The normal microbial flora

Non-pathogenic bacterial flora may inhibit colonization by methicillin-resistant Staphylococcus aureus in extremely low birth weight infants

OBJECTIVES

To evaluate our hypothesis that non-pathogenic bacterial flora inhibit later colonization with methicillin-resistant Staphylococcus aureus (MRSA) in extremely low birth weight (ELBW) infants, we performed a retrospective investigation of the association between non-pathogenic bacterial flora and later inhibition of colonization by MRSA in ELBW infants.

METHODS

A total of 110 preterm infants with birth weight <1,000 g admitted to the Neonatal Intensive Care Unit of Nagano Children's Hospital from January 1997 to December 2003 were analyzed retrospectively with regard to colonization by MRSA during hospitalization. We investigated the incidence of MRSA colonization in 56 infants with non-pathogenic bacterial flora in the oral cavity during the first week after birth and compared them with 54 infants lacking non-pathogenic bacteria.

RESULTS

Incidence rate of colonization by MRSA at postnatal week 6 was significantly lower in infants with non-pathogenic bacterial flora in the oral cavity (32.1%) than in infants without such bacteria during the first week of life (77.8%; p < 0.001).

CONCLUSIONS

The present results suggest an important role for non-pathogenic bacterial flora in the oral cavity during early life in prevention of later MRSA colonization in ELBW infants.

Microbiologic investigations for head and neck infections

A variety of methods, including direct examination of stained smears, antigen detection, routine and special cultures, and histopathologic evaluation are available for investigation of head and neck infections. Newer rapid molecular techniques with increased sensitivity and specificity are becoming available at many centers. Evaluation of specific causes in head and neck infections is complicated by the tendency for polymicrobial infections, difficulty in obtaining adequate specimens, and the presence of a diverse endogenous microflora at various mucosal sites that also can include true pathogens. These aspects of laboratory investigation for head and neck infections are reviewed in this article.

Colonization and impact of disease and other factors on intestinal microbiota

The aim of this study was to review the process of microbial colonization and the environmental and host factors that influence colonization and microbial succession. The impact of some diseases on intestinal microbiota composition is also described. Microbial colonization of the gut by maternal vaginal and fecal bacteria begins during and after birth. During the first 2 years of life, specific microbes become established in a process designated microbial succession. Microbial succession in the gastrointestinal tract is influenced by numerous external and internal host-related factors, and by the second year of life, the intestinal microbiota composition is considered identical to that of adults. Nevertheless, intestinal microbiota in both infants and adults remain incompletely characterized and their diversity poorly defined. The main explanation is that many intestinal bacteria that live in an anaerobic environment are difficult or impossible to culture outside the intestine. However, recent advances in molecular biology techniques have initiated the description of new bacteria species. The composition of gut microbiota can be modulated by host, environmental, and bacterial factors, and strong evidence has emerged of substantial modifications during illness or exposure to threatening experiences. It has been postulated that improvements in hygienic measures have led to an increase in allergic diseases ("hygiene hypothesis"). Alterations in gut microbiota and their functions have been widely associated with many chronic and degenerative diseases, including inflammatory bowel disease, colon cancer, and rheumatoid arthritis.

Management of pulmonary aspiration

Pulmonary aspiration of gastric contents in the perioperative phase is associated with increased postoperative morbidity and mortality. For the management of aspiration, differentiation between acid-associated aspiration pneumonitis and aspiration pneumonia as a consequence of a secondary bacterial contamination is of crucial importance. The incidence of aspiration in elective surgery is 1 per 2000-3000 anaesthesias in adults. In children, it is slightly more common with 1 per 1200-2600 anaesthesias. In the context of emergency anaesthesias the incidence of aspiration is three to four times higher. The risk particularly increases with recent ingestion of solid food or fluids, with older patients, with pregnant women, and with consciousness-reduced patients. Besides giving a review of the pathophysiology, incidence, and the risk factors of aspiration, this article places emphasis on the practical management of this anaesthesia-associated complication. Cricoid pressure, as a non-evidence-based but clinically wide-spread method in the context of the prophylaxis of aspiration, is discussed critically. The main part deals with strategies to structure the management of aspiration by use of scientific concepts based on medical crisis management. For this, an algorithm based on current scientific investigations is presented.

Digestive tract microbiota in healthy volunteers

PURPOSE

The aim of this study was to standardize the methods of sample collection of mucus from the digestive tract and to determine the microbiota in healthy volunteers from Brazil, collecting samples from the mouth, esophagus, stomach, duodenum, jejunum, ileum, colon, and rectum.

METHODS

Microbiota of selected healthy volunteers from the oral cavity (n=10), the esophagus (n=10), the upper digestive tract (n=20), and the lower digestive tract (n=24) were evaluated through distinct collection methods. Collection methods took into account the different sites, using basic scraping and swabbing techniques, stimulated saliva from the oral cavity, irrigation-aspiration with sterile catheters especially designed for the esophagus, a probe especially designed for upper digestive tract, and a special catheter for the lower digestive tract.

RESULTS

(i) Mixed microbiota were identified in the oral cavity, predominantly Gram-positive aerobic and anaerobic cocci; (ii) transitional flora mainly in the esophagus; (iii) Veillonella sp, Lactobacillus sp, and Clostridium sp in the stomach and duodenum; (iv) in the jejunum and upper ileum, we observed Bacteroides sp, Proteus sp, and Staphylococcus sp, in addition to Veillonella sp; (v) in the colon, the presence of "nonpathogenic" anaerobic bacteria Veillonella sp (average 10(5) UFC) indicates the existence of a low oxidation-reduction potential environment, which suggests the possibility of adoption of these bacteria as biological markers of total digestive tract health.

CONCLUSIONS

The collection methods were efficient in obtaining adequate samples from each segment of the total digestive tract to reveal the normal microbiota. These procedures are safe and easily reproducible for microbiological studies.

Is Helicobacter pylori really present in the adenoids of children?

Adenoid hyperplasia is a common cause of nasal obstruction in the pediatric age group. Recently, the adenoids were shown to harbor Helicobacter pylori (HP) based only on the rapid urease test (RUT). We conducted this pilot study to identify the presence of HP in the adenoids histologically and assess the reliability of both the RUT and histology in detecting HP in an extragastric location, using nested (two-steps) polymerase chain reaction (nPCR). Consecutive patients undergoing adenoidectomy for obstructive adenoid hyperplasia were enrolled. Adenoid specimens were subjected to the RUT. Histological sections stained with hematoxylin and eosin, Giemsa and Warthin-Starry were examined. We then used nPCR to detect the presence of HP in the studied specimens. Twenty-five patients (3-10 years; mean of 5.5 years) were enrolled. Twenty-one (84%) adenoids were positive by the RUT. Seventeen (68%) had bacteria on histological sections; four (16%) contained HP-like organisms. However, all specimens were negative by nPCR. No patient had a history of symptoms suggestive of laryngopharyngeal reflux within 6 months of the study. In conclusion, the children enrolled in this study did not have HP in their adenoids. High false positive results can occur with the RUT when used on adenoid tissues. It is not possible to rely solely on morphology to detect HP in an extragastric location. The nPCR remains the best way to identify HP accurately, but does not imply its presence in an active role.

Functional foods and paediatric gastro-intestinal health and disease

The application of molecular methods to gastro-intestinal diseases is giving insight into the way in which the resident intestinal microbiota interacts with the mucosal immune system. Using traditional culture techniques, the importance of mucosally-associated bacterial biofilms in maintaining mucosal integrity has been demonstrated in ways previously impossible. Changes in the balance of organisms at initiation of and during disease provide a rationale for interventions with functional foods which facilitate re-establishment of the homeostasis of healthy gut.

Non-Helicobacter bacterial flora rarely develops in the gastric mucosal layer of children

Non-Helicobacter bacteria can be cultured from the gastric mucosa in adults but in children, there are no studies about such microflora. The purpose of this study, therefore, was to clarify whether gastric biota develops in children. In 10 children and 10 adults or elderly (5 H. pylori-infected and 5 uninfected in each group), biopsy specimens of the gastric antrum and corpus and gastric juice were studied for bacterial examinations and the data were compared between both age groups in relation to H. pylori status and luminal pH. Bacterial genera and species were analyzed using both culture and real-time polymerase chain reaction (PCR) with the 52 genus- and species-specific primer sets. Non-Helicobacter bacteria in the mucosa were cultured from all adult patients, whereas microorganisms were cultured in only one child (p < .001). Gastric pH was lower in children (median, 1.4) than in adults (median, 2.6) (p < .005). The grade of endoscopic gastric atrophy was moderate or severe in 8 adults, but absent or mild in all 10 children. Among adults, there was a significant positive correlation between gastric pH and total bacterial counts of both the mucosa and juice. These data indicate that impaired gastric acid secretion associated with long-term H. pylori infection enables non-Helicobacter bacteria to colonize in the human stomach. Such microorganisms rarely colonize in the gastric mucosa in children regardless of H. pylori status.

The role of bacteria in chronic rhinosinusitis

Sinusitis generally develops as a complication of viral or allergic inflammation of the upper respiratory tract. The bacterial pathogens in acute sinusitis are S. pneumoniae, H. influenzae, and M. catarrhalis, while anaerobic bacteria and S. aureus predominant in CRS.

Chronic sinusitis in children and adults: role of bacteria and antimicrobial management

The nasopharynx serves as the reservoir for anaerobic bacteria as well as pathogenic bacteria that can cause respiratory infections including sinusitis. Some of these organisms possess the ability to interfere with the growth of potential pathogens and may play a role in preventing infections. Anaerobic bacteria emerge as pathogens as the infection becomes chronic. This may result from the selective pressure of antimicrobial agents that enable resistant anaerobic organisms to survive, and from the development of conditions appropriate for anaerobic growth, which include the reduction in oxygen tension and an increase in acidity within the sinus. Anaerobes were identified in chronic sinusitis in adults and children whenever techniques for their cultivation were employed. The predominant isolates were pigmented Prevotella, Fusobacterium, and Peptostreptococcus spp. The choice of antimicrobial agent in chronic sinusitis should provide coverage for the usual pathogens in acute sinusitis as well as beta-lactamase-producing aerobic and anaerobic organisms.

Recovery of interfering bacteria in the nasopharynx following antimicrobial therapy of acute maxillary sinusitis with telithromycin or amoxicillin-clavulanate

The effect on the nasopharyngeal flora of 7 days of amoxicillin-clavulanate or 5 days of 800 mg once a day was studied in 50 adults with acute sinusitis. The numbers of potential pathogens and interfering alpha-hemolytic streptococci were equally reduced after both therapies. However, the number of interfering Prevotella spp. declined more significantly after amoxicillin-clavulanate treatment.

The role of anaerobic bacteria in sinusitis

The normal oropharyngeal flora contained aerobic and anaerobic bacteria that can cause respiratory infections including sinusitis. Some of these bacteria can interfere with the growth of potential pathogens and may play a role in preventing infections. Anaerobic bacteria emerge as pathogens as the infection becomes chronic. This may be the result of the selective pressure of antimicrobial agents that enable resistant anaerobic organisms to survive, and from the development over time of conditions appropriate for anaerobic growth, which include the reduction in oxygen tension and an increase in acidity within the sinus cavity. Anaerobes were isolated in acute maxillary sinusitis of odontogenic origin and in over half of the patients with chronic sinusitis whenever proper techniques for their cultivation were employed. These organisms were also recovered in acute sinusitis that was associated with dental infections. The predominant isolates were pigmented Prevotella and Porphyromonas, Fusobacterium and Peptostreptococcus spp.

The role of bacterial interference in otitis, sinusitis and tonsillitis

Bacterial interactions that include antagonism (interference) and synergism help maintain balance between the members of the normal endogenous flora. Alpha-streptococci that predominate in the normal respiratory tract flora attracted most attention in studies of bacterial interference. Other organisms that possess interfering characteristics in upper respiratory tract infections (URTIs) are nonhemolytic streptococci, and Prevotella and Peptostreptococcus spp. The production of bacteriocins by some microorganisms is one of the important mechanisms of interference. The role of bacterial interference in the development of URTI and its effect on the eradication of these infections is discussed. These infections include pharyngo-tonsillitis, otitis media, and sinusitis. Treatment with various antimicrobial agents can affect the balance between members of the oro-pharyngeal bacterial flora and interfering organisms. Implantation into the indigenous microflora of low virulence bacterial strains that are potentially capable of interfering with colonization and infection with other more virulent organisms has been used in preliminary studies as a means of coping with the failure of antimicrobials in the treatment of several URTI.

Beneficial effect of auto-aggregating Lactobacillus crispatus on experimentally induced colitis in mice

We tested the therapeutic relevance of auto aggregation in lactobacilli by comparing the effect on DSS induced colitis of viable Lactobacillus crispatus M247, isolated from healthy humans, to L. crispatus MU5, an isogenic spontaneous mutants of M247, the latter lacking the auto aggregation phenotype which allows the adhesion to human mucus. Aggregating L. crispatus M247, but not the non-aggregating MU5, was retrievable from mice feces and adherent to the colonic mucosa. Daily administration of L. crispatus M247, but not heat killed L. crispatus M247 or aggregation deficient L. crispatus MU5, dose-dependently reduced the severity of DSS colitis. Indeed, L. crispatus MU5 administered in a 30% sucrose solution, known to restore the aggregation phenotype, had a protective effect comparable to mice receiving L. crispatus M247. These results indicate that a surface-mediated property such as aggregation may play a pivotal role in the protective effects obtained by dietary supplementation with L. crispatus M247 during colitis.

Long-term effects on the nasopharyngeal flora of children following antimicrobial therapy of acute otitis media with cefdinir or amoxycillin-clavulanate

The effect on the nasopharyngeal bacterial flora of 10 days of amoxycillin-clavulanate or cefdinir antimicrobial therapy was studied in 50 children with acute otitis media. Before therapy, 17 potential pathogens (Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis) were isolated from the nasopharynx of 14 (56%) of those treated with amoxycillin-clavulanate, and 20 potential pathogens were recovered from 15 (60%) of those treated with cefdinir. Following therapy, at days 12-15, the number of potential pathogens was reduced to a similar extent with both therapies, to three in those treated with amoxycillin-clavulanate and two in those treated with cefdinir. However, the number of potential pathogens rebounded faster in those treated with amoxycillin-clavulanate as compared with cefdinir in the two subsequent specimens taken at days 30-35 and 60-65 (12 and 18 in the amoxycillin-clavulanate group, and six and nine in the cefdinir group, P < 0.01 and P < 0.001, respectively). Differences between the groups were also noted in the recovery of organisms with interfering capability. Immediately following amoxycillin-clavulanate therapy, the number of interfering organisms declined from 54 to 13, while following cefdinir treatment their number was reduced from 59 to 39 (P < 0.001). The differences between the two therapy groups persisted in the two later specimens taken at days 30-35 and 60-65 (25 and 38 in the amoxycillin-clavulanate group, and 52 and 51 in the cefdinir group, P < 0.001 and P < 0.05, respectively). This study illustrates the potential beneficial effect of using a narrow-spectrum antimicrobial that selectively spares the interfering organisms while eliminating pathogens. The benefit of such therapy is the prevention of reacquisition of pathogenic bacteria in the nasopharynx. In contrast, utilization of a broad-spectrum antimicrobial is associated with prolonged absence of inhibitory organisms and rapid recolonization with pathogens.

Burden of Infection in Patients with End-Stage Renal Disease Requiring Long-Term Dialysis

BACKGROUND

This study examines the spectrum of infections in a selected population of patients requiring long-term dialysis, enlarging the focus beyond infections associated with the dialysis process.

METHODS

Infection data were reviewed from complete archived inpatient and outpatient dialysis records of 433 patients who were treated at a single hospital-based dialysis program and its dialysis satellites over a 9-year period, from 1 January 1992 to 31 December 2000.

RESULTS

The study period included 424,700 days of dialysis experience. A total of 2412 episodes of bacterial or fungal infections were treated in 433 patients. The infection rate was 5.7 episodes per 1000 days of dialysis. Patients received 5111 courses of antibiotics over 42,627 days of treatment, which cumulatively accounted for 10% of the total days of the study. Infections associated with hemodialysis vascular access devices comprised 20.5% of the total episodes. Infections below the knee (19.3% of infection episodes), pneumonia (13%), and other skin and soft-tissue infections (9%) were also important types and sources of infection, accounting for >42% of the total episodes. Eighty-two percent of the infections (1971 episodes) were acquired in the community. Of these, 868 (44%) required hospitalization. An additional 441 episodes were nosocomial. The profile of bacteria isolated from patients with community-acquired infections mirrored that of bacteria recovered from patients with nosocomial infections.

CONCLUSION

Patients with end-stage renal disease have an enormous burden of infection. The majority of the infections are unrelated to dialysis. Frequent and long-term antibiotic use and cohorting of patients in the dialysis unit have altered the microbiological flora of such individuals, with clinical and epidemiological implications.

Effect of antimicrobial therapy with amoxicillin and cefprozil on bacterial interference and beta-lactamase production in the adenoids

To compare the effects on the bacterial flora of the adenoids of antimicrobial therapy with amoxicillin or cefprozil, we enrolled in a prospective randomized study 60 children scheduled for elective adenoidectomy because of recurrent otitis media. They were randomized before surgery into 3 groups of 20 patients each: a no-therapy group, and groups with 10 days of either amoxicillin or cefprozil therapy. Core adenoid materials were quantitatively cultured for aerobic and facultative bacteria. The in vitro ability of alpha-hemolytic streptococci (AHS) to inhibit the growth of non-type B Haemophilus influenzae and Streptococcus pneumoniae was determined. The number of organisms in adenoids obtained from patients treated with either antibiotic was reduced as compared to that in adenoids from controls. However, in patients treated with amoxicillin, a significant decline in the number of AHS, and an increase (in Staphylococcus aureus) or no change in the number of other beta-lactamase-producing bacteria (BLPB) was noted. In contrast, in those treated with cefprozil, no change was noted in the frequency of recovery of AHS, and the number of BLPB decreased. Interfering AHS were more often recovered in patients treated with cefprozil. We conclude that the adenoids contain more interfering AHS after therapy with a second-generation oral cephalosporin (cefprozil) than after amoxicillin therapy. This study suggests a potential beneficial effect of using an antimicrobial that selectively spares interfering AHS while inhibiting BLPB.

Type 1 diabetes mellitus in childhood: a matched case control study in Lancashire and Cumbria, UK

AIMS

The aim of the study was to identify environmental risk factors for insulin-dependent diabetes mellitus (Type 1 DM) in childhood.

METHODS

A matched case-control study of Type 1 DM conducted in Lancashire and Cumbria, UK, using a structured interview. Cases (n=196, participation rate 83%) were children under 16 years of age diagnosed prior to October 1998 and attending diabetic clinics. Controls (n=381) were healthy children from the community matched by gender and by age (within a few days of birth). The data were analysed by logistic regression using the technique of Breslow and Day for matched case control studies.

RESULTS

The multivariate regression model showed that the following factors were significantly associated with the risk of developing Type 1 DM (odds ratio, 95% confidence intervals): sharing a room with a sibling (0.458, 0.290-0.721), social contact with other children when aged 6-11 months (0.439, 0.256-0.752), consumption of sugary food (0.080, 0.024-0.261), parental insulin dependent diabetes mellitus (10.651, 3.086-36.761), maternal thyroid disease (4.861, 1.681-14.058), consuming more than one pint of milk per day prior to school entry (0.498, 0.310-0.802), maternal smoking during pregnancy (0.373, 0.218-0.636), a father with no academic qualifications (0.504, 0.278-0.913), maternal age at time of birth (0.900, 0.854-0.948), maternal infections in pregnancy (2.453, 1.011-5.948), other maternal illnesses or conditions in pregnancy (2.007, 1.139-3.535), belonging to an Asian family (0.104, 0.028-0.394), and regular contact with pets and other animals (0.552, 0.309-0.987).

CONCLUSION

Many of the results are consistent with the hygiene hypothesis which links improved living standards with decreased exposure to microorganisms and increased risk of immune mediated disease in childhood. These findings challenge the idea that improved hygiene acts exclusively through a Th2 mechanism leading to atopic disease as Type 1 DM is mediated by a Th1 reaction. The association with maternal smoking could be due to recall bias but a causal link cannot be excluded with confidence.

Pouchitis

Pouchitis is one of the commonest and most debilitating complications of a restorative proctocolectomy. The cause remains elusive, though a number of approaches have been shown to alleviate the condition. This review outlines current evidence relating to pouchitis, obtained from randomised and nonrandomised studies. Medline, the Bath Information Data Service (BIDS) and PubMed were searched using the keywords 'pouchitis' and 'inflammatory bowel disease'. In addition, articles were cross-referenced, and the abstracts of recent colorectal meetings studied.

Microbial dynamics of purulent nasopharyngitis in children

This review presents the microbiological dynamic and therapeutic options in the management of purulent nasopharyngitis (NPT). The nasopharynx (NP) of healthy children is generally colonized by relatively non-pathogenic aerobic and anaerobic organisms, some of, which possess the ability to interfere with the growth of potential pathogens. Conversely, carriage of potential respiratory aerobic pathogen such as Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis, as well as some anaerobic bacteria (Peptostreptococcus, Fusobacterium and Prevotella spp.) increases during purulent NPT. The development of purulent NPT in children is associated with the pre-existing colonization by potential pathogens and the absence of interfering organisms in the NP. Controversy exists regarding the management of NPT as no conclusive evidence exists to date that the administration of antimicrobials will shorten the illness.

Characterization of the bacterial population of the genital tract of adult cats

OBJECTIVE

To characterize the bacteria of the genital tract in adult cats; assess the effect of estrus, mating, and administration of progestins on those microorganisms in females; and evaluate whether results of bacteriologic culture of vaginal swabs are affected by cleansing of the vulva prior to sampling or by repeated sampling.

ANIMALS

66 female and 29 male cats undergoing routine ovariohysterectomy or castration.

PROCEDURE

Specimens were obtained from vaginal and uterine or preputial mucosae with swabs moistened with sterile saline (0.9% NaCl) solution. In 9 cats, vaginal specimens were obtained before and after cleansing of the vulva with ethanol; in 7 female cats, 2 vaginal speci mens were obtained in immediate succession.

RESULTS

Aerobic bacteria were most commonly isolated from cats' vaginas and prepuces; anaerobic bacteria were isolated frequently from males (41%) but rarely from females (5%). Generally, culture results were not affected by cleansing of the vulva or repeated vaginal sampling. The bacterial population of the vaginas of cats was influenced by stage of the estrous cycle but not by mating or administration of progestins. Bacteria were not isolated from the uterus of any cat.

CONCLUSIONS AND CLINICAL RELEVANCE

In cats, bacteria of the genital tract in females are predominantly aerobic; in males, aerobic and anaerobic bacteria are found. The bacterial population of the vagina is affected by stage of the estrous cycle. Pure growth of bacteria in culture of genital tract specimens is a normal finding; antimicrobials should only be administered if clinical signs of genital infection are present.

The role of the gut flora in health and disease, and its modification as therapy

The gut flora is a vast interior ecosystem whose nature is only beginning to be unravelled, due to the emergence of sophisticated molecular tools. Techniques such as 16S ribosomal RNA analysis, polymerase chain reaction amplification and the use of DNA microarrays now facilitate rapid identification and characterization of species resistant to conventional culture and possibly unknown species. Life-long cross-talk between the host and the gut flora determines whether health is maintained or disease intervenes. An understanding of these bacteria-bacteria and bacteria-host immune and epithelial cell interactions is likely to lead to a greater insight into disease pathogenesis. Studies of single organism-epithelial interactions have revealed the large range of metabolic processes that gut bacteria may influence. In inflammatory bowel diseases, bacteria drive the inflammatory process, and genetic predisposition to disease identified to date, such as the recently described NOD2/CARD15 gene variants, may relate to altered bacterial recognition. Extra-intestinal disorders, such as atopy and arthritis, may also have an altered gut milieu as their basis. Clinical evidence is emerging that the modification of this internal environment, using either antibiotics or probiotic bacteria, is beneficial in preventing and treating disease. This natural and apparently safe approach holds great appeal.

Suppression of antigen-specific lymphocyte proliferation by Gram-positive bacterial cell walls

It is largely unknown how bacterial cell walls (BCW) modulate human immune responses. In the present work the effect of Gram-positive BCW on lymphocyte proliferation responses towards several microbial antigens (Ag) or mitogens was studied. Gram-positive BCW were derived from four indigenous bacterial strains and from one pathogen (Streptococcus pyogenes). All BCW preparations used non-specifically suppressed the proliferation responses of peripheral blood mononuclear cells (PBMC) against bacterial and viral Ag, but not against mitogens. Both lymphocytes and macrophages or their secreted products mediated the suppressive effects of BCW, which were not IL-10 dependent. Furthermore, the expression of HLA-DR and CD86 on monocytes/macrophages was downregulated by BCW. Unlike in LPS-induced suppression, the CD14 pathway was not used by BCW of Lactobacillus casei (L.c.). The observed results indicate that Gram-positive BCW suppress antigen-specific lymphocyte proliferation through several mechanisms. This non-specific immunosuppression might be a general function of BCW in the bacteria-host interaction, being of importance for bacterial survival and pathogenicity.

Nasopharyngeal carriage of Streptococcus pneumoniae in healthy children: implications for the use of heptavalent pneumococcal conjugate vaccine

We assessed the prevalence of Streptococcus pneumoniae serotypes in the nasopharynx of healthy children, antimicrobial susceptibility patterns, risk factors for carriage, and the coverage of heptavalent pneumococcal conjugate vaccine. In 2,799 healthy infants and children, the S. pneumoniae carrier rate was 8.6% (serotypes 3, 19F, 23F, 19A, 6B, and 14 were most common). Most pneumococci (69.4%) were resistant to one or more antimicrobial classes. The rate of penicillin resistance was low (9.1%); macrolide resistance was high (52.1%). Overall, 63.2% of the isolates belonged to strains covered by the heptavalent pneumococcal vaccine. This percentage was higher in children <2 years old (73.1%) and in those ages 2-5 years (68.9%). Sinusitis in the previous 3 months was the only risk factor for carrier status; acute otitis media was the only risk factor for the carriage of penicillin-resistant S. pneumoniae. Most isolated strains are covered by the heptavalent conjugate vaccine, especially in the first years of life, suggesting that its use could reduce the incidence of pneumococcal disease.

Colonization rate of bacteria in the throat of healthy infants

OBJECTIVE

the human throat is a major ecological site for various bacteria that can reach neighbouring sterile sites and cause mild infections or invasive diseases. The aim of this study was to investigate the carriage rate of several potential pathogens in the throat of healthy children under the age of 2 years.

METHODS

cultures were taken from the tonsils of 1000 healthy infants aged 1-24 months attending well-baby clinics, who had not received antibiotic therapy during the preceding 14 days.

RESULTS

one hundred and ninety-eight (19.8%) cultures were positive. Thirteen (1.3%) cultures were positive for beta-haemolytic Streptococcus group A, 23 (2.3%) for Streptococcus pneumoniae. In 28 (2.8%) and 24 (2.4%) cultures, respectively, Haemophilus influenzae Type b and non-typeable Haemophilus influenzae were recovered. The commonest bacterium found was Staphylococcus aureus (99 positive cultures). Eleven children carried two species of bacteria and from one 6-month-old child three species were isolated concurrently.

CONCLUSIONS

it is concluded that children younger than 2 years of age can be carriers of several types of pathogenic bacteria. In contrast to many other studies, in this study beta-haemolytic Streptococcus group A was isolated from the tonsils of children younger than 1 year of age.

The bacterial flora in inflammatory bowel disease: current insights in pathogenesis and the influence of antibiotics and probiotics

The pathogenesis of inflammatory bowel disease (IBD) remains unknown, although in recent years more data have become available. The contribution of genetic and environmental factors is evident, and the luminal bacterial flora plays a major role in the initiation and perpetuation of chronic IBD. Animal models of IBD have shown that colitis does not occur in a germ-free environment. In human IBD, inflammation is present in parts of the gut containing the highest bacterial concentrations. Moreover, the terminal ileum, caecum and rectum are areas of relative stasis, providing prolonged mucosal contact with luminal contents. Enhanced mucosal permeability may play a pivotal role in maintaining a chronic inflammatory state, due to a genetic predisposition or as a result of direct contact with bacteria or their products. A detective epithelial barrier may cause a loss of tolerance to the normal enteric flora. Furthermore, an increased mucosal absorption of viable bacteria and bacterial products is found in IBD. Serum and secreted antibodies are increased and mucosal T-lymphocytes that recognize luminal bacteria are present. However, there is evidence that the immune system reacts over aggressively towards the normal luminal flora rather than the flora being altered in IBD. Several approaches have been used in attempts to discover a specific microbial agent in the cause of IBD. These include demonstration of the presence of organisms or specific antigens in affected tissues, culture of microbes firm the affected tissues, demonstration of serological responses to several agents, and localization and detection of individual pathogen-specific nucleic acid sequences in affected tissue by in situ hybridization and polymerase chain reaction. So far, no specific micro-organism has been directly associated with the pathogenesis of IBD. Analysis of the luminal enteric flora, however, has revealed differences in the composition of this flora compared to healthy controls. In Crohn disease, concentrations of Bacteroides, Eubacteria and Peptostreptococcus are increased, whereas Bifidobacteria numbers are significantly reduced. Furthermore, in ulcerative colitis, concentrations of facultative anaerobic bacteria are increased. The arrival of new molecular techniques qualifying and quantifying the complex intestinal flora has induced a revival of interest in this microflora. Therapeutic approaches geared towards changing the environment at the mucosal border have been attempted by the use of elemental diets, total parenteral nutrition, surgical diversion of the faecal stream and antibiotics. Over the past few years, the use of probiotics in IBD and other intestinal disorders has gained attention. Strengthened by promising experimental data and commercial interests, research in this field is rapidly expanding. Manipulation of the colonic bacteria with antibiotic drugs and probiotic agents may prove to be more effective and better tolerated than immunosuppressants in the future.

Stool colonization with vancomycin-resistant enterococci in healthcare workers and their households

OBJECTIVE

To determine the prevalence of stool colonization with vancomycin-resistant enterococci (VRE) among healthcare workers (HCWs) and their families.

DESIGN

Prospective assessment of fecal colonization with VRE.

SETTING

A 603-bed, tertiary-care teaching hospital.

PARTICIPANTS

Healthy volunteers recruited from hospital employees and their households were screened to exclude pregnancy, diabetes mellitus, immunosuppressive disorders, and recent use of antimicrobials.

INTERVENTION

Self-obtained stool swabs were used to obtain cultures. Isolated enterococci were screened for vancomycin resistance and species were identified. Intra-household isolates were genotyped using pulsed-field gel electrophoresis (PFGE).

RESULTS

The participants (n = 228; age range, 28 days to 80 years) were from 137 households with and 91 without employees who had contact with patients. Enterococcus species were isolated from 127 stool specimens (55.7%). VRE were detected in 12 individuals, representing 6 E. casseliflavus, 5 E. faecium, and 1 E. gallinarum. VRE were more commonly isolated in employees who had contact with patients (5 of 52 vs 0 of 40; relative risk [RR], 1.9; 95% confidence interval [CI95], 1.5 to 2.2; P = .07) and their household members (10 of 137 vs 2 of 91; RR, 3.3; CI95, 0.7 to 14.8; P = .13). In 2 households (2 adults in a physician's household and an adult plus a child in a nurse's household) PFGE analysis demonstrated identical intra-household strains of vancomycin-resistant E. faecium.

CONCLUSIONS

VRE colonization was found in 5.3% of screened stools and was more prevalent in HCWs who had contact with patients and their households. Identical PFGE patterns between 2 employees who had contact with patients and their household members demonstrated probable intra-household spread. Although the mode of acquisition was uncertain, the association with employees who had contact with patients suggests possible occupational sources. These findings demonstrate the spread of VRE within the household and implicate occupational risk for its acquisition.

Antibiotics

This chapter discusses the bacterial pathogens that cause infective exacerbations, trials of antimicrobial therapy, individual antimicrobial agents, and guidelines for their use in the treatment of both asthma and chronic obstructive pulmonary disease (COPD). The relationship between respiratory tract infection, especially viral infection, and exacerbations of airway diseases is very well established. However, research is required to find new ways to distinguish between the colonization and infective exacerbations of COPD to gain a better understanding of the role of infection in the disease. With advances in molecular biology, the antigenic structures of bacteria and the evaluation of the antibody response to antigens can become the basis for identifying an acute exacerbation of COPD (AECB). Most clinical trials of antibiotics were performed for licensing, and patients with pathogens resistant to different antimicrobials were excluded. Future studies of new antimicrobials should examine clinical efficacy more stringently based on a classification system that would help select patients most likely to benefit from an antibiotic. These studies should also include well-defined prospective economic analyses and quality-of-life assessment to ascertain the cost utility of the antibiotic in question.

Host defense in respiratory infections

Respiratory defenses against infection involve a diverse and complex system. Mechanical barriers limit exposure of the respiratory tract to potential pathogenic organisms, whereas the mucociliary apparatus and cough reflexes work to expel any microbes that may bypass the initial defenses. When microorganisms have gained entry to the lower respiratory tract, the alveolar macrophage and recruited phagocytes may eliminate the culprits before active infection can be established. Only after the failure of the innate immune defenses is a specific immune response mounted. Examination of clinical defects in host defense allows one to understand the importance of the multitude of components of the lung's immune defense system.

Faecal fungal flora in healthy volunteers and inpatients

The faecal fungal flora was analysed in healthy volunteers and inpatients. Self-obtained stool swabs from volunteers (n = 228) and inpatient stool-samples (n = 34) were cultured on Inhibitory-Mould-Agar plates. All yeast isolates were identified. Fungi were detected in 51.8% of volunteers; the majority (88.1%) had single species. The prevalence increased steadily with age. Candida albicans was detected in 62.7%, non-albicans Candida species in 22.0%, yeasts--other than Candida in 20.3% and moulds in 8.5% of volunteers with fungi. No gender-related differences were noted in the prevalence or types of yeast. Candida glabrata and C. krusei were detected in adults only. Intra-household species-similarity (excluding C. albicans) was noted in seven of 31 (22.6%) households with fungi in two or more members. Inpatients had higher prevalence of yeast (88.2%) with a single species in the majority (73.3%). Yeasts other than Candida were less common in inpatients (3.3%; P = 0.013) whereas C. glabrata was significantly more prevalent (33.3 versus 2.5%; P < 0.001). This study delineates the faecal fungal flora in volunteers and inpatients. Most subjects harbour a single species that may be shared with other households. The prevalence is somewhat higher in adults and the types of yeast may vary with age. Finally, C. glabrata appears to be acquired nosocomially.

Management of portal hypertension after variceal hemorrhage

Each variceal bleed is associated with 20% to 30% risk of dying. Management of portal hypertension after a bleed consists of (1) control of bleeding and (2) prevention of rebleeding. Effective control of bleeding can be achieved either pharmacologically by administering somatostatin or octreotide or endoscopically via sclerotherapy or variceal band ligation. In practice, both pharmacologic and endoscopic therapy are used concomitantly. Rebleeding can be prevented by endoscopic obliteration of varices. In this setting, variceal ligation is the preferred endoscopic modality. B-blockade is as effective as endoscopic therapy and, in combination, the two modalities may be additive.

Bacterial resistance in urinary tract infections: how to stem the tide

Each year, approximately 10% of the population is diagnosed with a urinary tract infection (UTI). Escherichia coli is the most prevalent pathogen in UTIs but other species make significant contributions. UTIs are commonly treated with antibiotics and, therefore, a potential source for the emergence and/or selection of resistant bacteria. Although susceptibility to some antibiotics for a number of species is still high, resistance is an issue both for community- and hospital-acquired UTI. However, often treatment is empiric, especially in the community setting. This empiric treatment is often guided by inadequate information about the (local) rates of resistance, selection and emergence of resistance, although there is a general consensus that there is a relationship between antibiotic use and resistance. It is well known that some antibiotics, e.g., some fluoroquinolones, are able to induce mutations leading to resistance but the antibiotics prescribed also affect the commensal flora, potentially selecting resistant organisms. However, antibiotics meant to treat other infections may select uropathogens and, thereby, the risk for UTIs increases. The duration of treatment of any infection is an important factor to consider in this respect, as well as subinhibitory concentrations of the antibiotic prescribed. Prudent use of new and still effective antibiotics is required. Although prudent use of these antibiotics may help to reduce the prevalence of antibiotic-resistant uropathogens, elimination will be hard to achieve. Therefore, we believe, that we can reduce the tide but we will still have to deal with the resistance problem in the future.

Effect of mouth washing on the

BACKGROUND

Mouth washing is often mentioned as a possible method to eliminate the interference of urease activity in the oral cavity before the [13C]-urea breath test (UBT). However, the effectiveness of mouth washing prior to testing has not been demonstrated clearly in the literature. Thus, the present study was designed to examine the consistency of the [13C]-UBT and the effects of mouth washing on it.

METHODS

A total of 101 healthy volunteers underwent the [13C]-UBT three times. The first and second tests used a standard protocol and collected samples at 5, 10, 15 and 30 min. In the third test, the procedure was the same except that mouth washing was omitted.

RESULTS

We used 5 permil (/1000) as the cut-off value and there were 21 (20.8%) positive cases. The kappa values for the samples collected at 5, 10, 15 and 30 min between the first and second tests were 0.68, 0.97, 1 and 1, respectively, and all showed good consistency, except for the sample collected at 5 min. Judging from the mean value of the [13C] enrichment of the first and second tests (with mouth washing) and the third test (without mouth washing), 50 (63.3%), 15 (18.8%), 0 and 0 cases at 5, 10, 15 and 30 min, respectively, changed from negative to positive. There were 14 (17.5%) and six (7.5%) cases at 15 and 30 min, respectively, whose [13C] enrichment changed from less than 3 (negative) to between 3 and 5 (border zone).

CONCLUSIONS

These results indicate that mouth washing had an important effect on samples obtained at 5 and 10 min, while this influence decreased at 15 min and was lowest at 30 min.

Comparison of the effects of hospitalization and antibiotic usage on the aerobic intestinal flora

Antimicrobial resistance among bacteria has arisen ever since antimicrobial agents were introduced in the clinic. Unfortunately, it seems that resistance is now emerging at a more rapid rate than ever before, as a consequence of the widespread use of antimicrobial agents. The spread of these multiresistant microorganisms is an increasing threat in many countries. The human intestinal flora is a huge potential reservoir of resistant microorganisms. Antimicrobial resistance in clinical isolates may cause serious infections and treatment failure, and lead to the use of higher doses or more toxic alternative drugs. This study was planned so as to compare the effects of hospitalization and antibiotic usage on the aerobic intestinal flora and included 43 hospitalized adult patients without any previous history of hospitalization and antibiotic usage during the last 30 d. Patients were divided according to their antimicrobial therapy, into treated and untreated groups. The individual use of antimicrobials was recorded. Antibiotic usage was found to be more effective on the aerobic intestinal flora compared with hospitalization without such medication.

Stimulation of adenoidal lymphocytes by Alloiococcus otitidis

Otitis media with effusion (OME) is characterized by persistent effusion in the middle ear cavity and by chronic inflammation in the middle ear mucosa. Alloiococcus otitidis, a gram-positive aerobic bacterium, has been isolated in middle ear effusion, and by means of sensitive polymerase chain reaction detection assays it has been detected in as many as 20% of middle ear aspirates of patients with OME. Because A otitidis may freely interact with leukocytes in the middle ear effusion, it may potentially modulate the inflammatory reaction in OME. To study the nature of these interactions, we applied an in vitro assay in which killed A otitidis bacteria were incubated with peripheral blood and adenoidal mononuclear cells. The expression of the proliferation-associated surface marker CD69 was then measured in B lymphocytes and in CD4+ helper and CD8+ cytotoxic-suppressor T lymphocytes by means of multicolor flow cytometry. Alloiococcus otitidis induced the expression of CD69 in both peripheral blood and adenoidal T and B cells. Among the T cells, the cytotoxic-suppressor T lymphocytes were preferentially activated. It was also tested whether A otitidis would have an effect in another cytotoxic and immunoregulatory system, namely, the induction of natural killer cell activity in peripheral blood mononuclear cells. However, the effect was minimal compared with that of Salmonella minnesota or Staphylococcus aureus. The results show that A otitidis has a unique immunostimulatory capacity in vitro that is mainly confined to CD8+ T lymphocytes.

Saccharomyces boulardii stimulates sIgA production and the phagocytic system of gnotobiotic mice

The effect of Saccharomyces boulardii on the immune system was evaluated, comparing germ-free Swiss/NIH mice monoassociated with the probiotic with germ-free mice. Saccharomyces boulardii colonized the gut of germ-free mice and survived the gastrointestinal conditions. An increase in sIgA production, both total and anti-S. boulardii, was observed in the intestinal contents of monoassociated mice when compared with germ-free controls. The number of Kupffer cells was significantly higher in monoassociated mice than in germ-free controls. In S. boulardii-monoassociated mice, clearance of Escherichia coli B41 was higher than in germ-free controls. TNF-alpha, IFN-gamma and IL-12 serum levels were higher at earlier time points in monoassociated mice when compared with germ-free mice. These results show that the yeast S. boulardii modulates the host immune responses. This effect may be of interest for improving the resistance to enteropathogenic bacterial infections.

Oral bacteriotherapy as maintenance treatment in patients with chronic pouchitis: a double-blind, placebo-controlled trial

BACKGROUND & AIMS

Pouchitis is the major long-term complication after ileal pouch-anal anastomosis for ulcerative colitis. Most patients have relapsing disease, and no maintenance treatment study has been performed. We evaluated the efficacy of a probiotic preparation (VSL#3) containing 5 x 10(11) per gram of viable lyophilized bacteria of 4 strains of lactobacilli, 3 strains of bifidobacteria, and 1 strain of Streptococcus salivarius subsp. thermophilus compared with placebo in maintenance of remission of chronic pouchitis.

METHODS

Forty patients in clinical and endoscopic remission were randomized to receive either VSL#3, 6 g/day, or an identical placebo for 9 months. Patients were assessed clinically every month and endoscopically and histologically every 2 months or in the case of a relapse. Fecal samples were collected for stool culture before and after antibiotic treatment and each month during maintenance treatment.

RESULTS

Three patients (15%) in the VSL#3 group had relapses within the 9-month follow-up period, compared with 20 (100%) in the placebo group (P < 0.001). Fecal concentration of lactobacilli, bifidobacteria, and S. thermophilus increased significantly from baseline levels only in the VSL#3-treated group (P < 0.01).

CONCLUSIONS

These results suggest that oral administration of this new probiotic preparation is effective in preventing flare-ups of chronic pouchitis.

Replace hand washing with use of a waterless alcohol hand rub?

Hand hygiene is one of the basic components of any infection control program and is frequently considered synonymous with hand washing. However, health care workers frequently do not wash their hands, and compliance rarely exceeds 40%. Hand rubbing with a waterless, alcohol-based rub-in cleanser is commonly used in many European countries instead of hand washing. Scientific evidence and ease of use support employment of a hand rub for routine hand hygiene. It is microbiologically more effective in vitro and in vivo, it saves time, and preliminary data demonstrate better compliance than with hand washing. Therefore, a task force comprising experts from the Centers for Disease Control and Prevention and from professional societies is designing guidelines for the use of a hand rub in the United States. Today, most countries of Northern Europe recommend a hand rub for hand hygiene unless the hands are visibly soiled. Side effects are rare and are mainly related to dryness of the skin. This review evaluates the scientific and clinical evidence that support the use of alcohol-based hand rubs in health care facilities as a new option for hand hygiene.

Probiotics and inflammatory bowel disease: is there a scientific rationale?

Most conventional forms of drug therapy suppress or modify the host immunoinflammatory response and neglect the other contributor to disease pathogenesis-the environmental microflora. Probiotics are live microbial food ingredients that alter the enteric microflora and have a beneficial effect on health. The rationale for using probiotics in IBD is mainly based on evidence from human studies and experimental animal models implicating intestinal bacteria in the pathogenesis of these disorders. The relationship between bacteria and intestinal inflammation is complex and does not appear to reflect a simple cause and effect. Similarly, the field of probiotics is complex and in need of rigorous research. Until the indigenous flora are better characterized and mechanisms of probiotic action defined, the promise of probiotics in IBD is unlikely to be fulfilled. Because of strain-specific variability and clinical and therapeutic heterogeneity within Crohn's disease and ulcerative colitis, it cannot be assumed that a given probiotic is equally suitable for all individuals. Although preliminary results of probiotic therapy in animal models and humans with ulcerative colitis and pouchitis have been encouraging, their efficacy in treatment or maintenance of remission of Crohn's disease remains to be clarified. However, the circumstantial evidence for some form of biotherapeutic modification of the enteric flora in Crohn's disease seems compelling. In the future, probiotics may offer a simple adjunct to conventional therapy with the emphasis on diet shifting from one of nutritional replenishment alone to a more functional role.

Probiotics in infective diarrhoea and inflammatory bowel diseases

Bacteria are present throughout the gastrointestinal tract, but their pattern and concentration vary greatly. Probiotics are living organisms that supply beneficial health effects to the host. So far the beneficial effects of probiotics have been shown, almost exclusively, under poorly defined experimental conditions. There are little convincing data from well-designed, double-blind controlled trials supporting health-promoting effects. The use of probiotics to treat gastrointestinal infections has produced contrasting results. Apart from information on rotavirus infection in children, there is no convincing evidence from controlled studies on the efficacy of probiotics in the prevention or treatment of infective diarrhoea. However, experimental and clinical studies suggest that there are potential therapeutic roles for probiotics in the treatment of inflammatory bowel diseases. This review focuses on the available data concerning the mechanisms of action of probiotics, and on the results from clinical studies using probiotics to treat infective diarrhoea and inflammatory bowel disease.

Dynamics of nasopharyngitis in children

PURPOSE

Our goal was to characterize the dynamics and bacterial interaction of the aerobic and anaerobic flora of nasal discharge of children at different stages of uncomplicated nasopharyngitis.

METHODS AND PATIENTS

Serial semiquantitative nasopharyngeal (NP) and quantitative nasal discharge (ND) cultures were taken every 3 to 5 days from 20 children in whom purulent discharge eventually developed (group 1), and a single culture was obtained from a group of 20 who had only clear discharge (group 2).

RESULTS

Aerobic and anaerobic bacteria were isolated from all NP cultures. Bacterial growth was present in 8 (40%) NDs of group 2. Only 7 (35%) of the clear NDs of group 1 showed bacterial growth; the number increased to 14 (70%) at the mucoid stage and 20 (100%) at the purulent stage. It declined to 6 (30%) at the final clear stage. The number of species and total number of organisms increased in the NDs of group 1. Group 1 patients had higher recovery rates of Streptococcus pneumoniae and Haemophilus influenzae in their NP cultures than group 2 patients (P < 0.05). During the purulent stage, Peptostreptococcus species were isolated in 15 (75%), Fusobacterium species in 10 (50%), Prevotella species in 9 (45%), H influenzae in 8 (40%), S pneumoniae in 6 (30%), and beta-hemolytic streptococci in 5 (25%) of group 1 NDs. This was higher than their recovery in the clear stages of both groups and the mucoid stage of group 1. A total of 8 organisms capable of interfering with the growth of potential pathogens were isolated from the NPs of group 1, as compared with 35 from group 2 (P < 0.001).

CONCLUSIONS

The development of purulent nasopharyngitis is associated with the pre-existing presence of potential pathogens and the absence of interfering organisms.

Bacterial flora accompanying Candida yeasts in clinical specimens

From 1986 to 1988, in the prefluconazole era, 67,765 clinical specimens from the Göttingen University Hospital were investigated for bacteria and fungi in our institution. Oral and throat swabs, respiratory secretions, gastric juices, faeces, urine, genital swabs, blood, wound secretions and skin swabs were analysed for yeast-like fungi, and opportunistic or pathogenic bacteria. A total of 5195 specimens (7.7%) yielded Candida spp. alone or in combination with bacteria (fungal (F-) group) and 62,570 specimens yielded bacteria only or remained sterile (non-fungal group, N-group). Elevated rates of accompanying bacteria were detected with Candida spp. colonizing blood, urine, and skin. Among the dominant bacterial isolates, the distribution of staphylococci and enterococci did not reflect a distinct association pattern. Among the enterobacterial isolates from patients in intensive care, colonization patterns of the throat, gastric juices, and faeces reflected the use of a selective decontamination of the digestive tract (SDD). A statistically significant association between Candida and enterobacteria of the genus Enterobacter which was unaffected by SDD, was observed throughout this study. Such an association pattern was also observed, to a lesser extent, with the related genera Klebsiella and Serratia, but not with Escherichia coli.

Bacterial interference in the nasopharynx and nasal cavity of sinusitis prone and non-sinusitis prone children

The aim of this study was to compare the frequency of recovery of potential pathogens and aerobic and anaerobic interfering bacteria in the nasopharynx and nasal cavity of sinusitis prone (SP) children, with their recovery in non-sinusitis prone (N-SP) children. Nasopharyngeal and nasal cultures were taken from 20 SP and 20 N-SP children. Potential pathogens and aerobic and anaerobic bacteria with interfering capabilities against these micro-organisms were identified. Twenty-one potential pathogens (1.05 patient) were isolated from nasopharyngeal cultures from 14 of the 20 SP children, and 10 (0.5 patient) were recovered from 6 of the 20 NSP (p < 0.05). Bacterial interference between two aerobic (alpha and non-haemolytic streptococci) and two anaerobic species (Prevotella and Peptostreptococcus species) and four potential pathogens was observed. Bacterial interference was noted in 64 instances against 4 potential pathogens by 24 normal flora isolates that were recovered from 7 of the SP group and in 144 instances by 47 isolates from 18 of the NSP group (p < 0.05). Nineteen potential pathogens (0.95/patient) were isolated from nasal cultures of 13 of the 20 SP children and 8 (0.4/patient) were recovered from 5 of the 20 NSP (p < 0.05). Bacterial interference by similar micro-organisms was noted in 21 instances by 9 normal flora isolates that were recovered from 5 of the SP group, and in 63 instances by 26 isolates from 15 of the NSP group (p < 0.05). Our findings illustrate for the first time that the nasopharyngeal and nasal flora of NSP children contains more aerobic and anaerobic micro-organisms with interfering capability and less potential pathogens than that of SP children.