Impact of erythromycin resistance on the virulence properties and fitness of Campylobacter jejuni Yassir A. Almofti, Menghong Dai, Yawei Sun, Hao Haihong, Zonghui Yuan * MOA Key Laboratory of Food Safety Evaluation, National Reference Laboratory of Veterinary Drug Residue (HZAU), Huazhong Agricultural University, Wuhan, Hubei 430070, PR China article info Article history: Received 5 December 2010 Received in revised form 23 February 2011 Accepted 25 February 2011 Available online 4 March 2011 Keywords: C. jejuni Ery-resistant mutant Virulence Fitness abstract Epidemiological studies of macrolide resistance in Campylobacter jejuni demonstrated that infections with macrolide-resistant C. jejuni could be associated with an increased risk of adverse events, devel- opment of invasive illness or death compared to macrolide-susceptible isolates. In this study, an in vitro induction experiment was conducted using susceptible C. jejuni strain and erythromycin as a selecting agent to obtain Ery-resistant mutant with 23S rRNA gene mutation (A2074C). Changes in the virulence characteristics and fitness between the susceptible parent strain and Ery-resistant mutant were exam- ined. Ery-resistant mutant demonstrated slightly more resistance to bile in the bile tolerance assay compared to the susceptible strain but with no statistical significant difference. However Ery-resistant mutant apparently demonstrated reduced adhesion and invasion characteristics to intestinal epithelial cells, murine macrophage and short time intracellular survivability within macrophage compared to the susceptible strain. Co-inoculation of the two strains in the mice resulted in low colonization level of the resistant strain compared to the susceptible strain. Competition experiments resulted in mutant that grew significantly slower than the susceptible parent strain and the mutation imposed a fitness cost in Ery-resistant mutant. Taken together these findings demonstrated the increment of the virulence characteristics of Ery-susceptible strain rather than Ery-resistant strain. The adverse events previously observed in the epidemiological studies for macrolide-resistant strains infection, we suggested this maybe attributed to the resistivity of the resistant strains to the treatment and consequently prolonged the symptoms and compromised the disease in patients. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Campylobacter , especially Campylobacter jejuni, comes up on top of the principal bacterial agents that currently considered as the leading cause of human bacterial gastroenteritis [1]. Human gastroenteritis caused by Campylobacter infection largely attributed to the consumption of contaminated or undercooked food and is mostly often a self-limiting diarrheal illness where patients do not usually require antimicrobial treatment. Nevertheless severe and prolonged gastroenteritis required antimicrobial treatment. In such cases macrolides and quinolones are the drugs of choice [2]. In severe cases the most notable post-infection complication of campylobacteriosis is the development of Guillain-Barré syndrome, acute ascending bilateral paralysis [3]. Macrolides inhibit bacterial growth by binding to ribosomes and interfering with the bacterial protein synthesis. They bind to the 50S ribosomal subunit, causing blockage of transpeptidation and/or translocation [4]. Macrolide resistance in C. jejuni occurs mainly through chro- mosomal target gene mutation, particularly 23S rRNA gene point mutations (A2075G, A2074C, A2074G) [5]. Furthermore an efflux pump system (CmeABC) plays a significant role in Campylobacter multidrug resistance and extrusion of antibiotics, bile and dyes [6]. Recently modifications in ribosomal proteins L4 and L22 were reported to act synergistically with CmeABC to confer macrolide resistance in Campylobacter [7]. Resistance to clinically important antimicrobial agents, partic- ularly macrolides and fluoroquinolones, is increasing among Campylobacter isolates but few studies have explored the human health consequences of such resistance. Despite wealthy informa- tion about the adverse events associated with antimicrobial drug resistance in Salmonella infections [8e10], limited information exists on the clinical consequences of resistance in Campylobacter infection. Data supporting an increase in virulence of drug-resistant isolates of C. jejuni are starting to emerge and epidemiological studies have examined the clinical impact of antibiotic resistance in * Corresponding author. Tel.: þ86 27 87287186; fax: þ86 27 87672232. E-mail address: yuan5802@mail.hzau.edu.cn (Z. Yuan). Contents lists available at ScienceDirect Microbial Pathogenesis journal homepage: www.elsevier.com/locate/micpath 0882-4010/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.micpath.2011.02.009 Microbial Pathogenesis 50 (2011) 336e342