Antimicrobial susceptibility of bacterial isolates from clinical specimens in four Pacific Island countries, 2017-2021

Abstract

Background: There are limited antimicrobial resistance (AMR) surveillance data from low- and middle-income countries, especially from the Pacific Islands region. AMR surveillance data is essential to inform strategies for AMR pathogen control.

Methods: We performed a retrospective analysis of antimicrobial susceptibility results from the national microbiology laboratories of four Pacific Island countries - the Cook Islands, Kiribati, Samoa and Tonga - between 2017 and 2021. We focused on four bacteria that have been identified as 'Priority Pathogens' by the World Health Organization: Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa.

Findings: Following deduplication, a total of 20,902 bacterial isolates was included in the analysis. The most common organism was E. coli (n = 8455) followed by S. aureus (n = 7830), K. pneumoniae (n = 2689) and P. aeruginosa (n = 1928). The prevalence of methicillin resistance among S. aureus isolates varied between countries, ranging from 8% to 26% in the Cook Islands and Kiribati, to 43% in both Samoa and Tonga. Ceftriaxone susceptibility remained high to moderate among E. coli (87%-94%) and K. pneumoniae (72%-90%), whereas amoxicillin + clavulanate susceptibility was low against these two organisms (50%-54% and 43%-61%, respectively). High susceptibility was observed for all anti-pseudomonal agents (83%-99%).

Interpretation: Despite challenges, these Pacific Island laboratories were able to conduct AMR surveillance. These data provide valuable contemporary estimates of AMR prevalence, which will inform local antibiotic formularies, treatment guidelines, and national priorities for AMR policy.

Funding: Supported by the National Health and Medical Research Council.

Keywords: Antibiotic resistance; Antimicrobial; Bacteriology; Epidemiology; Pacific islands; Public health surveillance.

Fig. 1

Map of Pacific Island countries and territories, Australia and New Zealand. Source: Shutterstock/frees. Reproduced with permission of Shutterstock. W&F = Wallis and Futuna.

Fig. 2

Antimicrobial susceptibility in the Cook Islands by calendar year. AMC = amoxicillin + clavulanate. CAZ = ceftazidime. CIP = ciprofloxacin. CHL = chloramphenicol. CLI = clindamycin. CRO = ceftriaxone. ERY = erythromycin. FOX = cefoxitin. GEN = gentamicin. MEM = meropenem. NIT = nitrofurantoin. SXT = sulfamethoxazole + trimethoprim. TCY = tetracycline. Open circles indicate any years when <70% of isolates were tested against that antimicrobial, otherwise closed circles are used. Asterisks indicate years when n < 30 isolates were tested against that antimicrobial. FOX is used to determine MRSA status. NIT only tested against urinary E. coli isolates.

Fig. 3

Antimicrobial susceptibility in the Cook Islands by patient location.∗p < 0.05. ∗∗p < 0.01. ∗∗∗p < 0.001. AMC = amoxicillin + clavulanate. CAZ = ceftazidime. CIP = ciprofloxacin. CHL = chloramphenicol. CLI = clindamycin. CRO = ceftriaxone. ERY = erythromycin. FOX = cefoxitin. GEN = gentamicin. MEM = meropenem. NIT = nitrofurantoin. SXT = sulfamethoxazole + trimethoprim. TCY = tetracycline.

Fig. 4

Antimicrobial susceptibility in Kiribati by calendar year. AMC = amoxicillin + clavulanate. CAZ = ceftazidime. CIP = ciprofloxacin. CHL = chloramphenicol. CLI = clindamycin. CRO = ceftriaxone. ERY = erythromycin. FOX = cefoxitin. GEN = gentamicin. MEM = meropenem. NIT = nitrofurantoin. SXT = sulfamethoxazole + trimethoprim. TCY = tetracycline. Open circles indicate any years when <70% of isolates were tested against that antimicrobial, otherwise closed circles are used. Asterisks indicate years when n < 30 isolates were tested against that antimicrobial. FOX is used to determine MRSA status. NIT only tested against urinary E. coli isolates.

Fig. 5

Antimicrobial susceptibility in Samoa by calendar year. AMC = amoxicillin + clavulanate. CAZ = ceftazidime. CIP = ciprofloxacin. CHL = chloramphenicol. CLI = clindamycin. CRO = ceftriaxone. ERY = erythromycin. FOX = cefoxitin. GEN = gentamicin. MEM = meropenem. NIT = nitrofurantoin. SXT = sulfamethoxazole + trimethoprim. TCY = tetracycline. Open circles indicate any years when <70% of isolates were tested against that antimicrobial, otherwise closed circles are used. FOX is used to determine MRSA status. NIT only tested against urinary E. coli isolates.

Fig. 6

Antimicrobial susceptibility in Samoa by patient location. ∗p < 0.05. ∗∗p < 0.01. ∗∗∗p < 0.001. AMC = amoxicillin + clavulanate. CAZ = ceftazidime. CIP = ciprofloxacin. CHL = chloramphenicol. CLI = clindamycin. CRO = ceftriaxone. ERY = erythromycin. FOX = cefoxitin. GEN = gentamicin. MEM = meropenem. NIT = nitrofurantoin. SXT = sulfamethoxazole + trimethoprim. TCY = tetracycline.

Fig. 7

Antimicrobial susceptibility in Tonga by calendar year. AMC = amoxicillin + clavulanate. CAZ = ceftazidime. CIP = ciprofloxacin. CHL = chloramphenicol. CLI = clindamycin. CRO = ceftriaxone. ERY = erythromycin. FOX = cefoxitin. GEN = gentamicin. MEM = meropenem. NIT = nitrofurantoin. SXT = sulfamethoxazole + trimethoprim. TCY = tetracycline. Open circles indicate any years when <70% of isolates were tested against that antimicrobial, otherwise closed circles are used. Asterisks indicate years when n < 30 isolates were tested against that antimicrobial. FOX is used to determine MRSA status. NIT only tested against urinary E. coli isolates.

Fig. 8

Overall antimicrobial susceptibility by country, 2017–2021. AMC = amoxicillin + clavulanate. CAZ = ceftazidime. CIP = ciprofloxacin. CHL = chloramphenicol. CLI = clindamycin. CRO = ceftriaxone. ERY = erythromycin. FOX = cefoxitin. GEN = gentamicin. MEM = meropenem. NIT = nitrofurantoin. SXT = sulfamethoxazole + trimethoprim. TCY = tetracycline. Bars with lighter shading indicate when <70% of isolates were tested against that antimicrobial.