Caracterización de factores de virulencia y susceptibilidad antimicrobiana en cepas de Plesiomonas shigelloides aisladas de pacientes con diarrea aguda en Cuba / Virulence factors and in vitro susceptibility of Plesiomonas shigelloides isolated from diarrhea episodes in Cuba

Acute diarrhea is still one of the main causes of disease in developing countries. At the National Reference Laboratory for Acute Diarrhoeal Diseases, of the "Pedro Kourí" Tropical Medicine Institute, 54 Plesiomonas shigelloides strains were serotyped. As a result, the circulation of four new serotypes (O20:H2, 056:H18, 071 :H31,081 :H22) was detected. The most common antigenic variant was 094:H3. In addition, the susceptibility pattern to 21 antimicrobial agents (AA) was studied. Highest percentages of resistance were observed to ampicillin (77.7 percent), tetracycline (29.2 percent), and erythromycin (18.5 percent) while, to all other AA the resistance percentages were under 33 percent. There was no evidence of association between the serotypes and the multi-resistance patterns present in the strains under study. The frequency of virulence factors was determined: 21.15 percent of the strains turned out to be ß-haemolytic; 73.7 percent showed the presence of biofilm and 92.31 percent were hydrophobic. In 17.3 percent of the strains, the three virulence factors analysed were present. When establishing the relationship among the different virulence factors and the serotypes of the strains through cross reaction with the Shigella genus, there was evidence that 93.3 percent of the strains showed at least one of the virulence factors studied. Likewise, at least one of the virulence factors analysed was present in 90.9 percent of the multi-resistant strains.

La diarrea aguda (DA) continúa siendo una de las principales causas de consulta en los países en vías de desarrollo. Un agente de baja prevalencia en DA es Plesiomonas shigelloides. En el Laboratorio Nacional de Referencia de Enfermedad Diarreica Aguda del IPK se estudiaron 54 cepas conservadas de P. shigelloides. Se determinó el serotipo detectándose por primera vez en el país la circulación de cuatro serotipos (O20:H2, 056:H18, 07LH31, 08LH22) así como la vanante antigénica de mayor prevalencia (094:H3). Se estudió el comportamiento de las cepas frente a 21 agentes antimicrobianos obteniéndose los mayores porcentajes de resistencia frente a ampicilina (77,7 por ciento), tetraciclina (29,2 por cientoo) y eritromicina (18,5 por ciento) mientras que para el resto se obtuvieron porcentajes de resistencia inferior a 33 por cientoo. No se evidenció asociación entre los serotipos y los patrones de multi-resistencia presentes en las cepas del estudio. Se estudiaron los factores de virulencia: actividad hemolítica, producción de exo-polisacáridos y adherencia a hidrocarburos. El 22,2 por ciento de las cepas resultaron B hemolíticas, 72,2 por cientoo presentó bio-película y 92,31 por ciento fueron hidrofóbicas. El 17,3 por ciento de las cepas presentaron los tres factores de virulencia. Estableciendo una relación entre los factores de virulencia y los serotipos de las cepas con reacción cruzada con el género Shigella se evidenció que 93,3 por cientoo de las cepas presentaron al menos uno de los factores de virulencia. El 90,9 por cientoo de las cepas multi-resistentes presentó al menos uno de ellos.

Aeromonas species and Plesiomonas shigelloides in diarrhoea in Goa.

Sixty six strains (1.9%) of Aeromonas species and 7 strains (0.2%) of Plesiomonas shigelloides were isolated from 3484 stool/rectal swabs from cases of diarrhoea during the study period of four years from August 1986 to July 1990 in Goa. Although the selective medium (Ampicillin sheep blood agar) was not used for the isolation of Aeromonas, an increase in the rate of isolation of Aeromonas from 0.2% in the year 1986 to 6.0% in 1990 was observed. Stool samples from 100 controls (patients without diarrhoea) examined in the year 1989 did not yield either of the pathogens.

Effect of antibiotics on serum bactericidal action on Plesiomonas shigelloides by normal human serum.

Thirteen clinical isolates of Plesiomonas shigelloides were tested for antibiotic susceptibility of tetracycline, kanamycin-sulphate, gentamicin, erythromycin and ciprofloxacin. All the strains were susceptible to all these antibiotics. The minimal inhibitory concentration (MIC) of all these antibiotics were: Kanamycin-sulphate-MIC 0.4-10.0 micrograms/ml, tetracycline-MIC 0.25-2.4 micrograms/ml, gentamicin-MIC 2.0-12.0 micrograms/ml, erythromycin-MIC 0.5-14.0 micrograms/ml and ciprofloxacin-MIC < or = 0.006 micrograms/ml. The MIC and MBC (minimal bactericidal concentration) of the antibiotics kanamycin-sulphate, tetracycline, gentamicin, erythromycin and ciprofloxacin changed little in the presence of serum protein. Different concentrations of sub-MICs played synergistic role in serum bactericidal action on this organism.