Currently microorganisms are best identified using 16S rRNA and 18S rRNA gene sequencing. However, in recent years matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) has emerged as a potential tool for microbial identification and diagnosis. During the MALDI-TOF MS process, microbes are identified using either intact cells or cell extracts. The process is rapid, sensitive, and economical in terms of both labor and costs involved. The technology has been readily imbibed by microbiologists who have reported usage of MALDI-TOF MS for a number of purposes like, microbial identification and strain typing, epidemiological studies, detection of biological warfare agents, detection of water- and food-borne pathogens, detection of antibiotic resistance and detection of blood and urinary tract pathogens etc. The limitation of the technology is that identification of new isolates is possible only if the spectral database contains peptide mass fingerprints of the type strains of specific genera/species/subspecies/strains. This review provides an overview of the status and recent applications of mass spectrometry for microbial identification. It also explores the usefulness of this exciting new technology for diagnosis of diseases caused by bacteria, viruses, and fungi.

MALDI-TOF mass spectrometry: an emerging technology for microbial identification and diagnosis.

Campylobacter is a leading foodborne bacterial pathogen, which causes gastroenteritis in humans. This pathogenic organism is increasingly resistant to antibiotics, especially fluoroquinolones and macrolides, which are the most frequently used antimicrobials for the treatment of campylobacteriosis when clinical therapy is warranted. As a zoonotic pathogen, Campylobacter has a broad animal reservoir and infects humans via contaminated food, water or milk. Antibiotic usage in both animal agriculture and human medicine, can influence the development of antibiotic-resistant Campylobacter. This review will describe the trend in fluoroquinolone and macrolide resistance in Campylobacter, summarize the mechanisms underlying the resistance to various antibiotics and discuss the unique features associated with the emergence, transmission and persistence of antibiotic-resistant Campylobacter. Special attention will be given to recent findings and emphasis will be placed on Campylobacter resistance to fluoroquinolones...

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Antibiotic resistance in Campylobacter: emergence, transmission and persistence.

A growing number of Campylobacter species other than C. jejuni and C. coli have been recognized as emerging human and animal pathogens. Although C. jejuni continues to be the leading cause of bacterial gastroenteritis in humans worldwide, advances in molecular biology and development of innovative culture methodologies have led to the detection and isolation of a range of under-recognized and nutritionally fastidious Campylobacter spp., including C. concisus, C. upsaliensis and C. ureolyticus. These emerging Campylobacter spp. have been associated with a range of gastrointestinal diseases, particularly gastroenteritis, IBD and periodontitis. In some instances, infection of the gastrointestinal tract by these bacteria can progress to life-threatening extragastrointestinal diseases. Studies have shown that several emerging Campylobacter spp. have the ability to attach to and invade human intestinal epithelial cells and macrophages, damage intestinal barrier integrity, secrete toxins and strategically evade host immune responses. Members of the Campylobacter genus naturally colonize a wide range of hosts (including pets, farm animals and wild animals) and are frequently found in contaminated food products, which indicates that these bacteria are at risk of zoonotic transmission to humans. This Review presents the latest information on the role and clinical importance of emerging Campylobacter spp. in gastrointestinal health and disease.

The clinical importance of emerging Campylobacter species

Treatment of food by specific ionizing radiations to improve microbiological safety and storability is one of the most extensively studied technology of the XXth century. However, much of the research has been carried out in laboratories and it is still relatively underutilized commercially. Its application potential is very diverse, from inhibition of sprouting of tubers and bulbs to production of commercially sterile food products. The safety of consumption and wholesomeness of irradiated food have been extensively studied in international cooperations. Numerous international expert groups set up jointly by the FAO, the IAEA and the WHO, or the Scientific Committee on Food of the European Commission concluded that foods irradiated with appropriate technologies are both safe and nutritionally adequate. A Codex General Standard for Irradiated Foods and a Recommended International Code of Practice for Radiation Processing of Food have been developed. Specific applications of food irradiation are approved by national legislations in over 55 countries worldwide. Commercial use of irradiation, however, is still limited. In spite of pioneering past R&D activities in Europe and North-America, the utilization of the process growing faster and increasingly, mainly for sanitary purposes, in fast-developing countries in the (South-East) Asian region and some Latin-American countries. Progress in the European Union is decidedly slower. In the EU, food irradiation is regulated since 1999 by a General Directive, but its implementing directive, the Community list of EU approved irradiated foods contains only a single class of items: “dried aromatic herbs, spices and vegetable seasonings”. This slow progress is mainly due to psychological and political factors, misinformation created by various activist groups, and the reluctance to implement the process by the industry is discouraged by such forces. The future of food irradiation will depend on an informed public and better understanding of the role the process can play in the control of food-borne pathogens.

History and future of food irradiation

Campylobacter 감염증과 그 예방

Occurrence of Escherichia coli O157:H7, Listeria monocytogenes, Salmonella and Campylobacter spp. on beef carcasses in Northern Ireland.

Prevalence of Campylobacter spp. in raw retail poultry on sale in Northern Ireland.

Prevalence of Campylobacter and Salmonella in raw chicken on retail sale in the republic of Ireland.

Aims: When isolating Campylobacter spp. from retail raw chicken using BS EN ISO 10272-1:2006, contaminants frequently cause overgrowth on mCCDA plates. Therefore, these organisms proliferate in the enrichment medium, Bolton broth, indicating a lack of selectivity in this medium. This study sought to characterize the contaminant flora and to devise a modified Bolton broth to inhibit their growth.



Methods and results:  Contaminants (n = 30) from separate samples were identified and antibiotic resistances determined. Most (93%) were extended spectrum β-lactamase (ESBL) producing Escherichia coli, able to hydrolyse the cefoperazone present in Bolton broth and mCCDA. To inhibit these organisms, original formulation Bolton broth was supplemented with potassium clavulanate, at three concentrations, and recoveries of campylobacters from raw chicken were determined. Using standard Bolton broth, only 49% of samples (n = 104) yielded campylobacters, but supplementation with 2 mg l−1 potassium clavulanate increased this significantly (P < 0·05), with 91% of samples positive.



Conclusions:  Potassium clavulanate can restore the selectivity of Bolton broth when isolating Campylobacter spp. from raw chicken.



Significance and Impact of the Study:  Raw chicken is often contaminated with the pathogen Campylobacter, but the ISO methodology for its detection is becoming compromised by the increasing presence of antibiotic-resistant bacteria. A simple modification ensures effective detection of this pathogen.

https://sfamjournals.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1472-765X.2011.03046.x

Restoring the selectivity of bolton broth during enrichment for campylobacter spp. from raw chicken

Preston broth and agar incubated at either 37 or 42°C have been widely used to isolate campylobacters from foodstuffs. The consequences of using either incubation temperature were investigated. Retail packs of raw chicken (n = 24) and raw lamb liver (n = 30) were purchased. Samples were incubated in Preston broth at 37 and 42°C and then streaked onto Preston agar and incubated as before. Two Campylobacter isolates per treatment were characterized. Poultry isolates were genotyped by random amplification of polymorphic DNA (RAPD), pulsed-field gel electrophoresis (PFGE), and flagellin PCR-restriction fragment length polymorphism, and lamb isolates were genotyped by RAPD only. In total, 96% of the poultry and 73% of the lamb samples yielded campylobacters. The lamb isolates were all Campylobacter jejuni, as were 96% of the poultry isolates, with the remainder being Campylobacter lari. The incubation temperature had no significant effect on the number of positive samples or on the species isolated. However, genotyping of the C. jejuni isolates revealed profound differences in the types obtained. Overall (from poultry and lamb), the use of a single incubation temperature, 37°C, gave 56% of the total number of RAPD C. jejuni genotypes, and hence, 44% remained undetected. The effect was especially marked in the poultry samples, where incubation at 37°C gave 47% of the PFGE genotypes but 53% were exclusively recovered after incubation at 42°C. Thus, the incubation temperature of Preston media selects for certain genotypes of C. jejuni, and to detect the widest range, samples should be incubated at both 37 and 42°C. Conversely, genotyping results arising from the use of a single incubation temperature should be interpreted with caution.

L. Moran

Papers

Occurrence of Escherichia coli O157:H7, Listeria monocytogenes, Salmonella and Campylobacter spp. on beef carcasses in Northern Ireland.

Prevalence of Campylobacter spp. in raw retail poultry on sale in Northern Ireland.

Prevalence of Campylobacter and Salmonella in raw chicken on retail sale in the republic of Ireland.

Restoring the selectivity of bolton broth during enrichment for campylobacter spp. from raw chicken

Effect of Incubation Temperature on Isolation of Campylobacter jejuni Genotypes from Foodstuffs Enriched in Preston Broth