Effect of decreased salivation and pH on the adherence of Klebsiella species to human buccal epithelial cells

The potential of EGCG in modulating the oral-gut axis microbiota for treating inflammatory bowel disease

Inflammatory bowel disease (IBD) is a recurrent chronic intestinal disorder that includes ulcerative colitis (UC) and Crohn's disease (CD). Its pathogenesis involves intricate interactions between pathogenic microorganisms, native intestinal microorganisms, and the intestinal immune system via the oral-gut axis. The strong correlation observed between oral diseases and IBD indicates the potential involvement of oral pathogenic microorganisms in IBD development. Consequently, therapeutic strategies targeting the proliferation, translocation, intestinal colonization and exacerbated intestinal inflammation of oral microorganisms within the oral-gut axis may partially alleviate IBD. Tea consumption has been identified as a contributing factor in reducing IBD, with epigallocatechin gallate (EGCG) being the primary bioactive compound used for IBD treatment. However, the precise mechanism by which EGCG mediates microbial crosstalk within the oral-gut axis remains unclear. In this review, we provide a comprehensive overview of the diverse oral microorganisms implicated in the pathogenesis of IBD and elucidate their colonization pathways and mechanisms. Subsequently, we investigated the antibacterial properties of EGCG and its potential to attenuate microbial translocation and colonization in the gut, emphasizing its role in attenuating exacerbations of IBD. We also elucidated the toxic and side effects of EGCG. Finally, we discuss current strategies for enhancing EGCG bioavailability and propose novel multi-targeted nano-delivery systems for the more efficacious management of IBD. This review elucidates the role and feasibility of EGCG-mediated modulation of the oral-gut axis microbiota in the management of IBD, contributing to a better understanding of the mechanism of action of EGCG in the treatment of IBD and the development of prospective treatment strategies.

Biochemical and Microbiological Aspects of the Oral Cavity of Children and Young People with Neurological Impairment and Oropharyngeal Dysphagia

The components and the salivary flow have a direct influence on the composition of the oral microbiota of children and young people with oropharyngeal dysphagia, and studies have already demonstrated the excessive accumulation of supragingival dental calculus in individuals with enteral nutrition. This study aimed to compare the oral hygiene, biochemical, and microbiological aspects of the oral cavity of children and young people with neurological impairment and oropharyngeal dysphagia. Forty children and young people with neurological impairment and oropharyngeal dysphagia were enrolled and divided into two groups: group I, encompassing 20 participants fed via gastrostomy; and group II, encompassing 20 participants fed via the oral route. Oral hygiene and salivary pH and flow were assessed, and a polymerase chain reaction was performed to evaluate the messenger RNA expressions of Porphyromonas gingivalis, Tanerella forsythia, and Treponema denticola. In groups I and II, the mean Oral Hygiene Index-Simplified scores were 4 and 2, respectively, showing a significant difference; the mean Calculus Index scores were 2 and 0, respectively, showing a significant difference; and the mean pH was 7.5 and 6.0, respectively, showing a significant difference. Bacterial analysis indicated no association between the two groups. It can be concluded that children and young people who use gastrostomy had a poorer oral hygiene, greater dental calculus deposition, and higher salivary pH. The saliva of patients in both groups contained Porphyromonas gingivalis, Tanerella forsythia, and Treponema denticola.

The therapeutic importance of acid-base balance

Baking soda and vinegar have been used as home remedies for generations and today we are only a mouse-click away from claims that baking soda, lemon juice, and apple cider vinegar are miracles cures for everything from cancer to COVID-19. Despite these specious claims, the therapeutic value of controlling acid-base balance is indisputable and is the basis of Food and Drug Administration-approved treatments for constipation, epilepsy, metabolic acidosis, and peptic ulcers. In this narrative review, we present evidence in support of the current and potential therapeutic value of countering local and systemic acid-base imbalances, several of which do in fact involve the administration of baking soda (sodium bicarbonate). Furthermore, we discuss the side effects of pharmaceuticals on acid-base balance as well as the influence of acid-base status on the pharmacokinetic properties of drugs. Our review considers all major organ systems as well as information relevant to several clinical specialties such as anesthesiology, infectious disease, oncology, dentistry, and surgery.

Gender Differences in Stress- and Burnout-Related Factors of University Professors

The aim of the present study was to analyse the gender differences in stress-related factors of university professors. A cross-sectional study was carried out, where gender differences in psychological, nutrition, physical activity, and oral health stress-related factors were analysed in 470 Spanish university professors (58.7% male and 41.3% female, 42.1 ± 9.2 years) through a compendium of questionnaires. The results showed how females presented significantly (p ≤ 0.05) higher scores than males in perceived stress (females: 22.15 ± 4.40 vs. males: 19.69 ± 3.61), emotional exhaustion (females: 20.86 ± 9.51 vs. males: 16.44 ± 9.12), and neuroticism (females: 5.53 ± 1.97 vs. males: 4.77 ± 1.96). These results may be related to higher probabilities to suffer the burnout syndrome, showing possible physical symptoms of this psychological disorder such as dry mouth and gastritis or heartburn. We concluded that female professors presented higher burnout perceived stress, emotional exhaustion, and neuroticism levels than males. Females also presented higher dry mouth, gastritis, and heartburn than males. Female professors showed healthier nutritional habits than males, presenting higher consumption of milk products and fruit per day, a higher number of meals, and less eating between hours and fried food consumption. Nevertheless, females consumed fewer water glasses and practised less weekly sport than male professors.

Cultural Differences in Stress-Related Psychological, Nutrition, Physical Activity and Oral Health Factors of Professors

With the aim to explore cultural differences in stress-related psychological, nutrition, physical activity, and oral health factors between Spanish and Latin American professors, we analysed stress-related factors in 598 professors (39.9% male, 60.1% female, 41.3 ± 9.8 years) by a collection of questionnaires, which involved psychological, nutritional, physical activity and oral health items. Results showed how Spanish professors presented significantly (p ≤ 0.05) higher scores than Latin American professors in perceived stress (Spanish: 21.40 ± 4.32 vs. Latin American: 20.36 ± 4.31), teaching stress (Spanish: 6.59 ± 2.28 vs. Latin American: 6.00 ± 2.99) and neuroticism (Spanish: 5.40 ± 2.10 vs. Latin American: 4.58 ± 1.72). Spanish professors also showed healthier nutritional and physical activity habits than their Latin American counterparts, presenting higher consumption of milk products and a higher numbers of meals per day, greater weekly meat and fish consumption and higher weekly resistance training, as well as less eating between hours and snacking consumption. Nevertheless, Spanish professors brushed their teeth less and showed a higher smoking habit than Latin American professors. We concluded that there were cultural differences between Spanish and Latin American professors. In the present research, Spanish professors showed significantly higher burnout levels, teaching stress, perceived stress, and neuroticism than Latin American professors, and several differences were also found around health behaviours. These differences in perceived stress, teaching stress and burnout syndrome may be due to the habituation process of Latin American professors, and probably are associated with a higher stressful and demanding socio-cultural context.

Oropharyngeal colonization: epidemiology, treatment and ventilator-associated pneumonia prevention

Oropharyngeal (OP) colonization and ventilator-associated pneumonia (VAP) mechanisms are tightly linked. A significant within-population variation in OP colonization has been described, with its composition being dependent from patients' severity. For instance, healthy subjects have a very low rate in Gram-negative bacteria (GNB) colonization, while its rate rises in comorbid patients, reaching high proportions in ICU patients. Various factors can be put forward to explain the modifications of hospital acquired OP. ICU patients might suffer from underlying diseases; the gastric reflux induced by the presence of nasogastric tubes and the patients' position influences OP colonization; salivary composition might influence OP content, as it modulates bacterial adhesion and induces reversible bacterial changes enhancing bacterial binding. The transition from OP colonization to VAP has been shown in numerous studies, with the digestive tract acting as a filter, or as a reservoir. Some therapies have been investigated to modulate OP colonization, in order to reduce the risk for VAP. Among those, mammalian antimicrobial peptides have been shown effective in reducing GNB colonization in healthy subjects, but failed in preventing VAP in ICU patients. The widely used chlorhexidine was tested in numerous trials. Data on its efficacy are conflicting, and meta-analyses yield discordant results. Above all, several drawbacks have aroused: a poor tolerance of concentrated solutions; an increased risk of death in the less severe patients; and a reduced susceptibility towards chlorhexidine of number of VAP pathogens. Proanthocyanidins, used to prevent Escherichia coli adhesion to the urothelium, have been tested in mice model of pneumonia with interesting results. Some complementary data are needed before moving to clinical research. Future research paths should include a reappraisal of OP colonization; finding better formulations for chlorhexidine; define the best populations to target oral decontamination and developing other strategies to prevent and treat OP colonization.

Oral-gut connection: one step closer to an integrated view of the gastrointestinal tract?

Although an enrichment of orally derived bacteria is reported in the gut microbiota of patients with several diseases, it is mostly unknown whether oral bacteria can colonize and induce intestinal inflammation. In a recent paper in Science, Atarashi et al.¹ from Kenya Honda's laboratory show that a subset of orally derived bacteria colonizes and persists in the gut, leading to activation of the intestinal immune system and subsequent chronic inflammation in a susceptible host. The impact of oral health status as a potential contributor to inflammatory diseases at distal sites of the body deserves consideration.

Oral microbial carriage in oral squamous cell carcinoma patients at the time of diagnosis and during radiotherapy - a comparative study

OBJECTIVES

Tobacco chewing habit, presence of squamous cell carcinoma in oral cavity and radiotherapy causes alterations in healthy oral microflora. Abnormal flora developed due to radiotherapy in oral squamous cell carcinoma (OSCC) patients can exacerbate mucositis and can cause systemic infections. The role of oral microorganisms in carcinogenesis is gaining interest recently. Abnormal flora in development of second tumor in the field of first tumor is to be established. The study fundamentally tries to evaluate the shift that occurs during the radiotherapy in OSCC patients.

METHODS

Microbial analysis of saliva samples from OSCC patients undergoing radiotherapy, tobacco chewers and controls was undertaken. The microorganisms were grouped into categories as total aerobes, total anaerobes, candida, coliforms and gram negative anaerobic bacteria.

RESULTS

The frequency of isolation of total aerobes, total anaerobes, coliforms and gram negative anaerobic bacteria was significantly high in OSCC patients compared to healthy controls whereas candida was isolated most frequently during radiation period. The tobacco chewers showed significant increase in colony forming units of total aerobes and coliforms. All the microbial groups were high in OSCC and radiotherapy patients. While OSCC patients showed significant increase in total anaerobes and gram negative anaerobes, candida was increased in radiotherapy patients only.

CONCLUSION

Habits promote coliforms. Tumor supports efficiently anaerobes and candida. The latter is supported more by radiation. The study stresses the importance on administration of appropriate antimicrobial therapy right at the time of diagnosis of the lesion.

Role of salivary function in patients with globus pharyngeus

BACKGROUND

Our aim was to investigate the prevalence and the clinical role of salivary hypofunction in patients with globus sensation.

METHODS

We conducted a prospective observational study in 340 patients with globus pharyngeus. A standard questionnaire and (99m)Tc-pertechnate salivary scintigraphy were used to evaluate salivary hypofunction, with a full examination from the nasal cavity to the larynx (N = 303). We also investigated the effect of xerostomia management on globus symptoms (N = 252).

RESULTS

The symptom scores for xerostomia were higher in patients with severe globus (p < .05). Objective salivary hypofunction was noted in 57.4% of the patients, based on the reference values from control groups. Globus symptoms were more severe in the subgroup with salivary hypofunction (p = .0447). Conservative management of xerostomia significantly reduced the severity of globus at 1 and 3 months (p = .0002) regardless of salivary function.

CONCLUSIONS

Salivary hypofunction seems to be an aggravating factor in globus pharyngeus, but not a direct cause. Conservative management of xerostomia improves globus symptoms.

Bacterial community-acquired pneumonia in older patients

Pneumonia in the elderly remains a major source of morbidity and mortality in an age group that is growing in numbers. It remains unclear whether the propensity of older adults to develop community-acquired pneumonia represents an aging of host defenses, secondary effects of comorbid disease, or both. The signs and symptoms of pneumonia in the elderly are more subtle than in younger populations, which may lead to a delay in diagnosis. Although therapy for community-acquired pneumonia in the elderly is the same as for younger populations, mortality is higher, leading to an important role for prevention.

Signature-tagged mutagenesis of Klebsiella pneumoniae to identify genes that influence biofilm formation on extracellular matrix material

Klebsiella pneumoniae causes urinary tract infections, respiratory tract infections, and septicemia in susceptible individuals. Strains of Klebsiella frequently produce extended-spectrum beta-lactamases, and infections with these strains can lead to relatively high mortality rates (approximately 15%). Other virulence factors include production of an antiphagocytic capsule and outer membrane lipopolysaccharide (LPS), which mediates serum resistance, as well as fimbriae on the surface of the bacteria. Type 1 fimbriae mediate adherence to many types of epithelial cells and may facilitate adherence of the bacteria to the bladder epithelium. Type 3 fimbriae can bind in vitro to the extracellular matrix of urinary and respiratory tissues, suggesting that they mediate binding to damaged epithelial surfaces. In addition, type 3 fimbriae are required for biofilm formation by Klebsiella pneumoniae on plastics and human extracellular matrix; thus, they may facilitate the formation of treatment-resistant biofilm on indwelling plastic devices, such as catheters and endotracheal tubing. The presence of these devices may cause tissue damage, allowing Klebsiella to grow as a biofilm on exposed tissue basement membrane components. Though in vivo biofilm growth may be an important step in the infection process, little is known about the genetic factors required for biofilm formation by Klebsiella pneumoniae. Thus, we performed signature-tagged mutagenesis to identify factors produced by K. pneumoniae strain 43816 that are required for biofilm formation. We identified mutations in the cps capsule gene cluster, previously unidentified transcriptional regulators, fimbrial, and sugar phosphotransferase homologues, as well as genetic loci of unknown function, that affect biofilm formation.

The role of oral microbial colonization in ventilator-associated pneumonia

The present article reviews the association between microbial colonization of the oral cavity and the lungs in critically ill patients that develop ventilator-associated pneumonia (VAP) in the intensive care unit (ICU) setting. The risk factors and microorganisms associated with VAP are presented. The role of oral colonization of VAP-associated pathogens (VAP-AP) in the development of VAP is examined. We explore the potential factors involved in oral colonization of VAP-AP, which are atypical bacteria for the oral cavity. Strategies for the prevention or moderation of oral colonization of VAP-AP have had limited success. We need a deeper understanding of the pathophysiology of VAP in order to reduce the morbidity, mortality, and cost from this common complication in ICU medicine and surgery.

Lung infections and aging

Respiratory tract infections are the leading cause of death due to infectious disease in the elderly. Many factors, especially waning immune responses and the onset of age-associated organ dysfunction, likely account for an increase in susceptibility to respiratory tract infection in the elderly, and morbidity and mortality rates are substantially greater for the elderly when outcomes are compared to that of younger individuals. The presence of underlying disease states such as chronic obstructive pulmonary disease (COPD) or other organ system disease further increases the likelihood of developing severe pneumonia in the elderly population, and the frail elderly, particularly when institutionalized in chronic care facilities, are at high risk for developing severe and recurrent pneumonia. This article will discuss various factors associated with advanced age that predispose the elderly to respiratory infections and summarize current approaches to treatment and prevention.

Inadequate salivary flow and poor oral mucosal status in intubated intensive care unit patients

OBJECTIVE

To investigate salivary flow and frequency of oral mucositis in intensive care unit patients compared with patients admitted because of elective coronary artery bypass graft (CABG) surgery. In addition, the pattern of oropharyngeal colonization was investigated in these patients.

DESIGN

Prospective study.

SETTING

Mixed intensive care unit and cardiosurgical ward.

PATIENTS

In this study, 24 ventilated intensive care unit patients and 20 CABG patients were included.

MEASUREMENTS AND MAIN RESULTS

Two dental hygienists examined intensive care unit patients for the presence of periodontal disease and mucositis at admission and subsequently every week during their stay in the intensive care unit. At the same time, stimulated salivary flow and salivary total immunoglobulin A output were measured. Oropharyngeal cultures were obtained as well. CABG patients were examined the day before the operation, 1 day, 1 wk, and 2 wks after the operation. The following results were obtained: a) temporarily reduced postoperative stimulated salivary flow and total salivary immunoglobulin A output in CABG patients and nearly absent stimulated salivary flow in intensive care unit patients; b) oropharyngeal colonization with potentially pathogenic microorganisms in intensive care unit and not in CABG patients; and c) the increase in mucositis index in intensive care unit patients paralleled the increase in potentially pathogenic microorganism oropharyngeal colonization, especially and.

CONCLUSIONS

Absence of adequate salivary flow in intubated intensive care unit patients causes severe xerostomia, which may contribute to the development of mucositis and oropharyngeal colonization with Gram-negative bacteria.

Oral clearance and pathogenic oropharyngeal colonization in the elderly

The elderly have an increased incidence of oropharyngeal colonization with respiratory pathogens, a well-known risk factor for the development of pneumonia. Changes in the oral milieu may occur secondary to decreased salivary production and abnormalities in swallowing. These abnormalities, common in the elderly, may result in impaired clearance of organisms, allowing pathogenic colonization. To test this hypothesis, we performed a prospective cross-sectional analysis of 75 elderly institutionalized patients and measured oral clearance using (99m)Tc-human serum albumin (HSA) administered to the oropharynx. Oropharyngeal cultures, salivary cell populations, elastase activity, and clinical parameters were measured simultaneously. Retention of radiolabel ranged from 100% to 2.3% over 120 min of observation. Clearance in the oropharynx was significantly decreased in those patients who had oropharyngeal colonization with gram-negative bacilli (GNB), Staphylococcus aureus (SA), or yeast compared with those demonstrating normal flora by 95% confidence intervals. Decreased clearance was also seen in patients on antidepressants by 95% confidence levels. The absolute number of salivary lymphocytes/ml and buccal cells/ml was increased in colonized patients versus noncolonized persons (mean +/- SEM, 128 x 10(3) +/- 49 x 10(3), 25.4 +/- 11.6 x 10(3)). Elastase activity was elevated in patients who had GNB compared with patients without GNB (mean +/- SEM, 10.6 nM +/- 5.7, versus 2.2 nM +/- 1.2, p = 0.036). We conclude that a decrease in salivary clearance of potentially pathogenic organisms may be a major risk factor for the development of colonization in the elderly.

Oral colonization of aerobic and facultatively anaerobic gram-negative rods and cocci in irradiated, dentate, xerostomic individuals

This study aimed at investigating the oral colonization of aerobic and facultatively anaerobic gram-negative rods and cocci in head- and neck-irradiated, dentate, xerostomic individuals. Subjects were recruited from a nasopharyngeal carcinoma clinic and were segregated into group A: <60 years (n=25, 48+/-6 years, 5+/-5 years post-irradiation) and group B: >or=60 years (n=8, 67+/-4 years, 2+/-2 years post-irradiation) and were compared with age- and sex-matched normal individuals, group C: <60 years (n=20, 44+/-12 years) and group D: >or=60 years (n=10, 70+/-3 years). Selective culture of the oral rinse samples was carried out to isolate, quantify and speciate (using API 20E kit) aerobic and facultatively anaerobic gram-negative rods and cocci recovery. All test subjects were put under comprehensive oral and preventive care for 3 months, and 12 group A and 5 group B subjects were recalled for reassessment of aerobic and facultatively anaerobic gram-negative rods and cocci colonization. All identical isolates, pre- and post-hygienic care, were phenotypically (Vitek, Hazelwood, MA and antibiogram profile) and genotypically (pulsed-field gel electrophoresis) evaluated. The aerobic and facultatively anaerobic gram-negative rods and cocci isolated from the first round oral rinse samples included: Acinetobacter, Neisseria, Chryseomonas, Flavimonas, Pseudomonas, Citrobacter, Enterobacter, Escherichia, Klebsiella, Flavobacterium and Weeksella species. The aerobic and facultatively anaerobic gram-negative rods and cocci isolation rate was high for irradiated individuals, and they were 64/25% and 100/80% for groups A/C and B/D, respectively. Recovery of aerobic and facultatively anaerobic gram-negative rods and cocci and Klebsiella pneumoniae subsp. pneumoniae in oral rinse samples were found to be significantly more prevalent in the irradiated subjects (groups A and B). Enterobacteriaceae were more frequently isolated from oral rinse samples of aged irradiated subjects (group B vs D, P<0.05), where the quantity of Citrobacter freundii (colony-forming units/ml oral rinse) was also significantly elevated. The isolation rate of aerobic and facultatively anaerobic gram-negative rods and cocci after hygienic care remained unchanged; 3 of 12 and 3 of 5 of the recalled subjects from groups A and B, respectively, harbored same aerobic and facultatively anaerobic gram-negative rods and cocci species. However, only two pairs of K. pneumoniae subsp. pneumoniae, sequentially isolated from same patients in group B, were found to be identical by pulsed-field gel electrophoresis. This may be due to reinfection of the microbes from the same source or permanent colonization. In conclusion, irradiation-induced xerostomia seems to favor frequent, repeated, transient intraoral colonization of aerobic and facultatively anaerobic gram-negative rods and cocci.

Histatin 5 inhibits inflammatory cytokine induction from human gingival fibroblasts by Porphyromonas gingivalis

Porphyromonas gingivalis is a gram-negative rod associated with the progression of human periodontal disease. It has been demonstrated that outer-membrane proteins as well as lipopolysaccharides from P. gingivalis ATCC 53977 can induce interleukin 6 (IL-6) and IL-8 from the cells of the periodontium in vitro. But, they cannot induce IL-1 and tumor necrosis factor-alpha from the cells. In the present study, we studied the effects of salivary protein on cytokine induction from human gingival fibroblasts by P. gingivalis outer-membrane protein. Histatin 5 suppressed the IL-6 and IL-8 induction by P. gingivalis outer-membrane protein. This activity was more effective when outer-membrane protein was incubated with histatin 5 before addition to the cell culture. The present study indicates that histatin 5 restrains induction of inflammatory cytokines by periodontal pathogens and that histatin is one of the salivary proteins responsible for this activity.

Oropharyngeal gram-negative bacillary carriage in chronic obstructive pulmonary disease: relation to severity of disease

The prolonged presence of aerobic Gram-negative bacilli (AGNB) in the oropharynx is termed 'carriage'. AGNB carriage rates are low in populations of healthy individuals. Previously, severity of underlying disease has been positively correlated with oropharyngeal AGNB carriage rate. Overgrowth of AGNB at the oropharynx poses a significant risk of endogenous infection in end-stage chronic obstructive pulmonary disease (COPD) patients. The aims of this study were to undertake an epidemiological survey of the oropharyngeal flora of COPD patients and to correlate oropharyngeal carriage of AGNB with severity of disease. Two oral rinses were obtained, within a 2-day interval, from 40 COPD patients comprising three disease severity groups: 1. mild, 2. moderate and 3. severe. Eighty oral rinses were quantitatively (1:10 dilution series) cultured for AGNB and yeasts using broth enrichment. The mean AGNB carriage rate was 15%. AGNB carriage rates of 0, 7.7 and 29.4% were observed within the mild, moderate and severe disease groups, respectively. The mean yeast carriage rate was 33.3%. Yeast carriage rates of 33.3, 15.4 and 64.7% were observed within the mild, moderate and severe disease groups, respectively. Carriage of Staphylococcus aureus was 5%. Rates of oropharyngeal carriage of AGNB (1/23 vs. 5/17) and yeasts (5/23 vs. 11/17) were significantly higher within the severe disease group than in non-severe disease groups. Oropharyngeal carriage of AGNB in end-stage COPD patients (forced expiratory volume in 1 sec, FEV1 < 50% predicted) presents a potential source of Gram-negative endogenous pneumonia. This outcome may be promoted by intubation and some flora-suppressing antibiotic therapies.

Oropharyngeal Gram-negative bacillary carriage: a survey of 120 healthy individuals

BACKGROUND

The presence of aerobic Gram-negative bacilli (AGNB) in the oropharynx can be either temporary or persistent. Prolonged colonization (ie, carriage) is distinguished from transient presence (ie, acquisition), which often occurs in healthy individuals but less frequently in those with underlying disease. Prevalence rates of up to 61.1% quoted previously for healthy individuals were obtained by using single sample surveys, which fail to differentiate acquisition from carriage.

STUDY OBJECTIVES

To illustrate the need to distinguish carriage from acquisition in a healthy population at risk of acquisition of AGNB, and to show that although differing groups of healthy individuals may acquire oropharyngeal AGNB at differing frequencies, carriage is rare in healthy individuals.

PARTICIPANTS

Two oral rinses were obtained within a 2-day interval from 120 healthy individuals comprising 40 nurses, 40 students, and 40 laboratory-associated persons.

DESIGN

Two hundred forty oral rinses were quantitatively (1:10 dilution series) cultured for AGNB by using broth enrichment.

MEASUREMENTS AND RESULTS

The rate of AGNB carriage based on two consecutive samples positive for the same AGNB was 6.6%; the rate of AGNB acquisition based on one positive sample was 35.8%. The concentrations of all carried and acquired AGNB were < or = 103 cfu/mL. AGNB acquisition was significantly higher in students (52.5%) compared to nurses (32.5%) and laboratory-associated persons (22.5%; p < 0.05).

CONCLUSION

Healthy individuals rarely carry oropharyngeal AGNB, suggesting effective oropharyngeal clearance in a healthy population predisposed to acquisition. Apparently, the oropharyngeal mucosa in healthy individuals is not receptive to adhesins of AGNB, resulting in rapid elimination of these bacteria.

Klebsiella spp. as nosocomial pathogens: epidemiology, taxonomy, typing methods, and pathogenicity factors

Bacteria belonging to the genus Klebsiella frequently cause human nosocomial infections. In particular, the medically most important Klebsiella species, Klebsiella pneumoniae, accounts for a significant proportion of hospital-acquired urinary tract infections, pneumonia, septicemias, and soft tissue infections. The principal pathogenic reservoirs for transmission of Klebsiella are the gastrointestinal tract and the hands of hospital personnel. Because of their ability to spread rapidly in the hospital environment, these bacteria tend to cause nosocomial outbreaks. Hospital outbreaks of multidrug-resistant Klebsiella spp., especially those in neonatal wards, are often caused by new types of strains, the so-called extended-spectrum-beta-lactamase (ESBL) producers. The incidence of ESBL-producing strains among clinical Klebsiella isolates has been steadily increasing over the past years. The resulting limitations on the therapeutic options demand new measures for the management of Klebsiella hospital infections. While the different typing methods are useful epidemiological tools for infection control, recent findings about Klebsiella virulence factors have provided new insights into the pathogenic strategies of these bacteria. Klebsiella pathogenicity factors such as capsules or lipopolysaccharides are presently considered to be promising candidates for vaccination efforts that may serve as immunological infection control measures.

The oral prevalence of aerobic and facultatively anaerobic gram-negative rods and yeasts in semi-recluse human vegetarians

Limited data exist on the oral ecology of vegetarians. Hence the dental and periodontal status, and the oral prevalence of aerobic and facultatively anaerobic Gram-negative rods (AGNR) and yeasts, were studied in 36 semi-recluse, vegetarian, Buddhist monks and nuns in Hong Kong. The oral prevalence of AGNR and yeasts was 61.1% and 33.3%. There was no correlation between the prevalence of AGNR and/or yeasts and the incidence of carious or filled teeth and the health status of the periodontium. Rather, the results of this study combined with those of previous studies suggest that increasing age and the consumption of food prepared in communal kitchens might be more important contributory factors in the oral prevalence of AGNR than the nature of the diet itself or the health of the dentition and periodontium.

Oral and oropharyngeal prevalence of Enterobacteriaceae in humans: a review

Members of the Enterobacteriaceae family are widely distributed in nature and exhibit substantial diversity in ecology, host range and pathogenic potential for man. While wide discrepancies in methodology exist between epidemiological studies, the available data indicate an increased prevalence of oral and/or oropharyngeal Enterobacteriaceae carriage in patients with illnesses of varying severity compared with healthy subjects. This paper reviews the prevalence of Enterobacteriaceae in the oral and oropharyngeal region of healthy human subjects and those affected by different disease entities, and discusses the complexities associated with collating and interpreting such data. The effect of antimicrobials and antiseptics on oral and oropharyngeal Enterobacteriaceae has also been reviewed, while highlighting the gaps in knowledge and future research directions.

The role of salivary function on oropharyngeal colonization

Aspiration of oropharyngeal flora is the most common route of acquiring Gram-negative pneumonia, a major nosocomial infection. Epidemiologic studies indicate that the elderly are at increased risk for developing these life-threatening pneumonias. The primary objective of this study was to determine the effects of salivary oral defenses against Gram-negative colonization. The study population consisted of 41 male outpatients, age 70 and older, seen at the Denver VAMC. The group included subjects with both diminished and normal salivary flow. Each subject answered a questionnaire regarding overall health, medication use, and symptoms of salivary dysfunction. We then collected whole saliva, unstimulated and stimulated parotid saliva, and performed a throat swab on each patient. For each throat culture, analysis was done to identify Gram-negative bacteria. Flow rates between colonized (n = 6) and noncolonized subjects (n = 34) were compared. While there were no significant differences in the flow rates between the two groups, a trend was noticed in that flow rates were lower for all three flow measures in the colonized group (whole, 22% decrease; unstimulated, 22% decrease; and stimulated, 28% decrease). These preliminary findings suggest that subjects with diminished salivary flow may possibly be at increased risk for oropharyngeal Gram-negative colonization. Research on the role that saliva plays in oropharyngeal bacterial colonization is continuing.

Salivary secretion rate, yeast cells, and oral candidiasis in patients with acute leukemia

Stimulated salivary secretion rate was repeatedly determined in 29 patients with acute leukemia during two periods of cytotoxic treatment in myelosuppressive doses. For comparison, the salivary secretion rate was studied in 83 healthy persons and in three other groups of hospitalized patients without malignant disorders. At the start of cytotoxic treatment the secretion rate in the patients with leukemia was lower than in healthy persons. The rate fell significantly after 1 to 3 days and later rose to the level seen in the healthy persons. Several interacting factors may have contributed to the decrease in salivary secretion rate, but the most important factor was probably the use of antiemetic drugs during the first 3 days of the study periods. No relationship was found between salivary secretion rate and the number of gram-negative rods found in the mouth. Patients with low salivary secretion rates had high numbers of yeast cells and more often oral candidiasis.

Oral carriage of Candida species and coliforms in patients with burning mouth syndrome

The oral carriage of Candida species and coliforms in a healthy adult population and a group of patients with burning mouth syndrome (BMS) was investigated. The intra-oral prevalence of Candida species and coliforms was higher in the BMS group compared with the controls. The most frequent yeast isolated from the BMS group was Candida albicans while Enterobacter and Klebsiella species were the most prevalent coliforms. The possible reasons and the significance of the above findings are discussed.

Role of sialic acid in saliva-mediated aggregation of Pseudomonas aeruginosa isolated from cystic fibrosis patients

The mechanism of saliva-mediated aggregation of Pseudomonas aeruginosa in subjects with and without cystic fibrosis (CF) was investigated. Virtually all saliva from CF patients that we tested strongly agglutinated the Pseudomonas cells and was heat stable to 56 degrees C, whereas saliva from subjects without CF had a decreased aggregating ability and was heat sensitive. When saliva was treated with neuraminidase and proteases, and also when P. aeruginosa cells were treated with mixed gangliosides, there was a decrease in aggregating activities. However, neither the addition of the acid-hydrolyzed ganglioside nor the treatment of the P. aeruginosa cells by sugars had any effect on subsequent aggregating activities. Therefore, the release of sialic acid by enzymatic treatments of saliva, as well as the blockage of the sialic acid-binding sites on the cell wall by mixed gangliosides, resulted in the parallel loss of saliva-mediated aggregating activity of P. aeruginosa. The level of free sialic acid released by endogenous neuraminidase was higher in the saliva from CF patients than in that from the non-CF subjects examined. The increased aggregation of P. aeruginosa mediated by saliva from patients with CF seems to be directly related to the sialic acid content present, suggesting that this acid molecule acts as the salivary receptor for P. aeruginosa.

Bacterial adhesion to cerebrospinal fluid shunts

Bacterial adherence to cerebrospinal fluid (CSF) shunts was analyzed in vivo and in vitro. Scanning electron micrographs (SEM's) of catheters removed from pediatric patients with shunts infected by Staphylococcus aureus or Klebsiella pneumoniae revealed numerous bacterial cells and microcolonies, leukocytes, and erythrocytes attached to the CSF catheters' inner walls, as well as the existence of surface irregularities, such as fissures, rugosities, and holes. Permeability analyses and SEM's demonstrated that catheters develop physical alterations over the period of implantation. Different bacterial strains presented a different in vitro adherence to CSF shunts, suggesting that this attachment may be affected by specific properties of the outer structures of each strain. The attachment of microbial pathogens to CSF shunts seems to contribute to the persistence of bacterial cells within a catheter and the onset of recurrent shunt infection. This study demonstrated that some bacteria can remain attached within shunts in vitro despite a CSF flow at rates up to 200 times higher than those normally demonstrated in vivo. Furthermore, surface irregularities found throughout this study may help to anchor and hide bacterial microcolonies. Based on these findings, it seems advisable to remove an infected shunt and to replace it with a new one after proper antimicrobial therapy, in order to prevent recurrent infections.

Dog tracheal epithelial cells in culture synthesize sulfated macromolecular glycoconjugates and release them from the cell surface upon exposure to extracellular proteinases

To determine whether glycoconjugates can be released into airways by surface epithelial cells that do not contain secretory granules and, if so, whether extracellular proteinases can affect this release, we studied dog tracheal epithelial cells after 8-10 days in culture. Ultrastructurally, these cells showed an extensive cell surface coat and no secretory granules. Cells were pulse labeled with radioactive sulfate (Na2 35SO4, 50 microCi/ml/24 h) and washed free of the unbound label. Release of sulfated products was then measured at 20-min intervals under basal conditions and again after 20 min of incubation with various extracellular proteinase. We found that these cells synthesized sulfated products and released them spontaneously and continuously into the medium. In addition, trypsin, Pseudomonas aeruginosa elastase, thermolysin, Staphylococcus aureus proteinase, mast cell chymase, plasmin, and kallikrein (each at 10(-7) M except plasmin, at 5 X 10(-6) M) increased the release of sulfated products to 77-667% over baseline release (p less than 0.01, n = 5 dogs for each); preliminary results showed that human neutrophil elastase was also very potent. The sulfated products released by trypsin had an apparent molecular weight of greater than or equal to 10(6) da as determined by gel filtration on Sepharose Cl-4B. Over 50% of these 35S-labeled products were digested to low-molecular-weight products (500-2000 da) upon incubation with endo-beta-galactosidase or with keratanase, suggesting that they are glycoconjugates containing poly(N-acetyllactosamine)-type carbohydrate chains. Decrease in cell staining by lectins specific for poly(N-acetyllactosamine), which accompanied the release of glycoconjugates, indicates that these sulfated glycoconjugates were released by proteinases from the apical cell surface. We conclude that cultured tracheal epithelial cells synthesize and transport sulfated macromolecular glycoconjugates to apical cell surfaces. These glycoconjugates are released from cell surfaces when exposed to extracellular proteinases. We therefore suggest that macromolecular glycoconjugates in airway secretions can originate not only from secretory granules but also from epithelial cell surfaces during airway inflammation.

Pseudomonas aeruginosa in the oral cavity and sputum of patients with cystic fibrosis

Patients with cystic fibrosis (CF) are often hosts to colonies of both mucoid and nonmucoid strains of Pseudomonas aeruginosa. The major pathogens for chronic and recurrent pulmonary infection in these patients are the mucoid variants of P. aeruginosa. Of the 31 CF patients studied, 14 patients yielded both mucoid and nonmucoid strains of P. aeruginosa from the various oral ecologic sites and saliva. Of the sites tested, the dorsum of the tongue gave the highest yield of P. aeruginosa (27 strains), followed by the buccal mucosa (17 strains), saliva (15 strains), and dental plaques (6 strains). Eleven patients had P. aeruginosa in the oral cavity and sputum simultaneously. Antibiotic susceptibility tests on these multiple isolates suggest that CF patients may be cocolonized or coinfected by two or more strains of P. aeruginosa. Therefore, it may be important to identify multiple isolates of P. aeruginosa, not only from sputum cultures but also from oral cultures, for antibiotic-susceptibility testing. Oral colonization by the mucoid variants of P. aeruginosa may lead to further colonization in the lower respiratory tract and subsequent pulmonary infection in CF patients.