Pseudomonas aeruginosa

Pseudomonas aeruginosa, also known as Pseudomonas aeruginosa, is a Gram-negative, aerobic, rod-shaped bacterium with only one type of motility. It is an opportunistic pathogen that often causes infections characterized by greenish-colored pus and exudates in affected tissues.

Pseudomonas aeruginosa has numerous transmission routes. In poultry, contamination of hatching eggs during incubation is the primary cause of outbreaks in chicks. Additionally, vaccination, drug injections, cage-related injuries from sharp objects, and stress caused by flock transfers are other major pathways for Pseudomonas aeruginosa infection. In recent years, cases of Pseudomonas aeruginosa infection in chicks reported in China have largely been linked to contamination occurring during the administration of Marek’s disease vaccine. High ambient temperatures or prolonged transportation can further weaken chicks' immune systems, making them more susceptible to the disease. While this illness can occur year-round, it tends to peak during the spring hatching season. Chicks exhibit the highest susceptibility to Pseudomonas aeruginosa, though their vulnerability gradually decreases as they grow older.

Additionally, exogenous sources of contamination are also one of the key factors contributing to Pseudomonas aeruginosa infections, such as animal drinking water, feed, bedding materials, and housing equipment.

In immunocompetent animals and most immunodeficient animals, infection with Pseudomonas aeruginosa typically does not produce noticeable clinical symptoms. However, mice with neutropenia—such as those treated with radiation therapy or antimitotic agents—exhibit classic clinical signs after Pseudomonas aeruginosa infection. In severely immunocompromised animals, the bacterium can breach the nasopharyngeal or intestinal mucosal barriers, leading to systemic sepsis or bacteremia. Common clinical symptoms include asymptomatic death, conjunctivitis, nasal discharge, and general rodent-specific symptoms like anorexia, disheveled fur, and a hunched posture.

Additionally, a case of chronic otitis caused by Pseudomonas aeruginosa in a Gir cow directly progressed to purulent meningitis, highlighting the risk of secondary Pseudomonas aeruginosa infection.

Pseudomonas aeruginosa can be diagnosed through culture and biochemical methods or by PCR. The most commonly used samples include animal intestinal contents, with small amounts often found in isolated areas, the cecum, and the nasopharynx, as well as in animal drinking water or environmental swabs. This bacterium grows well on non-selective media, though selective media can further enhance isolation efficiency. Colonies typically exhibit a distinctive blue-green color and fluoresce under ultraviolet light. P. aeruginosa ferments glucose and xylose, and its oxidase test is positive; however, it does not ferment maltose, lactose, or sucrose. Additionally, it does not produce indole, and the H2S test remains negative. Finally, it tests positive in both the semi-solid motility test and the 42°C growth test.

To prevent animals from contracting Pseudomonas aeruginosa, they must be bred in a strictly bio-exclusion environment, particularly for immunocompromised animals. Additionally, water quality is crucial—before use, it must be disinfected, especially for animals with neutropenia.

Pseudomonas aeruginosa is sensitive to most disinfectants commonly used in animal facilities. In theory, any chemical or mechanical method of disinfection can effectively eliminate P. aeruginosa from the environment—but typically, P. aeruginosa thrives within biofilms. Without first breaking down these biofilms, the disinfection process becomes significantly less effective. To ensure animals remain free of P. aeruginosa infections, breeding strategies such as embryo transplantation or hysterectomy performed on P. aeruginosa-free mother rats are essential. Additionally, recent research has explored melatonin's potential to combat P. aeruginosa resistance, and further reports on the practical application of melatonin in this context continue to emerge.

References

[1] Antonio Carlos Lopes, Sousa Davi Emanuel Ribeiro, Isabel Luana de Mâcedo, Karoline Lacerda Soares, José Renato Junqueira Borges, Carlos Frederico Martins, Adriano Queiroz de Mesquita, Valéria Dutra de Castro, Márcio Botelho. Suppurative Meningoencephalitis Caused by Pseudomonas aeruginosa Resulting from Direct Extension of Chronic Otitis in a Gir Cow.[J]. Veterinary Sciences, 2023, 10(6).

[2] Suri. Pseudomonas aeruginosa Infection in Chickens [J]. New Agriculture, 2023, (05):49-50.

[3] Bai Jiangsong, Zhang Zihui, Lian Pengjing, Wang Xiao, Qiao Jian. Investigations on melatonin's effects on mink resistance to Pseudomonas aeruginosa[J]. Emerging Animal Species, 2022, 5.

[4] Zhao Yijie, Shao Lele, Jia Lihong, Meng Ziyi, Liu Yana, Wang Yuhan, Zou Bo, Dai Ruitong, Li Xingmin, Jia Fei. Subcellular inactivation mechanisms of Pseudomonas aeruginosa treated by cold atmospheric plasma and its application on chicken breasts[J]. Food Research International, 2022, 160.