Antibiotics resistance of Stenotrophomonas maltophilia strains isolated from various clinical specimens

Global mapping of antibiotic resistance rates among clinical isolates of Stenotrophomonas maltophilia: a systematic review and meta-analysis

INTRODUCTION

Infections caused by Stenotrophomonas maltophilia are clinically important due to its intrinsic resistance to a broad range of antibiotics. Therefore, selecting the most appropriate antibiotic to treat S. maltophilia infection is a major challenge.

AIM

The current meta-analysis aimed to investigate the global prevalence of antibiotic resistance among S. maltophilia isolates to the develop more effective therapeutic strategies.

METHOD

A systematic literature search was performed using the appropriate search syntax after searching Pubmed, Embase, Web of Science and Scopus databases (May 2023). Statistical analysis was performed using Pooled and the random effects model in R and the metafor package. A total of 11,438 articles were retrieved. After a thorough evaluation, 289 studies were finally eligible for inclusion in this systematic review and meta-analysis.

RESULT

Present analysis indicated that the highest incidences of resistance were associated with doripenem (97%), cefoxitin (96%), imipenem and cefuroxime (95%), ampicillin (94%), ceftriaxone (92%), aztreonam (91%) and meropenem (90%) which resistance to Carbapenems is intrinsic. The lowest resistance rates were documented for minocycline (3%), cefiderocol (4%). The global resistance rate to TMP-SMX remained constant in two periods before and after 2010 (14.4% vs. 14.6%). A significant increase in resistance to tigecycline and ceftolozane/tazobactam was observed before and after 2010.

CONCLUSIONS

Minocycline and cefiderocol can be considered the preferred treatment options due to low resistance rates, although regional differences in resistance rates to other antibiotics should be considered. The low global prevalence of resistance to TMP-SMX as a first-line treatment for S. maltophilia suggests that it remains an effective treatment option.

Evaluation of ethanol and EDTA concentrations in the expression of biofilm-producing smf-1, rpfF genes in XDR clinical isolates of Stenotrophomonas maltophilia

BACKGROUND

Stenotrophomonas maltophilia is able to cause infections in immunocompromised patients, and the treatment of this opportunistic pathogen is complicated due to its virulence factors, antibiotic resistance, and the ability of the bacteria to produce biofilm. The main goals of this study were to assess the susceptibility of extensively drug-resistant (XDR) isolates to ethanol and EDTA, and evaluating the synergistic effect of these disinfectants, and also survey the effect of exposure to sub-inhibitory concentrations of ethanol and EDTA on the expression of biofilm-producing smf-1, rpfF genes.

RESULTS

The results showed that EDTA significantly increased the effectiveness of the ethanol and have a synergistic effect. All of the 10 XDR isolates included in the current study harbored smf-1 and rpfF genes and produced biofilm. After exposure to MIC, sub-MIC, synergism, and sub-synergism of ethanol and EDTA, the expression of smf-1 and rpfF genes was repressed significantly.

CONCLUSION

In the current study, it was indicated that the expression of biofilm-producing genes was repressed when bacteria are exposed to different concentrations of ethanol and EDTA. Future studies should include more complex microbial communities residing in the hospitals, and more disinfectants use in hospitals. Expression of other virulence genes in different conditions is suggested.

Global prevalence and distribution of antibiotic resistance among clinical isolates of Stenotrophomonas maltophilia: A systematic review and meta-analysis

OBJECTIVES

Stenotrophomonas maltophilia (S. maltophilia), an opportunistic pathogen, causes infection in patients undergoing immunosuppressive therapy, mechanical ventilation, or catheters and in long-term hospitalized patients. Due to its extensive resistance to various antibiotics and chemotherapeutic agents, S. maltophilia is challenging to treat. Using case reports, case series, and prevalence studies, the current study provides a systematic review and meta-analysis of antibiotic resistance profiles across clinical isolates of S. maltophilia.

METHODS

A systematic literature search was performed for original research articles published in Medline, Web of Science, and Embase databases from 2000 to 2022. Statistical analysis was performed using STATA 14 software to report antibiotic resistance of S. maltophilia clinical isolates worldwide.

RESULTS

223 studies (39 case reports/case series and 184 prevalence studies) were collected for analysis. A meta-analysis of prevalence studies demonstrated that the most antibiotic resistance worldwide was to levofloxacin, trimethoprim-sulfamethoxazole (TMP/SMX), and minocycline (14.4%, 9.2%, and 1.4%, respectively). Resistance to TMP/SMX (36.84%), levofloxacin (19.29%), and minocycline (1.75%) were the most prevalent antibiotic resistance types found in evaluated case reports/case series studies. The highest resistance rate to TMP/SMX was reported in Asia (19.29%), Europe (10.52%), and America (7.01%), respectively.

CONCLUSION

Considering the high resistance to TMP/SMX, more attention should be paid to patients' drug regimens to prevent the emergence of multidrug-resistant S. maltophilia isolates.

In Vitro Activity of Cefiderocol against Clinical Gram-Negative Isolates Originating from Germany in 2016/17

Antimicrobial resistance poses a global threat to public health. Of great concern are Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacterales with resistance to carbapenems or third-generation cephalosporins. The aim of the present study was to investigate the in vitro activity of the novel siderophore cephaloporin cefiderocol (CID) and four comparator β-lactam-β-lactamase-inhibitor combinations and to give insights into the genetic background of CID-resistant isolates. In total, 301 clinical Enterobacterales and non-fermenting bacterial isolates were selected for this study, including randomly chosen isolates (set I, n = 195) and challenge isolates (set II, n = 106; enriched with ESBL and carbapenemase producers, as well as colistin-resistant isolates). Isolates displayed CID MIC_50/90 values of 0.12/0.5 mg/L (set I) and 0.5/1 mg/L (set II). Overall, the CID activity was superior to the comparators against A. baumannii, Stenotrophomonas maltophilia and set II isolates of P. aeruginosa. There were eight CID-resistant isolates detected (MIC > 2 mg/L): A. baumannii (n = 1), E. cloacae complex (n = 5) and P. aeruginosa (n = 2). Sequencing analyses of these isolates detected the acquired β-lactamase (bla) genes bla_NDM-1,bla_SHV-12 and naturally occurring bla_OXA-396, bla_ACT-type and bla_CMH-3. In conclusion, CID revealed potent activity against clinically relevant organisms of multidrug-resistant Enterobacterales and non-fermenters.

Global prevalence and antibiotic resistance in clinical isolates of Stenotrophomonas maltophilia: a systematic review and meta-analysis

Introduction

Stenotrophomonas maltophilia is a little-known environmental opportunistic bacterium that can cause broad-spectrum infections. Despite the importance of this bacterium as an emerging drug-resistant opportunistic pathogen, a comprehensive analysis of its prevalence and resistance to antibiotics has not yet been conducted.

Methods

A systematic search was performed using four electronic databases (MEDLINE via PubMed, Embase, Scopus, and Web of Science) up to October 2019. Out of 6,770 records, 179 were documented in the current meta-analysis according to our inclusion and exclusion criteria, and 95 studies were enrolled in the meta-analysis.

Results

Present analysis revealed that the global pooled prevalence of S. maltophilia was 5.3 % [95% CI, 4.1-6.7%], with a higher prevalence in the Western Pacific Region [10.5%; 95% CI, 5.7-18.6%] and a lower prevalence in the American regions [4.3%; 95% CI, 3.2-5.7%]. Based on our meta-analysis, the highest antibiotic resistance rate was against cefuroxime [99.1%; 95% CI, 97.3-99.7%], while the lowest resistance was correlated with minocycline [4·8%; 95% CI, 2.6-8.8%].

Discussion

The results of this study indicated that the prevalence of S. maltophilia infections has been increasing over time. A comparison of the antibiotic resistance of S. maltophilia before and after 2010 suggested there was an increasing trend in the resistance to some antibiotics, such as tigecycline and ticarcillin-clavulanic acid. However, trimethoprim-sulfamethoxazole is still considered an effective antibiotic for treating S. maltophilia infections.

A 20-year trend of prevalence and susceptibility to trimethoprim/sulfamethoxazole of Stenotrophomonas maltophilia in a single secondary care hospital in Korea

Stenotrophomonas maltophilia is a Gram-negative opportunistic pathogen that can cause serious infection. We aimed to analyze the prevalence and susceptibility rates to trimethoprim/sulfamethoxazole of S. maltophilia. We conducted a retrospective study of S. maltophilia isolates from a university hospital from 2001 to 2020. Clinical information, the numbers of isolates and susceptibility rates were analyzed by year. Susceptibility rates and changes in respiratory and non-respiratory samples were compared. 1805 S. maltophilia isolates were identified, of which 81.4% (1469/1805) were from respiratory samples. There was a male predominance and 52% of the isolates were from general wards. The average susceptibility rate was 87.7% and there was no significant annual trend (P = .519). The susceptibility rate was 88.7% in respiratory samples and 84.1% in non-respiratory samples (P = .018). Susceptibility analyses using clinical data over long periods can guide the choice of antimicrobials especially for pathogen whose treatment options are limited.

Stenotrophomonas maltophilia Epidemiology, Resistance Characteristics, and Clinical Outcomes: Understanding of the Recent Three Years' Trends

BACKGROUND

Stenotrophomonas maltophilia is an emerging pathogen classified as a public health concern, that infects critically ill patients and has expressed resistance against antimicrobial therapy. The aim of this study was to examine the epidemiological pattern, resistance characteristics and clinical outcomes of S. maltophilia infections in hospitalized patients.

METHODS

The study included 393 S. maltophilia isolates from different clinical specimens as well as the clinical data of 209 Intensive Care Unit (ICU) patients. The patients' data were obtained from medical and laboratory files. Descriptive statistics and a univariate analysis were used to report and compare the demographics, clinical data, and outcomes.

RESULTS

The S. maltophilia was mostly isolated from the respiratory specimens of ICU patients. The adult patients were more likely to develop serious infections and worse outcomes than were pediatric patients. The most common co-infecting pathogens were SARS-CoV2 and Pseudomonas aeruginosa. The death rate was 44.5% and increased to 47.1% in the case of a respiratory infection. Septic shock was the most significant predictor of mortality. Older age and mechanical ventilation were independent and significant risk factors that worsened the outcomes in patients with respiratory infections.

CONCLUSIONS

The identification of S. maltophilia as a threat highlights the importance of surveillance studies in this region.

Antibiotic Susceptibility and Minimum Inhibitory Concentration for Stenotrophomonas maltophilia Ocular Infections

Stenotrophomonas maltophilia (S. maltophilia) is a Gram-negative, opportunistic pathogen that can lead to ocular infections, such as keratitis and endophthalmitis. The purpose of this study was to determine the antibiotic susceptibility and minimum inhibitory concentrations (MICs) of S. maltophilia isolates from ocular infections and to evaluate the differences in antibiotic MICs between keratitis and endophthalmitis isolates. The disc diffusion method revealed that S. maltophilia isolates exhibited 91% susceptibility to levofloxacin and moxifloxacin and 61% susceptibility to trimethoprim−sulfamethoxazole (TMP−SMX). The E-test indicated that S. maltophilia isolates exhibited 40%, 100%, 72%, 91%, 91%, and 93% susceptibility to ceftazidime, tigecycline, TMP−SMX, levofloxacin, gatifloxacin, and moxifloxacin, respectively. The MIC90 values of amikacin, ceftazidime, cefuroxime, tigecycline, TMP−SMX, levofloxacin, gatifloxacin, and moxifloxacin were >256, >256, >256, 3, >32, 1, 2, and 0.75 µg/mL, respectively. The geometric mean MICs of ceftazidime, TMP−SMX, levofloxacin, gatifloxacin, and moxifloxacin were significantly lower for the keratitis isolates than for the endophthalmitis isolates (p = 0.0047, 0.003, 0.0029, 0.0003, and 0.0004, respectively). Fluoroquinolones showed higher susceptibility and lower MICs for the S. maltophilia isolates when compared with other antibiotics. Fluoroquinolones can be recommended for treating S. maltophilia ocular infections. Tigecycline and TMP−SMX could be alternative antibiotics for S. maltophilia ocular infections.

Evaluation of antibacterial activity of five biocides and the synergistic effect of biocide/EDTA combinations on biofilm-producing and non-producing Stenotrophomonas maltophilia strains isolated from clinical specimens in Iran

Background

The overuse of biocides in healthcare-facilities poses risk for emergence and spread of antibiotic resistance among nosocomial pathogens. Hospital-acquired infections due to S. maltophilia have been increased in the recent years and with its various resistance mechanisms contribute to patient morbidity and mortality in hospitals. The current study aimed to evaluate the susceptibility of biofilm-producing and non-producing S. maltophilia clinical isolates to five commonly used hospital biocides, alone and in combination with EDTA to examine the synergistic effect of combining EDTA on the bactericidal activity of them by microbroth dilution method. As well as the frequency of efflux genes encoding resistance to biocides among isolates. This study also intended to assess the effect of exposure of S. maltophilia isolates to sub-inhibitory concentrations of sodium hypochlorite upon the antimicrobial susceptibility patterns.

Results

Based on minimum inhibitory and bactericidal concentrations of biocides sodium hypochlorite 5% (w/v) and ethyl alcohol 70% (v/v) were the strongest and weakest biocides against S. maltophilia isolates, respectively. The combination of EDTA with biocides significantly increased the effectiveness of the studied biocides. Exposure to sub-inhibitory concentration of sodium hypochlorite showed a significant change in the susceptibility of isolates towards ceftazidime (p = 0.019), ticarcillin/clavulanate (p = 0.009), and chloramphenicol (p = 0.028). As well as among the isolates examined, 94 (95%) were able to produce biofilm. The frequency of sugE1 resistance genes was found in 90.7% of our clinical S. maltophilia isolates. None of the isolates carried qacE and qacEΔ1 gene.

Conclusions

The current study recommended that using the mixture of biocides with EDTA can be effective in reducing nosocomial infections. Also, this study demonstrated that exposure to sub-inhibitory concentrations of sodium hypochlorite leads to reduced antibiotic susceptibility and development of multidrug-resistant S. maltophilia strains.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-022-02664-1.

Biological characterization and complete genome analysis of a novel Stenotrophomonas maltophilia phage vB_SM_ytsc_ply2008005c

Multidrug-resistant bacteria have become a major threat to global public health. Bacteriophages are regarded as a promising substitute. Here, we present a novel lytic Stenotrophomonas maltophilia phage, vB_SM_ytsc_ply2008005c, which was isolated from sewage water samples in Qingdao, east China. Virion morphology of phage particles indicated that ply2008005c has an icosahedral head (56±5 nm in diameter) and a noncontractile sheathed tail (129±6 nm in length), which are the typical characteristics of phages belonging to the family Siphoviridae. Phage ply2008005c could be used for phage therapy for its stability in a wide pH (4 to 12) range and high temperature (up to 70°C) environment. Genome analysis revealed that ply2008005c has a circular double-strand DNA of 42,318 bp with a G+C content of 63.02%. It shared the closest relationship with phage vB_PaeS_PAO1_Ab18, but the homology coverage is just 20%. There were 54 open reading frames predicted in its genome, including three unique proteins and 34 functional genes in different modules. The phylogenetic analysis revealed that ply2008005c forms a distinct branch of the family Siphoviridae. These results demonstrated that ply2008005c was supposed to be a representative new member within the family Siphoviridae, which could be considered a potential bioagent against multidrug-resistant S. maltophilia.

Microbial Resistance to Antibiotics and Effective Antibiotherapy

Currently, the efficacy of antibiotics is severely affected by the emergence of the antimicrobial resistance phenomenon, leading to increased morbidity and mortality worldwide. Multidrug-resistant pathogens are found not only in hospital settings, but also in the community, and are considered one of the biggest public health concerns. The main mechanisms by which bacteria develop resistance to antibiotics include changes in the drug target, prevention of entering the cell, elimination through efflux pumps or inactivation of drugs. A better understanding and prediction of resistance patterns of a pathogen will lead to a better selection of active antibiotics for the treatment of multidrug-resistant infections.

Molecular Insight into Gene Response of Diorcinol- and Rubrolide-Treated Biofilms of the Emerging Pathogen Stenotrophomonas maltophilia

Stenotrophomonas maltophilia is a multidrug-resistant human opportunistic pathogen. S. maltophilia contributes to disease progression in cystic fibrosis patients and is found in wounds and infected tissues and on catheter surfaces. Due to its well-known multidrug resistance, it is difficult to treat S. maltophilia infections. Strain-specific susceptibility to antimicrobials has also been reported in several studies. Recently, three fungal diorcinols and 14 rubrolides were shown to reduce S. maltophilia K279a biofilm formation. Based on these initial findings, we were interested to extend this approach by testing a larger number of diorcinols and rubrolides and to understand the molecular mechanisms behind the observed antibiofilm effects. Of 52 tested compounds, 30 were able to significantly reduce the biofilm thickness by up to 85% ± 15% and had strong effects on mature biofilms. All compounds with antibiofilm activity also significantly affected the biofilm architecture. Additional RNA-sequencing data of diorcinol- and rubrolide-treated biofilm cells of two clinical isolates (454 and K279) identified a small set of shared genes that were affected by these potent antibiofilm compounds. Among these, genes for iron transport, general metabolism, and membrane biosynthesis were most strongly and differentially regulated. A further hierarchical clustering and detailed structural inspection of the diorcinols and rubrolides implied that a prenyl group as side chain of one of the phenyl groups of the diorcinols and an increasing degree of bromination of chlorinated rubrolides were possibly the cause of the strong antibiofilm effects. This study gives a deep insight into the effects of rubrolides and diorcinols on biofilms formed by the important global pathogen S. maltophilia.

IMPORTANCE Combating Stenotrophomonasmaltophilia biofilms in clinical and industrial settings has proven to be challenging. S. maltophilia is multidrug resistant, and occurrence of resistance to commonly used drugs as well as to antibiotic combinations, such as trimethoprim-sulfamethoxazole, is now frequently reported. It is therefore now necessary to look beyond conventional and already existing antimicrobial drugs when battling S. maltophilia biofilms. Our study contains comprehensive and detailed data sets for diorcinol and rubrolide-treated S. maltophilia biofilms. The study defines genes and pathways affected by treatment with these different compounds. These results, together with the identified structural elements that may be crucial for their antibiofilm activity, build a strong backbone for further research on diorcinols and rubrolides as novel and potent antibiofilm compounds.

Prevalence of trimethoprim/sulfamethoxazole resistance genes among Stenotrophomonas maltophilia clinical isolates in Egypt

Stenotrophomonas maltophilia is an important multidrug resistant nosocomial pathogen. Trimethoprim/sulfamethoxazole (TMP/SMX) is considered the drug of choice for treatment of S. maltophilia infections, thus emerging resistance to TMP/SMX poses a serious threat. In the present study we aimed to investigate the frequency of TMP/SMX resistance genes (sul1, sul2, dfrA), and to evaluate their relatedness with integron 1 (int1), and insertion sequence common regions (ISCR) among 100 S. maltophilia from different clinical isolates in Egypt. Isolates were identified biochemically and confirmed by VITEK2. Detection of sul1, sul2, and dfrA genes, int1 and ISCR elements was performed by PCR. Among the 16 TMP/SMX resistant isolates, sul1 gene was detected in all of them, and it was associated with int1 gene presence in all resistant isolates. The sul2 gene was detected in 6 out of 16 resistant isolates (37.5%), and only 2 of the 16 resistant isolates (12.5%) harboured dfrA gene. ISCR was detected in 10 of the resistant isolates (62.5%) and in 4 of them it was associated with the presence of sul2 gene. Among the 84 TMP/SMX sensitive isolates, sul1 gene was detected in 15 (17.8%), int1 in 16 (19%) and ISCR in 6 (7.1%). None of the susceptible isolates had sul2 or dfrA genes. These findings point out an increasing frequency of TMP/SMX resistance genes among S. maltophilia clinical isolates in our region, so the adoption of prudent use of S. maltophilia antimicrobial agents and the establishment of a surveillance system are desperately needed.

Emergence of fluoroquinolone resistance and possible mechanisms in clinical isolates of Stenotrophomonas maltophilia from Iran

Stenotrophomonas maltophilia exhibits wide spectrum of fluoroquinolone resistance using different mechanisms as multidrug efflux pumps and Smqnr alleles. Here, the role of smeDEF, smeVWX efflux genes and contribution of Smqnr alleles in the development of fluoroquinolone resistance was assessed. Ciprofloxacin, levofloxacin and moxifloxacin resistance were found in 10.9%, 3.5%, and 1.6% of isolates, respectively. More than four-fold differences in ciprofloxacin MICs were detected in the presence of reserpine and smeD, F, V expression was significantly associated with ciprofloxacin resistance (p = 0.017 for smeD, 0.003 for smeF, and 0.001 for smeV). Smqnr gene was found in 52% of the ciprofloxacin-resistant isolates and Smqnr8 was the most common allele detected. Fluoroquinolone resistance in S. maltophilia clinical isolates was significantly associated with active efflux pumps. There was no correlation between the Smqnr alleles and ciprofloxacin resistance; however, contribution of the Smqnr genes in low-level levofloxacin resistance was revealed.

An evaluation of six-year Stenotrophomonas maltophilia infections in a university hospital

Background

Stenotrophomonas maltophilia is a Gram-negative bacillus and opportunistic emergent pathogen causing hospital-acquired infections (HAIs). Due to risk factors such as prolonged intensive care unit stay and invasive procedures, it has become one of the leading causes of HAIs.

Objective

The aim of this study was to evaluate the epidemiology of S.maltophilia infections over a six-year period at Düzce University Hospital, Turkey.

Methods

The incidence, clinical characteristics, antimicrobial susceptibility and outcomes of nosocomial S. maltophilia infections during this period were retrospectively analyzed.

Results

During the study period, 67 samples obtained from 61 patients were identified. Pneumonias (82%) were the most common HAIs, followed by bloodstream infections (10.5%), urinary tract infections (3%), skin and soft tissue infections (3%) and surgical site infection (1.5%). Admission to intensive care, hospitalization exceeding 30 days, and previous use of broad-spectrum antibiotics constituted risk factors. Resistance to cotrimoxazole (6%) was lower than that to levofloxacin (18%).

Conclusion

The most important risk factors for S.maltophilia infection in patients are previous exposure to antibiotics, prolonged hospitalization and invasive procedures such as mechanic ventilation. Discharging patients as early as possible with the rational use of antibiotics may be effective in reducing S. maltophilia infections and resistance rates.

A prospective study of microbiological characterization and clinical facets of Stenotrophomonas maltophilia infections

Background and Objectives:

Stenotrophomonas maltophilia is a multidrug resistant opportunistic pathogen, which is normally present in hospital settings and has very high mortality rates.

Materials and Methods:

A prospective study was conducted over a period of two years. The specimens were processed by Gram staining and aerobic culture. The bacteria were isolated using standard protocols. The extent of antibiotic resistance of commonly used antimicrobials and biofilm production were studied in the isolates.

Results:

A total of 80 strains of Stenotrophomonas maltophilia were isolated. The maximum sensitivity (93.8%) of these isolates was noticed for cotrimoxazole. 63.7% of strains were strong biofilm producers. The group given pathogen specific antibiotic showed better prognosis (P value ≤ 0.05).

Conclusion:

Early diagnosis and proper management of cases infected with Stenotrophomonas maltophilia is important to avoid therapeutic failures.

Endocarditis caused by Stenotrophomonas maltophilia-A rare presentation of an emerging opportunistic pathogen

First isolated in 1943, Stenotrophomonas maltophilia (S. maltophilia) has historically been of little significance as it was considered a pathogen of low virulence noted to rarely infect immunocompromised hosts. However, over the last 30 years the prevalence of infection caused by the organism has increased significantly. Bacterial endocarditis from S. maltophilia remains exceedingly rare with only a small number of reported cases in the literature. This case involves a 27 year old male with sickle cell anemia with an indwelling right subclavian port who presented to the emergency department with myalgias, fever, and chills. His initial blood cultures grew Gram negative rods later identified as S. maltophilia. Transthoracic echocardiogram showed a mass in the right atrium. Transesophageal echocardiogram revealed a large C-shaped mass with attachment to the tricuspid annulus, mitral valve wall, and port tip in right atrium. The patient underwent sternotomy with removal of the vegetation to prevent embolization. He was treated with intravenous ciprofloxacin and oral trimethoprim/sulfamethoxazole to complete a full 6 weeks of therapy, making a full recovery. This report will further explore the unique presentation of this pathogen along with its epidemiology, resistance mechanisms, risk factors for infection, diagnosis, and appropriate antimicrobial treatment.

Presence of carbapenem-resistant bacteria in soils affected by illegal waste dumps

The carbapenem-resistant bacteria (CRB) are currently at the top of the WHO priority list of bacteria that pose the greatest threat to human health. Considering that soil is one of the important environments for the emergence of antibiotic-resistant bacteria, we isolated and quantified cultivable CRB in soils across Croatia, including ones affected by illegal dumps.We cultivated CRB at two temperatures, distinguishing between the intrinsically resistant CRB (37°C, mostly Stenotrophomonas spp.) and the ones that are presumably human-associated and clinically relevant (42°C, Acinetobacter sp., Enterobacteriaceae, Burkholderia spp.). Our study demonstrated that distinguishing between the two offers a better insight into the diversity of CRB in the environment. The ones cultivated at 37°C were found in almost all soil samples, while the presumably clinically relevant ones were absent from uncontaminated pasture and grassland, indicating that human-associated CRB are unlikely to be found in soils spared from anthropogenic influence.

Characterization of bacterial diversity in contaminated groundwater using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Groundwater is a major source for drinking water in the United States, and therefore, its quality and quantity is of extreme importance. One major concern that has emerged is the possible contamination of groundwater due to the unconventional oil and gas extraction activities. As such, the impacts of exogenous contaminants on microbial ecology is an area to be explored to understand what are the chemical and physical conditions that allow the proliferation of pathogenic bacteria and to find alternatives for water treatment by identifying organic-degrading bacteria. In this work, we assess the interplay between groundwater quality and the microbiome in contaminated groundwaters rich in hydrocarbon gases, volatile organic and inorganic compounds, and various metals. Opportunistic pathogenic bacteria, such as Aeromonas hydrophila, Bacillus cereus, Pseudomonas aeruginosa, and Stenotrophomonas maltophilia, were identified, increasing the risk for consumption of and exposure to these contaminated groundwaters. Additionally, antimicrobial tests revealed that many of the identified bacteria were resistant to different antibiotics. The MALDI-TOF MS results were successfully confirmed with 16S rRNA gene sequencing, proving the accuracy of this high-throughput method. Collectively, these data provide a seminal understanding of the microbial populations in contaminated groundwater overlying anthropogenic activities like unconventional oil and gas development.

The Resistome of Low-Impacted Marine Environments Is Composed by Distant Metallo-β-Lactamases Homologs

The worldwide dispersion and sudden emergence of new antibiotic resistance genes (ARGs) determined the need in uncovering which environment participate most as their source and reservoir. ARGs closely related to those currently found in human pathogens occur in the resistome of anthropogenic impacted environments. However, the role of pristine environment as the origin and source of ARGs remains underexplored and controversy, particularly, the marine environments represented by the oceans. Here, due to the ocean nature, we hypothesized that the resistome of this pristine/low-impacted marine environment is represented by distant ARG homologs. To test this hypothesis we performed an in silico analysis on the Global Ocean Sampling (GOS) metagenomic project dataset focusing on the metallo-β-lactamases (MβLs) as the ARG model. MβLs have been a challenge to public health, since they hydrolyze the carbapenems, one of the last therapeutic choice in clinics. Using Hidden Markov Model (HMM) profiles, we were successful in identifying a high diversity of distant MβL homologs, related to the B1, B2, and B3 subclasses. The majority of them were distributed across the Atlantic, Indian, and Pacific Oceans being related to the chromosomally encoded MβL GOB present in Elizabethkingia genus. It was observed only a reduced number of metagenomic sequence homologs related to the acquired MβL enzymes (VIM, SPM-1, and AIM-1) that currently have impact in clinics. Therefore, low antibiotic impacted marine environment, as the ocean, are unlikely the source of ARGs that have been causing enormous threat to the public health.

Antibacterial Activity of Endophytic Actinomycetes Isolated from the Medicinal Plant Vochysia divergens (Pantanal, Brazil)

Endophytic actinomycetes from medicinal plants produce a wide diversity of secondary metabolites (SM). However, to date, the knowledge about endophytes from Brazil remains scarce. Thus, we analyzed the antimicrobial potential of 10 actinomycetes isolated from the medicinal plant Vochysia divergens located in the Pantanal sul-mato-grossense, an unexplored wetland in Brazil. Strains were classified as belonging to the Aeromicrobium, Actinomadura, Microbacterium, Microbispora, Micrococcus, Sphaerisporangium, Streptomyces, and Williamsia genera, through morphological and 16S rRNA phylogenetic analyzes. A susceptibility analysis demonstrated that the strains were largely resistant to the antibiotics oxacillin and nalidixic acid. Additionally, different culture media (SG and R5A), and temperatures (28 and 36°C) were evaluated to select the best culture conditions to produce the active SM. All conditions were analyzed for active metabolites, and the best antibacterial activity was observed from metabolites produced with SG medium at 36°C. The LGMB491 (close related to Aeromicrobium ponti) extract showed the highest activity against methicillin-resistant Staphylococcus aureus (MRSA), with a MIC of 0.04 mg/mL, and it was selected for SM identification. Strain LGMB491 produced 1-acetyl-β-carboline (1), indole-3-carbaldehyde (2), 3-(hydroxyacetyl)-indole (4), brevianamide F (5), and cyclo-(L-Pro-L-Phe) (6) as major compounds with antibacterial activity. In this study, we add to the knowledge about the endophytic community from the medicinal plant V. divergens and report the isolation of rare actinomycetes that produce highly active metabolites.