Studies on the occurrence of Gram-negative bacteria in ticks: Ixodes ricinusas a potential vector of Pasteurella.
Jacek Dutkiewicz 1, Nimfa Maria Stojek 2 1 - 2 - Department of Occupational Biohazards, Institute of Agricultural Medicine, Jaczewskiego2, 20-090 Lublin, Poland. email@example.com Ann Agric Environ Med 2004; 11 (2): ICID: 142649
A total of 372 Ixodes ricinus ticks (101 females, 122 males, and 149 nymphs)collected by flagging in 6 mixed woodlands of eastern Poland were examined by culture for the presenceof internal Gram-negative bacteria other than Borrelia burgdorferi. Adult ticks were examined in poolsof 2 specimens each and nymphs were examined in pools of 3-5 specimens each. Ticks were disinfected in70 % ethanol and homogenized in 0.85% NaCl. The diluted homogenate was inoculated onto 3 kinds of agarmedia: buffered charcoal yeast extract (BCYE-alpha) for isolation of fastidious Gram-negative bacteria,eosin methylene blue agar (EMB) for isolation of enterobacteria, and tryptic soya agar for isolationof all other non-fastidious Gram-negative bacteria. The Gram-negative isolates were identified with theAPI Systems 20E and NE microtests. A total of 9 species of Gram-negative bacteria were identified, ofwhich the commonest were strains determined as Pasteurella pneumotropica/haemolytica, which were isolatedon BCYE-alpha agar from ticks collected in all 6 examined woodlands. The total number of these strains(49) exceeded the total number of all other strains of Gram-negative bacteria recovered from ticks (30).Of the total number of examined ticks, the minimum infection rate with Pasteurella pneumotropica/haemolyticawas highest in females (18.8%), and slightly lower in males (12.3%) and nymphs (10%). Besides Pasteurellapneumotropica/haemolytica, the following species of Gram-negative bacteria were isolated from examinedticks: Pantoea agglomerans, Serratia marcescens, Serratia plymuthica on EMB agar and Aeromonas hydrophila,Burkholderia cepacia, Chromobacterium violaceum, Pseudomonas aeruginosa, and Stenotrophomonas maltophiliaon tryptic soya agar. Minimal infection rates with these bacteria were low, ranging from 0.7-5.9%. Ofthe isolated bacteria, Chromobacterium violaceum, Pasteurella pneumotropica/haemolytica, Pseudomonasaeruginosa, and Serratia marcescens are potentially pathogenic for man and/or animals. In particular,the common occurrence of Pasteurella pneumotropica/haemolytica in Ixodes ricinus ticks poses a potentialrisk of pasteurellosis for humans and animals exposed to tick bites.