In vitro activity of antimicrobial agents against Legionella isolated from environmental water systems: first results from Turkey

Tenets of a holistic approach to drinking water-associated pathogen research, management, and communication

In recent years, drinking water-associated pathogens that can cause infections in immunocompromised or otherwise susceptible individuals (henceforth referred to as DWPI), sometimes referred to as opportunistic pathogens or opportunistic premise plumbing pathogens, have received considerable attention. DWPI research has largely been conducted by experts focusing on specific microorganisms or within silos of expertise. The resulting mitigation approaches optimized for a single microorganism may have unintended consequences and trade-offs for other DWPI or other interests (e.g., energy costs and conservation). For example, the ecological and epidemiological issues characteristic of Legionella pneumophila diverge from those relevant for Mycobacterium avium and other nontuberculous mycobacteria. Recent advances in understanding DWPI as part of a complex microbial ecosystem inhabiting drinking water systems continues to reveal additional challenges: namely, how can all microorganisms of concern be managed simultaneously? In order to protect public health, we must take a more holistic approach in all aspects of the field, including basic research, monitoring methods, risk-based mitigation techniques, and policy. A holistic approach will (i) target multiple microorganisms simultaneously, (ii) involve experts across several disciplines, and (iii) communicate results across disciplines and more broadly, proactively addressing source water-to-customer system management.

Water as a Source of Antimicrobial Resistance and Healthcare-Associated Infections

Healthcare-associated infections (HAIs) are one of the most common patient complications, affecting 7% of patients in developed countries each year. The rise of antimicrobial resistant (AMR) bacteria has been identified as one of the biggest global health challenges, resulting in an estimated 23,000 deaths in the US annually. Environmental reservoirs for AMR bacteria such as bed rails, light switches and doorknobs have been identified in the past and addressed with infection prevention guidelines. However, water and water-related devices are often overlooked as potential sources of HAI outbreaks. This systematic review examines the role of water and water-related devices in the transmission of AMR bacteria responsible for HAIs, discussing common waterborne devices, pathogens, and surveillance strategies. AMR strains of previously described waterborne pathogens including Pseudomonas aeruginosa, Mycobacterium spp., and Legionella spp. were commonly isolated. However, methicillin-resistant Staphylococcus aureus and carbapenem-resistant Enterobacteriaceae that are not typically associated with water were also isolated. Biofilms were identified as a hot spot for the dissemination of genes responsible for survival functions. A limitation identified was a lack of consistency between environmental screening scope, isolation methodology, and antimicrobial resistance characterization. Broad universal environmental surveillance guidelines must be developed and adopted to monitor AMR pathogens, allowing prediction of future threats before waterborne infection outbreaks occur.

Antibiotic Resistance of Legionella pneumophila in Clinical and Water Isolates-A Systematic Review

The current systematic review investigates the antibiotic susceptibility pattern of Legionella pneumophila isolates from the 1980s to the present day, deriving data from clinical and/or water samples from studies carried out all over the world. Eighty-nine papers meeting the inclusion criteria, i.e., “Legionella pneumophila” and “resistance to antibiotics”, were evaluated according to pre-defined validity criteria. Sixty articles referred to clinical isolates, and 18 articles reported water-related L. pneumophila isolates, while 11 articles included both clinical and water isolates. Several methods have been proposed as suitable for the determination of MICs, such as the E-test, broth and agar dilution, and disk diffusion methods, in vivo and in vitro, using various media. The E-test method proposed by the European Society of Clinical Microbiology and Infectious Diseases (EUCAST) seems to be the second most frequently used method overall, but it is the preferred method in the most recent publications (2000–2019) for the interpretation criteria. Erythromycin has been proved to be the preference for resistance testing over the years. However, in the last 19 years, the antibiotics ciprofloxacin (CIP), erythromycin (ERM), levofloxacin (LEV) and azithromycin (AZM) were the ones that saw an increase in their use. A decrease in the sensitivity to antibiotics was identified in approximately half of the reviewed articles.

Antimicrobial Susceptibility Patterns of Legionella spp. Strains Isolated from Water Systems in Morocco

Objective: Legionella is a waterborne pathogen that causes a severe form of pneumonia called Legionnaires' diseases, which is normally acquired by inhalation of aerosols containing Legionella originating from natural and man-made water systems. The aim of this study was to describe the level of antimicrobial susceptibility of environmental Legionella spp. strains to preferred and recommended therapeutic agents to treat Legionella disease. Methods: The minimum inhibitory concentrations (MICs) of 60 environmental Legionella spp. strains were tested using the broth dilution method. Susceptibility testing was performed for 12 antimicrobial agents: macrolides (erythromycin, azithromycin [AZI], and clarithromycin [CLA]), fluoroquinolones (ciprofloxacin, levofloxacin, moxifloxacin, and gemifloxacin), a ketolide (telithromycin), cefotaxime (CEF), tigecycline (TIG), doxycycline (DOX), and rifampicin (RIF). Results: All tested strains of Legionella spp. were inhibited by low concentrations of fluoroquinolones and macrolides. Regarding the macrolides, CLA was the most active antibiotic, and AZI was the least active. RIF was the most effective antibiotic against the isolates in vitro. All isolates were inhibited by the following antibiotics (in decreasing order of their MICs): DOX>CEF>TIG. Conclusions: No resistance against these drugs was detected, and all isolates were inhibited by low concentrations of the tested antibiotics. Susceptibility testing of environmental Legionella spp. isolates must be monitored often to detect and evaluate the possible development of antibiotic resistance.

Environmental surveillance and in vitro activity of antimicrobial agents against Legionella pneumophila isolated from hospital water systems in Campania, South Italy: a 5-year study

BACKGROUND

Legionellosis' treatment failures have been recently reported showing the possibility of resistance development to traditional therapy, especially in healthcare related disease cases. Environmental impact of antibiotic residues, especially in hospital waters, may act on the resistome of Legionella resulting in developing resistance mechanisms.

OBJECTIVES

In this study we investigate the antibiotic susceptibility of environmental Legionella pneumophila (Lpn) strains isolated from hospital water systems in Campania, a region located in Southwest Italy.

METHODS

5321 hospital water samples were investigated for the presence of Lpn. Among positive samples, antibiotic susceptibility was tested for a random subset of 125 Lpn strains (25 Lpn isolates from each of the following serogroups: 1, 3, 5, 6, 8). Susceptibility testing was performed, using the E-test on buffered charcoal yeast extract agar supplemented with α-ketoglutarate, for 10 antimicrobial drugs: azithromycin, cefotaxime, clarithromycin, doxycycline, erythromycin, rifampicin, tigecycline, ciprofloxacin, levofloxacin and moxifloxacin. Non parametric tests were used to determine and assess the significant differences in susceptibility to the different antimicrobics between the serogroups.

RESULTS

Among the isolated strains, none showed resistance to the antibiotics tested. Rifampicin was the most active antibiotic against overall Legionella strains, followed by levofloxacin. Between the macrolides the clarithromycin was overall the most active drug, instead the azithromycin was the less active. Analyzing the different serogroups a significant difference was found between serogroup 1 and non-1 serogroup isolates for doxycycline and tigecycline.

CONCLUSIONS

Antibiotic susceptibility of environmental isolates of Legionella spp. might be useful for the early detection of resistance to antibiotics that directly impacts on mortality and length of hospital stay.

Antibiotic susceptibility of Legionella strains isolated from public water sources in Macau and Guangzhou

The purpose of this study was to investigate the susceptibility of waterborne strains of Legionella to eight antimicrobials commonly used in legionellosis therapy. The minimum inhibitory concentrations (MICs) of 66 environmental Legionella strains, isolated from fountains and cooling towers of public facilities (hotels, schools, and shopping malls) in Macau and Guangzhou, were tested using the microdilution method in buffered yeast extract broth. The MIC₅₀/MIC₉₀ values for erythromycin, cefotaxime (CTX), doxycycline (DOC), minocycline (MIN), azithromycin, ciprofloxacin, levofloxacin (LEV), and moxifloxacin were 0.125/0.5 mg/L, 4/8 mg/L, 8/16 mg/L, 4/8 mg/L, 0.125/0.5 mg/L, 0.031/0.031 mg/L, 0.031/0.031 mg/L, and 0.031/0.062 mg/L, respectively. Legionella isolates were inhibited by either low concentrations of macrolides and fluoroquinolones, or high concentrations of CTX and tetracycline drugs. LEV was the most effective drug against different Legionella species and serogroups of L. pneumophila isolates. The latter were inhibited in decreasing order by MIN > CTX >DOC, while non-L. pneumophila isolates were inhibited by CTX> MIN >DOC. In this study, we evaluated drug resistance of pathogenic bacteria from the environment. This may help predict the emergence of drug resistance, improve patient outcomes, and reduce hospitalization costs.

Legionnaires' disease

Since first identified in early 1977, bacteria of the genus Legionella are recognised as a common cause of community-acquired pneumonia and a rare cause of hospital-acquired pneumonia. Legionella bacteria multisystem manifestations mainly affect susceptible patients as a result of age, underlying debilitating conditions, or immunosuppression. Water is the major natural reservoir for Legionella, and the pathogen is found in many different natural and artificial aquatic environments such as cooling towers or water systems in buildings, including hospitals. The term given to the severe pneumonia and systemic infection caused by Legionella bacteria is Legionnaires' disease. Over time, the prevalence of legionellosis or Legionnaires' disease has risen, which might indicate a greater awareness and reporting of the disease. Advances in microbiology have led to a better understanding of the ecological niches and pathogenesis of the condition. Legionnaires' disease is not always suspected because of its non-specific symptoms, and the diagnostic tests routinely available do not offer the desired sensitivity. However, effective antibiotics are available. Disease notification systems provide the basis for initiating investigations and limiting the scale and recurrence of outbreaks. This report reviews our current understanding of this disease.

Antibiotic susceptibility of Legionella pneumophila strains isolated from hospital water systems in Southern Italy

OBJECTIVES

The purpose of this study was to describe the susceptibility of environmental strains of Legionella spp. to 10 antimicrobials commonly used for legionellosis therapy. A study of environmental strains could be useful to timely predict the onset of antibiotic resistance in the environment before it is evidenced in clinical specimens.

METHODS

The minimum inhibitory concentrations (MICs) of 100 environmental Legionella pneumophila (Lpn) strains belonging to serogroups (sgs) 1, 6, 8, and 10 were tested using the E-test methodology on buffered charcoal yeast extract agar supplemented with α-ketoglutarate. The most frequent sgs were selected from those obtained during microbiological surveillance conducted in 2014 in a hospital in Southern Italy. The MICs were read after 2 days of incubation at 35 °C in a humidified atmosphere without CO2.

RESULTS

All isolates were inhibited by low concentrations of fluoroquinolones and macrolides. Rifampicin was the most active drug against the isolates in vitro. All Lpn isolates were inhibited by the following drugs (in decreasing order of their MICs): doxycycline>tigecycline>cefotaxime. The MICs of azithromycin, ciprofloxacin, levofloxacin, moxifloxacin, and tigecycline were significantly lower for Lpn non-sg 1 than Lpn sg 1 isolates.

CONCLUSIONS

Susceptibility testing of Legionella strains to appropriate antibiotics should be performed often to evaluate the possible emergence of resistance, to improve the outcomes of patients, and to reduce the direct costs associated with hospitalization.

Systematic screening of common wastewater-marking pharmaceuticals in urban aquatic environments: implications for environmental risk control

In this report, we refer to pharmaceuticals that are widespread in the urban aquatic environment and that mainly originate from wastewater treatment plants or non-point source sewage as "wastewater-marking pharmaceuticals" (WWMPs). To some extent, they reflect the condition or trend of water contamination and also contribute to aquatic environmental risk assessment. The method reported here for screening typical WWMPs was proposed based on academic concerns about them and their concentrations present in the urban aquatic environment, as well as their properties of accumulation, persistence, eco-toxicity and related environmental risks caused by them. The screening system consisted of an initial screening system and a further screening system. In the former, pharmaceuticals were categorised into different evaluation levels, and in the latter, each pharmaceutical was given a normalised final evaluation score, which was the sum of every score for its properties of accumulation, persistence, eco-toxicity and environmental risk in the aquatic environment. The system was applied to 126 pharmaceuticals frequently detected in the aquatic environment. In the initial screening procedure, five pharmaceuticals were classified into the "high" category, 16 pharmaceuticals into the "medium" category, 15 pharmaceuticals into the "low" category and 90 pharmaceuticals into the "very low" category. Subsequently, further screening were conducted on 36 pharmaceuticals considered as being of "high", "medium" and "low" categories in the former system. We identified 7 pharmaceuticals with final evaluation scores of 1-10, 10 pharmaceuticals with scores of 11-15, 15 pharmaceuticals with scores from 16 to 20 and 4 pharmaceuticals with scores above 21. The results showed that this screening system could contribute to the effective selection of target WWMPs, which would be important for spatial-temporal dynamics, transference and pollution control of pharmaceuticals in the urban aquatic environment. However, there remains a number of pharmaceutical parameters with measured data gaps, such as organic carbon adsorption coefficients and bioconcentration factors, which, if filled, would improve the accuracy of the screening system.