Prevalence and Antibiotic Resistance of Stenotrophomonas maltophilia in Respiratory Tract Samples: A 10-Year Epidemiological Snapshot

The airway microbiome of persons with cystic fibrosis correlates with acquisition and microbiological outcomes of incident Stenotrophomonas maltophilia infection

Rationale

Chronic infection with Stenotrophomonas maltophilia in persons with cystic fibrosis (pwCF) has been linked to an increased risk of pulmonary exacerbations and lung function decline. We sought to establish whether baseline sputum microbiome associates with risk of S. maltophilia incident infection and persistence in pwCF.

Methods

pwCF experiencing incident S. maltophilia infections attending the Calgary Adult CF Clinic from 2010-2018 were compared with S. maltophilia-negative sex, age (+/-2 years), and birth-cohort-matched controls. Infection outcomes were classified as persistent (when the pathogen was recovered in ≥50% of cultures in the subsequent year) or transient. We assessed microbial communities from prospectively biobanked sputum using V3-V4 16S ribosomal RNA (rRNA) gene sequencing, in the year preceding (Pre) (n = 57), at (At) (n = 22), and after (Post) (n = 31) incident infection. We verified relative abundance data using S. maltophilia-specific qPCR and 16S rRNA-targeted qPCR to assess bioburden. Strains were typed using pulse-field gel electrophoresis.

Results

Twenty-five pwCF with incident S. maltophilia (56% female, median 29 years, median FEV1 61%) with 33 total episodes were compared with 56 uninfected pwCF controls. Demographics and clinical characteristics were similar between cohorts. Among those with incident S. maltophilia infection, sputum communities did not cluster based on infection timeline (Pre, At, Post). Communities differed between the infection cohort and controls (n = 56) based on Shannon Diversity Index (SDI, p = 0.04) and clustered based on Aitchison distance (PERMANOVA, p = 0.01) prior to infection. At the time of incident S. maltophilia isolation, communities did not differ in SDI but clustered based on Aitchison distance (PERMANOVA, p = 0.03) in those that ultimately developed persistent infection versus those that were transient. S. maltophilia abundance within sputum was increased in samples from patients (Pre) relative to controls, measuring both relative (p = 0.004) and absolute (p = 0.001). Furthermore, S. maltophilia abundance was increased in sputum at incident infection in those who ultimately developed persistent infection relative to those with transient infection, measured relatively (p = 0.04) or absolute (p = 0.04), respectively.

Conclusion

Microbial community composition of CF sputum associates with S. maltophilia infection acquisition as well as infection outcome. Our study suggests sputum microbiome may serve as a surrogate for identifying infection risk and persistence risk.

Case series: Stenotrophomonas maltophilia in pediatric oncology patients

BACKGROUND

Stenotrophomonas maltophilia is a bacterial pathogen that can be fatal in hospitalized and immunocompromised patients with mortality as high as 69%. Pediatric cancer patients often have risk factors that are common for this infection, making them particularly susceptible. Managing S. maltophilia is especially challenging as it has inherent resistance to several antibiotics. Furthermore, soft tissue infections in neutropenic patients may deviate from the typical clinical presentation of S. maltophilia.

CASE DETAILS

This case series describes an in-depth examination of three cases involving immunocompromised pediatric patients with S. maltophilia infections. Each case exhibited a distinct clinical presentation, encompassing infection of the blood, lung, and skin, which highlights the variability in which S. maltophilia manifests in immunocompromised pediatric patients. These patients were treated at MD Anderson Cancer Center (MDACC) from 2020 to 2023, unfortunately resulting in fatality.

CONCLUSIONS

The study aims to provide valuable insights and guidance for the management of patients with S. maltophilia infections. Emphasizing a heightened clinical suspicion will potentially lead to early initiation of directed therapy against S. maltophilia. Timely intervention may play a pivotal role in improving patient outcomes and reduce further burden to the healthcare system.

A guide to Stenotrophomonas maltophilia virulence capabilities, as we currently understand them

The Gram-negative pathogen Stenotrophomonas maltophilia causes a wide range of human infections. It causes particularly serious lung infections in individuals with cystic fibrosis, leading to high mortality rates. This pathogen is resistant to most known antibiotics and harbors a plethora of virulence factors, including lytic enzymes and serine proteases, that cause acute infection in host organisms. S. maltophilia also establishes chronic infections through biofilm formation. The biofilm environment protects the bacteria from external threats and harsh conditions and is therefore vital for the long-term pathogenesis of the microbe. While studies have identified several genes that mediate S. maltophilia's initial colonization and biofilm formation, the cascade of events initiated by these factors is poorly understood. Consequently, understanding these and other virulence factors can yield exciting new targets for novel therapeutics.

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.

The Relationship between the Biofilm Genes and Antibiotic Resistance in Stenotrophomonas maltophilia

Objectives

Today, Stenotrophomonas maltophilia (S. maltophilia) is a major opportunistic pathogen among hospitalized or immunocompromised patients. Antibiotic-resistant clinical isolates are increasing in several parts of the world. Various antibiotic-resistance and biofilm-forming genes are identified in this bacterium. Its capacity to form biofilms is an important virulence factor that may impact antibiotic-resistance patterns. In the current study, we evaluated the biofilm-formation capacity, antibiotic-resistance profile, and prevalence of biofilm-forming genes as well as antibiotic resistance genes among S. maltophilia isolates.

Materials and Methods

In this cross-sectional study, 94 clinical S. maltophilia isolates were recovered from four tertiary-care hospitals in Iran between 2021 and 2022. The presence of the selected antibiotic-resistance genes and biofilm-forming genes was examined by polymerase chain reaction (PCR). The ability of biofilm formation was examined by microtiter plate assay. The Kirby-Bauer disc diffusion method was used to evaluate the trimethoprim-sulfamethoxazole (TMP-SMX), levofloxacin, and minocycline resistance.

Results

S. maltophilia is mainly isolated from bloodstream infections. Notably, 98.93% of isolates were biofilm producers, of which 19.35%, 60.22%, and 20.43% produced strong, moderate, and weak biofilm, respectively. The frequency of biofilm genes was 100%, 97.88%, 96.80%, and 75.53% for spgM, rmlA, smf-1, and rpfF, respectively. Isolates with the genotype of smf-1+/rmlA+/spgM+/rpfF+ were mostly strong biofilm producers. Among the antibiotic-resistance genes, the Smqnr, L1, and sul1 had the highest prevalence (76.59%, 72.34%, and 64.89), respectively. Antimicrobial susceptibility evaluation showed 1.06%, 3.19%, and 6.3% resistance to minocycline, TMP-SMX, and levofloxacin.

Conclusion

The results of the current study demonstrated that S. maltophilia isolates differ in biofilm-forming ability. Moreover, smf-1, rmlA, and spgM genes were presented in all strong biofilm producers. Although the overall resistance rate to the evaluated antibiotics was high, there was no statistically significant relation between antibiotic resistance and the type of biofilm.

The Activities of Antimicrobials Against Stenotrophomonas maltophilia Isolates and Evaluation of Clinical Outcomes Among Treatment Regimens in Patients with Stenotrophomonas maltophilia Infections: A Retrospective Multicenter Cohort Study

Purpose

Stenotrophomonas maltophilia, a multidrug-resistant pathogen can cause hospital-acquired infections such as pneumonia, or bloodstream infection. S. maltophilia infection is associated with high mortality rates. This retrospective study examined the antimicrobial susceptibility profile of clinical S. maltophilia isolates and evaluated clinical outcomes, treatment regimens, and risk factors associated with 30-day mortality or treatment failure of S. maltophilia infections at three tertiary care hospitals in Central Thailand.

Patients and Methods

The characteristics, microbiological data, and clinical treatment outcomes were derived from medical records obtained from three tertiary care hospitals in Central Thailand from January 2017 to October 2022. The primary outcomes were treatment failure and 30-day mortality. The antimicrobial susceptibility rates of trimethoprim-sulfamethoxazole (TMP-SMX), levofloxacin, and ceftazidime were determined by minimum inhibitory concentration (MIC), which were based on broth microdilution and clear zone diameters using the disk diffusion method. However, we also report the susceptibility of minocycline and tigecycline in some clinical S. maltophilia strains (n = 149) and determined by MIC with E-test method.

Results

The antimicrobial susceptibility rates to TMP-SMX, levofloxacin, and ceftazidime were 97.1%, 93%, and 55.3%, respectively. The treatment failure rate and 30-day mortality were 66.3% and 49%, respectively. Significant factors associated with treatment failure included APACHE II score ≥15 (OR 3.37, 95% confidence interval (CI) 1.46-7.76), polymicrobial infections (OR 3.20, 95% CI 1.35-7.55). The significant factors associated with reduced treatment failure was treatment with TMP-SMX-based regimen (OR 0.29, 95% CI 0.11-0.76). The 30-day mortality rate was associated with APACHE II score ≥15 (OR 3.27, 95% CI 1.45-7.39) and septic shock (OR 2.53, 95% CI 1.36-4.69).

Conclusion

The results indicate a high mortality rate for S. maltophilia infection. The predictive factors for an unfavourable outcome were severity of illness, septic shock, and non-use of TMP-SMX. Therefore, a TMP-SMX-based regimen is recommended for the treatment of S. maltophilia infections.

Steno-sphere: Navigating the enigmatic world of emerging multidrug-resistant Stenotrophomonas maltophilia

Stenotrophomonas maltophilia is an opportunistic pathogen and frequent cause of serious nosocomial infections. Patient populations at greatest risk for these infections include the immunocompromised and those with chronic respiratory illnesses and prior antibiotic exposure, notably to carbapenems. Its complex virulence and resistance profile drastically limit available antibiotics, and incomplete breakpoint and pharmacokinetic/pharmacodynamic (PK/PD) data to inform dose optimization further complicates therapeutic approaches. Clinical comparison data of first-line agents, including trimethoprim-sulfamethoxazole (TMP-SMX), quinolones, and minocycline, are limited to conflicting observational data with no clear benefit of a single agent or combination therapy. Newer antibiotic approaches, including cefiderocol and aztreonam- avibactam, are promising alternatives for extensively drug-resistant isolates; however, clinical outcomes data are needed. The potential clinical utility of bacteriophage for compassionate use in treating S. maltophilia infections remains to be determined since data is limited to in-vitro and sparse in-vivo work. This article provides a review of available literature for S. maltophilia infection management focused on related epidemiology, resistance mechanisms, identification, susceptibility testing, antimicrobial PK/PD, and emerging therapeutic strategies.

Economic and health impact modelling of a whole genome sequencing-led intervention strategy for bacterial healthcare-associated infections for England and for the USA

Bacterial healthcare-associated infections (HAIs) are a substantial source of global morbidity and mortality. The estimated cost associated with HAIs ranges from $35 to $45 billion in the USA alone. The costs and accessibility of whole genome sequencing (WGS) of bacteria and the lack of sufficiently accurate, high-resolution, scalable and accessible analysis for strain identification are being addressed. Thus, it is timely to determine the economic viability and impact of routine diagnostic bacterial genomics. The aim of this study was to model the economic impact of a WGS surveillance system that proactively detects and directs interventions for nosocomial infections and outbreaks compared to the current standard of care, without WGS. Using a synthesis of published models, inputs from national statistics, and peer-reviewed articles, the economic impacts of conducting a WGS-led surveillance system addressing the 11 most common nosocomial pathogen groups in England and the USA were modelled. This was followed by a series of sensitivity analyses. England was used to establish the baseline model because of the greater availability of underpinning data, and this was then modified using USA-specific parameters where available. The model for the NHS in England shows bacterial HAIs currently cost the NHS around £3 billion. WGS-based surveillance delivery is predicted to cost £61.1 million associated with the prevention of 74 408 HAIs and 1257 deaths. The net cost saving was £478.3 million, of which £65.8 million were from directly incurred savings (antibiotics, consumables, etc.) and £412.5 million from opportunity cost savings due to re-allocation of hospital beds and healthcare professionals. The USA model indicates that the bacterial HAI care baseline costs are around $18.3 billion. WGS surveillance costs $169.2 million, and resulted in a net saving of ca.$3.2 billion, while preventing 169 260 HAIs and 4862 deaths. From a 'return on investment' perspective, the model predicts a return to the hospitals of £7.83 per £1 invested in diagnostic WGS in the UK, and US$18.74 per $1 in the USA. Sensitivity analyses show that substantial savings are retained when inputs to the model are varied within a wide range of upper and lower limits. Modelling a proactive WGS system addressing HAI pathogens shows significant improvement in morbidity and mortality while simultaneously achieving substantial savings to healthcare facilities that more than offset the cost of implementing diagnostic genomics surveillance.

The prevalence of colistin resistance in clinical Stenotrophomonas maltophilia isolates worldwide: a systematic review and meta-analysis

While trimethoprim-sulfamethoxazole (TMP-SMX) is the first-line therapy of Stenotrophomonas maltophilia infections, colistin is one of the therapeutic options in cases of allergy or resistance to TMP-SMX. However, understanding the global status of resistance to colistin amongst S. maltophilia isolates could be helpful for appropriate antibiotic prescription. This study aimed to conduct a systematic review and meta-analysis to examine the prevalence of colistin resistance in clinical S. maltophilia isolates worldwide. According to eligibility criteria, a total of 61 studies were included in the analysis. The pooled prevalence for colistin resistance was 42% (95% CI: 35-49%), ranging from 0.1 to 97%. Subgroups analysis indicated that, the pooled prevalence of colistin resistance was 44% (95% CI: 29-60%) in 15 studies during 2000-2010, and it was estimated to be 41% (95% CI: 33-50%) in 46 articles from 2011 to 2021. It was 46% (95% CI: 35-58%) in the studies that used broth microdilution method, and 39% (95% CI: 30-49%) in the studies with other used methods. The resistance rate in Asian countries was 45% (95% CI: 31-60%), in European countries was 45% (95% CI: 34-56%) and in the countries of North and South America was 33% (95% CI: 20-46%). Our review showed notable resistance to colistin in clinical S. maltophilia isolates. Given the estimated resistance rates, alternative antibiotics could be preferred to treat serious infections due to S. maltophilia.

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.

Antibiotic and metal resistance of Stenotrophomonas maltophilia isolates from Eboling permafrost of the Tibetan Plateau

Whole-genome sequencing of pathogenic bacteria Stenotrophomonas maltophilia from a less polluted environment of permafrost can help understand the intrinsic resistome of both antibiotics and metals. This study aimed to examine the maximum minimum inhibitory concentration (MIC) of both antibiotics and metals, as well as antibiotic resistance genes and metal resistance genes annotated from whole-genome sequences. The permafrost S. maltophilia was sensitive to ciprofloxacin, tetracycline, streptomycin, and bacitracin, and resistant to chloramphenicol, trimethoprim-sulfamethoxazole, erythromycin, Zn²⁺, Ni²⁺, Cu²⁺, and Cr⁶⁺, with a lower maximum MIC, compared with clinical S. maltophilia. The former strain belonged to the lower antibiotic resistance gene (ARG) and metal resistance gene (MRG) clusters compared with the latter ones. The permafrost strain contained no or only one kind of ARG or MRG on a single genomic island, which explained the aforementioned lower maximum MIC and less diversity of ARGs or MRGs. The result indicated that the co-occurrence of antibiotic and metal resistance was due to a certain innate ability of S. maltophilia. The continuous human use of antibiotics or metals induced selective pressure, resulting in higher MIC and more diverse ARGs and MRGs in human-impacted environments.

Infection Trends, Susceptibility Pattern, and Treatment Options for Stenotrophomonas maltophilia Infections in Trauma Patients: A Retrospective Study

Introduction Stenotrophomonas maltophilia is an emerging environmental, gram-negative, multidrug-resistant organism, associated with risk factors such as prolonged hospitalization, invasive procedures, admission to the intensive care unit, mechanical ventilation, use of indwelling catheters, administration of immunosuppressants or corticosteroids, human immunodeficiency virus infection, underlying malignancy, and organ transplantation. The organism, despite being of low invasiveness in immune-competent individuals, is difficult to treat because of intrinsic resistance to several antimicrobial agents.

Materials and Methods This study focuses on commonly encountered resistance from among the isolates over a duration of 7 years from 2012 to 2018, analyzed retrospectively. Identification and susceptibility testing were performed using Vitek 2 (BioMérieux, Marcy-l'Etoile, France).

Results Bloodstream infections were found to be most common (52.02%), followed by respiratory infections (35.83%). The median age of the patients was 36 years, and male to female ratio was 143:27. The median duration of hospital stay was 18 days, and mortality was seen in 18.82% of patients. Susceptibility to cotrimoxazole and levofloxacin was seen in 97.1% of isolates (168 out of 173) and 90.1% of isolates (156 out of 173), respectively.

Conclusion Despite being effective in a majority of S. maltophilia isolates, both cotrimoxazole and levofloxacin have their shortcomings. Cotrimoxazole is bacteriostatic and can cause bone marrow suppression and resistance to levofloxacin sometimes develops during therapy. Thus, the therapy should be decided considering the characteristics of both of these drugs.

Colistin-degrading proteases confer collective resistance to microbial communities during polymicrobial infections

BACKGROUND

The increasing prevalence of resistance against the last-resort antibiotic colistin is a significant threat to global public health. Here, we discovered a novel colistin resistance mechanism via enzymatic inactivation of the drug and proposed its clinical importance in microbial communities during polymicrobial infections.

RESULTS

A bacterial strain of the Gram-negative opportunistic pathogen Stenotrophomonas maltophilia capable of degrading colistin and exhibiting a high-level colistin resistance was isolated from the soil environment. A colistin-degrading protease (Cdp) was identified in this strain, and its contribution to colistin resistance was demonstrated by growth inhibition experiments using knock-out (Δcdp) and complemented (Δcdp::cdp) mutants. Coculture and coinfection experiments revealed that S. maltophilia carrying the cdp gene could inactivate colistin and protect otherwise susceptible Pseudomonas aeruginosa, which may seriously affect the clinical efficacy of the drug for the treatment of cystic fibrosis patients with polymicrobial infection.

CONCLUSIONS

Our results suggest that Cdp should be recognized as a colistin resistance determinant that confers collective resistance at the microbial community level. Our study will provide vital information for successful clinical outcomes during the treatment of complex polymicrobial infections, particularly including S. maltophilia and other colistin-susceptible Gram-negative pathogens such as P. aeruginosa. Video abstract.

Clinical challenges treating Stenotrophomonas maltophilia infections: an update

Stenotrophomonas maltophilia is a non-fermenting, Gram-negative bacillus that has emerged as an opportunistic nosocomial pathogen. Its intrinsic multidrug resistance makes treating infections caused by S. maltophilia a great clinical challenge. Clinical management is further complicated by its molecular heterogeneity that is reflected in the uneven distribution of antibiotic resistance and virulence determinants among different strains, the shortcomings of available antimicrobial susceptibility tests and the lack of standardized breakpoints for the handful of antibiotics with in vitro activity against this microorganism. Herein, we provide an update on the most recent literature concerning these issues, emphasizing the impact they have on clinical management of S. maltophilia infections.

Review on Stenotrophomonas maltophilia: an emerging multidrug-resistant opportunistic pathogen

Stenotrophomonas maltophilia is an opportunistic pathogen that results in nosocomial infections in immunocompromised individuals. These bacteria colonize on the surface of medical devices and therapeutic equipment like urinary catheters, endoscopes, and ventilators, causing respiratory and urinary tract infections. The low outer membrane permeability of multidrug-resistance efflux systems and the two chromosomally encoded β-lactamases present in S.maltophilia are challenging for arsenal control. The cell-associated and extracellular virulence factors in S.maltophilia are involved in colonization and biofilm formation on the host surfaces. The spread of antibiotic-resistant genes in the pathogenic S.maltophilia attributes to bacterial resistance against a wide range of antibiotics, including penicillin, quinolones, and carbapenems. So far, tetracycline derivatives, fluoroquinolones, and trimethoprim-sulfamethoxazole (TMP-SMX) are considered promising antibiotics against S.maltophilia. Due to the adaptive nature of the intrinsically resistant mechanism towards the number of antibiotics and its ability to acquire new resistance via mutation and horizontal gene transfer, it is quite tricky for medicinal contribution against S.maltophilia. The current review summarizes the literary data of pathogenicity, quorum sensing, biofilm formation, virulence factors, and antibiotic resistance of S.maltophilia.

Multi-drug resistant gram-negative bacterial pneumonia: etiology, risk factors, and drug resistance patterns

Bacterial pneumonia is one of the most serious public health issues owing to its medical and economic costs, which result in increased morbidity and mortality in people of all ages around the world. Furthermore, antimicrobial resistance has risen over time, and the advent of multi-drug resistance in GNB complicates therapy and has a detrimental impact on patient outcomes. The current review aimed to summarize bacterial pneumonia with an emphasis on gram-negative etiology, pathogenesis, risk factors, resistance mechanisms, treatment updates, and vaccine concerns to tackle the problem before it causes a serious consequence. In conclusion, the global prevalence of GNB in CAP was reported 49.7% to 83.1%, whereas in VAP patients ranged between 76.13% to 95.3%. The most commonly reported MDR-GNB causes of pneumonia were A. baumannii, K. pneumoniae, and P. aeruginosa, with A. baumannii isolated particularly in VAP patients and the elderly. In most studies, ampicillin, tetracyclines, amoxicillin-clavulanic acid, cephalosporins, and carbapenems were shown to be highly resistant. Prior MDR-GNB infection, older age, previous use of broad-spectrum antibiotics, high frequency of local antibiotic resistance, prolonged hospital stays, ICU admission, mechanical ventilation, and immunosuppression are associated with the MDR-GNB colonization. S. maltophilia was reported as a severe cause of HAP/VAP in patients with mechanically ventilated and having hematologic malignancy due to its ability of biofilm formation, site adhesion in respiratory devices, and its intrinsic and acquired drug resistance mechanisms. Effective combination therapies targeting PDR strains and drug-resistant genes, antibiofilm agents, gene-based vaccinations, and pathogen-specific lymphocytes should be developed in the future.

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.

Clinical and Epidemiological Characteristics of Stenotrophomonas maltophilia Associated Lower Respiratory Tract Infections in Qatar: A Retrospective Study

Background

Stenotrophomonas maltophilia is a rapidly emerging nosocomial pathogen with intrinsic or acquired resistance mechanisms to several antibiotic classes. It can cause life-threatening opportunistic pneumonia, particularly among hospitalized patients. Incidence of infections by S. maltophilia has been reported as 0.07-0.4% of hospital discharges, but its mortality is 20 -60%. This is the first study from Qatar indexing the clinical and epidemiological characteristics and antibiotic susceptibility of S. maltophilia.

Materials and methods

This retrospective descriptive epidemiological study was conducted in 6 tertiary care hospitals under Hamad Medical Corporation in Doha, Qatar, analyzing inpatient respiratory isolates of S. maltophilia during 2016-17. Out-patients, children below 14 years, and non-respiratory samples except blood cultures in patients with pneumonia were excluded. Clinical records were reviewed to identify possible risk factors. Infection and colonization were identified using the Centers for Disease Control and Prevention (CDC) algorithm for clinically defined pneumonia and statistically analyzed using the chi-square test and Pearson's correlation.

Results

S. maltophilia was isolated from 2.07% (317/15312) of all respiratory samples received in the microbiology lab during our study period. Three hundred seventeen patients studied had a mean age of 60 ± 20 years, and 68% were men. Most of the isolates were from sputum (179), followed by tracheal aspirate (82) and bronchoscopy (42). Fourteen blood culture samples from patients diagnosed with pneumonia were also included. 67% were hospitalized for more than two weeks, 39.1% were on mechanical ventilators, and 88% had received a broad-spectrum antibiotic before the event. 29.1% were deemed to have an infection and 70.9% colonization. Incidence of infection in those with Charlson’s Co-morbidity Index (CCI) ≥ 3 was 36.5% compared to 24.2% in those with CCI < 3 (Relative Risk (RR)=1.52; 95% CI: 1.04,2.18; p=0.01). Patients with recent chemotherapy, immunosuppressant, or steroid use had a significantly higher infection risk than those without (69.2% v/s 23.3% RR=2.96; 95% CI:2.2,3.9; p<0.005). The most common symptoms in patients with infection were fever (96%) and expectoration (61.9%). The most common radiological finding was lobar consolidation (71.6%). Mean CRP and procalcitonin were 106.5±15.5 mg/l and 12.3 ± 14 ng/ml. Overall mortality was 16.3%. Patients on mechanical ventilator with IBMP-10 score ≥ 2 had 22.8% mortality compared to 5.7% in those with score < 2 (RR=3.9;95%CI:0.9,16.6; p<0.015). As per The US Clinical and Laboratory Standards Institute (CSLI) breakpoint values, Trimethoprim-Sulfamethoxazole (TMP-SMX) showed the highest sensitivity (97.8%), followed by levofloxacin (71.6%). 0.3% of samples were pan-drug resistant.

Conclusions

S. maltophilia is a frequent nosocomial colonizer, but it can cause nosocomial pneumonia in almost one-third of cases, specifically in immunocompromised and patients with CCI ≥ 3 with a high risk of mortality due to ventilator-associated pneumonia (VAP) in those with IBMP-10 ≥ 2. Prolonged hospital stay is a risk factor for colonization by S. maltophilia, while recent chemotherapy, immunosuppressant, or steroid use are risk factors for hospital-acquired pneumonia due to S. maltophilia. TMP-SMX and levofloxacin are the only reliable agents for monotherapy of respiratory infections due to S. maltophilia in Qatar.

Xanthogranulomatous Pyelonephritis Caused by Stenotrophomonas maltophilia—The First Case Report and Brief Review

Xanthogranulomatous pyelonephritis (XGP) represents a rare and severe pathology secondary to chronic urinary obstruction and recurrent infections. Commonly, this condition leads to loss of kidney function, and frequently, surgical approach is the only optional treatment. Proteus mirabilis and Escherichia coli are the most frequent pathogens associated with XGP. The actual changes in the pathogen’s characteristics increased the risk of newly acquired infections once considered opportunistic. Stenotrophomonas malthophilia is one of those agents more related to immunocompromised patients, presenting an increased incidence and modified antibiotic resistance profile in the modern era. This case report presents a healthy female patient with an underlying renal stone pathology diagnosed with XGP related to S. maltophilia urinary infection. After a complete biological and imagistic evaluation, the case was treated as pyonephrosis. Empirical antibiotic administration and a surgical approach were considered. A total nephrectomy was performed, but the patient’s condition did not improve. The patient’s status improved when specific antibiotics were administered based on the bacterial identification and antibiotic susceptibility pattern of drained perinephric fluid. Levofloxacin and Vancomycin were considered the optimal combination in this case. The histopathological examination revealed XGP secondary to chronic renal stone. The present study describes the first case of XGP related to an aerobic Gram-negative pathogen such as S. maltophilia, once considered opportunistic, in an apparently healthy female adult.

In Vitro Activity of 22 Antibiotics against Achromobacter Isolates from People with Cystic Fibrosis. Are There New Therapeutic Options?

Bacteria belonging to the genus Achromobacter are increasingly isolated from respiratory samples of people with cystic fibrosis (PWCF). The management of this multidrug-resistant genus is challenging and characterised by a lack of international recommendations, therapeutic guidelines and data concerning antibiotic susceptibility, especially concerning the newer antibiotics. The objective of this study was to describe the antibiotic susceptibility of Achromobacter isolates from PWCF, including susceptibility to new antibiotics. The minimum inhibitory concentrations (MICs) of 22 antibiotics were determined for a panel of 23 Achromobacter isolates from 19 respiratory samples of PWCF. Two microdilution MIC plates were used: EUMDROXF^® plate (Sensititre) and Micronaut-S Pseudomonas MIC^® plate (Merlin) and completed by a third method if necessary (E-test^® or UMIC^®). Among usual antimicrobial agents, the most active was imipenem (70% susceptibility). Trimethoprim-sulfamethoxazole, piperacillin and tigecycline (65%, 56% and 52% susceptibility, respectively) were still useful for the treatment of Achromobacter infections. Among new therapeutic options, β-lactams combined with a β-lactamase-inhibitor did not bring benefits compared to β-lactam alone. On the other hand, cefiderocol appeared as a promising therapeutic alternative for managing Achromobacter infections in PWCF. This study provides the first results on the susceptibility of clinical Achromobacter isolates concerning new antibiotics. More microbiological and clinical data are required to establish the optimal treatment of Achromobacter infections.

Antimicrobial Treatment Strategies for Stenotrophomonas maltophilia: A Focus on Novel Therapies

Stenotrophomonas maltophilia is an urgent global threat due to its increasing incidence and intrinsic antibiotic resistance. Antibiotic development has focused on carbapenem-resistant Enterobacteriaceae, Pseudomonas, and Acinetobacter, with approved antibiotics in recent years having limited activity for Stenotrophomonas. Accordingly, novel treatment strategies for Stenotrophomonas are desperately needed. We conducted a systemic literature review and offer recommendations based on current evidence for a treatment strategy of Stenotrophomonas infection.

In Vitro Antimicrobial and Antibiofilm Activity of S-(-)-Limonene and R-(+)-Limonene against Fish Bacteria

Brazilian fish farming goes together with the emergence of numerous bacterial diseases, with Aeromonas hydrophila being the main bacterial pathogen. As a consequence, antimicrobials are excessively used. Considering that antimicrobials are relatively stable and nonbiodegradable, medicinal plants and their phytochemicals have been used as alternative treatments of bacteriosis in fish farming. Limonene is a monoterpene available in two enantiomers: R-(+)-limonene and S-(-)-limonene. This study analyzed the antibacterial activity of the phytochemicals S-(-)-limonene and R-(+)-limonene against some bacteria isolated from silver catfish (Rhamdia quelen). Furthermore, by means of spectrophotometry and atomic force microscopy, we also investigated the combination therapy of phytochemicals with antimicrobials and their activity in terms of inhibiting biofilm formation. Six clinical isolates and a standard strain were selected for antimicrobial activity testing. Biofilm formation was tested in 96-well plates and nylon cubes. The most sensitive of the strains tested was the A. hydrophila strain (MF 372510). S-(-)-limonene and R-(+)-limonene had high minimum inhibitory concentrations; however, they strongly inhibited A. hydrophila biofilm formation. R-(+)-limonene and S-(-)-limonene had an additive effect when combined with florfenicol and an antagonistic effect with oxytetracycline. In general, the phytochemicals tested showed strong antibiofilm activity against A. hydrophila, and when in combination therapy with florfenicol, they showed an additive effect against the treatment of A. hydrophila.

Interplay between OmpA and RpoN Regulates Flagellar Synthesis in Stenotrophomonas maltophilia

OmpA, which encodes outer membrane protein A (OmpA), is the most abundant transcript in Stenotrophomonas maltophilia based on transcriptome analyses. The functions of OmpA, including adhesion, biofilm formation, drug resistance, and immune response targets, have been reported in some microorganisms, but few functions are known in S. maltophilia. This study aimed to elucidate the relationship between OmpA and swimming motility in S. maltophilia. KJΔOmpA, an ompA mutant, displayed compromised swimming and failure of conjugation-mediated plasmid transportation. The hierarchical organization of flagella synthesis genes in S. maltophilia was established by referencing the Pseudomonas aeruginosa model and was confirmed using mutant construction, qRT-PCR, and functional assays. Distinct from the P. aeruginosa model, rpoN, rather than fleQ and fliA, was at the top of the flagellar regulatory cascade in S. maltophilia. To elucidate the underlying mechanism responsible for ΔompA-mediated swimming compromise, transcriptome analysis of KJ and KJΔOmpA was performed and revealed rpoN downregulation in KJΔOmpA as the key element. The involvement of rpoN in ΔompA-mediated swimming compromise was verified using rpoN complementation, qRT-PCR, and function assays. Collectively, OmpA, which contributes to bacterial conjugation and swimming, is a promising target for adjuvant design in S. maltophilia.

Advances in the Microbiology of Stenotrophomonas maltophilia

Stenotrophomonas maltophilia is an opportunistic pathogen of significant concern to susceptible patient populations. This pathogen can cause nosocomial and community-acquired respiratory and bloodstream infections and various other infections in humans. Sources include water, plant rhizospheres, animals, and foods. Studies of the genetic heterogeneity of S. maltophilia strains have identified several new genogroups and suggested adaptation of this pathogen to its habitats. The mechanisms used by S. maltophilia during pathogenesis continue to be uncovered and explored. S. maltophilia virulence factors include use of motility, biofilm formation, iron acquisition mechanisms, outer membrane components, protein secretion systems, extracellular enzymes, and antimicrobial resistance mechanisms. S. maltophilia is intrinsically drug resistant to an array of different antibiotics and uses a broad arsenal to protect itself against antimicrobials. Surveillance studies have recorded increases in drug resistance for S. maltophilia, prompting new strategies to be developed against this opportunist. The interactions of this environmental bacterium with other microorganisms are being elucidated. S. maltophilia and its products have applications in biotechnology, including agriculture, biocontrol, and bioremediation.

Cystic Fibrosis: Recent Insights into Inhaled Antibiotic Treatment and Future Perspectives

Although new inhaled antibiotics have profoundly improved respiratory diseases in cystic fibrosis (CF) patients, lung infections are still the leading cause of death. Inhaled antibiotics, i.e., colistin, tobramycin, aztreonam lysine and levofloxacin, are used as maintenance treatment for CF patients after the development of chronic Pseudomonas aeruginosa (P. aeruginosa) infection. Their use offers advantages over systemic therapy since a relatively high concentration of the drug is delivered directly to the lung, thus, enhancing the pharmacokinetic/pharmacodynamic parameters and decreasing toxicity. Notably, alternating treatment with inhaled antibiotics represents an important strategy for improving patient outcomes. The prevalence of CF patients receiving continuous inhaled antibiotic regimens with different combinations of the anti-P. aeruginosa antibiotic class has been increasing over time. Moreover, these antimicrobial agents are also used for preventing acute pulmonary exacerbations in CF. In this review, the efficacy and safety of the currently available inhaled antibiotics for lung infection treatment in CF patients are discussed, with a particular focus on strategies for eradicating P. aeruginosa and other pathogens. Moreover, the effects of long-term inhaled antibiotic therapy for chronic P. aeruginosa infection and for the prevention of pulmonary exacerbations is reviewed. Finally, how the mucus environment and microbial community richness can influence the efficacy of aerosolized antimicrobial agents is discussed.

In Vitro Activity and In Vivo Efficacy of Cefiderocol against Stenotrophomonas maltophilia

Cefiderocol is a novel siderophore cephalosporin antibiotic with broad coverage against difficult-to-treat Gram-negative bacteria, including those resistant to carbapenems. Its activity against Stenotrophomonas maltophilia was investigated in vitro against clinical isolates and in lung infection models using strains either resistant (SR202006) or susceptible (SR201934, SR200614) to trimethoprim-sulfamethoxazole. Cefiderocol demonstrated potent in vitro activity against all 217 S. maltophilia clinical isolates tested (MIC50, 0.063 μg/ml; MIC90, 0.25 μg/ml). Cefiderocol also demonstrated low MICs against the trimethoprim-sulfamethoxazole-resistant S. maltophilia strains (i.e., SR202006; MIC, 0.125 μg/ml). In a neutropenic mouse lung infection model, cefiderocol (30 mg/kg body weight and 100 mg/kg) demonstrated a significant, dose-dependent reduction in the lung viable bacteria cell count compared with untreated controls in S. maltophilia infection and was the only antibiotic tested to show a similar significant effect in a trimethoprim-sulfamethoxazole-resistant S. maltophilia infection. In immunocompetent rat lung infection models of S. maltophilia, humanized dosing of cefiderocol (2 g every 8 h) and meropenem (1 g every 8 h) revealed pharmacokinetic profiles similar to those in human subjects, and the humanized cefiderocol dosing significantly reduced the lung viable bacteria cell count compared with baseline controls, which received no intervention. Together, the results from these studies suggest that cefiderocol could provide an effective alternative treatment option for S. maltophilia infections in the lower respiratory tract, particularly strains resistant to empirical antibiotics, such as trimethoprim-sulfamethoxazole or minocycline.

Stenotrophomonas maltophilia: An emerging opportunistic nosocomial pathogen in a tertiary care hospital in Al Batinah North Governorate, Oman

Objectives

Stenotrophomonas maltophilia, a Gram-negative non-fermentative bacillus, has emerged as an important nosocomial pathogen in recent years. It is intrinsically resistant to many antibiotics and has the ability to acquire antibiotic resistance by multiple mechanisms. Treating Stenotrophomonas infections, therefore, is a serious challenge for physicians. This study aimed to investigate the antibiotic susceptibility patterns and risk factors contributing to S. maltophilia infections.

Methods

A retrospective cross-sectional study was conducted at Sohar Hospital in Sohar, Oman. The demographic, clinical and microbiological data of individuals from whom S. maltophilia was isolated between September 2016 and August 2019 were reviewed. Descriptive statistics were presented as frequencies and percentages.

Results

A total of 41 S. maltophilia isolates from clinical specimens of 41 patients were studied. Infection occurred predominantly in males (73%) and the majority of patients (88%) were either ≤5 years old or >60 years old. All inpatients had at least one comorbidity while 50% had more than one. All inpatients were exposed to various medical interventions such as intensive care (44%), mechanical ventilation (41%), haemodialysis (25%), Foley's catheterisation (13%) and central venous lines (6%). Most patients (81%) were in hospital longer than two weeks. The susceptibility rates of S. maltophilia to minocycline (97%), trimethoprim-sulfamethoxazole (93%) and levofloxacin (92%) were high; the rate was lowest for ceftazidime (50%).

Conclusion

S. maltophilia was found to be an important nosocomial opportunistic pathogen. Prolonged hospital stay and exposure to various medical interventions were key factors contributing to the development of infection. Minocycline and ceftazidime were found to be the most and least susceptible drugs, respectively.

Stenotrophomonas maltophilia bacteremia in children: risk factors and mortality rate

Purpose

Stenotrophomonas maltophilia (S. maltophilia) is an opportunistic and nosocomial pathogen that can cause an invasive and fatal infection, particularly in hospitalized and immunocompromised patients. However, little is known about the impact of S. maltophilia bacteremia in pediatric patients. Therefore, we aimed to identify risk factors for mortality, antibiotics susceptibility to S. maltophilia, and mortality rates in pediatric patients with S. maltophilia bacteremia.

Methods

We conducted a retrospective cohort study by identifying all S. maltophilia positive blood cultures in the microbiology laboratory database between January 2007 and December 2018 from hospitalized pediatric patients (age 1–14 years). After identifying patients with S. maltophilia bacteremia, medical charts were reviewed for demographics, clinical data, and outcomes within seven days of bacteremia diagnosis. Risk factors associated with mortality in S. maltophilia bacteremia patients were determined using univariate and multivariate analyses.

Findings

Sixty-eight pediatric patients with S. maltophilia bacteremia were identified. All infections were nosocomial infections, and (88.2%) bacteremia cases were catheter-related bloodstream infections. On multivariate analysis, ICU admission prior to bacteremia episode and neutropenia were the major risk factors associated with mortality. S. maltophilia was the most susceptible to trimethoprim and sulfamethoxazole (TMP/SMX, 94.1%), followed by levofloxacin (85.7%). The overall mortality rate within seven days of S. maltophilia bacteremia diagnosis was 33.8%.

Conclusion

S. maltophilia bacteremia is a devastating emerging infection associated with high mortality among hospitalized children. Therefore, early diagnosis and prompt management based on local susceptibility data are crucial. Various risk factors, especially ICU admission prior to bacteremia episode and neutropenia, are associated with S. maltophilia bacteremia mortality.

Overcoming Challenges to Make Bacteriophage Therapy Standard Clinical Treatment Practice for Cystic Fibrosis

Individuals with cystic fibrosis (CF) are given antimicrobials as prophylaxis against bacterial lung infection, which contributes to the growing emergence of multidrug resistant (MDR) pathogens isolated. Pathogens such as Pseudomonas aeruginosa that are commonly isolated from individuals with CF are armed with an arsenal of protective and virulence mechanisms, complicating eradication and treatment strategies. While translation of phage therapy into standard care for CF has been explored, challenges such as the lack of an appropriate animal model demonstrating safety in vivo exist. In this review, we have discussed and provided some insights in the use of primary airway epithelial cells to represent the mucoenvironment of the CF lungs to demonstrate safety and efficacy of phage therapy. The combination of phage therapy and antimicrobials is gaining attention and has the potential to delay the onset of MDR infections. It is evident that efforts to translate phage therapy into standard clinical practice have gained traction in the past 5 years. Ultimately, collaboration, transparency in data publications and standardized policies are needed for clinical translation.

It's Not Easy Being Green: A Narrative Review on the Microbiology, Virulence and Therapeutic Prospects of Multidrug-Resistant Pseudomonas aeruginosa

Pseudomonas aeruginosa is the most frequent cause of infection among non-fermenting Gram-negative bacteria, predominantly affecting immunocompromised patients, but its pathogenic role should not be disregarded in immunocompetent patients. These pathogens present a concerning therapeutic challenge to clinicians, both in community and in hospital settings, due to their increasing prevalence of resistance, and this may lead to prolonged therapy, sequelae, and excess mortality in the affected patient population. The resistance mechanisms of P. aeruginosa may be classified into intrinsic and acquired resistance mechanisms. These mechanisms lead to occurrence of resistant strains against important antibiotics-relevant in the treatment of P. aeruginosa infections-such as β-lactams, quinolones, aminoglycosides, and colistin. The occurrence of a specific resistotype of P. aeruginosa, namely the emergence of carbapenem-resistant but cephalosporin-susceptible (Car-R/Ceph-S) strains, has received substantial attention from clinical microbiologists and infection control specialists; nevertheless, the available literature on this topic is still scarce. The aim of this present review paper is to provide a concise summary on the adaptability, virulence, and antibiotic resistance of P. aeruginosa to a readership of basic scientists and clinicians.

Adherence to Guidelines for Assessment and Empiric Antibiotics Recommendations for Community-Acquired Pneumonia at Ambo University Referral Hospital: Prospective Observational Study

OBJECTIVE

The high incidence and substantial morbidity and mortality associated with community-acquired pneumonia necessitate an accurate assessment and appropriate management of patients. This observational prospective study aimed to evaluate the physicians' adherence to the Ethiopian Standard Treatment Guideline for assessment and an empiric antibiotic selection for Community-acquired pneumonia.

RESULTS

The study indicated that the pneumonia severity assessment tool, CURB-65 score, was never used. Of 141 patients referred to an admitting diagnosis of severe community-acquired pneumonia, only 50 were subsequently found to satisfy the guideline criteria, over-diagnosis of 41.9%. Large proportions of the participants (130, 60%) were prescribed antibiotics in the last three months. The most commonly prescribed single antibiotic was Ceftriaxone (47, 21.7%), while ceftriaxone plus azithromycin was the most common combination, 110 (50.7%). In general, the extent of non-adherence to the national guideline for the use of antibiotics was 36.4%. In conclusion, the use of CRB65 scores was uncommon in the study setting. Poor adherence to Ethiopian Standard Treatment Guideline regarding the decision of hospital admission (41.9%) and the antimicrobial selection (36.4%) was determined.

Molecular epidemiology and risk factors of Stenotrophomonas maltophilia infections in a Chinese teaching hospital

Background

Stenotrophomonas maltophilia (S. maltophilia) is an important opportunistic pathogen that can be isolated in hospitals. With the abuse of broad spectrum antibiotics and invasive surgical devices, the rate of S. maltophilia infection is increasing every year. This study was an epidemiological analysis of the clinical and molecular characteristics of S. maltophilia infection in a Chinese teaching hospital. The goal was to obtain a comprehensive understanding of the status of S. maltophilia infection to provide strong epidemiological data for the prevention and treatment of S. maltophilia infection.

Results

A total of 93 isolates from Renji Hospital affiliated with the Shanghai Jiaotong University School of Medicine were included, in which 62 isolates were from male patients. In addition, 81 isolates were isolated from sputum samples. A total of 86 patients had underlying diseases. All patients received antibiotics. Multilocus sequence typing (MLST) analysis indicated that 61 different sequence types (STs) were found (including 45 novel STs), and MLST did not show significantly dominant STs. Pulsed field gel electrophoresis (PFGE) results showed that 93 isolates could be divided into 73 clusters, and they also showed weak genetic linkages between isolates. The resistant rates to trimethoprim/sulfamethoxazole (TMP/SMX) and levofloxacin were 9.7 and 4.3%, respectively, and all isolates were susceptible to minocycline. Four virulence gene’s loci Stmpr1, Stmpr2, Smf-1, and Smlt3773 were positive in 79.6, 91.4, 94.6, and 52.7% of the isolates, respectively. Three biofilm genes rmlA, spgM, and rpfF were positive in 82.8, 92.5, and 64.5% of the isolates, respectively. Mean biofilm forming level of OD₄₉₂ was 0.54 ± 0.49. We did not find any significant difference between different genders and different age-groups. We retrospectively analyzed data from patients in the intensive care unit (ICU) and the control group. The independent risk factors of those who were infected in the ICU included immunosuppression and the increased antibiotic usage.

Conclusions

Most of the patients had prior medical usage histories and baseline diseases. The positive rate of virulence genes was high, the drug resistance rate of S. maltophilia was low, and the biofilm formation ability was strong. The increased use of antibiotics was an independent risk factor for S. maltophilia infection, which should receive more attention. No obvious clonal transmissions were found in the same departments.

Successful treatment of pulmonary haemorrhage and acute respiratory distress syndrome caused by fulminant Stenotrophomonas maltophilia respiratory infection in a patient with acute lymphoblastic leukaemia - case report

Background

Stenotrophomonas maltophilia-induced pulmonary haemorrhage is considered a fatal infection among haematological patients. The outcome can be explained by the patients’ immunity status and late diagnosis and treatment.

Case presentation

We present the rare case of successful outcome in a 61-year-old female who developed alveolar haemorrhage and acute respiratory distress syndrome 8 days after a chemotherapy session for her acute lymphoblastic leukaemia, in the context of secondary bone marrow aplasia. Stenotrophomonas maltophilia was isolated in sputum culture. The patient benefitted from early empirical treatment with colistin followed by trimethoprim/sulfamethoxazole, according to the antibiogram. Despite a severe initial clinical presentation in need of mechanical ventilation, neuromuscular blocking agents infusion, and ventilation in prone position, the patient had a favourable outcome and was discharged from intensive care after 26 days.

Conclusions

Stenotrophomonas maltophilia severe pneumonia complicated with pulmonary haemorrhage is not always fatal in haematological patients. Empirical treatment of multidrug-resistant Stenotrophomonas maltophilia in an immunocompromised haematological patient presenting with hemoptysis should be taken into consideration.

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.

Whole Genome Sequencing and Characterization of Multidrug-Resistant (MDR) Bacterial Strains Isolated From a Norwegian University Campus Pond

The presence of extended-spectrum β-lactamase (ESBL)-producing bacteria in environmental sources has been reported worldwide and constitutes a serious risk of community-acquired infections with limited treatment options. The current study aimed to explore the presence of these worrisome bacteria in a pond located at the Norwegian University of Life Sciences in Ås, Norway. A total of 98 bacterial isolates survived growth on selective chromogenic media and were identified by 16S rRNA Sanger sequencing. All strains were evaluated for the presence of the most commonly found β-lactamases and ESBLs in clinical settings (bla_CTX–M groups 1, 2, and 9, bla_CMY, bla_SHV, and bla_TEM) and carbapenemases (bla_IMP, bla_KPC, bla_NDM, bla_OXA, bla_SFC1, bla_VIM) through multiplex PCR. A total of eight strains were determined to contain one or more genes of interest. Phenotypic resistance to 18 antimicrobial agents was assessed and isolates were subjected to whole genome sequencing through a combination of Oxford Nanopore’s MinION and Illumina’s MiSeq. Results revealed the presence of β-lactamase and ESBL-producing Escherichia coli, Klebsiella pneumoniae, Stenotrophomonas maltophilia, and a Paraburkholderia spp. Identified β-lactamases and ESBLs include bla_CTX–M, bla_TEM, bla_CMY, bla_SHV and a possible bla_KPC-like gene, with both documented and novel sequences established. In addition, two inducible β-lactamases were found, a class A β-lactamase (L1) and a cephalosporinase (L2). All strains were determined to be multidrug resistant and numerous resistance genes to non-β-lactams were observed. In conclusion, this study demonstrates that environmental sources are a potential reservoir of clinically relevant ESBL-producing bacteria that may pose a health risk to humans upon exposure.

Etiology of Community-Acquired Pneumonia Requiring Hospital Admission in Adults with and Without Cancers: A Single-Center Retrospective Study in China

Background

The etiology and distribution of community-acquired pneumonia (CAP) vary periodically and geographically. The clinical evaluation of CAP among patients with cancers remains unknown.

Patients and Methods

This retrospective hospital-based study on adult CAP was conducted in Tang Du Hospital, China, from September 2018 to August 2019. The demographic characteristics, clinical manifestations and laboratory data were extracted from medical records and compared between CAP patients with and without cancers. Univariable and multivariable logistic regression methods were used to explore risk factors associated with CAP patients with and without cancers.

Results

Data from 149 CAP patients with cancers and 268 CAP patients without cancers were analyzed. Patients without cancers were more likely to show fever, cough and yellow sputum, higher level of neutrophil count than the cancer patients. Klebsiella pneumoniae (K. pneumoniae 14.77% vs 9.33%, p = 0.093) and Streptococcus pneumoniae (S. pneumoniae 16.11% vs 11.57%, p = 0.189) were among the most commonly encountered pathogens in both the groups. Pseudomonas aeruginosa (P. pneumoniae 26.50% vs 11.41%, p < 0.001), Mycoplasma pneumoniae (M. pneumoniae 8.21% vs 1.34%, p = 0.003), and filamentous fungi (10.82% vs 4.7%, p = 0.033) were predominant in CAP patients without cancers. Haemophilus influenzae (H. influenzae 22.15% vs 14.18%, p = 0.038) and methicillin-resistant Staphylococci (MRS 23.49 vs 15.68, p = 0.049) were more prevalent for CAP cancer patients. Certain pathogens were increasing in a cold season. In patients without cancers, MRS, H. influenzae and P. aeruginosa were associated with central nervous system (CNS) disease, connective tissue disease, bronchiectasis, respectively. In addition, healthy adults were likely to be infected with M. pneumoniae showing fever.

Conclusion

CAP patients with cancers had atypical clinical manifestations and showed no distinct increase in inflammatory markers. The predominant pathogens differed as well as similar between the CAP patients with and without cancers. Certain pathogens follow a seasonal pattern. CNS disease, connective tissue disease and bronchiectasis were associated with the predominant pathogens in patients without cancers.

Raoultella ornithinolytica: Emergence and Resistance

Raoultella ornithinolytica is an encapsulated Gram-negative, oxidase-negative, catalase-positive, aerobic, non-motile rod that belongs to the Enterobacteriaceae family. This bacterium was initially classified in the genus Klebsiella as Klebsiella ornithinolytica, until the creation of the genus Raoultella in 2001. R. ornithinolytica is usually found in water environments and soil, and due to its ability to convert histidine to histamine, it has been associated with histamine poisoning in humans. R. ornithinolytica is an emerging entity in human infections, with several reports of virulent infections in comorbid at-risk patients. Increasing reports are potentially due to better and more precise identification tools. The objective of this article is to provide a comprehensive review of reported cases of R. ornithinolytica infections, the emergent virulence of described multiresistant strains, and an overview of currently used identification methods.

Carbapenem-Resistant but Cephalosporin-Susceptible Pseudomonas aeruginosa in Urinary Tract Infections: Opportunity for Colistin Sparing

This paper briefly reports the occurrence and epidemiology of carbapenem-resistant but cephalosporin-susceptible (Car-R/Ceph-S) Pseudomonas aeruginosa isolates from urinary tract infections (UTIs) in a tertiary-care hospital in the Southern Region of Hungary, and the phenotypic characterization of the possible resistance mechanisms in these isolates. Isolates and data were collected regarding P. aeruginosa UTIs corresponding to the period between 2008 and 2017. Susceptibility testing was performed using the Kirby–Bauer disk diffusion method; minimum inhibitory concentrations (MICs) of the isolates were determined using E-tests. The phenotypic detection of ampicillin C-type (AmpC) β-lactamases, efflux pump overexpression and carbapenemase production was also performed. P. aeruginosa represented n = 575 (2.72% ± 0.64%) from outpatient, and n = 1045 (5.43% ± 0.81%) from inpatient urinary samples, respectively. Based on the disk diffusion test, n = 359 (22.16%) were carbapenem-resistant; in addition to carbapenems, n = (64.34%) were also resistant to ciprofloxacin; n = (60.17%) to gentamicin/tobramycin; n = (58.51%) to levofloxacin; and n = (27.57%) to amikacin. From among the carbapenem-resistant isolates, n = 56 (15.59%) isolates were multidrug-resistant, while n = 16 (4.46%) were extensively drug-resistant. From among the Car-R/Ceph-S isolates (n = 57), overexpression of AmpC was observed in n = 7 cases (12.28%); carbapenemase production in n = 4 (7.02%); while overexpression of efflux pumps was present in n = 31 (54.39%) isolates. To spare last-resort agents, e.g., colistin, the use of broad-spectrum cephalosporins or safe, alternative agents should be considered in these infections.

Activity of Potential Alternative Treatment Agents for Stenotrophomonas maltophilia Isolates Nonsusceptible to Levofloxacin and/or Trimethoprim-Sulfamethoxazole

Stenotrophomonas maltophilia is difficult to treat due to the production of multiple intrinsic and acquired mechanisms of resistance. Trimethoprim-sulfamethoxazole (TMP-SMZ) and the fluoroquinolones have traditionally been considered the drugs of choice but are plagued by increasing resistance and adverse drug effects. The objective of this study was to evaluate the in vitro activities of 12 clinically relevant antimicrobials against clinical S. maltophilia isolates nonsusceptible to levofloxacin and/or TMP-SMZ. A diverse panel of 41 clinical S. maltophilia isolates collected through the SENTRY Antimicrobial Surveillance Program from 2008 to 2018 was evaluated against ceftazidime, ceftazidime-avibactam, chloramphenicol, delafloxacin, levofloxacin, moxifloxacin, eravacycline, minocycline, omadacycline, polymyxin B, and tigecycline. MICs were determined in triplicate via reference broth microdilution and interpreted according to CLSI guidelines where available. MIC distributions and susceptibilities were also compared across infection type, acquisition setting, and geographic origin. Susceptibilities to levofloxacin and TMP-SMZ were 29.3% and 36.6%, respectively. Minocycline displayed the highest susceptibility rate overall (92.7%) and the lowest MIC₉₀ value (4 mg/liter) of any of the 12 agents tested. Only 3 isolates were resistant to levofloxacin, TMP-SMZ, and minocycline. Polymyxin B and tigecycline were the second most active agents. No significant differences were observed in MIC distributions across the 3 strata evaluated. These data demonstrate that few antimicrobials, old or new, maintain reliable activity against resistant S. maltophilia The role of minocycline in the treatment of infections due to S. maltophilia warrants further clinical investigation given its potent in vitro activity and favorable adverse effect profile.

Resistance Levels and Epidemiology of Non-Fermenting Gram-Negative Bacteria in Urinary Tract Infections of Inpatients and Outpatients (RENFUTI): A 10-Year Epidemiological Snapshot

Background: Urinary tract infections (UTIs) are one of the most common infections in the human medicine, both among outpatients and inpatients. There is an increasing appreciation for the pathogenic role of non-fermenting Gram-negative bacteria (NFGNBs) in UTIs, particularly in the presence of underlying illnesses. Methods: The study was carried out using data regarding a 10-year period (2008-2017). The antimicrobial susceptibility testing was performed using the disk diffusion method, E-tests, and broth microdilution. Results: NFGNB represented 3.46% ± 0.93% for the outpatients, while 6.43% ± 0.81% of all positive urine samples for the inpatients (p < 0.001). In both groups, Pseudomonas spp. (78.7% compared to 85.1%) and Acinetobacter spp. (19.6% compared to 10.9%), were the most prevalent. The Acinetobacter resistance levels were significantly higher in inpatients isolates (p values ranging between 0.046 and <0.001), while the differences in the resistance levels of Pseudomonas was not as pronounced. The β-lactam-resistance levels were between 15-25% and 12-28% for the Acinetobacter and Pseudomonas spp., respectively. 4.71% of Acinetobacter and 1.67% of Pseudomonas were extensively drug resistant (XDR); no colistin-resistant isolates were recovered. Conclusions: Increasing resistance levels of the Acinetobacter spp. from 2013 onward, but not in the case of the Pseudomonas spp. Although rare, the drug resistant NFGNB in UTIs present a concerning therapeutic challenge to clinicians with few therapeutic options left.