Investigating the antimicrobial potential of bovine lactoferrin against the neonatal pathogen, Staphylococcus capitis.

Lactoferrin is an antimicrobial glycoprotein that demonstrates a broad-spectrum of activity against a wide variety of clinical pathogens. This study investigated the potential of bovine lactoferrin (bLf) against multidrug resistant Staphylococcus capitis (S. capitis) strains. Growth curve analysis and time-kill curves demonstrated that at 750 µg ml-1 lactoferrin significantly inhibited (50.6%, P < 0.05) the growth of most isolates tested (90%), and this effect was based on a bacteriostatic mechanism. At the same concentration, bLf also significantly inhibited (30%, P < 0.05) biofilm formation in 40% of strains tested. Combinations of bLf with selected antibiotics were assessed for enhanced antimicrobial activity using growth curves. BLf combined with ß-lactam antibiotics reduced the growth of S. capitis strains, however, the effects were not significant. BLf displays antimicrobial effects against multidrug resistant S. capitis isolates, but with strain-specific effects.

Calculated Globulin as a potential screening tool for paraproteinemia to aid in the early diagnosis of Multiple Myeloma.

BACKGROUND: Multiple Myeloma (MM) is a haematological malignancy with increasing global incidence. Diagnosis of MM should be initiated at the primary care level to achieve the best patient outcome. However, this can be delayed due to nonspecific presenting symptoms, such as back pain and fatigue. OBJECTIVES: The aim of this study was to investigate if commonly requested blood tests could indicate MM in primary care and potentially lead to earlier diagnosis. DESIGN AND METHODS: This retrospective observational study involved an audit of clinical and laboratory data from 109 MM patients, including patients with Active MM (N = 53), Smouldering MM (N = 33), and Free light chain MM (N = 23). RESULTS: Of the 16 potential biomarkers investigated, the most promising indicator for early detection of active MM and Smouldering MM was an increased Calculated Globulin (CG). The median CG for patients with active MM (50 g/L) was 78.6% higher than the healthy control group (28 g/L). Smouldering MM patients had a median CG value (38 g/L), which was 35.7% higher than the control group. Of interest, the median CG result was only 16.7% higher in the control group than in the free light chain MM group, suggesting CG would not be as effective at detecting this subtype. CONCLUSIONS: CG is derived from Total Protein and Albumin data, which are commonly measured in routine liver function profiles, thus there is no additional test or cost requirement. Based on these data, CG has potential as a clinical biomarker to support early detection of MM at the primary care level and allow for appropriate targeted investigations.

Bioengineered Nisin A Derivatives Display Enhanced Activity against Clinical Neonatal Pathogens.

Neonatal infection is a significant cause of mortality and morbidity in infants. The global incidence of multi-drug resistance continues to rise among neonatal pathogens, indicating a need for alternative treatment strategies. Nisin is an antimicrobial peptide that exhibits broad-spectrum activity against a wide variety of clinical pathogens and can be used in combination with antibiotics to improve their effectiveness. This study examined the activity of nisin and bioengineered derivatives against multi-drug resistant Streptococcus agalactiae and Staphylococcus capitis isolates and investigated the potential synergy between nisin peptides and selected antibiotics. Whole genome sequence analysis of the strains revealed the presence of multi-drug resistant determinants, e.g., macrolide, tetracycline, ß-lactam, aminoglycoside, while the S. agalactiae strains all possessed both nsr and nsrFP genes and the S. capitis strains were found to encode the nsr gene alone. Deferred antagonism assays demonstrated that nisin PV had improved antimicrobial activity against all strains tested (n = 10). The enhanced specific activity of this peptide was confirmed using minimum inhibitory concentrations (MIC) (0-4-fold lower MIC for nisin PV) and broth-based survival assays. Combinations of nisin peptides with antibiotics were assessed for enhanced antimicrobial activity using growth and time-kill assays and revealed a more effective nisin PV/ampicillin combination against one S. capitis strain while a nisin A/erythromycin combination displayed a synergistic effect against one S. agalactiae strain. The findings of this study suggest that nisin derivatives alone and in combination with antibiotics have potential as alternative antimicrobial strategies to target neonatal pathogens.

Minimal Residual Disease in Multiple Myeloma: Potential for Blood-Based Methods to Monitor Disease.

In recent years, the life expectancy of Multiple Myeloma (MM) patients has substantially improved, but this cancer remains incurable with increasing incidence in the developed world. Most MM patients will eventually relapse due to residual drug-resistant cancerous cells that survive treatment, commonly referred to as minimal residual disease (MRD). Methods to improve MRD detection in MM patients are generating considerable interest as a means of monitoring patients' response to treatment. In clinical laboratories, these methods currently require bone marrow aspirates which are invasive and frequently miss detection of localised disease due to the spatial heterogeneity of disease infiltration. By simplifying serial sampling and allowing for the detection of extramedullary disease, a blood-based method could significantly impact treatment duration and intensity and minimise chemotherapy-induced toxicity. This review will describe the current blood-based techniques available to detect MRD in MM and compare their potential to evaluate patient prognosis and drive therapeutic decisions.

Dietary protein considerations for muscle protein synthesis and muscle mass preservation in older adults.

Amino acid bioavailability is critical for muscle protein synthesis (MPS) and preservation of skeletal muscle mass (SMM). Ageing is associated with reduced responsiveness of MPS to essential amino acids (EAA). Further, the older adult population experiences anabolic resistance, leading to increased frailty, functional decline and depleted muscle mass preservation, which facilitates the need for increased protein intake to increase their SMM. This review focuses on the role of proteins in muscle mass preservation and examines the contribution of EAA and protein intake patterns to MPS. Leucine is the most widely studied amino acid for its role as a potent stimulator of MPS, though due to inadequate data little is yet known about the role of other EAA. Reaching a conclusion on the best pattern of protein intake has proven difficult due to conflicting studies. A mixture of animal and plant proteins can contribute to increased MPS and potentially attenuate muscle wasting conditions; however, there is limited research on the biological impact of protein blends in older adults. While there is some evidence to suggest that liquid protein foods with higher than the RDA of protein may be the best strategy for achieving high MPS rates in older adults, clinical trials are warranted to confirm an association between food form and SMM preservation. Further research is warranted before adequate recommendations and strategies for optimising SMM in the elderly population can be proposed.

Cheese as a functional food for older adults: comparing the bioactive properties of different cheese matrices following simulated gastrointestinal in vitro digestion.

Age-related changes to the gastrointestinal tract (GIT) can impact how food is digested. Studying the effects of these changes can help identify functional foods for older adults. Cheese was digested using two simulated gastrointestinal in vitro digestion (SGID) models representing adult and elderly gastro-intestinal conditions. Antioxidant capacity was measured using DPPH, FRAP and TPC assays. The ability of cheese to inhibit digestive enzymes was determined by the α-glucosidase and lipase inhibition assays. Digestive aging influenced the bioactivity of cheese, as elderly digestates had significantly lower (p < 0.05) antioxidant, α-glucosidase and lipase inhibitory properties compared to adult digestates. However, soft cheese (feta, goats', brie) demonstrated greatest potential with comparable radical scavenging properties and lipase inhibition, greatest FRAP and α-glucosidase inhibitory potential. Despite age-related changes, the bioactive properties of cheese were evident following digestion with an older adult SGID model, suggesting cheese has potential as a functional food for older adults.

A review of antibiotic resistance in Group B Streptococcus: the story so far.

Group B Streptococcus (GBS) is the leading cause of neonatal disease worldwide, and invasive disease in adults is becoming more prevalent. Currently, some countries adopt an intrapartum antibiotic prophylaxis regime to help prevent the transmission of GBS from mother to neonate during delivery. This precaution has reduced the incidence of GBS-associated early-onset disease; however, rates of late-onset disease and stillbirths associated with GBS infections remain unchanged. GBS is still recognized as being universally susceptible to beta-lactam antibiotics; however, there have been reports of reduced susceptibility to beta-lactams, including penicillin, in some countries. Resistance to second-line antibiotics, such as erythromycin and clindamycin, remains high amongst GBS, with several countries noting increased resistance rates in recent years. Moreover, resistance to other antibiotic classes, such as fluoroquinolones and aminoglycosides, also continues to rise. In instances where patients are allergic to penicillin and second-line antibiotics are ineffective, vancomycin is administered. While vancomycin, a last resort antibiotic, still remains largely effective, there have been two documented cases of vancomycin resistance in GBS. This review provides a comprehensive analysis of the prevalence of antibiotic resistance in GBS and outlines the specific resistance mechanisms identified in GBS isolates to date.

A casein hydrolysate increases GLP-1 secretion and reduces food intake.

In an effort to control weight gain, much attention has focused on the identification of bioactive peptides from food sources that induce satiety hormone secretion and increase the feeling of fullness. In this study, a screening platform identified a sodium caseinate hydrolysate, LFC25, that significantly increased calcium signalling in the enteroendocrine cell line, STC-1, and as a result increased secretion of the satiety hormone, GLP-1, in a dose-dependent manner. Administration of this hydrolysate to mice reduced the cumulative food intake over an eight hour period. To determine the feasibility of LFC25 as a food ingredient, production was scaled up to 10 L and spray-dried or freeze-dried without loss of bioactivity.

Aroma compound diacetyl suppresses glucagon-like peptide-1 production and secretion in STC-1 cells.

Diacetyl is a volatile flavour compound that has a characteristic buttery aroma and is widely used in the flavour industry. The aroma of a food plays an important role in food palatability and thus intake. This study investigates the effect of diacetyl on the satiety hormone, glucagon-like peptide (GLP-1), using the enteroendocrine cell line, STC-1. Diacetyl decreased proglucagon mRNA and total GLP-1 from glucose stimulated STC-1 cells. This dampening effect on GLP-1 appears to be mediated by increasing intracellular cAMP levels, increasing synthesis of the G protein coupled receptor, GPR120, and its recruitment to the cell surface. Voltage gated Ca2+ channels, K+ATP channels and the α-gustducin taste pathway do not appear to be involved. These findings demonstrate that components contributing to food palatability suppress GLP-1. This ability of diacetyl to reduce satiety signals may contribute to overconsumption of some palatable foods.

Lactoferrin affects the adherence and invasion of Streptococcus dysgalactiae ssp. dysgalactiae in mammary epithelial cells.

Streptococcus dysgalactiae ssp. dysgalactiae is an important causative agent of bovine mastitis worldwide. Lactoferrin is an innate immune protein that is associated with many functions including immunomodulatory, antiproliferative, and antimicrobial properties. This study aimed to investigate the interactions between lactoferrin and a clinical bovine mastitis isolate, Strep. dysgalactiae ssp. dysgalactiae DPC5345. Initially a deliberate in vivo bovine intramammary challenge was performed with Strep. dysgalactiae DPC5345. Results demonstrated a significant difference in lactoferrin mRNA levels in milk cells between the control and infused quarters 7h postinfusion. Milk lactoferrin levels in the Strep. dysgalactiae DPC5345 infused quarters were significantly increased compared with control quarters at 48h postinfusion. In vitro studies demonstrated that lactoferrin had a bacteriostatic effect on the growth of Strep. dysgalactiae DPC5345 and significantly decreased the ability of the bacteria to internalize into HC-11 mammary epithelial cells. Confocal microscopy images of HC-11 cells exposed to Strep. dysgalactiae and lactoferrin further supported this effect by demonstrating reduced invasion of bacteria to HC-11 cells. The combined data suggest that a bovine immune response to Strep. dysgalactiae infection includes a significant increase in lactoferrin expression in vivo, and based on in vitro data, lactoferrin limits mammary cell invasion of this pathogen by binding to the bacteria and preventing its adherence.

Examining acute and chronic effects of short- and long-chain fatty acids on peptide YY (PYY) gene expression, cellular storage and secretion in STC-1 cells.

PURPOSE: Peptide YY (PYY) is a gastrointestinal hormone with physiological actions regulating appetite and energy homoeostasis. The cellular mechanisms by which nutrients stimulate PYY secretion from intestinal enteroendocrine cells are still being elucidated. METHODS: This study comprehensively evaluated the suitability of intestinal STC-1 cells as an in vitro model of PYY secretion. PYY concentrations (both intracellular and in culture media) with other intestinal peptides (CCK, GLP-1 and GIP) demonstrated that PYY is a prominent product of STC-1 cells. Furthermore, acute and chronic PYY responses to 15 short (SCFAs)- and long-chain (LCFAs) dietary fatty acids were measured alongside parameters for DNA synthesis, cell viability and cytotoxicity. RESULTS: We found STC-1 cells to be reliable secretors of PYY constitutively releasing PYY into cell culture media (but not into non-stimulatory buffer). We demonstrate for the first time that STC-1 cells produce PYY mRNA transcripts; that STC-1 cells produce specific time- and concentration-dependent PYY secretory responses to valeric acid; that linoleic acid and conjugated linoleic acid 9,11 (CLA 9,11) are potent PYY secretagogues; and that chronic exposure of SCFAs and LCFAs can be detrimental to STC-1 cells. CONCLUSIONS: Our studies demonstrate the potential usefulness of STC-1 cells as an in vitro model for investigating nutrient-stimulated PYY secretion in an acute setting. Furthermore, our discovery that CLA directly stimulates L-cells to secrete PYY indicates another possible mechanism contributing to the observed effects of dietary CLA on weight loss.

The effects of food components on hormonal signalling in gastrointestinal enteroendocrine cells.

The incidence of obesity and obesity-associated diseases, such as type-2 diabetes, has reached epidemic proportions in recent years. It is predicted that by 2015 over 1.5 billion consumers will be overweight or obese. Several of the current drug-based treatments on the market for weight management and appetite control either lack efficacy or are associated with adverse side-effects. There is, therefore, an opportunity to develop functional foods which are both nutritionally beneficial but which also aid in weight management. Peptides produced in the gastrointestinal tract, which function to regulate feed intake and satiety, have been identified as key targets for bioactive ingredients in functional foods. These peptides are produced and released by specialised enteroendocrine cells. Understanding the interaction of foods with these cells is vital to the development of food matrices with positive health benefits. This review describes enteroendocrine cell populations in detail and focuses on the peptides that they produce in addition to their other functions, including taste transduction. Several food-based sources of bioactives and current food products on the market with beneficial effects on satiety and glycaemia will also be discussed.

The effect of α- or ß-casein addition to waxy maize starch on postprandial levels of glucose, insulin, and incretin hormones in pigs as a model for humans.

BACKGROUND: Starch is a main source of glucose and energy in the human diet. The extent to which it is digested in the gastrointestinal tract plays a major role in variations in postprandial blood glucose levels. Interactions with other biopolymers, such as dairy proteins, during processing can influence both the duration and extent of this postprandial surge. OBJECTIVE: To evaluate the effect of the addition of bovine α- or ß-casein to waxy maize starch on changes in postprandial blood glucose, insulin, and incretin hormones [glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP-1)] in 30 kg pigs used as an animal model for humans. DESIGN: Gelatinised starch, starch gelatinised with α-casein, and starch gelatinised with ß-casein were orally administered to trained pigs (n = 8) at a level of 60 g of available carbohydrate. Pre- and postprandial glucose measurements were taken every 15 min for the first hour and every 30 min thereafter up to 180 min. Insulin, GIP, and GLP-1 levels were measured in plasma samples up to 90 min postprandial. RESULTS: Starch gelatinised with α-casein had a significantly (p < 0.05) lower peak viscosity on pasting and resulted in significantly lower glucose release at 15, 30, and 90 min postprandial compared to starch gelatinised with ß-casein. During the first 45-min postprandial, the area under the glucose curve (AUC) for starch gelatinised with α-casein was significantly (p < 0.05) lower than that for starch gelatinised with ß-casein. There was also a significant (p < 0.05) difference at T30 in GIP levels in response to the control compared to starch gelatinised with α- or ß-casein. Significant (p < 0.05) increases in several free amino acid concentrations were observed on ingestion of either α- or ß-casein gelatinised with starch at 30 and 90 min postprandial compared to starch alone. In addition, plasma levels of six individual amino acids were increased on ingestion of starch gelatinised with α-casein compared to ingestion of starch gelatinised with ß-casein. CONCLUSION: The presence of casein fractions (α- or ß-casein) in gelatinised waxy maize starch affects swelling characteristics, viscosity, and subsequent in vivo digestion as determined by glucose levels in blood postprandial.

Effect of gelatinisation of starch with casein proteins on incretin hormones and glucose transporters in vitro.

Foods that have a low glycaemic index or foods that contain slowly digestible starch are beneficial in controlling fluctuations in blood glucose and insulin levels. The study hypothesis is that gelatinisation of starch in structured casein networks provides a method for decreasing the digestion rate of the starch and, hence, minimising postprandial glucose fluctuations. This study examined the effect of starch gelatinisation with or without casein on (1) gene expression and peptide secretion levels of the incretin hormones glucagon-like peptide 1 and glucose-independent insulinotropic polypeptide and (2) gene expression of the sodium-glucose cotransporter and GLUT-2 in intestinal cell culture systems. The intestinal epithelial cell line, STC-1, and the enteroendocrine colonic cell line, Caco-2, were exposed to in vitro digested foods (starch gelatinised with α-casein, starch gelatinised with ß-casein and gelatinised starch alone). The encapsulation of starch with casein before in vitro digestion lowers levels of incretin hormone secretion. Digestion of starch gelatinised with casein also releases less glucose than starch alone as indicated by significantly (P < 0·05) lower levels of glucose transporter mRNA transcripts. Some subtle cellular response differences were observed following exposure to starch gelatinised with α- compared to ß-casein. Fractionation of α-casein and ß-casein by reverse-phase HPLC identified that fractions that differed in hydrophobicity differed significantly (P < 0·05) in their ability to promote secretion of the incretin hormones. Evidence suggests that gelatinisation of starch with casein may be a functional food ingredient that minimises blood glucose fluctuations.

Acute and chronic effects of dietary fatty acids on cholecystokinin expression, storage and secretion in enteroendocrine STC-1 cells.

Cholecystokinin (CCK) is a peptide hormone secreted from the I-cells of the intestine and it has important physiological actions related to appetite regulation and satiety. In this study we used STC-1 cells to investigate the effects of common dietary-derived fatty acids (FAs) on I-cell secretory function and metabolism. We extend earlier studies by measuring the acute and chronic effects of 11 FAs on CCK secretion, cellular CCK content, CCK mRNA levels, cellular DNA synthesis, cellular viability and cytotoxicity. FAs were selected in order to assess the importance of chain length, degree of saturation, and double bond position and conformation. The results demonstrate that secretory responses elicited by dietary FAs are highly selective. For example, altering the conformation of a double bond from cis to trans (i.e. oleic acid versus elaidic acid) completely abolishes CCK secretion. Lauric acid appears to adversely affect I-cell metabolism and arachidonic acid suppresses DNA synthesis. Our studies reveal for the first time that conjugated linoleic acid isoforms are particularly potent CCK secretagogues, which also boost intracellular stores of CCK. These actions of conjugated linoleic acid may explain satiating actions observed in dietary intervention studies.

Characterization of a cmeABC operon in a quinolone-resistant Campylobacter coli isolate of Irish origin.

In this study, a tripartite-operon-encoding efflux system together with its regulatory gene was characterized in an Irish Campylobacter coli isolate CIT-382 showing high-level resistance to nalidixic acid and ciprofloxacin. Sequence comparisons revealed significant homology between C. coli and the cmeABC operon of Campylobacter jejuni. Conservation of functional sequence domains and motifs were noted among C. coli and similar operons in unrelated organisms. A transcriptional regulatory gene cmeR located proximal to cmeABC was also identified. C. coli CIT-382 harbored the Thr-86-Ile amino acid substitution in the gyrA gene. Accumulation studies with ethidium bromide in the presence of known efflux pump inhibitors confirmed the presence of efflux pump activity in C. coli CIT-382. The efflux pump inhibitor PAbetaN had no effect on the MICs to quinolones. Our data suggest that the gyrA gene mutation is the main contributor to the high-level nalidixic acid and ciprofloxacin resistance observed in this Irish C. coli CIT-382 isolate.

Molecular-based identification and typing of Campylobacter jejuni and C. coli.

Thermophilic Campylobacter spp., mainly Campylobacter jejuni and to a lesser extent C. coli are recognized as the most common bacteriological causes of gastroenteritis in humans. As enteric infection with Campylobacter organisms cannot be distinguished from that caused by other enteric pathogens, a definitive diagnosis can only be made by isolating or detecting the organism from the feces. The epidemiology of Campylobacter enteritis has been complicated by the ubiquitous nature of the organism (commonly found as a commensal in the intestines of domestic animals, in milk, and in water). Furthermore, identification is carried out only to genus level by most clinical laboratories. Because of the biochemical similarity known to exist between C. jejuni and C. coli, the hippurate hydrolysis test is often used as the only phenotypic test capable of differentiating the two species. This test, however, has some acknowledged technical limitations and is dependent on inoculum size; results can be difficult to interpret accurately. Furthermore, almost all C. jejuni isolates possess the hippuricase gene, fewer C. jejuni isolates express the hippuricase gene. For this reason, certain polymerase chain reaction (PCR)-based species identification methods, for both C. jejuni and C. coli, and for the other thermophilic species, provide more reliable identification; they also help to highlight mixed species cultures, should they occur. However, even with these methods, false negatives or nonspecifically amplified product(s) can occur in a minority of isolates tested owing to genomic anomalies. Thus a second molecular identification method may be required in these circumstances. Gonzalez et al. developed a species-specific PCR assay for the identification of C. jejuni and C. coli based on the ceuE gene, which is involved in siderophore transport. Using this method two primer sets are employed in separate PCR amplification reactions. Another method, developed by Eyers et al., performs PCR amplification of 23S rRNA gene fragments, based on regions specific for C. jejuni, C. coli, C. lari, and C. upsaliensis. In addition, Hani and Chan developed a PCR assay that detected and amplified the hippuricase gene. This molecular approach may offer a more reliable means of identifying C. jejuni strains compared with the phenotypic hippurate hydrolysis test alone.

Molecular genotyping of Irish rotavirus strains.

Rotavirus is the primary etiological agent of gastroenteritis in infants and young children worldwide. In developing countries, it is estimated that rotavirus is responsible for one-third of all diarrhea-associated hospitalizations and 873,000 deaths annually. In industrialized countries, where mortality from rotavirus is low, infection is widespread, and nearly all children experience an episode of rotavirus diarrhea in the first 3-5 yr of life. Rotaviruses have important antigenic specificities including serogroup and serotype, and all viruses are classified accordingly. They are divided into seven morphologically indistinguishable but antigenically defined serogroups, delineated A through G. The human infecting rotaviruses include groups A, B, and C, and it is well documented that group A rotaviruses are the major causative agents of diarrheal diseases in children. They are responsible for 125 million cases of diarrhea annually. Within each serogroup, distinct serotypes exist. In group A rotavirus, serotype is specified by two viral proteins, VP4 and VP7. The neutralizing antibody response that is evoked by the antigenic determinants on VP4 and VP7 play an important role in protective immunity. The rotavirus genome consists of 11 double-stranded (ds) RNA segments, and each genomic segment encodes a different protein. A dual system of reporting rotavirus serotype exists because the VP4 and VP7 proteins are encoded by different genes and thus can segregate independently. The serotypes derived from VP7 are defined as G-serotypes. Currently 14 G-serotypes have been identified, and only 10 of these have been recovered from humans. The predominating G-types worldwide are G1, G2, G3, and G4, with G1 being the most prevalent type. Serotypes G5, G6, G8-G10, and G12 are rarely identified in humans and are usually recovered from animals. However, some of these unconventional types are now being frequently reported in humans, including G5, G8, and G9.

Molecular characterization of class 1 integrons from Irish thermophilic Campylobacter spp.

OBJECTIVES: In this study a large random collection (n = 378) of Irish thermophilic Campylobacter isolates were investigated for the presence of integrons, genetic elements associated with the dissemination of antimicrobial resistance. METHODS: Purified genomic DNA from each isolate was analysed by PCR for the presence of class 1 integrons. Four gene cassette-associated amplicons were completely characterized. RESULTS: Sixty-two of the isolates possessed a complete class 1 integron with a recombined gene cassette located within a 1.0 kb amplicon containing an aadA2 gene. This cassette was present in both Campylobacter jejuni and Campylobacter coli isolates and following sequence analysis was shown to be similar to sequences recently reported in Salmonella enterica Hadar and on an 85 kb plasmid conferring quinolone resistance in Escherichia coli. CONCLUSIONS: Aminoglycoside aadA2-encoding class 1 integrons were identified among unrelated Campylobacter spp. Amino acid sequence comparisons revealed identical structures in both Salmonella and E. coli. The presence of class 1 integrons in Campylobacter spp. may be significant should these organisms enter the food chain and especially when antimicrobial treatment for severe infections is being considered.

Antimicrobial resistance and genetic diversity of Shigella sonnei isolates from western Ireland, an area of low incidence of infection.

Shigella sonnei is a significant cause of gastroenteritis in both developing and industrialized countries. Definition of the diversity and antimicrobial susceptibility of S. sonnei isolates may be helpful in the management of individual cases and outbreaks. Antimicrobial susceptibility testing and pulsed-field gel electrophoresis (PFGE) were performed with 67 isolates of S. sonnei predominantly (n = 59) from three counties in the west of Ireland. Phage typing (n = 17), plasmid profiling (n = 28), and integron analysis (n = 24) were performed with subsets of strains. PFGE typing permitted recognition of two major clusters: PFGE type A (n = 53) and PFGE type B (n = 14). PFGE type A was associated with resistance to ampicillin, streptomycin, and sulfonamides (51 of 53 isolates), and those that were phage typed (n = 6) were phage type 3. PFGE type B was associated with resistance to streptomycin, sulfonamides, tetracycline, and trimethoprim (11 of 14 isolates) and phage type 6 (9 of 11 isolates). Fifteen different plasmid profiles were identified among the 28 isolates analyzed. A class 2 integron was present in all 14 PFGE type B isolates. One of these isolates also contained a class 1 integron and showed a unique variant of the PFGE type B pattern. Sequence analysis of the gene cassette structures contained within these integrons identified distinct open reading frames that encoded determinants of resistance to trimethoprim, streptomycin, and streptothricin. Our data demonstrate two predominant PFGE types among S. sonnei isolates circulating in this region. The limited diversity of the S. sonnei isolates in this region means that detection of isolates indistinguishable by PFGE and according to their antibiograms in two or more patients is not persuasive evidence of a common-source food- or waterborne outbreak. Indistinguishable plasmid profiles in addition to indistinguishable PFGE and antibiogram types may be more suggestive of an epidemiologically relevant link between cases.