de bir gece (16-18 saat) inkübe edilmiştir.
 Bulgular: Çalışılan tüm suşlar ASP ile muamele edilmiş PBS çözeltisi tarafından inhibe edilmiştir. Verilen dilüsyonlar bakteri çoğalmasının tamamen inhibe olduğu dilüsyonlardır. K. pneumoniae suşlarının 45'i ACP ile muamele edilmiş PBS çözeltisi ile 3/4 konsantrasyonda tamamen inhibe olurken, K. pneumoniae suşlarının 5'i ACP ile muamele edilmiş PBS çözeltisi ile 7/8 konsantrasyonda tamamen inhibe olmuştur. Vankomisine dirençli E. faecium suşları, K. pneumonia suşlarına göre daha yüksek miktarlarda plazma ile inhibe edilmiştir. E. faecium suşlarından üçü (15/16), E. faecium suşlarından üçü (31/32), E. faecium suşlarından dördü (63/64) ACP ile muamele edilmiş PBS solüsyonu tarafından tamamen inhibe edilmiştir.
 Sonuç: ACP ile muamele edilmiş PBS çözeltisinin önemli antibiyotiklere dirençli hem Gram-pozitif hem de Gram-negatif bakterilere karşı etkili olduğu bulunmuştur. Seçilen Gram-negatif ve Gram-pozitif bakterilerde inaktivasyon için gereken ASP ile muamele edilmiş PBS konsantrasyonunda farklılıklar gözlenmiştir. Bununla birlikte, hem Gram-negatif hem de Gram-pozitif enfeksiyonlarda mevcut tedavi seçenekleri gün geçtikçe azaldığı için bu yöntem umut vericidir. ASP ile muamele edilmiş PBS sıvılarının bir tedavi yöntemi olarak kullanılması için ileri çalışmalara ihtiyaç vardır.

Summary of the conference "Phages and phage therapy: from Félix d'Hérelle to 2.0 phages"

As part of the 25th edition of the Francophone Virology Days, Pr. Frédéric Laurent held the conference "Phages and phage therapy: from Félix d'Hérelle to 2.0 phages". Frédéric Laurent detailed the history of phages: from their discovery and their first use in early 1920s, through their abandonment in Western world in the 1940s in favor of antibiotics, then their reappearance in recent years within the context of the emergence of multi-resistant bacterial strains. Throughout this presentation, Pr.Laurent also detailed general functioning of phages, their chain of bioproduction and quality control, the progress to be made in the compassionate treatment of patients in therapeutic failures.

Investigation of some basil genotypes in terms of their effect on bacterial communication system, and antimicrobial activity

The exponential growth of multiresistant bacterial strains creates the need to explore new or combined strategies to combat bacterial resistance. Medicinal plant-derived compounds against pathogenic bacteria may provide new, simple approaches to developing more environmentally friendly antimicrobial agents. Many researchers focus on exploring novel or combined strategies for combating bacterial resistance. Aromatic plants containing essential oils, such as basil, are often used as therapeutic agents in the pharmaceutical industry. Recent research has shown that basil is effective against certain harmful food phytopathogenic bacteria and has antimicrobial and anti-quorum sensing properties, which were investigated in this study. Our results have shown that the essential oil and ethanol extract of basil exhibits both antibacterial activity and anti-quorum sensing activity against some Gram-negative and Gram-positive bacterial species. It has also been found to have antifungal effects on C. albicans. Among the tested microorganisms, the genotypes of PI 531396, PI 296390, PI 414199, PI 253157, PI 296391, PI 652071, midnight, and Dino cultivars have been found to be more effective than other genotypes. The highest effect on quorum sensing system was found in Moonlight and Dino cultivars, PI 296391, PI 414199, PI 652070, PI 172997 and PI 190100 genotypes. Dendrogram analysis has shown that there is a relationship between different genotypes depending on microorganisms and anti-quorum sensing activity. Ames 29184, PI 207498, and PI 379412 genotypes were in the same group. Biplot analyses were performed to determine the relationship between the studied properties, and the results showed that more than 47% of the total variation was in all forms.

Chromobacterium Violaceum: A Model for Evaluating the Anti-Quorum Sensing Activities of Plant Substances

In the new antibiotic era, the exponential increase in multiresistant bacterial strains has become the main global health problem. Many researchers have focused their efforts on exploring novel or combined strategies for combating bacterial resistance. Good knowledge of the molecular mechanisms of resistance and bacterial virulence factors as key targets provides us with a good basis for resolving the problem. One particularly attractive and promising strategy is to attack the main regulatory “network” of bacterial virulence determinants known as quorum sensing (QS). The inhibition of QS signals will be a novel means of screening more effective quorum-sensing inhibitors (QSIs) and will play a key role in the use of next-generation antimicrobials in the battle against resistance. This motivated the present review to provide a comprehensive clarification of the regulatory mechanisms of quorum-sensing signaling pathways in Chromobacterium violaceum and the discovery of potential plant quorum-sensing inhibitors.

Synthetic Star Nanoengineered Antimicrobial Polymers as Antibiofilm Agents: Bacterial Membrane Disruption and Cell Aggregation.

Antimicrobial resistance has become a worldwide issue, with multiresistant bacterial strains emerging at an alarming rate. Multivalent antimicrobial polymer architectures such as bottle brush or star polymers have shown great potential, as they could lead to enhanced binding and interaction with the bacterial cell membrane. In this study, a library of amphiphilic star copolymers and their linear copolymer equivalents, based on acrylamide monomers, were synthesized via RAFT polymerization. Their monomer distribution and molecular weight were varied. Subsequently, their antimicrobial activity toward a Gram-negative bacterium (Pseudomonas aeruginosa PA14) and a Gram-positive bacterium (Staphylococcus aureus USA300) and their hemocompatibility were investigated. The statistical star copolymer, S-SP25, showed an improved antimicrobial activity compared to its linear equivalent againstP. aeruginosaPA14. The star architecture enhanced its antimicrobial activity, causing bacterial cell aggregation, as revealed via electron microscopy. However, it also induced increased red blood cell aggregation compared to its linear equivalents. Changing/shifting the position of the cationic block to the core of the structure prevents the cell aggregation effect while maintaining a potent antimicrobial activity for the smallest star copolymer. Finally, this compound showed antibiofilm properties against a robust in vitro biofilm model.

Multicationic Quaternary Ammonium Compounds: A Framework for Combating Bacterial Resistance.

During previous stages of research, high biocidal activity toward microorganism archival strains has been used as the main indicator in the development of new antiseptic formulations. Although this factor remains one of the most important characteristics of biocide efficiency, the scale of antimicrobial resistance spread causes serious concern. Therefore, focus shifts toward the development of formulations with a stable effect even in the case of prolonged contact with pathogens. Here, we introduce an original isocyanuric acid alkylation method with the use of available alkyl dichlorides, which opened access to a wide panel of multi-QACs with alkyl chains of various lengths between the nitrogen atoms of triazine and pyridine cycles. We used a complex approach for the resulting series of 17 compounds, including their antibiofilm properties, bacterial tolerance development, and antimicrobial activity toward multiresistant pathogenic strains. As a result of these efforts, available compounds have shown higher levels of antibacterial activity against ESKAPE pathogens than widely used commercial QACs. Hit compounds possessed high activity toward clinical bacterial strains and have also demonstrated a long-term biocidal effect without significant development of microorganism tolerance. The overall results indicated a high level of antibacterial activity and the broad application prospects of multi-QACs based on isocyanuric acid against multiresistant bacterial strains.

In Vitro Activity of Cefiderocol on Multiresistant Bacterial Strains and Genomic Analysis of Two Cefiderocol Resistant Strains.

Cefiderocol is a new siderophore cephalosporin that is effective against multidrug-resistant Gram-negative bacteria, including carbapenem-resistant strains. The aim of this study was to evaluate the activity of this new antimicrobial agent against a collection of pathogens using broth microdilution assays and to analyze the possible mechanism of cefiderocol resistance in two resistant Klebsiella pneumoniae isolates. One hundred and ten isolates were tested, comprising 67 Enterobacterales, two Acinetobacter baumannii, one Achromobacter xylosoxidans, 33 Pseudomonas aeruginosa and seven Stenotrophomonas maltophilia. Cefiderocol showed good in vitro activity, with an MIC < 2 μg/mL, and was able to inhibit 94% of the tested isolates. We observed a resistance rate of 6%. The resistant isolates consisted of six Klebsiella pneumoniae and one Escherichia coli, leading to a resistance rate of 10.4% among the Enterobacterales. Whole-genome sequencing analysis was performed on two cefiderocol-resistant Klebsiella pneumoniae isolates to investigate the possible mutations responsible for the observed resistance. Both strains belonged to ST383 and harbored different resistant and virulence genes. The analysis of genes involved in iron uptake and transport showed the presence of different mutations located in fhuA, fepA, iutA, cirA, sitC, apbC, fepG, fepC, fetB, yicI, yicJ, and yicL. Furthermore, for the first time, to the best of our knowledge, we described two Klebsiella pneumoniae isolates that synthesize a truncated fecA protein due to the transition from G to A, leading to a premature stop codon in the amino acid position 569, and a TonB protein carrying a 4-amino acid insertion (PKPK) after Lysine 103. In conclusion, our data show that cefiderocol is an effective drug against multidrug-resistant Gram-negative bacteria. However, the higher resistance rate observed in Enterobacterales underlines the need for active surveillance to limit the spread of these pathogens and to avoid the risks associated with the emergence of resistance to new drugs.

Ultra-Small Silver Nanoparticles: A Sustainable Green Synthesis Approach for Antibacterial Activity

The present study centers on the synthesis of ultra-small silver nanoparticles (AgNPs) with antibacterial properties using citrus peel residues (orange, lemon, and grapefruit) as reducing and stabilizing agents, and on assessing their antibacterial activity against multidrug-resistant clinical Staphylococcus aureus. The synthesized AgNPs were analyzed by various techniques, including UV-Vis spectroscopy, SAED, TEM, XRD, FTIR, and Raman. The results demonstrate the formation of ultra-small, monodisperse, quasi-spherical AgNPs with an average particle size of 2.42 nm for AgNPs produced with mixed extracts. XRD analysis indicated that the AgNPs have a crystal size of 9.71 to 16.23 nm. The AgNPs exhibited potent inhibitory activity against resistant S. aureus, with a minimum inhibitory concentration (MIC) of 15.625 to 62.50 ppm. The findings suggest that the ultra-small nanometer size of the AgNPs could be attributed to the synthesis method that employs ambient conditions and the presence of polyphenolic compounds from citrus peel. Consequently, AgNPs obtained through sustainable green synthesis hold significant potential in combating clinical multi-resistant bacterial strains that are challenging to treat and eradicate. This approach also contributes to the revaluation of citrus residues in the region, which is an ongoing environmental issue today.

Antibacterial Activity of Calycophyllum spruceanum Leaf Extract against Enterococcus faecalis Strains “In vitro” for Endodontic Purposes

Aims: The indiscriminate use of antimicrobials contributed to the selection of multiresistant bacterial strains, mainly Enterococcus faecalis, leading to the search for new strategies for these infections, requiring the identification of new bioactive compounds from medicinal plants, an example is C. spruceanum used in traditional communities in the Amazon.&#x0D; In this sense, this study aimed to evaluate the antibacterial activity of C. spruceanum leaf extract against E. faecalis "in vitro" for endodontic purposes.&#x0D; Place and Duration of Study: Sample: the study was carried out at the microbiology laboratory of the Federal University of Acre (UFAC), in the city of Rio Branco, state of Acre, Brazil, from July 2021 to January 2022.&#x0D; Methodology: For this study, 50mg/mL of the crude extract of C. spruceanum leaf was diluted in Dimethylsulfoxide, as well as 50mg/mL of the extract with 1000mg of calcium hydroxide and 1000mg of calcium hydroxide in 1mL of distilled water. After preparing the extracts, 20µL were deposited in the wells made on Müeler-Hinton agar medium seeded with E. faecalis, incubated for 24 hours at 37°C. After this period, the positive activity of the extracts was obtained from the formation of the inhibition halo in millimeters.&#x0D; Results: The best results were for extract associated with calcium hydroxide (20mm), followed by calcium hydroxide solution (17.67mm) and with lower activity, C. spruceanum extract (14.33mm). The best results of the Minimum Inhibitory Concentration with values ​​of 6.25 mg/mL for the extract combined with calcium hydroxide and Minimum Bactericidal Concentration that was 25mg/mL for the association of the extract with calcium hydroxide.&#x0D; Conclusion: The C. spruceanum extract has antibacterial activity against E. faecalis and its association with calcium hydroxide potentiated its effect.

Bacteriological profile and antibiotic susceptibility of bacteria isolated from diabetic foot ulcers at the National Hospital of Niamey

Objective: The objective of our work was to determine the bacteriological profile and antibiotic sensitivity of bacteria isolated from diabetic foot wounds. Methods: We conducted a descriptive cross-sectional study from July 1 to December 31, 2020. During this period, all diabetic patients with wounds were sampled. The different samples were plated on appropriate media. The identification of the isolated bacterial strains as well as the study of their sensitivity to antibiotics was performed according to conventional methods. Results: A total of 689 diabetic patients were followed during this period, 58 (8.41%) had infected foot wounds. The average age was 53.6 years with a sex ratio (M/F) of 1.15. Bacteriological analyses allowed the isolation of 48 bacterial strains (10 different species) with a predominance of Staphylococcus aureus (35.42%), followed by Klebsiella pneumoniae (20.84%), Escherichia coli (12.50%), Enterobacter aerogenes (10.42%). We observed a predominance of Gram-negative bacilli (56.25%). The sensitivity tests performed on the identified bacteria showed that 100% of the enterobacteria strains were sensitive to Ertapenem and Imipenem, except for Proteus mirabilis. Four strains were tested for extended-spectrum betalactamase (ESBL) and none were producers. All Gram positive cocci isolates were sensitive to vancomycin and resistant to penicillin G. Staphylococcus aureus strains were sensitive to erythromycin (82.35%), Kanamycin (82.35%) and Oxacillin (82.35%). Conclusion: These results show that diabetic foot wound infections are becoming more frequent. It is necessary to manage them with adequate antibiotic therapy based on an antibiogram to avoid the spread of multi-resistant bacterial strains.

Prevalence and Characterisation of Multiresistant Bacterial Strains Isolated in Pigs from the Island of Tenerife.

Background: Antibiotic-resistant bacteria can circulate among human and animal populations through direct contact with animals, as well as via food and the environment. The purpose of this study was to examine the prevalence and characterisation of multiresistant bacteria in pig samples. Methods: 224 samples of pig livestock were taken at the slaughterhouse on the island of Tenerife. A nasal and a rectal sample were collected from each pig. The presence of methicillin-resistant Staphylococcus aureus (MRSA), methicillin-resistant Staphylococcus coagulase-negative (MRCoNS), vancomycin-resistant Enterococcus (VRE), extended-spectrum ß-lactamase-producing Enterobacteriaceae (BLEE), carbapenemase-producing Enterobacteriaceae (CPE), and colistin-resistant Enterobacteriaceae was investigated. The resistance genes of the isolated bacteria were characterised by specific PCRs depending on the microorganism to be studied, and in vitro antimicrobial resistance was determined using the broth microdilution method (Vitek®2 system bioMérieux®, Nurtingen, Germany). Results: MRSA prevalence was 73.21% (164 isolates). MRCoNS prevalence was 9.8% (22 isolates), S. sciuri being the prevalent species. Six isolates presented a 2.7% prevalence of extended-spectrum ß-lactamase-producing Escherichia coli (BLEE) in the CTX-M-1 group. No vancomycin-resistant Enterococcus (VRE), carbapenemase-producing Enterobacteriaceae (CRE), or colistin-resistant Enterobacteriaceae were isolated. Conclusion: we found a high presence of multiresistant bacteria, suggesting the need for increased control and surveillance of this type of strains in pig livestock and a better understanding of the possible transmission routes of these microorganisms through livestock products.

Adenanthin Is an Efficient Inhibitor of Peroxiredoxins from Pathogens, Inhibits Bacterial Growth, and Potentiates Antibiotic Activities.

The emergence and re-emergence of bacterial strains resistant to multiple drugs represent a global health threat, and the search for novel biological targets is a worldwide concern. AhpC are enzymes involved in bacterial redox homeostasis by metabolizing diverse kinds of hydroperoxides. In pathogenic bacteria, AhpC are related to several functions, as some isoforms are characterized as virulence factors. However, no inhibitor has been systematically evaluated to date. Here we show that the natural ent-kaurane Adenanthin (Adn) efficiently inhibits AhpC and molecular interactions were explored by computer assisted simulations. Additionally, Adn interferes with growth and potentializes the effect of antibiotics (kanamycin and PMBN), positioning Adn as a promising compound to treat infections caused by multiresistant bacterial strains.

Antibiotic resistance profile of Enterococcus spp. strains isolated from the intestinal tract at the Yaounde Military Hospital Laboratory

Multidrug-resistant Enterococci colonizing the intestinal tract of patients are the major sources of infection as well as the spread of resistance. The present study aims to determine the antimicrobial resistance profile of Enterococcus species from the intestinal tract of patients admitted to the laboratory of the Yaounde Military Hospital. The study was conducted in patients from July to November 2020. Stool samples were collected and processed for bacterial isolation and antimicrobial susceptibility testing. Stool samples were inoculated onto selective Enterococci media (Bile Esculin azide agar). The isolates obtained were identified to the level of genus and species level: characteristics, Gram staining and use of API 20 Streptococcus system. Susceptibility testing was performed using the Kirby-Bauer solid state disk diffusion method. Of the 35 samples analyzed 19 strains were isolated, 9 Enterococci and 10 non-Enterococci. Enterococci were isolated from 9 (25.7%) of the study subjects. The isolates were Enterococcus faecium (36.9%) followed by Enterococcus faecalis (10.5%), Aerococcus viridans (31.5%), Streptococcus mitis 1 (10.5%) and finally Streptococcus mitis 2 (10.5%). Of the 9 Enterococci isolates tested, 6 (66.6%) were resistant to Ampicillin, 9 (100%) to Gentamycin and 4 (44.4%) to Amikacin. Other alternative antibiotics to treat infection that may be caused by Enterococci have also shown a high rate of resistance in vitro: levofloxacin 6 (66.6%), erythromycin 8 (88.8%), tetracycline 7 (77.7%), chloramphenicol 4 (44.4%). 7 (77.7%) of the Enterococci were resistant to vancomycin. Multidrug resistance was predominant in E. faecium up to R7 (10.5%), however multi resistance was more pronounced at R3 (94.73%). This study reveals a high rate of faecal colonization by multidrug-resistant Enterococci and an increasing prevalence of strains resistant to vancomycin. Thus, periodic monitoring of antibacterial susceptibilities is recommended to detect emerging resistance and prevent the spread of multi-resistant bacterial strains.

Icariin in Combination with Amoxycillin-Clavulanate and Ampicillin, but Not Vancomycin, Increases Antibiotic Sensitivity and Growth Inhibition against Methicillin-Resistant Staphylococcus aureus.

The widespread irrational use of antibiotics in recent years has resulted in an increase in the detection of multi-resistant bacterial strains, particularly methicillin-resistant Staphylococcus aureus (MRSA). The use of natural derivatives such as flavonoids is postulated as one of the most promising avenues to solve this emerging public health problem. The objective of the present study is to characterize the antimicrobial activity of icariin, a flavonoid compound isolated from a variety of plants of the Epimedium genus, against human and animal clinical MRSA isolates. Our study found that icariin alone did not have any antimicrobial effect on S. aureus or MRSA clinical isolates. However, icariin enhanced the effect of amoxycillin-clavulanate or ampicillin, whereas no effect was seen when used in combination with vancomycin. Specifically, co-incubation of S. aureus with amoxycillin-clavulanate plus icariin resulted in an increased proportion of dead cells, suggesting that this flavonoid potentially increases antimicrobial activity when used in combination with the beta-lactam antibiotic amoxycillin-clavulanate. Furthermore, we demonstrate that co-incubation of S. aureus with AmoxyClav plus icariin resulted in increased membrane disruption and growth inhibition. This study demonstrates the potential utility of icariin in permitting lower antibiotic therapeutic doses in alignment with strategies to reduce the spread of antibiotic resistance. Further research is required to determine the optimum concentration of icariin and to define clinically relevant combinations of flavonoid and antibiotic.

Alternative ecological strategies used in the prevention and treatment of infections produced by antibotic multiresistant bacterial strains

Alternative ecological strategies used in the prevention and treatment of infections produced by antibotic multiresistant bacterial strains

Evaluation of the antibacterial and modulatory activities of ethanolic excract of Calotropis procera (Aiton) W.T. Aiton against multiresistant bacterial strains

The objective of this study was to evaluate the antibacterial and modulatory activities of ethanolic extract of Calotropis procera (Aiton) W.T. Aiton against resistant species. By microdilution method, the minimum inhibitory concentration (MIC) of the extract and modulation of the subinhibitory concentration MIC/8 to norfloxacine, gentamicin and imipenem against Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. There was obtained 512 μg/mL to Pseudomonas aeruginosa. To Staphylococcus aureus, modulation showed synergism to norfloxacin and gentamicin, with imipenem against Pseudomonas aeruginosa and gentamicin against Escherichia coli. Based on these results, more studies are needed to test the antibacterial activity of the extract. El objetivo de este estudio fue evaluar la actividad antibacteriana y moduladora del extracto etanólico de Calotropis procera (Aiton) W.T. Aiton contra cepas multirresistentes de bacterias. Por el método de microdilución, fueron definidas la concentración inhibidora mínima (MIC) del extracto y la modulación con la concentración inhibidora CIM / 8 del extracto con norfloxacina, gentamicina e imipenem contra Staphylococcus aureus, Escherichia coli y Pseudomonas aeruginosa. Se obtuvo 512 μg/mL para Pseudomonas aeruginosa. Se descubrió sinergismo en el caso de Staphylococcus aureus, en la modulación con norfloxacina y gentamicina, mientras que con imipenem frente a Pseudomonas aeruginosa y con gentamicina para Escherichia coli. Con base en estos resultados, se necesitan más estudios para probar la actividad antibacteriana del extracto.

Enhancement of Antibiotic Activity by 1,8-Naphthyridine Derivatives against Multi-Resistant Bacterial Strains.

The search for new antibacterial agents has become urgent due to the exponential growth of bacterial resistance to antibiotics. Nitrogen-containing heterocycles such as 1,8-naphthyridine derivatives have been shown to have excellent antimicrobial properties. Therefore, the purpose of this study was to evaluate the antibacterial and antibiotic-modulating activities of 1,8-naphthyridine derivatives against multi-resistant bacterial strains. The broth microdilution method was used to determine the minimum inhibitory concentration (MIC) of the following compounds: 7-acetamido-1,8-naphthyridin-4(1H)-one and 3-trifluoromethyl-N-(5-chloro-1,8-naphthyridin-2-yl)-benzenesulfonamide. The antibiotic-modulating activity was analyzed using subinhibitory concentrations (MIC/8) of these compounds in combination with norfloxacin, ofloxacin, and lomefloxacin. Multi-resistant strains of Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus were used in both tests. Although the compounds had no direct antibacterial activity (MIC ≥ 1.024 µg/mL), they could decrease the MIC of these fluoroquinolones, indicating synergism was obtained from the association of the compounds. These results suggest the existence of a structure–activity relationship in this group of compounds with regard to the modulation of antibiotic activity. Therefore, we conclude that 1,8-naphthyridine derivatives potentiate the activity of fluoroquinolone antibiotics against multi-resistant bacterial strains, and thereby interesting candidates for the development of drugs against bacterial infections caused by multidrug resistant strains.

Modulating antibacterial activity against multidrugresistant Escherichia coli and Staphylococcus aureus of the flavonoid pectolinarin isolated from Lantana camara leaves

The antibiotic potentiating activity against standard and multidrug-resistant Escherichia coli and Staphylococcus aureus bacterial strains of the natural compound 5”-O-α-L-raminopyranosyl-1’-β-D-glycopyranosyl-4’,6-dimethoxyflavone (pectolinarin) isolated from L. camara leaves was evaluated. Tests for antibacterial activity of the pure natural substance and analysis of the potentiation of antibacterial activity of pectolinarin associated with antibiotics were carried out against standard and multiresistant bacterial strains of Escherichia coli and Staphylococcus aureus by microdilution. Pectolinarin, when combined with the antibiotic gentamicin, showed synergism, potentiating growth inhibition against Gram-positive S. aureus strains. The pectolinarin flavonoid when combined with the gentamicin antibiotic potentiated its action Gram-positive S. aureus bacteria. Moreover, an antagonistic effect was observed when the pectolinarin was combined with the penicillin antibiotic against the multiresistant S. aureus 358 strain. This research suggests that pectolinarin is a compound with potential application as an antibacterial drug.