Rising Legionella Infections and Its Prevention in Industrial

Cooling Towers

Although Legionella is found naturally in freshwater environments, it becomes a health concern to the population when it becomes established in building water systems including showerheads, sink faucets, hot tubs, decorative fountains, hot water tanks, heaters, and cooling towers.(1) An industrial cooling tower is a critical component of many refrigeration systems and can be found in industries such as power plants, chemical processing, steel mills, and many manufacturing companies where process cooling is necessary. Also, a commercial cooling tower can be used to provide comfort-cooling for large commercial buildings like airports, schools, hospitals (shown in the photo above), or hotels. If not properly sanitized and monitored, these systems, having substantial amounts of water, can be an ideal habitat for Legionella, a heat-loving organism.(2) Cooling towers take warm water generated during an industrial process, and spray it through nozzles to maximize its contact with cool outside air.(3,4) This process creates a heat exchange, where some water evaporates and dissipates from the top of the tower. Aerosolized water can then spread over miles and carry Legionella along the way, if present.(4)

Individuals inhaling aerosolized water contaminated with Legionella can develop legionellosis, a disease consisting of three distinct clinical and epidemiological illnesses: Legionnaires’ disease, Pontiac fever, and extrapulmonary legionellosis. Legionnaires’ disease is a serious type of pneumonia. Pontiac fever is a milder infection that rarely requires antibiotic treatment. Extrapulmonary legionellosis is associated with endocarditis and wound, joint, and graft infections.(5)

Legionnaires’ disease is a common cause of community-acquired pneumonia that usually requires hospitalization. According to the CDC, Legionnaires’ disease cases have been on the rise since 2000 with close to 10,000 reports in the United States in 2018 (see the graph below).(6) Graham et al. conducted a systematic review and meta-analysis to determine the mean percentage where Legionella is the causative agent for community-acquired pneumonia and its incidence rate. This investigation reviewed 2,778 global studies and included 219 in the meta analysis. The mean proportion of Legionella as the causative agent for community-acquired pneumonia was 4.6% (95% CI: 4.4 - 4.7) and the mean incidence rate was 2.8 per 100,000 population (95% CI: 2.7 - 2.9).(7)

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Almost 5% of all pneumonias are caused by Legionella

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Therefore, controlling Legionella in cooling towers is of considerable importance to prevent outbreaks. The design, operation, maintenance, control limits, and remediation protocols should be taken into consideration to ensure public safety. Locating these cooling towers at least 25 feet from building air intake ducts can prevent aerosolized water from being drawn into a ventilation system. Also, understanding cooling tower design components, using high-efficiency drift eliminators to capture large water droplets in the cooling tower air stream, avoiding water stagnation in the system, recirculating water during intermittent operation, and designing and installing an automated water treatment system can avert bacterial growth. Lastly, when an outbreak or illness is confirmed, taking the necessary cleaning, disinfecting, and remediation steps while working with the corresponding public health authority can prevent the increase in legionellosis cases.(8) 

Hardy offers a complete line of culture media designed to detect Legionella for the purpose of monitoring potentially dangerous cooling towers.

References: 1, 2, 3, 4, 5, 6, 7, 8

by Elide Herrera

The Rising Antimicrobial Resistance

in Fido and Fifi

Antimicrobial resistance (AMR) is one of the top ten global public health threats facing humanity.¹ Ironically, humans are to blame; yet, in recent years, the increase of AMR strains in animals, specifically companion animals, has also risen. Today, leading animal veterinarian organizations are calling on veterinarians, producers, breeders and pet owners to help in the fight against AMR in animals. Furthermore, in its 2020 report, the American Veterinary Medical Association Committee on Antimicrobials raises awareness on the threat of antimicrobial resistance affecting animal health and encourages action to address the threat.²

Consequently, several studies have found carbapenem-resistant Enterobacterales (CRE) in pets, including dogs and cats, as well as in veterinary hospital settings. A study published in the Journal of Antimicrobial Chemotherapy in 2017 found 8% of dogs and cats tested in veterinary clinics in the United States were infected or carriers of CRE strains. Another study published in the same journal in 2019 found 1.6% of dogs and cats tested in the Netherlands had CRE. Not surprisingly, there is concern pets with CRE infections may spread these bacteria to humans, because of the ways in which we share our homes and lives with companion animals.³

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8% of US dogs and cats have CRE!

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Another study showed humans and companion animals readily exchange methicillin-resistant Staphylococcus aureus (MRSA); sharing is not unidirectional, but flows back and forth between pets and humans.⁴ There is also evidence to suggest Candida, a type of yeast, may be increasing in pets in recent years. Several factors may contribute to an increase in Candida in pets. These include changes in diet, increased use of antimicrobials and other medications which may compromise an animal’s natural microbiota, and increased exposure to environmental toxins.

More research and surveillance are needed to capture the prevalence of potentially antimicrobial resistant pathogens in companion pets. This is especially critical considering the use of therapy animals which may visit hospitals, nursing homes, or patient care centers where immunocompromised patients reside. Measures to reduce unnecessary or misused antimicrobial therapy in pets may help reduce the incidence of antimicrobial resistance. This could include establishing infection prevention programs and developing antimicrobial stewardships plans in veterinary settings. In the meantime, veterinarians can reduce the potential for antimicrobial resistance by prescribing antimicrobials only when necessary; implementing infection prevention and antimicrobial stewardships programs in veterinary settings; and using diagnostic testing to guide treatment decisions.

Another source of resistant organisms is in uncooked raw pet food. A study done in Portugal found that all of the 25 brands tested were contaminated with antibiotic resistant Enterococcus, with some strains being resistant to colistin and linezolid, which are considered to be "drugs of last resort." Genetic sequencing revealed that some of these antibiotic-resistant bacteria in the raw dog food were the same kind found in hospital patients.(5)

Hardy Diagnostics has a complete offering of diagnostic testing platforms for use in veterinarian settings. Please click here to access the complete catalog. Below are just a few products that may be of interest.

HardyCHROM Hurbi (Cat. No. J100)

Blood Agar, 5%/MacConkey Biplate (Cat. No J32)

HardyCHROM™ CRE (Cat. No. G323) shown in th

HardyCHROM™ MRSA (Cat. No. G307)

HardyCHROM™ Candida (Cat. No G301)

Mueller Hinton Agar 100mm plate (Cat. No. G45)

Mueller Hinton Agar 150 mm plate (Cat. No. H11)

HardyDisks™ AST and Susceptibility Testing Products

By Megan Roesner

References: 1, 2, 3, 4, 5