Antibiotic resistance and extended-spectrum β-lactamases in isolated bacteria from seawater of Algiers beaches (Algeria)

Abstract

The aim of the study was to evaluate bacterial antibiotic resistance in seawater from four beaches in Algiers. The most significant resistance rates were observed for amoxicillin and ticarcillin, whereas they were relatively low for ceftazidime, cefotaxime and imipenem. According to sampling sites, the highest resistance rates were recorded for 2 sites subjected to chemical and microbiological inputs (amoxicillin, 43% and 52%; ticarcillin, 19.6% and 47.7%), and for 2 sites relatively preserved from anthropogenic influence, resistance rates were lowest (amoxicillin, 1.5% and 16%; ticarcillin, 0.8% and 2.6%). Thirty-four bacteria resistant to imipenem (n=14) or cefotaxime (n=20) were identified as Pseudomonas aeruginosa (n=15), Pseudomonas fluorescens (7), Stenotrophomonas maltophilia (4), Burkholderia cepacia (2), Bordetella sp. (1), Pantoea sp. (1), Acinetobacter baumannii (1), Chryseomonas luteola (1), Ochrobactrum anthropi (1) and Escherichia coli (1). Screening for extended spectrum β-lactamase showed the presence of CTX-M-15 β-lactamase in the E. coli isolate, and the encoding gene was transferable in association with the IncI1 plasmid of about 50 kbp. Insertion sequence ISEcp1B was located upstream of the CTX-M-15 gene. This work showed a significant level of resistance to antibiotics, mainly among environmental saprophytic bacteria. Transmissible CTX-M-15 was detected in E. coli; this may mean that contamination of the environment by resistant bacteria may cause the spread of resistance genes.

Fig. 1

β-Lactam resistance among total flora from beach seawater. AMX: amoxicillin; TIC: ticarcillin; CTX: cefotaxime; CAZ: ceftazidime; FOX: cefoxitin; IMP: imipenem.

Fig. 2

PCR products of bla_CTX-M gene (A) and map of the nucleotide sequence of bla_CTX-M-15 gene (B) A: Detection of bla_CTX-M gene with consensus primers for family (left) and group 1 (right) in ESBL-positive E. coli (C1) and in its transconjugants (T1 and T2). The amplification band size of the bla_CTX-M family is 550 bp and for group 1 bla_CTX-M is 863 bp. C−: negative control; C+: positive control; M: 100 bp DNA marker. B: Map of the nucleotide sequence of the 3′ end of ISEcp1 and bla_CTX-M-15 and schematic representation of ISEcp1- bla_CTX-M-15. The sequences at the 3′ and 5′ of the primers used for sequencing are underlined. P-10: sequence of CTX-M-15 promoter region, IR-R: right inverted repeat of ISEcp1, sequence W: intercalary sequence of 48 bp (underlined) between ISEcp1 and bla_CTX-M-15. Initiation and stop codons of bla_CTX-M-15 are boxed in grey.

Fig. 3

Plasmid profiles of ESBL-positive E. coli (C1) and its transconjugants (T1 and T2). M1: pRK2048 (48 kbp) and M2: E. coli V517 (54, 5.6, 5.1, 3.9, 3, 2.7 and 2.1 kbp)