Enterococcus hirae is a type of bacteria commonly found in various environments and within the gut of many animals, including humans. While often a harmless inhabitant, E. hirae has the potential to cause infections under certain circumstances, affecting both animals and, less frequently, humans.
Understanding Enterococcus hirae
Enterococcus hirae is classified as a Gram-positive bacterium, meaning it has a thick cell wall that retains certain stains. It exists as part of the normal microbiota in the gastrointestinal tracts of various mammals and birds, including cattle and poultry. Beyond animal hosts, E. hirae can also be found in environmental niches such as soil, water, and plant ecosystems, demonstrating its adaptability.
This bacterium is resilient, tolerating a wide range of temperatures, from approximately 10 to 45 degrees Celsius, and acidic environments with pH levels between 4.6 and 9.9.
Its Role in Human and Animal Health
While Enterococcus hirae often acts as a commensal organism, it can transform into an opportunistic pathogen. This occurs in individuals or animals with weakened immune systems, or when the bacteria gain access to parts of the body they do not normally inhabit. In humans, E. hirae infections are relatively rare, accounting for a small percentage (0.4% to 3.03%) of all Enterococcal infections.
When human infections do occur, they can manifest as urinary tract infections (UTIs), particularly in individuals with pre-existing conditions like diabetes or benign prostatic hyperplasia. Other reported human infections include wound infections, biliary tract infections, and, less commonly, more severe systemic infections such as pyelonephritis and infective endocarditis. The bacterium has also been isolated from intra-peritoneal samples and blood cultures in hospitalized patients.
Enterococcus hirae plays a more prominent role in animal health, particularly within agricultural settings. In poultry, it can cause conditions such as diarrhea, endocarditis (heart valve infection), and bloodstream infections, leading to increased mortality rates in young broiler breeders. Pigs affected by E. hirae may exhibit loose or watery diarrhea and a rough hair coat. In cattle, E. hirae has been identified as a potential cause of mastitis, an inflammation of the udder that can reduce milk production.
Challenges of Antibiotic Resistance
Enterococcus species, including E. hirae, are recognized for their inherent and acquired resistance to various antibiotics, presenting a challenge in treatment. This resistance can arise through different mechanisms. Some bacteria, for instance, may develop efflux pumps, which are specialized proteins that actively pump antibiotic drugs out of the bacterial cell, preventing them from reaching their target. Other mechanisms include the production of enzymes that inactivate antibiotics or modifications to the antibiotic’s target site within the bacterial cell, reducing the drug’s effectiveness.
This widespread resistance makes E. hirae infections more difficult to treat, particularly in healthcare and agricultural environments where antibiotic use is common. For example, E. hirae isolates from beef production systems have shown high resistance to tetracycline (65%) and erythromycin (57%), with over half exhibiting multi-drug resistance. The ability of E. hirae to transfer antimicrobial resistance to other Enterococci, such as E. faecalis, further complicates treatment strategies and raises public health concerns.
Strategies for Prevention and Management
Preventing and managing Enterococcus hirae infections involves a combination of hygiene practices and targeted interventions. In healthcare settings, consistent handwashing is important to limit the spread of bacteria. Proper wound care and careful management of medical devices like catheters also help prevent human infections.
In animal agriculture, implementing biosecurity measures is important to control the spread of E. hirae. This includes regular disinfection of drinking water, troughs, and feeders to minimize bacterial presence on farms. Disinfectants can be used in animal drinking water to reduce the risk of E. hirae outbreaks.
When infections do occur, managing them effectively requires accurate diagnostic testing to identify the specific bacterial species and its antibiotic susceptibility profile. This information guides the selection of appropriate antibiotics. Judicious use of antibiotics is emphasized to slow the development and spread of resistance.