Immune checkpoint inhibitor-induced neurotoxicity is not associated with seroprevalence of neurotropic infections.

BACKGROUND: Immune checkpoint inhibitors (ICI) substantially improve outcome for patients with cancer. However, the majority of patients develops immune-related adverse events (irAEs), which can be persistent and significantly reduce quality of life. Neurological irAEs occur in 1-5% of patients and can induce severe, permanent sequelae or even be fatal. In order to improve the diagnosis and treatment of neurological irAEs and to better understand their pathogenesis, we assessed whether previous neurotropic infections are associated with neurological irAEs. METHODS: Neurotropic infections that might predispose to ICI-induced neurological irAEs were analyzed in 61 melanoma patients from 3 countries, the Netherlands, Australia and Germany, including 24 patients with neurotoxicity and 37 control patients. In total, 14 viral, 6 bacterial, and 1 protozoal infections previously reported to trigger neurological pathologies were assessed using routine serology testing. The Dutch and Australian cohorts (NL) included pre-treatment plasma samples of patients treated with neoadjuvant ICI therapy (OpACIN-neo and PRADO trials; NCT02977052). In the Dutch/Australian cohort a total of 11 patients with neurological irAEs were compared to 27 control patients (patients without neurological irAEs). The German cohort (LMU) consisted of serum samples of 13 patients with neurological irAE and 10 control patients without any documented irAE under ICI therapy. RESULTS: The association of neurological irAEs with 21 possible preceding infections was assessed by measuring specific antibodies against investigated agents. The seroprevalence of all the tested viral (cytomegalovirus, Epstein-Barr-Virus, varicella-zoster virus, measles, rubella, influenza A and B, human herpes virus 6 and 7, herpes simplex virus 1 and 2, parvovirus B19, hepatitis A and E and human T-lymphotropic virus type 1 and 2), bacterial (Borrelia burgdorferi sensu lato, Campylobacter jejuni, Mycoplasma pneumoniae, Coxiella burnetti, Helicobacter pylori, Yersinia enterocolitica and Y. pseudotuberculosis) and protozoal (Toxoplasma gondii) infections was similar for patients who developed neurological irAEs as compared to control patients. Thus, the analysis provided no evidence for an association of described agents tested for seroprevalence with ICI induced neurotoxicity. CONCLUSION: Previous viral, bacterial and protozoal neurotropic infections appear not to be associated with the development of neurological irAEs in melanoma patients who underwent therapy with ICI across 3 countries. Further efforts are needed to unravel the factors underlying neurological irAEs in order to identify risk factors for these toxicities, especially with the increasing use of ICI in earlier stage disease.

Is benzyl alcohol a significant contact sensitizer?

BACKGROUND: Benzyl alcohol is a widely used preservative, solvent and fragrance material. According to published data, it is a rare sensitizer in humans. OBJECTIVES: To identify characteristics and sensitization patterns of patients with positive patch test reactions to benzyl alcohol and to check the reliability of the patch test preparation benzyl alcohol 1% pet. PATIENTS AND METHODS: Retrospective analysis of data from the Information Network of Departments of Dermatology (IVDK), 2010-2019. RESULTS: Of 70 867 patients patch tested with benzyl alcohol 1% pet., 146 (0.21%) showed a positive reaction, most of them (89%) only weakly positive. The number of doubtful and irritant reactions significantly exceeded the number of positive reactions. Reproducibility of positive test reactions was low. Among benzyl alcohol-positive patients, compared to benzyl alcohol-negative patients, there were significantly more patients with leg dermatitis (17.8% vs. 8.6%), more patients aged 40 years or more (81.5% vs. 70.5%) and more patients who were tested because of a suspected intolerance reaction to topical medications (34.9% vs. 16.6%). Concomitant positive reactions were mainly seen to fragrances, preservatives and ointment bases. CONCLUSIONS: Sensitization to benzyl alcohol occurs very rarely, mainly in patients with stasis dermatitis. In view of our results, benzyl alcohol cannot be regarded as a significant contact allergen, and therefore marking it as skin sensitizer 1B and labelling it with H 317 is not helpful.

Short- and Long-term Outcome After Interventional VSD Closure: A Single-Center Experience in Pediatric and Adult Patients.

Interventional closure of congenital ventricular septal defects (VSD) is recording a continuous rise in acceptance. Complete atrioventricular block (cAVB) and residual shunting are major concerns during follow-up, but long-term data for both are still limited. We retrospectively evaluated the outcome of patients with interventional VSD closure and focused on long-term results (> 1 year follow-up). Transcatheter VSD closures were performed between 1993 and 2015, in 149 patients requiring 155 procedures (104 perimembranous, 29 muscular, 19 residual post-surgical VSDs, and 3 with multiple defects). The following devices were used: 65 × Amplatzer™ Membranous VSD Occluder, 33 × Duct Occluder II, 27 × Muscular VSD Occluder, 3 × Duct Occluder I, 24 × PFM-Nit-Occlud®, and 3 × Rashkind-Occluder. The median age at time of implantation was 6.2 (0.01-66.1) years, median height 117 (49-188) cm, and median weight 20.9 (3.2-117) kg. Median follow-up time was 6.2 (1.1-21.3) years and closure rate was 86.2% at last follow-up. Complications resulting in device explantation include one case of cAVB with a Membranous VSD occluder 7 days after implantation and four cases due to residual shunt/malposition. Six (4%) deaths occurred during follow-up with only one procedural related death from a hybrid VSD closure. Overall, our reported results of interventional VSD closure show favorable outcomes with only one (0.7%) episode of cAVB. Interventional closure offers a good alternative to surgical closure and shows improved performance by using softer devices. However, prospective long-term data in the current era with different devices are still mandatory to assess the effectiveness and safety of this procedure.

Assessment of occupational exposure and spectrum of contact sensitization in metalworkers with occupational dermatitis: results of a cohort study within the OCCUDERM project.

BACKGROUND: Metalworkers occupationally exposed to metals, tools, metalworking fluids (MWFs), technical oils, gloves, skin care products etc. frequently suffer from occupational dermatitis (OD). OBJECTIVES: To investigate occupational exposure and to identify relevant occupational sensitizers in metalworkers with OD, and to evaluate suitability of current German patch test recommendations for this occupational group. PATIENTS AND METHODS: As part of the OCCUDERM project, occupational exposure of 230 metalworkers with suspected OD patch tested in the departments of dermatology in Göttingen and Osnabrück (both Lower Saxony, Germany) in 2012-2017 was recorded by questionnaire. These data, as well as results, of patch testing with standardized allergens and with workplace material were analysed. RESULTS: Metalworking fluids and skin care products were the most important exposures. Among MWF allergens, most frequently sensitizations to formaldehyde and formaldehyde releasers, colophony/abietic acid and monoethanolamine were observed. Sensitization to methylisothiazolinone (MI) was frequent, probably as part of the general European epidemic of contact allergy to MI in leave-on cosmetics. Sensitization to glove ingredients only played a minor role. CONCLUSIONS: The known occupational allergen spectrum could largely be confirmed. In order not to miss relevant sensitizations, patch testing with material from the patients' workplaces in parallel to baseline and MWF series is recommended. Sensitizations diagnosed could not always be linked to particular occupational exposures.

The frequency of specific contact allergies is reduced in patients with psoriasis.

BACKGROUND: Earlier studies suggested an inverse association between contact allergy and psoriasis, although the results of clinical studies have been inconsistent. Gene expression studies in human contact allergy focusing on immune responses revealed nickel being an inducer of T helper (Th)1/Th17 and some Th22 immune polarization, whereas fragrances were found to promote a Th2-dominated immune activation. OBJECTIVES: To investigate the epidemiological association between contact allergy and psoriasis in a large multicentre cohort and to analyse the sensitization profile to specific allergens in these patients. METHODS: Retrospective analysis of patch-tested patients from 56 departments of dermatology (1996-2015), including 2387 patients with psoriasis and 161 989 control patients. All patients with atopic dermatitis were excluded from both groups. RESULTS: The odds ratio (OR) for contact allergy was calculated to be 0·55 in patients with psoriasis (95% confidence interval 0·50-0·59). Logistic regression analyses with several independent variables indicated a 'protective effect' of having psoriasis for most allergens, independently of age, sex, affected body site and patch test indication. Fragrance mix II (OR 0·36) and lanolin alcohols (OR 0·38) were found to be among the least common allergens in patients with psoriasis. In contrast, the frequency of contact dermatitis to nickel was only marginally affected in patients with psoriasis compared with controls (OR 0·75). CONCLUSIONS: The inverse association between psoriasis and allergic contact sensitization is likely to be not exclusively mediated by psoriasis itself. The polarization of the activated immune response by specific allergens may influence the occurrence and significance of contact allergies in underlying immune-mediated diseases, eventually even beyond the skin.

Effects of mesenchymal stromal cells versus serum on tendon healing in a controlled experimental trial in an equine model.

BACKGROUND: Mesenchymal stromal cells (MSC) have shown promising results in the treatment of tendinopathy in equine medicine, making this therapeutic approach seem favorable for translation to human medicine. Having demonstrated that MSC engraft within the tendon lesions after local injection in an equine model, we hypothesized that they would improve tendon healing superior to serum injection alone. METHODS: Quadrilateral tendon lesions were induced in six horses by mechanical tissue disruption combined with collagenase application 3 weeks before treatment. Adipose-derived MSC suspended in serum or serum alone were then injected intralesionally. Clinical examinations, ultrasound and magnetic resonance imaging were performed over 24 weeks. Tendon biopsies for histological assessment were taken from the hindlimbs 3 weeks after treatment. Horses were sacrificed after 24 weeks and forelimb tendons were subjected to macroscopic and histological examination as well as analysis of musculoskeletal marker expression. RESULTS: Tendons injected with MSC showed a transient increase in inflammation and lesion size, as indicated by clinical and imaging parameters between week 3 and 6 (p < 0.05). Thereafter, symptoms decreased in both groups and, except that in MSC-treated tendons, mean lesion signal intensity as seen in T2w magnetic resonance imaging and cellularity as seen in the histology (p < 0.05) were lower, no major differences could be found at week 24. CONCLUSIONS: These data suggest that MSC have influenced the inflammatory reaction in a way not described in tendinopathy studies before. However, at the endpoint of the current study, 24 weeks after treatment, no distinct improvement was observed in MSC-treated tendons compared to the serum-injected controls. Future studies are necessary to elucidate whether and under which conditions MSC are beneficial for tendon healing before translation into human medicine.

[Type IV contact allergies in the food processing industry: an update]. / Typ-IV-Kontaktallergien in Nahrungsmittelberufen: Eine aktuelle Übersicht.

BACKGROUND: The food sector is one of the high-risk areas for occupational irritative and allergic contact eczema. OBJECTIVES: The present work provides an overview of the main allergens as well as sensitization frequencies and risk in various food industry occupations. METHODS: The literature on type IV sensitization in the food sector is summarized. RESULTS: The relative risk of developing a work-related eczema in food processing is increased by more than 3 times. The comparison group was calculated on the basis of the proportion of documented cases in the IVDK (Informationsverbund Dermatologischer Kliniken) network per 100,000 working persons in relation to the average of the years 2005 and 2010. For this purpose, the average risk of all patients was set as reference to 1. Bakers, pastry chefs, cooks and meat and fish processors are mainly affected. In addition to irritant contact eczema, allergic contact eczema and protein contact dermatitis often occur. Leading haptens (main allergens) are rubber ingredients, but also disinfectants and compositae. CONCLUSION: Only a few contact allergens are responsible for the majority of job-relevant sensitizations in the food industry.

Pharmacodynamics of Finafloxacin, Ciprofloxacin, and Levofloxacin in Serum and Urine against TEM- and SHV-Type Extended-Spectrum-ß-Lactamase-Producing Enterobacteriaceae Isolates from Patients with Urinary Tract Infections.

The pharmacodynamics of finafloxacin, ciprofloxacin, and levofloxacin against extended-spectrum-ß-lactamase (ESBL)-producing Enterobacteriaceae isolates were compared. Since quinolones lose activity in acidic media, and particularly in urine, their activities were tested in parallel under conventional conditions and in acidic artificial urine. For this purpose, TEM- and SHV-type ESBL-producing Escherichia coli and Klebsiella pneumoniae strains and their wild-type counterparts were exposed in a modified Grasso model to simulated concentrations of drugs in serum and urine following oral doses of either finafloxacin at 800 mg once a day (q.d.), immediate-release ciprofloxacin at 500 mg twice a day (b.i.d.), extended-release ciprofloxacin at 1,000 mg q.d., or levofloxacin at 500 or 750 mg q.d. The concentrations of the drugs in urine were fitted by compartmental modeling. Bacteria were cultivated in Mueller-Hinton broth (MHB) at pH 7.2 or 5.8 or in artificial urine at pH 5.8. Bacteria were counted every 2 h until 10 h and at 24 h; the areas under the bacterial-count-versus-time curves were calculated. It was found that finafloxacin eliminated all strains within 2 h under all the conditions studied. At all doses studied, ciprofloxacin and levofloxacin were highly active against wild-type strains in MHB at pH 7.2 but lost activity in MHB, and particularly in urine, at pH 5.8. Viable counts of ESBL producers were reduced for 6 to 8 h by 3 log10 titers, but the bacteria regrew thereafter. Ciprofloxacin and levofloxacin were almost inactive against the SHV producer grown in artificial urine. We conclude that pharmacodynamic models using artificial urine may mirror the physiology of urinary tract infections more closely than those using conventional media. In contrast to ciprofloxacin and levofloxacin, finafloxacin gained activity in this model at an acidic pH, maintained activity in artificial urine, and was active against TEM and SHV producers.

Occupational contact sensitization in female geriatric nurses: Data of the Information Network of Departments of Dermatology (IVDK) 2005-2014.

BACKGROUND: Geriatric nurses (GN) have a high risk of occupational contact dermatitis (OCD), with chronic irritant contact dermatitis predominating. However, allergic contact dermatitis is an important issue as well. Little is known whether the relevant occupational allergen spectrum reported in the 1990s, including fragrances, preservatives, rubber chemicals and ingredients of surface disinfectants to be the most common sensitizers in GN, is still valid. OBJECTIVES: To monitor the current allergen spectrum in GN with OCD and verify the validity of the patch test recommendations (baseline-, preservative-, ointment base-, rubber-, disinfectant, series and fragrances) in GN with suspected OCD given by the German Contact Dermatitis Research Group (DKG). METHODS: Retrospective analysis of IVDK data (2005-2014) of 743 female GN with OCD, in comparison to 695 GN without OCD. RESULTS: GN with OCD reacted significantly more frequently to both fragrance mixes, hydroxyisohexyl 3-cyclohexene carboxaldehyde (HICC), thiuram mix, zinc diethyldithiocarbamate and mercaptobenzothiazole than GN without OCD. Reactions to MDBGN, methylchloroisothiazolinone/methylisothiazolinone and oil of turpentine occurred substantially, but not significantly more frequently among GN with OCD. The latter may be due to former use of a special alcoholic liniment in geriatric care. Among material from the patients' workplaces, tetrazepam was a frequent allergen, due to dust exposure from pill crushing. Furthermore, occupationally used protective gloves, body care products as well as surface disinfectants were often tested positively. CONCLUSIONS: The general allergen spectrum in GN with OCD is unchanged, so the DKG patch test recommendations are still valid. Prevention of occupational sensitization should focus on fragrance-free hygiene and body care products, usage of accelerator-free protective gloves and avoidance of drug dust exposure.

[Spondylodiscitis in children and adolescents]. / Spondylodiszitis im Kindes- und Jugendalter.

BACKGROUND: Spondylodiscitis in children is rare. The condition has an incidence of 2 to 4 % of all infectious skeletal diseases in children. AIM: Aim of the article is the presentation of epidemiology, the clinical signs, radiological findings as well the treatment options of non-specific and specific spondylodiscitis in children. METHODS: The available literature was reviewed. RESULTS: Non-specific spondylodiscitis in children is caused by haematogenous spread of pathogens. Staphylococcus aureus is the most frequently detected bacterium. The clinical signs are unspecific and an Magnetic Resonance Imaging of the spine is the standard radiological procedure to detect spondylodiscitis. In general, the treatment is conservative and includes an antibiotic therapy as well an immobilization of the spine. In endemic areas of the world, specific spondylodiscitis is more common and is caused by Mycobacterium tuberculosis or Brucellae. The treatment is also conservative. For all entities of spondylodiscitis in children, a surgical intervention is only necessary in the case of severe deformities due to the infection or in the case of neurological symptoms. CONCLUSION: Elevated infectious laboratory values and back pain or other unspecific symptoms can indicate spondylodiscitis in children. MRI of the spine is necessary to rule out spondylodiscitis.

Bordetella trematum in chronic ulcers: report on two cases and review of the literature.

We report on two new cases Bordetella trematum in chronic ulcers. Literature shows that this species is infrequently isolated from clinical samples. Only a few cases have been reported so far. B. trematum may be underdiagnosed because of its problematic identification. Today, MALDI-TOF MS allows for an accurate discrimination of these bacteria. Overall, B. trematum was typically associated with severe skin and soft tissue infections, particularly in diabetic patients. The intrinsic resistance to some antibiotics commonly used to treat these infections makes the isolation of B. trematum significant.

A novel mutation in the XPA gene results in two truncated protein variants and leads to a severe XP/neurological symptoms phenotype.

BACKGROUND: The nucleotide excision repair (NER) pathway repairs UV-induced DNA lesions in an accurate fashion and prevents UV-irradiated areas of the skin from tumour formation. The XPA protein plays a major role in DNA damage demarcation as well as stabilization of other NER factors and was found to be defective in xeroderma pigmentosum (XP) complementation group A patients. OBJECTIVE: Characterization of four new XP-A patients. METHODS: Genomic and cDNA sequencing, post-UV cell survival of living cells, host-cell reactivation of patients' fibroblasts and Western blotting. RESULTS: One of the four investigated patients shows a novel mutation leading to two different truncated protein variants. Three patients contain the already described p.R228X mutation. All patient cell lines exhibit a strong UVC sensitivity and reduced NER capability. In most of the cases stable protein expression was detected. CONCLUSION: We discovered four new XP-A patients and a novel XPA mutation resulting in two diverse patient alleles.

Follow-up of patients with interventional closure of ventricular septal defects with Amplatzer Duct Occluder II.

Nonsurgical closure of congenital ventricular septal defects (VSD) has become increasingly acceptable with the availability of different occlusion systems. Transcatheter device treatment is used for perimembranous and muscular defects. Atrio-ventricular block remains the most troublesome complication of device closure. The aim of this study was to describe our experience with closure of VSD using the Amplatzer Duct Occluder II (ADO II) as an "off-label" approach in children and adults. Between 2004 and 2012 transcatheter closure of 31 VSD (20 perimembranous, 10 muscular VSD and 1 ruptured sinus valsalva) with ADO II was undertaken in patients between 3 months and 55 years of age and with a body weight ranging from 4 to 105 kg in our institution. In 29 of 31 procedures, the defect was successfully closed (93.5%) without any significant complications. No increase of aortic or tricuspid valve regurgitation was found in any after procedure. Small residual shunts were observed immediately after the device implantation, but disappeared during a median follow-up period of 38 months (0.4-63) in 27 of 31 patients. There was no incidence of AV block or other conductance abnormalities during implantation or follow-up. The ADO II device is safe and effective for transcatheter VSD closure, but this is still an "off-label" use. After long-term follow-up in a large number of patients this device may be approved for VSD closure in the future.

Rapid detection of antibiotic resistance based on mass spectrometry and stable isotopes.

With the emergence and growing complexity of bacterial drug resistance, rapid and reliable susceptibility testing has become a topical issue. Therefore, new technologies that assist in predicting the effectiveness of empiric antibiotic therapy are of great interest. Although the use of matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS) for the rapid detection of antibiotic resistance is an attractive option, the current methods for MALDI-TOF MS susceptibility testing are restricted to very limited conditions. Here, we describe a technique that may allow for rapid susceptibility testing to an extent that is comparable to phenotypic methods. The test was based on a stable isotope labelling by amino acids in cell culture (SILAC)-like approach. This technique was used to visualise the growth of bacteria in the presence of an antibiotic. Pseudomonas aeruginosa was chosen as the model organism, and strains were incubated in normal medium, medium supplemented with (13)C6-(15) N2-labelled lysine and medium supplemented with labelled lysine and antibiotic. Peak shifts occurring due to the incorporation of the labelled amino acids were detected by MALDI-TOF MS. Three antibiotics with different mechanisms of action, meropenem, tobramycin and ciprofloxacin, were tested. A semi-automated algorithm was created to enable rapid and unbiased data evaluation. With the proposed test, a clear distinction between resistant and susceptible isolates was possible for all three antibiotics. The application of SILAC technology for the detection of antibiotic resistance may contribute to accelerated and reliable susceptibility testing.

Invasive cardiac aspergillosis after orthotopic liver transplantation.

Invasive aspergillus infection occurs in 5 - 42 % of liver-transplanted recipients and is a dangerous complication, associated with high mortality if untreated. However, the early diagnosis of invasive aspergillosis can be elusive, as clinical signs are unspecific and the pathogenic agent is difficult to demonstrate. We here report about a 58-year-old man with acute liver failure caused by newly diagnosed chronic hepatitis B infection who underwent liver transplantation. The postoperative course was uneventful, and the patient was discharged after 30 days. After 105 days the patient was readmitted because of fever, recurrent chest and abdominal pain. Computed tomography revealed a cardiac lesion; other diagnostic steps including bone-marrow and endomycordial biopsy, virological and microbiological investigations gave no clear findings. To exclude a malignant process, thoracotomy with mass and simultaneous lower left lobe resection were performed. Histopathological findings revealed an invasive perimyocardial aspergillosis. Immediate intravenous therapy with voriconazole and caspofungin was initiated and monitoring of the mass was performed with transesophageal echocardiography and Cardio-MRI. Due to slightly increase of the lesion, medication was switched to posaconazole and caspofungin. Under this dual fungal treatment the lesion regressed and the patient could be discharged after two months in good clinical condition. Frequent Cardio-MRI scan after discharge showed further mass-regression. Therefore antifungal treatment was switched to oral posaconazole mono-therapy. After one year, complete reduction of the mass was achieved and antifungal therapy was discontinued. Recent diagnostic imaging follow-up showed no pathological finding.

A novel ex vivo set-up for dynamic long-term characterization of processes on mucosal interfaces by confocal imaging and simultaneous cytokine measurements.

We present a novel organ-explant imaging system for easy and cost-effective extended-time observation of host-pathogen interactions at mucosal interfaces. Data are complemented by parallel cytokine measurements at high temporal resolution. The set-up is based on a custom-built reusable organ chamber compatible with standard microscopes. Luminal and basal side of the explanted mucosa are connected to separate channels for optimized incubation and cytokine measurements, oxygen is provided via membrane oxygenation. Dynamic imaging with confocal microscopy permits a detailed analysis of the dynamics of pathogen-host cell interactions at the mucosal interface and the neighbouring tissue at high resolution. The system can be applied to various hollow organs with few modifications. Here we present first applications to study representative infections such as uropathogenic Escherichia coli (UPEC) infections in the urinary bladder or amoebiasis of the colon by using mouse organs. We show (i) intracellular bacteria in UPEC infections, (ii) phagocytic events on tissue during infection, as well as (iii) tissue invasion of virulent protozoans into epithelia. The versatility of this system and its higher degree of control in comparison with both traditional explant microscopy and in vivo two photon imaging solutions make it a valuable and easy-to-use addition to other current imaging techniques.

Volatile organic compound analysis by ion molecule reaction mass spectrometry for Gram-positive bacteria differentiation.

Approximately 50 % of all clinically proven infections in critically ill patients are caused by Gram-positive bacteria. The timely and appropriate treatment of these infections is vital in order to avoid negative outcomes. Hence, fast and reliable methods are needed for the early detection and identification of microorganisms. Recently, direct mass spectrometry-based analysis of volatile organic compounds emitted by microorganisms has been employed to study Gram-negative bacteria. Here, we report a feasibility study of ion molecule reaction mass spectrometry (IMR-MS) for in vitro growth detection and species differentiation of selected Gram-positive bacteria that are frequently isolated in blood culture samples, namely, Enterococcus faecalis, Enterococcus faecium, Staphylococcus aureus, and Staphylococcus epidermidis. Ion molecule reaction mass spectrometry was used to analyze the headspace above cultures containing Gram-positive bacteria incubated at 37 °C starting with 10(2) colony-forming units (CFU)/ml. Measurements to determine the presence of volatile organic compounds were performed 4, 8, and 24 h after incubation, respectively. The detection of microbial growth was accomplished already after 8 h in cultures containing E. faecalis. After 24 h of incubation, characteristic mass spectra were obtained for all species. Processing these mass spectra by hierarchic clustering and principal component analysis (PCA) enabled us to differentiate between bacterial species. IMR-MS in conjunction with a cumulative end-point model provides the means for rapid growth detection and differentiation of Gram-positive bacteria on the species level, typically within an analysis time of less than 3 min per sample.

Volatile compound profiling for the identification of Gram-negative bacteria by ion-molecule reaction-mass spectrometry.

AIMS: Fast and reliable methods for the early detection and identification of micro-organism are of high interest. In addition to established methods, direct mass spectrometry-based analysis of volatile compounds (VCs) emitted by micro-organisms has recently been shown to allow species differentiation. Thus, a large number of pathogenic Gram-negative bacteria, which comprised Acinetobacter baumannii, Enterobacter cloacae, Escherichia coli, Klebsiella oxytoca, Pseudomonas aeruginosa, Proteus vulgaris and Serratia marcescens, were subjected to headspace VC composition analysis using direct mass spectrometry in a low sample volume that allows for automation. METHODS AND RESULTS: Ion-molecule reaction-mass spectrometry (IMR-MS) was applied to headspace analysis of the above bacterial samples incubated at 37°C starting with 10(2) CFU ml(-1) . Measurements of sample VC composition were performed at 4, 8 and 24 h. Microbial growth was detected in all samples after 8 h. After 24 h, species-specific mass spectra were obtained allowing differentiation between bacterial species. CONCLUSIONS: IMR-MS provided rapid growth detection and identification of micro-organisms using a cumulative end-point model with a short analysis time of 3 min per sample. SIGNIFICANCE AND IMPACT OF THE STUDY: Following further validation, the presented method of bacterial sample headspace VC analysis has the potential to be used for bacteria differentiation.