Validation of the prevalence to incidence conversion method for healthcare associated infections in long-term care facilities.

INTRODUCTION: Residents of long-term care facilities (LTCFs) are a population at high risk of developing severe healthcare associated infections (HAIs). In the assessment of HAIs in acute-care hospitals, selection bias can occur due to cases being over-represented: patients developing HAIs usually have longer lengths of stays compared to controls, and therefore have an increased probability of being sampled in PPS, leading to an overestimation of HAI prevalence. Our hypothesis was that in LTCFs, the opposite may occur: residents developing HAIs either may have a greater chance of being transferred to acute-care facilities or of dying, and therefore could be under-represented in PPS, leading to an underestimation of HAI prevalence. Our aim was to test this hypothesis by comparing HAI rates obtained through longitudinal and cross-sectional studies. METHODS: Results from two studies conducted simultaneously in four LTCFs in Italy were compared: a longitudinal study promoted by the European Centre for Disease Prevention and Control (ECDC, HALT4 longitudinal study, H4LS), and a PPS. Prevalence was estimated from the PPS and converted into incidence per year using an adapted version of the Rhame and Sudderth formula proposed by the ECDC. Differences between incidence rates calculated from the PPS results and obtained from H4LS were investigated using the Byar method for rate ratio (RR). RESULTS: On the day of the PPS, HAI prevalence was 1.47% (95% confidence interval, CI 0.38-3.97), whereas the H4LS incidence rate was 3.53 per 1000 patient-days (PDs, 95% CI 2.99-4.08). Conversion of prevalence rates obtained through the PPS into incidence using the ECDC formula resulted in a rate of 0.86 per 1000 PDs (95% CI 0-2.68). Comparing the two rates, a RR of 0.24 (95% CI 0.03-2.03, p 0.1649) was found. CONCLUSIONS: This study did not find significant differences between HAI incidence estimates obtained from a longitudinal study and through conversion from PPS data. Results of this study support the validity of the ECDC method.

Vancomycin resistant enterococcus risk factors for hospital colonization in hematological patients: a matched case-control study.

BACKGROUND: Vancomycin-resistant enterococcus (VRE) was the fastest growing pathogen in Europe in 2022 (+ 21%) but its clinical relevance is still unclear. We aim to identify risk factors for acquired VRE rectal colonization in hematological patients and evaluate the clinical impact of VRE colonization on subsequent infection, and 30- and 90-day overall mortality rates, compared to a matched control group. METHODS: A retrospective, single center, case-control matched study (ratio 1:1) was conducted in a hematological department from January 2017 to December 2020. Case patients with nosocomial isolation of VRE from rectal swab screening (≥ 48 h) were matched to controls by age, sex, ethnicity, and hematologic disease. Univariate and multivariate logistic regression compared risk factors for colonization. RESULTS: A total of 83 cases were matched with 83 controls. Risk factors for VRE colonization were febrile neutropenia, bone marrow transplant, central venous catheter, bedsores, reduced mobility, altered bowel habits, cachexia, previous hospitalization and antibiotic treatments before and during hospitalization. VRE bacteraemia and Clostridioides difficile infection (CDI) occurred more frequently among cases without any impact on 30 and 90-days overall mortality. Vancomycin administration and altered bowel habits were the only independent risk factors for VRE colonization at multivariate analysis (OR: 3.53 and 3.1; respectively). CONCLUSIONS: Antimicrobial stewardship strategies to reduce inappropriate Gram-positive coverage in hematological patients is urgently required, as independent risk factors for VRE nosocomial colonization identified in this study include any use of vancomycin and altered bowel habits. VRE colonization and infection did not influence 30- and 90-day mortality. There was a strong correlation between CDI and VRE, which deserves further investigation to target new therapeutic approaches.

The incidence and risk factors of selected drug prescriptions and outpatient care after SARS-CoV-2 infection in low-risk subjects: a multicenter population-based cohort study.

Background: Knowledge about the dynamics of transmission of SARS-CoV-2 and the clinical aspects of COVID-19 has steadily increased over time, although evidence of the determinants of disease severity and duration is still limited and mainly focused on older adult and fragile populations. Methods: The present study was conceived and carried out in the Emilia-Romagna (E-R) and Veneto Regions, Italy, within the context of the EU's Horizon 2020 research project called ORCHESTRA (Connecting European Cohorts to increase common and effective response to SARS-CoV-2 pandemic) (www.orchestra-cohort.eu). The study has a multicenter retrospective population-based cohort design and aimed to investigate the incidence and risk factors of access to specific healthcare services (outpatient visits and diagnostics, drug prescriptions) during the post-acute phase from day-31 to day-365 after SARS-CoV-2 infection, in a healthy population at low risk of severe acute COVID-19. The study made use of previously recorded large-scale healthcare data available in the administrative databases of the two Italian Regions. The statistical analysis made use of methods for competing risks. Risk factors were assessed separately in the two Regions and results were pooled using random effects meta-analysis. Results: There were 35,128 subjects in E-R and 88,881 in Veneto who were included in the data analysis. The outcome (access to selected health services) occurred in a high percentage of subjects in the post-acute phase (25% in E-R and 21% in Veneto). Outpatient care was observed more frequently than drug prescriptions (18% vs. 12% in E-R and 15% vs. 10% in Veneto). Risk factors associated with the outcome were female sex, age greater than 40 years, baseline risk of hospitalization and death, moderate to severe acute COVID-19, and acute extrapulmonary complications. Conclusion: The outcome of interest may be considered as a proxy for long-term effects of COVID-19 needing clinical attention. Our data suggest that this outcome occurs in a substantial percentage of cases, even among a previously healthy population with low or mild severity of acute COVID-19. The study results provide useful insights into planning COVID-19-related services.

Implementation of a centralized, web-based surveillance for healthcare associated infections among residents of long-term care facilities in Italy.

Objective: The Italian National Action Plan to contrast AMR identified among its objectives the development and implementation of a national Healthcare-Associated Infection (HAI) surveillance system based on European Centre for Disease Prevention and Control (ECDC) indications, through point prevalence surveys (PPS) of HAIs and antibiotic use in acute-care hospitals and long-term care facilities (LTCFs). We aimed to assess feasibility and appropriateness of proposed tools for a national surveillance system of HAIs and antibiotic use in LTCFs. Study design: Point prevalence survey. Methods: A pilot PPS was conducted between May-June 2022, among 15 LTCFs of 7 Italian regions. Data were collected in a single day in each LTCF, at the LTCF, ward, and resident levels, using a web-based data collection tool developed ad hoc. Data collector teams of each facility were invited to complete a questionnaire investigating opinions on the proposed tools. Results: Among 1025 included residents, the prevalence of residents with at least one HAI was 2.5% (95% CI 1.7%-3.7%) considering all HAIs and 2.2% (95% CI 1.3%-3%) without considering SARS-CoV-2 infections. The prevalence of antimicrobial use was 3% (95% CI 0.2%-4.3%). Overall, most respondents were satisfied with the web-based software, training and protocol, even though some difficulties were reported. Conclusions: A national surveillance network was established, which will facilitate future surveillance efforts. Further studies are necessary to evaluate the impact of the pandemic on HAI transmission and antibiotic use in LTCFs.

Early Warning Systems for Emerging Profiles of Antimicrobial Resistance in Italy: A National Survey.

Antimicrobial resistance (AMR) national surveillance systems in Italy lack alert systems for timely detection of emerging profiles of AMR with potential relevance to public health. Furthermore, the existence of early warning systems (EWS) at subnational level is unclear. This study aims at mapping and characterizing EWS for microbiological threats available at regional level in Italy, focusing on emerging AMR, and at outlining potential barriers and facilitators to their development/implementation. To this end, a three-section, web-based survey was developed and administered to all Italian regional AMR representatives from June to August 2022. Twenty out of twenty-one regions and autonomous provinces (95.2%) responded to the survey. Among these, nine (45%) reported the implementation of EWS for microbiological threats at regional level, three (15%) reported that EWS are in the process of being developed, and eight (40%) reported that EWS are not currently available. EWS characteristics varied widely among the identified systems concerning both AMR profiles reported and data flow: the microorganisms most frequently included were extensively drug-resistant (XDR) Enterobacterales, with the lack of a dedicated regional IT platform reported in most cases. The results of this study depict a highly heterogeneous scenario and suggest that more efforts aimed at strengthening national AMR surveillance systems are needed.

Increasing Number of Cases Due to Candida auris in North Italy, July 2019-December 2022.

Candida auris is an emerging fungus that represents a serious health threat globally. In Italy, the first case was detected in July 2019. Then, one case was reported to the Ministry of Health (MoH) on January 2020. Nine months later, a huge number of cases were reported in northern Italy. Overall, 361 cases were detected in 17 healthcare facilities between July 2019 and December 2022 in the Liguria, Piedmont, Emilia-Romagna, and Veneto regions, including 146 (40.4%) deaths. The majority of cases (91.8%) were considered as colonised. Only one had a history of travel abroad. Microbiological data on seven isolates showed that all but one strain (85.7%) were resistant to fluconazole. All the environmental samples tested negative. Weekly screening of contacts was performed by the healthcare facilities. Infection prevention and control (IPC) measures were applied locally. The MoH nominated a National Reference Laboratory to characterise C. auris isolates and store the strains. In 2021, Italy posted two messages through the Epidemic Intelligence Information System (EPIS) to inform on the cases. On February 2022, a rapid risk assessment indicated a high risk for further spread within Italy, but a low risk of spread to other countries.

Reduction trend of mcr-1 circulation in Emilia-Romagna Region, Italy.

This study aims to describe trends of mcr-positive Enterobacterales in humans based on laboratory surveillance with a defined catchment population. The data source is the Micro-RER surveillance system, established in Emilia-Romagna region (Italy), to monitor the trend of mcr resistance. Enterobacterales isolates from human clinical samples with minimum inhibitory concentration (MIC) ≥ 2 mg/L for colistin were sent to the study reference laboratory for the detection of mcr genes. Isolates prospectively collected in the period 2018-2020 were considered for the assessment of population rates and trends; further analyses were carried out for the evaluation of clonality and horizontal mcr gene transfer. Previous isolates from local laboratory collection were also described. In the period 2018-2020, 1164 isolates were sent to the reference laboratory, and 51 (4.4%) were confirmed as mcr-positive: 50 mcr-1 (42 Escherichia coli, 6 Klebsiella pneumoniae, 2 Salmonella enterica) and 1 mcr-4 (Enterobacter cloacae). The number of mcr-positive isolates dropped from 24 in the first half of 2018 to 3 in the whole of 2020 (trend p value < 0.001). Genomic analyses showed the predominant role of the horizontal transfer of mcr genes through plasmids or dissemination of transposable elements compared to clonal dissemination of mcr-positive microorganisms. The study results demonstrate a substantial decrease in the circulation of mcr-1 plasmid genes in Emilia-Romagna Region.

High impact of COVID-19 in long-term care facilities, suggestion for monitoring in the EU/EEA, May 2020.

Residents in long-term care facilities (LTCF) are a vulnerable population group. Coronavirus disease (COVID-19)-related deaths in LTCF residents represent 30-60% of all COVID-19 deaths in many European countries. This situation demands that countries implement local and national testing, infection prevention and control, and monitoring programmes for COVID-19 in LTCF in order to identify clusters early, decrease the spread within and between facilities and reduce the size and severity of outbreaks.

A proposal for a comprehensive approach to infections across the surgical pathway.

Despite evidence supporting the effectiveness of best practices in infection prevention and management, many healthcare workers fail to implement them and evidence-based practices tend to be underused in routine practice. Prevention and management of infections across the surgical pathway should always focus on collaboration among all healthcare workers sharing knowledge of best practices. To clarify key issues in the prevention and management of infections across the surgical pathway, a multidisciplinary task force of experts convened in Ancona, Italy, on May 31, 2019, for a national meeting. This document represents the executive summary of the final statements approved by the expert panel.

Point prevalence data on antimicrobial usage in Italian acute-care hospitals: Evaluation and comparison of results from two national surveys (2011-2016).

OBJECTIVES AND DESIGN: Data from the Italian national point-prevalence survey (PPS) of healthcare-associated infections (HAIs) were used to evaluate antimicrobial usage (AMU) in Italy and to identify targets for future interventions. METHODS: The second Italian PPS was conducted in 2016 as part of the European PPS initiated by the ECDC. We compared these results with those of the first national survey, conducted in 2011. RESULTS: An overall AMU prevalence of 44.5% (95% CI, 43.7-45.3) was estimated in 2016. No significant change in AMU prevalence was detected when comparing data with the first survey. In both surveys, the most prevalent indication for AMU was the treatment of infections. Considering all indications, penicillins plus ß-lactamase inhibitors (BLIs) were the most commonly prescribed antimicrobial group in 2016; they were used significantly more than in 2011, and piperacillin plus BLI was the most frequently used agent. Broad-spectrum agents accounted for >60% of all antimicrobials for systemic use. No significant increase in the use of carbapenems occurred in 2016. Stable or decreasing carbapenem-resistance levels were identified in this study, although these levels remain alarmingly high for both Klebsiella pneumoniae (50%) and Acinetobacter baumannii (>75%). CONCLUSIONS: These results can be used to identify priorities and targets for interventions that promote more prudent use of antimicrobials, improve healthcare quality and patient safety, and combat the emergence and spread of antimicrobial-resistant pathogens.

[Good practices for the surveillance and control of antimicrobial resistance]. / Buone pratiche per la sorveglianza e il controllo dell'antibiotico-resistenza.

Italy is one of the European Countries with the highest level of antimicrobial consumption, both in the community and in hospital settings, and with the highest prevalence of antimicrobial resistant microorganisms. In 2015, the Project "Good practices for the surveillance and control of antimicrobial resistance" was funded by the Italian National Centre for Disease Prevention and Control (CCM): the aim was to promote integrated actions at national level to control antimicrobial resistance, favouring the transfer of existing good practices. The principal objectives of the project were: to describe the Italian scenario of good practices based on literature review; to improve the capacity of surveillance, through achieving consensus on a core set of indicators, including paediatrics, and through the strengthening of the national surveillance system of antimicrobial resistance coordinated by the Italian National Institute of Health; to define tools useful for priority setting; to evaluate the efficacy of intervention programme aimed at promoting the appropriate use of antibiotics among children for upper respiratory tract infections in the community; to set up training programmes on the prudent use of antibiotics in veterinary medicine. Seven regions were enrolled in the project (Emilia-Romagna with the role of programme coordinator, Campania, Calabria, Lazio, Lombardy, Piedmont, Tuscany) and the Italian National Health Institute. The project allowed to document: the scarce spread of control practices at national level (out of 277 studies reviewed, only 6.1% of the cases were targeted to evaluating the effectiveness of intervention programmes); a significant variability among regions both in relation to antimicrobial consumption and antimicrobial resistance prevalence, with a worrying spread in some regions of several antimicrobial resistant organisms responsible for "critical" infections with great potential health impact; the effectiveness of an intervention aimed at promoting appropriate use of antibiotics in frequent infections for children in the community, such as pharingotonsillitis and acute otitis media (35% reduction of antimicrobial consumption between 2010 and 2017 in Emilia-Romagna; an inversion of the ratio amoxicillin/amoxicillin-clavulanate); the need for new indicators to monitor antimicrobial consumption in hospital paediatric wards and of a new national system for timely identification of new antimicrobial resistance profiles; a positive evaluation of the training programme for veterinary physicians. In conclusion, the project has contributed to identify the most critical areas for antimicrobial resistance control and to select appropriate solutions, potentially transferable to the national level.

Prevalence of healthcare-associated infections, estimated incidence and composite antimicrobial resistance index in acute care hospitals and long-term care facilities: results from two European point prevalence surveys, 2016 to 2017.

Point prevalence surveys of healthcare-associated infections (HAI) and antimicrobial use in the European Union and European Economic Area (EU/EEA) from 2016 to 2017 included 310,755 patients from 1,209 acute care hospitals (ACH) in 28 countries and 117,138 residents from 2,221 long-term care facilities (LTCF) in 23 countries. After national validation, we estimated that 6.5% (cumulative 95% confidence interval (cCI): 5.4-7.8%) patients in ACH and 3.9% (95% cCI: 2.4-6.0%) residents in LTCF had at least one HAI (country-weighted prevalence). On any given day, 98,166 patients (95% cCI: 81,022-117,484) in ACH and 129,940 (95% cCI: 79,570-197,625) residents in LTCF had an HAI. HAI episodes per year were estimated at 8.9 million (95% cCI: 4.6-15.6 million), including 4.5 million (95% cCI: 2.6-7.6 million) in ACH and 4.4 million (95% cCI: 2.0-8.0 million) in LTCF; 3.8 million (95% cCI: 3.1-4.5 million) patients acquired an HAI each year in ACH. Antimicrobial resistance (AMR) to selected AMR markers was 31.6% in ACH and 28.0% in LTCF. Our study confirmed a high annual number of HAI in healthcare facilities in the EU/EEA and indicated that AMR in HAI in LTCF may have reached the same level as in ACH.

Antimicrobial use in European long-term care facilities: results from the third point prevalence survey of healthcare-associated infections and antimicrobial use, 2016 to 2017.

Antimicrobials are commonly prescribed and contribute to the development of antimicrobial resistance in long-term care facilities (LTCFs). In 2010, the European Centre for Disease Prevention and Control initiated point prevalence surveys (PPS) of healthcare-associated infections and antimicrobial use in European LTCFs, performed by external contractors as the Healthcare-Associated infections in Long-Term care facilities (HALT) projects. Here, we investigated prevalence and characteristics of antimicrobial use and antimicrobial stewardship indicators in European LTCFs in 2016-17. Twenty-four European Union/European Economic Area (EU/EEA) countries, the former Yugoslav Republic of Macedonia and Serbia participated in the third PPS in European LTCFs. Overall, 4.9% (95% confidence interval: 4.8-5.1) of LTCF residents in the EU/EEA participating countries received at least one antimicrobial. The most commonly reported Anatomical Therapeutic Chemical (ATC) groups were beta-lactam antibacterials/penicillins (J01C), other antibacterials (J01X) (e.g. glycopeptide antibacterials, polymyxins), quinolones (J01M), sulfonamides and trimethoprim (J01E), and other beta-lactams (J01D). Urinary tract infections and respiratory tract infections were the main indications for antimicrobial prescription. This PPS provides updated and detailed information on antimicrobial use in LTCFs across the EU/EEA that can be used to identify targets for future interventions, follow-up of these interventions and promote prudent use of antimicrobials in European LTCFs.

Multidrug-resistant infections in long-term care facilities: extended-spectrum ß-lactamase-producing Enterobacteriaceae and hypervirulent antibiotic resistant Clostridium difficile.

Infections due to multidrug-resistant (MDR) organisms in long-term care facilities (LTCFs) residents constitute a public health concern. This multicenter study investigated the frequency of ESBL-producing pathogens and MDR Clostridium difficile in clinical specimens from LTCF residents in Italy. During October 2014-March 2015, all urine and diarrheic fecal samples from LTCF residents (≥65 years) with suspected urinary tract infection or C. difficile infection, respectively, received for diagnosis by 4 hospital laboratories located in different cities were analyzed. Antibiotic susceptibility testing, characterization of resistance genes, and molecular typing of pathogens were performed. Of 806 urine cultures collected from 626 residents at 44 different LTCFs, 492 were positive for microbial infection. Of these, 158 were positive for at least an ESBL-producing Enterobacteriaceae species (32.1%), with Escherichia coli as the most frequent ESBL pathogen (23.4%) followed by Klebsiella pneumoniae (4.5%). Furthermore, 4 carbapenemase producers (0.8%) (1 E. coli with VIM-1and 3 K. pneumoniae with KPC-3) were detected. The CTX-M-15 type ESBL predominated in both E. coli (71.3%) and K. pneumoniae (77.3%). Most E. coli isolates (82.6%) belonged to the ST131/H30 clone/subclone. For K. pneumoniae, ST307 and ST15 were frequent (31.8% and 22.7%, respectively), but isolates harboring blaKPC-3 belonged to CC258. Of 136 diarrheic fecal samples collected from 111 residents at 26 different LTCFs, 21 (15.4%) were positive for toxigenic C. difficile; of these, 13 (62%) were MDR (resistant to 3 or more antimicrobial agents of different classes). The predominant C. difficile polymerase chain reaction ribotype was 356/607 (42.9%), followed by 018, 449, and 078 (14% each). Public health efforts are needed to contain the diffusion of CTX-M-producing Enterobacteriaceae and MDR C. difficile in LTCF settings.

Italian field survey reveals a high diffusion of avian metapneumovirus subtype B in layers and weaknesses in the vaccination strategy applied.

The current information on the prevalence of avian metapneumovirus (aMPV) infection in layers is fragmentary and its true impact on egg production often remains unknown or unclear. In order to draw an epidemiologic picture of aMPV presence in layer flocks in Italy, a survey was performed on 19 flocks of pullets and layers based on longitudinal studies or sporadic samplings. aMPV was detected by reverse transcription (RT)-PCR, and blood samples were collected for serology by aMPV ELISA. Occurrences of respiratory signs and a drop in egg production were recorded. Possible involvement of infectious bronchitis (IB) and egg drop syndrome (EDS) viruses that could have caused loss of egg production we ruled out for IB virus by RT-PCR, and EDS virus was ruled out by hemagglutination-inhibition (HI). Only subtype B of aMPV was found in both pullet and layer farms. Surveys of pullets showed that most groups became infected prior to the onset of lay without showing clear respiratory signs. At the point of lay, these groups were serologically positive to aMPV. In two layer flocks, egg drops were observed and could be strongly linked to the presence of aMPV infection. Results were correlated with aMPV vaccination programs applied to the birds in three flocks on the same farm. Only a vaccination program which included two live and one killed vaccines gave complete protection from aMPV infection to the birds, while a single live vaccine application was not efficacious. The current study gives an inside view of field aMPV diffusion in Italy and its control in layers.

A turkey rhinotracheitis outbreak caused by the environmental spread of a vaccine-derived avian metapneumovirus.

Avian metapneumovirus (aMPV) subtype A was isolated from 7-week-old turkeys showing respiratory disease typical of turkey rhinotracheitis. Comparison of the virus sequence with previously determined vaccine marker sequences showed that the virulent virus had originated from a licensed live subtype A aMPV vaccine. The vaccine had neither been in use on the farm within a period of at least 6 months nor had it been used on farms within a distance of approximately 5 km. Isolation of the virus and exposure to naive turkeys caused disease typical of a virulent aMPV field strain. The study shows that disease was caused by exposure to aMPV vaccine-derived virus that was present in the environment, and indicates that such virus is able to circulate for longer than was previously envisaged.

A single polymerase (L) mutation in avian metapneumovirus increased virulence and partially maintained virus viability at an elevated temperature.

Previously, a virulent avian metapneumovirus, farm isolate Italy 309/04, was shown to have been derived from a live vaccine. Virulence due to the five nucleotide mutations associated with the reversion to virulence was investigated by their addition to the genome of the vaccine strain using reverse genetics. Virulence of these recombinant viruses was determined by infection of 1-day-old turkeys. Disease levels resulting from the combined two matrix mutations was indistinguishable from that produced by the recombinant vaccine, whereas the combined three L gene mutations increased disease to a level (P<0.0001) that was indistinguishable from that caused by the revertant Italy 309/04 virus. Testing of the L mutations individually showed that two mutations did not increase virulence, while the third mutation, corresponding to an asparagine to aspartic acid substitution, produced virulence indistinguishable from that caused by Italy 309/04. In contrast to the vaccine, the virulent mutant also showed increased viability at temperatures typical of turkey core tissues. The notion that increased viral virulence resulted from enhanced ability to replicate in tissues away from the cool respiratory tract, cannot be discounted.

Avian metapneumovirus (AMPV) attachment protein involvement in probable virus evolution concurrent with mass live vaccine introduction.

Avian metapneumoviruses detected in Northern Italy between 1987 and 2007 were sequenced in their fusion (F) and attachment (G) genes together with the same genes from isolates collected throughout western European prior to 1994. Fusion protein genes sequences were highly conserved while G protein sequences showed much greater heterogeneity. Phylogenetic studies based on both genes clearly showed that later Italian viruses were significantly different to all earlier virus detections, including early detections from Italy. Furthermore a serine residue in the G proteins and lysine residue in the fusion protein were exclusive to Italian viruses, indicating that later viruses probably arose within the country and the notion that these later viruses evolved from earlier Italian progenitors cannot be discounted. Biocomputing analysis applied to F and G proteins of later Italian viruses predicted that only G contained altered T cell epitopes. It appears likely that Italian field viruses evolved in response to selection pressure from vaccine induced immunity.

Field avian metapneumovirus evolution avoiding vaccine induced immunity.

Live avian metapneumovirus (AMPV) vaccines have largely brought turkey rhinotracheitis (TRT) under control in Europe but unexplained outbreaks still occur. Italian AMPV longitudinal farm studies showed that subtype B AMPVs were frequently detected in turkeys some considerable period after subtype B vaccination. Sequencing showed these to be unrelated to the previously applied vaccine. Sequencing of the entire genome of a typical later isolate showed numerous SH and G protein gene differences when compared to both a 1987 Italian field isolate and the vaccine in common use. Experimental challenge of vaccinated birds with recent virus showed that protection was inferior to that seen after challenge with the earlier 1987 isolate. Field virus had changed in key antigenic regions allowing replication and leading to disease in well vaccinated birds.