Food as a potential vector for antibiotic resistances. 2: Relevance of lactic acid bacteria

Transfer of antibiotic resistances via the food chain is possible through the ingestion of resistant parts of the original food microflora. Lactic acid bacteria (especially glycopeptide resistant enterococci) are considered as important vectors because of their ability to transfer resistances by genetic mechanisms. Therefore a literature review and own investigations concerning the incidence and the resistance profile of enterococci from fresh meat were performed. The isolates harboured in part resistances relevant for human medicine. However, they could be isolated only sporadically and could not be demonstrated quantitatively in most cases. The resistance profile differed from those of human clinical origin. These results were confirmed by other authors. Additionally other investigators could prove molecular differences compared to clinical strains. Therefore food can only be considered as a vector if resistance transfer from food isolates to pathogenic microorganisms is possible. Such a transfer could be shown only in very low frequencies. In conclusion so far lactic acid bacteria cannot be considered as the main source for the incidence of antibiotic resistances in man.     

Nosocomial infections and bacterial antibiotic resistance in a university equine hospital

A base-line study of bacteria isolated from horses admitted to the Veterinary Medical Teaching Hospital during a 6-month period was performed to determine the extent of multiresistant nosocomial infections caused by gram-negative aerobic bacteria other than Salmonella spp. Results of this study indicated that 21.9% of the 105 horses from which cultures and sensitivities were available had developed nosocomial gram-negative aerobic infections, with high rates of resistance to gentamicin, kanamycin, and trimethoprim sulfadiazine, three of the most often prescribed antibiotics in this hospital. In addition, a prospective study of antibiotic-resistant bacteria of fecal origin was performed to determine whether there was a change in the degree of antibiotic resistance of a horse's intestinal flora while the horse was hospitalized. Bacterial culturing for gram-negative lactose fermenting bacteria was done on fecal specimens collected directly from the rectum on day 1 and day 7 of a horse's hospitalization. Susceptibility testing was done on each isolant. Of the 24 paired fecal specimens obtained, Escherichia coli and Klebsiella sp isolated on day 7 were resistant to a significantly higher number of antibiotics than day 1 isolants (P = 0.003, P = 0.043, respectively).     

Nematospiroides dubius as a vector for Salmonella typhimurium.

Salmonella typhimurium within the 3rd stage larvae of Nematospiroides dubius was shown to infect mice, evidenced by prolonged shedding of salmonellae in the feces. Numbers of S typhimurium needed to infect mice were approximately 1,000- fold less if incorporated within the 3rd-stage larvae of N dubius. Results of these experiments demonstrate that nematode parasites may act as a vector for pathogenic species of enteric bacteria.     

Evaluation of Rhipicephalus sanguineus as a potential biologic vector of Ehrlichia platys

The brown dog tick, Rhipicephalus sanguineus (Acari: Ixodidae), transmits several diseases among dogs including Ehrlichia canis infection. The role of Rhipicephalus sanguineus as a biologic vector for E platys, the rickettsial agent of infectious canine cyclic thrombocytopenia, was studied in dogs. Laboratory-cultured, pathogen-free nymph ticks were fed to repletion on dogs acutely infected with E platys. Tick engorgement coincided with the development of initial parasitemia and thrombocytopenia in the infected dogs. Following repletion, nymph ticks were allowed to molt under controlled conditions. One-month-old E platys-exposed adult ticks failed to infect naive dogs in animal transmission studies. The presence of E platys was not detected in midguts or salivary glands of similarly exposed adult ticks by use of light and transmission electron microscopy. These studies indicate that R sanguineus may not transmit E platys infection.     

A modified method for the detection of antibiotic residues in slaughter animals.

Biological methods in current use for the detection of antibiotic residues in slaughter animals are reviewed. A modified method is suggested in which the conditions for the control have been standardized. By the use of a semi-defined medium, the batch-to-batch variations are minimized. In order to facilitate the detection of sulfonamides the medium is supplemented with trimethoprim. The standardized conditions included the use of a sporulating organism, Bacillus subtilis, an inoculum size of 0.5 × 10⁵ spores per ml medium, and 5 ml medium of pH 6.0 per plate. A preincubation-diffusion time of 1 h in room temperature is recommended before incubation.The modified method was compared with the currently prescribed Swedish method. The new method was easier to perform and showed a more uniform sensitivity to most of the antibiotics used.     

Pet birds as potential reservoirs of virulent and antibiotic resistant zoonotic bacteria

Bacterial pathogens carried by pet birds are considered a risk for birds, workers, and pet owners. This study investigated the potential of pet birds as reservoirs for virulent multidrug-resistant (MDR) zoonotic bacteria and assessed the genetic relatedness and diversity of bacterial isolates from pet birds and human contacts. Cloacal and tracheal swabs from 125 pet birds and 70 hand swabs from human contacts were collected. The results revealed that the pet birds were reservoirs for Escherichia coli, Klebsiella pneumoniae (17.6 %, each), and Staphylococcus aureus (15.2 %). These isolates were also identified in their human contacts, at percentages of 14.3 %, 12.9 %, and 24.3 %, respectively. Virulence associated genes were identified from E. coli (stx2, stx2f, eaeA, and hlyA), K. pneumoniae (fimH, TraT, and magA), and S. aureus (PVL, hly, sea, sed genes) isolates. Multidrug-resistant E. coli, K. pneumoniae, and S. aureus were highly prevalent (81.3 %, 90.3 %, and 61.1 %, respectively). The genetic relationship between the E. coli and K. pneumoniae isolates from the pet birds and human contacts were determined by ERIC-PCR, while, RAPD-PCR was used for the S. aureus isolates. ERIC-PCR was found to have the highest discriminatory power. The clustering of the isolates from the pet birds and human contacts indicated potential transmission between the birds and workers. In conclusion, pet birds could act as potential reservoirs for zoonotic bacterial pathogens; thus, posing a risk to their human contacts.     

Glucagon as a potential therapy for ketosis and fatty liver.

An experiment demonstrating the usefulness of glucagon as a treatment for fatty liver and ketosis in early-lactation dairy cows has been described. This is the first report of the ability of glucagon, or any agent, to promote clearance of lipid from livers of animals suffering hepatic lipidosis. The development and use of glucagon as a therapeutic agent for the fatty-liver complex in dairy cows may provide a powerful management tool to enhance the profitability of the high-producing dairy cow.     

Salmonella infections in finishing pigs in The Netherlands: bacteriological herd prevalence, serogroup and antibiotic resistance of isolates and risk factors for infection.

Salmonellae are wide spread in man and animals world wide and are of increasing significance as causative agents of foodborne diseases in man. The European Union, national authorities and the pig industry are therefore more and more interested in the Salmonella status of the pig population. The aim of this study was to estimate the bacteriological prevalence of Salmonella in finishing pig herds, the serogroup and the resistance to antibiotics of the isolated Salmonellae and a preliminary risk analysis of factors associated with infection. For this, 317 finishing pig herds were randomly selected from a database containing 1500 herds in the southern part of the Netherlands. In each herd 24 samples of fresh faeces were collected from two compartments with pigs close to market weight. Per compartment 12 samples of faeces were pooled into one pooled sample. Pooled samples were cultured in duplicate. Salmonella spp. were recovered from 71 out of 306 herds (23%) in which two compartments could be sampled. A total of 108 isolated Salmonella's were serotyped: 71 serogroup B, 3 serogroup C1, 6 serogroup C2, 22 serogroup D1, and 6 isolates neither serogroup B, C or D1. Of a total of 115 Salmonella isolates tested, none were resistant to colistin, enrofloxacin, flumequin or gentamicin. Automated liquid feeding of by-products, and membership of an Integrated Quality Control (IQC) production group were associated with a decreased risk of infection, while use of trough feeding was associated with an increased risk of infection. It is necessary to test these presumed risk factors in intervention studies to evaluate their potency to reduce the Salmonella prevalence in finishing pigs and thereby reduce the risk of Salmonellosis in people consuming pork.     

仔猪致病性大肠杆菌的分离鉴定与耐药性分析

由湛江市3个养猪场采集到40份仔猪黄痢、白痢腹泻粪便样品,共分离到40株大肠杆菌,其中7株是致病性大肠杆菌,三个猪场致病性大肠杆菌的分离率分别为15.4%、10%和43%。对7株致病性大肠杆菌进行药物敏感性试验,结果表明:它们均对恩诺沙星、菌必治和丁胺卡那霉素敏感,而对复方新诺明、阿莫西林、氨苄青霉素、四环素和庆大霉素的耐药率为100%,对氯霉素、头孢氨苄和痢特灵的耐药率为85.7%,对卡那霉素和链霉素的耐药率为57.1,%对氟哌酸和环丙沙星的耐药率为14.3%。猪场选用较敏感药物来防治仔猪大肠杆菌病,使疫病得到了有效控制。     

Development of a polymerase chain reaction assay for the detection of antibiotic resistance genes in community DNA.

Many methods are used to detect antibiotic resistance genes in samples. The objective of the study reported here was to compare polymerase chain reaction (PCR) analysis of community DNA with fecal culturing for detecting antibiotic resistance genes in cattle samples. In the laboratory-based portion of this study, known concentrations of an Escherichia coli strain with 3 antibiotic resistance genes (cmy-2, flo, and cat) were added to feces from dairy cattle. These genes were used to assess the effect of various primer pairs, chromosomally versus plasmid-encoded genes, and gene copy number on the sensitivity of PCR amplification. Gene-specific PCR amplification was performed on the community DNA extracted from the feces. Feces were cultured for the inoculated strain. In the field-based portion of the study, 80 cattle fecal samples of unknown gene status were compared by use of similar methods. Culture and PCR amplification from community DNA extractions produced variable results, and this variability was most noticeable at dilutions that approached the detection limit of the assay. Typically, PCR amplification had a higher sensitivity than did culture for detecting the gene of interest. However, the sensitivity of culture was improved by plating on selective media containing antibiotics. The community DNA approach enables assessment of bacterial communities in complex samples such as feces, a task that can be prohibitive by budget or time constraints associated with culture methods. Through a strategic combination of culture and community DNA approaches, the relationship between specific selection pressures and the persistence and dissemination of specific resistance genes can be elucidated.     

Incidence and antibiotic resistance of Salmonella spp. in ground turkey meat

1.?The objectives of this study were to isolate Salmonella spp. by conventional culture technique from ground turkey samples, to determine the seasonal distribution of Salmonella spp., to verify the isolates by PCR using primers based on oriC gene sequence, and to determine the antibiotic susceptibility profiles of the isolates. A total of 240 packaged fresh ground turkey samples marketed in Ankara were analysed between July 2004 and June 2005.

2.?One hundred and ten out of 240 (45?8%) samples were positive for Salmonella spp. and confirmed by PCR. The distribution of Salmonella spp. was determined as 48?3, 55?0, 63?3 and 16?6%, during spring, summer, autumn and winter, respectively. Statistical analysis showed a significant difference for the prevalence of Salmonella spp. between winter and the other seasons.

3.?Of the isolates, 54 out of 110 (49?0%) were resistant to one or more antibiotics tested. The highest resistance was observed to nalidixic acid (25?4%), followed by streptomycin (17?2%) and tetracycline (15?4%).

4.?In conclusion, this is a disturbing finding, both for the high prevalence of Salmonella and the extent of antibiotic resistance. Ground turkey should be produced under suitable hygienic and technological conditions and the use of antimicrobials must be controlled by governmental agencies to protect public health from salmonellosis and from the consequences of increased resistance to the antibiotics.     

Livestock manure as a vector for parasites--a report of experiences

Analysing the results of own investigations and informations in literature a review is given about the role of manure specially in stables of high-intensity cattle and pig production as a vector for exogenic parasite stages. In the course of investigations--in most cases simulating practice conditions--so-called indicator germs were used as test material. In cattle stables manure is significant as a vector for Eimeria species, Cryptosporidium parvum, Sarcocystis species, Taenia saginata and Fasciola hepatica. In pig stables manure must be classified as a reservoir of infections with Toxoplasma gondii, Sarcocystis species and Ascaris suum; moreover it represents a favourable culturing medium for stable flies. Possibilities to overcome the problems are discussed under parasitological field of view.     

Development of a monitoring program for antibiotic resistance in bacteria from Swiss food-producing animals

Resistant bacteria from food-producing animals may compromise the success of antibiotic treatment in animals and in humans. Therefore, the level of antibiotic resistance in bacteria from farm animals and its development over time needs to be monitored. In Switzerland, a monitoring program for antibiotic resistance is currently being developed. Pilot-monitoring programs were conducted in selected animal species in order to obtain current data on antibiotic resistance. The data on the prevalence of bacteria and antibiotic resistance in poultry were used to optimize the sampling plan. The influence of sampling more farms compared to sampling more animals per farm on the prevalence estimate for antibiotic resistance was analyzed by a Monte Carlo simulation model. Accounting for the costs for sample collection, transportation and laboratory analysis of the samples, the number of samples to be taken at the respective step in the production line was optimized. Optimization was defined as maximizing the precision of the prevalence estimate while minimizing the costs. The model will be expanded to other bacterial and animal species in the future.     

The determination of hemoglobin and myoglogin residues as a parameter for testing heat exposure in back bacon.

The use of an extraction of the heme pigments hemoglobin and myoglobin as a test for the heat exposure of back bacon was investigated by treating back bacon at varying temperatures of 50-70 degrees C and times of two to 180 minutes and observing the effect on the absorbance of heme pigment residue after nitrite oxidation. Absorbance at 409 nm was used in place of the more usual 540 nm to provide greater sensitivity in the detection of heme. A decrease in residual heme pigments was time-dependent, particularly at lower temperatures. In view of this factor and the complex nature of the heat exposure of a large block of back bacon, the application of this test would require a calibration of each process. Alternatively, limits to the amounts of heme pigment residue could be set. The heme pigment test is useful in its simplicity and overcomes difficulties associated with the coagulation and enzyme tests.