BACKGROUND:Methicillin resistant Staphylococcus aureus (MRSA) is a major burden for hospitals globally. However, in the Netherlands, the MRSA prevalence is relatively low due to the 'search and destroy' policy. Routine multiple-locus variable-number of tandem repeat analysis (MLVA) of MRSA isolates supports outbreak detection. However, whole genome multiple locus sequence typing (wgMLST) is superior to MLVA in identifying (pseudo-)outbreaks with MRSA. The present study describes a pseudo-outbreak of MRSA at the bacteriology laboratory of a large Dutch teaching hospital.METHODS:All staff members of the bacteriology laboratory of the Elisabeth-TweeSteden hospital were screened for MRSA carriage, after a laboratory contamination with MRSA was suspected. Clonal relatedness between the index isolate and the MRSA isolates from laboratory staff members and all previous MRSA isolates from the Elisabeth-TweeSteden hospital with the same MLVA-type as the index case was examined based on wgMLST using whole genome sequencing.RESULTS:One of the staff members was identified as the probable source of the laboratory contamination, because of carriage of a MRSA possessing the same MLVA-type as the index case. Eleven other isolates with the same molecular characteristics were found in the database, of which seven were retrospectively suspected of contamination. Clonal relatedness was found between ten isolates, including the isolate found in the staff member and the MRSA found in the index patient with a maximum of eleven alleles difference. All isolates were epidemiologically linked through the laboratory staff member, who had worked on all these cultures.CONCLUSIONS:The present study describes a MRSA pseudo-outbreak over a 2.5-year period due to laboratory contamination caused by a MRSA carrying laboratory staff member involving nine patients. In case of unexpected bacteriological findings, the possibility of a laboratory contamination should be considered.

Here we describe the characteristics of the first 100 laboratory confirmed COVID-19 patients admitted to the Elisabeth-Tweesteden Hospital (Tilburg, The Netherlands). The median age was 72 years, 67% was male, approximately 80% had co-morbidity, approximately 50% of which consisted of hypertension, cardiac and or pulmonary conditions and 25% diabetes. At admission 61% of patients had fever and about 50% presented at day 6 or more after onset of symptoms. At the time of writing 38 patients were discharged, 19 admitted to the intensive care unit (ICU) and 20 patients had died. The median age of ICU patients was 67 years and 63% had co-morbidity. The median time to discharge or to death was 6 and 5.5 days, respectively.

To rapidly assess possible community transmission in Noord-Brabant, the Netherlands, healthcare workers (HCW) with mild respiratory complaints and without epidemiological link (contact with confirmed case or visited areas with active circulation) were tested for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Within 2 days, 1,097 HCW in nine hospitals were tested; 45 (4.1%) were positive. Of six hospitals with positive HCW, two accounted for 38 positive HCW. The results informed local and national risk management.

BACKGROUND:10 days after the first reported case of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in the Netherlands (on Feb 27, 2020), 55 (4%) of 1497 health-care workers in nine hospitals located in the south of the Netherlands had tested positive for SARS-CoV-2 RNA. We aimed to gain insight in possible sources of infection in health-care workers. METHODS:We did a cross-sectional study at three of the nine hospitals located in the south of the Netherlands. We screened health-care workers at the participating hospitals for SARS-CoV-2 infection, based on clinical symptoms (fever or mild respiratory symptoms) in the 10 days before screening. We obtained epidemiological data through structured interviews with health-care workers and combined this information with data from whole-genome sequencing of SARS-CoV-2 in clinical samples taken from health-care workers and patients. We did an in-depth analysis of sources and modes of transmission of SARS-CoV-2 in health-care workers and patients. FINDINGS:Between March 2 and March 12, 2020, 1796 (15%) of 12 022 health-care workers were screened, of whom 96 (5%) tested positive for SARS-CoV-2. We obtained complete and near-complete genome sequences from 50 health-care workers and ten patients. Most sequences were grouped in three clusters, with two clusters showing local circulation within the region. The noted patterns were consistent with multiple introductions into the hospitals through community-acquired infections and local amplification in the community. INTERPRETATION:Although direct transmission in the hospitals cannot be ruled out, our data do not support widespread nosocomial transmission as the source of infection in patients or health-care workers. FUNDING:EU Horizon 2020 (RECoVer, VEO, and the European Joint Programme One Health METASTAVA), and the National Institute of Allergy and Infectious Diseases, National Institutes of Health.

Introduction Knowledge of within-patient dynamics of resistance plasmids during outbreaks is important for understanding the persistence and transmission of plasmid-mediated antimicrobial resistance. During an outbreak of a Klebsiella pneumoniae carbapenemase-producing (KPC) K. pneumoniae, the plasmid and chromosomal dynamics of K. pneumoniae within-patients were investigated. Methods During the outbreak, all K. pneumoniae isolates of colonized or infected patients were collected, regardless of their susceptibility pattern. A selection of isolates was short-read and long-read sequenced. A hybrid assembly of the short-and long-read sequence data was performed. Plasmid contigs were extracted from the hybrid assembly, annotated, and within patient plasmid comparisons were performed. Results Fifteen K. pneumoniae isolates of six patients were short-read whole-genome sequenced. Whole-genome multi-locus sequence typing revealed a maximum of 4 allele differences between the sequenced isolates. Within patients 1 and 2 the resistance gene- and plasmid replicon-content did differ between the isolates sequenced. Long-read sequencing and hybrid assembly of 4 isolates revealed loss of the entire KPC-gene containing plasmid in the isolates of patient 2 and a recombination event between the plasmids in the isolates of patient 1. This resulted in two different KPC-gene containing plasmids being simultaneously present during the outbreak. Conclusion During a hospital outbreak of a KPC-producing K. pneumoniae isolate, plasmid loss of the KPC-gene carrying plasmid and plasmid recombination was detected within the isolates from two patients. When investigating outbreaks, one should be aware that plasmid transmission can occur and the possibility of within- and between-patient plasmid variation needs to be considered.

Here we describe the characteristics of the first 100 laboratory confirmed COVID-19 patients admitted to the Elisabeth-Tweesteden Hospital (Tilburg, The Netherlands). The median age was 72 years, 67% was male, approximately 80% had co-morbidity, approximately 50% of which consisted of hypertension, cardiac and or pulmonary conditions and 25% diabetes. At admission 61% of patients had fever and about 50% presented at day 6 or more after onset of symptoms. At the time of writing 38 patients were discharged, 19 admitted to the intensive care unit (ICU) and 20 patients had died. The median age of ICU patients was 67 years and 63% had co-morbidity. The median time to discharge or to death was 6 and 5.5 days, respectively.

Ten days after the first reported case of SARS-CoV-2 infection in the Netherlands, 3.9% of healthcare workers (HCWs) in nine hospitals located in the South of the Netherlands tested positive for SARS-CoV-2 RNA. The extent of nosocomial transmission that contributed to the HCW infections was unknown. We combined epidemiological data, collected by means of structured interviews of HCWs, with whole genome sequencing (WGS) of SARS-CoV-2 in clinical samples from HCWs and patients in three of nine hospitals that participated in the HCW screening, to perform an in-depth analysis of sources and modes of transmission of SARS -CoV-2 in HCWs and patients. A total of 1,796 out of 12,022 HCWs (15%) of the three participating hospitals were screened, based on clinical symptoms, of whom 96 (5%) tested positive for SARS-CoV-2. We obtained complete genome sequences of 50 HCWs and 18 patients. Most sequences grouped in 3 clusters, with 2 clusters displaying local circulation within the region. The observed patterns are most consistent with multiple introductions into the hospitals through community acquired infections, and local amplification in the community. Although direct transmission in the hospitals cannot be ruled out, the data does not support widespread nosocomial transmission as source of infection in patients or healthcare workers. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This study has been partly funded by H2020 projects RECoVer (no. 101003589), VEO (No. 874735) and NIAID/NIH contract HHSN272201400008C ### Author Declarations All relevant ethical guidelines have been followed; any necessary IRB and/or ethics committee approvals have been obtained and details of the IRB/oversight body are included in the manuscript. Yes All necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes All data is available upon request

BACKGROUND: Since December 2019, the world is captivated by SARS-CoV-2, a new coronavirus that shows a lot of similaritieswith previous coronaviruses such as SARS and MERS Although it was initially seen mainly in China and the surrounding countries, now it also reached Europe, where a large region in northern Italy, in particular, encountered many infections CASE DESCRIPTION: Here we describe the first Dutch patient with COVID-19, a 56-year-old man whose infection appeared to be related to a trip to Northern Italy one week before presentation In the days that followed, the brother of the patient with whom he had traveled, his wife and daughter also tested positive CONCLUSION: At the moment much is still unclear and it is particularly important to quickly identify patients with an increased risk of complications and to prevent unrestrained spread in the Netherlands

BACKGROUND:Since December 2019, the world is captivated by SARS-CoV-2, a new coronavirus that shows a lot of similaritieswith previous coronaviruses such as SARS and MERS. Although it was initially seen mainly in China and the surrounding countries, now it also reached Europe, where a large region in northern Italy, in particular, encountered many infections.CASE DESCRIPTION:Here we describe the first Dutch patient with COVID-19, a 56-year-old man whose infection appeared to be related to a trip to Northern Italy one week before presentation. In the days that followed, the brother of the patient with whom he had traveled, his wife and daughter also tested positive.CONCLUSION:At the moment much is still unclear and it is particularly important to quickly identify patients with an increased risk of complications and to prevent unrestrained spread in the Netherlands.

Key Points Question What was the prevalence and clinical presentation of coronavirus disease 2019 among health care workers with self-reported fever or respiratory symptoms in 2 Dutch hospitals within 2 weeks after the first patient with coronavirus disease 2019 was detected in the Netherlands? Findings In this cross-sectional study that included 1353 health care workers with self-reported fever or respiratory symptoms, 6% were infected with severe acute respiratory syndrome coronavirus 2. Most health care workers with coronavirus disease 2019 experienced mild disease, and only 53% reported fever. Meaning The high prevalence of mild clinical presentations, frequently not including fever, suggests that the currently recommended case definition for suspected coronavirus disease 2019 should be used less stringently.

ABSTRACTBackgroundOn February 27, 2020, the first patient with COVID-19 was reported in the Netherlands. During the following weeks, nine healthcare workers (HCWs) were diagnosed with COVID-19 in two Dutch teaching hospitals, eight of whom had no history of travel to China or Northern-Italy. A low-threshold screening regimen was implemented to determine the prevalence and clinical presentation of COVID-19 among HCWs in these two hospitals.MethodsHCWs who suffered from fever or respiratory symptoms were voluntarily tested for SARS-CoV-2 by real-time reverse-transcriptase PCR on oropharyngeal samples. Structured interviews were conducted to document symptoms for all HCWs with confirmed COVID-19.FindingsThirteen-hundred fifty-three (14%) of 9,705 HCWs employed were tested, 86 (6%) of whom were infected with SARS-CoV-2. Most HCWs suffered from relatively mild disease and only 46 (53%) reported fever. Eighty (93%) HCWs met a case definition of fever and/or coughing and/or shortness of breath. None of the HCWs identified through the screening reported a travel history to China or Northern Italy, and 3 (3%) reported to have been exposed to an inpatient known with COVID-19 prior to the onset of symptoms.InterpretationWithin two weeks after the first Dutch case was detected, a substantial proportion of HCWs with fever or respiratory symptoms were infected with SARS-CoV-2, probably caused by acquisition of the virus in the community during the early phase of local spread. The high prevalence of mild clinical presentations, frequently not including fever, asks for less stringent use of the currently recommended case-definition for suspected COVID-19.RESEARCH IN PERSPECTIVEEvidence before this studyThis study was conducted in response to the global spread of SARS-CoV-2, and the detection of eight healthcare workers (HCWs) in two Dutch teaching hospitals within two weeks after the first patient with COVID-19 was detected in the Netherlands who had no history of travel to China or Northern-Italy, raising the question of whether undetected community circulation was occurring.Added value of this studyTo the best of our knowledge, this report is the first to describe the prevalence, the clinical presentation and early outcomes of COVID-19 in HCWs, which may be helpful for others seeking to identify HCWs suspected for COVID-19 in an outbreak situation.Implications of all the available evidenceWe describe that within two weeks after the first Dutch case was detected, a substantial proportion of HCWs with fever or (mild) respiratory symptoms were infected with SARS-CoV-2, probably caused by acquisition of the virus in the community during the early phase of local spread. The high prevalence of mild clinical presentations, frequently not including fever, asks for less stringent use of the currently recommended case-definition for suspected COVID-19.

Severe acute respiratory syndrome coronavirus (SARS-CoV)-2 infections often cause only mild disease that may evoke relatively low Ab titers compared with patients admitted to hospitals. Generally, total Ab bridging assays combine good sensitivity with high specificity. Therefore, we developed sensitive total Ab bridging assays for detection of SARS-CoV-2 Abs to the receptor-binding domain (RBD) and nucleocapsid protein in addition to conventional isotype-specific assays. Ab kinetics was assessed in PCR-confirmed, hospitalized coronavirus disease 2019 (COVID-19) patients (n = 41) and three populations of patients with COVID-19 symptoms not requiring hospital admission: PCR-confirmed convalescent plasmapheresis donors (n = 182), PCR-confirmed hospital care workers (n = 47), and a group of longitudinally sampled symptomatic individuals highly suspect of COVID-19 (n = 14). In nonhospitalized patients, the Ab response to RBD is weaker but follows similar kinetics, as has been observed in hospitalized patients. Across populations, the RBD bridging assay identified most patients correctly as seropositive. In 11/14 of the COVID-19-suspect cases, seroconversion in the RBD bridging assay could be demonstrated before day 12; nucleocapsid protein Abs emerged less consistently. Furthermore, we demonstrated the feasibility of finger-prick sampling for Ab detection against SARS-CoV-2 using these assays. In conclusion, the developed bridging assays reliably detect SARS-CoV-2 Abs in hospitalized and nonhospitalized patients and are therefore well suited to conduct seroprevalence studies.

Objectives: Antibiotic resistance in Gram-negative bacteria has been associated with increased mortality. This was demonstrated mostly for third-generation cephalosporin-resistant (3GC-R) Enterobacterales bacteraemia in international studies. Yet, the burden of resistance specifically in the Netherlands and created by all types of Gram-negative infection has not been quantified. We therefore investigated the attributable mortality of antibiotic resistance in Gram-negative infections in the Netherlands. Methods: In eight hospitals, a sample of Gram-negative infections was identified between 2013 and 2016, and separated into resistant and susceptible infection cohorts. Both cohorts were matched 1:1 to noninfected control patients on hospital, length of stay at infection onset, and age. In this parallel matched cohort set-up, 30-day mortality was compared between infected and non-infected patients. The impact of resistance was then assessed by dividing the two separate risk ratios (RRs) for mortality attributable to Gram-negative infection. Results: We identified 1954 Gram-negative infections, of which 1190 (61%) involved Escherichia coli, 210 (11%) Pseudomonas aeruginosa, and 758 (39%) bacteraemia. Resistant Gram-negatives caused 243 infections (12%; 189 (78%) 3GC-R Enterobacterales, nine (4%) multidrug-resistant P. aeruginosa, no carbapenemase-producing Enterobacterales). Subsequently, we matched 1941 non-infected controls. After adjustment, point estimates for RRs comparing mortality between infections and controls were similarly higher than 1 in case of resistant infections and susceptible infections (1.42 (95% confidence interval 0.66-3.09) and 1.32 (1.06-1.65), respectively). By dividing these, the RR reflecting attributable mortality of resistance was calculated as 1.08 (0.48-2.41). Conclusions: In the Netherlands, antibiotic resistance did not increase 30-day mortality in Gram-negative infections. (C) 2020 The Authors. Published by Elsevier Ltd on behalf of European Society of Clinical Microbiology and Infectious Diseases.

Objectives There is a global increase in infections caused by Gram-negative bacteria. The majority of research is on bacteremic Gram-negative infections (GNI), leaving a knowledge gap on the burden of non-bacteremic GNI. Our aim is to describe characteristics and determine the burden of bacteremic and non-bacteremic GNI in hospitalized patients in the Netherlands. Methods We conducted a prospective cohort study of patients in eight hospitals with microbiologically confirmed GNI, between June 2013 and November 2015. In each hospital the first five adults meeting the eligibility criteria per week were enrolled. We estimated the national incidence and mortality of GNI by combining the cohort data with a national surveillance database for antimicrobial resistance. Results 1,954 patients with GNI were included of which 758 (39%) were bloodstream infections (BSI). 243 GNI (12%) involved multi-drug resistant pathogens. 30-day mortality rate was 11.1% (n = 217) Estimated national incidences of non-bacteremic GNI and bacteremic GNI in hospitalized adults were 74 (95% CI 58 - 89) and 86 (95% CI 72-100) per 100,000 person years, yielding estimated annual numbers of 30-day all-cause mortality deaths of 1,528 (95% CI 1,102-1,954) for bacteremic and 982 (95% CI 688 - 1,276) for non-bacteremic GNI. Conclusion GNI form a large mortality burden in a low-resistance country. A third of the associated mortality occurs after non-bacteremic GNI.

Background Use of single-bed rooms for control of extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae is under debate; the added value when applying contact precautions has not been shown. We aimed to assess whether an isolation strategy of contact precautions in a multiple-bed room was non-inferior to a strategy of contact precautions in a single-bed room for preventing transmission of ESBL-producing Enterobacteriaceae. Methods We did a cluster-randomised, crossover, non-inferiority study on medical and surgical wards of 16 Dutch hospitals. During two consecutive study periods, either contact precautions in a single-bed room or contact precautions in a multiple-bed room were applied as the preferred isolation strategy for patients with ESBL-producing Enterobacteriaceae cultured from a routine clinical sample (index patients). Eligible index patients were aged 18 years or older, had no strict indication for barrier precautions in a single-bed room, had a culture result reported within 7 days of culture and before discharge, and had no wardmate known to be colonised or infected with an ESBLproducing Enterobacteriaceae isolate of the same bacterial species with a similar antibiogram. Hospitals were randomly assigned in a 1: 1 ratio by computer to one of two sequences of isolation strategies, stratified by university or non-university hospital. Allocation was masked for laboratory technicians who assessed the outcomes but not for patients, treating doctors, and infection-control practitioners enrolling index patients. The primary outcome was transmission of ESBL-producing Enterobacteriaceae to wardmates, which was defined as rectal carriage of an ESBLproducing Enterobacteriaceae isolate that was clonally related to the index patient's isolate in at least one wardmate. The primary analysis was done in the per-protocol population, which included patients who were adherent to the assigned room type. A 10% non-inferiority margin for the risk difference was used to assess non-inferiority. This study is registered with Nederlands Trialregister, NTR2799. Findings 16 hospitals were randomised, eight to each sequence of isolation strategies. All hospitals randomised to the sequence single-bed room then multiple-bed room and five of eight hospitals randomised to the sequence multiplebed room then single-bed room completed both study periods and were analysed. From April 24, 2011, to Feb 27, 2014, 1652 index patients and 12 875 wardmates were assessed for eligibility. Of those, 693 index patients and 9527 wardmates were enrolled and 463 index patients and 7093 wardmates were included in the per-protocol population. Transmission of ESBL-producing Enterobacteriaceae to at least one wardmate was identified for 11 (4%) of 275 index patients during the single-bed room strategy period and for 14 (7%) of 188 index patients during the multiple-bed room strategy period (crude risk difference 3.4%, 90% CI -0.3 to 7.1). Interpretation For patients with ESBL-producing Enterobacteriaceae cultured from a routine clinical sample, an isolation strategy of contact precautions in a multiple-bed room was non-inferior to a strategy of contact precautions in a singlebed room for preventing transmission of ESBL-producing Enterobacteriaceae. Non-inferiority of the multiple-bed room strategy might change the current single-bed room preference for isolation of patients with ESBL-producing Enterobacteriaceae and, thus, broaden infection-control options for ESBL-producing Enterobacteriaceae in daily clinical practice.

Objectives: Clostridium difficile infections (CDI) account for 1.5% of diarrhoeic episodes in patients attending a general practitioner in the Netherlands, but its sources are unknown. We searched for community clusters to recognize localized point sources of CDI. Methods: Between October 2010 and February 2012, a community-based prospective nested case-control study was performed in three laboratories in the Netherlands with a study population of 2 810 830 people. Bernoulli spatial scan and space-time permutation models were used to detect spatial and/or temporal clusters of CDI. In addition, a multivariate conditional logistic regression model was constructed to test livestock exposure as a supposed risk factor in CDI patients without hospital admission within the previous 12 weeks (community-acquired (CA) CDI). Results: In laboratories A, B and C, 1.3%, 1.8% and 2.1% of patients with diarrhoea tested positive for CDI, respectively. The mean age of CA-CDI patients (n = 124) was 49 years (standard deviation, 22.6); 64.5% were female. No spatial or temporal clusters of CDI cases were detected compared to C. difficile-negative diarrhoeic controls. Except for one false-positive signal, no spatiotemporal interaction amongst CDI cases was found. Livestock exposure was not related to CA-CDI (odds ratio, 0.99; 95% confidence interval, 0.44-2.24). Ten percent of CA-CDIs was caused by PCR ribotype 078, spatially dispersed throughout the study area. Conclusions: The absence of clusters of CDI cases in a community cohort of diarrhoeic patients suggests a lack of localized point sources of CDI in the living environment of these patients. (C) 2018 European Society of Clinical Microbiology and Infectious Diseases. Published by Elsevier Ltd. All rights reserved.

The i-4-1-Health project is a One Health project on the prevalence and spread of antimicrobial resistance in the human and veterinary domain in the Dutch-Belgian cross-border region. This paper describes the main components of the laboratory protocol that was developed to standardise the microbiological methods used for the detection of intestinal carriage of highly-resistant microorganisms.

Despite low sensitivity, culture of periprosthetic tissue (PPT) specimens on agars and in broths has traditionally been used for the detection of causative microorganisms in patients suspected for prosthetic joint infection (PJI). The aim of this study was to evaluate the added diagnostic value of culturing PPT in blood culture bottles (BCB) over the conventional combination of standard agar and broth alone. This prospective cohort study was conducted over a 12-month period and included consecutive patients undergoing revision arthroplasty. Overall, 113 episodes from 90 subjects were studied; 45 subjects (50.0%) met the Infectious Diseases Society of America (IDSA) criteria for PJI, of whom the majority (75.6%) had an acute infection. Sensitivity and specificity of culture were assessed using IDSA criteria for PJI as gold standard. Although the increase in sensitivity from 84.44 (CI 70.54; 93.51) to 93.33% (81.73; 98.60) was not significant, added diagnostic value of culturing PPT in BCBs was demonstrated by the significantly higher number of detected pathogens in culture sets with BCBs compared to culture without BCBs (61 pathogens in conventional set versus 89 when BCBs were included for 57 PJI episodes, P = <0.0001). In 17 (29.8%) episodes, microorganisms were cultured from BCBs only, and in 9 (52.9%) of these episodes, virulent pathogens were found. This study demonstrates that PPT culture in BCBs leads to isolation of additional microorganisms, both virulent and low-virulent, which were not cultured with use of agars and broths alone. Isolation of additional causative microorganisms has serious consequences for the treatment strategy in PJI.

The standard incubation time for antimicrobial susceptibility testing (AST) by disk diffusion is primarily based on laboratory working hours rather than growth and kill characteristics of bacteria. Faster AST results could result in better patient outcomes and reduced costs by initiating earlier appropriate therapy. The earliest possible reading moment for disk diffusion using established disk zone diameter breakpoints for Enterobacteriaceae was determined with a special focus on the accuracy of the results. A total of 88 Enterobacteriaceae challenge isolates, including isolates with specific resistance mechanisms such as extended-spectrum β-lactamase (ESBL), were subjected to disk diffusion with 15 antibiotics. Hourly images were automatically produced by an incubator/camera combination from 1 h to 20 h. Disk zones were plotted over time for all combinations. Essential and categorical agreement rates using the final reading after 20 h of incubation as a reference were calculated for every hour. In total, 1320 antibiotic-micro-organism combinations were tested. Clear growth with readable inhibition zones was visible after 6 h of incubation for the majority (95.8%) of plates and after 7 h for all incubated plates. However, zone sizes changed significantly after those time points for a number of strains. After 10 h of incubation, minor, major and very major error rates were 1.6% (n = 21), 0.2% (n = 1) and 0.7% (n = 4), respectively. The results of this study clearly indicate that early reading of inhibition zones to 10 h after incubation is feasible and accurate and thus may save significantly on turnaround time.