Svjetlana Dekić

Extensively and multi drug-resistant Acinetobacter baumannii recovered from technosol at a dump site in Croatia

In a karst pit above City of Rijeka in Croatia the hazardous industrial waste was continuously disposed from 1955 to 1990, and later it was periodically used as an illegal dump site. The surface part of a technosol at the edge of dump was analysed mineralogically, geochemically and bacteriologically. From the technosol rich in petroleum hydrocarbons and heavy metals three isolates of Acinetobacter baumannii were recovered. Isolates from technosol shared many features that are previously described for clinically isolates: the affiliation to IC1 and 2, multi-drug resistant (MDR) or extensively drug-resistant (XDR) antibiotic resistance profile, carbapenem resistance mediated by blaOXA72 and blaOXA23 genes, and the expression of virulence factors. In in vitro conditions, isolates were able to survive in contact with technosol during 58days of monitoring. The most probable source of A. baumannii in technosol was the illegally disposed hospital waste. Proper management and disposal of human solid waste is mandatory to prevent the spread of clinically important A. baumannii in nature.

Transmission and survival of carbapenem-resistant Acinetobacter baumannii outside hospital setting

Acinetobacter baumannii origin and its epidemiology is under a great concern worldwide since this microorganism has become a leading nosocomial pathogen of the 21th century among the ESKAPE group of microorganisms. The aim of the study was to monitor and explore the epidemiology of this important hospital pathogen in the second largest clinical university hospital in Croatia. The presence of A. baumannii in hospital wastewater, as a route for possible transmission outside of the hospital setting, as well as its survival in environmental conditions including seawater, was investigated. During the examination period, ten both carbapenem and multidrug-resistant isolates of A. baumannii were recovered from hospital wastewater and compared to the clinical isolates originating from the same monitoring period. Multiplex PCR confirmed that four wastewater isolates harboured blaOXA-23-like, while five wastewater isolates harboured blaOXA-40-like genes sharing 100% sequence identity with blaOXA-72 sequence described in the same hospital in 2009, confirming the presence of an endemic cluster. Survival of A. baumannii in natural seawater was examined during 50 days of monitoring and to the best of our knowledge, was performed for the first time.

Survival of ESKAPE pathogen Acinetobacter baumannii in water of different temperatures and pH

Bacterium Acinetobacter baumannii is an emergent pathogen associated with nosocomial infections, which can be also found in natural waters. The impact of ecological factors on A. baumannii is insufficiently investigated. The aim was to examine the influence of temperatures (-20 to 80 °C) and pH values (2 to 12) on the survival of environmental and clinical isolates of A. baumannii in nutrient-deprived spring water (SW) and nutrient-rich diluted nutrient broth during 5 months. A. baumannii successfully survived at -20 to 44 °C and neutral pH for 5 months, which is consistent with the persistence of this pathogen in the hospital environment. At temperatures 50 to 80 °C the survival of A. baumannii ranged from 5 days to 5 min. The pH 2 was the most lethal with survival time up to 3 hours, suggesting that acidic conditions are promising for disinfection of water contaminated with A. baumannii. Although the type of media was not statistically significant for long-time survival, the extensively resistant or pandrug-resistant isolates survived better in SW than susceptible or multidrug-resistant isolates. Two distinct colony phenotypes were recorded at extreme temperatures and pH values. The results of this study provide insight into the behaviour of this emerging pathogen in the environment.

Characterization of Acinetobacter baumannii from water and sludge line of secondary wastewater treatment plant.

The elimination of potentially pathogenic bacteria in wastewater treatment plants (WWTPs) attracts much attention in public health. Reports on the occurrence of the emerging hospital pathogen Acinetobacter baumannii in wastewaters do not include a continuous monitoring at all WWTP stages. The objective of this study was to characterize A.xa0baumannii recovered from the water and sludge line of the secondary WWTP in Zagreb, Croatia over the period of one year. Recovery of A.xa0baumannii was performed using CHROMagar Acinetobacter plates. Antimicrobial susceptibility testing was performed with broth microdilution and results interpreted using EUCAST breakpoints for clinical isolates of A.xa0baumannii. Molecular characterization was performed by WGS and cgMLST. The secondary WWTP treating the urban wastewater is constantly receiving viable A.xa0baumannii along with genes encoding carbapenem resistance, and emitting them via effluent into the environment. Furthermore, A.xa0baumannii from influent are incorporated into activated sludge flocs in aeration basin. A.xa0baumannii can survive the technological process of anaerobic mesophilic sludge digestion, and is finally destroyed in alkaline lime-treated stabilized sludge. The majority (102/119) of A.xa0baumannii isolates were carbapenem-resistant, while antibiotic-susceptible isolates (17/119) were rarely recovered from all WWTP stages. Carbapenem-resistant isolates belonged to international clonal lineage IC2 carrying OXA-23 and IC1 carrying OXA-72, while the susceptible isolates belonged to IC5 or were unclustered. Increased resistance to antibiotics, together with the appearance of carbapenem- and even pandrug-resistant isolates in effluent as compared to influent wastewater, suggests the need of additional disinfection of effluent prior to its discharge into the natural recipient.

Emerging human pathogen Acinetobacter baumannii in the natural aquatic environment: a public health risk?

Abstract Bacterium Acinetobacter baumannii is an emerging human pathogen whose presence in the aquatic environment raises the issue of public health risk. Fish colonization represents the potential route of pathogen transmission to humans. The aim was to examine the colonization of A. baumannii to freshwater fish Poecilia reticulata. An extensively drug-resistant A. baumannii was tested at three concentrations in natural spring water. Additionally, 70 fish from the Sava River (Croatia) were screened for the presence of A. baumannii, which was not found in gill swabs or analysed gut. The colonization potential of A. baumannii in freshwater fish is dependent upon its concentration in surrounding water. The low concentration of A. baumannii in natural waters represents low colonization potential of freshwater fish. The risk for public health exists in closed water bodies where there is constant inflow of water polluted by A. baumannii in concentrations above 3 log CFU mL−1.

Presence of carbapenem-resistant bacteria in soils affected by illegal waste dumps

ABSTRACT The carbapenem-resistant bacteria (CRB) are currently at the top of the WHO priority list of bacteria that pose the greatest threat to human health. Considering that soil is one of the important environments for the emergence of antibiotic-resistant bacteria, we isolated and quantified cultivable CRB in soils across Croatia, including ones affected by illegal dumps. We cultivated CRB at two temperatures, distinguishing between the intrinsically resistant CRB (37°C, mostly Stenotrophomonas spp.) and the ones that are presumably human-associated and clinically relevant (42°C, Acinetobacter sp., Enterobacteriaceae, Burkholderia spp.). Our study demonstrated that distinguishing between the two offers a better insight into the diversity of CRB in the environment. The ones cultivated at 37°C were found in almost all soil samples, while the presumably clinically relevant ones were absent from uncontaminated pasture and grassland, indicating that human-associated CRB are unlikely to be found in soils spared from anthropogenic influence.