Contamination of broiler chickens by Staphylococcus aureus during processing; incidence and origin

Distribution of staphylococcal enterotoxin genes among Staphylococcus aureus isolates from poultry and humans with invasive staphylococcal disease

Food poisoning by Staphylococcus aureus affects hundreds of thousands of people each year. Staphylococcus aureus also causes invasive diseases such as arthritis (in poultry) and septicemia (in poultry and humans). Foodborne disease is caused by the ingestion of a staphylococcal enterotoxin (SE). Enterotoxin has also been associated with other S. aureus illnesses in humans and domestic animals. In this study, polymerase chain reaction was used to detect the staphylococcal enterotoxin genes, SEA, SEB, SEC, SED, and SEE, in S. aureus isolates associated with invasive disease in poultry and humans. In the 34 poultry isolates, only one isolate was found to contain a SE gene, sec. In the 41 human isolates, over 51% tested positive for an SE gene with 12.2% positive for the gene for SEA, 2.4% for SEB, 22% for SEC, 24.4% for SED, and 0 for SEE. The disparity between the rates for SE gene(s) in poultry and human isolates suggests a lesser role for the enterotoxins in invasive poultry disease than in human disease.

Microbiological quality of retail poultry carcasses in Spain

A total of 40 eviscerated and refrigerated chicken carcasses were collected from five retail outlets (three supermarkets and two poulterers' shops) in León (Spain). The level of microorganisms on chicken carcasses was assessed using the excised breast-skin technique. Mean counts (log10 CFU/g) of psychrotrophs, pseudomonads, fluorescent pseudomonads, enterococci, Micrococcaceae, Staphylococcus aureus, and yeasts and molds were 4.84, 4.11, 3.32, 2.72, 3.80, 3.67, and 2.99, respectively. A significant correlation coefficient was found between pseudomonads and fluorescent pseudomonad counts (r = 0.827; P < 0.001) and between Micrococcaceae and S. aureus counts (r = 0.915; P < 0.001). Levels of psychrotrophs, pseudomonads, fluorescent pseudomonads, and yeasts and molds were significantly (P < 0.05) higher in supermarkets than in poulterers' shops, possibly due to the longer period of time the carcasses spent in the supermarkets (between 1 and 2 days, as opposed to only 4 to 16 h in the case of poulterers' shops). Carcasses from poulterers' shops showed higher (P < 0.05) counts of enterococci. Micrococcaceae, and S. aureus, which suggests higher storage temperatures in these outlets. Only S. aureus counts (especially those from poulterers' shops) exceeded the established values in the microbiological criteria for poultry meat consulted.

Probes and polymerase chain reaction for detection of food-borne bacterial pathogens

DNA-hybridization and the polymerase chain reaction (PCR) are techniques commonly used to detect pathogenic bacteria. In this paper, the use of these techniques for detection of Salmonella, E. coli, V. cholerae, non-O1 Vibrio, Yersinia enterocolitica, Campylobacter, Listeria monocytogenes, Staphylococcus aureus, Bacillus cereus, Clostridium perfringens, and C. botulinum is reviewed with emphasis on application in food microbiology. In food control, DNA-techniques have most often been used in a 'culture confirmation' fashion, i.e. bacteria are enriched and sometimes even purified by traditional culture procedures and thereafter identified by the use of DNA-based methods. The most desirable approach is, however, to detect organisms directly in the food, but major problems remain to be solved before this can be routinely performed.

Numerical taxonomy of an 'atypical' population of gram-positive cocci isolated from freshly dressed lamb carcasses

One hundred Gram-positive, catalase-positive strains were isolated from freshly dressed lamb carcasses. They were randomly selected from a non-selective medium and tested for 75 characters. Only nine cultures could be identified by conventional methods. A numerical taxonomic study was conducted on the whole population and 25 reference strains. At the 80% similarity level (Ssm), ten clusters were formed. Five of them were entirely composed of reference strains. Phena V and VIII contained seven isolates and two reference strains of Micrococcus. Phena VI (six unidentified isolates), VII (nine staphylococci) and IX (69 unidentified isolates) were more related to M. kristinae than to the remaining reference strains. Properties with possible implications in meat spoilage were: strong lipolytic activity (76%), anaerobic growth (85%), tolerance to 15% (w/v) NaCl (95%) and ability to grow at 15 degrees C (95%) and 4 degrees C (26%).

Existing and emerging foodborne diseases

Foodborne diseases, i.e. illnesses due to contaminated food, are one of the most widespread problems of the contemporary world. They are toxic or infectious by nature and are caused by agents which enter the body through the ingestion of contaminated food or water. These agents can be chemical like pesticide residues and toxic metals or biological like pathogenic microorganisms. Foods contaminated by biological agents are, however, the major cause of foodborne disease. Data recorded in different countries show that the incidence of some of these diseases has increased dramatically over the past few years, but because of under-reporting the data are of limited value and cannot be compared between countries. In most countries, individual cases of illness are usually not reported. A sentinel surveillance system, started as a pilot study in the Netherlands, was shown to be feasible for the registration of some foodborne infections. Based on this study, it can be estimated that each year Salmonella and Campylobacter cause respectively about 12,000 and 25,000 cases of acute enteritis per million. Case-control studies clearly implicate poultry products as an important source of acute enteritis. New developments in food production and changing trends in food consumption lead to the emergence of new hazards. Additionally, because the population is aging and there has been an increase in the number of individuals with underlying diseases, the state of public health is deteriorating. Campylobacter, Salmonella enteritidis and enterohemorrhagic Escherichia coli are examples of microorganisms that have the opportunity to increase as a consequence of intensive husbandry. Listeria monocytogenes is an example of an organism that causes disease in immunosuppressed individuals.

Differentiation of Staphylococcus aureus from freshly slaughtered poultry and strains 'endemic' to processing plants by biochemical and physiological tests

A comparison was made of 27 'endemic' strains of Staphylococcus aureus and 35 strains from freshly slaughtered birds, isolated at five commercial slaughterhouses processing chickens or turkeys. Of 112 biochemical and physiological tests used, 74 gave results which differed among the strains. Cluster analysis revealed several distinct groupings which were influenced by strain type, processing plant and bird origin; these included a single group at the 72% level of similarity containing most of the 'endemic' strains. In comparison with strains from freshly slaughtered birds, a higher proportion of 'endemic' strains produced fibrinolysin, alpha-glucosidase and urease and were beta-haemolytic on sheep-blood agar. The 'endemic' type also showed a greater tendency to coagulate human but not bovine plasma, and to produce mucoid growth and clumping. The last two properties, relevant to colonization of processing equipment, were less evident in heart infusion broth than in richer media or process water collected during defeathering of the birds.

Bacteriological quality of broiler carcasses as affected by in-plant lactic acid decontamination

In an attempt to improve the bacteriological quality of broiler carcasses the bactericidal effect of treatments with 1% and 2% lactic acid was investigated. Bacterial colonisation was determined immediately after treatment, after the carcasses had been chilled and during storage at 0 degrees C. Examination included numbers of mesophilic aerobic and psychrotrophic aerobic colony-forming units (CFU), CFU of Enterobacteriaceae at 37 degrees C and CFU of Staphylococcus aureus. Immediately after treatment colonisation per gram skin was generally reduced by about 1 log. Initially 2% lactic acid was not found significantly more effective in reducing colony counts than 1%. However, treatment with 2% lactic acid suppressed post-decontamination colonisation with Enterobacteriaceae more effectively than 1% lactic acid, as determined after 15-18 days storage at about 0 degrees C. Lactic acid treatment was most effective when applied shortly before chilling. Successive treatment at three different stages during slaughtering did not increase reduction of colony counts. It is concluded that decontamination with 1-2% lactic acid at pH 2, when applied shortly before chilling, will markedly improve the bacterial safety and increase the refrigerated shelf life of broiler carcasses.

Gordon memorial lecture. Poultry disease and public health

The development of the poultry industry and the consumption of poultry meat is traced over the past quarter of a century and related to the increased incidence of food poisoning in man. Factors affecting the spread of the main poultry pathogens which are of human significance are discussed. The pathogens considered are salmonella, campylobacter, staphylococci and clostridia. Various preventative measures are considered including rearing procedures for poultry, decontamination methods and education of the public. It is concluded that one of the most effective measures is irradiation of poultry and poultry products. The difficulties of introducing this control measure are recognised. It is concluded that more effective application of existing control methods would greatly reduce the hazards to public health.

Bacteriological quality assurance (BQA) of mechanically deboned meat (MDM)

Adequacy of bacteriological quality assurance during the commercial production of mechanically deboned meat (MDM) was assessed. Lax standards of hygiene during production were observed, resulting in high numbers of Staphylococcus aureus, viz. 10(4) to 10(5) cfu g(-1), and severe contamination with Enterobacteriaceae: 10(5) to 10(6) cfu g(-1). These data indicate that measures of hygiene observed during boning of carcasses and during collection, storage and transport of bones or poultry parts should be markedly tightened, while conditions of refrigerated storage of raw materials and MDM should be improved. Use of bones of poor sensory quality (discoloration, abnormal smell) generally resulted in MDM of inferior bacteriological quality. Phage typing, biotyping and assessment of enterotoxin production was carried out with 136 St. aureus cultures, isolates from mechanically deboned pork produced at one plant. Fifty-five per cent of the isolates was not typable, 28% was typable with human phages, 8% with bovine phages. The majority of the strains could not be explicitly assigned to any Meyer and/or Hájek and Marŝálek types. Applying the simplified system of Devriese to eighteen strains isolated in our investigation, ten were found to belong to the poultry ecovar, one to the bovine ecovar, while seven strains were non-host specific. None of the isolates produced enterotoxins A-E. Microbiological inspection of end products is recommended as part of an integrated quality assurance system. The following reference values for the final product (maximal colony counts to be expected under GMP conditions expressed as 95th percentile) were calculated: Pig MDM: log(10) mesophilic colony count 6·8 and log(10) cfu mesophilic Enterobacteriaceae g(-1) 4·8; Poultry MDM: log(10) mesophilic colony count 6·6 and log(10) cfu mesophilic Enterobacteriaceae g(-1) 4·7.

Plasmids of Staphylococcus aureus associated with live and processed poultry

A series of 23 strains of Staphylococcus aureus originally isolated from processed poultry was screened for the presence of plasmids. Plasmids were more common in strains of Staph. aureus characteristically associated with live poultry than with strains endemic in poultry plants and strains of human origin. Two plasmids with sizes of 1.65 and 18.2 kilobase pairs (kBp) were present in three strains considered typical of Staph. aureus forma specialis 'altilis' and two plasmids with sizes of 1.65 and 17 kBp were present in three of four strains of Staph. aureus var. gallinae. A 1.65 kBp plasmid was present in all seven strains of these poultry biotypes and in three of 14 'endemic' strains. All the 1.65 kBp plasmids were shown by blot hybridization to share sequence homology. There was also some sequence homology between the 18.2 kBp and 17 kBp plasmids. These results were supported by restriction enzyme digest analyses. A study of cured derivatives of strain PS221 f.sp. 'altilis' suggested that the 18.2 kBp plasmid encoded the genetic determinant(s) responsible for caseolysis. Both the 1.65 and the 18.2 kBp plasmids also exerted an effect on the production of acid from lactose. In no other characteristic did cured strains resemble the plasmid-free 'endemic' strains. This was therefore consistent with the notion that the genetic determinants associated with the cultural characteristics of endemic strains are chromosomally located.

Incidence and properties of Staphylococcus aureus associated with turkeys during processing and further-processing operations

The incidence of Staphylococcus aureus on turkeys sampled at various stages of processing and further-processing was determined on four occasions at each of three different processing plants. For freshly-slaughtered birds, counts from neck skin varied from plant to plant over the range less than 10(2) to greater than 10(5)/g but in all cases the corresponding counts obtained from carcasses sampled after chilling rarely exceeded 10(3)/g and the same was true for samples of mechanically recovered meat (MRM), the final raw product examined. Despite the limited susceptibility of isolates from the different factories to typing by means of either standard human or poultry bacteriophages (55-94% untypable), evidence was obtained with the aid of biotyping for the presence of both human and animal-derived strains. However, some biotypes isolated from MRM were not detected at earlier stages of processing. At one processing plant, an "indigenous' type of S. aureus was clearly demonstrated. It occurred in high numbers in the defeathering machines (up to 10(5)/swab), was found on carcasses at all subsequent stages of processing over the survey period and was shown to survive routine cleaning and disinfection procedures. Isolates of this type produced unusually large amounts of extracellular "slime' in artificial culture. Two of the three processing plants yielded isolates which were enterotoxigenic. Of 55 strains from Plant 1, 60% produced enterotoxin C and all were of the "indigenous' type. In the case of Plant 2, only two type D- and one type F-producing strain were found.