Campylobacter susceptibility to ciprofloxacin and corresponding fluoroquinolone concentrations within the gastrointestinal tracts of chickens

AIMS: This study evaluated the relationship between Campylobacter susceptibility and enteric fluoroquinolone concentrations in chickens treated with different doses of enrofloxacin. METHODS AND RESULTS: All chickens were challenged with seven fluoroquinolone sensitive Campylobacter jejuni (6.6 x 10(6) CFU per bird) at 2 weeks posthatch. At 26 days of age chickens were treated with 0 (n = 29 birds), 25 mg ml(-1) enrofloxacin (Baytril, Bayer Corp., Shawnee Mission, KS, USA) for 3 days (n = 45 birds) or 50 mg ml(-1) enrofloxacin for 7 days (n = 65 birds) in the drinking water. The crop, upper ileum, lower ileum, ceca and colon contents were collected from both enrofloxacin treatment groups (n = 5 birds per day per treatment group) and nonmedicated controls. The minimum inhibitory concentration (MIC) of ciprofloxacin for Campylobacter increased for isolates from both treatment groups within the first day of dosing and the daily average ranged from 1.4 to 6.5 microg ml(-1) throughout the study. Although enteric fluoroquinolone concentrations were higher (P < 0.05) in birds dosed with 50 mg ml(-1)vs 25 mg ml(-1) enrofloxacin, there were no differences between the isolates collected from these groups for MIC values. CONCLUSION: These data indicate, for the doses used, differences in gut fluoroquinolone concentrations do not produce isolates of Campylobacter with differing susceptibility to ciprofloxacin. SIGNIFICANCE AND IMPACT OF THE STUDY: Using the manufacturers lowest, shortest duration dose vs the highest, longest duration dose of enrofloxacin did not change Campylobacter susceptibility to ciprofloxacin. However, ciprofloxacin MIC values for Campylobacter determined in this study were lower than previously reported.     

Evaluation of nested PCR assays for the detection of Legionella pneumophila in a wide range of aquatic samples

AIMS: To compare the sensitivities of two nested PCR assays for the detection of Legionella pneumophila to each other and to the plate counting technique (ISO 11731) in a wide range of aquatic samples. METHODS AND RESULTS: The nested PCR assay with the primer set LEG 225-LEG 858 revealed 56% of the 46 analysed aquatic samples as being positive for Legionella spp., while the primer set JFP-JRP yielded 98% positive samples. The detection was confirmed by sequencing the PCR products. These results are considerably higher than the result obtained with the plate counting technique (41%), indicating the higher sensitivity of PCR-based diagnostic methods. As the PCR assay with the LEG 225-LEG 858 primer set resulted in a lower number of positive samples, it is considered not sensitive enough for aquatic samples. Similar results for the respective primer sets were obtained for the detection of the species L. pneumophila, responsible for 90% of all human Legionella infections, in the aquatic samples analysed. Both microbial community analysis by PCR-denaturing gradient gel electrophoresis and the analysis of biotic and abiotic water quality parameters revealed no relation between L. pneumophila-positive and -negative samples and the physico-chemical and bacteriological characteristics of the aquatic samples. CONCLUSIONS: The results show the additional value of the PCR assay with the JFP-JRP primer set compared with the plate counting technique, as well as its applicability in a wide range of aquatic samples. SIGNIFICANCE AND IMPACT OF THE STUDY: This study shows the importance of comparing different primer sets for nested PCR assays for the detection of L. pneumophila in aquatic samples, as well as the lower sensitivity of the widely accepted plate counting technique (ISO 11731).     

Immunocapture UPPCR combined with DGGE for rapid detection of Shigella species

AIMS: To develop an immunocapture universal primer PCR (iUPPCR) combined with denaturing gradient gel electrophoresis (DGGE) and evaluate it as a method permitting rapid detection of Shigella species and their serotypes. METHODS AND RESULTS: This method amplifying the conserved regions of bacterial 16S rRNA genes of different species or serotypes of Shigella dysentery bacilli captured and enriched by polyvalent antibodies can detect and distinguish causative pathogens rapidly. Four serotypes from three Shigella species including Shigella dysenteriae serotype 1, Shigella boydii serotype 1, Shigella flexneri serotypes 1a and 3a were examined. CONCLUSION: Our approach could be adopted for not only axenic bacterial population but also mixed communities and achieve rapid detection of various bacteria from the same genus or species in one sample. SIGNIFICANCE AND IMPACT OF THE STUDY: The iUPPCR-DGGE method was shown to be more convenient than serotype-specific-antibody-based method of iUPPCR for Shigella species detection and it could be also applied to the quick detection for other kinds of pathogens with many serotypes.     

Influence of soil type, moisture content and biosolids application on the fate of Escherichia coli in agricultural soil under controlled laboratory conditions

AIMS: To determine the fate of the enteric indicator organism, Escherichia coli, in sewage sludge (biosolids)-amended agricultural soil in relation to soil type and moisture status under controlled conditions. METHODS AND RESULTS: We enumerated Escherichia coli in soil by membrane filtration and most probable number techniques. The background concentration of E. coli was higher in sandy loam than in silty clay soil. E. coli numbers increased in soil following addition of dewatered, mesophilic anaerobically digested sludge. Escherichia coli declined to a small extent with time in both moist and air-dried unamended control soils, although decay was only highly significant (P < 0.001) in moist sandy loam (T(90) = 100 days). Removal rates were high in sludge-treated moist soil (T(90) = 20 days), but were significantly reduced in amended air-dried soil. CONCLUSIONS: Slow removal of E. coli in air-dried soil as against their rapid decay in moist soil after sludge application indicated that the soil biota are involved in pathogen reduction processes in sludge-amended soil. SIGNIFICANCE AND IMPACT OF THE STUDY: Soil ecological mechanisms are implicated as having a critical role in the fate of enteric organisms introduced into temperate agricultural soil in sewage sludge.     

Prevalence of the stx2 gene in coliform populations from aquatic environments

Shiga toxin-producing Escherichia coli strains are human pathogens linked to hemorrhagic colitis and hemolytic uremic syndrome. The major virulence factors of these strains are Shiga toxins Stx1 and Stx2. The majority of the genes coding for these toxins are borne by bacteriophages. Free Stx2-encoding bacteriophages have been found in aquatic environments, but there is limited information about the lysogenic strains and bacteria present in the environment that are susceptible to phage infection. The aim of this work was to study the prevalence and the distribution of the stx(2) gene in coliform bacteria in sewage samples of different origins. The presence of the stx(2) gene was monitored every 2 weeks over a 1-year period in a municipal sewage treatment plant. A mean value of 10(2) genes/ml was observed without significant variation during the study period. This concentration was of the same order of magnitude in raw municipal sewage of various origins and in animal wastewater from several slaughterhouses. A total of 138 strains carrying the stx(2) gene were isolated by colony hybridization. This procedure detected approximately 1 gene-carrying colony per 1,000 fecal coliform colonies in municipal sewage and around 1 gene-carrying colony per 100 fecal coliform colonies in animal wastewaters. Most of the isolates belonged to E. coli serotypes other than E. coli O157, suggesting a low prevalence of strains of this serotype carrying the stx(2) gene in the wastewater studied.     

Recognition of individual genes in diverse microorganisms by cycling primed in situ amplification

Cycling primed in situ amplification-fluorescent in situ hybridization (CPRINS-FISH) was developed to recognize individual genes in a single bacterial cell. In CPRINS, the amplicon was long single-stranded DNA and thus retained within the permeabilized microbial cells. FISH with a multiply labeled fluorescent probe set enabled significant reduction in nonspecific background while maintaining high fluorescence signals of target bacteria. The ampicillin resistance gene in Escherichia coli, chloramphenicol acetyltransferase gene in different gram-negative strains, and RNA polymerase sigma factor (rpoD) gene in Aeromonas spp. could be detected under identical permeabilization conditions. After concentration of environmental freshwater samples onto polycarbonate filters and subsequent coating of filters in gelatin, no decrease in bacterial cell numbers was observed with extensive permeabilization. The detection rates of bacterioplankton in river and pond water samples by CPRINS-FISH with a universal 16S rRNA gene primer and probe set ranged from 65 to 76% of total cell counts (mean, 71%). The concentrations of cells detected by CPRINS-FISH targeting of the rpoD genes of Aeromonas sobria and A. hydrophila in the water samples varied between 2.1 x 10(3) and 9.0 x 10(3) cells ml(-1) and between undetectable and 5.1 x 10(2) cells ml(-1), respectively. These results demonstrate that CPRINS-FISH provides a high sensitivity for microscopic detection of bacteria carrying a specific gene in natural aquatic samples.     

Comparison of primers for the detection of pathogenic Escherichia coli using real-time PCR

AIMS: To evaluate PCR primers for the detection of pathogenic Escherichia coli in a real-time PCR assay and determine their utility in produce irrigation water testing. METHODS AND RESULTS: Three previously published PCR primer sets and one set designed for this study were tested for their ability to produce amplification products for several pathogenic E. coli serotypes from whole cells as template. Two of the previously published primer sets were chosen for real-time PCR detection limit determination. The coneaeA and PEH detection limit of E. coli O157:H7 was 10(0) and 10(1) CFU rxn(-1) in sterile water respectively. To detect E. coli O157:H7 in sprout irrigation water, the water required dilution due to PCR inhibitors. The detection limit of the coneaeA and PEH was 10(1) and between 10(2) and 10(3) CFU rxn(-1) in diluted sprout irrigation water respectively. CONCLUSIONS: The primer set coneaeA was able to produce an amplification product from each E. coli serotype, except O128:H7 and most sensitive for real-time PCR detection of pathogenic E. coli in diluted sprout irrigation water. SIGNIFICANCE AND IMPACT OF THE STUDY: The necessity of a dissociation analysis to distinguish positive samples from those with fluorescence of random dsDNA generation for real-time PCR in a complex background was established.     

Evaluation of the efficiency of peracetic acid in the disinfection of sewage effluents

AIMS: Evaluation of the efficiency of peracetic acid in the disinfection of wastewater in a large treatment plant. METHODS AND RESULTS: Over a period of 18 months 30 sample collections were made, each consisting of three samples taken from: raw incoming sewage, secondary effluent (after 10-12 h) and secondary effluent disinfected with 1.5-2 mg l(-1) of peracetic acid (contact time: 20 min). Total coliforms and Escherichia coli declined from 10(7) MPN 100 ml(-1) in the raw sewage to 10(2) in the disinfected effluent and the enterococci fell from 10(6) MPN 100 ml(-1) to 702 MPN 100 ml(-1). The reduction of bacteria increased with the rise in temperature and decreased with the rise in BOD5. CONCLUSIONS: Disinfection with peracetic acid reduced levels of faecal contamination by 97%, thus attaining the limit recommended by current Italian law (Escherichia coli 相似文献   

16S/18S/ITS扩增子高通量测序引物的生物信息学评估和改进

【背景】在过去的十几年里,基于核糖体RNA基因的扩增子测序技术被广泛用于各种生态系统中微生物群落的多样性检测。扩增子测序的使用极大地促进了土壤、水体、空气等环境中微生物生态的相关研究。【目的】随着高通量测序技术的不断发展和参考数据库的不断更新,针对不同的环境样本的引物选择和改进仍然需要更深入的校验。【方法】本文收集了目前在微生物群落研究中被广泛采用的标记基因扩增通用引物,包括16S rRNA基因扩增常用的8对通用引物和2对古菌引物、9对真菌转录间隔区(internal transcribed spacer,ITS)基因扩增引物,以及18S rRNA基因扩增的4对真核微生物通用引物和1对真菌特异性引物。这些引物中包括了地球微生物组计划(Earth Microbiome Project,EMP)推荐的2对16S rRNA基因扩增引物、1对ITS1基因扩增引物和1对18S rRNA基因扩增引物。采用最近更新的标准数据库对这些引物进行了覆盖度和特异性评价。【结果】EMP推荐的引物依然具有较高的覆盖度,而其他引物在覆盖度及对特定环境或类群的特异性上也各有特点。此外,最近有研究对这些通用引物进行了一些改进,而我们也发现,一个碱基的变化都可能会导致评价结果或扩增产物发生明显变化,简并碱基的引入既可以覆盖更多的物种,但同时也会在一定程度上降低关注物种的特异性。【结论】研究结果为微生态研究中标记基因的引物选择提供了一个广泛的指导,但在关注具体科学问题时,引物的选择仍需数据指导与实验尝试。     

Risk assessment of adenoviruses detected in treated drinking water and recreational water

AIMS: Human adenoviruses (HAds) have previously been detected in sewage and polluted river and dam water, as well as treated drinking water. The 51 serotypes of HAds cause a wide range of infections with clinical manifestations associated with the gastrointestinal, respiratory and urinary tracts, and the eyes. Water may play a meaningful role in the transmission of many of these HAd serotypes, specifically the enteric HAds which are transmitted via the faecal-oral route. The presence of these viruses in water used for drinking and recreational purposes is considered to constitute a potential health risk. In this study, the risk of infection by the group of HAds previously detected over a period of 1 year in selected drinking water supplies, as well as river and dam water used for recreational purposes, was assessed. METHODS AND RESULTS: Adenoviruses were previously detected in nine of 204 (4.41%) samples of two drinking water supplies (A and B) treated and disinfected according to international specifications, in four of 51 (7.8%) samples of river water and nine of 51 (17.7%) samples of dam water. Application of these previously published results in an exponential risk assessment model indicated an annual risk of infection of 1.01 x 10(-1) and 1.7 x 10(-1) for drinking water supplies A and B, respectively, assuming a daily consumption of 2 l day(-1). The daily risk of infection constituted by HAds in the river water was calculated as 1.71 x 10(-4), and in the dam water as 3.12 x 10(-5), assuming a consumption of 30 ml of water per day. CONCLUSIONS: The risk of infection exceeded the tolerable risk of one infection per 10 000 consumers per year proposed for drinking water. However, the results for river and dam water used for recreational purposes were within the tolerable risk of one infection per 1000 bathers per day proposed for environmental waters used for recreational purposes. SIGNIFICANCE AND IMPACT OF THE STUDY: The study showed that the risk of HAd infection calculated for the drinking water supplies and the recreational water may overestimate the actual risk of infection, as conservative values were assumed for some of the variables. For a more accurate assessment of the potential risk of infection research should at least include a thorough investigation of the water consumption of individuals in South Africa, and the efficiency of recovery of the glass wool adsorption-elution method.     

Effect of different anesthetics on immunoreactive atrial natriuretic factor concentrations in rat plasma

The effect of different conditions of blood withdrawal and use of different anesthetics on immunoreactive atrial natriuretic factor (IR-ANF) concentrations in plasma was studied in rats. The concentration of IR-ANF in plasma from jugular vein of non-anesthetized conscious rats, cannulated either 24 hr before blood withdrawal was 93.9 +/- 17.1 pg/ml (n = 30); and 48 hr: 81.9 +/- 11.5 pg/ml (n = 29). Immobilization stress (4 hr) increased IR-ANF concentration: 248.0 +/- 80.2 pg/ml (n = 5). Anesthesia by morphine, diethyl-ether, chloral hydrate and ketamine chlorhydrate increased IR-ANF concentrations to 2,443.0 +/- 281.2 pg/ml (n = 24), 806.1 +/- 74.6 pg/ml (n = 64), 224.0 +/- 81.4 pg/ml (n = 20), and 195.0 +/- 20.3 pg/ml (n = 51), respectively. IR-ANF in plasma of sodium-pentobarbital and urethane anesthetized rats was 59.2 +/- 6.7 pg/ml (n = 10) and 42.6 +/- 8.1 pg/ml (n = 8), respectively. These changes in IR-ANF evoked by different types of anesthetics and different conditions of blood withdrawal have to be taken into consideration during studies on the physiopathological role of atrial natriuretic factor.     

Elimination of human enteric viruses during conventional waste water treatment by activated sludge

The present study was undertaken to determine if viruses were selectively eliminated during waste water treatment. Human enteric viruses were detected at all steps of treatment in a conventional activated sludge waste water treatment plant. Liquid overlays and large volume sampling with multiple passages on BGM cells permitted the detection of poliovirus (serotypes 1, 2, and 3), coxsackievirus B (serotypes 1, 2, 3, 4, and 5), and echovirus (serotypes 3, 14, and 22), as well as reoviruses. The mean virus concentration was 95.1 most probable number of infectious units per litre (mpniu/L) in raw sewage, 23.3 in settled water, 1.4 in effluent after activated sludge treatment, and 40.3 mpniu/L in sludge samples. All samples of raw sewage and settled water, 79% of effluent water, and 94% of sludge samples contained viruses. The mean reduction was 75% after settling and 98% after activated sludge treatment. Poliovirus type 3 was rarely isolated after the activated sludge treatment, but was still detected in about one-third of the sludge samples. Reoviruses and coxsackieviruses were detected at similar rates from all samples and appear to be more resistant to the activated sludge treatment than poliovirus type 3. Poliovirus types 1 and 2 were present in almost every sample of raw sewage and settled water and still found in about half of the effluent and sludge samples, indicating a level of resistance similar to that of reoviruses and coxsackieviruses.     

Homology of Escherichia coli R773 arsA, arsB, and arsC genes in arsenic-resistant bacteria isolated from raw sewage and arsenic-enriched creek waters.

The occurrence and diversity of the Escherichia coli R773 ars operon were investigated among arsenic-resistant enteric and nonenteric bacteria isolated from raw sewage and arsenic-enriched creek waters. Selected isolates from each creek location were screened for ars genes by colony hybridization and PCR. The occurrence of arsA, arsB, and arsC determined by low-stringency colony hybridization (31 to 53% estimated mismatch) was 81, 87, and 86%, respectively, for 84 bacteria isolated on arsenate- and arsenite-amended media from three locations. At moderate stringency (21 to 36% estimated mismatch), the occurrence decreased to 42, 56, and 63% for arsA, arsB, and arsC, respectively. PCR results showed that the ars operon is conserved in some enteric bacteria isolated from creek waters and raw sewage. The occurrence of the arsBC genotype was about 50% in raw sewage enteric bacteria, while arsA was detected in only 9.4% of the isolates (n = 32). The arsABC and arsBC genotypes occurred more frequently in enteric bacteria isolated from creek samples: 71.4 and 85.7% (n = 7), respectively. Average sequence divergence within arsB for six creek enteric bacteria was 20% compared to that of the E. coli R773 ars operon. Only 1 of 11 pseudomonads screened by PCR was positive for arsB. The results from this study suggest that significant divergence has occurred in the ars operon among As-resistant E. coli strains and in Pseudomonas spp.     

Quantitative procedure for enumeration of bifidobacteria.

A membrane filter technique has been developed for the enumeration of bifidobacteria in natural aquatic environments. The technique is quantitative, selective, and differential. The medium (YN-6) contains: yeast extract, 2.0 g; agar, 1.5 g; polypeptone peptone, 1.0 g; vitamin-free Casamino Acids, 0.8 g; sodium chloride, 0.32 g; and L-cysteine hydrochloride, 0.003 g; in 100 ml of deionized water. The medium is adjusted to pH 7.0 before autoclaving. Nalidixic acid (80 micrograms/ml), neomycin sulfate (2.5 micrograms/ml), and bromcresol green (300 micrograms/ml) are included as selective and differential agents. After incubation for 48 h at 37 degrees C in an anaerobic environment, Gram-stained smears from green, glistening, smooth entire colonies are examined microscopically for typical bifidobacterial morphology. No significant difference in recoveries was observed when YN-6 was compared with reinforced clostridial agar, using bifidobacteria freshly isolated from feces and raw sewage. Using this technique with aquatic and fecal samples, less than 9% false-positive and 8% false-negative isolates were observed. These results indicated that the medium was able to satisfactorily recover organisms from a variety of situations.     

Differentiation of outer membrane proteins from Salmonellaenterica serotypes using Fourier transform infrared spectroscopy and chemometrics

AIMS: To differentiate between outer membrane proteins (OMPs) from six Salmonellaenterica serotypes using a Fourier transform infrared (FTIR) spectroscopy method and chemometrics. METHODS AND RESULTS: The OMPs from Salmonella serotypes (Typhimurium, Enteritidis, Thomasville, Hadar, Seftenberg and Brandenburg) were isolated using a sarcosyl extraction method. OMP profiles on SDS-PAGE exhibited two or three bands between 48 and 54 kDa. Spectra of 10 microl of OMP preparations (5 mg ml(-1)) dried on a gold reflective slide were collected using 128 scans at 4 cm(-1) resolution and units of log (1/R) and analyzed using canonical variate analysis (CVA) and linear discriminant analysis (LDA). The CVA of Salmonella OMP spectra in the 1800-1500 cm(-1) region separated the serotypes and LDA provided a 100% correct classification. CONCLUSIONS: The use of a FTIR method combined with chemometrics provided better differentiation of Salmonella OMPs than the OMP pattern analysis by SDS-PAGE. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first study to demonstrate that spectra of OMP extracts from Salmonella serotypes can be used for 100% correct classification of the serotypes studied.     

Unique requirements for template primers of DNA polymerase beta from rat ascites hepatoma AH130 cells.

The optimal condition for the rat DNA polymerase beta activity with (rA)n . (dT)12-18 as a template-primer was determined. The activity was remarkably affected by the concentration of the primer, (dT)12-18' and the mixing ratio of (dT)12-18 to (rA)n. DNA polymerase beta requires higher primer concentration (Km = 11.1 microM with respect to 3'-OH of the primer) than DNA polymerase gamma (Km = 0.04 microM) or oncornaviral DNA polymerase (Km = 0.08 microM) and the enzyme represented the maximum activity in the base ratio of 2:1 with (dT)12-18 and (rA)n suggesting the difference in reaction mechanisms of these enzymes. Under the optimized conditions, the specific activity of the near homogeneous preparation of DNA polymerase beta was 1,000,000 units per mg protein.     

In vitro inhibitory effect of gossypol from gossypol-acetic acid, and (+)- and (-)-isomers of gossypol on the growth of Edwardsiella ictaluri

AIM: This study was conducted to evaluate the toxic effect of gossypol from gossypol-acetic acid, and (+)- and (-)-isomers of gossypol on the growth of Edwardsiella ictaluri. METHODS AND RESULTS: Inhibitory effect of various concentrations of gossypol on the growth of E. ictaluri was determined. Bacterial recovery was performed by preincubation of bacteria in medium containing various concentrations of gossypol and subsequent activation of bacteria by inoculating on gossypol-free plates. Concentrations of racemic gossypol, (+)-gossypol and (-)-gossypol of 1.5 microg ml(-1) or higher significantly reduced the number of bacterial colonies compared with that of the control. The growth of E. ictaluri was completely inhibited on agar plates supplemented with 3 microg ml(-1), regardless of the forms of gossypol. The inhibitory effect of (+)-gossypol was higher than that of (-)-gossypol or gossypol-acetic acid. Recovery of E. ictaluri was <50% for all three forms of gossypol at concentrations of 5 microg ml(-1). Bacterial recovery remained relatively constant (6.5%) at gossypol concentrations from 10 to 100 microg ml(-1). Complete killing of E. ictaluri was not reached at gossypol levels up to 100 microg ml(-1). CONCLUSION: Gossypol-acetic acid, and (+)- and (-)-optical isomers have anti-bacterial effect against E. ictaluri. The results suggest the action is bacteriostatic rather than bactericidal. SIGNIFICANCE AND IMPACT OF THE STUDY: The therapeutic effect of gossypol against E. ictaluri may be useful in controlling enteric septicaemia of catfish.     

Two distinct mutations in gyrA lead to ciprofloxacin and nalidixic acid resistance in Campylobacter coli and Campylobacter jejuni isolated from chickens and beef cattle

AIMS: The aim of this study was to identify point mutations in the gyrA quinolone resistance determining region (QRDR) of Campylobacter coli (n = 27) and Campylobacter jejuni (n = 26) that confer nalidixic acid (NAL) resistance without conferring resistance to ciprofloxacin (CIP). METHODS AND RESULTS: Point mutations in the QRDR of gyrA from C. coli and C. jejuni isolates were identified by direct sequencing. All isolates (n = 14) with minimum inhibitory concentrations (MICs) >or=4 microg ml(-1) for CIP and >or=32 microg ml(-1) for NAL possessed a missense mutation leading to substitution of Ile for Thr at codon 86. Three isolates with a missense mutation leading to a Thr86Ala substitution had MICs <4 mug ml(-1) for CIP and >or=32 microg ml(-1) for NAL. CONCLUSIONS: These data confirm previous findings that Thr86Ile mutations confer resistance to both CIP and NAL. However, resistance to NAL alone was conferred by a single Thr86Ala mutation. SIGNIFICANCE AND IMPACT OF THE STUDY: Resistance to NAL alone arises independently from CIP resistance. In addition, the role of other previously described point mutations in quinolone resistance is discussed.     

Presence of Salmonella as a risk to public health in the Caribbean zone of Colombia

Salmonella is frequently involved in diarrhoeal disease throughout the world and is disseminated mainly by food, polluted waters or infected food-handlers. In Colombia, the serotypes of Salmonella and their distribution in food have not been characterized. Therefore, the objective was to establish the epidemiology of Salmonella in the Caribbean zone. Six hundred thirty-six samples were obtained in fast food outlets located in city squares or markets of Barranquilla (n=245), Montería (n=222), Sincelejo (n=87) and Cartagena (n=82). Salmonella was isolated by the conventional methods recommended by the United States Food and Drug Administration. Briefly, 25 g of each sample was inoculated in 225 ml of broth. Twenty-four hours later, a 1 ml aliquot was inoculated onto selective media for Salmonella. Suspicious colonies were identified by conventional biochemical tests and confirmed by conventional serology for Salmonella detection. Forty-seven Salmonella serotypes were isolated from meat (40%), sausage (25%), cheese (13%), pig (13%), chicken (4.2%) and egg 'arepas' (4.2%). The serologic characterization indicated the following serotypes: S. Anatum (26%), S. Newport (13%), S. Typhimurium (9%), S. Gaminara (9%) and S. Uganda (9%). No statistically significant Salmonella isolations among 4 socioeconomic categories were observed (p=0.05). However, differences were observed when rates were compared for Salmonella by food type for socioeconomic categories 1, 2 and 3 (p<0.05), categories 2 and 3 did not show differences between them (p>0.05).     

Grazing rates of diverse morphotypes of bacterivorous ciliates feeding on four allochthonous bacteria

AIMS: The permanence in aquatic systems of allochthonous bacteria coming from sewage effluents is a risk for public health. This work aimed to analyse the elimination of the bacteria Staphylococcus epidermidis, Enterococcus faecalis, Escherichia coli and Klebsiella pneumoniae by a riverine ciliate community. METHODS AND RESULTS: The ciliates were characterized and identified on the basis of morphological and behavioural features and grouped in nine morphotypes. Differential grazing by each morphotype on the four allochthonous bacteria was carried out by adding fluorescently labelled bacteria to the water samples, and measuring their uptake along time. CONCLUSIONS: The nine morphotypes were present in all the samples but in different proportions, being the most abundant the small scuticociliates and hipotrichs. The smallest morphotypes showed grazing rates lower than 20 FLB ciliate(-1) h(-1), with a preference towards K. pneumoniae. The larger morphotypes showed in general the highest grazing rates, but the selectivity was hardly attributable to bacterial size or type of cell wall. CONCLUSIONS, SIGNIFICANCE AND IMPACT OF THE STUDY: The elimination of allochthonous bacteria in an aquatic system may be highly different depending on the diversity of the ciliated protistan community in the system and on the nature of the bacterial prey.