Confirmation of presumptive Legionella colonies on culture media according to ISO 11731:2017: Principles, problems and practice

AIMS

The ISO 11731 norm, published in 2017, describes a method to identify and enumerate Legionella based exclusively on the confirmation of presumptive colonies by subculturing them on BCYE and BCYE-cys agar (BCYE agar without L-cysteine).

METHODS AND RESULTS

Despite this recommendation, our laboratory has kept confirming all presumptive Legionella colonies by combining the subculture method with the latex agglutination and polymerase chain reaction (PCR) assays. Here, we show that the ISO 11731:2017 method adequately performs in our laboratory according ISO 13843:2017. We compared the performance of the ISO method in detecting Legionella in typical and atypical colonies (n = 7156) from health care facilities (HCFs) water samples to that of our combined protocol and we found a 2.1% false positive rate (FPR), underscoring the importance of combining agglutination test and PCR with subculture to achieve optimal confirmation. Lastly, we estimated the water system disinfection cost for HCFs (n = 7), that due to false positive results, would displayed Legionella values exceeding the threshold of risk acceptance established by the Italian guidelines.

CONCLUSIONS

Overall, this large-scale study indicates that the ISO 11731:2017 confirmation method is error-prone, leading to significant FPRs and higher costs for HCFs due to remedial actions on their water systems.

Antibody responses to BNT162b2 SARS-CoV-2 mRNA vaccine among healthcare workers and residents of long-term care facilities: A cohort study in Northern Italy

Background and Aims

Long-term care facilities (LTCFs) have been severely impacted by COVID-19, with a disproportionate amount of SARS-CoV-2 infections and related deaths occurring among residents.

Methods

This study is part of an ongoing multicenter, prospective cohort study conducted among healthcare workers (HCWs) and residents of 13 LTCFs in Northern Italy designed to evaluate SARS-CoV-2 specific immunoglobulin class G (IgG) titers before and following vaccination with Pfizer/BNT162b2 SARS-CoV-2 mRNA vaccine (two doses of vaccine, 21 days apart). Serum samples were obtained from participants (t0) before vaccination, and (t1) 2 weeks after and analyzed to determine anti-S1 IgG antibodies.

Results

Five hundred and thirty-four participants were enrolled (404 subjects participated in both blood draws). Seropositivity was 50.19% at t0 and 99% at t1, with a significant difference in IgG titers. A higher proportion of residents were seropositive at t0 compared with HCWs, with significantly higher IgG titers among residents at both t0 and t1. Pre-existing immunity also had a significant effect on postvaccination IgG titers. However, a significant difference in titers at t1 between HCWs and residents considering only participants seropositive at t0 was found, with higher median titers among previously seropositive residents.

Conclusion

Findings of this study provide scientific evidence endorsing the policy of universal vaccination in LTCFs.

Seroprevalence of infection-induced SARS-CoV-2 antibodies among healthcare users of Northern Italy - results from two serosurveys (October-November 2019 - September-October 2021)

Objectives

The objective was to estimate the seroprevalence of SARS-CoV-2 in autumn 2019 (before case zero was identified in Italy) and 2021 among residual sera samples from health care users in the Piedmont region of northwestern Italy.

Methods

Two serosurveys were conducted. Using a semiquantitative method, samples were tested for the presence of immunoglobulin G (IgG) antibodies against the S1 domain of the spike protein. Samples with positive test results from the 2019 survey were independently retested using a multiplex panel to detect IgG antibodies against the receptor binding domain, S1 and S2 domains, and nucleocapsid. Samples with positive test results from the 2021 survey underwent repeat testing with enzyme-linked immunosorbent assay to detect anti-nucleocapsid IgG antibodies. Prevalence rates according to gender and age groups, together with their respective 95% confidence intervals (CIs), were calculated.

Results

Overall, the proportion of samples with positive test results was 2/353 in 2019 and 22/363 in 2021, with an estimated seroprevalence of 0.27% (95% CI 0-1.86) and 6.21% (95% CI 3.9-9.31) in 2019 and 2021 respectively.

Conclusion

Results of this study support the hypothesis that the virus was circulating in Italy as early as autumn 2019. The role of these early cases in broader transmission dynamics remains to be determined.

A New Culture Method for the Detection of Non-Tuberculous Mycobacteria in Water Samples from Heater-Cooler Units and Extracorporeal Membrane Oxygenation Machines

The isolation of non-tuberculous mycobacteria (NTM) from cultures is particularly laborious due to the potential overgrowth of coexisting non-acid fast bacilli. To reduce the overgrowth of these non-mycobacterial organisms, a decontamination step with NaOH or cetylpyridinium chloride is highly recommended before plating the samples on the culture medium. However, due to their toxicity, decontamination solutions tend to decrease NTM recovery from clinical and environmental samples. Here, we tested an alternative method for NTM recovery based on the use of NTM Elite agar, a selective medium that does not require a decontamination step. Using NTM Elite agar, we were able to detect non-tuberculous mycobacteria in 27.7% (30/108) of water samples analyzed. The average time to NTM detection was 18 days, but some strains required longer to grow, perhaps due to the stressful environmental conditions (periodical disinfection of devices). NTM Elite agar's effectiveness in inhibiting background flora was proven by the isolation of NTM from samples with and without background flora, showing no statistically significant differences in detection rates for different total viable counts of background flora (p = 0.4989). In conclusion, our findings indicate that effective NTM recovery from HCU- and ECMO-derived water samples can be achieved via filtration and direct culture of the filters on NTM Elite agar. This simple procedure can speed up laboratory work and provide an improved method, successfully resulting in low contamination and high detection rate, in addition to being less time-consuming. Its sensitivity and lack of a decontamination step make this protocol particularly useful for monitoring the effectiveness of device disinfection in hospital settings, even in the presence of low NTM loads. Reading timeframes should probably be extended to 7 weeks (i.e., well beyond the standard 4 weeks advised by the manufacturer), in order to isolate even the slow-growing mycobacteria. However, an extended incubation period is not necessary for exclusion of M. chimaera contamination of the devices, as M. chimaera isolation times do not generally exceed 3 weeks.

Cross-sectional study of SARS-CoV-2 seropositivity among health-care workers and residents of long-term facilities in Italy, January 2021

Long‐term care facilities (LTCFs) are high‐risk settings for SARS‐CoV‐2 infection. This study aimed to describe SARS‐CoV‐2 seropositivity among residents of LTCFs and health‐care workers (HCWs). Subjects were recruited in January 2021 among unvaccinated HCWs of LTCFs and hospitals and residents of LTCFs in Northern Italy. Information concerning previous SARS‐CoV‐2 infections and a sample of peripheral blood were collected. Anti‐S SARS‐CoV‐2 IgG antibodies were measured using the EUROIMMUN Anti‐SARS‐CoV‐2 QuantiVac ELISA kit (EUROIMMUN Medizinische Labordiagnostika AG). For subjects with previous COVID‐19 infection, gender, age, type of subject (HCW or resident), and time between last positive swab and blood draw were considered as possible determinants of two outcomes: the probability to obtain a positive serological result and antibody titer. Six hundred and fifty‐eight subjects were enrolled. 56.1% of all subjects and 65% of residents presented positive results (overall median antibody titer: 31.0 RU/ml). Multivariable models identified a statistically significant 4% decrease in the estimated antibody level for each 30‐day increase from the last positive swab. HCWs were associated with significant odds for seroreversion over time (OR: 0.926 for every 30 days, 95% CI: 0.860–0.998), contrary to residents (OR: 1.059, 95% CI: 0.919–1.22). Age and gender were not factors predicting seropositivity over time. Residents could have a higher probability of maintaining a seropositive status over time compared to HCWs.

Chemical susceptibility testing of non-tuberculous mycobacterium strains and other aquatic bacteria: Results of a study for the development of a more sensitive and simple method for the detection of NTM in environmental samples

The methods employed to detect non-tuberculous mycobacteria on environmental samples are essentially those classically used in clinical microbiology, which envisage a decontamination step to reduce the overgrowth of non-mycobacterial organisms before plating them on the culture medium. The aim of this study was to propose alternative culture techniques to improve non-tuberculous mycobacteria detection in environmental samples. We used artificially contaminated samples to compare the membrane filter washing procedure against direct plating of membrane filters on culture media in relation to M.chimaera and M.chelonae recovery efficiency. Moreover, we compared the efficacy of NTM Elite agar in inhibiting the growth of aquatic bacteria with that of cetylpyridinium chloride and N-acetyl-L-cysteine sodium hydroxide decontamination treatments. The washing procedure yielded a low release of both mycobacterium strains (6.6% for Mycobacterium chimaera and 7.5% for Mycobacterium chelonae) from the membrane filters; on the contrary, direct plating of membrane filters led to a 100% cell recovery. Water sample pretreatment with N-acetyl-L-cysteine sodium hydroxide (1%), despite achieving complete suppression of non-acid fast bacilli, caused a reduction in mycobacteria growth. Decontamination with cetylpyridinium chloride (0.005%) was found to be ineffective against Methylobacterium spp. and Burkholderia multivorans. NTM Elite agar was ineffective against B. multivorans, but it inhibited the growth of all other aquatic bacteria. Our results indicate that NTM Elite agar provides a valid alternative method of recovering non-tuberculous mycobacteria from environmental samples. It does not involve a decontamination step and provides greater recovery efficiency by skipping the washing step and directly plating the filters on the media.

The use of BCYE medium for the detection of Legionella in environmental water samples: an appropriate update to ISO 11731:2017 standard?

We evaluated the diagnostic performances of 2 media (BCYE, MWY) on 951 Legionella-positive hospital water samples. MWY allowed detecting Legionella in 89.2% of samples, but in 10.8% (103/951) Legionella was found on BCYE plates only. In samples where Legionella was isolated with other microorganisms (663/951), MWY was essential to detect the majority of positive samples (349/663, 52.6%), as fewer plates resulted unreadable; however, in those containing Legionella only, a higher frequency of positive samples was recorded with BCYE (94.8%, 273/288) compared to MWY (85.1%, 245/288). Considering the 484 concordant positive samples, overall Legionella counts were significantly higher on BCYE (P = 0.0029), with 47% of samples showing higher counts on BCYE compared to MWY plates. Furthermore, discordant samples (positive on only one medium) showed different relative proportions between Legionella pneumophila and non-pneumophila, the latter being found more frequently on BCYE only (P = 0.0296).Our findings confirm the appropriateness of the ISO 11731:2017 update.

First assessment of covid-19 vaccine response in a population at risk

Introduction

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of coronavirus disease 2019 (COVID-19), has led to a global pandemic. Currently, the diagnosis of COVID-19 is confirmed by detecting SARS-CoV-2 via RealTime-RT-PCR in rhino-pharyngeal swab. Serological test is required to evaluate a previous exposure to the virus, as well as antibody response. The aim of this multicentric study is to analyse the antibody response following COVID-19 vaccination in healthcare workers and guests of nursing homes, and to determine differences between subjects with or without a confirmed previous infection.

Methods

Our study included 657 subjects, recruited from guests and healthcare workers of nursing homes in the Piedmont region. 10 days after the completion of the vaccination cycle, a blood sample was taken from the subjects to measure IgG against SARS-CoV-2 spike protein. Serological testing was performed using an enzyme immunoassay kit (EUROIMMUN Anti-SARS-CoV-2 QuantiVac ELISA). We performed statistical analysis with R software.

Results

We recruited 657 subjects aged between 19 to 106. Among them, 404 had a previous infection and 253 didn't have a known previous infection. The serological examination resulted positive in 655 subjects and negative in 2 (X¯ IgG 1095 RU/ml). Samples with titer> 1200 RU/ml will be further diluted to identify the titer and differences from the baseline situation.

Conclusions

This study analyses neutralizing antibodies, which should prevent the virus from binding to target cells via spike protein. According to literature, immunological response to vaccine presents a great variability of antibodies level in the study population. However, no significantly correlations were found between the available variables. Preliminary data show the presence of a very intense antibody response after active vaccine immunization both in subjects with previous infection and in the rest of the study population.

Key messages

Covid-19 vaccine response in a population at risk. Differences between subjects with or without a confirmed previous infection.

Preliminary assessment of COVID-19 serological situation in a high-risk cohort

Introduction

Studies on the duration of immune response in subjects with COVID-19 could facilitate understanding of how immunity develops and persists during the natural course of infection, as well as providing epidemiological information useful in public health decisions on the use of vaccines. The study aims to analyse antibody response in a cohort of subjects with high-risk of exposure to SARS-CoV-2 due to the long-term care facility environment.

Methods

We recruited 657 subjects between guests and healthcare workers from Piedmontese nursing homes. IgG directed against the S1 domain of SARS-CoV-2 spike protein were assayed on serum. We used EUROIMMUN kit, which exploits ELISA method. Reference values are (RU/mL): positive ≥ 11; borderline 8 ≤ value < 11; negative < 8.

Results

Among the 657 subjects, we examined 494 health workers and 163 guests. The average age was 56.2. In relation to COVID-19, 402 subjects had a previous infection, 255 had not. About serology: positive 369; negative 261; borderline 27. The mean of the IgG values was 35.68 RU/mL. Swabs/serology: 77.36% with previous infection were positive to serology, 18.66% negative; of all subjects who were always negative to swabs, 72.94% were negative, 22.74% positive. Moreover, the mean time elapsed from positive swab to serology test was 144.08 days.

Conclusions

Preliminary results show that the antibody response is present and persistent in the study population, even a long time after the infection. According to literature, antibody persistence has great variability in our population, as no statistically significant correlations were found between antibody titer and other variables such as time elapsed since infection. The examined sample, belonging to high-risk category (long-term care facilities), is most likely to present repeated exposure to SARS-CoV-2, highlighted by the seropositivity of never infected subjects. These findings might help policy makers better address resources regarding vaccines.

Key messages

Antibody response is present and persistent in the study population, even a long time after the infection. Antibody persistence has great variability in our population, as no statistically significant correlations were found between antibody titer and other variables such as time elapsed since infection.

Pertussis immunisation during pregnancy: Antibody levels and the impact of booster vaccine

Pertussis (whooping cough) is a highly infectious disease caused by Bordetella pertussis. Mothers lacking adequate immunity and contracting the disease represent the biggest risk of transmission to new-borns, for which the disease is often a threat. The aim of the study was to estimate the frequency of pertussis susceptibility among pregnant women, in order to point out the need for a vaccine recall during pregnancy, and to evaluate the antibody response in already vaccinated women. A cross-sectional observational study was conducted in the blood test centre of "St. Anna" Obstetrics and Gynaecology Hospital in Turin (Piedmont, Italy). Eligibility criteria included pregnant women coming to the centre for any blood test, aged 18 or above and with gestational age between 33 and 37 weeks at the moment of the blood draw. The data collection was carried out from May 2019 to January 2020 and the concentration of anti-Pertussis Toxin (anti-PT) IgG was measured through the Enzyme-Linked Immunosorbent Assay (ELISA) technique. Two-hundred women (median age 35) were enrolled: 132 (66%) had received at least one dose of pertussis vaccine, 82 of which during pregnancy. Recently vaccinated women had significantly higher antibody titres (even 12-15 times as high) compared to those vaccinated more than 5 years before or never vaccinated at all (p < 0.0001). Moreover, 95.1% of recently vaccinated women had anti-PT IgG levels above 10 IU/ml, and 85.4% above 20 IU/ml, while the same proportions were as low as 37% and 21% (respectively) in the group of women not vaccinated in pregnancy. This study confirmed that the vaccination is greatly effective in ensuring high antibody titres in the first months after the booster vaccine, with considerable differences in anti-PT IgG compared to women vaccinated earlier or never vaccinated at all, and therefore vaccinating pregnant women against pertussis still represents a valuable strategy.

Comparison of BCYEα+AB agar and MWY agar for detection and enumeration of Legionella spp. in hospital water samples

Background

This study illustrates for the first time the performance (sensitivity and selectivity) of the selective medium BCYEα +AB suggested by the new edition of ISO 11731 for legionella isolation and enumeration. We compared the efficacy of the selective BCYEα +AB medium with that of the highly selective MWY medium.

Results

Legionella spp. was detected in 48.2 and 47.1% of the samples by BCYEα +AB and MWY agar, respectively. For optimal detection of Legionella spp., most protocols recommend using selective media to reduce the number of non-Legionella bacteria. Agreement between the two media was 86.7%.

Conclusions

According to the results, both media have a very similar performance and they both have advantages and disadvantages over each other. In AB medium there is the risk of being less selective so more interfering microbiota may grow but in MWY medium there is the risk of being too selective. The low selectivity of the AB medium could be resolved if other treatments are applied after filtration, e.g. acid and/or heat treatment, but it must be taken into account that these treatments still reduce the number of viable Legionella. In conclusion, we recommend using MWY as a selective medium for the detection of Legionella spp. as it is easier discern suspected colonies and facilitate the final Legionella spp. count.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-021-02109-1.

Real-time PCR, the best approaches for rapid testing for Mycobacterium chimaera detection in heater cooler units and extracorporeal membrane oxygenation

According to recent investigations, the risk of M. chimaera contamination of heater-cooler units (HCUs) has reached global proportions. Our aim was to field evaluate a protocol for early detection of M. chimaera contamination. We assessed the presence of viable M. chimaera in 395 water samples obtained from 48 devices (HCUs and extracorporeal membrane oxygenation) by Real Time PCR. Thirty devices were NTM positive, of which 14 were contaminated with M. chimaera. The most frequently contaminated devices were the Stockert 3T. Noteworthy, Stockert 3T devices were positive for M. chimaera. In conclusion, this study introduces novel PMA-PCR designed to specifically detect M. chimaera in HCUs and ECMO devices; this method can replace the culture method for continuous microbiological surveillance. The timely detection of M. chimaera contamination can then be used to improve effective management of the devices.

Failure to eradicate non-tuberculous mycobacteria upon disinfection of heater-cooler units: results of a microbiological investigation in northwestern Italy

BACKGROUND

Heater-cooler units (HCUs) used during cardiopulmonary bypass may become colonized with non-tuberculous mycobacteria (NTM), including Mycobacterium chimaera. Recently, a worldwide investigation conducted in hospitalized infected patients has detected M. chimaera in several Stockert 3T HCUs manufactured by LivaNova.

AIM

Microbiological surveillance on Stockert 3T (LivaNova) and Maquet HCU40 (Getinge) devices as well as an evaluation of the efficacy of their recommended decontamination protocols.

METHODS

A total of 308 water samples were collected from 29 HCUs: 264 samples were collected from 17 Stockert 3T HCUs and 44 samples from 12 Maquet HCU40 devices. Samples were tested for total viable counts (TVCs) at both 22 and 36°C, Pseudomonas aeruginosa, coliform bacteria, and NTM. The microbiological surveillance began in June 2017 and ran until October 2019.

FINDINGS

A total of 308 HCU water samples were analysed, 65.5% of which yielded NTM. The most frequently colonized device with NTM was the Stockert 3T (88.2%), with a frequency of positive samples of 59.5% (157/264). The Maquet HCU40 devices less frequently yielded NTM (33.3%), with a frequency of positive water samples of 13.6% (6/44). Disinfection procedures were effective in reducing TVCs of bacteria with the exception of NTM species. NTM were detected in both pre-disinfection (50.1%) and post-disinfection (55.7%) samples, and no significant association was found between disinfection and NTM results both in Stockert 3T and Maquet HCU40 devices.

CONCLUSION

This study suggests that manufacturers' procedures for disinfection are ineffective and/or inadequate. Until effective disinfection protocols become available, the only way to minimize the risk of NTM contamination is to closely monitor the water quality in the HCU, keep it as clean as possible, and treat it like any other biohazardous material.

Seroprevalence of anti-pertussis antibodies and immunization status of pregnant women in Turin, 2019

Background

Pertussis is an acute respiratory infection caused by B. pertussis. An acellular vaccine is available, but the protection it confers is estimated to wane after 5 years. Infants under 6 months have the highest risk of complications and mortality. In Italy, the first dose of vaccine is administered in the third month of life and maternal vaccination is recommended in the final weeks of pregnancy. This study aimed to evaluate the seroprevalence of IgG antibodies to pertussis toxin (IgG anti-PT) among pregnant women as a potential source of transplacental transfer of antibodies, which may reduce neonatal risk of disease.

Methods

An observational cross-sectional study was conducted. Two hundred women between the 33rd and 37th weeks of pregnancy were recruited among patients undergoing routine pregnancy check-up at the S.Anna Hospital of Turin, from May to December 2019. Participants were interviewed on their immunization status and a serum sample was collected. Anti-PT levels were assessed using ELISA “NovaLisa B. Pertussis toxin (PT) IgG”. Lacking a correlate of protection, we have distinguished contact with microorganism (10-39 IU/mL), exposure in the previous 2-3 years (40-99 IU/mL), recent infection or immunization &lt;12 months ( &gt; =100 IU/mL).

Results

The median age of participants was 35. Women who had anti-PT titers &gt; =10 IU/mL were 120 (60%) (10-39 IU/mL: 26%, 40-99 IU/mL: 14%, &gt; = 100 IU/mL: 20%). Around 70.5% of women declared previous vaccination (42.5% during pregnancy). Among women vaccinated in the previous 12 months, 7% presented antibodies titer &lt;100 IU/ml. Two women not vaccinated had a titer &gt; 100 IU/ml, indicative of recent pertussis exposure.

Conclusions

This study found 40% of women with antibody titers under cut-off (&lt;10 IU/mL) and 1% prevalence of recent exposure. Despite the late introduction of vaccination against pertussis during pregnancy, a good adherence to the program offered is evident.

Key messages

40% of pregnant women in this study were lacking in antibodies against Pertussis and could not transfer anti-PT to their newborn for early protection. Improving maternal vaccination coverage against pertussis should be a public health priority in Italy; a good adherence to intervention was reported.

Sensitivity and Selectivity of Two Commercially Available Media for Legionella spp. Recovery from Environmental Water Samples

The quality control of culture media used for Legionella spp. isolation and enumeration is paramount to achieve a satisfactory degree of comparability among water testing results from different laboratories. Here, we report on a comparative assessment of the sensitivity and selectivity of MWY and BCYEα media supplied by two different manufacturers (i.e., Xebios Diagnostics GmbH and Oxoid Ltd) for the detection of Legionella spp. from environmental water samples. Even though our analysis showed an excellent agreement between the recovery rates of the four media tested (90.5%), the quantitative recovery of Legionella spp. colonies using Xebios media was significantly greater than that achieved by Oxoid media (P = 0.0054). Furthermore, the sensitivity of detection was significantly higher when samples were plated on MWY ^Xebios agar (P = 0.0442), while the selectivity of MWY appeared to be the same regardless of the manufacturer. Furthermore, MWY^Xebios agar favored the growth of much larger colonies compared to those observed on MWY^Oxoid agar. Finally, MWY^Xebios medium enhanced the recovery of non-pneumophila Legionella species. Collectively, our findings demonstrate that quality control is crucial to ensure high selectivity and sensitivity of the culture media used for the detection and enumeration of Legionella spp. from environmental water resources. As water remediation measures strictly depend on Legionella spp. recovery, culture protocol standardization, as well as quality control of the culture media, is essential to achieve intra- and interlaboratory reproducibility and accuracy.

Using Microbiological Sampling to Evaluate the Efficacy of Nasofibroscope Disinfection: The Tristel Trio Wipes System in Ear-Nose-Throat (ENT) Endoscopy

Disinfection and sterilization are needed for guaranteeing that medical and surgical instruments do not spread contagious microorganisms to patients. The aim of this study was to evaluate the efficacy of a simple manual technique of high-level disinfection (HLD) of flexible fiberoptic nasofibroscopes (FFNs) with wipes impregnated with a chlorine dioxide solution (Tristel Trio Wipes System—TTW) against a conventional automated washer machine (Soluscope ENT, Cimrex 12—AW). FFNs used in 62 patients undergoing endoscopy at an ENT clinic were sampled according to an aseptic procedure. For each nasoendoscopy, microbiological samples were taken at two times: (1) after a patient’s nasoendoscopy and (2) immediately after high-level disinfection. Ten microliters of each prepared sample were inoculated onto specific culture media for the detection of nasopharyngeal flora microorganisms. The microbiological results obtained from 62 post-disinfection samples revealed bacterial growth on two FFNs disinfected with AW, and five FFNs disinfected with TTW, but this difference is not statistically significant. None of the isolates were pathogenic bacteria. Our results are different than the results obtained by two previously published studies on the TTW system. In both studies, sampling was carried out by swabbing the tip and the handle surface of FFNs. This sampling method was the least effective method means of detecting bacteria on a surface. It can be concluded that the two disinfection systems allow providers to obtain a reduction of the saprophytic and pathogenic microbial load.

Reduction of turnaround time for non-tuberculous mycobacteria detection in heater-cooler units by propidium monoazide-real-time polymerase chain reaction

BACKGROUND

Invasive non-tuberculous mycobacteria (NTM) infections are emerging worldwide in patients undergoing open-chest cardiac bypass surgery exposed to contaminated heater-cooler units (HCUs). Although this outbreak has been investigated by culturing bacteria isolated from HCU aerosol and water samples, these conventional methods have low-analytic sensitivity, high rates of sample contamination, and long turnaround time.

AIM

To develop a simple and effective method to detect NTM in HCUs by real-time polymerase chain reaction (PCR), with a short laboratory turnaround time and reliable culture results.

METHODS

A total of 281 water samples collected from various HCUs at seven Italian hospitals were simultaneously screened for NTM by a propidium monoazide (PMA)-PCR assay and by conventional culture testing. The results were analysed with culture testing as the reference method.

FINDINGS

(i) The agreement between culture testing and PMA-PCR was 85.0% with a cycle threshold (C_T) cut-off value of <38 vs 80.0% with a C_T of <43, with a moderate Cohen's κ-coefficient; (ii) the C_T cut-off value of <42 was deemed more suitable for predicting positive specimens; (iii) given the low concentration of target DNA in water samples, the minimum volume to be tested was 1 L.

CONCLUSION

The use of PMA-PCR for fast detection of NTM from environmental samples is highly recommended in order to ascertain whether HCUs may represent a potential source of human exposure to NTM. This reliable and simple method reduces laboratory turnaround time compared to conventional methods (one to two days vs eight weeks, respectively), thereby improving control strategies and effective management of HCUs.

Reduction of turnaround time for non-tuberculous mycobacteria detection in heater-cooler units by propidium monoazide-real-time polymerase chain reaction

BACKGROUND

Invasive non-tuberculous mycobacteria (NTM) infections are emerging worldwide in patients undergoing open-chest cardiac bypass surgery exposed to contaminated heater-cooler units (HCUs). Although this outbreak has been investigated by culturing bacteria isolated from HCU aerosol and water samples, these conventional methods have low-analytic sensitivity, high rates of sample contamination, and long turnaround time.

AIM

To develop a simple and effective method to detect NTM in HCUs by real-time polymerase chain reaction (PCR), with a short laboratory turnaround time and reliable culture results.

METHODS

A total of 281 water samples collected from various HCUs at seven Italian hospitals were simultaneously screened for NTM by a propidium monoazide (PMA)-PCR assay and by conventional culture testing. The results were analysed with culture testing as the reference method.

FINDINGS

(i) The agreement between culture testing and PMA-PCR was 85.0% with a cycle threshold (C_T) cut-off value of <38 vs 80.0% with a C_T of <43, with a moderate Cohen's κ-coefficient; (ii) the C_T cut-off value of <42 was deemed more suitable for predicting positive specimens; (iii) given the low concentration of target DNA in water samples, the minimum volume to be tested was 1 L.

CONCLUSION

The use of PMA-PCR for fast detection of NTM from environmental samples is highly recommended in order to ascertain whether HCUs may represent a potential source of human exposure to NTM. This reliable and simple method reduces laboratory turnaround time compared to conventional methods (one to two days vs eight weeks, respectively), thereby improving control strategies and effective management of HCUs.

Colonization by Pseudomonas aeruginosa of dental unit waterlines and its relationship with other bacteria: suggestions for microbiological monitoring

Pseudomonas aeruginosa is an environmental bacterium, ubiquitous in aquatic habitats and water distribution systems, including dental unit waterlines (DUWLs). We investigated the prevalence of P. aeruginosa in DUWLs from private dental settings. We also analyzed the relationship between P. aeruginosa contamination and the presence of Legionella spp. and total viable count (TVC) in order to suggest a simple and inexpensive protocol to test the quality of water from DUWLs. We detected and quantified P. aeruginosa both by culture and by a PMA (propidium monoazide)-qPCR method. Overall, we detected P. aeruginosa in 17 samples using the PMA-qPCR and in 11 samples using the culture. All culture-positive samples were positive with the PMA-qPCR too, with an agreement between the two methods of 93% and a Cohen's kappa coefficient of κ = 0.747 (good concordance). Comparing results with results of our previous study, we noted that (a) P. aeruginosa was isolated only from DUWLs with high TVC and (b) five out of six Legionella-positive samples were negative for Pseudomonas spp. Our final suggestion is that the cleanliness of DUWLs should be assessed by TVC because it is a good indicator of the presence of pathogens such as Legionella spp. and P. aeruginosa.

"Guidelines for the prevention and control of legionnaire's disease in Italy": guidelines or guidance?

The creation of guidelines is a methodologically complex activity that requires technical expertise, resources and time. Methods of guideline production must meet at least these three criteria: multidisciplinarity, systematic review, and ranked recommendations. In May 2015, the new "Guidelines for the prevention and control of Legionnaire's disease" were published on the website of the Italian Ministry of Health in order to "gather, update and integrate in a single document all the previous national recommendations published". The critical review of the document has led us to conclude that this document does not comply with these three criteria, and we emphasize that guidelines should make decision-making easier, considering the various scientific approaches to a health problem and choosing the one considered most effective. Therefore, the persons responsible for the development of guidelines should strive to widely adopt and use current standards for the development of guidelines as a means to improve patient care and health outcomes.

Experimental Study to Develop a Method for Improving Sample Collection to Monitor Laryngoscopes after Reprocessing

BACKGROUND/AIMS

The microbiological surveillance of endoscopes and automated flexible endoscope reprocessing have been proven to be two of the most difficult and controversial areas of infection control in endoscopy. The purpose of this study was to standardize a sampling method for assessing the effectiveness of standard reprocessing operating procedures for flexible fiberoptic laryngoscopes (FFLs).

METHODS

First, the sampling devices were directly inoculated with Bacillus atrophaeus spores; second, tissue non tissue (TNT) wipes were tested on artificially contaminated surfaces and on FFLs.

RESULTS

Comparison of the sponges, cellulose, and TNT wipes indicated that the TNT wipes were more effective in releasing spores (93%) than the sponges (49%) and cellulose wipes (52%). The developed protocol provides a high efficiency for both collection and extraction from the stainless steel surface (87% of the spores were removed and released) and from the FFL (85% of the spores were removed and released), with relatively low standard deviations for recovery efficiency, particularly for the analysis of the FFL.

CONCLUSION

TNT wipes are more efficient for sampling surface areas, thereby aiding in the accuracy and reproducibility of environmental surveillance.

The role of chemical products at low doses in preventing the proliferation of bacteria in dental unit waterlines: the ICX® experience

In this study we evaluated (1) the efficacy of a protocol that combines hydrogen peroxide (shock treatment) and ICX^® tablets (continuous treatment) for the control of microbial contamination in dental unit water lines, and (2) the in vitro antimicrobial activity of ICX^® tablets on collection and wild strains isolated from dental chair output waters. To assess the treatment effectiveness, the microbial load in the output water samples of three dental chairs were investigated: one control chair received only shock treatment. In vitro bactericidal activity was tested against Staphylococcus aureus and Pseudomonas aeruginosa. Data obtained from samples collected from chairs treated with ICX^® and shock treatment and data from the control chair did not differ significantly on the basis of microbial load. In the in vitro study, the product was unable to kill Gram-negative bacteria. These results show that the continuous introduction of ICX^® was not effective in maintaining low counts of the heterotrophic bacteria in the output water of dental devices, and shock treatment may be needed more frequently than monthly.

Efficacy of a Low Dose of Hydrogen Peroxide (Peroxy Ag⁺) for Continuous Treatment of Dental Unit Water Lines: Challenge Test with Legionella pneumophila Serogroup 1 in a Simulated Dental Unit Waterline

This study was designed to examine the in vitro bactericidal activity of hydrogen peroxide against Legionella. We tested hydrogen peroxide (Peroxy Ag⁺) at 600 ppm to evaluate Legionella survival in a simulated dental treatment water system equipped with Water Hygienization Equipment (W.H.E.) device that was artificially contaminated. When Legionella pneumophila serogroup (sg) 1 was exposed to Peroxy Ag⁺ for 60 min we obtained a two decimal log reduction. High antimicrobial efficacy was obtained with extended periods of exposure: four decimal log reduction at 75 min and five decimal log reduction at 15 h of exposure. Involving a simulation device (Peroxy Ag⁺ is flushed into the simulation dental unit waterlines (DUWL)) we obtained an average reduction of 85% of Legionella load. The product is effective in reducing the number of Legionella cells after 75 min of contact time (99.997%) in the simulator device under test conditions. The Peroxy Ag⁺ treatment is safe for continuous use in the dental water supply system (i.e., it is safe for patient contact), so it could be used as a preventive option, and it may be useful in long-term treatments, alone or coupled with a daily or periodic shock treatment.

Peracetic Acid in the Disinfection of a Hospital Water System Contaminated With Legionella Species

Objective:

To assess the efficacy of an alternative disinfection method for hospital water distribution systems contaminated with Legionella.

Methods:

Disinfection with peracetic acid was performed in a small hospital contaminated with L. pneumophila serotype 1. The disinfectant was used at concentrations of 50 ppm (first three surveillance phases) and 1,000 ppm (fourth surveillance phase) for 30 minutes.

Results:

Environmental monitoring revealed that disinfection was maintained 1 week after treatment; however, levels of recontamination surpassing baseline values were detected after approximately 1 month. Comparison of water temperatures measured at the distal outlets showed a statistically significant association between temperature and bacterial load. The circulating water temperature was found to be lower in the two wards farthest away from the hot water production plant than in other wards. It was thought that the lower water temperature in the two wards promoted the bacterial growth even after disinfection.

Conclusion:

Peracetic acid may be useful in emergency situations, but does not provide definitive protection even if used monthly.

Overestimation of the Legionella spp. load in environmental samples by quantitative real-time PCR: pretreatment with propidium monoazide as a tool for the assessment of an association between Legionella concentration and sanitary risk

Quantitative polymerase chain reaction (qPCR) offers rapid, sensitive, and specific detection of Legionella in environmental water samples. In this study, qPCR and qPCR combined with propidium monoazide (PMA-qPCR) were both applied to hot-water system samples and compared to traditional culture techniques. In addition, we evaluated the ability of PMA-qPCR to monitor the efficacy of different disinfection strategies. Comparison between the quantification obtained by culture and by qPCR or PMA-qPCR on environmental water samples confirms that the concentration of Legionella estimated by GU/L is generally higher than that estimated in CFU/L. Our results on 57 hot-water-system samples collected from 3 different sites show that: i) qPCR results were on average 178-fold higher than the culture results (Δ log10=2.25), ii) PMA-qPCR results were on average 27-fold higher than the culture results (Δ log10=1.43), iii) propidium monoazide-induced signal reduction in qPCR were nearly 10-fold (Δ log10=0.95), and that iv) different degrees of correlations between the 3 methods might be explained by different matrix properties, but also by different disinfection methods affecting cultivability of Legionella. In our study, we calculated the logarithmic differences between the results obtained by PMA-qPCR and those obtained by culture, and we suggested an algorithm for the interpretation of PMA-qPCR results for the routine monitoring of healthcare water systems using a commercial qPCR system (iQ-check real-time PCR kit; Bio-Rad, Marnes-la-Coquette, France).

Virulence of Legionella pneumophila strains isolated from hospital water system and healthcare-associated Legionnaires' disease in Northern Italy between 2004 and 2009

BACKGROUND

Worldwide, L. pneumophila sg 1 is the most common agent of Legionnaires' disease ( 80 to 90% of the reported cases). In contrast, L. pneumophila sg 2-14 account for only 15 to 20% of community-acquired cases, although they account for over 50% of the environmental isolates. The discrepancy between environmental isolates and clinical cases of disease suggested that there are differences in virulence.We decided to subtype the environmental Legionella strains isolated from health care facilities (HCFs) and to compare the distribution of strains with the occurrence of hospital-acquired legionellosis.

METHODS

Observational ecological study based on the data provided by the regional surveillance of legionellosis and on data obtained from hospitals environmental monitoring.Using the monoclonal antibody MAb 3/1 of the Dresden Panel we collected and typed environmental strains of L. pneumophila sg 1 obtained during routine testing in 56 health care facilities from 2004 to 2009.The results of the laboratory analyses of the environmental samples were compared with the number of cases that each health care facility reported during the study period.

RESULTS

The association between the type of colonisation (L. pneumophila sg 1 vs others serogroups) and the incidence of reported cases was statistically significant (p = 0.03 according to the χ2 test).Legionella strains with the virulence-associated epitope recognised by MAb 3/1 were isolated in 8 of the 26 HCFs colonised by L. pneumophila sg 1; 7 of the HCFs colonised by MAb 3/1-positive strains accounted for 85% of the cases of hospital-acquired legionellosis reported during the 6-year study period. There was a statistically significant association (p = 0.003) between the presence of cases and colonisation by MAb 3/1-positive Legionella strains.

CONCLUSION

This study suggests that hospitals colonised by more virulent strains should be aware of the increased risk and consider the opportunities of increase their monitoring efforts and implement more effective contamination control strategies.

Recovery of Legionella species from water samples using an internal method based on ISO 11731: suggestions for revision and implementation

The study aim was to determine retrospectively whether the parallel use of 2 media [buffered charcoal yeast extract (BCYE) and medium of Wadowsky and Yee (MWY)] to isolate Legionella spp. from water samples taken from hospital water supply systems increased the sensitivity of the culture method as compared with methods/protocols in which only seeding on a selective medium is used. We analyzed the results obtained from 931 positive water samples. In 484 of the 931 positive water samples, Legionella spp. was isolated in the presence of other microorganisms; in 83% (400/484), we used MWY to count suspected colonies, which gave a lower number of unreadable plates. In the 447 samples containing only Legionella spp., the highest frequency of positive samples (93%, 418/447) was obtained with BCYE, whereas seeding on MWY yielded 78% (348/447) (P < 0.001). Evaluation of the influence of the media on the Legionella spp. counts obtained by the 2 media showed that BCYE agar produced significantly higher counts than MWY (P < 0.001). The major conclusions that may be drawn from our data are as follows: 1) BCYE gives a high recovery rate of positive samples (93%) and a much greater yield of Legionella spp. than MWY; 2) BCYE was necessary for the detection of non-L. pneumophila spp. which grew poorly on selective media; 3) selective media [MWY or GVPC (glycine, vancomycin, polymyxin B, and cycloheximide)] were necessary for the recovery of Legionella spp. when the non-selective medium (BCYE) was difficult to interpret because of contaminating background flora. The use of different media is recommended for routine water tests in hospitals.

Effective environmental sampling strategies for monitoring Legionella spp contamination in hot water systems

BACKGROUND

The prevention and control of legionellosis in hospital settings involves environmental sampling, among other measures. The data yielded by sampling constitute an important means of risk assessment and provide a valid basis on which to plan remedial (cleansing and disinfection) and preventive (maintenance) interventions. This retrospective study had 2 objectives: (1) to evaluate the utility of biofilm sampling at distal sites and (2) to identify an efficient environmental sampling strategy.

METHODS

Samples of hot water and biofilm were collected between June 1999 and March 2008 from 41 hospitals in Italy's Piemonte region. We analyzed results of the samples (water and biofilm) taken from the same site and results of the water samples taken from the recirculation loop and water samples taken from the distal sites during the same sampling run.

RESULTS

Microbiological analysis was performed on 3910 pairs of samples (water/biofilm). In 81% of the pairs, the results were concordant; in 17% of the pairs, Legionella was isolated only from the water samples, and in only 2% of the pairs was Legionella isolated from the biofilm sample alone. Data from 299 sampling runs show that 79% (236) of results from the water samples taken from the recirculation loop and water samples taken from the distal sites during the same sampling run were concordant, and 21% (63) were discordant.

CONCLUSIONS

Our findings suggest that hospitals could safely adopt a simpler (water sampling only without biofilm sampling) and more efficient (monitoring of the entire system through sampling of recirculation loop water) environmental sampling policy.

Prevalence of anti-legionella antibodies among Italian hospital workers

This study evaluated the prevalence of anti-legionella antibodies in workers at hospitals with a long-term history of legionella contamination. The hospitals are located in Milan and Turin, northern Italy, and in Naples and Bari, southern Italy. Antibody prevalence and titres of healthcare workers, medical and dental students and blood donors were assessed. In total 28.5% of subjects were antibody positive, most frequently to L. pneumophila serogroups 7-14. Major differences were observed in seroprevalence and type of legionella antibody in persons from different geographic areas. Healthcare workers had a significantly higher frequency of antibodies compared with blood donors in Milan (35.4 vs 15.9%, P<0.001), whereas in Naples both groups exhibited high antibody frequency (48.8 vs 44.0%) and had a higher proportion of antibodies to legionella serogroups 1-6. Dental workers had a higher seroprevalence than office staff in Bari, but not in Turin, where daily disinfecting procedures had been adopted to avoid contamination of dental unit water. No association was found between the presence of antibodies and the presence of risk factors for legionellosis, nor with the occurrence of pneumonia and/or flu-like symptoms. In conclusion, the presence of legionella antibodies may be associated with occupational exposure in the hospital environment, but there was no evidence of any association with disease.

Use of IgG Avidity test in case definitions of toxoplasmosis in pregnancy

A survey network for congenital toxoplasmosis (TOXO-NET) was set up in December 1996 in Piedmont (Italy). Participants were asked to classify the infections in pregnant mothers and newborns by the criteria of the European Network on Congenital Toxoplasmosis published by Lebech in 1996. Because the IgG Avidity test is largely employed as a 2nd level test in toxoplasmosis diagnosis and it could be helpful to date infection, the co-ordinators of TOXO-NET suggested including it in the "case definition" of "probable" infection and "unlikely" infection. 117 cases of toxoplasmosis in pregnancy divided into the risk categories under Lebech's criteria were re-examined using the "new" case definitions. 77 out of 117 (65.8%) Toxoplasma gondii infections during pregnancy could be defined with only one serum sample using the IgG Avidity test. The IgG Avidity test proved a useful method to classify the Toxoplasma gondii infections in pregnancy, especially when we had only one serum sample.