Characteristics of Organisms and Type of Illness These “arc-shaped” bacteria, fi rst observed in veterinary specimens, were designated species of a distinct genus in 1991 (Vandamme et al., 1991), offi cially separating them from the closely related species of the genus Campylobacter, with which they share a relatively common background of sources, characteristics, and illness manifestations in humans and animals. Together with Campylobacter spp., they are placed in the family Campylobacter-aceae. Seven species have been identifi ed: A. butzleri (thought to be the primary human pathogen), A. cryaerophilus hybridization groups 1A and 1B, A. skirrowii, A. nitrofi gilis (Houf et al., 2000), A.
cibarius (Houf et al., 2005), A. halophilus (Donachie
With the exception of A. nitrofi gilis, the organisms have been isolated from water (surface and drinking water), sewage, raw foods (including poultry [chickens, ducks, and turkeys], beef, and pork), ready-to-eat poultry, chicken fl ocks, humans and animals with enteritis, and aborted animal fetuses (Wesley, 1996).
Isolation rates of up to 43% from porcine abortions have been reported. One study found the distribution of Arcobacter spp. in porcine abortions in the United States to be A. butzleri at 8%, A. cryaerophilus 1A at 16%, and A. cryaerophilus 1B at 60% (Harmon and Wesley, 1997). They are also a part of the indigenous fl ora of healthy animals. Antigenically identical strains have been recovered from diseased and healthy animals, underlining the possibly opportunistic role of Arcobacter spp. in disease under suitable conditions.
Their role in the causation of disease is underlined by higher isolation rates from aborted fetuses and cases of porcine infertility than from healthy animals (Ellis et al., 1977). A. cryaerophilus has been associated with cases of infectious abortion in cattle herds in Germany (Wesley, 1994).
Son et al. (2007) sampled 325 broiler carcasses during a three-month period in 2004, at the prescalding, prechilling, and postchilling steps of a commercial poultry operation. Arcobacter recovery rates were highest in prescalded carcasses (96.8%) compared to prechilled (61.3%) and postchilled carcasses (9.6%). A. butzleri was found to be the most prevalent species in 79.1% of the samples, followed by A. cryaerophilus 1B (18.6%) and A.
cryaerophilus 1A (2.3%). A skirrowii was not isolated in this study. A total of 71.8% of Arcobacter isolates showed multiple antimicrobial resistance. A total of 125 (89.9%) of A. butzleri isolates showed resistance to clindamycin, 114 (82%) to azithromycin, and 33 (23.7%) to nalidixic acid.
The disease can be acquired from travel in developing areas/countries, unhygienic food prepara-tion practices and environmental condiprepara-tions, cross-contamination, and person-to-person contact. In vivo studies have suggested the potential virulence of A.
butzleri (Wesley et al., 1996; Musmanno et al., 1997).
The presence of Arcobacter spp. in seafood and raw milk remains unknown. Tertiary treatment of sewage effl uent with 2 ppm chlorine dioxide removes 99.9%
of Arcobacter spp. (Stampi et al., 1993).
Surveys of cattle have detected Arcobacter spp. in 10.52% of dairy cattle fecal samples (Wesley, 1997).
Wesley et al. (2000) studied the shedding of Campy-lobacter and Arcobacter spp. in the feces of dairy cattle in various U.S. states and found 14.3% to be positive for Arcobacter. Analysis of farm management practices revealed that feeding of alfalfa and use of individual waterers protected the cattle from infection with et al., 2005), and A. sulfi dicus (Wirsen et al., 2002).
Campylobacter, Helicobacter, Wolinella, and Arco-bacter spp. make up the rRNA superfamily VI of the epsilon class of Proteobacteria. Arcobacter spp. are gram-negative, mesophilic, aerotolerant, nonsporing rods and have been known to cause gastritis (rarely bac-teremia or appendicitis) in humans and abortions, mastitis, and gastritis in livestock (Wesley, 1994). Infec-tions with these organisms cause economic losses in livestock herds and compromise human health.
Since these organisms are relatively metabolically inert, tests used in their identifi cation include those used to identify Campylobacter spp. Defi nitive bio-chemical tests used to identify Arcobacter and distin-guish between the species are limited and somewhat unreliable. They include growth temperature, cata-lase activity, nitrate reduction, fatty acid analysis, hydrolysis of indoxyl acetate, growth in the presence of glycine or sodium chloride, growth on MacConkey agar, the inability to hydrolyze hippurate, and cadmium chloride susceptibility (Wesley, 1994). Other tests suggested include arylsulfatase and pyrazinamidase activities and susceptibility to polymyxin B, since in contrast to Campylobacter strains, Arcobacter strains are negative for all three tests (Burnens and Nicolet, 1993). Susceptibility to antimicrobial agents has also been used to characterize this genus (Kiehlbauch et al., 1992). Molecular and nucleic acid-based tech-niques, using genus- and species-specifi c DNA probes complementary to the highly conserved 16S rRNA molecule or the glyA gene, have proven to be more reliable means of identifi cation and distinction for Arcobacter (and between Campylobacter and Arco-bacter) species. Plasmid analysis (with a plasmid detection rate of 33% for Arcobacter spp.) has also been used, along with biochemical tests and antimi-crobial resistance patterns, for epidemiological typing (Harrasset al., 1998).
Sources and Incidence in the Environment and Foods
Limited studies have been conducted globally on the prevalence of these organisms. This, together with the fact that classical laboratory testing is geared toward the detection of thermophilic Campylobacter spp. (Bolton et al., 1992), allowing Arcobacter spp.
to possibly go undetected, makes the determination of the accurate prevalence of the genus a study in sta-tistical extrapolation.
Lammerding et al. (1996) postulated that the genus has a signifi cant reservoir in poultry products.
Its presence in red meat animals has also been docu-mented. Consequently, containment of intestinal contents and fecal material will limit the spread of this emerging pathogen in farm animal operations.
a slightly higher radiation resistance than that of Campylobacter jejuni. A z value of 8.1 was reported for exponential phase A. butzleri cells (Hilton et al., 2001).
Lactic and citric acids at concentrations of 0.5, 1, and 2% were found to be inhibitory to the growth in culture of A. butzleri, with citric acid being more effective (Phillips, 1999). Nisin (500 IU/ml) was inhibitory, while sodium citrate was more effective than sodium lactate. Low levels of sodium tripoly-phosphate can prevent growth (0.016%) and sur-vival (0.02%) of A. butzleri (D’Sa and Harrison, 2005).
Hancock (2000) studied the effects of spices on A. butzleri in vitro and in spice marinades on fresh pork loins. Cinnamon aquaresin (1.56%) and cinna-mon oleoresin (3.13%) were the most inhibitory to the two strains of A. butzleri studied. Pimento leaf essential oil (3.13%), barbeque spice aquaresin, and clove aquaresin also inhibited growth at 6.25%.
In the marination study, pimento leaf essential oil (6%) reduced A. butzleri populations by 1.37 and 2.11 logs over 2 and 5 days, respectively. Cinnamon aquaresin (3%) reduced A. butzleri levels by 1.03 and 1.34 logs over the same time span.
Hancock (2000) also studied the effi cacy of organic acids, both in vitro and sprayed onto fresh pork loins inoculated with A. butzleri. Acetic acid, citric acid monohydrate, and lactic acid were inhibi-tory to A. butzleri strains studied in vitro, at less than 0.5%. On pork loins, A. butzleri populations were reduced by 0.87 log10 using 4% lactic acid. Organic acid concentration and type signifi cantly affected the effectiveness of antimicrobial activity. Inclusion of both spices and organic acids as “hurdle” compo-nents, in combination with other means of reducing these bacterial species on food, was suggested.
Due to the lower rate of recovery of Arcobacter from red meats that have a reduced surface moisture level, it has been postulated that the genus is sensitive to the effects of ambient drying (Nachamkin and Bla-ser, 2000). The organism is also cold sensitive and may be sublethally injured at lower temperatures.
Heat resistance studies have shown that recom-mended temperatures for safe cooking of foods should be suffi cient to kill Arcobacter spp. (D’Sa and Harrison, 2005; USDA/FSIS, 2007).
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the Pathogens
Cervenka et al. (2008) found that cinnamalde-hyde, followed by thymol, carvacrol, caffeic acid, tannic acid, and eugenol, was inhibitory in vitro against three strains of A. butzleri, two strains of A. cryaerophilus, and one strain of A. skirrowii.
Arcobacter. Thus, feed and dietary supplements may alter gut homeostasis, infl uencing microbial colonization.
Intrinsic and Extrinsic Factors That Affect Survival and Growth in Food Products and Contribute
to Outbreaks
Campylobacter spp. have been identifi ed as the leading cause of bacterial food-borne diarrheal illness in humans (CDC, 2001). It has been postulated that some of these campylobacters may be misidentifi ed Arcobacter spp. Given the high incidence of Campy-lobacter spp. in raw poultry and in the environment and the ability of arcobacters to grow at mesophilic temperatures (as low as 15°C), it is possible that Arcobacter spp. are also signifi cant contributors to the global incidence of diarrheal illness. In 1983, A. butzleri was the only pathogen isolated from an outbreak of diarrheal illness in Italian schoolchildren (Vandamme et al., 1993). A few other cases of A. butzleri in hospitalized patients who responded to antibiotics and in which A. butzleri was isolated as the sole pathogen, point to the pathogenic and inva-sive capacity of the organism (D’Sa, 2002). Lior sero-group 1 predominates in samples of food and from patients with illness.
In a study carried out by D’Sa (2002) using four human isolates of A. butzleri and two human isolates of A. cryaerophilus, it was determined that the pH growth range for these isolates was 5.5 to 8.0. The optimum pH range for A. butzleri strains was 6.0 to 7.0 and for A. cryaerophilus strains was 7.0 to 7.5.
The effect of NaCl on growth and survival of the genus was variable, with upper growth limits of 3.5 and 3.0% for A. butzleri and A. cryaerophilus, respectively. Survival at NaCl concentrations up to 5% was noted at 25°C for some Arcobacter strains.
Calculated z values ranged from 5.20 to 6.28°C. The species studied were found to be cold sensitive, eluci-dated by the fact that a mild heat treatment followed by cold shock acted synergistically to produce a large reduction in cell numbers.
Food Processing Operations That Infl uence the Numbers, Spread, or Characteristics The same food processing and handling practices that are recommended to reduce Campylobacter problems should control problems that could be asso-ciated with Arcobacter species. There have been a few studies focused on the inhibition or elimination of Arcobacter in foods.
Low doses of irradiation (1.5 to 4.5 kGy) were found to be suffi cient to eliminate the presence of A. butzleri in ground pork, as it was found to possess
facilitate adherence, cecropins that limit the growth of competing microfl ora, and a P-type adenosine-triphosphatase. The organism attaches to gastric mucosa and using various factors, including its own LPS, causes mucosal injury. Following gastric coloni-zation, an infl ammatory reaction is induced that initiates a cascade of reactions, resulting in the recog-nizable symptoms of infection. H. pylori also alters normal gastric secretion. Patients with duodenal ulcers have an elevated serum gastrin level that results in increased gastric acid levels. Asymptomatic H. pylori infections are frequent. The relatively inaccessible microenvironment of the organism during infection makes treatment challenging. Metronidazole-clarithro-mycin antibiotic combinations have been used com-monly to treat infections, along with proton pump inhibitors like ranitidine bismuth citrate. Under adverse conditions, the species has been known to produce viable but noncultivable forms that retain infective capacity (Bode et al., 1993). It has been suggested that invasion of gastric epithelial cells could be a mechanism of infection and persistence in the occurrence of H. pylori disease (Petersen and Krog-felt, 2003).
The organisms are gram-negative, fastidious, microaerophilic, nonsporing, spiral, motile (with polar fl agella), curved rods (Hill, 1997) that grow optimally at 35 to 37°C but not at 25°C. The optimal NaCl con-centration for growth is 0.5 to 1% (Jiang and Doyle, 1998). Addition of 0.05% ferrous sulfate and 0.05%
sodium pyruvate optimized the growth of H. pylori strains in broth (Jiang and Doyle, 2000). They are sensitive to acid but are protected from the effects of gastric acidity in their mucosal microenvironment.
Noncultivable cells have been detected in the oral cavity and in feces and may be signifi cant in the assess-ment of the routes of transmission of the organism.
Sources and Incidence in the Environment and Foods
A defi nitive source of the organisms is unknown (Hill, 1997), and there is no established link to zoonotic transmission (Martin and Penn, 2001).
Food-borne transmission has been postulated by sev-eral authors but not defi nitively proven. Water (both surface and municipal) may also be linked to trans-mission (Gomes and De Martinis, 2004a). Studies have demonstrated the ability of H. pylori to survive in water globally (Bellack et al., 2006).
The incidence of H. pylori infection in developed countries (0.3 to 0.5%) was found to be on the decline. The organism is acquired mainly during childhood and primarily by the fecal-oral, oral-oral, and iatrogenic routes. Higher infection rates are Discriminative Detection Methods for Confi rmation
and Trace-Back of Contaminated Products Multiplex PCR assays, PCR-restriction fragment length polymorphism assays, and combined PCR-en-zyme-linked immunosorbent assays targeting both the 16s and 23s rRNA regions have been developed and tested as a means of identifi cation and distinction of Arcobacter spp. (Wesley et al., 1995; Cardarelli-Leite et al., 1996; Harmon and Wesley, 1997; Mar-shall et al., 1999; Winters and Slavik, 2000; Antolin et al., 2001). Use of selective and enrichment media is necessary to increase the rate of isolation of Arco-bacter spp. from food, environmental, and patient samples (D’Sa, 2002).
Concluding Remarks
There is still uncertainty as to the signifi cance of the threat posed by members of the genus Arcobacter.
While there have been food-borne illness cases linked to foods contaminated with species of Arcobacter, their frequency has been sporadic to date. Whether this is related to the clinical and laboratory methods used, which might overlook species of Arcobacter or misidentify them as Campylobacter, is unknown.
Considering the similarities of many of the character-istics of the genera Arcobacter and Campylobacter, it is reasonable to consider species of Arcobacter poten-tial food-borne hazards. While the two genera are frequently found on similar foods and share many growth and survival traits, they also are controlled by the same food handling and processing practices.
HELICOBACTER
Characteristics of Organism and Type of Illness Helicobacter pylori, fi rst isolated in 1983, is the type species and most well-known species of this genus. It has been the target of intensive study because of its link to human illness, especially peptic ulcers, chronic gastritis, and stomach cancer, including mucosa-associated lymphoid tissue lymphoma (Hardin and Wright, 2002). It colonizes stomach walls, is present on the gastric mucosal layer of carriers, is recognized as the major cause of peptic ulcer disease globally, and is one of the most common bacterial infections in humans (Suerbaum and Michetti, 2002). The genus Helicobacter was created in 1989 and includes about 23 recognized species. Taxonomically, these are placed in the epsilon class of Proteobacteria.
H. pylori infections require an array of bacterial and host factors; signifi cant among these are fl aA and fl aB (genes coding for fl agellin), urease (which alters the gastric microenvironment), specifi c adhesins that
consumption of raw, contaminated food (fruits and vegetables) and postprocess contamination of foods are believed to be possibilities in the food-borne transmission of the organism.
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Pathogen
Gancz et al. (2008) showed that increasing NaCl concentrations altered cell growth, morphology, survival, and virulence factor expression of H. pylori, with some strain differences observed. Tabak et al.
(1999) tested the effects of cinnamon extracts (ethanol based and methylene chloride based) on growth and urease activity of H. pylori. It was determined that the methylene chloride-based extract inhibited H. pylori growth at the concentration of commonly used antibiotics (15 to 50 µg/ml), while the ethanol extract inhibited urease activity.
Discriminative Detection Methods for Confi rmation and Trace-Back of Contaminated Products The organism is diffi cult to grow in culture (Suerbaum and Michetti, 2002). Methods used to diagnose infection include histological examination of tissues obtained during endoscopy, culture, PCR-based techniques, breath-testing for urease during active infection, serological tests, stool antigen assays, restriction length polymorphism analysis, and identi-fi cation of H. pylori in feces, saliva, and dental plaque (Gomes and De Martinis, 2004b). Neubauer and Hess (2006) developed a multiplex PCR procedure that would detect and distinguish Helicobacter pul-lorum in poultry and poultry products.
Concluding Remarks
Transmission of H. pylori through foods leading to incidences of food-borne illness has been speculated but not demonstrated to date. There is evidence that the bacterium can survive on some types of foods, but the lack of evidence linking illness due to the organ-ism to food products would indicate that the typical route of exposure to H. pylori is not food related.
Helicobacter also appears to possess no outstanding survival characteristics that would be of concern when applying typical food processing and handling practices.