Disc Diffusion Testing of Azithromycin Against Clinical Isolates of Typhoidal Salmonellae: A Diagnostic Conundrum

Shoaib, Muhammad; Satti, Luqman; Hussain, Ashfaq; Khursheed, Nazia; Sarwar, Saba; Shah, A.H

doi:10.7759/cureus.16777

Cited by 5 publications

(6 citation statements)

References 26 publications

(38 reference statements)

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“…Disc diffusion data for azithromycin were available for 1,779 isolates. However, previous work has shown that disc diffusion method can detect azithromycin susceptible strains with 100% specificity and 100% sensitivity, but the sensitivity of detection of resistant strains is much lower [27,28]. Therefore, all isolates interpreted as resistant using disc diffusion were retested using MIC strips.…”

Section: Resultsmentioning

confidence: 99%

23-year trends indicate low rates of antimicrobial resistance inSalmonellaParatyphi A

Sajib

Tanmoy

Hooda

et al. 2023

Preprint

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Background: Typhoid and paratyphoid remain common bloodstream infections in areas with suboptimal water and sanitation infrastructure. Paratyphoid, caused by Salmonella Paratyphi A, is less prevalent than typhoid and its antimicrobial resistance (AMR) trends are less documented. Empirical treatment for paratyphoid is commonly based on the knowledge of susceptibility of Salmonella Typhi, which causes typhoid. Hence, with rising drug resistance in Salmonella Typhi, last-line antibiotics like ceftriaxone and azithromycin are prescribed for both typhoid and paratyphoid. Here, we report 23-year AMR trends of Salmonella Paratyphi A in Bangladesh. Methods: From 1999 to 2021, we conducted enteric fever surveillance in two major pediatric hospitals and three clinics in Dhaka, Bangladesh. Blood cultures were performed at the discretion of the treating physicians; cases were confirmed by culture, serological and biochemical tests. Antimicrobial susceptibility was determined following CLSI guidelines. Results: Over 23 years, we identified 2,725 blood culture-confirmed paratyphoid cases. Over 97% of the isolates were susceptible to ampicillin, chloramphenicol, and cotrimoxazole, and no isolate was resistant to all three. No resistance to ceftriaxone was recorded, and >99% of the isolates were sensitive to azithromycin. A slight increase in minimum inhibitory concentration (MIC) is noticed for ceftriaxone but current average MIC is 32-fold lower than the resistance cut-off. Over 99%, of the isolates exhibited decreased susceptibility to ciprofloxacin. Conclusions: Salmonella Paratyphi A has remained susceptible to most antibiotics, unlike Salmonella Typhi, despite widespread usage of many antibiotics in Bangladesh. The data can guide evidence-based policy decisions for empirical treatment of paratyphoid fever.

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Section: Resultsmentioning

confidence: 99%

23-year trends indicate low rates of antimicrobial resistance inSalmonellaParatyphi A

Sajib

Tanmoy

Hooda

et al. 2023

Preprint

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“…In 2020, a study conducted in Karachi found discordance in 10 (16.6%) out of 60 Salmonella isolates. 10 Another study conducted in India found discordance in 12 (12%) out of 100 isolates. 14 Similarly, in 2020 a study conducted in Karachi found discordance in 5 (0.23%) out of 2104 S. Typhi isolates.…”

Section: Discussionmentioning

confidence: 97%

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

Sultan,

Safdar,

Malik

et al. 2023

Infect Dis J Pak

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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

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“…Gradient strip methods, called the E-test, are preferable to the disk diffusion approach, as these methods measure MIC values and are more specific for reporting sensitivity. 19 Shoaib et al 10 indicated in a recent study from Karachi that the E-test could be a better choice than disk diffusion. In addition, few studies have reported problems with the E-test method.…”

Section: Discussionmentioning

confidence: 99%

“…9 The lack of antimicrobial stewardship with over-the-counter antibiotic availability contributes to increasing antimicrobial resistance in endemic regions. 10 As a result of widespread empiric use of AZM during the coronavirus disease 2019 pandemic, there is a growing risk of AZM resistance. 11 This misuse of antibiotics may lead to a complete lack of options for treating XDR typhoid.…”

Section: Introductionmentioning

confidence: 99%

Reporting of Azithromycin Activity against Clinical Isolates of Extensively Drug-Resistant Salmonella enterica Serovar Typhi

Jabeen

Saleem

Nizamuddin

et al. 2023

The American Journal of Tropical Medicine and Hygiene

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This study aimed to evaluate the minimum inhibitory concentration (MIC) of azithromycin (AZM) in clinical isolates of extensively drug-resistant (XDR) Salmonella Typhi (i.e., resistant to chloramphenicol, ampicillin, trimethoprim-sulfamethoxazole, fluoroquinolones, and third-generation cephalosporin) using the E-test versus the broth microdilution method (BMD). From January to June 2021, a retrospective cross-sectional study was carried out in Lahore, Pakistan. Antimicrobial susceptibility was performed initially by the Kirby-Bauer disk diffusion method for 150 XDR Salmonella enterica serovar Typhi isolates, and MICs of all the recommended antibiotics were determined by the VITEK 2 (BioMérieux) fully automated system using Clinical Laboratory Standard Institute (CLSI) 2021 guidelines. The E-test method was used to determine AZM MICs. These MICs were compared with the BMD, which is the method recommended by the CLSI but not adopted in routine laboratory reporting. Of 150 isolates, 10 (6.6%) were resistant by disk diffusion. Eight (5.3%) of these had high MICs against AZM by the E-test. Only three isolates (2%) were resistant by E-test, having an MIC of 32 μg/mL. All eight isolates had a high MIC by BMD with different MIC distributions, but only one was resistant, having an MIC of 32 μg/mL by BMD. The sensitivity, specificity, negative predictive value, positive predictive value, and diagnostic accuracy of the E-test method versus BMD were 98.65%,100%, 99.3%, 33.3%, and 98.6%, respectively. Similarly, the concordance rate was 98.6%, negative percent agreement was 100%, and positive percent agreement was 33%. The BMD is the most reliable approach for reporting AZM sensitivity in XDR S. Typhi compared with the E-test and disk diffusion methods. Potentially, AZM resistance in XDR S. Typhi is around the corner. Sensitivity patterns should be reported with MIC values, and if possible, higher values should be screened for the presence of any potential resistance genes. Antibiotic stewardship should be strictly implemented.

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Disc Diffusion Testing of Azithromycin Against Clinical Isolates of Typhoidal Salmonellae: A Diagnostic Conundrum

Cited by 5 publications

References 26 publications

23-year trends indicate low rates of antimicrobial resistance inSalmonellaParatyphi A

23-year trends indicate low rates of antimicrobial resistance inSalmonellaParatyphi A

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

Reporting of Azithromycin Activity against Clinical Isolates of Extensively Drug-Resistant Salmonella enterica Serovar Typhi

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