Pseudomonas infections in patients with AIDS and AIDS-related complex

An investigation of clinical characteristics and antimicrobial agent susceptibility patterns in clinical Comamonas testosteroni isolates: An increasingly prevalent nosocomial pathogen

BACKGROUND

Comamonas testosteroni is a gram-negative bacillus, known before 1987 as Pseudomonas testosteroni. Although considered as a rare pathogen, its frequency has been increasing. Data regarding its antibiotic susceptibility are insufficient. To date, forty-four cases have been reported in the literature. In this study, we identified the C. testosteroni infections observed in our hospital and evaluated their antimicrobial agent susceptibility patterns compared with cases reported in the literature.

METHODS

For the purposes of the present study, patients admitted to hospital between November 2019 and December 2020 were screened. Those with clinical and laboratory signs of infection with positive C. testosteroni growth in culture were enrolled. Clinical isolates obtained from the samples processed in accordance with standard microbiological examination procedures in our laboratory were defined by MALDI-TOF mass spectrometry with 99.9% probability as C. testosteroni.

RESULTS

C testosteroni infection was detected between November 2019 and December 2020 in eight patients in our hospital. Six of them had a bloodstream infection (BSI), one had pneumonia, and one had urinary tract infection due to C. testosteroni. Coexistence of COVID-19 was detected in four patients. Six out of the eight cases with BSI had hospital-acquired infection and all of the infections were healthcare-associated. When antimicrobial agent susceptibility results reported in the literature were evaluated in combination with the current results, ceftazidime and meropenem were found to be the most susceptible agents (96.1% and 80%, respectively).

CONCLUSIONS

The frequency of nosocomial C. testosteroni infections and resistance to antimicrobial agents are gradually increasing. While resistance to carbapenems is on the upswing, third-generation cephalosporins are still seen as suitable treatment options.

Clinical features, risk factors, and antimicrobial resistance of pseudomonas putida isolates

Pseudomonas putida rarely results in infection, primarily in patients undergoing invasive procedures or immunocompromised hosts. We aimed to investigate the characteristics of Pseudomonas putida infections. This is a retrospectively designed cross-sectional observational study. We retrospectively scanned the data from our hospital for the 10 years before February 15, 2022. The patients with Pseudomonas putida growth in the microbiological cultures and with antibiotic susceptibility tests were included in the study. We recorded culture isolates types, age, gender, comorbidities, immunosuppressive factors, symptoms, invasive medical procedures, length of hospital stay, and radiological findings. The mean age of the patients was 66.2 ± 14.5 years, and the male patients predominated (76.3%, n = 58/76). There was growth in bronchial lavage in 33 patients, sputum in 28, pleural effusion fluid in 12, and tracheal aspirate in 3 patients. The rate of antibiotic-resistant strains was 56.6% (n = 43). All strains were sensitive to colistin (100%), and carbapenem, amikacin, and gentamicin sensitivity rates were high. We observed that the risk of antibiotic resistance increased 4.29 times in the patients in the intensive care unit (Cl:1.27-14.47, P = .01). The patients with Diabetes Mellitus had a higher risk (OR 4.33, Cl:1.11-16.77, P = .03), and in cancer cases, the risk was 3.31 times higher (Cl:1.06-10.32, P = .03). The risk of Pseudomonas putida infection should be considered, particularly in patients with comorbid disorders causing immunosuppression, including Diabetes Mellitus and Cancer.

The Emergence of the Genus Comamonas as Important Opportunistic Pathogens

Comamonas spp. are non-fermenting Gram-negative bacilli. They were first discovered in 1894, and since then, twenty-four species have been characterized. The natural habitat of these bacteria is soil, wastewater/sludge, fresh water such as ponds and rivers, and the animal intestinal microbiome. They were also isolated from industrial settings, such as activated sludge and polluted soil, and from the hospital environment and clinical samples, such as urine, pus, blood, feces, and kidney. Comamonas spp. are associated with environmental bioremediation and are considered an important environmental bacterium rather than a human pathogen. However, in the 1980s, they became a concern when several human infections associated with these species were reported. Here, the Comamonas genus was examined in terms of its members, identification techniques, and pathogenicity. Seventy-seven infection cases associated with these microorganisms that have been discussed in the literature were identified and investigated in this project. All relevant information regarding year of infection, country of origin, patient information such as age, sex, underlying medical conditions if any, type of infection caused by the Comamonas species, antibiotic susceptibility testing, treatment, and outcomes for the patient were extracted from case reports. The findings suggest that even though Comamonas spp. are thought of as being of low virulence, they have caused harmful health conditions in many healthy individuals and even death in patients with underlying conditions. Antimicrobial treatment of infections associated with these species, in general, was not very difficult; however, it can become an issue in the future because some strains are already resistant to different classes of antibiotics. Therefore, these pathogens should be considered of such importance that they should be included in the hospital screening programs.

Genomic Analysis of Carbapenem-Resistant Comamonas in Water Matrices: Implications for Public Health and Wastewater Treatments

Comamonas spp. are Gram-negative bacteria that catabolize a wide range of organic and inorganic substrates. Comamonas spp. are abundant in aquatic and soil environments, including wastewater, and can cause opportunistic infections in humans. Because of their potential in wastewater bioaugmentation and bioremediation strategies, the identification of Comamonas species harboring genes encoding carbapenemases and other clinically important antibiotic resistance genes warrant further investigation. Here, we present an analysis of 39 whole-genome sequences comprising three Comamonas species from aquatic environments in South Australia that were recovered on media supplemented with carbapenems. The analysis includes a detailed description of 33 Comamonas denitrificans isolates, some of which carried chromosomally acquired bla_GES-5, bla_OXA, and aminoglycoside resistance (aadA) genes located on putative genomic islands (GIs). All bla_GES-5- and bla_OXA-containing GIs appear to be unique to this Australian collection of C. denitrificans. Notably, most open reading frames (ORFs) within the GIs, including all antimicrobial resistance (AMR) genes, had adjacent attC sites, indicating that these ORFs are mobile gene cassettes. One C. denitrificans isolate carried an IncP-1 plasmid with genes involved in xenobiotic degradation and response to oxidative stress. Our assessment of the sequences highlights the very distant nature of C. denitrificans to the other Comamonas species and its apparent disposition to acquire antimicrobial resistance genes on putative genomic islands. IMPORTANCE Antimicrobial resistance (AMR) poses a global public health threat, and the increase in resistance to "last-resort drugs," such as carbapenems, is alarming. Wastewater has been flagged as a hot spot for AMR evolution. Comamonas spp. are among the most common bacteria in wastewater and play a role in its bioaugmentation. While the ability of Comamonas species to catabolize a wide range of organic and inorganic substrates is well documented, some species are also opportunistic pathogens. However, data regarding AMR in Comamonas spp. are limited. Here, through the genomic analyses of 39 carbapenem-resistant Comamonas isolates, we make several key observations, including the identification of a subset of C. denitrificans isolates that harbored genomic islands encoding carbapenemase bla_GES-5 or extended-spectrum β-lactamase bla_OXA alleles. Given the importance of Comamonas species in potential wastewater bioaugmentation and bioremediation strategies, as well as their status as emerging pathogens, the acquisition of critically important antibiotic resistance genes on genomic islands warrants future monitoring.

Enhanced Eradication of Mucin-Embedded Bacterial Biofilm by Locally Delivered Antibiotics in Functionalized Microcontainers

Bacterial biofilm-related infections are difficult to eradicate and require repeated treatments with high doses of antibiotics. Thus, there is an urgent need for new treatment strategies that minimize the use of antibiotics while enhancing biofilm eradication. Functionalized reservoir-based microdevices, such as, microcontainers (MCs), offer, high drug loading capacity, mucus embedment, and tuneable drug release. Here, MCs are loaded with the antibiotic ciprofloxacin (CIP), and sealed with a lid consisting of chitosan (CHI) and a mucolytic agent, N-acetylcysteine (NAC). It is found that CHI and NAC work synergistically, showing improved mucoadhesive and mucolytic properties. To better mimic the in vivo habitat of Pseudomonas aeruginosa (P. aeruginosa), the biofilm is grown in a mucin-containing medium on a newly developed centrifugal microfluidic system. The CHI/NAC coated MCs improve eradication of biofilm (88.22 ± 2.89%) compared to CHI-coated MCs (72.68 ± 3.73%) or bolus injection (39.86 ± 13.28%). The findings suggest that MCs are significantly more efficient than a bolus treatment. Furthermore, CHI/NAC functionalized MCs kill most of the biomass already after 5 h (80.75 ± 3.50%), mainly due to a fast drug release. This is the first time that CHI/NAC has been combined as a coating to explore mucolytic properties on bacterial biofilms.

A study of Rose Bengal against a 2-keto-3-deoxy-d-manno-octulosonate cytidylyltransferase as an antibiotic candidate

Frequent occurrences of multi-drug resistance of pathogenic Gram-negative bacteria threaten human beings. The CMP-2-keto-3-deoxy-d-manno-octulosonic acid biosynthesis pathway is one of the new targets for antibiotic design. 2-Keto-3-deoxy-d-manno-octulosonate cytidylyltransferase (KdsB) is the key enzyme in this pathway. KdsB proteins from Burkholderia pseudomallei (Bp), B. thailandensis (Bt), Pseudomonas aeruginosa (Pa), and Chlamydia psittaci (Cp) have been assayed to find inhibitors. Interestingly, Rose Bengal (4,5,6,7-tetrachloro-2′,4′,5′,7′-tetraiodofluorescein) was turned out to be an inhibitor of three KdsBs (BpKdsB, BtKdsB, and PaKdsB) with promising IC₅₀ values and increased thermostability. The inhibitory enzyme kinetics of Rose Bengal revealed that it is competitive with 2-keto-3-deoxy-manno-octulosonic acid (KDO) but non-competitive against cytidine 5′-triphosphate (CTP). Induced-fit docking analysis of PaKdsB revealed that Arg160 and Arg185 together with other interactions in the substrate binding site seemed to play an important role in binding with Rose Bengal. We suggest that Rose Bengal can be used as the scaffold to develop potential antibiotics.

Orbita-Infektion mit Delftia acidovorans nach Katzenkratzer

Anamnese und klinischer Befund Die 60-jährige Patientin wurde vor 34 Monaten von ihrer Katze am linken Augenlid gekratzt. Danach kam es zu chronischen, langsam progredienten Hautveränderungen mit sich verstärkenden Kopfschmerzen. Therapieversuche mit Kortison, Pimecrolimus, Pregabalin und Metamizol waren erfolglos. Nach 24 Monaten klagte sie über starken Bulbus-Schmerz am linken Auge, zunehmende Schmerzen bei Augenbewegungen und große Lichtempfindlichkeit. Es zeigten sich granulomatöse Papeln im Bereich des Auges.

Untersuchungen und Diagnose Die interdisziplinären Untersuchungsbefunde und klinisch-chemischen Parameter waren unauffällig. Eine Biopsie aus dem Lidbereich erbrachte den Nachweis von Delftia acidovorans mittels bakterieller 16S-rRNA-PCR.

Therapie und Verlauf Unter der Therapie mit Piperacillin/Tazobactam 3-mal 4,5 g/d i. v. für 10 Tage kam es zu einer raschen klinischen Besserung, sodass die Patientin nach 11 Tagen entlassen werden konnte. Nach weiteren 10 Monaten war sie rezidiv- und beschwerdefrei.

Folgerung D. acidovorans ist bislang nicht als zoonotischer Erreger in Erscheinung getreten, sollte aber bei Verletzungen durch Tiere in die differenzialdiagnostischen Erwägungen einbezogen werden.

Risk factors and antimicrobial resistance profiles of Pseudomonas putida infection in Central China, 2010-2017

The aim of this study was to analyze the risk factors, clinical features, and antimicrobial resistance of Pseudomonas putida (P putida) isolated from Tongji Hospital in Wuhan, China.The data of 44 patients with P putida infections were retrospectively reviewed in this study. All cases of P putida strains were detected by the clinical laboratory of Tongji Hospital in the period of January 2010 to December 2017. Antimicrobial susceptibility testing was conducted using Kirby-Bauer method.Forty-four effective strains of P putida were isolated, including 32 inpatients and 12 outpatients. The 32 inpatients cases were obtained from various departments, which were urosurgery wards (n = 5, 15.6%), pediatrics wards (n = 4, 12.5%), hepatic surgery wards (n = 4, 12.5%), among others. The isolates had been discovered from urine specimens (28.2%), blood specimens (21.9%), sputum specimens (12.5%), and so on. Twenty-five patients had histories of catheterization before the isolation of P putida. Twenty-four patients were in immunocompromised states, 5 patients had undergone surgery, catheterization and were taking immunosuppressive therapy simultaneously. Polymicrobial infections were found in some P putida cases, especially Stenotrophomonas maltophilia, Pseudomonas aeruginosa, and Escherichia coli. All the patients had treated by antimicrobial before culture. Multi-drug-resistant strains were detected in 75% of P putida isolates. The P putida strains were resistant to trimethoprim/sulfamethoxazole (97.7%), aztreonam (88.6%), minocyline (74.3%), ticarcillin/clavulanic acid (72.7%), and sensitive to amikacin (86.4%), imipenem (62.8%), gentamicin (56.8%).Catheterization or other invasive procedures, immunocompromised states, and underlying diseases increased the risks of P putida infections. Moreover, the P putida strains were highly resistant to trimethoprim/sulfamethoxazole, aztreonam, minocyline, ticarcillin/clavulanic acid.

Protective roles of ginseng against bacterial infection

Ginseng (Panax ginseng Meyer) is a well-known traditional herbal medicine that plays a protective role against microbial attack. Several studies have revealed its anti-cancer, anti-inflammatory, and immune-modulatory effects. Ginseng contains several components that vary according to the year of cultivation and the processing method used, such as heating, drying, and steaming, which induce different degrees of pharmacological activities. This review discusses the antibacterial effects of ginseng against pathogenic bacterial infections. We describe how ginseng regulates pathogenic factors that are harmful to the host and discuss the therapeutic potential of ginseng as a natural antibacterial drug to combat bacterial infectious disease, which is a global public health challenge. The components of ginseng could be novel alternatives to solve the growing problem of antibiotic resistance and toxicity.

Beta-Defensin 2 and 3 Promote Bacterial Clearance of Pseudomonas aeruginosa by Inhibiting Macrophage Autophagy through Downregulation of Early Growth Response Gene-1 and c-FOS

Beta-defensins 2 and 3 (BD2 and BD3) are inducible peptides present at the sites of infection, and they are well characterized for their antimicrobial activities and immune-regulatory functions. However, no study has thoroughly investigated their immunomodulatory effects on macrophage-mediated immune responses against Pseudomonas aeruginosa (PA). Here, we use THP-1 and RAW264.7 cell lines and demonstrate that BD2 and BD3 suppressed macrophage autophagy but enhanced the engulfment of PA and Zymosan bioparticles as well as the formation of phagolysosomes, using immunofluorescence staining and confocal microscopy. Plate count assay showed that macrophage-mediated phagocytosis and intracellular killing of PA were promoted by BD2 and BD3. Furthermore, microarray and real-time PCR showed that the expression of two genes, early growth response gene-1 (EGR1) and c-FOS, was attenuated by BD2 and BD3. Western blot revealed that BD2 and BD3 inhibited the expression and nuclear translocation of EGR1 and c-FOS. Knockdown of EGR1 and c-FOS by siRNA transfection suppressed macrophage autophagy before and after PA infection; while overexpression of these two transcription factors enhanced autophagy but reversed the role of BD2 and BD3 on macrophage-mediated PA eradication. Together, these results demonstrate a novel immune defense activity of BD2 and BD3, which promotes clearance of PA by inhibiting macrophage autophagy through downregulation of EGR1 and c-FOS.

Endotoxin evaluation of eleven lipopolysaccharides by whole blood assay does not always correlate with Limulus amebocyte lysate assay

More than 90% of all publications on endotoxin were carried out with endotoxins (lipopolysaccharide, LPS) from enterobacteriaceae. We compared the immune stimulatory potency of 11 different LPSs using human whole blood incubations. While the majority of LPSs induced cytokine release equipotently, a 1000-fold more LPS from Pseudomonas aeruginosa or Vibrio cholerae was still less potent in inducing TNF, IL-1β, IL-10 and IFN-γ though it potently induced nanogram quantities IL-8. All LPSs tested, regardless of the micro-organism, showed Toll-like receptor (TLR)4-dependence, except for the LPSs from P. aeruginosa and V. cholerae, which were both TLR4- and TLR2-dependent. Interestingly, UV-inactivated P. aeruginosa bacteria, although Gram-negative, also showed TLR2- and TLR4-dependence. Repurification of commercial LPS preparations by phenol re-extraction led to a complete loss of the TLR2 dependency, indicating contamination with lipoproteins. In the Limulus amebocyte lysate assay, often performed to exclude contamination in purified water likely to originate from P. aeruginosa, P. aeruginosa LPS was only 2-fold less potent than LPS from S. abortus equi or the assay standard LPS from E. coli. This results in an overestimation of pyrogenic burden by a factor of 500 in the sample when compared with the biological activity of highly purified P. aeruginosa LPS in human whole blood.

Delftia acidovorans: A rare pathogen in immunocompetent and immunocompromised patients

Delftia acidovorans is an aerobic, nonfermenting Gram-negative bacillus. It is usually a nonpathogenic environmental organism and is rarely clinically significant. Although D acidovorans infection most commonly occurs in hospitalized or immunocompromised patients, there are also several reports documenting the infection in immunocompetent patients. The present article describes a B cell lymphoblastic leukemia patient with D acidovorans pneumonia who was successfully treated with antibiotic therapy. The present report indicates that unusual pathogens may be clinically significant in both immunocompromised and immunocompetent patients. D acidovorans is often resistant to aminoglycosides; therefore, rapid detection of this microorganism is important.

Pseudomonas aeruginosa causing inflammatory mass of the nasopharynx in an immunocompromised HIV infected patient: A mimic of malignancy

Head and neck manifestations of acquired immunodeficiency syndrome are among the most common complications of this disease. The sinonasal and oral manifestations are more common that the otologic and range from malignancies to infectious processes caused by both opportunistic and nonopportunistic organisms. We report the case of a nasopharyngeal mass of infectious etiology in a severely immunocompromised HIV infected patient. The patient was admitted with a presumptive diagnosis of infectious gastroenteritis and was found to have a nasopharyngeal mass. The mass was extending into the oropharynx and paravertebral soft tissues and was associated with extensive secretions causing near complete occlusion of the oropharynx. CT scan findings favored malignant verses infectious etiology. The surgical biopsy performed twice ruled out malignancy and the bacterial culture proved to be a pure growth of Pseudomonas aeruginosa. Pseudomonas can inhabit the nasopharynx and lower digestive tract, and is only occasionally associated with causing disease in non-susceptible patients but is a common infection in immunocompromised patients. To the best of our knowledge, and after considering the current literature, we believe this case is unique. We discuss this rare entity and its management. Clinicians should be aware of this potential life threatening condition in the HIV population and add P. aeruginosa infection to the differential diagnosis of an acute inflammatory nasopharyngeal mass.

Polymicrobial Bacteremia Involving Comamonas testosteroni

Comamonas spp. are uncommon isolates in microbiology laboratories and have been rarely observed as an infectious agent in clinical practice. They have widespread environmental distribution and have been isolated from water, soil, and plants as well as from some hospital devices such as intravenous catheters and water contained in humidifier reservoirs used in respiratory treatment. The genus Comamonas originally contained the following species: acidovorans, testosteroni, kerstersii, terrigena, denitrificans, and nitrativorans. It now contains 17 species, while acidovorans spp. have been reclassified as Delftia acidovorans. In spite of its uncommon human pathogenesis, there are few reports on the aggressive manner of it as an opportunistic pathogen, mostly related to testosteroni spp. We present a case of polymicrobial bacteremia involving Comamonas testosteroni. The aim of this case report is to alert clinicians to the potential diagnosis of bloodstream infections caused by uncommon pathogens.

Description of Acidovorax wautersii sp. nov. to accommodate clinical isolates and an environmental isolate, most closely related to Acidovorax avenae

Three Gram-negative strains, NF 1078(T), NF 1598 and NF 1715, were isolated from clinical (two) and environmental (one) samples, respectively. Sequence analysis of the 16S rRNA genes revealed similarity of 100% among the three strains and next highest similarity to the type strain of Acidovorax avenae (98.16%). The three strains were able to acidify lactose and rhamnose on low peptone phenol red agar and to alkalinize citrate on Simmons' agar and were negative for nitrate reduction. The DNA G+C content of strain NF 1078(T) was 67.1 mol%. The level of DNA-DNA relatedness between this strain and the type strains of A. avenae (ATCC 19860(T), LMG 2117(T)) was 29%. Based on these phylogenetic, phenotypic and genotypic analyses, the three strains could be distinguished clearly from all other recognized Acidovorax species and should be classified as representatives of a novel species of the genus Acidovorax, for which the name Acidovorax wautersii sp. nov. is proposed. The type strain is NF 1078(T) (=LMG 26971(T)=CCUG 62584(T)).

The Fe(III) and Ga(III) coordination chemistry of 3-(1-hydroxymethylidene) and 3-(1-hydroxydecylidene)-5-(2-hydroxyethyl)pyrrolidine-2,4-dione: novel tetramic acid degradation products of homoserine lactone bacterial quorum sensing molecules

Bacteria use small diffusible molecules to exchange information in a process called quorum sensing (QS). An important class of quorum sensing molecules used by Gram-negative bacteria is the family of N-acylhomoserine lactones (HSL). It was recently discovered that a degradation product of the QS molecule 3-oxo-C(12)-homoserine lactone, the tetramic acid 3-(1-hydroxydecylidene)-5-(2-hydroxyethyl)pyrrolidine-2,4-dione, is a potent antibacterial agent, thus implying roles for QS outside of simply communication. Because these tetramic acids also appear to bind iron with appreciable affinity it was suggested that metal binding might contribute to their biological activity. Here, using a variety of spectroscopic tools, we describe the coordination chemistry of both the methylidene and decylidene tetramic acid derivatives with Fe(III) and Ga(III) and discuss the potential biological significance of such metal binding.

Recurrent intravascular-catheter-related bacteremia caused by Delftia acidovorans in a hemodialysis patient

We report the first case of recurrent intravascular-catheter-related bacteremia in a pediatric hemodialysis patient caused by Delftia acidovorans, previously called Comamonas acidovorans or Pseudomonas acidovorans. The patient had a history of multiple infections of central vascular catheters with other organisms, requiring courses of antibiotics and catheter replacements. Previously reported cases of D. acidovorans infections are reviewed. The isolate appeared to become resistant to cephalosporins after antibiotic treatment, but resistance could not be confirmed with additional testing. In vitro susceptibility testing for cephalosporins is not reliable for this organism.

Comamonas testosteroni infection in Taiwan: Reported two cases and literature review

Comamonas testosteroni is a widely distributed aerobic gram-negative bacillus. Infection by C testosteroni is infrequent, and no such cases have been reported in Taiwan. Here, we would like to present a 54-year-old alcoholic patient from Taiwan, and his left leg was injured during a fishing trip, resulting in left leg cellulitis and C testosteroni bacteremia. The patient's fever subsided after initial treatment with extended-spectrum cephalosporin, whereas his erythematous swelling did not resolve until switched to ciprofloxacin. The second patient is a 73-year-old Taiwanese male with chronic hepatitis B infection, liver cirrhosis, and hepatocellular carcinoma. Comamonas testosteroni bacteremia was found after transarterial embolization. Further studies are necessary to determine the best antibiotic(s) for patients infected with C testosteroni.

Pseudomonas aeruginosa and the host pulmonary immune response

Pseudomonas aeruginosa is a highly adaptable, opportunistic pathogen that is commonly found in the environment. It can infect a number of sites in the body and disseminate. It can cause both acute and chronic pulmonary infection and the acuity of infection and accompanying inflammatory phenotype is determined, for the most part, by the host. Although P. aeruginosa has been a successful opportunist in the context of a number of different disease states, it has been best studied in the context of cystic fibrosis (CF). The adaptability of P. aeruginosa has enabled it to adjust quickly to the CF airway, transitioning from initial colonization to chronic infection. The organism quickly expresses virulence factors that allow it to circumvent some elements of the host immune response and, even more importantly, quickly develops antimicrobial resistance. In the case of CF, chronic infection resulting in progressive lung damage, coupled with antimicrobial resistance, becomes an increasingly important issue as individuals with CF live longer. It is for these reasons that both organism- and host-targeted immunotherapies are being increasingly explored.

Implanted-port-catheter-related sepsis caused by Acidovorax avenae and methicillin-sensitive Staphylococcus aureus

Acidovorax avenae is a gram-negative rod in the family Comamonadaceae and a phytopathogen found in the environment. Human infections caused by members of the Comamonadaceae are extremely rare. We report a case of implanted-port-catheter-related sepsis caused by Acidovorax avenae and methicillin (meticillin)-sensitive Staphylococcus aureus (MSSA).

Pseudomonas exotoxin A: from virulence factor to anti-cancer agent

The pathogenic bacterium Pseudomonas aeruginosa has the ability to cause severe acute and chronic infections in humans. Pseudomonas exotoxin A (PE) is the most toxic virulence factor of this bacterium. It has ADP-ribosylation activity and decisively affects the protein synthesis of the host cells. The cytotoxic pathways of PE have been elucidated, and it could be shown that PE uses several molecular strategies developed under evolutionary pressure for effective killing. Interestingly, a medical benefit from this molecule has also been ascertained in recent years and several PE-based immunotoxins have been constructed and tested in preclinical and clinical trials against different cancers. In these molecules, the enzymatic active domain of PE is specifically targeted to tumor-related antigens. This review describes the current knowledge about the cytotoxic pathways of PE. Additionally, it summarizes preclinical and clinical trials of PE-based immunotoxins and furthermore discusses current problems and answers with these agents.

Therapeutic options for Stenotrophomonas maltophilia infections beyond co-trimoxazole: a systematic review

BACKGROUND

Stenotrophomonas maltophilia has emerged as an important opportunistic pathogen, causing infections whose management is often problematic due to its inherent resistance to many antibiotics, making co-trimoxazole the main therapeutic option. However, there are cases in which either due to antimicrobial resistance or allergic reactions and intolerance to co-trimoxazole this antibiotic cannot be administered. We sought to evaluate the available clinical evidence regarding potentially effective alternative antibiotics for the treatment of S. maltophilia infections.

METHODS

The literature search was performed in the PubMed and Scopus databases. The search string used was 'Stenotrophomonas maltophilia OR Xanthomonas maltophilia'.

RESULTS

Thirty-one case reports and 5 case series were retrieved including a total of 49 patients with a variety of infections. Twenty of 49 cases (40.8%) were treated with ciprofloxacin as monotherapy or in combination with other antibiotics; 12 of 49 cases (24.5%) were treated with ceftriaxone- or ceftazidime-based regimens; and 6 of 49 cases (12.2%) were treated with ticarcillin- or ticarcillin/clavulanate-based regimens. The cure or improvement rates were 18 cases (90%), 8 (75%) and 4 (66.7%), respectively. The remaining 11 patients received various antimicrobials including aminoglycoside-based regimens, carbapenems, levofloxacin, chloramphenicol, aztreonam, minocycline and other beta-lactams.

CONCLUSIONS

The limited available data suggest that ciprofloxacin, ceftazidime or ceftriaxone, and ticarcillin/clavulanate, alone or in combination with other antibiotics, may be considered as alternative options beyond co-trimoxazole.

Pseudomonas simiae sp. nov., isolated from clinical specimens from monkeys (Callithrix geoffroyi)

An unusual Gram-negative, catalase- and oxidase-positive, rod-shaped bacterium isolated from different clinical samples from two monkeys (Callithrix geoffroyi) was characterized by phenotypic and molecular genetic methods. The micro-organism was tentatively identified as a Pseudomonas species on the basis of the results of cellular morphological and biochemical tests. Fatty acid studies confirmed this generic placement and comparative 16S rRNA gene sequencing studies demonstrated that the unknown isolates were phylogenetically closely related to each other (100 % sequence similarity) and were part of the ‘Pseudomonas fluorescens intrageneric cluster’. The novel bacterium, however, was distinguished from other phylogenetically related species of Pseudomonas by DNA–DNA hybridization studies and biochemical tests. On the basis of both phenotypic and phylogenetic findings, it is proposed that the novel Pseudomonas isolates are classified as Pseudomonas simiae sp. nov. The type strain of P. simiae is OLiT (=CCUG 50988T=CECT 7078T).

Bacteremia due to Comamonas species possibly associated with exposure to tropical fish

Comamonas species are environmental gram-negative rods that grow forming pink-pigmented colonies. Despite their common occurrence in nature, they rarely cause human infection. We present a case of Comamonas bacteremia that we think may have been related to tropical fish exposure. The patient was treated successfully with levofloxacin.

Role of phosphoglucomutase of Stenotrophomonas maltophilia in lipopolysaccharide biosynthesis, virulence, and antibiotic resistance

A homologue of the algC gene, responsible for the production of a phosphoglucomutase (PGM) associated with LPS and alginate biosynthesis in Pseudomonas aeruginosa, spgM, was cloned from Stenotrophomonas maltophilia. The spgM gene was shown to encode a bifunctional enzyme with both PGM and phosphomannomutase activities. Mutants lacking spgM produced less LPS than the SpgM(+) parent strain and had a tendency for shorter O polysaccharide chains. No changes in LPS chemistry were obvious as a result of the loss of spgM. Significantly, however, spgM mutants displayed a modest increase in susceptibility to several antimicrobial agents and were completely avirulent in an animal model of infection. The latter finding may relate to the resultant serum sensitivity of spgM mutants which, unlike the wild-type parent strain, were rapidly killed by human serum. These data highlight the contribution made by LPS to the antimicrobial resistance and virulence of S. maltophilia.

Pseudomonas fluorescens encodes the Crohn's disease-associated I2 sequence and T-cell superantigen

Commensal bacteria have emerged as an important disease factor in human Crohn's disease (CD) and murine inflammatory bowel disease (IBD) models. We recently isolated I2, a novel gene segment of microbial origin that is associated with human CD and that encodes a T-cell superantigen. To identify the I2 microorganism, BLAST analysis was used to identify a microbial homologue, PA2885, a novel open reading frame (ORF) in the Pseudomonas aeruginosa genome. PCR and Southern analysis identified Pseudomonas fluorescens as the originating species of I2, with homologues detectable in 3 of 13 other Pseudomonas species. Genomic cloning disclosed a locus containing the full-length I2 gene (pfiT) and three other orthologous genes, including a homologue of the pbrA/pvdS iron response gene. CD4(+) T-cell responses to recombinant proteins were potent for I2 and pfiT, but modest for PA2885. pfiT has several features of a virulence factor: association with an iron-response locus, restricted species distribution, and T-cell superantigen bioactivity. These findings suggest roles for pfiT and P. fluorescens in the pathogenesis of Crohn's disease.

Central venous catheter-related infection due to Comamonas testosteroni in a woman with breast cancer

A 75-y-old woman with breast cancer presented with bacteremia due to Comamonas testosteroni. Evolution was favorable following adapted antimicrobial therapy and removal of a central venous catheter. This germ seems to be a rare pathogen; as reported in the literature, it is mostly encountered in patients with predisposing factors.

Hospital course of HIV-positive patients with odontogenic infections

OBJECTIVE

The study purpose was to compare and contrast the hospital course of patients who are human immunodeficiency virus-positive (HIV+) and human immunodeficiency virus-negative (HIV-) who were admitted to manage their odontogenic infection.

STUDY DESIGN

We used a retrospective case-control study design and a sample derived from patients admitted for management of their odontogenic infections. Cases and controls were defined as patients who were HIV+ or HIV-, respectively. HIV status was determined by patient self-report. Outcome variables included admission temperature (degrees Celsius) and white blood cell count, number of fascial spaces infected, days with temperature >38 degrees C, need for intensive care, and length of hospital stay.

RESULTS

The study sample consisted of 60 patients (10 HIV+ cases and 50 HIV- controls matched for age and sex) with a mean age of 32.8 +/- 6.6 years and was predominantly male (78%). Significant differences existed between patients who were HIV+ and those who were HIV- for the following variables: admission white blood cell count, number of days with maximum temperature >38.0 degrees C, and use of the intensive care unit.

CONCLUSIONS

The study results suggest that patients who are HIV+ who are admitted for management of odontogenic infection have a significantly more intense hospital course than those who are HIV-. However, the overall length of hospital stay is not significantly different.

Establishment of Pseudomonas aeruginosa infection: lessons from a versatile opportunist

Pseudomonas aeruginosa is an ubiquitous pathogen capable of infecting virtually all tissues. A large variety of virulence factors contribute to its importance in burn wounds, lung infection and eye infection. Prominent factors include pili, flagella, lipopolysaccharide, proteases, quorum sensing, exotoxin A and exoenzymes secreted by the type III secretion system.

Pseudomonas spp. complications in patients with HIV disease: an eight-year clinical and microbiological survey

Two hundred and twenty-four episodes of Pseudomonas spp. complications that occurred in 179 consecutive patients with HIV infection were retrospectively reviewed. Pseudomonas spp. organisms were responsible for 11.6% of 1933 episodes of non-mycobacterial bacterial diseases (5.4% of 1072 episodes of sepsis), observed over an 8-year period; 20.7% of patients experienced disease relapses (45 episodes). These complications mostly involved lower airways (66 cases), urinary tract (53 episodes), and blood (34 cases), with Pseudomonas aeruginosa isolated in 161 episodes, and other Pseudomonas spp. in the remaining 63 cases. An advanced HIV disease was frequently present (as expressed by a prior diagnosis of AIDS, a low CD4+ lymphocyte count, and leukopenia-neutropenia). Indwelling intravascular and urinary catheters were often associated with bacteremia and urinary tract involvement, respectively. More than 60% of patients were given antibiotics and/or cotrimoxazole in the month preceding the onset of Pseudomonas spp. disease. Bacterial strains isolated from our HIV-infected patients showed a favorable sensitivity to piperacillin, ceftazidime, imipenem, amikacin, tobramycin, and ciprofloxacin. An adequate antimicrobial treatment led to clinical and microbiological cure in 73.2% of patients at the first episode, and in 22.3% more subjects after one or more relapses. A lethal outcome occurred in only eight patients of 179 (4.5%), suffering from a far advanced HIV disease; P. aeruginosa infection directly contributed to death in four cases (sepsis, and/or pneumonia). Nosocomial disease occurred in 46.4% of the 224 episodes, and was significantly related to a previous diagnosis of AIDS, concurrent neutropenia, the occurrence of sepsis or urinary tract infection, disease relapses, the involvement of non-aeruginosa Pseudomonas spp., and a lethal outcome, compared with community-acquired infection. Our experience (the largest reported to date) confirms that Pseudomonas spp. (including non-aeruginosa Pseudomonas spp. organisms) is responsible for remarkable morbidity and mortality among patients with HIV infection, and may pose relevant problems to clinicians and microbiologists involved in the care of HIV-infected patients.

Nosocomial infections in patients with HIV disease

Throughout the AIDS epidemic, nosocomial infection in the patient with HIV disease has presented a constant problem--not only for the hospitalized patient but also for the clinic attender. The nosocomial spread of multidrug-resistant tuberculosis has emphasized the need for effective control of infection measures in dealing with the immunodeficient. Increased recognition of nosocomial bacterial pneumonias has raised questions about the place, if any, of antimicrobial prophylaxis in preventing Gram-negative and Legionella infection. The use of long-term indwelling venous catheters for the administration of parenteral therapy is associated with an increased risk of nosocomial bloodstream infection--particularly from staphylococci and Pseudomonas spp. Evidence now exists for the nosocomial spread of opportunistic infections, including Cryptosporidium parvum, Mycobacterium avium complex and Pneumocystis carinii. The delay between exposure and diagnosis, the atypical presentation of infections such as tuberculosis and repeated hospital admissions of AIDS patients can combine to confuse the issue with the result that a nosocomial infection may be mis-classified as community-acquired. It seems likely that the burden of nosocomial infection in HIV disease is continually underestimated.

Comamonas acidovorans contamination of dental unit waters

A study was carried out to evaluate the extent of the colonization of dental water systems by Comamonas acidovorans and to investigate how the occurrence of these bacteria is related to certain water characteristics. The 152 water samples were collected from the oral rinsing cup, air-water syringe, turbine and supply lines to dental units. Comamonas acidovorans was found most frequently and in greatest quantities in samples taken from water entering the units and in samples with a lower total bacterial count at 22 degrees C, higher temperature, lower content of organic matter and, in general, higher concentrations of residual chlorine.

Pseudomonas aeruginosa infection in human immunodeficiency virus infected patients

OBJECTIVES

(1) To determine the incidence and outcome of Pseudomonas aeruginosa infection in HIV-infected patients. (2) To study the antimicrobial susceptibility of P. aeruginosa isolates in this particular population. (3) To identify risk factors for these infections.

PATIENTS AND METHODS

A retrospective case-control study performed in a 28-bed infectious-diseases unit in a 940-bed university hospital. All cases were defined as HIV-infected patients with severe infections due to P. aeruginosa, including bacteremia, lower or upper respiratory tract infections, infections related to a central venous catheter, and cutaneous/muscular infection. Each case was matched with an HIV-seropositive control not infected by P. aeruginosa and hospitalized on the same dates as the cases.

RESULTS

One thousand and thirty-five HIV-infected patients were hospitalized during the study period. A first severe P. aeruginosa infection was documented in 41 patients, giving an overall annual incidence note of 2.51 episodes per 100 admissions. Forty of the 41 case notes were available for analysis. They consisted of 17 cases of bacteraemia, four upper respiratory tract infections, 10 lower respiratory tract infections, three catheter-related infections, and six cutaneous/muscular infections. Of these 40 cases, 60% were nosocomial and the remainder were community-acquired. The overall mortality rate was 22% (47% in bacteraemic forms). Twenty five percent of patients relapsed after an average of 37 days. The case-control comparison showed that AIDS was more frequent among the cases (92% vs. 74%, P = 0.04), who also had a lower PN count (P = 0.005), and a lower CD4 cell count (15.7 +/- 18.8/mm3 vs. 118 +/- 211/mm3; P = 0.0007). The number of days spent in hospital in the previous 3 months (29.3 +/- 20.7 vs. 19.7 +/- 14, P = 0.04) was significantly higher among the cases. In a multivariate analysis, examining treatments received in the previous month, only co-trimoxazole [OR = 5.5 (1.1-26.9)], penicillins [OR = 5.2 (1.1-25.3)], steroids [OR = 5.5, (1.2-25.5)] and a CD4 cell count below 50/mm3 [OR = 13.2 (1.4-129.4)] were identified as risk factors.

CONCLUSION

P. aeruginosa infection is a not frequent bacterial disease in highly immunodeficient HIV-infected patients. It is frequently fatal and must be borne in mind in the advanced stages of HIV disease, especially when patients have received co-trimoxazole (trianthoprim-sulphamethoxazole), penicillins or steroids.

Microbiological and clinical aspects of infection associated with Stenotrophomonas maltophilia

The gram-negative bacterium Stenotrophomonas maltophilia is increasingly recognized as an important cause of nosocomial infection. Infection occurs principally, but not exclusively, in debilitated and immunosuppressed individuals. Management of S. maltophilia-associated infection is problematic because many strains of the bacterium manifest resistance to multiple antibiotics. These difficulties are compounded by methodological problems in in vitro susceptibility testing for which there are, as yet, no formal guidelines. Despite its acknowledged importance as a nosocomial pathogen, little is known of the epidemiology of S. maltophilia, and although it is considered an environmental bacterium, its sources and reservoirs are often not readily apparent. Molecular typing systems may contribute to our knowledge of the epidemiology of S. maltophilia infection, thus allowing the development of strategies to interrupt the transmission of the bacterium in the hospital setting. Even less is known of pathogenic mechanisms and putative virulence factors involved in the natural history of S. maltophilia infection and this, coupled with difficulties in distinguishing colonization from true infection, has fostered the view that the bacterium is essentially nonpathogenic. This article aims to review the current taxonomic status of S. maltophilia, and it discusses the laboratory identification of the bacterium. The epidemiology of the organism is considered with particular reference to nosocomial outbreaks, several of which have been investigated by molecular typing techniques. Risk factors for acquisition of the bacterium are also reviewed, and the ever-expanding spectrum of clinical syndromes associated with S. maltophilia is surveyed. Antimicrobial resistance mechanisms, pitfalls in in vitro susceptibility testing, and therapy of S. maltophilia infections are also discussed.

Bacterial infections

Non-opportunistic bacterial infections are an important cause of morbidity and mortality for HIV-infected adults and children. Factors associated with increased risk of these include altered B- and T-cell function; altered phagocytic cell function; skin and mucous membrane defects; and use of indwelling vascular catheters, antibiotics, or cytotoxic agents. The pathogens encountered most frequently are S. aureus, S. pneumoniae, H. influenzae, Salmonella sp., and Pseudomonas aeruginosa. Less commonly encountered organisms include Rhodococcus equi, Listeria monocytogenes, Shigella sp., and Nocardia asteroides, Strategies for prevention as well as diagnosis and treatment of these are discussed.

Pseudomonas aeruginosa bronchopulmonary infection in patients with advanced human immunodeficiency virus disease

Pseudomonas aeruginosa is increasingly reported as a respiratory pathogen in patients with advanced human immunodeficiency virus (HIV) disease. We retrospectively reviewed the chest radiographic appearances of 29 HIV-infected adults with bronchopulmonary infection in whom Pseudomonas aeruginosa was the sole respiratory pathogen isolated. The commonest radiographic abnormality was a diffuse reticular (11 patients) or reticulonodular (9 patients) infiltrate in the pulmonary interstitium. Alveolar opacification was seen in seven patients. Cavitation was rare (2 patients), as was ground-glass opacification (2 patients). Five patients had pleural effusions. No patient had mediastinal or hilar lymphadenopathy. Normal chest radiographs were seen in eight patients. Although the radiographic appearances of Pseudomonas bronchopulmonary infection in HIV-infected patients are non-specific, an interstitial infiltrate is a common finding. Pseudomonas aeruginosa should be considered along with the commoner pathogen Pneumocystis carinii in the differential diagnosis of an interstitial infiltrate in this group of patients.