Prevalence and characteristics of bacteria and host factors in an outbreak situation of antibiotic-associated diarrhoea

Effect of the combination of Lactobacillus acidophilus (probiotic) with vitamin K3 and vitamin E on Escherichia coli and Staphylococcus aureus: An in vitro pathogen model

The gut microbiota plays a key role in maintaining health and regulating the host's immune response. The use of probiotics and concomitant vitamins can increase mucus secretion by improving the intestinal microbial population and prevent the breakdown of tight junction proteins by reducing lipopolysaccharide concentration. Changes in the intestinal microbiome mass affect multiple metabolic and physiological functions. Studies on how this microbiome mass and the regulation in the gastrointestinal tract are affected by probiotic supplements and vitamin combinations have attracted attention. The current study evaluated vitamins K and E and probiotic combinations effects on Escherichia coli and Staphylococcus aureus. Minimal inhibition concentrations of vitamins and probiotics were determined. In addition, inhibition zone diameters, antioxidant activities and immunohistochemical evaluation of the cell for DNA damage were performed to evaluate the effects of vitamins and probiotics. At the specified dose intervals, L. acidophilus and vitamin combinations inhibit the growth of Escherichia coli and Staphylococcus aureus. It could thus contribute positively to biological functions by exerting immune system‑strengthening activities.

A worldwide systematic review and meta-analysis of bacteria related to antibiotic-associated diarrhea in hospitalized patients

INTRODUCTION

Antibiotic-associated diarrhea (AAD) is a major hospital problem and a common adverse effect of antibiotic treatment. The aim of this study was to investigate the prevalence of the most important bacteria that cause AAD in hospitalized patients.

MATERIALS AND METHODS

PubMed, Web of Science and Scopus databases were searched using multiple relevant keywords and screening carried out based on inclusion/exclusion criteria from March 2001 to October 2021. The random-effects model was used to conduct the meta-analysis.

RESULTS

Of the 7,377 identified articles, 56 met the inclusion criteria. Pooling all studies, the prevalence of Clostridioides (Clostridium) difficile, Clostridium perfringens, Klebsiella oxytoca, and Staphylococcus aureus as AAD-related bacteria among hospitalized patients were 19.6%, 14.9%, 27%, and 5.2%, respectively. The prevalence of all four bacteria was higher in Europe compared to other continents. The highest resistance of C. difficile was estimated to ciprofloxacin and the lowest resistances were reported to chloramphenicol, vancomycin, and metronidazole. There was no or little data on antibiotic resistance of other bacteria.

CONCLUSIONS

The results of this study emphasize the need for a surveillance program, as well as timely public and hospital health measures in order to control and treat AAD infections.

A Case of Postoperative Methicillin-Resistant Staphylococcus aureus Enterocolitis in an 81-Year-Old Man and Review of the Literature

Patient: Male, 81-year-old

Final Diagnosis: Methicillin-resistant Staphylococcus aureus bacteremia • Methicillin-resistant Staphylococcus aureus enterocolitis

Symptoms: Diarrhea • sepsis

Medication: —

Clinical Procedure: Computed tomography • echocardiography • polymerase chain reaction • whipple procedure

Specialty: Gastroenterology and Hepatology • Infectious Diseases • Surgery

High Clostridium difficile Infection among HIV-Infected Children with Diarrhea in a Tertiary Hospital in Mwanza, Tanzania

Clostridium difficile causes a million of illnesses each year worldwide and can affect people of all ages. Limited data exist on the prevalence of C. difficile infections (CDI) among children below five years of age in developing countries. This study is aimed at determining the prevalence, associated factors, and outcome of the Clostridium difficile infection among children with diarrhea attending a tertiary hospital in Mwanza, Tanzania. Stool samples were collected and cultured anaerobically to isolate Clostridium difficile, followed by C. difficile toxin A and B assay and ribotyping. A total of 301 children with diarrhea were enrolled. A total of 22 (7.31%, 95% CI: 0.89-0.95) nonrepetitive stool samples were positive for Clostridium difficile. Eighteen (81%) of C. difficile isolates were toxigenic, and 16 (72.7%) had unknown ribotypes. Independent predictors of positive C. difficile were as follows: positive HIV status, hospital stay of more than four days, high stool leukocyte count, and watery stool. Clostridium difficile-positive children had significantly higher median duration of the diarrhea than those without C. difficile. Clinicians should consider C. difficile as a possible cause of diarrhea in children living in developing countries and institute appropriate management to prevent associated morbidities and mortalities. Furthermore, there is a need of joint effort to improve C. difficile diagnosis and surveillance in developing countries to establish the unknown epidemiology of CDI in these countries.

Presence of Clostridium difficile in pig faecal samples and wild animal species associated with pig farms

AIMS

To determine the presence of Clostridium difficile on fattening pig farms in north-eastern Spain.

METHODS AND RESULTS

Twenty-seven farms were sampled. Pools of pig faecal samples (n = 210), samples of intestinal content from common farm pest species (n = 95) and environment-related samples (n = 93) were collected. Isolates were tested for toxin genes of C. difficile, and typed by PCR-ribotyping and toxinotyping. The minimal inhibitory concentrations of six antimicrobial agents were determined using Etest. Thirty-four isolates were obtained from 12 farms, and 30 (88·2%) had toxin genes. Seven ribotypes were identified. Ribotype 078 and its variant 126 were predominant (52·9%). The same ribotypes were isolated from different animal species on the same farm. None of the isolates were resistant to metronidazole or vancomycin.

CONCLUSIONS

Clostridium difficile was common within the pig farm environment. Most of the positive samples came from pest species or were pest-related environmental samples.

SIGNIFICANCE AND IMPACT OF THE STUDY

Pest species were colonized with toxigenic and antimicrobial-resistant C. difficile strains of the same ribotypes that are found in humans and pigs. Rodents and pigeons may transmit toxigenic and antimicrobial-resistant C. difficile strains that are of the same ribotypes as those occuring in humans.

A systematic review for pursuing the presence of antibiotic associated enterocolitis caused by methicillin resistant Staphylococcus aureus

BACKGROUND

Although it has received a degree of notoriety as a cause for antibiotic-associated enterocolitis (AAE), the role of methicillin resistant Staphylococcus aureus (MRSA) in the pathogenesis of this disease remains enigmatic despite a multitude of efforts, and previous studies have failed to conclude whether MRSA can cause AAE. Numerous cases of AAE caused by MRSA have been reported from Japan; however, due to the fact that these reports were written in the Japanese language and a good portion lacked scientific rigor, many of these reports went unnoticed.

METHODS

We conducted a systematic review of pertinent literatures to verify the existence of AAE caused by MRSA. We modified and applied methods in common use today and used a total of 9 criteria to prove the existence of AAE caused by Klebsiella oxytoca. MEDLINE/Pubmed, Excerpta Medica Database (EMBASE), the Cochrane Database of Systematic Reviews, and the Japan Medical Abstract Society database were searched for studies published prior to March 2013.

RESULTS

A total of 1,999 articles were retrieved for evaluation. Forty-five case reports/series and 9 basic studies were reviewed in detail. We successfully identified articles reporting AAE with pathological and microscopic findings supporting MRSA as the etiological agent. We also found comparative studies involving the use of healthy subjects, and studies detecting probable toxins. In addition, we found animal models in which enteritis was induced by introducing MRSA from patients. Although we were unable to identify a single study that encompasses all of the defined criteria, we were able to fulfill all 9 elements of the criteria by collectively analyzing multiple studies.

CONCLUSIONS

AAE caused by MRSA-although likely to be rarer than previous Japanese literatures have suggested-most likely does exist.

Molecular epidemiology of Clostridium difficile strains from nosocomial-acquired infections

The purpose of this study is to analyze isolates of Clostridium difficile from patients with nosocomial acquired infection in respect to their molecular type and antimicrobial susceptibility. Fifty-nine randomly selected clinical isolates were characterized. Molecular typing was performed by rep-PCR (DiversiLab). Isolates were tested by disk diffusion towards 11 different antibiotics. All isolates were susceptible to metronidazole and vancomycin. Fifty five (93 %) isolates were resistant to erythromycin and fifty six (95 %) exhibited resistance to both clindamycin and moxifloxacin. Twenty rep-PCR types were identified, but most clinical isolates formed four major rep-PCR clusters (A1 24/59, 40 %; A2 20/59, 33 %; A3 5/59, 8 %; A4 3/59, 5 %). These results show high genetic variability, which demonstrate clearly the complexity of the strains of C. difficile and also show an increasing rate of resistance to fluoroquinolones in our region emphasizing the importance of implementing surveillance programs in order to prevent further spread of resistance in C. difficile.

A Lactobacillus casei Shirota probiotic drink reduces antibiotic-associated diarrhoea in patients with spinal cord injuries: a randomised controlled trial

Certain probiotics may prevent the development of antibiotic-associated diarrhoea (AAD) and Clostridium difficile-associated diarrhoea (CDAD), but their effectiveness depends on both strain and dose. There are few data on nutritional interventions to control AAD/CDAD in the spinal cord injury (SCI) population. The present study aimed to assess (1) the efficacy of consuming a commercially produced probiotic containing at least 6·5 × 10⁹ live Lactobacillus casei Shirota (LcS) in reducing the incidence of AAD/CDAD, and (2) whether undernutrition and proton pump inhibitors (PPI) are risk factors for AAD/CDAD. A total of 164 SCI patients (50·1 (sd 17·8) years) with a requirement for antibiotics (median 21 d, range 5-366) were randomly allocated to receive LcS (n 76) or no probiotic (n 82). LcS was given once daily for the duration of the antibiotic course and continued for 7 days thereafter. Nutritional risk was assessed by the Spinal Nutrition Screening Tool. The LcS group had a significantly lower incidence of AAD (17·1 v. 54·9%, P< 0·001). At baseline, 65% of patients were at undernutrition risk. Undernutrition (64·1 v. 33·3%, P< 0·01) and the use of PPI (38·4 v. 12·1 %, P= 0·022) were found to be associated with AAD. However, no significant difference was observed in nutrient intake between the groups. The multivariate logistic regression analysis identified poor appetite ( < 1/2 meals eaten) (OR 5·04, 95% CI 1·28, 19·84) and no probiotic (OR 8·46, 95% CI 3·22, 22·20) as the independent risk factors for AAD. The present study indicated that LcS could reduce the incidence of AAD in hospitalised SCI patients. A randomised, placebo-controlled study is needed to confirm this apparent therapeutic success in order to translate into improved clinical outcomes.

Potential protective role of linezolid against Clostridium difficile infection

Clostridium difficile infection (CDI) is one of the main causes of diarrhoea associated with antimicrobial therapy. Antibiotics with good 'in vitro' activity against C. difficile could protect patients from developing CDI. In this study, the potential of linezolid to protect patients with ventilator-associated pneumonia (VAP) from developing CDI was assessed. Over a 4-year period, a cohort of patients who developed VAP following major heart surgery (MHS) in Gregorio Marañón General Hospital (Madrid, Spain) was retrospectively analysed. Patients were divided into those who developed CDI in the post-operative period and those who did not. Variables associated with the development of CDI were analysed, including the role of antimicrobial therapy. Overall, 1934 patients underwent MHS; 90 patients were excluded due to intra-operative or early post-operative (first 48h) death, leaving a study population of 1844 patients, of which 105 cases had VAP. Complete clinical data were available in 91 cases. CDI occurred in 22 patients (24.2%). When comparing VAP cases with and without CDI, EuroSCORE and overall antibiotics prescribed were not significantly different. Patients with chronic renal failure (CRF) were more prone to develop CDI than those without CRF (32% vs. 13%; P=0.04), and patients without [corrected] CDI received more doses of linezolid than those with [corrected] CDI [12.4±9.7 defined daily doses (DDDs) vs. 6.7±4.0 DDDs; P=0.007]. Multivariate analysis confirmed that receiving more DDDs of linezolid protects from developing CDI (hazard ratio=0.908, 95% confidence interval 0.83-0.99; P=0.04). This work is retrospective and addresses a very particular population, but it is the first to suggest the potential impact of linezolid against CDI.

[Nosocomial diarrhea]

Hospital acquired or nosocomial diarrhea affects up to one third of hospitalized patients. It increases mortality rates as well as length and costs of the hospital stay. Drug side effects are the predominant cause of nosocomial diarrhea whilst clostridium difficile is the most common infectious agent, whose development is closely linked to antibiotic usage. The causal therapy of mild clostridium difficile infections is controversially discussed. Nevertheless, the use of Metronidazol for mild cases and of vancomycin for severe forms of the disease is recommended. Diarrhea outbreaks might be caused by viruses and less often by Salmonella and Listeria. Norovirus infections are of outstanding importance. Rehydration and isolation to prevent the spread of this highly contagious virus are the only reasonable options as we still lack a proper therapy.

Effect of lifestyle factors on Staphylococcus aureus gut colonization in Swedish and Italian infants

In recent years, Staphylococcus aureus has become a common bowel colonizer in Swedish infants. We aimed to identify host factors that determine such colonization. Stool samples from 100 Italian and 100 Swedish infants were obtained on seven occasions during the first year of life and cultured quantitatively for S. aureus. In a subgroup of infants in each cohort, individual strains were identified by random amplified polymorphic DNA analysis. Colonization at each time-point was related to delivery mode, siblings in family and antibiotic treatment. In total, 66% of the Italian and 78% of the Swedish infants had S. aureus in their stools on at least one time-point (p 0.08) and 4% of Italian and 27% of Swedish infants were positive on at least six of the seven time-points investigated (p 0.0001). Most infants analysed regarding strain carriage harboured a single strain in their microbiota for several months. The S. aureus stool populations in colonized infants decreased from 10(7) to 10(4) colony-forming units/g between 1 week and 1 year of age in both cohorts. In multivariate analysis, the strongest predictor for S. aureus colonization was being born in Sweden (OR 3.4 at 1 week of age, p 0.002). Having (an) elder sibling(s) increased colonization at peak phase (OR 1.8 at 6 months, p 0.047). Antibiotic treatment was more prevalent among Italian infants and correlated negatively with S. aureus colonization at 6 months of age (OR 0.3, p 0.01). To conclude, S. aureus is a more common gut colonizer in Swedish than Italian infants, a fact that could not be attributed to feeding or delivery mode.

Effect of probiotic Lactobacillus (Lacidofil® cap) for the prevention of antibiotic-associated diarrhea: a prospective, randomized, double-blind, multicenter study

Antibiotic-associated diarrhea (AAD) is a common complication of antibiotic use. There is growing interest in probiotics for the treatment of AAD and Clostridium difficile infection because of the wide availability of probiotics. The aim of this multicenter, randomized, placebo-controlled, double-blind trial was to assess the efficacy of probiotic Lactobacillus (Lacidofil® cap) for the prevention of AAD in adults. From September 2008 to November 2009, a total of 214 patients with respiratory tract infection who had begun receiving antibiotics were randomized to receive Lactobacillus (Lacidofil® cap) or placebo for 14 days. Patients recorded bowel frequency and stool consistency daily for 14 days. The primary outcome was the proportion of patients who developed AAD within 14 days of enrollment. AAD developed in 4 (3.9%) of 103 patients in the Lactobacillus group and in 8 (7.2%) of 111 patients in the placebo group (P=0.44). However, the Lactobacillus group showed lower change in bowel frequency and consistency (50/103, 48.5%) than the placebo group (35/111, 31.5%) (P=0.01). Although the Lacidofil® cap does not reduce the rate of occurrence of AAD in adult patients with respiratory tract infection who have taken antibiotics, the Lactobacillus group maintains their bowel habits to a greater extent than the placebo group.

Resistance to linezolid in a porcine Clostridium perfringens strain carrying a mutation in the rplD gene encoding the ribosomal protein L4

Coresistance to human reserve antibiotics can be selected by antibiotics used in veterinary medicine. A Clostridium perfringens strain isolated from pig manure was resistant to the reserve drug linezolid and, simultaneously, resistant against florfenicol and erythromycin. We detected a new mutation in a highly conserved region of rplD, encoding protein L4 of the 50S ribosomal subunit. This is the first genetic substantiation of linezolid resistance in the genus Clostridium.

Nosocomial and antibiotic-associated diarrhoea caused by organisms other than Clostridium difficile

Most cases of nosocomial and antibiotic-associated diarrhoea are caused by alteration of the physiological gut microflora. This alteration leads to reduced microbial metabolism of carbohydrates and primary bile acids, resulting in osmotic or secretory forms of diarrhoea. Moreover, facultative enteropathogens may experience a growth advantage due to the antibiotic-induced microflora alteration that, in turn, can harm the gut mucosa by the toxins they produce. Clostridium difficile is the major infectious agent leading to pseudomembranous colitis. However, there is increasing evidence that certain other pathogens such as enterotoxin-producing Clostridium perfringens, Staphylococcus aureus and Klebsiella oxytoca can induce mucosal deterioration and diarrhoea after antibiotic use. But, as with C. difficile, these facultative enteropathogens can also be found in the healthy population. Their contribution to disease is, therefore, controversial and their presence in the stools of antibiotic-associated diarrhoea patients is often claimed to be mere colonisation. In this respect, the causal relationship of each suspected pathogen with the development of intestinal disease has to be proved clinically and experimentally.

Characterization of Clostridium species utilizing liquid chromatography/mass spectrometry of intact proteins

A method for biomarker candidate discovery and strain level pathogen characterization using liquid chromatography/mass spectrometry (LC/MS) with electrospray ionization is described. This method was applied to two pathogenic Clostridium species: C. difficile and C. perfringens. Seven marker proteins per species (fourteen total) were successfully implemented to speciate unknowns during a blind study and could enhance serological and genetic approaches by serving as new targets for detection. Two sets of C. perfringens isolates that were 100% similar by pulsed-field gel electrophoresis (PFGE) were distinguished using LC/MS, demonstrating the high specificity of this approach. The use of LC/MS is less labor intensive than PFGE, affords greater specificity than real-time PCR, and requires no primers or antibodies.

Antibiotic-associated diarrhea: epidemiology, trends and treatment

A common complication of antibiotic use is the development of gastrointestinal disease. This complication ranges from mild diarrhea to pseudomembranous colitis. Outbreaks of antibiotic-associated diarrhea (AAD) may also occur in healthcare settings, usually caused by Clostridium difficile. AAD typically occurs in 5-35% of patients taking antibiotics and varies depending upon the specific type of antibiotic, the health of the host and exposure to pathogens. The pathogenesis of AAD may be mediated through the disruption of the normal microbiota resulting in pathogen overgrowth or metabolic imbalances. The key to addressing AAD is prompt diagnosis followed by effective treatment and institution of control measures. Areas of active research include the search for other etiologies and more effective treatments.

Intestinal carriage of Staphylococcus aureus: how does its frequency compare with that of nasal carriage and what is its clinical impact?

The bacterial species Staphylococcus aureus, including its methicillin-resistant variant (MRSA), finds its primary ecological niche in the human nose, but is also able to colonize the intestines and the perineal region. Intestinal carriage has not been widely investigated despite its potential clinical impact. This review summarizes literature on the topic and sketches the current state of affairs from a microbiological and infectious diseases' perspective. Major findings are that the average reported detection rate of intestinal carriage in healthy individuals and patients is 20% for S. aureus and 9% for MRSA, which is approximately half of that for nasal carriage. Nasal carriage seems to predispose to intestinal carriage, but sole intestinal carriage occurs relatively frequently and is observed in 1 out of 3 intestinal carriers, which provides a rationale to include intestinal screening for surveillance or in outbreak settings. Colonization of the intestinal tract with S. aureus at a young age occurs at a high frequency and may affect the host's immune system. The frequency of intestinal carriage is generally underestimated and may significantly contribute to bacterial dissemination and subsequent risk of infections. Whether intestinal rather than nasal S. aureus carriage is a primary predictor for infections is still ill-defined.

Enhanced production of phospholipase C and perfringolysin O (alpha and theta toxins) in a gatifloxacin-resistant strain of Clostridium perfringens

Clostridium perfringens-induced gas gangrene is mediated by potent extracellular toxins, especially alpha toxin (a phospholipase C [PLC]) and theta toxin (perfringolysin O [PFO], a thiol-activated cytolysin); and antibiotic-induced suppression of toxin synthesis is an important clinical goal. The production of PLC and PFO by a gatifloxacin-induced, fluoroquinolone-resistant mutant strain of C. perfringens, strain 10G, carrying a stable mutation in DNA gyrase was compared with that of the wild-type (WT) parent strain. Zymography (with sheep red blood cell and egg yolk overlays) and time course analysis [with hydrolysis of egg yolk lecithin and O-(4 nitrophenyl-phosphoryl)choline] demonstrated that strain 10G produced more PLC and PFO than the WT strain. Increased toxin production in strain 10G was not related either to differences in growth characteristics between the wild-type and the mutant strain or to nonsynonymous polymorphisms in PLC, PFO, or their known regulatory proteins. Increased PLC and PFO production by strain 10G was associated with increased cytotoxic activity for HT-29 human adenocarcinoma cells and with increased platelet-neutrophil aggregate formation. Four other gatifloxacin-induced gyrase mutants did not show increased toxin production, suggesting that gatifloxacin resistance was not always associated with increased toxin production in all strains of C. perfringens. This is the first report of increased toxin production in a fluoroquinolone-resistant strain of C. perfringens.

Monocyte chemoattractant protein-1 production by intestinal myofibroblasts in response to staphylococcal enterotoxin a: relevance to staphylococcal enterotoxigenic disease

Food poisoning due to staphylococcal enterotoxins A and B (SEA and SEB) affects hundreds of thousands of people annually. SEA and SEB induce massive intestinal cytokine production, which is believed to be the key factor in staphylococcal enterotoxin enteropathy. MHC class II molecules are the major receptors for staphylococcal enterotoxins. We recently demonstrated that normal human subepithelial intestinal myofibroblasts (IMFs) express MHC class II molecules. We hypothesized that IMFs are among the first cells to respond to staphylococcal enterotoxins and contribute to the cytokine production associated with staphylococcal enterotoxin pathogenesis. We demonstrated here that primary cultured IMFs bind staphylococcal enterotoxins in a MHC class II-dependent fashion in vitro. We also demonstrated that staphylococcal enterotoxins can cross a CaCo-2 epithelial monolayer in coculture with IMFs and bind to the MHC class II on IMFs. IMFs responded to SEA, but not SEB, exposure with 3- to 20-fold increases in the production of proinflammatory chemokines (MCP-1, IL-8), cytokines (IL-6), and growth factors (GM-CSF and G-CSF). The SEA induction of the proinflammatory mediators by IMFs resulted from the efficient cross-linking of MHC class II molecules because cross-linking of class II MHC by biotinylated anti-HLA-DR Abs induced similar cytokine patterns. The studies presented here show that MCP-1 is central to the production of other cytokines elicited by SEA in IMFs because its neutralization with specific Abs prevented the expression of IL-6 and IL-8 by IMFs. Thus, MCP-1 may play a leading role in initiation of inflammatory injury associated with staphylococcal enterotoxigenic disease.

Laboratory diagnosis of antibiotic-associated diarrhea: a Polish pilot study into the clinical relevance of Clostridium difficile and Clostridium perfringens toxins

In the present study, we investigated the prevalence of the Clostridium perfringens enterotoxin (CPEnt) in stool samples originally submitted for detection of Clostridium difficile toxins. Fifty-two fecal samples from inpatients were screened simultaneously for C. difficile and C. perfringens toxins: 75% of the specimens were positive for TcdA/TcdB toxins, 40% were positive for CPEnt, and 31% gave positive test results for both. It is interesting to note that only a relatively small number of C. perfringens isolates were positive for the cpe gene. All C. difficile strains were susceptible to metronidazole, but intermediate metronidazole resistance was documented for the C. perfringens isolates, which decreased upon in vitro passaging in the absence of metronidazole. We recommend that CPEnt detection should be included when diagnosing patients with presumed antibiotic-associated diarrhea.

The mosaic nature of intergenic 16S-23S rRNA spacer regions suggests rRNA operon copy number variation in Clostridium difficile strains

Clostridium difficile is a major spore-forming environmental pathogen that causes serious health problems in patients undergoing antibiotic therapy. Consequently, reliable and sensitive methods for typing individual strains are required for epidemiological and environmental studies. Ribotyping is generally considered the best method, but it fails to account for sequence diversity which might exist in intergenic 16S-23S rRNA spacer regions (ISRs) within and among strains of this organism. Therefore, this study was undertaken to compare the sequence of each individual ISR in five strains of C. difficile to explore the extent of this diversity and see whether such information might provide the basis for more sensitive and discriminatory strain typing methods. After targeted PCR amplification, cloning, and sequencing, the diversity of the ISRs was used as a measure of rRNA operon copy number. In C. difficile strains 630, ATCC 43593, A, and B, 11, 11, 7, and 8 ISR length variants, respectively, were found (containing different combinations of sequence groups [i to xiii]), suggesting 11, 11, 7, and 8 rrn copies in the respective strains. Many ISRs of the same length differed markedly in their sequences, and some of these were restricted in occurrence to a single strain. Most of these ISRs did not contain any tRNA genes, and only single copies of the tRNA(Ala) gene were found in those that did. The presence of ISR sequence groups (i to xiii) varied between strains, with some found in one, two, three, four, or all five strains. We conclude that the intergenic 16S-23S rRNA spacer regions showed a high degree of diversity, not only among the rrn operons in different strains and different rrn copies in a single strain but also among ISRs of the same length. It appears that C. difficile ISRs vary more at the inter- and intragenic levels than those of other species as determined by empirical comparison of sequences. The precise characterization of these sequences has demonstrated a high level of mosaic sequence block rearrangements that are present or absent in multiple strain-variable rrn copies within and between five different strains of C. difficile.

Staphylococcus aureus adheres to human intestinal mucus but can be displaced by certain lactic acid bacteria

There is increasing evidence that Staphylococcus aureus may colonize the intestinal tract, especially among hospitalized patients. As Staph. aureus has been found to be associated with certain gastrointestinal diseases, it has become important to study whether this bacterium can colonize the intestinal tract and if so, whether it is possible to prevent colonization. Adhesion is the first step in colonization; this study shows that Staph. aureus adheres to mucus from resected human intestinal tissue. Certain lactic acid bacteria (LAB), mainly commercial probiotics, were able to reduce adhesion and viability of adherent Staph. aureus. In displacement assays the amount of adherent Staph. aureus in human intestinal mucus was reduced 39-44% by Lactobacillus rhamnosus GG, Lactococcus lactis subsp. lactis and Propionibacterium freudenreichii subsp. shermanii. Moreover, adherent Lactobacillus reuteri, Lc. lactis and P. freudenreichii reduced viability of adherent Staph. aureus by 27-36%, depending on the strain, after 2 h incubation. This was probably due to the production of organic acids and hydrogen peroxide and possibly in the case of L. reuteri to the production of reuterin. This study shows for the first time that Staph. aureus can adhere to human intestinal mucus and adherent bacteria can be displaced and killed by certain LAB strains via in situ production of antimicrobial substances.

Meta-analysis of probiotics for the prevention of antibiotic associated diarrhea and the treatment of Clostridium difficile disease

CONTEXT

Antibiotic-associated diarrhea (AAD) is a common complication of most antibiotics and Clostridium difficile disease (CDD), which also is incited by antibiotics, is a leading cause of nosocomial outbreaks of diarrhea and colitis. The use of probiotics for these two related diseases remains controversial.

OBJECTIVE

To compare the efficacy of probiotics for the prevention of AAD and the treatment of CDD based on the published randomized, controlled clinical trials.

DATA SOURCES

PubMed, Medline, Google Scholar, NIH registry of clinical trials, metaRegister, and Cochrane Central Register of Controlled Trials were searched from 1977 to 2005, unrestricted by language. Secondary searches of reference lists, authors, reviews, commentaries, associated diseases, books, and meeting abstracts.

STUDY SELECTION

Trials were included in which specific probiotics given to either prevent or treat the diseases of interest. Trials were required to be randomized, controlled, blinded efficacy trials in humans published in peer-reviewed journals. Trials that were excluded were pre-clinical, safety, Phase 1 studies in volunteers, reviews, duplicate reports, trials of unspecified probiotics, trials of prebiotics, not the disease being studied, or inconsistent outcome measures. Thirty-one of 180 screened studies (totally 3,164 subjects) met the inclusion and exclusion criteria.

DATA EXTRACTION

One reviewer identified studies and abstracted data on sample size, population characteristics, treatments, and outcomes.

DATA SYNTHESIS

From 25 randomized controlled trials (RCTs), probiotics significantly reduced the relative risk of AAD (RR = 0.43, 95% CI 0.31, 0.58, p < 0.001). From six randomized trials, probiotics had significant efficacy for CDD (RR = 0.59, 95% CI 0.41, 0.85, p = 0.005).

CONCLUSION

A variety of different types of probiotics show promise as effective therapies for these two diseases. Using meta-analyses, three types of probiotics (Saccharomyces boulardii, Lactobacillus rhamnosus GG, and probiotic mixtures) significantly reduced the development of antibiotic-associated diarrhea. Only S. boulardii was effective for CDD.