Neotropical Entomology 34(6): 999-1006 (2005) Formigas Como Agentes Carreadores de Bactérias Resistentes em Hospitais RESUMO -A presença de bactérias resistentes a antimicrobianos e carreadas por formigas isoladas em hospitais foi investigada em Campos dos Goytacazes, RJ. Três instituições de saúde foram visitadas nos períodos de 2001 a 2002 e amostras foram coletadas em áreas de cuidados médicos consideradas críticas baseando-se em critérios de maior risco para a aquisição de infecções por pacientes hospitalizados. Quatro espécies de formigas foram identificadas, Tapinoma melanocephalum (Fabricius) (63,1%), Paratrechina longicornis (Latreille) (21,1%), Monomorium pharaonis (L.) (10,5%) e Solenopsis saevissima (S. Smith) (5,3%) como carreadoras de 21 morfoespécies de bactérias. Os testes de identificação bacteriana e de perfil de resistência antimicrobiana foram realizados por meio de kits padronizados e avaliados por método automatizado. Entre as bactérias isoladas, algumas foram consideradas multirresistentes, incluindo o gênero Acinetobacter, Streptococcus, Gemella, e Klebsiella. Para análise antimicrobiana do gênero Enterobacter foi utilizado o método padrão de difusão em disco. Os resultados sugerem que existem riscos para pacientes que procuram por assistência de saúde nos hospitais estudados e a ocorrência de bactérias emergentes em hospitais carreadas por formigas devem ser consideradas. PALAVRAS-CHAVE: Infecçcão nosocomial, antimicrobiano, controle, formiga urbana ABSTRACT -The presence of antimicrobial-resistant bacteria and carried by ants isolated from hospitals was investigated in Campos dos Goytacazes, RJ, Brazil. Three health institutions were visited from 2001 to 2002 and samples were collected within critical areas of medical care based on criteria of greater risk of patient hospital acquired-infection. Four ant species were identified, Tapinoma melanocephalum (Fabricius) (63.1%), Paratrechina longicornis (Latreille) (21.1%), Monomorium pharaonis (L.) (10.5%), and Solenopsis saevissima (S. Smith) (5.3%) carrying 21 species of bacteria. The tests for bacteria species identification and antimicrobial-resistance profile were carried out by using standardized kits and evaluated by automated equipment. Among the bacteria isolates, some were considered multiresistant isolates, including genera Acinetobacter, Streptococcus, Gemella, and Klebsiella. For Enterobacter antibacterial analysis the disk diffusion standard method was used. The results suggest that there are risks for patients which seek for health assistance in the hospitals studied, and the presence of emerging bacteria isolates in hospital carried by ants must be considered.

Conventional control of leaf-cutting ants is mainly carried out by application of solid insecticide baits. However, alternative approaches could increase the efficiency of control methods. Here, we investigated the hypothesis that liquid and semi-solid baits are more readily ingested by leaf-cutting ants and are therefore more toxic than solid baits. Furthermore, following increased ingestion rates, ants could perform higher frequencies of trophallactic exchanges with their nest mates, thus increasing dispersal rates within the colony. Each of three diets were offered to Acromyrmex subterraneus subterraneus (Forel) and Atta sexdens rubropilosa Forel (both Hymenoptera: Formicidae) for 1 h under laboratory conditions and subsequently crop volumes were quantified. The highest crop volumes for both species were seen when the diet was offered in liquid form, and the lowest crop volumes were observed after offering solid diets. Survival rates of the ants were monitored following addition of the neonicotinoid insecticide imidacloprid (IMI) to the three diets. The ingestion of liquid and semi-solid diets + IMI by A. subterraneus resulted in 17 and 6% survival, respectively, whereas these diets caused 100% mortality of A. sexdens. Ingestion of solid diets with IMI resulted in 51% survival of A. subterraneus and 23% survival of Atta workers. Twenty-three percent of A. subterraneus which had fed on liquid diet carried out trophallactic exchanges, whereas only 10 and 3% of ants carried out trophallaxis when fed on semi-solid or solid diet, respectively. Lower trophallactic frequencies were observed for A. sexdens, with 13 and 3% of ants that had fed on liquid and semisolid diets performing trophallaxis, respectively. The low trophallactic exchange rates following ingestion of solid diets would reduce the dispersal of these compounds throughout the colony. Control strategies using solid baits should be re-examined in the light of these findings, which indicate the importance of optimizing insecticide ingestion.