Occurrence of total coliform bacteria in a coastal sea loaded with inflows

Abstract

Kakvoća mora za kupanje predstavlja važan javnozdravstveni pokazatelj koji može biti narušen fekalnim i sekundarnim onečišćenjem. Cilj ovog istraživanja bio je ispitati pojavnost ukupnih koliformnih bakterija (UKB) u priobalju Rijeke, s naglaskom na vrste koje nisu obuhvaćene standardnim monitoringom, ali mogu ukazivati na prisutnost oportunističkih patogena i bolničkog zagađenja. Istraživanje je provedeno u sklopu projekta EUROBATH na 12 lokacija, a obuhvatilo je ukupno 1119 uzoraka morske vode. Od toga je 117 uzoraka (10,5 %) bilo pozitivno na UKB. Najzastupljeniji je bio rod Citrobacter (79,5 %), a slijedili su rodovi Klebsiella, Enterobacter i Morganella. Identificirane su vrste poput Citrobacter freundii, Klebsiella pneumoniae i Enterobacter cloacae, poznate po višestrukoj antimikrobnoj rezistenciji i kliničkoj važnosti. Statistička analiza pokazala je značajnu povezanost roda Citrobacter s kategorijom kakvoće mora „dobar“ prema koncentraciji E. coli, dok takva povezanost nije utvrđena za crijevne enterokoke, što upućuje na potencijalni nesklad među fekalnim indikatorima. Salinitet je bio jedini okolišni čimbenik koji je pokazao značajan utjecaj na pojavnost UKB, dok temperatura mora i zraka nisu imale značajnu povezanost. Rezultati potvrđuju da se pojedine vrste UKB mogu pojavljivati i u odsutnosti izravnog fekalnog zagađenja, ali unatoč tome mogu imati važnu ulogu u dodatnim programima praćenja kakvoće obalnog mora, osobito u kontekstu praćenja antimikrobne rezistencije i sekundarnog onečišćenja bolničkog porijekla. Iako njihovo uvođenje u rutinski monitoring zasad nije opravdano zbog financijskih i dijagnostičkih ograničenja, praćenje vrsta poput Citrobacter spp. i Klebsiella spp. preporučljivo je u visokorizičnim i ciljanima istraživanjima.Bathing water quality is an important public health indicator that can be affected by both fecal and secondary contamination. The aim of this study was to examine the occurrence of total coliform bacteria (TCB) in the coastal waters of Rijeka, with a focus on species not included in standard monitoring but potentially indicative of opportunistic pathogens and hospital-related pollution. The research was conducted as part of the EUROBATH project at 12 locations, with a total of 1119 seawater samples analyzed. Of these, 117 samples (10.5%) tested positive for TCB. The most prevalent genus was Citrobacter (79.5%), followed by Klebsiella, Enterobacter, and Morganella. Identified species included Citrobacter freundii, Klebsiella pneumoniae, and Enterobacter cloacae, all known for their multidrug resistance and clinical relevance. Statistical analysis revealed a significant association between the presence of Citrobacter and the "good" bathing water quality category according to E. coli levels, but not according to intestinal enterococci, indicating a potential mismatch between standard fecal indicators. Salinity was the only environmental factor that showed a statistically significant influence on TCB occurrence, while sea and air temperature did not. The results confirm that certain TCB species can be present even in the absence of direct fecal contamination, yet may still play an important role in supplementary coastal water quality monitoring programs, especially in the context of antimicrobial resistance and secondary pollution of hospital origin. While their inclusion in routine monitoring is currently not justified due to financial and diagnostic constraints, tracking species such as Citrobacter spp. and Klebsiella spp. is recommended in high-risk and targeted investigation