Antimicrobial resistant Escherichia coli from karst waters, surfaces and bat guano in Slovenian caves

Abstract

Escherichia coli, one of the primary intestinal commensal bacteria in humans and endothermic animals, is commonly considered an indicator of faecal pollution. E. coli strains were isolated from karst rivers under different hydrological conditions, from footpaths in tourist caves and from bat guano. Isolates were tested for phenotypic resistance to ampicillin, chloramphenicol, ciprofloxacin, nalidixic acid, tetracycline and trimethoprim. The highest percentage of antimicrobial resistant E. coli was found in karst waters, followed by those from surface swabs and from bat guano. Several isolates from rivers and swabs exhibited multidrug-resistant phenotype. Environmental conditions impact the populations of E. coli; a positive correlation between dissolved oxygen and E. coli counts, and a negative correlation between conductivity and E. coli concentrations have been observed for karst rivers. Malenščica (Slovenia), a drinking water resource with an extensive catchment area, contained a relative high percentage of antimicrobial-resistant E. coli strains. None of the isolates from bat guano was resistant to ampicillin, chloramphenicol, and tetracycline. Future monitoring of bats should consider a regular follow-up of indicative microbial disease indicators in fresh guano. Regular cleansing of tourist footpaths in caves and disinfection barriers at the cave entrances reduce the concentration and transmission of E. coli significantly. A future, more detailed, study on characterization of additional E. coli isolates is needed to reveal their pathogeneicity, mechanisms of antibiotic resistance, mobile genetic elements, and gene transfer frequencies to other members of the karst microbiome.

Bats and Antibiotic Resistance: A Culprit or a Victim?

“…Another source of contamination due to direct contact with humans is tourists that visit large colonies that are an attraction in some regions. Tourists are responsible for introducing resistant strains of bacteria in and out of the cave, spreading AMR into the ecosystems (Mulec et al, 2020). To prevent the dissemination of these strains should be performed a regular cleaning of the tourist footpaths and a disinfectant barrier at the tourist cave entrance and exit (Mulec et al, 2020).…”

“…Tourists are responsible for introducing resistant strains of bacteria in and out of the cave, spreading AMR into the ecosystems (Mulec et al, 2020). To prevent the dissemination of these strains should be performed a regular cleaning of the tourist footpaths and a disinfectant barrier at the tourist cave entrance and exit (Mulec et al, 2020). Environmental compartments (e.g., water bodies) can also serve as reservoirs for multiresistant bacteria and resistance genes (Gharout-Sait et al, 2019).…”

“…In many caverns, there is a network of underground water channels that have contact with the exterior environment. These underground water bodies can be contaminated with AMR due to the infiltration of bat faecal matter during the rainy seasons or introduce contaminated water into the caves (Mulec et al, 2020).…”

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“…Os resultados de isolamento correspondem à literatura em relação as espécies isoladas e sua proporção descrita em estudos de Enterobacteriales de morcegos. Sendo geralmente descrito nas publicações o isolamento de uma grande proporção de E. coli, seguido de Enterobacter sp., Klebsiella sp., Citrobacter sp., Serratia marcescens, entre outros (Adesiyun et al, 2009;Akobi et al, 2012;Aladejana et al, 2022;Apun et al, 2008;Banskar et al, 2015;Benavides et al, 2018;Benavides et al, 2022;Cabal et al, 2015;Carrillo-Araujo et al, 2015;Daniel et al, 2013;Garcês et al, 2019;Garcês et al, 2020;García et al, 2020;García et al, 2022;Gerbáčová et al, 2020;Gharout-Sait et al, 2019;Graves et al, 1988;Hassell et al, 2019;Iovine et al, 2015;Islam et al, 2013;McDougall et al, 2019;McDougall et al, 2021 b ;McDougall et al, 2022;Nguema et al, 2020;Obi et al, 2014;Olatimehin et al, 2018;Oluduro, 2012;Selvin et al, 2019;Sens-Junior et al, 2018;Skok et al, 2020;Souza et al, 1999;;Vandžurová et al, 2013).…”