Multicenter comparison of Etest, Vitek2 and BD Phoenix to broth microdilution for beta-lactam susceptibility testing of Streptococcus pneumonia.

PURPOSE: To assess performance of Etest®, Vitek®2 and BD Phoenix™ to determine the susceptibility of Streptococcus pneumoniae strains to penicillin, ampicillin and cefotaxime. METHODS: Sixty unique S. pneumoniae challenge strains were selected to cover a wide range of penicillin, ampicillin and cefotaxime minimal inhibitory concentrations (MICs). Strains were analyzed in four different Belgian laboratories. Etest® benzylpenicillin (BEN), ampicillin/amoxicillin (AMP) and cefotaxime (CTA) (bioMérieux), Vitek®2 AST-ST03 (bioMérieux) and BD Phoenix™ SMIC/ID-11 testing were each performed in two different labs. Results were compared to Sensititre® broth microdilution (BMD) (Thermo Fisher Scientific) results. MIC results were interpreted using EUCAST non-meningitis breakpoints (v 13.0). RESULTS: Essential agreement (EA) was ≥ 90% for all methods compared to BMD, except for Etest® BEN on Oxoid plate (58.3%), Etest® AMP (both on Oxoid (65.8%) and BD BBL plate (84.2%)). Categorical agreement (CA) for penicillin was only ≥ 90% for Vitek®2, for other methods CA ranged between 74 and 84%. CA for AMP was for all methods < 90% (range 75.8-88.3%) and CA for CTA was between 87 and 90% for all methods except for Etest on Oxoid plate (79.2%). CONCLUSIONS: Our study indicates that Vitek®2 and BD Phoenix™ are reliable for providing accurate pneumococcal susceptibility results for BEN, AMP and CTA. Using Etest BEN or AMP on Oxoid plate carries a risk of underestimating the MIC and should be interpreted with caution, especially when the obtained MIC is 1 or 2 doubling dilutions below the S or R clinical breakpoint.

Multicenter interlaboratory study of routine systems for the susceptibility testing of temocillin using a challenge panel of multidrug-resistant strains.

Accurate susceptibility result of temocillin (TMO) is important for treating infections caused by multidrug-resistant Enterobacterales. This multicenter study aimed to investigate the performance of routine temocillin testing assays against Enterobacterales challenging strains. Forty-seven selected clinical isolates were blindly analyzed by 12 Belgian laboratories using VITEK® 2 (n = 5) and BD Phoenix™ (n = 3) automated systems, ETEST® gradient strip (n = 3), and disk (3 brands) diffusion method (DD; n = 6) for temocillin susceptibility using standardized methodology. Results were interpreted using EUCAST 2023 criteria and compared to the broth microdilution (BMD; Sensititre™ panel) method used as gold standard. Methods' reproducibility was assessed by testing 3 reference strains in triplicate. A total of 702 organism-drug results were obtained against 33 TMO-susceptible and 14 TMO-resistant isolates. Excluding Proteae species (P. mirabilis and M. morganii), the essential agreement rates were excellent (91.5-100%) for all MIC-based methods. The highest category agreement was achieved by ETEST® (97.5%) followed by VITEK® 2 (93.2%), disk diffusion (91.6%), and BD Phoenix™ (88.5%). BD Phoenix™ and paper disk diffusion overcalled resistance (11.5% and 6.8% of major discrepancies, respectively), while ROSCO tablets diffusion and VITEK® 2 generated higher very major discrepancies (7.1% and 4.2% respectively). Inter-assay reproducibility was unsatisfactory using recommended E. coli ATCC 25922 strain but was excellent with E. coli ATCC 35218 and K. pneumoniae ATCC 700603 strains. This interlaboratory study suggests that routine testing methods provide accurate and reproducible TMO categorization results except for Proteae species.

Multicenter study of automated systems for colistin susceptibility testing.

PURPOSE: Broth microdilution (BMD) stays as the reference testing method for determination of antimicrobial susceptibility testing (AST) to colistin and is considered essential for patient management and for monitoring of colistin resistance. This multicenter study aimed to evaluate the performance of automated systems for colistin AST among Enterobacterales as an alternative for BMD since the majority of laboratories use automated systems as first-line method. METHODS: Twenty colistin resistant (COL-R) including 10 MCR producers and 10 colistin-susceptible (COL-S) Enterobacterales isolates were blindly tested for colistin susceptibility with the routine automated AST systems used by 8 laboratories (3 with BD Phoenix, 3 with Vitek2 and 2 with MicroScan). Additionally, 3 reference strains (E. coli ATCC 25922, E. coli NCTC 13846, and one COL-R mcr-negative K. pneumoniae M/14750) were tested in triplicate by each laboratory. RESULTS AND CONCLUSION: Results were compared with BMD performed at the reference laboratory. BD Phoenix and MicroScan automated AST systems provide accurate and reproducible categorical results for the testing of colistin in Enterobacterales. However, Vitek2 system showed poor performance for the detection of COL-R isolates especially those with MICs close to the susceptibility breakpoint (categorical agreement of 88% and precision categorical agreement of 81%).

Isolation, characterization and antibiotic resistance of Proteus mirabilis from Belgian broiler carcasses at retail and human stool.

Proteus mirabilis is an important pathogen involved in human urinary tract infections, and also more isolated from stools of patients with diarrheal disease than from healthy patients. The role of food, especially poultry products as source for human infection and multi-resistant strains remains unclear. As a resident in broilers' intestines, P. mirabilis can contaminate broiler carcasses due to slaughter practices, and be a risk for human infection. The present study evaluated the performance of five isolation media, and subsequently examined the presence of P. mirabilis on broiler carcasses at retail. Additionally, isolates were characterized by the Dienes' test, repetitive element PCR fingerprinting and pulsed-field gel electrophoresis, and their antibiotic resistance profile determined. Using a combined isolation protocol on blood agar, xylose lysine deoxycholate agar and violet red bile glucose agar, P. mirabilis was isolated from 29 out of 80 broiler carcasses (36.25%) with a mean contamination level of 2.25 ± 0.50 log10 CFU/g. A high strain heterogeneity was present in isolates from broilers and human stool. The same strains were not shared, but the antibiotic resistance profiling was similar. A role of poultry products as source for human infection should be taken into account.

Use of fosfomycin as targeted antibiotic prophylaxis before prostate biopsy: A prospective randomized study.

OBJECTIVES: To investigate whether switching ciprofloxacin to fosfomycin in the case of fluoroquinolone-resistant rectal bacteria influences the incidence of infectious complications after transrectal prostate biopsy. METHODS: From December 2015 until December 2017, patients undergoing prostate biopsy were randomly assigned to a control group or an intervention group in a prospective, open-label fashion at three different centers. The presence of fluoroquinolone-resistant organisms was detected by rectal swabs. Patients in the control group received ciprofloxacin. Patients in the intervention group received fosfomycin instead of ciprofloxacin in the case of fluoroquinolone-resistant bacteria on rectal swab culture. The primary end-point was the difference in occurrence of major (febrile) and minor (afebrile) infections between both groups. RESULTS: A total of 102 patients were randomized to the control group, and 102 patients to the intervention group. In the control group, nine complications occurred, of which five were major febrile complications. In the intervention group, six complications occurred, of which four were major febrile complications. The total number of complications (major and minor) did not differ between both groups (P = 0.59). A subgroup analysis of patients with fluoroquinolone-resistant bacteria on rectal swab showed five complications in the control group and one complication in the intervention group (P = 0.09). CONCLUSIONS: This represents the first prospective randomized study using rectal cultures for targeted antibiotic prophylaxis. Study findings show promising results for use of fosfomycin in patients with fluoroquinolone resistance.

Decontamination Strategies and Bloodstream Infections With Antibiotic-Resistant Microorganisms in Ventilated Patients: A Randomized Clinical Trial.

Importance: The effects of chlorhexidine (CHX) mouthwash, selective oropharyngeal decontamination (SOD), and selective digestive tract decontamination (SDD) on patient outcomes in ICUs with moderate to high levels of antibiotic resistance are unknown. Objective: To determine associations between CHX 2%, SOD, and SDD and the occurrence of ICU-acquired bloodstream infections with multidrug-resistant gram-negative bacteria (MDRGNB) and 28-day mortality in ICUs with moderate to high levels of antibiotic resistance. Design, Setting, and Participants: Randomized trial conducted from December 1, 2013, to May 31, 2017, in 13 European ICUs where at least 5% of bloodstream infections are caused by extended-spectrum ß-lactamase-producing Enterobacteriaceae. Patients with anticipated mechanical ventilation of more than 24 hours were eligible. The final date of follow-up was September 20, 2017. Interventions: Standard care was daily CHX 2% body washings and a hand hygiene improvement program. Following a baseline period from 6 to 14 months, each ICU was assigned in random order to 3 separate 6-month intervention periods with either CHX 2% mouthwash, SOD (mouthpaste with colistin, tobramycin, and nystatin), or SDD (the same mouthpaste and gastrointestinal suspension with the same antibiotics), all applied 4 times daily. Main Outcomes and Measures: The occurrence of ICU-acquired bloodstream infection with MDRGNB (primary outcome) and 28-day mortality (secondary outcome) during each intervention period compared with the baseline period. Results: A total of 8665 patients (median age, 64.1 years; 5561 men [64.2%]) were included in the study (2251, 2108, 2224, and 2082 in the baseline, CHX, SOD, and SDD periods, respectively). ICU-acquired bloodstream infection with MDRGNB occurred among 144 patients (154 episodes) in 2.1%, 1.8%, 1.5%, and 1.2% of included patients during the baseline, CHX, SOD, and SDD periods, respectively. Absolute risk reductions were 0.3% (95% CI, -0.6% to 1.1%), 0.6% (95% CI, -0.2% to 1.4%), and 0.8% (95% CI, 0.1% to 1.6%) for CHX, SOD, and SDD, respectively, compared with baseline. Adjusted hazard ratios were 1.13 (95% CI, 0.68-1.88), 0.89 (95% CI, 0.55-1.45), and 0.70 (95% CI, 0.43-1.14) during the CHX, SOD, and SDD periods, respectively, vs baseline. Crude mortality risks on day 28 were 31.9%, 32.9%, 32.4%, and 34.1% during the baseline, CHX, SOD, and SDD periods, respectively. Adjusted odds ratios for 28-day mortality were 1.07 (95% CI, 0.86-1.32), 1.05 (95% CI, 0.85-1.29), and 1.03 (95% CI, 0.80-1.32) for CHX, SOD, and SDD, respectively, vs baseline. Conclusions and Relevance: Among patients receiving mechanical ventilation in ICUs with moderate to high antibiotic resistance prevalence, use of CHX mouthwash, SOD, or SDD was not associated with reductions in ICU-acquired bloodstream infections caused by MDRGNB compared with standard care. Trial Registration: ClinicalTrials.gov Identifier: NCT02208154.

Endomyocardial and pericardial aspergillosis in critically ill patients.

Invasive aspergillosis(IA) is a potentially lethal complication of Aspergillus infection affecting mainly immunocompromised hosts; however, during the last two decades its incidence was increasingly observed in critically ill immunocompetent patients. The objective of this study is to describe the clinical characteristics of histologically proven endomyocardial and pericardial invasion, in the context of IA, in critically ill patients. Eight critically ill patients with histopathological confirmation of endomyocardial/pericardial aspergillosis were evaluated. Risk factors, clinical and laboratory characteristics, treatment, histopathological characteristics and mortality were recorded. Signs and symptoms of cardiac dysfunction were not observed in any of the patients. Therapy was administered to six of them shortly after the first positive culture. The observed histopathological lesions included haemorrhagic lesions, small vessels with central thrombosis and surrounding consolidated tissue with necrosis. Voriconazole, caspofungin, lipid amphotericin B and itraconazole were the used antifungals. The mortality rate was high (87.5%). Endomyocardial and pericardial aspergillosis are devastating complications of invasive aspergillosis. Clinical suspicion is low making the diagnosis difficult, therefore histopathological examination of tissues are required. The mortality is high.

Antimicrobial susceptibility testing of Arcobacter butzleri and Arcobacter cryaerophilus strains isolated from Belgian patients.

OBJECTIVES: To evaluate the feasibility of different methods for susceptibility testing of human Arcobacter isolates, to assess susceptibility to antibiotics commonly used to treat diarrhoeal illness and to obtain MIC distribution data. METHODS: One-hundred-and-six unique Arcobacter strains were collected during an epidemiological study on pathogens in gastroenteritis. Strains were identified by multiplex PCR and PCR-RFLP, and characterized by PFGE. Susceptibility to ampicillin, erythromycin, tetracycline, doxycycline, gentamicin and ciprofloxacin was determined using gradient strip and disc diffusion methodology. Optimal conditions for growth and incubation were tested. Azithromycin was tested with gradient strip diffusion on a subset of 40 strains. Sequence analysis of the quinolone resistance-determining region of gyrA was performed for a subset of 18 strains. RESULTS: Based on gradient diffusion results, most Arcobacter strains were susceptible to gentamicin (99%) and tetracycline (89%). Erythromycin (78%), ciprofloxacin (72%) and doxycycline (76%) retained moderate activity against Arcobacter spp. Only 9% of the strains were susceptible to ampicillin. Most Arcobacter butzleri strains were susceptible to ciprofloxacin (87%), whereas half of the Arcobacter cryaerophilus isolates (51%) showed high-level resistance (MIC >32 mg/L). MIC50 values were comparable for both macrolide antibiotics. Ciprofloxacin-resistant strains possessed an identical mutation in gyrA. Overall, categorical agreement between gradient and disc diffusion results was 60%. Gradient diffusion showed superior readability. CONCLUSIONS: Gradient diffusion methodology is preferred for routine susceptibility testing. Acquired resistance to fluoroquinolones was observed in A. cryaerophilus. Macrolides are not first-choice empirical antibiotics for Arcobacter infections. Tetracyclines can be suggested for treatment of documented Arcobacter-related gastrointestinal infections.

Epidemiology of invasive aspergillosis in critically ill patients: clinical presentation, underlying conditions, and outcomes.

INTRODUCTION: Invasive aspergillosis (IA) is a fungal infection that particularly affects immunocompromised hosts. Recently, several studies have indicated a high incidence of IA in intensive care unit (ICU) patients. However, few data are available on the epidemiology and outcome of patients with IA in this setting. METHODS: An observational study including all patients with a positive Aspergillus culture during ICU stay was performed in 30 ICUs in 8 countries. Cases were classified as proven IA, putative IA or Aspergillus colonization according to recently validated criteria. Demographic, microbiologic and diagnostic data were collected. Outcome was recorded 12 weeks after Aspergillus isolation. RESULTS: A total of 563 patients were included, of whom 266 were colonized (47%), 203 had putative IA (36%) and 94 had proven IA (17%). The lung was the most frequent site of infection (94%), and Aspergillus fumigatus the most commonly isolated species (92%). Patients with IA had higher incidences of cancer and organ transplantation than those with colonization. Compared with other patients, they were more frequently diagnosed with sepsis on ICU admission and more frequently received vasopressors and renal replacement therapy (RRT) during the ICU stay. Mortality was 38% among colonized patients, 67% in those with putative IA and 79% in those with proven IA (P < 0.001). Independent risk factors for death among patients with IA included older age, history of bone marrow transplantation, and mechanical ventilation, RRT and higher Sequential Organ Failure Assessment score at diagnosis. CONCLUSIONS: IA among critically ill patients is associated with high mortality. Patients diagnosed with proven or putative IA had greater severity of illness and more frequently needed organ support than those with Aspergillus spp colonization.

Prevalence of Arcobacter species among humans, Belgium, 2008-2013.

We examined fecal samples from 6,774 patients with enteritis in Belgium, 2008-2013. Members of the genus Arcobacter were the fourth most common pathogen group isolated, and the isolation rate was higher than previously reported. Culturing Arcobacter in a microbiology laboratory is feasible and should thus be tested for in cases of diarrheal disease.

Campylobacter occurrence and antimicrobial resistance profile in under five-year-old diarrheal children, backyard farm animals, and companion pets.

Campylobacteriosis disproportionately affects children under five in low-income countries. However, epidemiological and antimicrobial resistance (AMR) information at the children-animal interface is lacking. We hypothesized that Campylobacter is a major cause of enteritis in children in Ethiopia, and contact with animals is a potential source of transmission. The objective of the study was to determine Campylobacter occurrence and its AMR in children under five with diarrhea, backyard farm animals, and companion pets. Stool from 303 children and feces from 711 animals were sampled. Campylobacter was isolated through membrane filtration on modified charcoal cefoperazone deoxycholate agar plates under microaerobic incubation, and the technique showed to be feasible for use in regions lacking organized laboratories. Typical isolates were characterized with MALDI-TOF MS and multiplex PCR. Of 303 children, 20% (n = 59) were infected, with a higher proportion in the 6 to 11-month age group. Campylobacter occurred in 64% (n = 14) of dogs and 44% (n = 112) of poultry. Campylobacter jejuni was present in both a child and animal species in 15% (n = 23) of 149 households positive for Campylobacter. MICs using the gradient strip diffusion test of 128 isolates displayed resistance rates of 20% to ciprofloxacin and 11% to doxycycline. MICs of ciprofloxacin and doxycycline varied between C. coli and C. jejuni, with higher resistance in C. coli and poultry isolates. Campylobacter infection in children and its prevalent excretion from backyard poultry and dogs is a understudied concern. The co-occurrence of C. jejuni in animals and children suggest household-level transmission As resistance to ciprofloxacin and doxycycline was observed, therapy of severe campylobacteriosis should consider susceptibility testing. Findings from this study can support evidence-based diagnosis, antimicrobial treatment, and further investigations on the spread of AMR mechanisms for informed One Health intervention.

A clinical algorithm to diagnose invasive pulmonary aspergillosis in critically ill patients.

RATIONALE: The clinical relevance of Aspergillus-positive endotracheal aspirates in critically ill patients is difficult to assess. OBJECTIVES: We externally validate a clinical algorithm to discriminate Aspergillus colonization from putative invasive pulmonary aspergillosis in this patient group. METHODS: We performed a multicenter (n = 30) observational study including critically ill patients with one or more Aspergillus-positive endotracheal aspirate cultures (n = 524). The diagnostic accuracy of this algorithm was evaluated using 115 patients with histopathologic data, considered the gold standard. Subsequently, the diagnostic workout of the algorithm was compared on the total cohort (n = 524), with the categorization based on the diagnostic criteria of the European Organization for the Research and Treatment of Cancer/Mycoses Study Group. MEASUREMENTS AND MAIN RESULTS: Among 115 histopathology-controlled patients, 79 had proven aspergillosis. The algorithm judged 86 of 115 cases to have putative aspergillosis. This diagnosis was confirmed in 72 and rejected in 14 patients. The algorithm judged 29 patients to have Aspergillus colonization. This was confirmed in 22 and rejected in 7 patients. The algorithm had a specificity of 61% and a sensitivity of 92%. The positive and negative predictive values were 61 and 92%, respectively. In the total cohort (n = 524), 79 patients had proven invasive pulmonary aspergillosis (15.1%). According to the European Organization for the Research and Treatment of Cancer/Mycoses Study Group criteria, 32 patients had probable aspergillosis (6.1%) and 413 patients were not classifiable (78.8%). The algorithm judged 199 patients to have putative aspergillosis (38.0%) and 246 to have Aspergillus colonization (46.9%). CONCLUSIONS: The algorithm demonstrated favorable operating characteristics to discriminate Aspergillus respiratory tract colonization from invasive pulmonary aspergillosis in critically ill patients.

Occurrence of putative virulence genes in arcobacter species isolated from humans and animals.

Interest in arcobacters in veterinary and human public health has increased since the first report of the isolation of arcobacters from food of animal origin. Since then, studies worldwide have reported the occurrence of arcobacters on food and in food production animals and have highlighted possible transmission, especially of Arcobacter butzleri, to the human population. In humans, arcobacters are associated with enteritis and septicemia. To assess their clinical relevance for humans and animals, evaluation of potential virulence factors is required. However, up to now, little has been known about the mechanisms of pathogenicity. Because of their close phylogenetic affiliation to the food-borne pathogen Campylobacter and their similar clinical manifestations, the presence of nine putative Campylobacter virulence genes (cadF, ciaB, cj1349, hecA, hecB, irgA, mviN, pldA, and tlyA) previously identified in the recent Arcobacter butzleri ATCC 49616 genome sequence was determined in a large set of human and animal Arcobacter butzleri, Arcobacter cryaerophilus, and Arcobacter skirrowii strains after the development of rapid and accurate PCR assays and confirmed by sequencing and dot blot hybridization.

Three Cases of Atypical Pneumonia with Chlamydia psittaci: The Role of Laboratory Vigilance in the Diagnosis of Psittacosis.

Chlamydia psittaci is an established zoonotic agent causing respiratory disease in humans. An infection often remains asymptomatic but can also result in flu-like illness, pneumonia or even multi-organ failure. This paper describes three patients, hospitalised at AZ Sint-Lucas Hospital, with atypical pneumonia who were diagnosed with C. psittaci after an in-depth anamnesis and laboratory investigation in the midst of the COVID pandemic. All three infections were confirmed with PCR and serology, whereas viable bacteria were only present for one patient. Genotyping revealed the presence of genotype B for patient 1 and 2 whereas ompA genotyping was unsuccessful for patient 3. This case report demonstrates the importance of a thorough patient history as close contact with birds is one of the main risk factors to contract the pathogen. Once exposure to birds has been confirmed, a diagnosis by a combination of PCR and serology is essential in order to initiate a treatment with the proper antibiotics. As psittacosis is still an underestimated and underdiagnosed disease, communication between laboratory, clinicians and bird fanciers is encouraged.

Multicentre interlaboratory analysis of routine susceptibility testing with a challenge panel of resistant strains.

OBJECTIVES: In order to elaborate a new national challenge panel of resistant Gram-negative bacilli and Gram-positive cocci strains for the validation of routine antimicrobial susceptibility testing (AST) methods, an interlaboratory evaluation was organised. METHODS: The results of 12 well-characterised multidrug-resistant strains tested by nine laboratories using local disk diffusion (DD) and automated AST (AUST) methods were compared with the reference broth microdilution method. RESULTS: Overall categorical agreement ranged from 70% to 100% both for DD and AUST and was >90% for all but one strain for all antibiotics. CONCLUSION: Our multicentre AST study showed good reproducibility and the panel can be used as national resistant reference strains for routine AST validation.

On the nature of peculiar expectorated bronchial casts: Can infrared spectroscopy enlighten us?

BACKGROUND: Bronchial casts can be defined as gelatinous structures originating from the airways. While several cases of bronchial cast formation have been reported in literature, unravelling its nature is often a difficult task. METHODS: In this case report, we applied infrared (IR) spectroscopy on a bronchial cast fragment originating from a patient who suffered from a 2-y history of frequent coughing accompanied by the occasional expectoration of viscous and thick white-yellow bronchial-like structures. RESULTS: Based on a markedly high lipid to protein ratio and presence of long-chain fatty acids, the resulting IR spectrum appeared to be very suggestive for chyloptysis. CONCLUSION: Taking into account the patient's prior history of radiation therapy for a lymphoma complicated by congestive heart failure, we hypothesized that an impairment of adequate lymphatic flow into the venous system due to a combination of lymphatic obstruction and high venous pressures is the most plausible culprit.

Performance of a new chromogenic medium, BBL CHROMagar MRSA II (BD), for detection of methicillin-resistant Staphylococcus aureus in screening samples.

Two chromogenic media for the detection of MRSA were compared: BBL CHROMagar MRSA II (BD) and MRSA ID agar (bioMérieux). Following overnight nonselective enrichment, 1,919 screening samples were inoculated on both chromogenic agars. After 24 h, the sensitivities of both media were high and comparable. Both media showed an important decrease in specificity after 48 h of incubation (decreases of 8% for MRSA II and 10% for MRSA ID), but MRSA II was significantly more specific at both time points.

A Bird's-Eye View of Chronic Unilateral Conjunctivitis: Remember about Chlamydia psittaci.

Chlamydia psittaci causes psittacosis in humans, mainly in people in contact with birds in either the setting of occupational or companion bird exposure. Infection is associated with a range of clinical manifestations from asymptomatic infection to severe atypical pneumonia and systemic disease. C. psittaci has also been associated with ocular adnexal lymphoma in human patients. The current paper describes successful doxycycline treatment of a male patient suffering from C. psittaci chronic unilateral conjunctivitis, most probably linked to the visit of a South African wildlife reserve. Increased awareness among general and occupational physicians, ophthalmologists, clinicians, and the public on the potential of C. psittaci to cause ocular infection is needed.

Filling the gaps in clinical proteomics: a do-it-yourself guide for the identification of the emerging pathogen Arcobacter by matrix-assisted laser desorption ionization-time of flight mass spectrometry.

Arcobacters are considered emerging gastrointestinal pathogens. Rapid, reliable and species-specific identification of these bacteria is important. Biochemical tests commonly yield negative or variable results. Molecular methods prove more reliable but are time consuming and lack specificity. Matrix assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) is a fast, cheap and robust technique that has revolutionized genus and species identification in clinical microbiology. The performance of an in vitro diagnostic (RUO) spectral database of MALDI-TOF MS for the identification of human clinically relevant Arcobacter isolates was validated and compared to an in house created Reference Spectral database (RS) containing a representative set of deposited Arcobacter strains of zoonotic interest. A challenge panel of clinical, human and veterinary, unique Campylobacteraceae strains was used to test accuracy. Using direct colony transfer, sensitivity with RS was significantly better than with RUO for A. butzleri and A. cryaerophilus identification (100% and 92% versus 74% and 16%). For A. skirrowii, sensitivity remained low (21% versus 0%). Reanalysis using formic acid overlay (on-target extraction) augmented sensitivity for the latter species to 64%. Specificity of RS database remained excellent without any misidentifications of human clinical strains including Campylobacter fetus and C. jejuni/coli. The use of an enriched database for MALDI-TOF MS identification of Arcobacter spp. of human interest produced high-confidence identifications to species level resulting in a significantly improved sensitivity with conservation of excellent specificity. Misidentifications, which can have therapeutic and public health consequences, were not encountered.