Tips from the journals of the American Society for Microbiology

06/23/04

Fatty Acids May Fight Salmonella in Chickens

Medium-chain fatty acids may be effective at controlling Salmonella bacteria in chickens say researchers from Belgium and the Czech Republic. Their findings appear in the June 2004 issue of the journal Applied and Environmental Microbiology.

The leading cause of food-borne infections in humans, Salmonella bacteria is most commonly associated with poultry. Currently, short-chain fatty acids are being used to treat chickens and prevent infection. Although they have proven somewhat effective researchers believe that the use of medium-chain fatty acids (MCFA) may further decrease the number of acquired food-borne infections in humans.

In the study, MCFA's, caproic, caprylic, and capric acid (harmless fatty acids often found in vegetable oils and flavoring) were used to challenge the growth of Salmonella enterica serovar Enteritidis in the intestinal tract of chickens. Results showed that all MCFA inhibited growth with caproic acid causing the most resistance. More specifically, MCFA was able to decrease gene expression of hilA, a regulator of the invasive capability of Salmonella bacteria. Also, when used as a feed supplement, caproic acid substantially decreased levels of S. enterica serovar Enteritidis in 5 day-old chicks 3 days after infection.

"These results suggest that MCFA have a synergistic ability to suppress the expression of the genes required for invasion and to reduce the numbers of bacteria in vivo," say the researchers. "Thus, MCFA are potentially useful products for reducing the level of colonization of chicks and could ultimately aid in the reduction of the number of contaminated eggs in the food supply."

(F.V. Immerseel, J. De Buck, F. Boyen, L. Bohez, F. Pasmans, J. Volf, M. Sevcik, I. Rychlik, F. Haesebrouck, R. Ducatelle. 2004. Medium-chain fatty acids decrease colonization and invasion through hilA suppression shortly after infection of chickens with Salmonella enterica Serovar Enteritidis. Applied and Environmental Microbiology, 70. 6: 3582-3587.)


New Vaccine May Protect Horses From Deadly Disease

Three related proteins combined may produce an effective vaccine against strangles in horses say researchers from the United Kingdom and Sweden. Their findings appear in the June 2004 issue of the journal Infection and Immunity.

Streptococcus equi subspecies equi, more commonly referred to as strangles, is one of the most serious diseases effecting horses worldwide. Highly contagious and exhibiting symptoms such as fever, lymphadenitis, and abscesses in the head and neck region, strangles has proven sensitive to penicillin, however, antibiotic treatment has been deemed relatively ineffective as infected animals may harbor the bacteria for several months. Live vaccines have been used for treatment, but often result in serious side effects such as abscesses.

"In order to combat the disease and mitigate serious clinical complications, research has mainly been aimed at developing efficient vaccines," say the researchers.

In the study, mice were immunized with a recombinant subunit vaccine containing parts of the three proteins, FNZ, SFS, and EAG from S. equi either subcutaneously (under the skin) or intranasally (through the nose), and challenged with S. equi through the nasal cavity. Vaccines in mice had a significant reduction in nasal colonization of S. equi with almost complete eradication in those receiving intranasal vaccination. Healthy horses were then administered the same vaccine intranasally and subcutaneously producing substantial antibody responses against FNZ and EAG. Further enhancement of the antibody response resulted from the addition of EtxB, a form of Escherichia coli enterotoxin and the horses showed no adverse effects to either vaccine combination.

"We found that vaccination with FNZ, SFS, and EAG together gives an antibody response that is highly protective in the mouse," say the researchers. "Thus, these antigens are promising candidates for an effective and safe vaccine against strangles." (M. Flock, K. Jacobsson, L. Frykberg, T.R. Hirst, A. Franklin, B. Guss, J.I. Flock. 2004. Recombinant Streptococcus equi proteins protect mice in challenge experiments and induce immune response in horses. Infection and Immunity, 72. 6: 3228-3236.)


Researchers Identify New Pathogen in Patient with Rheumatoid Arthritis

Japanese and German researchers have identified a novel pathogen as the cause of infection in a patient with rheumatoid arthritis. Their findings appear in the June 2004 issue of the Journal of Clinical Microbiology.

Nocardiosis, a potentially life-threatening infection of the lungs, central nervous system and skin, stems from the Nocardia species. Previous cases of nocardiosis have been attributed to the Nocardia asteroides strain.

In the case study, two varying bacterial strains that were susceptible to different drugs were found in the lung mucous and inflammatory discharge of a sixty-five year old Japanese male patient with rheumatoid arthritis. The samples were analyzed and one strain was identified as Nocardia farcinica, while the other revealed unique properties distinguishing it from other established Nocardia strains. All data collected indicated a new Nocardia species now referred to as Nocardia arthritidis.

"The genotypic and phenotypic data combined indicated that the bacterium merits description as a new Nocardia species," say the researchers. "The present study suggests that Nocardia infections can be caused by multiple species of the bacterium."

(A. Kageyama, K. Torikoe, M. Iwamoto, J.I. Masuyama, Y. Shibuya, H. Okazaki, K. Yazawa, S. Minota, R.M. Kroppenstedt, Y. Mikami. 2004. Nocardia arthritidis sp. nov., a new pathogen isolated from a patient with rheumatoid arthritis in Japan. Journal of Clinical Microbiology, 42. 6: 2366-2371.)

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