Antimicrobial susceptibility of Leptospira isolates from dogs and rats to 12 antimicrobial agents

This study determined the antimicrobial susceptibilities of 67 isolates of Leptospira from dogs (suspect canine cases: n=7 and stray dogs: n=6) and rodents (n=54) in Trinidad to 12 antimicrobial agents using broth microdilution and macrodilution techniques. Commonly used antimicrobial agents such as the penicillin G and ceftriaxone had relatively low minimal inhibitory concentrations (MICs) while doxycycline displayed a relatively higher value but was still considered to be effective. While imipenem was the most effective with low MIC values in vitro, sulphamethoxazole-trimethoprim had the highest i.e. least effective. Based on these results, the drugs commonly used in the treatment of leptospirosis (penicillin G, penicillin-streptomycin, doxycycline and ceftriaxone) in both humans and animals in Trinidad appear to have similar MICs and MBCs in vitro when compared with published reports. The serovar of Leptospira spp. and in most cases the origin of the isolates did not significantly (P>0.05) influence their susceptibilities to the antimicrobial agents tested

Seroepidemiology of leptospirosis in dogs and rats in Trinidad

Stray dogs (n=207), suspected canine cases of leptospirosis (n=50) and rats (n=200) from the Caribbean island of Trinidad were subjected to the Microscopic Agglutination Test (MAT) for leptospirosis. The seroprevalence in stray dogs was 15.5% (n=32), the predominant serogroup was Icterohaemorrhagiae (14.5%; n=30) with agglutinations to serovars Copenhageni at 5.8%, Icterohaemorrhagiae at 4.8%, Mankarso at 3.9%. The seroprevalence among suspected canine cases was 72% (n=36) with Icterohaemorrhagiae again being the predominant serogroup at 60% inclusive of serovars: Copenhageni, 44%; Mankarso, 14%; and Icterohaemorrhagiae 2%. A seroprevalence of 16.5% was determined in rats, all agglutinations were to the Icterohaemorrhagiae serogroup (inclusive of serovars Copenhageni, 9.5%; Icterohaemorrhagiae, 5.5%; and Mankarso, 1.5%). Overall serovar Copenhageni was the most common serovar as 11.6% of all the animal species tested by the MAT were positive and may be an important zoonotic serovar in Trinidad. The titres of infecting serovars of Leptospira in suspected canine cases of leptospirosis were considerably higher than that found in stray dogs and in rats where the lowest titres were found. Age and sex were not significant risk factors except in the case of rats where age was significant, indicating that juvenile rats were at a significantly higher risk. There was no definite pattern of the distribution of positive animals or the serovars when using the MAT. Data obtained in the current study indicate that dogs and rats in Trinidad have the potential to be sources of leptospiral infections for humans. This potential has public health implications making it imperative to control rat and stray dog populations in the island to reduce the risk of human leptospirosis.