Relationship between antibiotic- and disinfectant-resistance profiles in bacteria harvested from tap water

Abstract

Chlorination is commonly used to control levels of bacteria in drinking water; however, viable bacteria may remain due to chlorine resistance. What is concerning is that surviving bacteria, due to co-selection factors, may also have increased resistance to common antibiotics. This would pose a public health risk as it could link resistant bacteria in the natural environment to human population. Here, we investigated the relationship between chlorine- and antibiotic-resistances by harvesting 148 surviving bacteria from chlorinated drinking-water systems and compared their susceptibilities against chlorine disinfectants and antibiotics. Twenty-two genera were isolated, including members of Paenibacillus, Burkholderia, Escherichia, Sphingomonas and Dermacoccus species. Weak (but significant) correlations were found between chlorine-tolerance and minimum inhibitory concentrations against the antibiotics tetracycline, sulfamethoxazole and amoxicillin, but not against ciprofloxacin; this suggest that chlorine-tolerant bacteria are more likely to also be antibiotic resistant. Further, antibiotic-resistant bacteria survived longer than antibiotic-sensitive organisms when exposed to free chlorine in a contact-time assay; however, there were little differences in susceptibility when exposed to monochloramine. Irrespective of antibiotic-resistance, spore-forming bacteria had higher tolerance against disinfection compounds. The presence of chlorine-resistant bacteria surviving in drinking-water systems may carry additional risk of antibiotic resistance.

Chlorine Tolerance and Inactivation of Escherichia coli recovered from Wastewater Treatment Plants in the Eastern Cape, South Africa

“…Previous studies have shown that the highest reduction of bacterial population occurred within 10-15 min of exposure [50,51].…”

“…Bacterial inactivation was rapid within the first 10 min while inactivation rate slowly declined afterwards with increase in contact time. Previous studies have shown that the highest reduction of bacterial population occurred within 10-15 min of exposure [50,51].…”

Stress resistance in naturalised waste water E. coli strains

“…Interestingly, it has been demonstrated that chlorine treatment can promote antibiotic resistance (Murray et al, 1984). Khan et al (2016) observed that chlorine-tolerant strains of bacteria isolated from chlorinated drinking water systems were more resistant to tetracycline, sulfamethoxozole and amoxicillin, and Jia et al (2015) observed that chlorine residual was an important parameter is driving antibiotic resistance in bacterial populations found in drinking water distribution systems, including E. coli. Given that antibiotic-resistant E. coli are relatively abundant in treated waste water (Iwane et al, 2001), as are uspC-IS30-flhDC-positive E. coli strains, it would be interesting to evaluate whether uspC-IS30-flhDC-positive E. coli are antibiotic resistant.…”

The occurrence of heavy metals and metal-resistant bacteria in water and bottom sediments of the Straszyn reservoir (Poland)

“…Responses range from lethality/complete inhibition at high concentrations, selective survivability of resistant populations at sub-inhibiting concentrations, to responses triggering biochemical stress at much lower (sub-inhibitory) concentrations. Some of surviving bacteria may have increased the innate resistance to those impacts [45]. Fig.…”