The plasmidome of multidrug-resistant emergent Salmonella serovars isolated from poultry

The rapid emergence of resistant bacteria is occurring worldwide. The understanding of the dissemination of antimicrobial resistance using high-throughput sequencing and bioinformatics approaches is providing valuable insights into the genetic basis of the horizontal gene transfer and the emergence of the antibiotic resistance threat. This ultimately can offer vital clues to the development of coordinated efforts to implement new policies to continue fighting against bacterial infections. The poultry microbiota is characterized as a potential reservoir of resistance genes, mostly derived from the Enterobacteriaceae which have become increasingly important in human and animal infections. In this work, complete genome sequences were achieved for four multidrug-resistant Salmonella spp. isolated from poultry from different farms in Brazil. We identified highly similar IncHI2-ST2 megaplasmids (larger than 275.000 bp) in all Salmonella isolates studied. These megaplasmids carry a resistome comprised of eleven different resistance genes (aac(6′)-Iaa, aadA1b, aph(4)-Ia, aph(6)-Id, aph(3″)-Ib, aph(3′)-Ia, aac(3)-Iva, sul1, tetA, tetB and dfrA1b) and four heavy metal tolerance operons (telluride, mercury, silver and copper). In conclusion, the multidrug-resistant plasmids identified in S. enterica serovar Schwarzengrund and Newport isolated from poultry show a variety of antibiotic resistance and heavy metal tolerance genes, providing advantages for the bacteria to survive under extremely unfavorable conditions.     

Representative Salmonella serovars isolated from poultry and poultry environments in Saudi Arabia

The authors describe the source and prevalence of pathogenic Salmonella serovars among poultry farms in Saudi Arabia. A total of 1,052 (4%) Salmonella isolates were recovered from 25,759 samples of poultry (broilers, layers, broiler breeders and layer breeders) and poultry environments (box liner, litter, drag swab, droppings, mice and feed) were examined bacteriologically between 1988 and 1997 at the Poultry Disease Laboratory at the National Agriculture and Water Research Center in Riyadh. Eleven Salmonella serogroups representing 38 different Salmonella serovars were identified by means of antigenic analysis. The majority of the 276 isolates (26.2%) of Salmonella typed, were recovered from liver, heart and intestines of the broilers and layers. The most prominent Salmonella serogroups isolated were as follows: serogroup C1 (392 isolates, 37.26%), B (289 isolates, 27.47%) and D1 (269 isolates, 25.69%). However, untypable and multiple serogroups were also encountered, the most frequent isolates serotyped belonged to groups C1 (97 isolates, 24.7%), D1 (86 isolates, 31.9%), and B (71 isolates, 24.6%). Salmonella Enteritidis (85 isolates, 98.8%), Salmonella Virchow (48 isolates, 57.8%), Salmonella Paratyphi B var. Java (41 isolates, 57.7%) and Salmonella Infantis (30 isolates, 20.6%) were distributed the most widely as all were encountered in poultry and in poultry environments. S. Enteritidis phage type 4 (30 isolates, 35.3%), was the phage type most frequently detected among group D1 phage types, while 39 (45.8%) of the isolates of S. Enteritidis could not be phage typed.     

Virus isolations from sewage and from a stream receiving effluents of sewage treatment plants

In order to detect viruses in sewage or streams, it is first necessary to concentrate the virus present in the fluid sample. Available methods are not readily manageable for concentrating virus from large volumes of fluid, and have not always yielded high recovery rates. In the study described in this paper, a method for concentration of viruses by adsorption on insoluble cross-linked maleic anhydride polyelectrolytes has been utilized to survey the viral flora of sewage and of a stream receiving sewage effluents, in a residential area of Houston, Texas. On a single day the virus flow at different points along the stream varied from 304 000 to 6 014 000 PFU/min. From 84 samples each of 1 US gal, 14 520 isolates were obtained, chiefly echovirus type 7 and polioviruses of all 3 types, some of them with characteristics of virulent wild strains. With virus isolation rates as high as those achieved, it is now possible to monitor virus in natural waters more effectively.     

Use of ciprofloxacin to control a Salmonella outbreak in a long-stay psychiatric hospital.

An outbreak of diarrhoea due to Salmonella virchow phage type 8 occurred in a major block of a large psychiatric hospital. The two other major blocks of the hospital remained unaffected. No source of infection was identified and the epidemiological investigations pointed to cross-infection as the mode of transmission. Infection control measures were implemented at an early stage but a total of 55 patients and four members of staff were affected. The disease was self-limiting and of short duration. During the course of the outbreak, Salmonella typhimurium phage type 66 also emerged as a pathogen and was isolated from the stools of symptomatic cases with diarrhoea. Owing to the size of the hospital, the lack of facilities for infection control, the nature of the patients' illnesses and an increasing number of affected patients, it was decided to treat all symptomatic and asymptomatic patients with oral ciprofloxacin 500 mg twice daily for 7 days. A quantitative stool culture for salmonellae was undertaken on days 3, 7, 10, 30, 60 and 90 from the start of treatment. All patients' and staff's stool cultures became negative on day 7 and remained negative for a period of 6 months during follow-up. We conclude that cross-infection outbreaks due to Salmonella spp. in psychiatric and geriatric hospitals can be controlled by isolation in a designated ward and supportive therapy, together with ciprofloxacin treatment.     

Routes for Campylobacter contamination of poultry meat: epidemiological study from hatchery to slaughterhouse

From April 1998 to March 2000, 18 broiler flocks were followed from the hatchery to the slaughterhouse. Campylobacter was not found in the hatchery, 1-day-old chicks or in the rearing house before the arrival of the chicks. The infection of broiler flocks increased continuously during the rearing time, with a total of seven positive flocks at the end of rearing. Farms with Campylobacter-positive broilers were characterized by the circulation of Campylobacter in the environment (puddles, dung hill) and on the footwear of the farmer. The administration of antibiotics did not significantly reduce Campylobacter shedding. With the exception of one flock during rearing and a few flocks in the slaughterhouse with a mixed Campylobacter coli-Campylobacter jejuni infection, C. jejuni exclusively was found both during rearing and on the carcasses. A significant correlation exits between the contamination of the broilers during rearing and the carcasses after processing. No slaughterhouse was able to avoid contamination of carcasses when status-positive animals were delivered. Moreover, six negatively delivered flocks yielded positive carcasses, the result of a supplementary contamination, which occurred during transport and slaughtering.     

Genetical relationship between R plasmids derived from Salmonella and Escherichia coli obtained from a pig farm, and its epidemiological significance

A total of 475 Salmonella strains belonging to 5 serovars, isolated from a pig farm which had been heavily contaminated with Salmonella for the past 2 years were tested for antibiotic susceptibility and detection of R plasmids. Thirty-three Escherichia coli isolates from the same farm were also examined in a similar way. Out of 475 strains 348 (73.2%) were resistant to one or more antibiotics such as tetracycline (Tc), streptomycin (Sm), sulfadimethoxine (Su), chloramphenicol (Cm) and kanamycin (Km), and 247 (85.2%) out of 290 strains belonging to 3 serovars examined harboured conjugative R plasmids. There was no change in the pattern of drug resistance during this survey nor any variation in the pattern of resistance of R plasmids, whatever the serovar. The antibiogram pattern Tc Sm Su, mainly S. typhimurium, was common among Salmonella strains. Among the transferred resistance patterns, the thermosensitive R plasmids conferring the Tc marker detected in this study were Fi-, and belonged to incompatibility group H1, whereas the R plasmids conferring Sm Su resistances which coexisted in the same host were Fi+, and compatible with the reference R plasmids tested. The I alpha plasmid conferring Cm resistance alone was isolated from S. anatum and the FII plasmid conferring Sm Km resistances was also isolated from S. typhimurium. In contrast, the 33 E. coli strains examined were resistant to three or five antibiotics and most of the resistance markers were located on conjugative R plasmids. I alpha plasmids conferring Cm resistance alone or FII plasmids conferring Cm or Km markers were common in the E. coli strains. H1 and H2 plasmids conferring multiple resistance markers were also found in them. The genetic properties of R plasmids derived from Salmonella or E. coli strains are compared, and the potential spread of R plasmids between strains of Salmonella and E. coli is discussed.     

Routes for salmonella contamination of poultry meat: epidemiological study from hatchery to slaughterhouse

Data were collected on the prevalence of salmonella at different stages during the life cycle of 18 broiler flocks on different farms as well as during slaughter in different poultry slaughterhouses. For the isolation of salmonella, the highest sensitivity (93.9%) was obtained by enrichment in the semi-solid agar Diasalm. The 'overshoe method' utilizing several pairs of overshoes provided the highest sensitivity for determining the salmonella status of the broilers during rearing. A clear decrease of the relative importance of the first production stages was demonstrated for the salmonella contamination of the end product, whereas horizontal transmission of salmonella to broilers during rearing and to broiler carcasses in the slaughterhouse was shown to be the main determinative factor. Ten of the 18 flocks received a salmonella positive status with the highest shedding occurring during the first 2 weeks of rearing. The shedding of the animals was significantly negatively influenced by the use of subtherapeutic or therapeutic doses of antibiotics. The intake of portable material in the broiler house was identified as the most important risk factor for horizontal transmission. Significant associations were found between the contamination level of a flock and hygiene of the broiler house, feed and water in the broiler house and both animal and non-animal material sampled in the environment. No correlation was found between contamination during the rearing period and contamination found after slaughtering. The presence of faecal material in the transport crates and predominantly the identity of the slaughterhouse seemed to be the determining factors for carcass quality. Improved hygiene management during transport of broilers and in some slaughterhouses could significantly reduce the risk of salmonella contamination of poultry meat.     

Genetical relationship between R plasmids derived from Salmonella and Escherichia coli obtained from a pig farm, and its epidemiological significance.

A total of 475 Salmonella strains belonging to 5 serovars, isolated from a pig farm which had been heavily contaminated with Salmonella for the past 2 years were tested for antibiotic susceptibility and detection of R plasmids. Thirty-three Escherichia coli isolates from the same farm were also examined in a similar way. Out of 475 strains 348 (73.2%) were resistant to one or more antibiotics such as tetracycline (Tc), streptomycin (Sm), sulfadimethoxine (Su), chloramphenicol (Cm) and kanamycin (Km), and 247 (85.2%) out of 290 strains belonging to 3 serovars examined harboured conjugative R plasmids. There was no change in the pattern of drug resistance during this survey nor any variation in the pattern of resistance of R plasmids, whatever the serovar. The antibiogram pattern Tc Sm Su, mainly S. typhimurium, was common among Salmonella strains. Among the transferred resistance patterns, the thermosensitive R plasmids conferring the Tc marker detected in this study were Fi-, and belonged to incompatibility group H1, whereas the R plasmids conferring Sm Su resistances which coexisted in the same host were Fi+, and compatible with the reference R plasmids tested. The I alpha plasmid conferring Cm resistance alone was isolated from S. anatum and the FII plasmid conferring Sm Km resistances was also isolated from S. typhimurium. In contrast, the 33 E. coli strains examined were resistant to three or five antibiotics and most of the resistance markers were located on conjugative R plasmids. I alpha plasmids conferring Cm resistance alone or FII plasmids conferring Cm or Km markers were common in the E. coli strains. H1 and H2 plasmids conferring multiple resistance markers were also found in them. The genetic properties of R plasmids derived from Salmonella or E. coli strains are compared, and the potential spread of R plasmids between strains of Salmonella and E. coli is discussed.     

Instability of multiple drug resistance plasmids in Salmonella typhimurium isolated from poultry

Plasmids in five strains of Salmonella typhimurium resistant to ampicillin, chloramphenicol, gentamicin, neomycin/kanamycin, streptomycin, sulphonamides, tetracyclines and trimethoprim (ACGKSSuTTm), CGKSSuTTm, ACSSuT or CSSuT which had been isolated from poultry in the first 3 months of 1989 have been characterized and compared with plasmids in two strains of R-types ACGKSSuTTm and ASSuTTm isolated from two patients later in the year. With the exception of the human isolate of R-type ASSuTTm, all strains carried two non-conjugative plasmids, one coding for SSu and belonging to incompatibility group Q, and a second coding for multiple resistance and belonging to the FIme incompatibility group. The human isolate of R-type ASSuTTm did not carry the IncQ SSu plasmid but like the poultry isolates, carried a non-conjugative FIme plasmid. Restriction endonuclease digestion with the enzymes EcoR I, Pst I and Hind III demonstrated that the FIme plasmids from strains of different R-types showed a high degree of homology but exhibited numerous fragment size polymorphisms. The restriction digest fingerprint of plasmids in the human isolate of R-type ACGKSSuTTm was indistinguishable from a poultry isolate of the same R-type. Analysis of segregants of one of the poultry isolates of R-type ACGKSSuTTm demonstrated that resistance determinants could be rapidly lost from the FIme plasmid to give rise to a number of R-types and fingerprint patterns. Loss of tetracycline resistance from this plasmid appeared to be correlated with the integration of other plasmid-mediated resistances into the bacterial chromosome. Evidence is presented for the rapid loss of antimicrobial resistance determinants from a multiple resistance plasmid of the FIme incompatibility group in response to withdrawal of antibiotic selective pressure.     

Prevalence and antimicrobial resistance of Salmonella isolated from meat and meat products in Algiers (Algeria)

This study was conducted in order to estimate the proportion of raw meat and processed meat products contaminated by Salmonella in the region of Algiers, Algeria, to identify serovars and to determine the antimicrobial resistance patterns of isolates. Out of the total 314 samples (144 of raw red meat and meat products, 128 of raw poultry meat and poultry products, and 42 of processed meat products) collected from various retail outlets, 61 (19.43%) were tested positive for Salmonella. The most significant occurrences were recorded for the categories of red meat (23.61%, n=34) and poultry (17.97%, n=23). Among the 64 isolates recovered, 21 different serovars were identified and two strains were nontypable. The most prevalent serovars were Salmonella Anatum (14.6%, n=9), Salmonella Altona (12.50%, n=8), Salmonella Corvallis (7.81%, n=5), Salmonella Enteritidis (7.81%, n=5), and Salmonella Typhimurium (7.81%, n=5). Sixty-two Salmonella isolates were tested for their susceptibility to 32 selected antimicrobial agents. Fifty-six (90.32%) isolates were resistant to at least one antimicrobial, of which 20 (32.26%) showed multidrug resistance. Resistance to sulphonamides (87.10%, n=54) was the most common. Resistance rates were lower to nalidixic acid (16.13%, n=10), streptomycin (16.13%, n=10), and tetracycline (12.90%, n=8), while resistance to pefloxacin was estimated at 4.84% (n=3). Fourteen different resistance patterns were observed. The "ACSSuT" pentaresistance pattern was observed in three of the Salmonella Typhimurium strains. The obtained results show that these foodstuffs are a potential source of antimicrobial-resistant Salmonella for human infections.     

Molecular epidemiology and in vitro antimicrobial susceptibility of Salmonella isolated from poultry in Kashmir

A total of 480 samples, comprising 429 faecal samples from healthy adult birds and 51 tissue samples from dead birds, were collected from four government poultry farms in the Kashmir valley from September 2007 to April 2008. In all, 33 Salmonella isolates were obtained. Of these, 28 (84.85%) isolates were Salmonella Gallinarum, 3 (9.09%) were Salmonella Enteritidis and the remaining 2 (6.06%) were Salmonella Typhimurium. All the isolates harboured the invA, sefA, stn and spvC virulence-specific genes. However, the sopB gene was found in only 90.9% of the isolates. Pulsed-field gel electrophoresis analysis of representative isolates revealed that the majority were related but a few belonged to different clones. The majority of the isolates were resistant to cefpodoxime, nalidixic acid and sulphadiazine and sensitive to chloramphenicol, cefotaxime and tetracycline. Isolation of multidrug-resistant Salmonella, including the zoonotically important serovars, revealed a potential threat not only to poultry but also to human health in Kashmir.     

Molecular characterization and antibiotic resistance profiling of Salmonella isolated from retail Turkey meat products

Contaminated poultry meat has been identified as one of the principal foodborne sources of Salmonella. Molecular characterization of Salmonella is important in addressing methods to control this pathogen. Seventy-four retail turkey meat samples were collected from various stores in Fargo, North Dakota in the fall of 2003. Salmonella was recovered from 30 samples using the standard conventional culture method (FSIS, USDA). Isolated Salmonella were characterized by serotyping, pulsed-field gel electrophoresis (PFGE) analysis, plasmid analysis, and antibiotic resistance profiling. Five serotypes were identified among the isolates: Newport (n = 12), Hadar (n = 8), Heidelberg (n = 7), 4,12:nonmotile (n = 2), and Reading (n = 1). XbaI PFGE analysis revealed 13 PFGE types and succeeded in grouping the isolates according to their serotypes. Plasmid profiling identified 5 plasmid types (with 1 or 2 plasmids) among eleven isolates that harbored plasmids. Seventeen isolates were resistant to antibiotics. The Heidelberg serotype showed resistance to multiple antibiotics: 1 isolate had resistance to gentamicin, sulfamethoxazole, and streptomycin, and 6 isolates had resistance to tetracycline, gentamycin, sulfamethoxazole, kanamycin, and streptomycin. The Hadar serotype isolates were resistant to 2 or 3 antibiotics: tetracycline and streptomycin (1 isolate); tetracycline and kanamycin (1 isolate); and tetracycline, kanamycin, and streptomycin (6 isolates). The 4,12:nonmotile serotype isolates showed resistance to tetracycline only. The Newport and the Reading serotypes were susceptible to all 16 of the antimicrobials tested.     

Plasmid analysis of Salmonella enteritidis isolated from human gastroenteritis cases and from epidemiologically associated poultry flocks.

Plasmid analysis of Salmonella enteritidis isolates from human gastroenteritis cases and from two commercial egg-producing poultry flocks was performed to determine if the poultry flocks were the source of the human infections. The plasmid profile and restriction fragment pattern (fingerprint) of five S. enteritidis isolates from human cases matched those of nine isolates from internal organs of egg-laying hens in one flock which was the source of eggs consumed by the cases. Another commercial flock was epidemiologically associated as the source of eggs consumed by affected persons in four separate gastroenteritis outbreaks from which S. enteritidis isolates were available. Five S. enteritidis isolates from human cases in these four outbreaks had the same profile and fingerprint, and they all matched those of the 24 isolates from hens in this flock. These results provide further documentation of egg-borne transmission of S. enteritidis to humans.     

Antibiotic susceptibility of Salmonella enterica serovar Typhi isolated from blood cultures at the Ain M'lila hospital (Algeria), between 2005 and 2008

Introduction

Typhoid fever is a food- and water-borne disease, caused by Salmonella enterica serovar Typhi, responsible for high rates of morbidity and mortality in developing countries. Typhoid is also a public health problem in Algeria. Antimicrobial susceptibility surveillance must be applied to prevent the emergence of multidrug resistant strains.

Patients and methods

We studied the incidence of S. enterica serovar Typhi isolated from blood cultures in the Ain M’lila public hospital (Algeria), between 2005 and 2008. Blood cultures were performed in the febrile stage of infection and positive samples were identified by biochemical and antigenic tests. Susceptibility to ampicillin, cotrimoxazole, chloramphenicol and nalidixic acid was tested by antibiogram.

Results

One hundred and seventy-eight strains were isolated from blood cultures between 2005 and 2008. They were all susceptible to the antibiotics tested.

Discussion

Typhoid fever incidence has decreased in Algeria. In our region, it comes by outbreaks during the summer season, with no sporadic cases between the peaks. In our study, S. enterica serovar Typhi was still susceptible to antimicrobials despite the worldwide emergence of multidrug resistant strains.

Conclusion

A regular surveillance of Salmonella typhi antibiotic susceptibility is mandatory.     

Prevalence and antibiotic resistance of Salmonella isolated from a poultry farm and processing plant environment in the State of Kuwait

The prevalence of Salmonella isolated from a poultry farm and from the poultry processing plant environment were evaluated from August 2004 to July 2005 along with microbial antibiotic resistance. In total, 3242 samples were collected from the farm and processing plant. Samples collected from the farm included hatching eggs, paper liners, litter, feed, water, drinkers, air, bird rinse, and ceca. While samples collected from the processing plant included carcass rinse and ceca. Out of 2882 samples collected from the farm, the overall percentage prevalence of Salmonella was 5.4% with prevalence rates of 10%, 1.5%, 0.7%, 0.2%, 13.5%, and 12.6% for hatching eggs, litter, feed, drinkers, bird rinse and ceca, respectively. No Salmonella were detected in any of the paper liner, water, or air samples. Out of 360 samples collected from the processing plant, the overall percentage prevalence of Salmonella was 4.7% with prevalence rates of 6.1% and 3.3% for carcass rinse and ceca samples, respectively. Salmonella Enteritidis was the most prevalent serotype. All of the isolates were resistant to at least one antibiotic and 10 different resistance profiles were found among 173 isolates of Salmonella Enteritidis. Resistance to ampicillin, nalidixic acid, and tetracycline were the most common. The widespread occurrence of multiple resistant Salmonella Enteritidis is a cause for concern, and local regulatory enforcement agencies should ensure prudent use of antibiotics.     

The economics of the disposal of sewage and trade effluents

In this review of the economics of the disposal of sewage and trade wastes, the author touches on all aspects of the subject, from the annual costs of sewerage and sewage-disposal services in England and Wales, and what he terms the “uneconomics” of pollution of natural waters, to the financing of capital expenditure on the construction of new sewage works and equipment and on alterations to existing works. He discusses the purposes and relative costs of the various processes in the treatment of domestic sewage and outlines the special problems involved in the disposal of trade wastes.