What are the characteristics of Clostridium bacteria?

Bacteria of the genus Clostridium are characterized because they are gram positive, grow in anaerobic media (with low or no oxygen) and are spore-forming. These growth and survival characteristics give this group of bacteria a high resistance in the environment that allows them to multiply in hostile environments.

These bacteria have been studied for decades in pigs because of the disease patterns they can generate. Clostridiosis in swine generate pictures called enteric, histotoxic and neurotoxic by the organic systems that invade and affect. The species that affect these organs are varied and are summarized in Table 1.

Importance of strains and toxins of Clostridium bacteria

Clostridium perfringens bacteria have been divided into seven types of strains which are named from A through G. This naming correlates to the production of toxins called major toxins which are named with Greek letters (alpha, beta, epsilon) listed in Table 2.

Intestinal clostridioses in pigs are caused by bacteria of the species C. perfringens type C and Clostridium difficile. These two bacteria have been well studied mainly in suckling piglets.

The described strains of Clostridium bacteria can cause a wide range of clinical pictures in domestic animals. Strains A and C have been significantly associated with outbreaks in piglets compatible with intestinal lesions (Table 3).

These diseases in swine usually have diarrhea as characteristic signs because is generated by the toxins produced by the bacteria.

Porcine enteritis caused by Clostridium perfringens type C

Enteric Clostridium perfringens type C infections occur worldwide. Swine with this infection have a usually fatal necrotic-hemorrhagic enteritis, mainly affecting piglets.

The toxins involved in these enteric pictures of pigs are A, B and C, being Beta toxin the most pathogenic.

Epidemiology of necrotic-hemorrhagic enteritis in swine

The affected population is usually suckling piglets which become infected through the feces of sick animals. In addition, infection can be acquired through air contaminated with spores of the bacterium.

Clostridium perfringens spores are resistant in the environment, even to heat, disinfectants and ultraviolet light. In addition, they often persist in litter used for suckling piglets.

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Pathogenesis of Clostridiosis

The disease in piglets can appear even a few hours after birth and manifests itself severely within three days of birth in the form of an epidemic outbreak. In farms with piglets without previous immunity to the bacterium, mortality can reach 100%. In older animals and the farm in general, mortality can be 60% in animals without immunity.

Colostrum from sows with immunity to enteric Clostridiosis can partially provide a defense to suckling piglets. However, if there are problems in the passive transfer of antibodies from the sow to the piglets, chronic infection can occur.

Clostridium bacteria multiply rapidly in the digestive system of pigs. The pathogenicity of Clostridium perfringens toxin B has been studied to be associated with low levels of trypsin in piglets. This trypsin can inhibit the toxin, but as trypsin is found in reduced amounts, the toxin is produced in greater quantities causing enteric lesions by damage to endothelial cells.

Clinical signs of enteric Clostridiosis in piglets

Enteric Clostridiosis lesions can be acute or chronic, depending on the immunity of the piglets.

Pigs have hemorrhagic diarrhea, weakness, uncoordinated movements, death within a few hours of onset of signs. The temperature may drop to 35°C or below and color changes in the skin of the abdomen may be noted. Some pigs may die without clinical signs due to the rapidity and severity of infection.

Pigs that survive for more days have brown diarrhea with tissue fragments and mucus. A significant sign is dehydration and weight loss leading to death within a few days.

Chronically affected pigs have intermittent diarrhea for several days, where the feces are gray and mucoid in appearance, with the perineal area stained with feces. Piglets die within a few weeks or must be culled due to progressive deterioration.

The clinical signs observed are explained by the lesions generated by Clostridium perfringens at the level of the small intestine and fragments of the spiral colon. In these organs there are hemorrhages, emphysema and fibrinonecrotic exudate, with presence of serosanguinolent fluid with fibrin. In addition, necropsies show a fibrinonecrotic membrane attached to the intestinal mucosa.

Diagnosis of clostridial enteritis diarrhea

The diagnosis of clostridial diarrhea in pigs is based on clinical signs observed in piglets. In addition, necropsy evidence is indicative of a picture compatible with Clostridium perfringens enteritis.

On the other hand, intestinal contents and feces can be used for culture and microscopic analysis in search of gram-positive bacteria.

In specific cases where it is required to diagnose the toxin involved in an outbreak, an antigen detection test is used. It is recommended to add a trypsin inhibitor or refrigerate the sample to avoid deterioration of the toxin involved. Another diagnostic method is PCR test and genotyping, which is more accurate.

Porcine enteritis due to Clostridium difficile

In pigs, Clostridium difficile infections are seen in piglets from 1 to 7 days of age. These animals acquire the infection through spores in the bedding or feces of sick pigs that enter orally.

The bacterial population is high in the first few hours of piglet life and decreases as the animal grows.

The pathogenesis of Clostridium difficile is related to the production of toxins A and B. The spores of the bacterium that enter orally are resistant to stomach acid, so they are released in the small intestine by bile salts, reaching the large intestine.

The clinical signs observed are abdominal distension, scrotal edema, and death. Lesions are in the cecum and colon where there is yellow-brown fluid. The mucosa of the intestine presents ulcers and fibrinonecrotic exudate. This causes diarrhea in pigs, as well as ascites.

The diagnosis of this disease is made by clinical signs, history and necropsy and histopathology findings. Culture is not considered since it is a bacterium present in healthy animals with difficult growth conditions.

Prevention and control strategies for Clostridium diarrhea in pigs

• Prevention of this disease focuses on prophylaxis treatments in animals with clinical signs are not effective. Equine antitoxin has been used to protect piglets without previous immunity.
• Antibiotics such as ampicillin or amoxicillin have been used, but their use can lead to antimicrobial resistance.
• Vaccination of breeding or pregnant sows with type C toxoid allows herd immunization. In addition, piglet immunity is enhanced by supplying colostrum from these sows.
• Use Alquermold Natural, developed by Biovet S.A., which contains cimenol ring and citric acid, which provides a natural preservative for the feed supplied to the pigs. The cimenol ring is a molecule of natural origin that has the antimicrobial capacity against pathogenic bacteria such as Clostridium and favors the growth of intestinal flora. In addition, it also contains citric which potentiates the effect of the cimenol ring.

In this way, a product with the bactericidal effect against Clostridium is obtained, thus preventing diarrhea associated with this pathogen in pigs without affecting the natural microbiota of the animals. In addition, Alquermold Natural does not leave residues in the meat nor does it create antimicrobial resistance.

Conclusions

Diarrheas are one of the major problems in pig farming due to the pathological effects that lead to the death of the animals. Among these diarrheas, one of the most important pathogens are bacteria of the genus Clostridium perfringens and Clostridium difficile. These microorganisms produce toxins that have serious consequences on the intestinal tract of pigs, specially piglets in their first days of life.

Diarrhea caused by Clostridiosis is usually severe, with high mortality and difficult to control due to the resistance of the spores of these bacteria in the environment. Animals are infected by oral-fecal route and lactating piglets have bloody diarrhea with necrotic lesions of the small and large intestine.

At the production level, there are economic losses associated with high mortality, inefficient treatments, decreased weight gain and epidemic outbreaks.

Prevention is focused on immunization of animals with vaccines and toxoids; however, they can be difficult to access. On the other hand, the use of combined intestinal conditioner pronutrients and cimenol ring is recommended to reduce Clostridium growth and improve the intestinal welfare of pigs. In this way, populations of pathogenic bacteria can be controlled, improving nutrient absorption, and preserving the pigs’ natural bacteria.