Emergence Of Cephalosporin Resistance Research Articles

Azithromycin susceptibility testing for salmonella enterica isolates: Comparing disk diffusion results with MIC gradient strips

Background: Enteric fever remains an imperative public health problem in developing countries. After the emergence of cephalosporin resistance in Salmonella enterica subsp. enterica serovar Typhi, azithromycin is increasingly being used for oral treatment of enteric fever. Reports of sporadic azithromycin resistance have been reported across the country, additionally, misuse of azithromycin during the COVID-19 pandemic has concerns regarding emerging azithromycin resistance. This study evaluated the reliability of the disc diffusion method as a screening test for detecting azithromycin resistance by comparing it with the minimum inhibitory concentrations (MIC) gradient strip results, in 231 typhoidal salmonellae. Material and Methods: This prospective study was conducted in the Section of microbiology of the Shaukat Khanum Memorial Cancer Hospital and Research Centre, Lahore from March 2022 to March 2023. Isolates recovered from blood cultures of patients, suffering from enteric fever were selected. Azithromycin susceptibility testing was performed both by disk diffusion and as well as gradient strips and their results were compared. Results: Among typhoidal salmonellae, a significant portion consisted of extensively drug resistant Salmonella Typhi (61.9%). Only one XDR S. Typhi was found to be resistant to azithromycin both by disk diffusion method and MIC gradient strip method, with a MIC value of 64µg/ml. The study found no discrepancy between the disk diffusion and gradient strip methods. Conclusion: The current study found no discordance between disk diffusion and gradient strip test methods for evaluating azithromycin susceptibility among typhoidal salmonellae. Keywords: Azithromycin, disk diffusion testing, enteric fever, Minimum inhibitory concentration, Salmonella Typhi

Involvement of the Eukaryote-Like Kinase-Phosphatase System and a Protein That Interacts with Penicillin-Binding Protein 5 in Emergence of Cephalosporin Resistance in Cephalosporin-Sensitive Class A Penicillin-Binding Protein Mutants in Enterococcus faecium.

ABSTRACTThe intrinsic resistance of Enterococcus faecium to ceftriaxone and cefepime (here referred to as “cephalosporins”) is reliant on the presence of class A penicillin-binding proteins (Pbps) PbpF and PonA. Mutants lacking these Pbps exhibit cephalosporin susceptibility that is reversible by exposure to penicillin and by selection on cephalosporin-containing medium. We selected two cephalosporin-resistant mutants (Cro1 and Cro2) of class A Pbp-deficient E. faecium CV598. Genome analysis revealed changes in the serine-threonine kinase Stk in Cro1 and a truncation in the associated phosphatase StpA in Cro2 whose respective involvements in resistance were confirmed in separate complementation experiments. In an additional effort to identify proteins linked to cephalosporin resistance, we performed tandem affinity purification using Pbp5 as bait in penicillin-exposed E. faecium; these experiments yielded a protein designated Pbp5-associated protein (P5AP). Transcription of the P5AP gene was increased after exposure to penicillin in wild-type strains and in Cro2 and suppressed in Cro2 complemented with the wild-type stpA. Transformation of class A Pbp-deficient strains with the plasmid-carried P5AP gene conferred cephalosporin resistance. These data suggest that Pbp5-associated cephalosporin resistance in E. faecium devoid of typical class A Pbps is related to the presence of P5AP, whose expression is influenced by the activity of the serine-threonine phosphatase/kinase system.

S06.1 Treating Contacts to Gonorrhoea and Chlamydia Without a Clinic Visit; The Efficacy and Effectiveness of Different Models

The sex partners of persons with Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (GC) infection must be treated to prevent repeat infection of the index patient and to interrupt forward transmission...

Antimicrobial Resistance and Molecular Epidemiologic Characteristics ofNeisseria gonorrhoeaeIsolated from Korea in 2013

Background: Antimicrobial resistance of Neisseria gonorrhoeae has become a serious problem worldwide, and ceftriaxone non-susceptible isolates have been recently reported from Japan and Europe. In this study, we evaluated the antimicrobial susceptibilities and molecular epidemiological characteristics of isolates from Korea in 2013. Methods: Sixty strains of N. gonorrhoeae were collected from Korean patients and prostitutes. Antimicrobial susceptibility was tested by the agar dilution and disk diffusion methods. N. gonorrhoeae multi-antigen sequence typing (NG-MAST) was performed in order to determine the molecular epidemiologic relatedness. Results: All of isolates were non-susceptible to penicillin G and tetracycline, and the rate of ciprofloxacinresistant isolates was 95% in 2013. The MICs of ceftriaxone were within the susceptible range for all isolates, but one isolate non-susceptible to cefixime (MIC=0.5 μg/mL) was encountered. The isolates with decreased susceptibility (MIC≤0.12 μg/mL) to cefixime or ceftriaxone accounted for 10% and 14% of the isolates tested, respectively. In NG-MAST analysis, 40 different STs were encountered among the 59 isolates. Isolates that belonged to tbpB110 showed higher cefixime and ceftriaxone MICs (0.12-0.5 μg/ mL) as well as cefixime resistance. Conclusion: Most of the N. gonorrhoeae isolates showed susceptibility to spectinomycin and cephalosporins. Due to the emergence of isolates that are non-susceptible to cefixime and the prevalence of isolates with the tbpB110 allele belonging to ST1407, which cause cefixime and ceftriaxone treatment failure in successful global clones of N. gonorrhoeae, a continuous nationwide antimicrobial surveillance program is required to monitor the emergence of cephalosporin resistance in N. gonorrhoeae. (Ann Clin Microbiol 2013;16:182-187)