Acinetobacter calcoaceticus-baumannii complex prevalence, spatial-temporal distribution, and contamination sources in Canadian aquatic environments

Abstract

Acinetobacter calcoaceticus-baumannii (ACB) complex has been identified as a group of emerging opportunistic pathogens that cause nosocomial infections. The current study investigates the prevalence, distribution, and diversity of pathogenic ACB complex in various aquatic systems with different uses. Of the total 157 agricultural, raw drinking water intake, recreational beach, and wastewater treatment plant (WWTP) effluent samples, acinetobacters were isolated, quantified, and confirmed by genus- and ACB complex-specific PCR assays. Of all agricultural surface water samples, A. calcoaceticus (65%) was more frequently detected than A. pittii (14%), A. nosocomialis (9%), and A. baumannii (3%). In WWTP effluent samples, A. baumannii was more prevalent in de-chlorinated (60%) samples compared to both A. pittii and A. nosocomialis (40%). Interestingly, A. nosocomialis (43%), A. calcoaceticus (29%), and A. baumannii (14%) were detected in raw drinking water intake samples, whereas A. pittii (50%) and A. nosocomialis (25%) were detected in beach samples. Although no sampling location-specific differences were recorded, significant (P < 0.05) seasonal differences were observed when agricultural surface water samples collected in spring were compared with the summer and fall. Whereas effluent chlorination significantly impacted the degree of prevalence of Acinetobacter in WWTP effluent samples, overall, the prevalence of ACB complex in all sampling locations and seasons indicates that these water sources, containing human-associated ACB complex, may pose potential health risks as community-acquired opportunistic infections.IMPORTANCEAcinetobacter calcoaceticus-baumannii (ACB) complex is a group of organisms known to cause problematic nosocomial opportunistic infections. A member of the species complex, A. baumannii, is becoming a global threat to infection treatment as strains are increasingly develop resistance to antibiotics. The prevalence and distribution of potentially pathogenic Acinetobacter calcoaceticus-baumannii complex species remain poorly understood, and there is a need to better understand the occurrence of A. baumannii in non-nosocomial environments. Our research details the spatial-temporal distribution of ACB complex species in a regional watershed and highlights the presence of ACB complex in wastewater effluent that is discharged into a river. These findings deepen our understanding of this group of species in non-nosocomial environments and encourage the development of monitoring programs for these species in regional waters.

Keywords: Acinetobacter calcoaceticus-baumannii complex; agriculture; beach water; environment; surface water; wastewater.

Fig 1

Study map showing various aquatic sampling sites including agricultural tributary (SN-5, SN-6, SN-10, and SN-253) and drainage (SN-18, SN-19, SN-20, and SN-21), forest (SN-24), drinking water intake source (SN-1), wastewater treatment plant (ROPEC-WWTP), and recreational beach.

Fig 2

Percent Acinetobacter species-positive samples collected from various aquatic environments. (A) prevalence of Acinetobacter species in agricultural, forest, raw drinking intake, and beach surface water samples. (B) season volume-weighted average cell concentrations (CFU 100 mL⁻¹) of Acinetobacter species from agricultural (Tributary: 5, 6, 10, and 253; Drainage: 18, 19, 20, and 21) and forest/wetland (24). (C) prevalence of Acinetobacter species in WWTP treatment stages. (D) volume-weighted average concentrations (CFU 100 mL⁻¹) of Acinetobacter species from WWTP pre-chlorinated, chlorinated, and de-chlorinated samples. Statistical significance (P < 0.001) is shown as *** in (B) and (D).

Fig 3

Percent of ACB complex-positive samples collected from various aquatic sources. ACB complex in agricultural (tributary and drainage), forest, WTP intake, beach and WWTP (pre-chlorinated, chlorinated, and de-chlorinated) samples.

Fig 4

(A) percent of ACB complex detected in surface water samples collected from agricultural (tributary and drainage), forest, raw drinking intake, and beach. (B) percent ACB complex detected in WWTP samples. (C) seasonal rate of prevalence of ACB complex in tributary, agricultural drainage, forest, and WTP raw intake source samples.