Abstract
The current global crisis of antimicrobial resistance (AMR) among important human bacterial pathogens has been amplified by an increased resistance prevalence. In recent years, a number of studies have reported higher resistance levels among Listeria monocytogenes isolates, which may have implications for treatment of listeriosis infection where resistance to key treatment antimicrobials is noted. This study examined the genotypic and phenotypic AMR patterns of 100 L. monocytogenes isolates originating from food production supplies in Australia and examined this in the context of global population trends. Low levels of resistance were noted to ciprofloxacin (2%) and erythromycin (1%); however, no resistance was observed to penicillin G or tetracycline. Resistance to ciprofloxacin was associated with a mutation in the fepR gene in one isolate; however, no genetic basis for resistance in the other isolate was identified. Resistance to erythromycin was correlated with the presence of the ermB resistance gene. Both resistant isolates belonged to clonal complex 1 (CC1), and analysis of these in the context of global CC1 isolates suggested that they were more similar to isolates from India rather than the other CC1 isolates included in this study. This study provides baseline AMR data for L. monocytogenes isolated in Australia, identifies key genetic markers underlying this resistance, and highlights the need for global molecular surveillance of resistance patterns to maintain control over the potential dissemination of AMR isolates.
Highlights
Listeria monocytogenes is a foodborne pathogen and the causative agent of the human infection, listeriosis
L. monocytogenes may be classified into genetic lineages [43]
There currently exists insufficient breakpoint documentation required for Minimum Inhibitory Concentration (MIC) interpretation, impeding standardised 4ave established breakpoints for ampicillin, benzylpenicillin, erythromycin, meropenem, penicillin, and Trimethoprim-sulfamethoxazole only [54,55]
Summary
Listeria monocytogenes is a foodborne pathogen and the causative agent of the human infection, listeriosis. Invasive listeriosis has a high fatality rate of 20–30% [4]. It is characterised by invasion of the central nervous system, blood, or placenta, causing symptoms such as meningitis, encephalitis, and septicaemia [5]. Those with increased susceptibility include the immunocompromised, elderly, pregnant women, and newborn children. L. monocytogenes is of additional concern to pregnant women as it has the ability to translocate into the placenta causing perinatal infection, miscarriage, and stillbirth [6,7]
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