Emerging importance of multidrug-resistant Acinetobacter species and Stenotrophomonas maltophilia as pathogens in seriously ill patients: geographic patterns, epidemiological features, and trends in the SENTRY Antimicrobial Surveillance Program (1997-1999)

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.

Risk factors for bacteremia and mortality due to multidrug-resistant Acinetobacter baumannii: a retrospective study

This research aimed to determine the relationships between the risk factors for nosocomial multidrug-resistant Acinetobacter baumannii (MDRAB) bacteremia and associated mortality. We analyzed 144 patients treated for A. baumannii bacteremia, including 120 patients with MDRAB bacteremia, from March 2015 to March 2020, in this retrospective study. The overall bacteremia-related mortality rate was 48.6%. The mortality rates were 25.0% and 53.3% for non-MDRAB and MDRAB bacteremia, respectively. Risk factors for the development of MDRAB bacteremia were prior use of cephalosporins [odds ratio (OR): 8.62; P < .001], carbapenems (OR: 15.04; P < .001), or quinolones (OR: 5.02; P = .040); indwelling urinary catheters (OR: 21.38; P < .001); and respiratory tract as the source of bacteremia (OR: 75.33; P < .001). Patients with elective surgeries were inclined to develop non-MDRAB bacteremia (OR: 0.45; P = .029). High scores in the Acute Physiology and Chronic Health Evaluation II (OR: 1.321; P < .001) and Sequential Organ Failure Assessment (OR: 1.326; P < .001) were risk factors for mortality from MDRAB infection. In summary, higher mortality rates occur in patients with MDRAB bacteremia, and risk factors include prior use of cephalosporins, carbapenems, or quinolones. Urinary catheters and the respiratory tract as sources of the infection increase the risk of MDRAB bacteremia.

The microbiology and pathogenesis of nonfermenting Gram-negative infections

PURPOSE OF REVIEW

This review provides an overview of most recent evidence about pathogenesis traits and virulence factors contributing to successful colonization or infection by P. aeruginosa , A. baumannii , S. maltophilia and B. cepacia complex, among the most clinically relevant nonfermenting Gram-negative bacteria (NFGNB).

RECENT FINDINGS

The growing clinical importance of NFGNB as important opportunistic pathogens causing difficult-to-treat infections in a fragile patients' population in stressed by numerous studies. Identification of novel virulence factors and deciphering of their mechanisms of action have greatly furthered our understanding of NFGNB pathogenesis, revealing that each pathogen-specific armamentarium of virulence factors (adhesins, motility, capsule, biofilm, lipopolysaccharide, exotoxins, exoenzymes, secretion systems, siderophores) can be likely responsible for the difference in the pathophysiology even in the context of a similar infection site. Emerging evidence of the immunomodulatory effect of some virulence factors is also acknowledged.

SUMMARY

NFGNB continue to be a serious global problem as cause of life-threatening opportunistic infections, owing to a highly heterogeneous content of virulence factors and their extensive number of intrinsic resistance mechanisms. Further efforts in development of novel effective antimicrobials and of alternative strategies targeting key virulence factors are warranted.

Soil-specific responses in the antibiotic resistome of culturable Acinetobacter spp. and other non-fermentative Gram-negative bacteria following experimental manure application

Acinetobacter spp. and other non-fermenting Gram-negative bacteria (NFGNB) represent an important group of opportunistic pathogens due to their propensity for multiple, intrinsic, or acquired antimicrobial resistance (AMR). Antimicrobial resistant bacteria and their genes can spread to the environment through livestock manure. This study investigated the effects of fresh manure from dairy cows under antibiotic prophylaxis on the antibiotic resistome and AMR hosts in microcosms using pasture soil. We specifically focused on culturable Acinetobacter spp. and other NFGNB using CHROMagar Acinetobacter. We conducted two 28-days incubation experiments to simulate natural deposition of fresh manure on pasture soil and evaluated the effects on antibiotic resistance genes (ARGs) and bacterial hosts through shotgun metagenomics. We found that manure application altered the abundance and composition of ARGs and their bacterial hosts, and that the effects depended on the soil source. Manure enriched the antibiotic resistome of bacteria only in the soil where native bacteria had a low abundance of ARGs. Our study highlights the role of native soil bacteria in modulating the consequences of manure deposition on soil and confirms the potential of culturable Acinetobacter spp. and other NFGNB to accumulate AMR in pasture soil receiving fresh manure.

Looking for Stenotrophomonas maltophilia treatment: in vitro activity of ceftazidime/avibactam alone and in combination with aztreonam

During the Sars-Cov-2 pandemic, Stenotrophomonas maltophilia (S.maltophilia) secondary pulmonary infections have increased, especially in critically ill patients, highlighting the need for new therapeutic options. Trimethoprim-sulfamethoxazole (SXT) is the treatment of choice but the increase of resistant strains or adverse drug reactions limited its clinical use. Recently ceftazidime/avibactam (CZA) has been approved for the treatment of multi drug resistant (MDR) Gram-negative bacteria infections, including hospital acquired pneumonia. The aim of this study was to evaluate the in vitro activity of ceftazidime/avibactam (CZA) alone and in combination with aztreonam (ATM) against S. maltophilia clinical isolates by E-test method. Susceptibility of SXT and levofloxacin (LEV) was also investigated. Our results showed 22% of resistance to CZA, 2% to SXT and 26% to LEV. CZA in combination with ATM demonstrated synergistic activity against 86% of the strains, including all those resistant to CZA. The combination of CZA with ATM provides a new therapeutic option for the treatment of severe respiratory infections in critically ill patients.

Jojan: a novel virus that lyses Stenotrophomonas maltophilia from dog

Stenotrophomonas maltophilia is a Gram-negative bacterium widely distributed in the environment and associated with nosocomial infections, pneumonia, and bacteremia in humans and other mammals. We have isolated and sequenced a new virus that lyses the S. maltophilia strain from a dog skin. The virus has a siphovirus-like morphology and a linear dsDNA genome 60,804 pb in length with terminal repeats, four tRNA genes, and 111 putative proteins. The annotated genes resemble the corresponding genes of some siphoviruses, but the unique genome arrangement and limited similarity of the encoded proteins suggest that this virus does not belong to any known genus. The virus uses zinc metallopeptidase for lysis of its host. This enzyme is active in the presence of Zn2+ or Mg2+ ions and maintains its bactericidal activity up to 50 °C. Both the virus itself and the endolysin specifically degrade only the host bacterial strain.

Acinetobacter baumannii Bloodstream Infections: A Nationwide Study in Israel

Acinetobacter baumannii (Ab) bloodstream infections (BSIs) are a major public health concern and associated with high mortality. We describe the nationwide incidence, antimicrobial resistance, and mortality of Ab-BSI in Israel using laboratory-based BSI surveillance data from January 2018 to December 2019. During the study period, there were 971 Ab-BSI events (508 in 2018 and 463 in 2019), with an average annual incidence of 8.08/100,000 population. The median age of patients was 72 (IQR 62-83), and 56.4% were males. Two-thirds of Ab-BSI events were hospital-onset (HO), with median day of onset 16 (IQR 9-30). HO-BSI incidence was 0.62/10,000 patient-days (rate per 10,000 patient-days: 2.78, 1.17, and 0.2 for intensive care, medical, and surgical wards, respectively). Carbapenem susceptibility was 23.4%; 41.4% and 14.9% in community and HO events, respectively. The 14-day, 30-day, and 1-year mortality were 51.2%, 59.3%, and 81.4%, respectively. Carbapenem-resistant Ab-BSI were associated with a significantly higher 14-day, 30-day, and 1-year mortality (p < 0.001 for all). In the multivariable model, age (aHR 1.02) and carbapenem resistance (aHR 3.21) were independent predictors of 30-day mortality. In conclusion, Ab-BSIs pose a significant burden with high mortality, especially associated with antimicrobial resistance. Attention should be focused on prevention and improving treatment.

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.

Upraising Stenotrophomonas maltophilia in Critically Ill Patients: A New Enemy?

Stenotrophomonas maltophilia (S. maltophilia), an important pathogen in immuno-compromised patients, has recently gained attention in patients admitted in intensive care units (ICU). We sought to investigate clinical features of infections caused by S. maltophilia in ICU patients and identify risk factors for mortality. We conducted a retrospective study in two multivalent non-COVID-19 ICUs of tertiary-teaching hospitals in Greece and Spain, including patients with isolated S. maltophilia from at least one clinical specimen along with clinical signs of infection. A total of 103 patients (66% male) were analyzed. Median age was 65.5 (54–73.3) years and mean APACHE II and SOFA scores upon ICU admission were 18.36 (±7.22) and 18.17 (±6.95), respectively. Pneumonia was the predominant clinical syndrome (72.8%), while 22% of cases were among hemato/oncology patients. Crude 28-day mortality rate was 54.8%, even though, 14-day clinical and microbiological response was 96%. Age, APACHE II on ICU admission, hemato-oncologic disease, and multi-organ failure were initially identified as potential predictors of mortality. In the multivariable analysis, only increasing age and hemato-oncologic disease were shown to be independent risk factors for 28-day mortality. High all-cause mortality was observed in critically ill patients with predominantly respiratory infections by S. maltophilia, despite initial clinical and laboratory response after targeted treatment. The study elucidates a potentially worrisome emerging pathogen in the ICU.

Trends in Stenotrophomonas maltophilia antibiotic resistance rates in the United States Veterans Affairs Health System

Introduction. Stenotrophomonas maltophilia is an important multidrug-resistant Gram-negative pathogen. While largely a hospital-acquired pathogen, there have been increasing reports of the pathogen in the community.

Gap Statement. Trends in S. maltophilia prevalence and resistance rates that include outpatient isolates are unknown.

Aim. We described recent trends in prevalence and resistance of S. maltophilia in the national Veterans Affairs (VA) Healthcare system.

Methodology. The study identified positive S. maltophilia clinical cultures among VA adult patients from 2010 to 2018 across all VA hospitals, long-term care facilities/units, and outpatient settings. Annual S. maltophilia resistance rates were evaluated. Multidrug resistant (MDR) was defined as resistance to sulfamethoxazole/trimethoprim (SMX/TMP) and minocycline or levofloxacin. Time trends were assessed with regression analyses to estimate annual average percent changes (AAPC) with 95 % confidence intervals using Joinpoint software.

Results. Over the 9 year study period, 18 285  S . maltophilia cultures were identified (57 % hospital, 3 % long-term care, 40 % outpatient). The most common source of S. maltophilia cultures were respiratory cultures (34.6 %) followed by urine cultures (30.4 %). In VA hospitals and long-term care facilities, the number of S. maltophilia cultures decreased significantly (by 5.4% and 8.4 % per year respectively). Overall, 3.1 % of isolates were MDR which remained stable over the study period. Resistance to other antibiotics assessed mostly remained stable, except SMX/TMP resistance decreased significantly by 8.5 % (2010, 15 %; 2018, 6 %) per year in VA hospitals.

Conclusion. While previous work has recognized S. maltophilia as primarily a nosocomial pathogen, the present study found that 40 % of cultures collected were among outpatients. Between 2010 and 2018, the number of positive S. maltophilia cultures decreased significantly in the national VA Healthcare System. Resistance to SMX/TMP decreased over the study period in VA hospitals and now more closely reflects previously reported resistance rates worldwide (0–10 %). MDR S. maltophilia remained stable and low in the national VA Healthcare System.

Activity of Delafloxacin and Levofloxacin against Stenotrophomonas maltophilia at Simulated Plasma and Intrapulmonary pH Values

Fluoroquinolones have become a popular treatment option for Stenotrophomonas maltophilia infections. Although levofloxacin is most commonly used, delafloxacin demonstrates comparable in vitro activity when evaluated under standard susceptibility testing conditions at neutral pH. At acidic pH, the activity of the anionic delafloxacin is improved, while the activity of the zwitterionic levofloxacin is reduced. Because the human respiratory tract has a pH of ~6.6 and is the most common site of S. maltophilia infection, it is vital to understand the activity of these agents in this environment. Therefore, levofloxacin and delafloxacin were tested against clinical S. maltophilia isolates via broth microdilution testing (n = 37) and time-kill analysis (n = 5) in neutral cation-adjusted Mueller-Hinton broth (CAMHB) (pH 7.3) and acidic CAMHB (aCAMHB) (pH 6.5). In CAMHB, MIC50 values were similar between levofloxacin and delafloxacin (8 mg/L versus 8 mg/L). In aCAMHB, levofloxacin MICs did not change, while delafloxacin MICs decreased by a median of 4 log2 dilutions (MIC50 values of 8 mg/L versus 0.25 mg/L). In time-kill analyses, levofloxacin and delafloxacin at the maximum drug concentration for the free drug (fCmax) were bactericidal against 3 and 2 isolates in CAMHB, respectively. In aCAMHB, levofloxacin was not bactericidal against any isolate, while delafloxacin was bactericidal against the same 2 isolates. Relative to CAMHB, levofloxacin activity was reduced by 2.5 log10 CFU/mL in aCAMHB, whereas delafloxacin activity was increased 2.7 log10 CFU/mL. Although the bactericidal activity of levofloxacin against S. maltophilia was attenuated in an acidic environment in this study, the increased potency of delafloxacin at pH 6.5 did not translate into improved bactericidal activity in time-kill analyses, compared to pH 7.3. IMPORTANCE Stenotrophomonas maltophilia most often infects the lungs, where the physiologic environment is naturally slightly acidic (pH ~6.6), compared to most parts of the body (such as the bloodstream), which have neutral pH values (~7.4). Pneumonia due to S. maltophilia is often treated with the antibiotic levofloxacin, despite the activity of levofloxacin being known to be impaired at acidic pH. Unfortunately, currently available methods for susceptibility testing of levofloxacin against S. maltophilia are performed at a neutral pH and therefore may not accurately represent the activity of levofloxacin at the site of infection in the lungs. A similar but newer antibiotic in the same class as levofloxacin, namely, delafloxacin, is not affected by being in an acidic environment and may actually work better at lower pH values. Therefore, the purpose of this study was to investigate whether one drug might be better than the other in this setting by testing each agent's ability to kill S. maltophilia at pH 7.3 and pH 6.5. These findings could then be used to design confirmatory studies that may ultimately impact which drug is given to patients with lung infections due to S. maltophilia.

The effect of photodynamic therapy using Radachlorin on biofilm-forming multidrug-resistant bacteria

Objectives

This study aimed to test the effect of photodynamic therapy (PDT) on the inhibition and removal of biofilms containing multidrug-resistant Acinetobacter baumannii.

Methods

Using multidrug-resistant A. baumannii strains, an antibiotic susceptibility test was performed using the Gram-negative identification card of the Vitek 2 system (bioMérieux Inc., France), as well as an analysis of resistance genes, the effects of treatment with a light-emitting diode (LED) array using Radachlorin (RADA-PHARMA Co., Ltd., Russia), and transmission and scanning electron microscopy to confirm the biofilm-inhibitory effect of PDT.

Results

The antibiotic susceptibility test revealed multiple resistance to the antibiotics imipenem and meropenem in the carbapenem class. A class-D–type β-lactamase was found, and OXA-23 and OXA-51 were found in 100% of 15 A. baumannii strains. After PDT using Radachlorin, morphological observations revealed an abnormal structure due to the loss of the cell membrane and extensive morphological changes, including low intracellular visibility and small vacuoles attached to the cell membrane.

Conclusion

PDT involving a combination of LED and Radachlorin significantly eliminated the biofilm of multidrug-resistant A. baumannii. Observations made using electron microscopy showed that PDT combining LED and Radachlorin was effective. Additional studies on the effective elimination of biofilms containing multidrug-resistant bacteria are necessary, and we hope that a treatment method superior to sterilization with antibiotics will be developed in the future.

Risk Factors for Mortality in Hospitalized Patients with Stenotrophomonas maltophilia Bacteremia

Objective

Stenotrophomonas maltophilia (S. maltophilia) is an opportunistic and nosocomial pathogen with high mortality. And it has intrinsic resistance to a number of antibiotics classes. In this study, we investigated risk factors for death due to S. maltophilia bacteremia.

Methods

A retrospective cohort study was conducted at a tertiary-care hospital in Beijing, China. The patients from the hospital database with S. maltophilia bacteremia between January 2011 and December 2020 were investigated. Univariate and multivariate analyses were performed to identify factors associated with mortality.

Results

51 patients with S. maltophilia bacteremia were identified. The mortality rate was 37.3%. Based on the univariate analysis, pulmonary disease (P=0.019), chronic kidney disease (P=0.014), shock (P=0.002), foley catheter (P=0.011), the Acute Physiology and Chronic Health Evaluation II (APACHE II) score (P<0.001), procalcitonin (PCT) (P=0.045) and using antifungal agent (P=0.033) were significantly related to mortality. Based on the multivariate analysis, the APACHE II score (odds ratio [OR] =1.211; 95% confidence interval [CI]: 1.061, 1.382; P=0.005) was independent factor associated with mortality. S. maltophilia was the most susceptible to minocycline (94.7%), followed by trimethoprim and sulfamethoxazole (TMP/SMX, 92.2%).

Conclusion

Our findings suggested that the APACHE II score was a significantly independent predictor in S. maltophilia bacteremia patients. The use of TMP/SMX or minocycline might be the first choice for the treatment of S. maltophilia bacteremia.

Bacterial Signatures of Cerebral Thrombi in Large Vessel Occlusion Stroke

It is important to understand the microbial features of the cerebral thrombus and its clinical relevance in stroke patients, of which data were scarce. We aimed to investigate the microbial features of cerebral thrombi retrieved via thrombectomy in stroke patients with large vessel occlusion (LVO) and their correlations with 3-month mortality. In a prospective cohort study, thrombus samples were collected during mechanical thrombectomy in LVO stroke patients with successful revascularization at a tertiary hospital. Oral, fecal, and isolated plasma samples were collected within 12 h of admission. The microbial compositions of all samples were compared using 16S rRNA gene amplicon next-generation sequencing. Fluorescent in situ hybridization (FISH) was used to detect bacteria in thrombus samples. The primary outcome was 3-month mortality. Perioperative adverse events (AEs) within 48 h were also recorded. Bacterial DNA was detected in 96.2% of thrombus samples from 104 patients, and clusters of bacterial signals were seen in the thrombi with FISH. Compared with fecal and oral samples, the thrombus microbiota was mainly characterized by excessive enrichment of Proteobacteria, mainly originating from plasma. The bacterial concentrations, dominant bacteria, and distribution patterns differed in thrombi obtained from cardioembolic and large-artery atherosclerotic strokes. Higher abundances of Acinetobacter and Enterobacteriaceae were associated with a higher risk of perioperative AEs, and a higher abundance of Acinetobacter was independently associated with a higher risk of 90-day mortality. This study demonstrated the presence of bacteria in cerebral thrombi retrieved with thrombectomy in LVO strokes, with some bacteria associated with patients’ prognoses.

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.

Characterisation of Bacteriophage vB_SmaM_Ps15 Infective to Stenotrophomonas maltophilia Clinical Ocular Isolates

Recent acknowledgment that multidrug resistant Stenotrophomonas maltophilia strains can cause severe infections has led to increasing global interest in addressing its pathogenicity. While being primarily associated with hospital-acquired respiratory tract infections, this bacterial species is also relevant to ophthalmology, particularly to contact lens-related diseases. In the current study, the capacity of Stenotrophomonas phage vB_SmaM_Ps15 to infect ocular S. maltophilia strains was investigated to explore its future potential as a phage therapeutic. The phage proved to be lytic to a range of clinical isolates collected in Australia from eye swabs, contact lenses and contact lens cases that had previously shown to be resistant to several antibiotics and multipurpose contact lenses disinfectant solutions. Morphological analysis by transmission electron microscopy placed the phage into the Myoviridae family. Its genome size was 161,350 bp with a G + C content of 54.2%, containing 276 putative protein-encoding genes and 24 tRNAs. A detailed comparative genomic analysis positioned vB_SmaM_Ps15 as a new species of the Menderavirus genus, which currently contains six very similar globally distributed members. It was confirmed as a virulent phage, free of known lysogenic and pathogenicity determinants, which supports its potential use for the treatment of S. maltophilia eye infections.

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.

Chlorinated cyanurates and potassium salt of peroxymonosulphate as antimicrobial and antibiofilm agents for drinking water disinfection

The understanding of microbial susceptibility to disinfectants is an important step to provide drinking water (DW) of adequate microbiological quality. In drinking water distribution systems (DWDS) the application of disinfectants is the main approach to control microorganisms. Although chlorine has been commonly used for DW treatment, the increase of microbial resistance and the production of harmful disinfection by-products promote the necessity to seek new alternatives. This study evaluated the antimicrobial activity of sodium dichloroisocyanurate (NaDCC), trichloroisocyanuric acid (TCCA), and pentapotassium bis(peroxymonosulphate) bis(sulphate) (OXONE) against two emerging pathogens isolated from DW, Acinetobacter calcoaceticus and Stenotrophomonas maltophilia. Free chlorine from calcium hypochlorite was used for comparison. The dose and time-responses against planktonic bacteria were performed as well as the assessment of the effects on membrane integrity. Moreover, the effects against 48 h-old biofilms formed on polyvinyl chloride and stainless steel were evaluated in terms of biofilm culturability and removal. Minimum bactericidal concentrations of 2.1 and 3.1 mg/L for NaDCC, 2.5 and 3.8 mg/L for TCCA, 340 and 690 mg/L for OXONE, and 0.80 and 1.0 mg/L for free chlorine alone were obtained against S. maltophilia and A. calcoaceticus, respectively. The kinetic modeling revealed that NaDCC and TCCA caused similar inactivation rates and the time for first log reduction by OXONE was less than 10 min, for both bacteria. All the disinfectants triggered significant bacterial cytoplasmic membrane destabilization, even at sub-lethal concentrations. A 30 min treatment with the disinfectants allowed a reduction in the biofilm culturability up to 5 log. OXONE was the disinfectant with the best efficiency against both bacterial biofilms. However, none of the disinfectants caused significant biofilm removal (reduction < 1 log cells/cm²). This study highlights NaDCC, TCCA, and OXONE as promising alternatives to free chlorine for DW disinfection, particularly for planktonic growth control and biofilm culturability reduction.

VG, Kadri SS. Trimethoprim-Sulfamethoxazole versus Levofloxacin for Stenotrophomonas maltophilia Infections: A Retrospective Comparative Effectiveness Study of Electronic Health Records from 154 U.S. Hospitals

Background

Trimethoprim-sulfamethoxazole (TMP-SMX) is considered first-line therapy for Stenotrophomonas maltophilia infections based on observational data from small studies. Levofloxacin has emerged as a popular alternative due to tolerability concerns related to TMP-SMX. Data comparing levofloxacin to TMP-SMX as targeted therapy are lacking.

Methods

Adult inpatient encounters January 2005 through December 2017 with growth of S maltophilia in blood and/or lower respiratory cultures were identified in the Cerner Healthfacts database. Patients included received targeted therapy with either levofloxacin or TMP-SMX. Overlap weighting was used followed by downstream weighted regression. The primary outcome was adjusted odds ratio (aOR) for in-hospital mortality or discharge to hospice. The secondary outcome was number of days from index S maltophilia culture to hospital discharge.

Results

Among 1581 patients with S maltophilia infections, levofloxacin (n = 823) displayed statistically similar mortality risk (aOR, 0.76 [95% confidence interval {CI}, .58–1.01]; P = .06) compared to TMP-SMX (n = 758). Levofloxacin (vs TMP-SMX) use was associated with a lower aOR of death in patients with lower respiratory tract infection (n = 1452) (aOR, 0.73 [95% CI, .54–.98]; P = .03) and if initiated empirically (n = 89) (aOR, 0.16 [95% CI, .03–.95]; P = .04). The levofloxacin cohort had fewer hospital days between index culture collection and discharge (weighted median [interquartile range], 7 [4–13] vs 9 [6–16] days; P < .0001).

Conclusions

Based on observational evidence, levofloxacin is a reasonable alternative to TMP-SMX for the treatment of bloodstream and lower respiratory tract infections caused by S maltophilia.

Stenotrophomonas maltophilia Infections in Pediatric Patients - Experience at a European Center for Pediatric Hematology and Oncology

Stenotrophomonas maltophilia is an important nosocomial pathogen in immunocom-promised individuals and characterized by intrinsic resistance to broad-spectrum antibacterial agents. Limited data exists on its clinical relevance in immunocompromised pediatric patients, particularly those with hematological or oncological disorders. In a retrospective single center cohort study in pediatric patients receiving care at a large european pediatric hematology and oncology department, ten cases of invasive S.maltophilia infections (blood stream infections (BSI), 4; BSI and pneumonia, 3, or soft tissue infection, 2; and pneumonia, 1) were identified between 2010 and 2020. Seven patients had lymphoblastic leukemia and/or were post allogeneic hematopoietic cell transplantation. Invasive S.maltophilia infections occurred in a setting of indwelling central venous catheters, granulocytopenia, defective mucocutaneous barriers, treatment with broad-spectrum antibacterial agents, and admission to the intensive care unit. Whole genome sequencing based typing revealed no genetic relationship among four individual S.maltophilia isolates. The case fatality rate and mortality at 100 days post diagnosis were 40 and 50%, respectively, and three patients died from pulmonary hemorrhage. Invasive S.maltophilia infections are an emerging cause of infectious morbidity in patients receiving care at departments of pediatric hematology and oncology and carry a high case fatality rate.

Prevalence of antibiotic-resistant bacterial strains in wastewater streams: molecular characterization and relative abundance

Bacteria from wastewater discharged to the sewerage near three hospitals of Islamabad, Rawalpindi, and Faisalabad were examined for resistance to the most commonly prescribed antibiotics in Pakistan. From the selected sites, a total of 109 isolates from 40 different species were identified based on 16S rRNA gene sequence and phylogeny. The isolates were tested for their resistance to ciprofloxacin, levofloxacin, ofloxacin, amoxicillin, and ampicillin. The results indicated that the isolates were resistant with the highest percentage to ampicillin and the lowest percentage to ciprofloxacin. Among the resistant isolates, 91.7% were found resistant to ampicillin, 83.5% to amoxicillin, 67.0% to ofloxacin, whereas only 27.5% to ciprofloxacin and 21.1% to levofloxacin. Among three sampled locations, the most of resistance was observed in Escherichia and Acinetobacter species. More than 30% isolated microorganisms were found resistant to more than three antibiotics. These findings concluded the presence of predominant microbial population resistant to antibiotics in wastewater channels near hospitals and its surroundings, which requires further investigation regarding their existence and spread in other environmental media having potential community health implications.

Antimicrobial resistance trends of non-fermenter Gram negative bacteria in Saudi Arabia: A six-year national study

BACKGROUND

Antimicrobial resistance (AMR) of non-fermenting Gram-negative bacteria (NFGNB) is increasingly recognized as urgent healthcare threat. Trend data on AMR of NFGNB in Saudi Arabia are either old or limited. The objective was to estimate the prevalence and resistance trends of isolated NFGNB in Saudi Arabia.

METHODS

A retrospective multicenter study involving seven tertiary care hospitals in Saudi Arabia was conducted between 2011 and 2016. Susceptibility testing for non-duplicate isolates was performed according to the Clinical and Laboratory Standards Institute (CLSI) guidelines in College of American Pathologists accredited diagnostic microbiology laboratories in the participating hospitals.

RESULTS

Out of 461,274 isolates, 100,132 (21.7%) were NFGNB which represented 30% of gram-negative pathogens. Pseudomonas aeruginosa was the most common (73.6%), followed by Acinetobacter baumannii (21.0%) and Stenotrophomonas maltophilia (5.3%). Resistance trends of P. aeruginosa were increasing for aztreonam (absolute increase during the study was 17.3%), imipenem (12.3%), and meropenem (11.6%). A. baumannii was fully resistant to several beta lactam drugs, and resistance trends were increasing for potential treatments such as tigecycline (25.1%) and tobramycin (15.5%). S. maltophilia was >90% resistant to trimethoprim/ sulfamethoxazole and ciprofloxacin by the end of the study.

CONCLUSION

We are reporting high and/or increasing resistance of NFGNB to common treatment options. The current findings call for urgent actions to combat the increasing resistance of NFGNB. Large scale sharing of AMR data collected at different hospitals with the Saudi AMR committee would be critical to set priorities and monitor progress.

Clinical outcomes of Stenotrophomonas maltophilia infection treated with trimethoprim/sulfamethoxazole, minocycline, or fluoroquinolone monotherapy

OBJECTIVES

The historical treatment of choice for Stenotrophomonas maltophilia infection is trimethoprim/sulfamethoxazole and this is primarily based on preclinical studies. The objective of this study was to examine the clinical outcomes of patients receiving monotherapy with different agents.

METHODS

This was a retrospective study of adult patients receiving monotherapy for S. maltophilia infection with trimethoprim/sulfamethoxazole (TMP/SMX), a fluoroquinolone, or minocycline from 2010 to 2016. The primary outcome was clinical failure, a composite of recurrence, alteration of therapy due to adverse reaction or concern for clinical failure, or 30-day in-hospital mortality. The secondary outcome was 30-day in-hospital mortality. To account for treatment selection bias, multivariate regression and propensity score weighting were conducted.

RESULTS

284 patients were included (217 received TMP/SMX, 28 received a fluoroquinolone, and 39 received minocycline). The TMP/SMX and minocycline groups appeared to include similar patients whereas the fluoroquinolone group appeared to represent a slightly less severely ill population. Clinical failure was similar between groups (36%, 29%, and 31% in the TMP/SMX, fluoroquinolone, and minocycline groups, respectively, P=0.69) as was 30-day mortality (15%, 7%, and 5% in the TMP/SMX, fluoroquinolone, and minocycline groups, respectively, P=0.16). After controlling for confounding factors, receipt of minocycline (adjusted odds ratio [OR]=0.2 [0.1-0.7]) but not a fluoroquinolone (adjusted OR=0.3 [0.1 to 2.1]) was associated with lower mortality compared with TMP/SMX. This association persisted after propensity score weighting.

CONCLUSIONS

Outcomes were similar or better with alternatives to TMP/SMX monotherapy, which indicates this may not be the treatment of choice for infections caused by S. maltophilia.

Prevalence and antibiogram of non-fermenting Gram-negative bacilli in blood stream infections: Study in a tertiary care centre, Western Uttar Pradesh, India

Non-fermenting Gram-negative bacilli (NFGNB) are emerging as important cause of blood stream infections. We aimed to determine the prevalence and antibiotic susceptibility pattern of NFGNB isolated from blood of patients with sepsis. We found, in 176 patients, the most common to be Pseudomonas aeruginosa (74) and Acinetobacter baumanii complex (39) followed by Stenotrophomonas maltophilia (16), Sphingomonas paucimobilis (6), Burkholderia cepacia (5) and Ochrobactrum anthropic (1). Generally, organisms showed a good sensitivity towards colistin, carbapenems and fluoroquinolones, whereas cephalosporins were ineffective.

Effect of antimicrobials on Stenotrophomonas maltophilia biofilm

Aim: To evaluate the activity of five antimicrobials against young and mature Stenotrophomonas maltophilia biofilms. Materials & methods: Nineteen clinical strains from hemoculture of hemodialysis patients were tested for biofilm kinetics, MIC and minimum biofilm inhibitory concentration (MBIC) in young and mature biofilms. Results: All strains were moderate biofilm producers. MIC showed total susceptibility to levofloxacin and trimethoprim-sulfamethoxazole and partial resistance to ceftazidime (63.2%) and gentamicin (21%). Young and mature biofilms showed the lowest MBIC/MIC ratio for gentamicin, chloramphenicol and levofloxacin, respectively. The highest MBIC/MIC was for trimethoprim-sulfamethoxazole (young) and ceftazidime (mature). Conclusion: Gentamicin displayed surprising activity against S. maltophilia biofilms. Chloramphenicol was indicated as a good option against young S. maltophilia biofilms, and trimethoprim-sulfamethoxazole showed limited antibiofilm activity.

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.

Clinical and microbiological characteristics of patients colonized or infected by Stenotrophomonas maltophilia : is resistance to sulfamethoxazole/trimethoprim a problem?

Stenotrophomonas maltophilia has emerged as an important opportunistic pathogen in the last decade. Increased resistance to sulfamethoxazole/trimethoprim (SMX/TMP) has been reported in S. maltophilia strains in the past few years, leading to few therapeutic options. We conducted a prospective multicenter study at two Brazilian teaching hospitals that identified S. maltophilia isolates and evaluated their antimicrobial susceptibility profile, SMX/TMP resistance genes and their clonality profile. A total of 106 non-repeated clinical samples of S. maltophilia were evaluated. Resistance to SMX/TMP was identified in 21.6% of the samples, and previous use of SMX/TMP occurred in 19 (82.6%). PCR detected the sul1 gene in 14 of 106 strains (13.2%). Of these isolates, nine displayed resistance to SMX/TMP. The resistant strains presented a polyclonal profile. This opportunistic pathogen has emerged in immunocompromised hosts, with few therapeutic options, which is aggravated by the description of emerging resistance mechanisms, although with a polyclonal distribution profile.

Activity of Aztreonam in Combination with Avibactam, Clavulanate, Relebactam, and Vaborbactam against Multidrug-Resistant Stenotrophomonas maltophilia

The intrinsic L1 metallo- and L2 serine-β-lactamases in Stenotrophomonas maltophilia make it naturally multidrug resistant and difficult to treat. There is a need to identify novel treatment strategies for this pathogen, especially against isolates resistant to first-line agents. Aztreonam in combination with avibactam has demonstrated potential, although data on other aztreonam-β-lactamase inhibitor (BLI) combinations are lacking. Additionally, molecular mechanisms for reduced susceptibility to these combinations have not been explored. The objectives of this study were to evaluate and compare the in vitro activities and to understand the mechanisms of resistance to aztreonam in combination with avibactam, clavulanate, relebactam, and vaborbactam against S. maltophilia A panel of 47 clinical S. maltophilia strains nonsusceptible to levofloxacin and/or trimethoprim-sulfamethoxazole were tested against each aztreonam-BLI combination via broth microdilution, and 6 isolates were then evaluated in time-kill analyses. Three isolates with various aztreonam-BLI MICs were subjected to whole-genome sequencing and quantitative reverse transcriptase PCR. Avibactam restored aztreonam susceptibility in 98% of aztreonam-resistant isolates, compared to 61, 71, and 15% with clavulanate, relebactam, and vaborbactam, respectively. The addition of avibactam to aztreonam resulted in a ≥2-log₁₀-CFU/ml decrease at 24 h versus aztreonam alone against 5/6 isolates compared to 1/6 with clavulanate, 4/6 with relebactam, and 2/6 with vaborbactam. Molecular analyses revealed that decreased susceptibility to aztreonam-avibactam was associated with increased expression of genes encoding L1 and L2, as well as the efflux pump (smeABC). Aztreonam-avibactam is the most promising BLI-combination against multidrug-resistant S. maltophilia Decreased susceptibility may be due to the combination of overexpressed β-lactamases and efflux pumps. Further studies evaluating this combination against S. maltophilia are warranted.

High Frequency of AdeA, AdeB and AdeC Genes among Acinetobacter baumannii Isolates

Background:

Efflux pumps are involved in resistance of Acinetobacter baumannii isolates to antimicrobial agents. AdeABC efflux pump is one of the RND superfamily efflux pump and consists of adeA (membrane fusion), adeB (multidrug transporter) and adeC (outer membrane) genes. In this study, the frequency of adeA, adeB and adeC genes among A. baumannii isolates with resistance to erythromycin, trimethoprim, meropenem and imipenem was investigated.

Methods:

Overall, 79 strains of A. baumannii were isolated from patients admitted to two major hospitals in Tehran during 2016. Antibiotic susceptibility testing was determined by disc diffusion and microdilution methods according to Clinical and Laboratory Standards Institute (CLSI) guideline. The presence of adeA, adeB and adeC genes was also determined using Multiplex PCR assay.

Results:

The highest and the lowest resistance among A. baumannii isolates were to trimethoprim (93%) and erythromycin (53%), respectively. The frequency of adeA, adeB and adeC genes was 96.2%, 96.2% and 91.1 % respectively. There was a significant relationship between imipenem resistance and presence of efflux pump genes (P<0.05).

Conclusion:

According to the high prevalence of the AdeABC efflux system genes, it may involve in resistance of clinical isolates of A. baumannii to imipenem, especially.

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.

Dissemination of Plasmid-Mediated Aminoglycoside-Modifying Enzymes Among MDR Acinetobacter baumannii Isolates from a Tertiary Care Egyptian Hospital

Background:

Acinetobacter baumannii is one of the most challenging multidrug-resistant (MDR) nosocomial pathogens worldwide. Aminoglycosides are used for the treatment of A. baumannii infections, however, resistance to aminoglycosides is currently emerging, limiting therapeutic choices.

Objective:

In this study, the prevalence of aminoglycoside resistance and plasmid-mediated mechanisms of aminoglycoside resistance were investigated in A. baumannii clinical isolates collected from ICU patients at a tertiary care hospital in Egypt.

Methods:

The automated Vitek 2 system was used to identify A. baumannii species and determination of the antimicrobial susceptibility pattern. The identification of A. baumannii was confirmed by the detection of the blaOXA-51-like gene intrinsic to this species. Minimum Inhibitory Concentration (MIC) of gentamicin was determined using E-test following the CLSI breakpoints. Isolates were screened for the prevalence and diversity of the plasmid-carried aminoglycoside-modifying enzymes encoding genes aacC1, aadA1, aadB and aphA6. For genetic diversity analysis, the ERIC-PCR method was performed.

Results:

All A. baumannii isolates were MDR with high resistance rates to tested antimicrobials. The resistance rate to gentamicin was 92.9% with elevated MICs (≥ 32 μg/mL). The gentamicin-resistant isolates harboured one or more of the studied genes with the prevalence of aphA6 (81%). ERIC-based genotyping revealed that there was no evidence of A. baumannii clonal dissemination among isolates.

Conclusion:

The study concluded that MDR A. baumannii isolates were highly resistant to gentamicin. The plasmid-carried aminoglycoside-modifying enzymes encoding genes were disseminated among isolates with the AphA6 gene, which was the most prevalent one. The acquisition of more than one aminoglycoside resistance gene was associated with an elevated MIC of gentamicin. Thus, regular surveillance studies of the emerging resistance to antimicrobials and strict measures to control the dissemination of resistance determinants genes are warranted.

Tigecycline to treat Stenotrophomonas maltophilia ventilator-associated pneumonia in a trauma intensive care unit as a result of a drug shortage: A case series

WHAT IS KNOWN AND OBJECTIVE

Stenotrophomonas maltophilia is an intrinsically multidrug-resistant (MDR) organism which commonly presents as a respiratory tract infection. S. maltophilia is typically treated with high-dose sulfamethoxazole/trimethoprim (SMX/TMP). However, SMX/TMP and other treatment options for S. maltophilia can be limited because of resistance, allergy, adverse events or unavailability of the drug; use of novel agents may be necessary to adequately treat this MDR infection and overcome these limitations.

CASE DESCRIPTION

This small case series describes two patients who underwent treatment with tigecycline for ventilator-associated pneumonia (VAP) caused by S. maltophilia after admission to a trauma intensive care unit. At the time of admission for the two reported patients, a national drug shortage of intravenous (IV) SMX/TMP prevented its use. Tigecycline was chosen as a novel agent to treat S. maltophilia VAP based on culture and susceptibility data, and it was used successfully. Both patients showed clinical signs of improvement with eventual cure and discharge from the hospital after treatment with tigecycline, and one patient demonstrated confirmed microbiological cure with a negative repeat bronchoscopic bronchoalveolar lavage (BAL).

WHAT IS NEW AND CONCLUSION

To our knowledge, this small case series is the first documentation of utilizing tigecycline to treat S. maltophilia VAP in the United States. Although it likely should not be considered as a first-line agent, tigecycline proved to be an effective treatment option in the two cases described in the setting of a national drug shortage of the drug of choice.

Antimicrobial susceptibility pattern of Stenotrophomonas species isolated from Mexico

BACKGROUND

Stenotrophomonas species are multi-resistant bacteria with ability to cause opportunistic infections.

OBJECTIVE

We isolated 45 Stenotrophomonas species from soil, sewage and the clinic with the aim of investigating their susceptibility to commonly used antimicrobial agents.

METHODOLOGY

The identities of isolates were confirmed with 16S rRNA gene sequence and MALDI-TOF analysis. Anti-microbial resistance, biofilm production and clonal diversity were also evaluated. The minimum inhibitory concentration technique as described by Clinical & Laboratory Standards Institute: CLSI Guidelines (CLSI) was employed for the evaluation of isolate susceptibility to antibiotics.

RESULT

Forty-five Stenotrophomonas species which include 36 environmental strains and 9 clinical strains of S. maltophilia were considered in this study. 32 (88.9 %) environmental strains were identified to be S. maltophilia, 2 (5.6 %) were Stenotrophomonas nitritireducens, and 2 (5.6 %) cluster as Stenotrophomonas spp. Stenotrophomonas isolates were resistant to at least six of the antibiotics tested, including Trimethoprim/Sulfamethoxazole (SXT).

CONCLUSION

Environmental isolates from this study were resistant to SXT which is commonly used for the treatment of S. maltophilia infections. This informs the need for good public hygiene as the environment could be a reservoir of multi-resistant bacteria. It also buttresses the importance of surveillance study in the management of bacterial resistance.

Molecular Epidemiology, Antibiotic Resistance, and Virulence Traits of Stenotrophomonas maltophilia Strains Associated With an Outbreak in a Mexican Tertiary Care Hospital

Stenotrophomonas maltophilia, an emerging opportunistic pathogen, is widely distributed in the environment the resistance mechanisms, and virulence factors of this bacterium facilitate its dissemination in hospitals. This study aimed to characterize the molecular epidemiology of S. maltophilia strains associated with an outbreak in the Children's Hospital of México Federico Gómez (HIMFG). Twenty-one clinical S. maltophilia strains were recovered from cultures of blood and urine samples from 10 pediatric patients at the emergency department, and nine environmental S. maltophilia strains recovered from faucets in the same area were also included. Two of the 10 patients were related with health care-associated infections (HCAIs), and the other eight patients (8/10) were infected with environmental S. maltophilia strains. The outbreak was controlled by monthly disinfection of the faucets in the emergency department. Typing using pulsed-field gel electrophoresis (PFGE) showed a 52% genetic diversity with seven pulsotypes denoted P1–P7 among all S. maltophilia strains. Three pulsotypes (P2, P3, and P7) were identified among both the clinical and environmental S. maltophilia strains and associated with two type sequences (STs), namely, ST304 and ST24. Moreover, 80% (24/30) of the strains exhibited resistance mainly to tetracycline, 76.66% (23/30) to trimethoprim-sulfamethoxazole, and 23.33% (7/30) to the extended-spectrum β-lactamase (ESBL) phenotype. The main resistance genes identified by multiplex PCR were sul1 in 100% (30/30), qnr in 86.66% (26/30), and intl1 in 80% (24/30) of the samples, respectively. Furthermore, the pilU, hlylII, and rmlA genes were identified in 96.6% (29/30), 90% (27/30), and 83.33% (25/30) of the samples, respectively. Additionally, 76.66% (23/30) of the S. maltophilia strains exhibited high swimming motility, 46.66% (14/30) showed moderate biofilm formation capacity, 43.33% (13/30) displayed moderate twitching motility, and 20% (6/30) exhibited high adherence. The clinical S. maltophilia strains isolated from blood most strongly adhered to HTB-9 cells. In conclusion, the molecular epidemiology and some of the features such as resistance, and virulence genes associated with colonization patterns are pathogenic attributes that can promote S. maltophilia dissemination, persistence, and facilitate the outbreak that occurred in the HIMFG. This study supports the need for faucet disinfection as a control strategy for clinical outbreaks.

Interaction of Oral and Toothbrush Microbiota Affects Oral Cavity Health

Tooth brushing is necessary to maintain oral health. Little research has been carried out to explore microbial diversity in toothbrushes and to study the potential impact of these bacteria on human health. In the present study, 20 participants were enrolled, and the microbial diversity in their oral cavity and toothbrushes was investigated using high-throughput sequencing. Our results indicate that 1,136 and 976 operational taxonomic units (OTUs) were obtained from groups CB (samples from toothbrushes of participants using traditional Chinese medicinal toothpaste) and AB (samples from toothbrushes of those using antibacterial toothpaste), respectively. The pathogens Acinetobacter baumannii, Staphylococcus aureus, and Candida albicans were identified on toothbrushes. The presence of these pathogens increases the chance for the host to get infectious diseases, neurodegenerative diseases, cardiovascular diseases, and cancers. Moreover, our in vitro results indicate that traditional Chinese medicinal toothpaste and antibacterial toothpaste can not only inhibit the growth of pathogens but also markedly inhibit the growth of probiotics Lactobacillus salivarius and Streptococcus salivarius. Therefore, the inhibitory effect of toothpaste on probiotics, together with the existence of pathogens in toothbrushes, indicates a potential risk of tooth brushing for people in a sub-healthy state.

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.

High Prevalence of Multi-Drug Resistance and Extended Spectrum Beta Lactamase Production in Non-Fermenting Gram-Negative Bacilli in Ethiopia

Background

Emergence of resistance to multiple antimicrobial agents in Non-Fermenting Gram-Negative Bacilli is a major problem to public health, as it limits drug treatment options against infections. The aim of this study was to determine the prevalence of multi-drug resistance and extended spectrum beta lactamase production in Non-Fermenting Gram-Negative Bacilli.

Materials and methods

Different clinical samples were collected and processed following standard procedures. Each sample was then inoculated onto culture media. Identification, drug susceptibility testing, and extended spectrum beta lactamase production of the isolates were carried out by using the VITEK 2 compact system.

Results

Among 996 clinical samples, 135 samples yielded Non-Fermenting Gram-Negative Bacilli of which Pseudomonas and Acinetobacter species were the commonest isolates. The overall drug resistance rates of Non-Fermenting Gram-Negative Bacilli were above 80% against ampicillin (89.6%), cefuroxime axetil (88.9%), nitrofurantoin (85.9%), cefalotin (84.4%), cefoxitin (83.7%), cefazolin (83.0%), and cefuroxime (83.0%). Tobramycin with a resistance rate of 19.3% was the most active antimicrobial agent. Out of 135 isolates, 81.5% were multi-drug resistant of which 13.3% were extensively drug resistant and 10.4% were pandrug resistant. Extended spectrum beta lactamase production was detected in 48.9% of the isolates.

Conclusions

The spectrum of bacterial species isolated was diverse. The isolates demonstrated high level of drug resistance in different classes of antibiotics. The magnitude of multi-drug resistance and the level of extended spectrum beta lactamase production were high. Hence, further studies on multi-drug resistant and extended spectrum beta lactamase producing Non-Fermenting Gram-Negative Bacilli both in the community and in hospital setting are essential.

Quantitative real-time PCR assay for the rapid identification of the intrinsically multidrug-resistant bacterial pathogen Stenotrophomonas maltophilia

Stenotrophomonas maltophilia is emerging as an important cause of disease in nosocomial and community-acquired settings, including bloodstream, wound and catheter-associated infections. Cystic fibrosis (CF) airways also provide optimal growth conditions for various opportunistic pathogens with high antibiotic tolerance, including S. maltophilia. Currently, there is no rapid, cost-effective and accurate molecular method for detecting this potentially life-threatening pathogen, particularly in polymicrobial specimens, suggesting that its true prevalence is underestimated. Here, we used large-scale comparative genomics to identify a specific genetic target for S. maltophilia, with subsequent development and validation of a real-time PCR assay for its detection. Analysis of 167 Stenotrophomonas spp. genomes identified a conserved 4 kb region in S. maltophilia, which was targeted for Black Hole Quencher assay design. Our assay yielded the positive detection of 89 of 89 (100%) clinical S. maltophilia strains, and no amplification of 23 non-S. maltophilia clinical isolates. S. maltophilia was detected in 10 of 16 CF sputa, demonstrating the assay's utility for direct detection in respiratory specimens. The assay demonstrated good sensitivity, with limits of detection and quantitation on pure culture of ~10 and ~100 genome equivalents, respectively. Our assay provides a highly specific, sensitive and cost-effective method for the accurate identification of S. maltophilia, and will improve the diagnosis and treatment of this under-recognized pathogen by enabling its accurate and rapid detection from polymicrobial clinical and environmental samples.

A systematic review of the global seasonality of infections caused by Acinetobacter species in hospitalized patients

BACKGROUND

Acinetobacter is a leading multidrug resistant pathogen in hospitals worldwide that has been seen to exhibit periodic surges during summer months. However, winter peaks and lack of seasonality have also been noted.

OBJECTIVES

To systematically collate and examine the evidence describing seasonal patterns in the incidence of Acinetobacter infection in hospitalized patients.

DATA SOURCES

MEDLINE/Ovid, EMBASE, Scopus and Web of Science.

STUDY ELIGIBILITY CRITERIA

Longitudinal observational studies investigating seasonal variation in the incidence of Acinetobacter infection.

PARTICIPANTS

Patients receiving hospital care.

INTERVENTIONS

Routine hospital care.

METHODS

Systematic review with narrative evidence synthesis structured around clinical and methodological heterogeneity and internal validity of retrieved studies, seasonal patterns and risk factors detected, and stated hypotheses of mechanisms underlying seasonality. To examine consistency in reported seasonal patterns across different conditions, monthly incidence data were extracted, standardised, weighted and presented graphically.

RESULTS

Twenty-five studies reporting 37006 cases of Acinetobacter infection or colonization during 1954 months of follow-up were reviewed. Standardised monthly incidence data pooled across studies exhibited a global seasonal pattern with an incidence peak in summer/warmer months and a trough in winter/colder months. This seasonal pattern remained consistent under different weighting schemes accounting for study size, length of follow-up and overall quality assessment rating. Seasonality persisted in different clinical settings and for different types and sources of infection. Nine studies provided consistent evidence of temperature-associated variation in Acinetobacter incidence, while there were controversial findings regarding other environmental variables. No study detected patient-related or clinical practice-related seasonal variation in Acinetobacter incidence.

CONCLUSIONS

Despite substantial clinical and methodological heterogeneity in retrieved studies, a consistent global seasonal pattern in Acinetobacter infection incidence was evident in this review. This merits attention when designing or evaluating infection control interventions in hospitals. Future research should focus on elucidating driving mechanisms underlying the observed seasonality.

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.

Risk factors for mortality in patients with Stenotrophomonas maltophilia bacteremia and clinical impact of quinolone-resistant strains

Background

Stenotrophomonas maltophilia is an important nosocomial pathogen. This pathogen has intrinsic or acquired resistance to a number of antibiotics classes. Furthermore, Stenotrophomonas infections have been associated with high mortality, mainly in immunocompromised patients. Accordingly, we conducted a retrospective cohort study on the clinical data, microbiological characteristics, and outcomes of patients with S. maltophilia (SM) bacteremia.

Methods

A retrospective cohort study was conducted at two tertiary care referral hospitals in Seoul, South Korea. Data were collected between January 2006 and December 2015 from electric medical records. Our analysis aimed to identify the risk factors associated with crude mortality, as well as the predictive factors of quinolone-resistant strains in SM bacteremia patients.

Results

A total of 126 bacteremia patients were enrolled in the study. The mortality rate was 65.1%. On multivariable analysis, hypoalbuminemia (odds ratio [OR], 5.090; 95% confidence interval [CI], 1.321–19.621; P = 0.018), hematologic malignancy (OR, 35.567; 95% CI, 2.517–502.515; P = 0.008) and quinolone-resistant strains (OR, 7.785; 95% CI, 1.278–47.432; P = 0.026) were independent risk factors for mortality. Alternatively, usage of an empirical regimen with quinolone (OR, 0.172; 95% CI, 0.034–0.875; P = 0.034) was an independent protective factor for mortality. The multivariable analysis of predictive factors revealed that high Charlson comorbidity index (OR, 1.190; 95% CI, 1.040–1.361; P = 0.011) and indwelling of a central venous catheter (CVC) (OR, 3.303; 95% CI, 1.194–9.139; P = 0.021) were independent predisposing factors associated with quinolone-resistant strains in SM bacteremia patients.

Conclusions

Our findings suggest that a high Charlson comorbidity score and indwelling of a CVC were significantly independent predictors of quinolone-resistant strains in SM bacteremia patients. Therefore, we need to carefully consider the antibiotic use in SM bacteremia patients with these predictive factors.

Electronic supplementary material

The online version of this article (10.1186/s12879-019-4394-4) contains supplementary material, which is available to authorized users.

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

Background:

Since the 1980s, Stenotrophomonas maltophilia has emerged as an important pathogen associated with significant mortality in pneumonia and bacteremia of severely immunocompromised, hospitalized patients. The drug of choice in S maltophilia infections is sulfamethoxazole-trimethoprim (SMX/TMP); SMX/TMP resistance is a serious concern in clinical practice. The aim of this study was to assess the prevalence of S maltophilia in lower respiratory tract (LRTI) samples at a tertiary-care university hospital.

Methods:

This retrospective cohort study was carried out using microbiological data collected between January 2008 and December 2017. Routine antimicrobial susceptibility testing was performed for SMX/TMP and levofloxacin; in case of resistance, susceptibility testing for additional antibiotics (tigecycline, amikacin, and colistin) was also performed.

Results:

A total of 579 individual S maltophilia isolates were identified (2008-2012: n = 160, 2013-2017: n = 419; P = .0008). In all, 78.46% of patients were younger than 5 or older than 50 years of age and had recent trauma, surgery, or underlying conditions (malignancies, respiratory distress syndrome, congenital disorders, and cystic fibrosis). In 28.16% of samples, more than 1 pathogen was identified, and 5.35% of coisolated pathogens were multidrug resistant (MDR). In all, 12.1% of isolates were SMX/TMP-resistant (2008-2012: 6.12%, 2013-2017: 18.06%; P = .034), while 8.99% were resistant to levofloxacin (2008-2012: 7.86%, 2013-2017: 10.12%; P > .05). SMX/TMP resistance was detected more frequently in samples originating from inpatients (n = 2.50 ± 2.39 vs n = 11.50 ± 3.76; P = .0002).

Conclusions:

In all, 5.87% of isolates were extensively drug resistant (XDR), that is, in addition to SMX/TMP, they were resistant to levofloxacin, amikacin, colistin, and tigecycline. The results of our study correspond to the findings in the literature.

Epidemiological investigation of non-fermentative bacterial infection in cirrhotic patients

Background: This study aimed to describe the clinical characteristics of NFGNB in patients with cirrhosis as well as the risk factors for short-term mortality. Methods: A retrospective analysis was performed in patients with cirrhosis and NFGNB infections from 2011 to 2016 . Results: 144 episodes in 134 patients with liver cirrhosis and NFGNB infections were found in total. Of these, 81.2% were hospital-acquired or healthcare- associated infections, while only 18.8% of NFGNB infections originated from the community. A. baumannii were the most frequently isolated bacteria (39 episodes), followed by S. maltophilia (38 episodes) and P. aeruginosa (31 episodes). MDR- and non-MDR-NFGNB comprised 62.5% and 37.5% of infections respectively. The Kaplan-Meier survival curve showed no significant difference between MDR and non-MDR NFGNB patients (74.1% vs 75.5%, P = 0.811). Neither MDR or the subgroup of common NFGNB (P. aeruginosa, A. baumannii, S. maltophilia) was associated with the 28-day mortality (all P >0.05). Low albumin levels and high Tbil levels were both independent risk factors for 28-day mortality (HR = 0.930, 95%CI (0.869, 0.995), P = 0.035; HR = 1.003, 95%CI (1.002, 1.005), P < 0.001, respectively). Conclusions: Diabetes increased 28-day mortality significantly, however, MDR status, site of infection and bacteria type did not.

Population Structure, Molecular Epidemiology, and β-Lactamase Diversity among Stenotrophomonas maltophilia Isolates in the United States

Stenotrophomonas maltophilia is a Gram-negative, nonfermenting, environmental bacillus that is an important cause of nosocomial infections, primarily associated with the respiratory tract in the immunocompromised population. Aiming to understand the population structure, microbiological characteristics and impact of allelic variation on β-lactamase structure and function, we collected 130 clinical isolates from across the United States. Identification of 90 different sequence types (STs), of which 63 are new allelic combinations, demonstrates the high diversity of this species. The majority of the isolates (45%) belong to genomic group 6. We also report excellent activity of the ceftazidime-avibactam and aztreonam combination, especially against strains recovered from blood and respiratory infections for which the susceptibility is higher than the susceptibility to trimethoprim-sulfamethoxazole, considered the "first-line" antibiotic to treat S. maltophilia Analysis of 73 blaL1 and 116 blaL2 genes identified 35 and 43 novel variants of L1 and L2 β-lactamases, respectively. Investigation of the derived amino acid sequences showed that substitutions are mostly conservative and scattered throughout the protein, preferentially affecting positions that do not compromise enzyme function but that may have an impact on substrate and inhibitor binding. Interestingly, we detected a probable association between a specific type of L1 and L2 and genomic group 6. Taken together, our results provide an overview of the molecular epidemiology of S. maltophilia clinical strains from the United States. In particular, the discovery of new L1 and L2 variants warrants further study to fully understand the relationship between them and the β-lactam resistance phenotype in this pathogen.IMPORTANCE Multiple antibiotic resistance mechanisms, including two β-lactamases, L1, a metallo-β-lactamase, and L2, a class A cephalosporinase, make S. maltophilia naturally multidrug resistant. Thus, infections caused by S. maltophilia pose a big therapeutic challenge. Our study aims to understand the microbiological and molecular characteristics of S. maltophilia isolates recovered from human sources. A highlight of the resistance profile of this collection is the excellent activity of the ceftazidime-avibactam and aztreonam combination. We hope this result prompts controlled and observational studies to add clinical data on the utility and safety of this therapy. We also identify 35 and 43 novel variants of L1 and L2, respectively, some of which harbor novel substitutions that could potentially affect substrate and/or inhibitor binding. We believe our results provide valuable knowledge to understand the epidemiology of this species and to advance mechanism-based inhibitor design to add to the limited arsenal of antibiotics active against this pathogen.