Fulminant Stenotrophomonas maltophilia soft tissue infection in immunocompromised patients: an outbreak transmitted via tap water

Stenotrophomonas maltophilia outbreak originating from a pull-out faucet in a pediatric intensive care unit in Turkey: Insights from clinical records and molecular typing

BACKGROUND

Nosocomial Stenotrophomonas maltophilia-related cases are rising and pose a threat to immunocompromised patients. Twelve patients from our pediatric intensive care unit (PICU) presented with S maltophilia-associated bloodstream infection.

METHODS

This outbreak investigation includes 12 patients from PICU between the ages of 2 months and 4 years (mean 16 months, 7 male). To identify the origin, samples from all possible sources throughout the hospital were collected and ran through DNA isolation and Pulse Field Gel Electrophoresis.

RESULTS

120 samples were collected during the outbreak. 31 samples (26%) were positive for S maltophilia. 30 S maltophilia isolates were analyzed, 10 different genotypes were identified. Clustering isolates were grouped into 3 different clusters (tolerance and optimization 1.0, cutoff 90%). The largest cluster was genotype 1, which included 19 isolates, those belong to patients' samples and a sample from a pull-out faucet inside the PICU. The Pull-out faucet was the origin of the bloodstream infection.

DISCUSSION

Pull-out faucets allow biofilm production, due its structure. Pulse Field Gel Electrophoresis identifies the transmission dynamics of the outbreak, with its high discriminatory power.

CONCLUSIONS

Water sources should be monitored on a regular basis. Pull-out faucets enable bacterial overgrowth; therefore, we recommend water surveillance during outbreak investigations.

Emerging infections in vulnerable hosts: Stenotrophomonas maltophilia and Elizabethkingia anophelis

PURPOSE OF REVIEW

This systematic review aimed to explore the recent trends in the epidemiology, risk factors, and antimicrobial susceptibility of two emerging opportunistic pathogens, Stenotrophomonas maltophilia and Elizabethkingia anophelis .

RECENT FINDINGS

Since 2020, numerous outbreaks of S. maltophilia and E. anophelis have been reported worldwide. Most of these outbreaks have been associated with healthcare facilities, although one outbreak caused by E. anophelis in France was considered a community-associated infection. In terms of antimicrobial susceptibility, trimethoprim/sulfamethoxazole (TMP-SMZ), levofloxacin, and minocycline have exhibited good efficacy against S. maltophilia . Additionally, cefiderocol and a combination of aztreonam and avibactam have shown promising results in in vitro susceptibility testing. For E. anophelis , there is currently no consensus on the optimal treatment. Although some studies have reported good efficacy with rifampin, TMP-SMZ, piperacillin/tazobactam, and cefoperazone/sulbactam, minocycline had the most favourable in vitro susceptibility rates. Cefiderocol may serve as an alternative due to its low minimum inhibitory concentration (MIC) against E. anophelis . The role of vancomycin in treatment is still uncertain, although several successful cases with vancomycin treatment, even with high MIC values, have been reported.

SUMMARY

Immunocompromised patients are particularly vulnerable to infections caused by S. maltophilia and E. anophelis , but the optimal treatment strategy remains inconclusive. Further research is necessary to determine the most effective use of conventional and novel antimicrobial agents in combatting these multidrug-resistant pathogens.

Functional network analysis identifies multiple virulence and antibiotic resistance targets in Stenotrophomonas maltophilia

Stenotrophomonas maltophilia, an emerging multidrug-resistant opportunistic bacterium in humans is of major concern for immunocompromised individuals for causing pneumonia and bloodborne infections. This bacterial pathogen is associated with a considerable fatality/case ratio, with up to 100%, when presented as hemorrhagic fever. It is resistant to commonly used drugs as well as to antibiotic combinations. In-silico based functional network analysis is a key approach to get novel insights into virulence and resistance in pathogenic organisms. This study included the protein-protein interaction (PPI) network analysis of 150 specific genes identified for antibiotic resistance mechanism and virulence pathways. Eight proteins, namely, PilL, FliA, Smlt2260, Smlt2267, CheW, Smlt2318, CheZ, and FliM were identified as hub proteins. Further docking studies of 58 selected phytochemicals were performed against the identified hub proteins. Deoxytubulosine and corosolic acid were found to be potent inhibitors of hub proteins of pathogenic S. maltophilia based on protein-ligand interactive study. Further pharmacophore studies are warranted with these molecules to develop them as novel antibiotics against S. maltophilia.

Influence of Temperature on Growth of Four Different Opportunistic Pathogens in Drinking Water Biofilms

High drinking water temperatures occur due to climate change and could enhance the growth of opportunistic pathogens in drinking water systems. We investigated the influence of drinking water temperatures on the growth of Pseudomonas aeruginosa, Stenotrophomonas maltophilia, Mycobacterium kansasii and Aspergillus fumigatus in drinking water biofilms with an autochthonous microflora. Our results reveal that the growth of P. aeruginosa and S. maltophilia in the biofilm already occurred at 15.0 °C, whereas M. kansasii and A. fumigatus were able to grow when temperatures were above 20.0 °C and 25.0 °C, respectively. Moreover, the maximum growth yield of P. aeruginosa, M. kansasii and A. fumigatus increased with increasing temperatures up to 30 °C, whereas an effect of temperature on the yield of S. maltophilia could not be established. In contrast, the maximum ATP concentration of the biofilm decreased with increasing temperatures. We conclude from these results that high drinking water temperatures caused by, e.g., climate change can result in high numbers of P. aeruginosa, M. kansasii and A. fumigatus in drinking water systems, which poses a possible risk to public health. Consequently, it is recommended for countries with a more moderate climate to use or maintain a drinking water maximum standard temperature of 25 °C.

Waterborne infections in haemato-oncology units - a narrative review

Bone marrow transplant and haemato-oncology patients are at risk of healthcare associated infections due to waterborne pathogens. We undertook a narrative review of waterborne outbreaks in haemato-oncology patients from 2000-2022. Databases searched included Pubmed, DARE and CDSR and were undertaken by two authors. We analysed the organisms implicated, sources identified and infection prevention and control strategies implemented. The most commonly implicated pathogens were Pseudomonas aeruginosa, non-tuberculous mycobacteria and Legionella pneumophila. Bloodstream infection was the most common clinical presentation. The majority of incidents employed multimodal strategies to achieve control, addressing both the water source and routes of transmission. This review highlights the risk to haemato-oncology patients from waterborne pathogens and discusses future preventative strategies and the requirement for new UK guidance for haemato-oncology units.

Fulminant Metastatic Cellulitis Caused by Stenotrophomonas Maltophilia Infection and Subsequent Candida Parapsilosis Fungemia After Cord Blood Transplantation

Stenotrophomonas maltophilia is known to be an opportunistic pathogen with intrinsic and acquired resistance mechanisms to multiple antibiotics. Bloodstream infection caused by S. maltophilia is a potentially fatal complication, especially in recipients of umbilical cord blood transplantation (CBT). Infrequent reports of S. maltophilia skin and soft tissue infections (SSTIs), including metastatic cellulitis and ecthyma gangrenosum, have been reported as wound infections. Metastatic cellulitis lesions due to S. maltophilia are typically reported to be tender, erythematous, and to show warm subcutaneous infiltration. There are only a few available reports about the clinical course of metastatic cellulitis due to S. maltophilia. We experienced a case involving the development of metastatic cellulitis with fulminant and extensive exfoliation in a patient who underwent CBT. Despite controlling the bloodstream infection caused by S. maltophilia, the patient succumbed to secondary fungal infection due to the devastation of the skin barrier. Our case highlights that SSTIs due to S. maltophilia can cause the unexpected development of fulminant metastatic cellulitis with systemic epidermal peeling in severely immunocompromised hosts, including CBT recipients undergoing steroid therapy.

Pseudomonas aeruginosa Promotes Persistence of Stenotrophomonas maltophilia via Increased Adherence to Depolarized Respiratory Epithelium

Stenotrophomonas maltophilia is an emerging opportunistic respiratory pathogen in people with cystic fibrosis (CF). S. maltophilia is frequently observed in polymicrobial infections, and we have previously shown that Pseudomonas aeruginosa promotes colonization and persistence of S. maltophilia in mouse respiratory infections. In this study, we used host and bacterial RNA sequencing to further understand the molecular underpinnings of this interaction. To evaluate S. maltophilia transcript profiles, we used a recently described method for selective capture of bacterial mRNA transcripts with strain-specific RNA probes. We found that factors associated with the type IV pilus, including the histidine kinase subunit of a chemotactic two-component signaling system (chpA), had increased transcript levels during dual-species infection. Using immortalized CF respiratory epithelial cells, we found that infection with P. aeruginosa increases adherence of S. maltophilia, at least in part due to disruption of epithelial tight junctions. In contrast, an isogenic S. maltophilia chpA mutant strain lacked cooperative adherence to CF epithelia and decreased bacterial burden in vivo in dual-species infections with P. aeruginosa. Similarly, P. aeruginosa lacking elastase (lasB) failed to promote S. maltophilia adherence or bacterial colonization and persistence in vivo. Based on these results, we propose that disruption of lung tissue integrity by P. aeruginosa facilitates adherence of S. maltophilia to the lung epithelia, likely in a type IV pilus-dependent manner. These data lend insight into S. maltophilia colonization and persistence in people in later stages of CF disease and may have implications for interactions with other bacterial opportunists. IMPORTANCE Despite advances in treatment options for people with CF, complications of bacterial infections remain the greatest driver of morbidity and mortality in this patient population. These infections often involve more than one bacterial pathogen, and our understanding of how interspecies interactions impact disease progression is lacking. Previous work in our lab found that two CF pathogens, Stenotrophomonas maltophilia and Pseudomonas aeruginosa, can work together in the lung to cause more severe infection. In the present study, we found that infection with P. aeruginosa promotes persistence of S. maltophilia by interfering with epithelial barrier integrity. Depolarization of the epithelial cell layer by P. aeruginosa-secreted elastase increased S. maltophilia adherence, likely in a type IV pilus-dependent manner. Ultimately, this work sheds light on the molecular mechanisms governing an important multispecies interaction seen in pulmonary diseases such as CF.

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.

Carbapenem Resistance among Marine Bacteria-An Emerging Threat to the Global Health Sector

The emergence of antibiotic resistance among pathogenic microorganisms is a major issue for global public health, as it results in acute or chronic infections, debilitating diseases, and mortality. Of particular concern is the rapid and common spread of carbapenem resistance in healthcare settings. Carbapenems are a class of critical antibiotics reserved for treatment against multidrug-resistant microorganisms, and resistance to this antibiotic may result in limited treatment against infections. In addition to in clinical facilities, carbapenem resistance has also been identified in aquatic niches, including marine environments. Various carbapenem-resistant genes (CRGs) have been detected in different marine settings, with the majority of the genes incorporated in mobile genetic elements, i.e., transposons or plasmids, which may contribute to efficient genetic transfer. This review highlights the potential of the marine environment as a reservoir for carbapenem resistance and provides a general overview of CRG transmission among marine microbes.

Comparative proteomic analysis to annotate the structural and functional association of the hypothetical proteins of S. maltophilia k279a and predict potential T and B cell targets for vaccination

Stenotrophomonas maltophilia is a multidrug-resistant bacterium with no precise clinical treatment. This bacterium can be a vital cause for death and different organ failures in immune-compromised, immune-competent, and long-time hospitalized patients. Extensive quorum sensing capability has become a challenge to develop new drugs against this pathogen. Moreover, the organism possesses about 789 proteins which function, structure, and pathogenesis remain obscured. In this piece of work, we tried to enlighten the aforementioned sectors using highly reliable bioinformatics tools validated by the scientific community. At first, the whole proteome sequence of the organism was retrieved and stored. Then we separated the hypothetical proteins and searched for the conserved domain with a high confidence level and multi-server validation, which resulted in 24 such proteins. Furthermore, all of their physical and chemical characterizations were performed, such as theoretical isoelectric point, molecular weight, GRAVY value, and many more. Besides, the subcellular localization, protein-protein interactions, functional motifs, 3D structures, antigenicity, and virulence factors were also evaluated. As an extension of this work, 'RTFAMSSER' and 'PAAPQPSAS' were predicted as potential T and B cell epitopes, respectively. We hope our findings will help in better understating the pathogenesis and smoothen the way to the cure.

Oral Infection Caused by Stenotrophomonas maltophilia: A Rare Presentation of an Emerging Opportunistic Pathogen

Stenotrophomonas maltophilia is an emerging multidrug-resistant opportunistic pathogen with an increasing incidence of nosocomial and community-acquired infection cases, mainly in immunocompromised individuals. Oral cavity infections are rare. To learn more about this infection, a case of oral cavity infection caused by S. maltophilia in an immunosuppressed patient under ventilatory therapy has been presented. The patient presented with multiple nonpainful erosive lesions of the tongue, palate, and oral mucosa. A smear of the oral lesions was performed that revealed the presence of S. maltophilia and Candida albicans, and the patient was treated with fluconazole and sulfamethoxazole associated with trimethoprim in accordance with the antimicrobial susceptibility testing. After 14 days of antibiotic therapy, there were almost no signs of the previous lesions.

Stenotrophomonas maltophilia infections: Clinical characteristics in a military trauma population

Stenotrophomonas maltophilia is a pathogen with unique resistance patterns. We assessed 70 combat casualties with S. maltophilia clinical isolates to examine its role as a nosocomial pathogen in critically-ill trauma patients. Incidence density was 0.36 S. maltophilia infections per 100 patient-days (95% CI: 0.29-0.44). Patients predominantly had blast trauma (97%) and were critically injured (injury severity score [ISS] >25; 80%). Restricting to patients with ISS >15, 50 patients with S. maltophilia infections were compared to 441 patients with infections attributed to other gram-negative bacilli. Patients with S. maltophilia infections had significantly more operating room visits prior to isolation, traumatic or early surgical amputations, longer hospitalization (median 71 vs 47 days), and higher overall mortality (10% vs 2%; P = 0.01). Initial and serial (≥7 days between initial and subsequent isolation) S. maltophilia isolates had high susceptibility to trimethoprim-sulfamethoxazole and minocycline. Evaluation of newer agents awaiting CLSI breakpoints, including moxifloxacin, showed promising results.

The clinical impact of Stenotrophomonas maltophilia bacteremia on the 30-day mortality rate in patients with hematologic disorders: a single-institution experience

OBJECTIVE

Stenotrophomonas maltophilia (SM) is an important nosocomial pathogen, particularly in immunocompromised patients due to their adverse antimicrobial susceptibility pattern. The objective of this article was to investigate the clinical impact of SM bacteremia on the 30-day mortality rate and identify the risk factors of the cause of mortality in patients with hematologic disorders.

METHODS

We retrospectively reviewed the clinical data in patients diagnosed with hematological disorders and SM bacteremia over an 8-year period from July 2010 to July 2018 at a 248-bed hematology department. We compared patients' clinical characteristics and outcomes between the non-survivor and survivor groups.

RESULTS

The overall incidence of SM bacteremia was 25.1 per 10,000 admissions. There were 59 patients (median age: 35 years; 57.6% males) included in the study with an overall SM bacteremia-related 30-day mortality of 44.1%. Multi-drug resistance was common. In vitro susceptibility is higher to ceftazidime (72.9%), ciprofloxacin (66.1%) and cefoperazone/sulbactam (59.3%). The risk factors identified in the univariate analysis were catheter re-implantation, accompanying polymicrobial infection, inadequate initial antimicrobial treatment, APACHE II score, temperature > 39 °C, septic shock, respiratory failure, and non-remission post treatment for primary diseases. Multivariate analysis further confirmed that inadequate initial antimicrobial treatment, respiratory failure, and non-remission after treatment for hematological diseases are independent risk factors associated with mortality (P = 0.001, 0.002 and 0.007, respectively).

CONCLUSIONS

Our study suggests that SM bacteremia is highly associated with increased mortality in patients with hematologic diseases. Early detection, prompt comprehensive management including initiation of combined sensitive antibiotics, respiratory monitoring and support, platelet infusion, and strategies to improve patients' remission status are recommended to improve the overall survival in patients with SM bacteremia.

Skin Infections

Cutaneous infections are common in immunocompromised patients. Neutropenia predisposes patients to fungal, bacterial and viral infections. Antibacterial antifungal and antiviral prophylaxis have caused a significant reduction in some of these infections.

There are two main types of cutaneous infections : primary cutaneous infections and cutaneous manifestations of a disseminated infection. In the latter, skin lesions may be the window to disseminated bloodstream infection and the first and only evidence of a disseminated life threatening infection.

The diagnosis may be at your fingertips; therefore a thorough skin exam is the clue. However, it’s also important to know the characteristic lesions associated with different infections. It will help expedite diagnosis so appropriate treatment is initiated promptly in neutropenic patients, which can be lifesaving.

In a retrospective study of 43 neutropenic febrile patients with cutaneous lesions, fungal infections were the most frequent, and nodular lesions on the lower extremities were the most prevalent (Naorungroj and Aiempanakit, J Am Acad Dermatol 74:AB166, 2016).

Skin biopsy for pathological study and culture remains the gold standard and should be obtained early to confirm the suspected diagnosis. In these immunocompromised patients the inflammatory response is altered by either the primary disease or its treatment. Therefore, routine pathogens may present in an atypical fashion, with diminished or absent induration, erythema, or pustulation in response to bacterial resulting cutaneous infection without typical cellulitis (Urabe, Clin Infect Dis 39:S53–S55, 2004). Skin lesions are evaluated not only by morphology, but also in the context of the clinical setting and biopsy result. The skin biopsy is inexpensive, relatively noninvasive and without contraindication, and may avoid the need for more invasive procedures such an open lung biopsy (Grossman, et al., Cutaneous manifestations of infection in the immunocompromised host. Springer Science+Business Media, LLC, New York, 2012).

In addition to antimicrobial therapy, surgery should not be postponed in the face of progressive skin and soft tissue infection in this population (Brzozowski and Ross, J Hand Surg Br 22:679–680, 1997).

Identification of immunogenic outer membrane proteins and evaluation of their protective efficacy against Stenotrophomonas maltophilia

Background

Stenotrophomonas maltophilia (S. maltophilia) is an emerging global multiple-drug-resistant organism. It becomes increasingly challenging to treat S. maltophilia infection effectively. Novel therapeutic and preventive approaches targeting S. maltophilia infection are still lacking. This study aims to isolate outer membrane proteins (Omps) from S. maltophilia and use immunoproteomic technology to identify potential vaccine candidates of Omps against S. maltophilia infections.

Methods

Omps from S. maltophilia culture were separated by two-dimensional electrophoresis and identified by matrix-assisted laser desorption/ionization time of flight mass spectrometry and nano liquid chromatography coupled fourier transform ion cyclotron resonance tandem mass spectrometry. Recombinant Omps were prepared and used to immunize mice, and the potency of mouse anti-Omp serum was tested in opsonophagocytic killing assay (OPKA). The effects of immunization with recombinant Omp on blood and tissue bacterial loads in a mouse model of S. maltophilia-induced infection were analyzed.

Results

Outer membrane protein A (OmpA) and Smlt4123 were identified by mass spectrometry. Mouse anti-Smlt4123 serum significantly reduced the bacterial counts in healthy individuals’ blood in OPKA (P < 0.05) but mouse anti-OmpA serum did not. Enzyme-linked immunosorbent assay revealed that the antibody subtype of mouse anti-Smlt4123 antibody was IgG1. Eight hours after an intraperitoneal challenge with S. maltophilia, the bacterial loads in mouse blood were significantly lower in the mice receiving immunization with recombinant Smlt4123 than in the control mice receiving no immunization (P < 0.05), whereas the bacterial loads in other organs, such as the liver, spleen, lung, and kidney were similar in the two groups.

Conclusions

The results revealed that the immunoproteomic approach was an efficient way to screen the immunogenic protein of Stenotrophomonas maltophilia. Moreover, the recombinant Smlt4123 had potential to protect mice from bacteremia caused by S. maltophilia in the early stages.

Electronic supplementary material

The online version of this article (10.1186/s12879-018-3258-7) contains supplementary material, which is available to authorized users.

Stenotrophomonas maltophilia Necrotizing Soft Tissue Infection in an Immunocompromised Patient

Introduction

To report on the first recorded case of necrotizing soft tissue infection (NSTI) in an immunocompromised individual caused by Stenotrophomonas maltophilia in the Western Hemisphere and highlight the challenges that medical providers face in promptly diagnosing and treating NSTI in this highly vulnerable patient population.

Case Presentation

We report a case of NSTI caused by S. maltophilia in a neutropenic patient admitted for treatment of acute lymphoblastic leukemia. The patient presented with laboratory and clinical findings atypical for a NSTI that may have confounded its diagnosis and delayed surgical intervention. Despite aggressive medical care and surgical debridement, the patient unfortunately passed away due to overwhelming septic shock.

Conclusions

Providers should consider atypical organisms as causative in NSTI in immunocompromised patients and recognize that these patients may present without classic clinical and laboratory findings.

Stenotrophomonas maltophilia as an Emerging Ubiquitous Pathogen: Looking Beyond Contemporary Antibiotic Therapy

Stenotrophomonas maltophilia is a commensal and an emerging pathogen earlier noted in broad-spectrum life threatening infections among the vulnerable, but more recently as a pathogen in immunocompetent individuals. The bacteria are consistently being implicated in necrotizing otitis, cutaneous infections including soft tissue infection and keratitis, endocarditis, meningitis, acute respiratory tract infection (RTI), bacteraemia (with/without hematological malignancies), tropical pyomyositis, cystic fibrosis, septic arthritis, among others. S. maltophilia is also an environmental bacteria occurring in water, rhizospheres, as part of the animals' microflora, in foods, and several other microbiota. This review highlights clinical reports on S. maltophilia both as an opportunistic and as true pathogen. Also, biofilm formation as well as quorum sensing, extracellular enzymes, flagella, pili/fimbriae, small colony variant, other virulence or virulence-associated factors, the antibiotic resistance factors, and their implications are considered. Low outer membrane permeability, natural MDR efflux systems, and/or resistance genes, resistance mechanisms like the production of two inducible chromosomally encoded β-lactamases, and lack of carefully compiled patient history are factors that pose great challenges to the S. maltophilia control arsenals. The fluoroquinolone, some tetracycline derivatives and trimethoprim-sulphamethaxole (TMP-SMX) were reported as effective antibiotics with good therapeutic outcome. However, TMP-SMX resistance and allergies to sulfa together with high toxicity of fluoroquinolone are notable setbacks. S. maltophilia's production and sustenance of biofilm by quorum sensing enhance their virulence, resistance to antibiotics and gene transfer, making quorum quenching an imperative step in Stenotrophomonas control. Incorporating several other proven approaches like bioengineered bacteriophage therapy, Epigallocatechin-3-gallate (EGCG), essential oil, nanoemulsions, and use of cationic compounds are promising alternatives which can be incorporated in Stenotrophomonas control arsenal.

BsmR degrades c-di-GMP to modulate biofilm formation of nosocomial pathogen Stenotrophomonas maltophilia

c-di-GMP is a cellular second messenger that regulates diverse bacterial processes, including swimming, biofilm formation and virulence. However, in Stenotrophomonas maltophilia, a nosocomial pathogen that frequently infects immunodeficient or immunoincompetent patients, the regulatory function of c-di-GMP remains unclear. Here we show that BsmR is a negative regulator of biofilm development that degrades c-di-GMP through its EAL domain. Increasing BsmR expression resulted in significant increase in bacterial swimming and decrease in cell aggregation. BsmR regulates the expression of at least 349 genes. Among them, 34 involved in flagellar assembly and a flagellar-assembly-related transcription factor (fsnR) are positively regulated. Although BsmR is a response regulator of the two-component signaling system, its role in biofilm formation depends on the expression level of its respective gene (bsmR), not on the protein’s phosphorylation level. A transcription factor, BsmT, whose coding gene is located in the same tetra-cistronic operon as bsmR, was shown to directly bind to the promoter region of the operon and, through a positive regulatory loop, modulate bsmR transcription. Thus, our results revealed that the c-di-GMP signaling pathway controls biofilm formation and swimming in S. maltophilia, suggesting c-di-GMP signaling as a target in the development of novel antibacterial agents to resist this pathogen.

Skin and Soft Tissue Infections

The skin is colonized by a diverse collection of microorganisms which, for the most part, peacefully coexist with their hosts. Skin and soft tissue infections (SSTIs) encompass a variety of conditions; in immunocompromised hosts, SSTIs can be caused by diverse microorganisms-most commonly bacteria, but also fungi, viruses, mycobacteria, and protozoa. The diagnosis of SSTIs is difficult because they may commonly masquerade as other clinical syndromes or can be a manifestation of systemic disease. In immunocompromised hosts, SSTI poses a major diagnostic challenge, and clinical dermatological assessment should be initially performed; to better identify the pathogen and to lead to appropriate treatment, etiology should include cultures of lesions and blood, biopsy with histology, specific microbiological analysis with special stains, molecular techniques, and antigen-detection methodologies. Here, we reviewed the epidemiology, pathophysiology, clinical presentation, and diagnostic techniques, including molecular biological techniques, used for SSTIs, with a focus on the immunocompromised host, such as patients with cellular immunodeficiency, HIV, and diabetic foot infection.

Computed Tomography Findings of Community-Acquired Stenotrophomonas Maltophilia Pneumonia in an Immunocompetent Patient: A Case Report

Stenotrophomonas maltophilia (S. maltophilia) is a rare, but globally emerging gram-negative multiple-drug-resistant organism usually found in a nosocomial setting in immunocompromised patients. To our best knowledge, computed tomography (CT) features of community-acquired S. maltophilia pneumonia have not been previously reported in an immunocompetent patient. Herein, we presented the CT findings of a previous healthy 56-year-old male with S. maltophilia pneumonia.

Quality of Drinking Water Treated at Point of Use in Residential Healthcare Facilities for the Elderly

Municipal tap water is increasingly treated at the point of use (POU) to improve the acceptability and palatability of its taste. The aim of this study was to assess the bacteriologic and nutritional characteristics of tap water treated at the point of use in residential healthcare facilities for the elderly. Two types of POU devices were used: microfiltered water dispensers (MWDs) and reverse-osmosis water dispensers (ROWDs). All samples of water entering the devices and leaving them were tested for the bacteriological parameters set by Italian regulations for drinking water and for opportunistic pathogens associated with various infections in healthcare settings; in addition, the degree of mineralization of the water was assessed. The results revealed widespread bacterial contamination in the POU treatment devices, particularly from potentially pathogenic species. As expected, the use of ROWDs led to a decrease in the saline content of the water. In conclusion, the use of POU treatment in healthcare facilities for the elderly can be considered advisable only if the devices are constantly and carefully maintained.

An overview of various typing methods for clinical epidemiology of the emerging pathogen Stenotrophomonas maltophilia

Typing of bacterial isolates has been used for decades to study local outbreaks as well as in national and international surveillances for monitoring newly emerging resistant clones. Despite being recognized as a nosocomial pathogen, the precise modes of transmission of Stenotrophomonas maltophilia in health care settings are unknown. Due to the high genetic diversity observed among S. maltophilia clinical isolates, the typing results might be better interpreted if also environmental strains were included. This could help to identify preventative measures to be designed and implemented for decreasing the possibility of outbreaks and nosocomial infections. In this review, we attempt to provide an overview on the most common typing methods used for clinical epidemiology of S. maltophilia strains, such as PCR-based fingerprinting analyses, pulsed-field gel electrophoresis, multilocus variable number tandem repeat analysis, and multilocus sequence type. Application of the proteomic-based mass spectrometry by matrix-assisted laser desorption ionization-time of flight is also described. Improvements of typing methods already in use have to be achieved to facilitate S. maltophilia infection control at any level. In the near future, when novel Web-based platforms for rapid data processing and analysis will be available, whole genome sequencing technologies will likely become a highly powerful tool for outbreak investigations and surveillance studies in routine clinical practices.

Aetiology, source and prevention of waterborne healthcare-associated infections: a review

The purpose of this review is to discuss the scientific literature on waterborne healthcare-associated infections (HCAIs) published from 1990 to 2012. The review focuses on aquatic bacteria and describes both outbreaks and single cases in relation to patient characteristics, the settings and contaminated sources. An overview of diagnostic methods and environmental investigations is summarized in order to provide guidance for future case investigations. Lastly, on the basis of the prevention and control measures adopted, information and recommendations are given. A total of 125 reports were included, 41 describing hospitalized children. All cases were sustained by opportunistic pathogens, mainly Legionellaceae, Pseudomonadaceae and Burkholderiaceae. Hot-water distribution systems were the primary source of legionnaires’ disease, bottled water was mainly colonized by Pseudomonaceae, and Burkholderiaceae were the leading cause of distilled and sterile water contamination. The intensive care unit was the most frequently involved setting, but patient characteristics were the main risk factor, independent of the ward. As it is difficult to avoid water contamination by microbes and disinfection treatments may be insufficient to control the risk of infection, a proactive preventive plan should be put in place. Nursing staff should pay special attention to children and immunosuppressed patients in terms of tap-water exposure and also their personal hygiene, and should regularly use sterile water for rinsing/cleaning devices.

The role of water in healthcare-associated infections

PURPOSE OF REVIEW

The aim is to discuss the epidemiology of infections that arise from contaminated water in healthcare settings, including Legionnaires' disease, other Gram-negative pathogens, nontuberculous mycobacteria, and fungi.

RECENT FINDINGS

Legionella can colonize a hospital water system and infect patients despite use of preventive disinfectants. Evidence-based measures are available for secondary prevention. Vulnerable patients can develop healthcare-associated infections with waterborne organisms that are transmitted by colonization of plumbing systems, including sinks and their fixtures. Room humidifiers and decorative fountains have been implicated in serious outbreaks, and pose unwarranted risks in healthcare settings.

SUMMARY

Design of hospital plumbing must be purposeful and thoughtful to avoid the features that foster growth and dissemination of Legionella and other pathogens. Exposure of patients who have central venous catheters and other invasive devices to tap water poses a risk for infection with waterborne pathogens. Healthcare facilities must conduct aggressive clinical surveillance for Legionnaires' disease and other waterborne infections in order to detect and remediate an outbreak promptly. Hand hygiene is the most important measure to prevent transmission of other Gram-negative waterborne pathogens in the healthcare setting.

Stenotrophomonas maltophilia: an emerging global opportunistic pathogen

Stenotrophomonas maltophilia is an emerging multidrug-resistant global opportunistic pathogen. The increasing incidence of nosocomial and community-acquired S. maltophilia infections is of particular concern for immunocompromised individuals, as this bacterial pathogen is associated with a significant fatality/case ratio. S. maltophilia is an environmental bacterium found in aqueous habitats, including plant rhizospheres, animals, foods, and water sources. Infections of S. maltophilia can occur in a range of organs and tissues; the organism is commonly found in respiratory tract infections. This review summarizes the current literature and presents S. maltophilia as an organism with various molecular mechanisms used for colonization and infection. S. maltophilia can be recovered from polymicrobial infections, most notably from the respiratory tract of cystic fibrosis patients, as a cocolonizer with Pseudomonas aeruginosa. Recent evidence of cell-cell communication between these pathogens has implications for the development of novel pharmacological therapies. Animal models of S. maltophilia infection have provided useful information about the type of host immune response induced by this opportunistic pathogen. Current and emerging treatments for patients infected with S. maltophilia are discussed.

Stenotrophomonas maltophilia: emerging disease patterns and challenges for treatment

Stenotrophomonas maltophilia is a ubiquitous organism associated with opportunistic infections. In the immunocompromised host, increasing prevalence and severity of illness is observed, particularly opportunistic bloodstream infections and pneumonia syndromes. In this article, the classification and microbiology are outlined, together with clinical presentation, outcomes and management of infections due to S. maltophilia. Although virulence mechanisms and the genetic basis of antibiotic resistance have been identified, a role for standardized and uniform reporting of antibiotic sensitivity is not defined. Infections due to S. maltophilia have traditionally been treated with trimethoprim-sulfamethoxazole, ticarcillin-clavulanic acid, or fluoroquinolone agents. The use of combination therapies, newer fluoroquinolone agents and tetracycline derivatives is discussed. Finally, measures to prevent transmission of S. maltophilia within healthcare facilities are reported, especially in at-risk patient populations.

Attributable mortality of Stenotrophomonas maltophilia infections: a systematic review of the literature

AIM

Although Stenotrophomonas maltophilia is commonly isolated from clinical specimens, mainly of immunocompromised patients, mortality directly attributable to this organism is controversial. We searched PubMed, Scopus and Cochrane and assessed the available literature regarding mortality attributable to infection with S. maltophilia.

METHOD

Crude mortality and mortality of case patients receiving appropriate or inappropriate initial antibiotic treatment were evaluated. A total of 15 articles (six matched case-control, seven case-control and two controlled cohort studies) were identified; 13 studies (the six matched case-control and the seven case-control studies) were included in the analysis.

RESULTS

In seven studies, mortality of cases differed significantly from that of controls. Mortality was significantly higher in cases than controls in six of these studies; it was lower in cases than controls in the one study where controls had Pseudomonas aeruginosa bacteremia. In six studies, mortality of cases did not differ significantly compared with the respective controls. In three of four studies providing relevant data, mortality of cases treated with inappropriate initial antibiotic treatment was significantly higher compared with cases treated with appropriate initial antibiotic treatment.

CONCLUSION

A considerable mortality rate (up to 37.5%) can be attributed to S. maltophilia infection. Thus, clinicians should not underestimate the clinical significance of S. maltophilia infections.

Ecthyma Gangrenosum: A Rare Cutaneous Manifestation Caused by Stenotrophomonas maltophilia in a Leukemic Patient

Ecthyma gangrenosum (EG) is a well-recognized cutaneous infection that most commonly affects immunocompromised patients. It typically occurs on the extremities, or in gluteal and perineal regions. Although Pseudomonas aeruginosa is the most well-known pathogen causing EG, other organisms have been reported to cause EG. Herein we report a rare case of ecthyma gangrenosum presenting as aggressive necrotic skin lesions in perioral and infraorbital areas in a 47-year-old patient with acute myelocytic leukemia after allogeneic bone marrow transplantation. It was caused by Stenotrophomonas maltophilia, which is an aerobic, gram-negative pathogen that has been associated only rarely with cutaneous disease. Blood culture and tissue culture were positive for S. maltophilia. Histological examination revealed numerous tiny bacilli in the dermis and perivascular area. Early recognition of skin lesions caused by S. maltophilia is important to decrease associated mortality in immunosuppressed patients.

Lethal Pulmonary Hemorrhage Caused by a FulminantStenotrophomonas maltophiliaRespiratory Infection in an Acute Myeloid Leukemia Patient

Stenotrophomonas maltophilia (Sm) pneumonia in immunocompromized hosts is an increasingly common nosocomial infection. Even though resistant to multiple antimicrobials, this gram-negative bacteria usually does not present with a fulminant course leading to a fatal hemorrhagic respiratory infection in neutropenic patients. We report here the case of a 63-year-old woman treated by intensive chemotherapy for acute myeloid leukemia (AML) who presented while severely neutropenic and thrombocytopenic a Sm pulmonary infection with hemoptysis leading to death in 48 h. The bronchoalveolar lavage (BAL) performed shortly before death was highly hemorrhagic and contained a striking amount of extra- and intra-cellular pathogens. Blood and BAL cultures grew S. maltophilia. Post-mortem examination revealed bilateral extensive intra-alveolar hemorrhage (IAH) associated with a great amount of microorganisms and severe bone marrow aplasia was observed without evidence of leukemia residual disease. Sm pneumonia usually does not evolve into such a devastating clinical picture although infections due to the bacteria are known to be associated with high morbidity and mortality. So far, the present observation is the fourth similar case reported in the literature. Even though an early diagnosis and an adequate antibiotic prescription may improve Sm infection prognosis, S. maltophilia proves difficult to eradicate due to a high resistance rate in part intrinsic but also in part acquired.

Acute upper airway obstruction caused by Stenotrophomonas maltophilia soft tissue infection

A previously healthy 71-y-old male developed acute upper airway obstruction caused by a Stenotrophomonas maltophilia infection of the mucocutaneous and soft tissue of the neck. Ventilator support was provided via a small-calibre endotracheal tube. Stenotrophomonas was susceptible only to levofloxacin and cotrimoxazole. Antibiotic therapy rapidly improved the soft tissue oedema, allowing extubation and discharge from the intensive care unit.

The versatility and adaptation of bacteria from the genus Stenotrophomonas

The genus Stenotrophomonas comprises at least eight species. These bacteria are found throughout the environment, particularly in close association with plants. Strains of the most predominant species, Stenotrophomonas maltophilia, have an extraordinary range of activities that include beneficial effects for plant growth and health, the breakdown of natural and man-made pollutants that are central to bioremediation and phytoremediation strategies and the production of biomolecules of economic value, as well as detrimental effects, such as multidrug resistance, in human pathogenic strains. Here, we discuss the versatility of the bacteria in the genus Stenotrophomonas and the insight that comparative genomic analysis of clinical and endophytic isolates of S. maltophilia has brought to our understanding of the adaptation of this genus to various niches.

Control of Pseudomonas aeruginosa and Stenotrophomonas maltophilia contamination of microfiltered water dispensers with peracetic acid and hydrogen peroxide

The abilities of peracetic acid and hydrogen peroxide to remove or reduce Pseudomonas aeruginosa and Stenotrophomonas maltophilia in output water from microfiltered water dispensers (MWDs) were investigated. Two MWDs were inoculated with strains of P. aeruginosa and S. maltophilia isolated from water. Dispensers A and B were disinfected with 10% (v/v) peracetic acid (PAA) and 3% (v/v) hydrogen peroxide (HP) respectively. Each dispenser was disinfected three times at monthly intervals with contact times of 10, 30 and 40 min. Water dispensed by the MWDs was collected immediately before and after each treatment and then twice weekly for the remaining period. Once a week a sample of the tap water entering the dispensers was tested. P. aeruginosa and S. maltophilia were enumerated in the 90 samples collected during 6 months. In the output water from the dispensers before the first treatment, the number of the bacteria was 3 to 4 log cfu/100 mL. Treatment with PAA greatly reduced the numbers of P. aeruginosa and S. maltophilia in the dispensed water initially. However, by 2 days after treatment, the numbers increased and remained high. In the case of disinfection with HP for 40 min, P. aeruginosa was not detected in most of the samples (73.7%). Numbers of S. maltophilia decreased with increasing time after treatment.

Stenotrophomonas maltophilia infections of intact skin: a systematic review of the literature

To highlight the importance of intact skin infection syndromes caused by Stenotrophomonas maltophilia, we review 17 reported cases. Skin infection syndrome presentations included metastatic cellulitis (58%), primary cellulitis (23%), and ecthyma gangrenosum (17%). Associated risk factors were hematologic malignancies and chemotherapy (94%), neutropenia (94%), presence of central venous catheter (17%), and exposure to broad-spectrum antibiotics (84%). The diagnosis was supported by cultures of skin biopsy specimens (35%), blood cultures (24%), or both (41%). Trimethoprim-sulfamethoxazole was the treatment of choice (76%), and outcomes were favorable (71%).

Salvage of long-term central venous catheters during an outbreak of Pseudomonas putida and Stenotrophomonas maltophilia infections associated with contaminated heparin catheter-lock solution

OBJECTIVE

To describe the management of patients with long-term central venous catheters (CVCs) during an outbreak of infection due to Pseudomonas putida and Stenotrophomonas maltophilia associated with contaminated heparin catheter-lock solution.

DESIGN

Descriptive study.

SETTING

Private, 250-bed tertiary-care hospital.

METHODS

In March 2003, we identified 2 febrile cancer patients with P. putida bacteremia. Over 2 days, 7 cases of bacteremia were identified; lots of syringes prefilled with heparin catheter-lock solution, supplied by a compounding pharmacy, were recalled and samples were cultured. More cases of bacteremia appeared during the following days, and any patient who had had a catheter lock infused with the suspect solution was asked to provide blood samples for culture, even if the patient was asymptomatic. Isolates that were recovered from culture were typed by pulsed-field gel electrophoresis. Antimicrobial salvage treatment of long-term CVCs was attempted.

RESULTS

A total of 154 patients had had their catheter lock infused with solution from the lots that were suspected of being contaminated. Only 48 of these patients had CVCs. By day 7 of the outbreak, 18 of these patients had become symptomatic. Twenty-six of the remaining 30 asymptomatic patients then also provided blood samples for culture, 10 of whom developed fever shortly after samples were collected. Thirty-two patients were identified who had P. putida bacteremia; 9 also had infection due to S. maltophilia. Samples from 1 of the 3 lots of prefilled syringes in use at the time of the outbreak also grew P. putida on culture. Molecular typing identified 3 different clones of P. putida from patients and heparin catheter-lock solution, and 1 clone of S. maltophilia. A total of 27 patients received antimicrobial therapy regimens, some of which included decontamination of the catheter lock with anti-infective lock solution. Of 27 patients, 19 (70%) retained their long-term CVC during the 6-month follow-up period.

CONCLUSIONS

To our knowledge, this is one of the largest prospective experiences in the management of bloodstream infection associated with long-term CVCs. The infections were caused by gram-negative bacilli and were managed without catheter removal, with a high response rate. We emphasize the risks of using intravenous formulations of medications supplied by compounding pharmacies that produce large quantities of drugs.

Antimicrobial therapy for Stenotrophomonas maltophilia infections

Stenotrophomonas maltophilia has emerged as an important nosocomial pathogen capable of causing respiratory, bloodstream, and urinary infections. The treatment of nosocomial infections by S. maltophilia is difficult, as this pathogen shows high levels of intrinsic or acquired resistance to different antimicrobial agents, drastically reducing the antibiotic options available for treatment. Intrinsic resistance may be due to reduced outer membrane permeability or to the multidrug efflux pumps. However, specific mechanisms of resistance such as aminoglycoside-modifying enzymes or the heterogeneous production of metallo-beta-lactamase have contributed to the multidrug-resistant phenotype displayed by this pathogen. Moreover, the lack of standardized susceptibility tests and their interpretative criteria hinder the choice of an adequate antibiotic treatment. Recommendations for the treatment of infections by S. maltophilia are based on in vitro studies, certain nonrandomized clinical trials, and anecdotal experience. Trimethoprim-sulfamethoxazole remains the drug of choice, although in vitro studies indicate that ticarcillin-clavulanic acid, minocycline, some of the new fluoroquinolones, and tigecycline may be useful agents. This review describes the main resistance mechanisms, the in vitro susceptibility profile, and treatment options for S. maltophilia infections.

Pseudooutbreak of Stenotrophomonas maltophilia bacteremia in a general ward

BACKGROUND

Stenotrophomonas maltophilia is a significant nosocomial pathogen and is commonly isolated in the hospital environment. We investigated the risk factors for a bloodstream pseudooutbreak of S maltophilia in a general ward.

METHODS

On November 24 and 25, 2005, 7 patients without evidence of sepsis were reported as positive for blood culture with S maltophilia from blood samples collected on November 21 and 22, 2005. We conducted an epidemiologic investigation and a case-control study of this pseudooutbreak.

RESULTS

All 7 S maltophilia showed the same antibiogram and an indistinguishable pattern on pulsed-field gel electrophoresis. The observational study revealed multiple lapses in infection control, including multiple use of a single bottle of saline for dilution of antibiotics. A case-control study showed that one health care worker, who collected blood samples from 6 of 7 patients, was a significant risk factor for the pseudooutbreak of S maltophilia (P < .05).

CONCLUSION

We suggest that the combination of multiple lapses in infection control and the blood-collecting behavior of a health care worker might be the cause of the pseudooutbreak of S maltophilia.

Skin Manifestation of Stenotrophomonas maltophilia Infection – A Case Report and Review Article

Introduction: Stenotrophomonas maltophilia is an aerobic gram-negative bacillus that is a frequent coloniser of fluids used in the hospital setting. It causes infection in immunosuppressed hosts, especially those who are neutropaenic, on chemotherapy and broad spectrum antibiotics. Skin and soft tissue manifestations of Stenotrophomonas maltophilia infection are becoming an increasingly recognised entity; the clinical spectrum ranges from mucocutaneous, skin to soft tissue infections. Materials and Methods: We present a case of an 8-year-old girl with acute myeloid leukaemia who developed metastatic skin lesions secondary to Stenotrophomonas maltophilia bacteraemia. The authors reviewed a total of 24 reported cases of mucocutaneous, skin and soft tissue infections by Stenotrophomonas maltophilia. The presentations include metastatic cellulitis, primary cellulitis and infected mucocutaneous ulcers. Results: This is the first locally reported case of metastatic nodular skin lesions caused by Stenotrophomonas maltophilia bacteraemia. This is also the first reported paediatric case of embolic skin lesions caused by Stenotrophomonas maltophilia. Of the 6 cases of Stenotrophomonas maltophilia bacteraemia seen in the paediatric oncology patients from year 2000 to 2004 at our hospital, only 1 case developed metastatic skin lesions. Conclusion: Stenotrophomonas maltophilia skin infection should be included into the list of differential diagnoses for metastatic skin lesions in neutropaenic patients, especially with an underlying haematologic malignancy who has received recent chemotherapy and broad spectrum antibiotics. Haematologic malignancy, transplantation, neutropaenic, immunosuppressive therapy and a high severity of illness score were important prognostic factors.

Stenotrophomonas maltophilia: the significance and role as a nosocomial pathogen

Stenotrophomonas maltophilia is a significant pathogen that primarily affects patients with co-morbid illnesses, usually malignancies, who have been hospitalized for prolonged periods and received broad-spectrum antibiotic therapy. The organism has been associated with an expanding spectrum of clinical manifestations associated with high case to fatality ratios. Therapy of these infections presents a significant challenge both for the clinician and the microbiologists because of its high-level antibiotic resistance to most of the currently used agents and methodological difficulties in susceptibility testing with this organism.

Outbreak of extended spectrum beta-lactamase-producing Klebsiella pneumoniae infection in a neonatal intensive care unit related to onychomycosis in a health care worker

Four cases of infection by extended spectrum beta-lactamase-producing Klebsiella pneumoniae occurred in the neonatal intensive care unit. Isolation, empiric therapy change and education produced no effect. Newborn weekly colonization rates were 0-18.7%. One health care worker with onychomycosis was positive for extended spectrum beta-lactamase-producing K. pneumoniae. Isolates were identical by molecular typing. Outbreak was controlled when the health care worker was excluded from the neonatal intensive care unit.

Stenotrophomonas maltophilia: a serious and rare complication in patients suffering from burns

Stenotrophomonas maltophilia is rarely implicated in clinical infections but it constitutes a significant nosocomial pathogen, especially in immunocompromised patients. This report describes the first case of a generalised infection caused by S. maltophilia that included bacteremia, wound and respiratory tract infection in a patient suffering from burns. Given the emergence of S. maltophilia nosocomial infections, especially in patients with burns, isolation of the bacterium from blood cultures should prompt the commencement of adequate antibiotic treatment.