SARS-CoV-2 genomic and subgenomic RNAs in diagnostic samples are not an indicator of active replication

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) was first detected in late December 2019 and has spread worldwide. Coronaviruses are enveloped, positive sense, single-stranded RNA viruses and employ a complicated pattern of virus genome length RNA replication as well as transcription of genome length and leader containing subgenomic RNAs. Although not fully understood, both replication and transcription are thought to take place in so-called double-membrane vesicles in the cytoplasm of infected cells. Here we show detection of SARS-CoV-2 subgenomic RNAs in diagnostic samples up to 17 days after initial detection of infection and provide evidence for their nuclease resistance and protection by cellular membranes suggesting that detection of subgenomic RNAs in such samples may not be a suitable indicator of active coronavirus replication/infection.

SARS-CoV-2 genomic and subgenomic RNAs in diagnostic samples are not an indicator of active replication

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) was first detected in late December 2019 and has spread worldwide. Coronaviruses are enveloped, positive sense, single-stranded RNA viruses and employ a complicated pattern of virus genome length RNA replication as well as transcription of genome length and leader containing subgenomic RNAs. Although not fully understood, both replication and transcription are thought to take place in so-called double-membrane vesicles in the cytoplasm of infected cells. Here we show detection of SARS-CoV-2 subgenomic RNAs in diagnostic samples up to 17 days after initial detection of infection and provide evidence for their nuclease resistance and protection by cellular membranes suggesting that detection of subgenomic RNAs in such samples may not be a suitable indicator of active coronavirus replication/infection.

Oral EBV and KSHV Infection in HIV

The gamma herpesviruses, Kaposi’s-sarcoma-associated herpesvirus (KSHV) and Epstein-Barr virus (EBV), are tightly associated with the development of AIDS-associated oral disease and malignancy during immune suppression. The objective of this investigation was to characterize oral infection and pathogenesis in healthy and immune-suppressed individuals. To characterize oral EBV and KSHV infection, we examined throat washings and oral epithelial cells from HIV-positive and HIV-negative individuals. Quantitative/real-time polymerase-chain-reaction (PCR) assays, transmission electronmicroscopy, immunostaining, and sequence analysis were used to identify viral infection. Virus was isolated from throat-wash samples and was used to infect epithelial and lymphoid cell lines. We detected EBV and KSHV in the oral cavity in healthy and immune-suppressed individuals. Viral strain analysis of KSHV K1 in multiple clones from the oral cavities of healthy persons and immunosuppressed patients detected several strains previously detected in KS lesions, with minor strain variation within individuals. Immunoelectron microscopy for multiple viral antigens detected consistent expression of viral proteins and oral epithelial specimens. In oral epithelial cells infected with wild-type KSHV in vitro, the K8.1 glycoprotein associated with lytic KSHV infection was detected in both primary and telomerase immortalized oral epithelial cultures by 24 hours post-infection. Virions were detected, subsequent to infection, by scanning electron microscopy. Oral epithelial cells were also infected in vitro with wild-type EBV originating from throat washes. Analysis of these data suggests that, like EBV, KSHV infection is present in the oropharynx of healthy individuals, is transmissible in vitro, and may be transmitted by saliva.

Reduction of DNA damage by curcumin and celecoxib in epithelial cell cultures of the oropharynx after incubation with tobacco smoke condensate

BACKGROUND

Tobacco smoke, as the major risk factor for the development of squamous cell cancer of the head and neck (HNSCC), contains various xenobiotics, such as polycyclic aromatic hydrocarbons, nitrosamines, aromatic amines and phenols. Chemoprevention either by artificial agents such as celecoxib, or natural compounds such as curcumin, might offer a chance to reduce the risk of developing malignant transformation.

MATERIALS AND METHODS

In order to evaluate the DNA-damaging effects of smoke condensate towards human mucosa cells of the oropharynx, mini organ cultures (MOC) of macroscopically healthy pharyngeal tissue of 40 patients with oropharyngeal SCC were used. After incubation with smoke condensate DNA damage was evaluated with the alkaline single-cell microgel electrophoresis (comet assay). The chemoprotective potential of curcumin and celecoxib was analyzed after their incubation with the condensate-treated MOCs. As DNA-damaging and chemopreventive effects might not be equally distributed over the whole DNA, fragmentation of the epithelial growth factor receptor (EGFR) gene was additionally examined by Comet fluorescence in situ hybridization (FISH).

RESULTS

As expected, tobacco smoke condensate caused significant DNA fragmentation compared to the negative control. No enhanced damage was observed on the EGFR gene. DNA fragmentation was significantly reduced when MOCs were incubated with celecoxib (p ≤ 0.001) and with curcumin (p ≤ 0.001).

CONCLUSION

Both celecoxib and curcumin showed considerable chemoprotective effects towards the impact of smoke condensate. No evidence was found for higher susceptibility to damage in the EGFR gene.

In vivo acquisition of prophage in Streptococcus pyogenes

Genomic analysis of 12 Streptococcus pyogenes genomes representing six different serotypes reveals that they are poly-lysogenized, with as many as seven separate phage genomes (some of which are defective). Sequence alignments of these genomes (excluding incorporated prophage) have revealed that they are approximately 90% conserved, indicating that their diversity and disease capacity might be phage related. However, because S. pyogenes are only found in humans, how are new phages acquired? In vitro and in vivo experiments show that efficient phage transfer from donor to recipient streptococci occurs in the presence of mammalian cells. This suggests that, through evolution, phage have devised a system whereby progeny phage are induced and transferred to host streptococci at a site where host organisms are more prevalent.

Candida albicans protein kinase CK2 governs virulence during oropharyngeal candidiasis

To identify Candida albicans genes whose proteins are necessary for host cell interactions and virulence, a collection of C. albicans insertion mutants was screened for strains with reduced capacity to damage endothelial cells in vitro. This screen identified CKA2. CKA2 and its homologue CKA1 encode the catalytic subunits of the protein kinase CK2. cka2delta/cka2delta strains of C. albicans were constructed and found to have significantly reduced capacity to damage both endothelial cells and an oral epithelial cell line in vitro. Although these strains invaded endothelial cells similarly to the wild-type strain, they were defective in oral epithelial cell invasion. They were also hypersusceptible to hydrogen peroxide, but not to high salt or to cell wall damaging agents. A cka1delta/cka1delta mutant caused normal damage to both endothelial cells and oral epithelial cells, and it was not hypersusceptible to hydrogen peroxide. However, overexpression of CKA1 in a cka2delta/cka2delta strain restored wild-type phenotype. Although the cka2delta/cka2delta mutant had normal virulence in the mouse model of haematogenously disseminated candidiasis, it had significantly attenuated virulence in the mouse model of oropharyngeal candidiasis. Therefore, Cka2p governs the interactions of C. albicans with endothelial and oral epithelial cells in vitro and virulence during oropharyngeal candidiasis.

Effects of epidermal growth factor and keratinocyte growth factor on the growth of oropharyngeal keratinocytes in coculture with autologous fibroblasts in a three-dimensional matrix

Tissue engineering of oropharyngeal mucosa is rendered complex by the fact that oropharyngeal keratinocytes are difficult to culture in the long term and do not grow well after several subcultivations. Three populations of oropharyngeal keratinocytes were isolated by a method based on different levels of beta(1)-integrin expression. In particular, keratinocytes were isolated between cell fractions that adhere rapidly on collagen-IV-coated culture dishes (RAC-IV) and populations that are less adherent (RAC-IV-D). The total fraction of both subpopulations served as a control (RAC-IV-T). The epidermal growth factor (EGF) and the keratinocyte growth factor (KGF) were examined with regard to their effects on the growth of the three populations. Growth curves of all three cell fractions grown with or without EGF were generated, and different concentrations of EGF and KGF were tested. EGF did not change any growth characteristics of the cells, with the exception of the speed of growth. Best growth was achieved with a physiologic EGF concentration of 0.15-1.5 ng/ml and a KGF concentration of 15 ng/ml. Finally, we cocultured oropharyngeal keratinocytes and their autologous fibroblasts in a three-dimensional matrix using Matrigeltrade mark. Oropharyngeal keratinocytes grown in coculture formed larger colonies than keratinocytes grown without fibroblasts. In conclusion, we were able to optimize the supplement of EGF and KGF in standard medium for the long-term culture of primary oropharyngeal keratinocytes. The use of Matrigel as a scaffold for three-dimensional cocultures of oropharyngeal keratinocytes and fibroblasts might signify a step forward in the development of a transplantable mucosa construct.

Cytolysin-dependent evasion of lysosomal killing

Local host defenses limit proliferation and systemic spread of pathogenic bacteria from sites of mucosal colonization. For pathogens such as streptococci that fail to grow intracellularly, internalization and killing by epithelial cells contribute to the control of bacterial growth and dissemination. Here, we show that group A Streptococcus (GAS), the agent of streptococcal sore throat and invasive soft tissue infections, evades internalization and intracellular killing by pharyngeal epithelial cells. Production of the cholesterol-binding cytotoxin streptolysin O (SLO) prevented internalization of GAS into lysosomes. In striking contrast, GAS rendered defective in production of SLO were internalized directly or rapidly transported into lysosomes, where they were killed by a pH-dependent mechanism. Because SLO is the prototype of cholesterol-dependent cytolysins produced by many Gram-positive bacteria, cytolysin-mediated evasion of lysosomal killing may be a general mechanism to protect such pathogens from clearance by host epithelial cells.

Nitric oxide formation in the oropharyngeal tract: possible influence of cigarette smoking

Cigarette smoking reduces the level of nitric oxide (NO) in exhaled air by an unknown mechanism. The view that part of the effect of cigarette smoking on NO production should occur in the oropharyngeal tract is supported by several studies. We have therefore compared smokers and non-smokers regarding non-enzymatic formation of NO from nitrite in the oral cavity since this is a primary candidate target for cigarette smoke. We have also looked at NO synthase-dependent NO formation in the mucosa of the oropharyngeal tract as an alternative target for the inhibitory effect induced by cigarette smoke. Smokers exhaled 67% lower levels of NO than controls (p<0.01, n=15 each group). We could not detect any significant difference in salivary nitrite, nitrate or ascorbate between smokers and non-smokers. Mouthwash with the antibacterial agent chlorhexidine reduced salivary nitrite (-65%) and exhaled NO levels (-10%) similarly in the two groups. Immunohistochemical techniques revealed dense expression of inducible (but not endothelial or neuronal) NO synthase in the squamous epithelium of non-inflamed tonsillar and gingival tissue biopsies. In the same biopsies, significant Ca2+ -independent citrulline-forming activity was detected. We found no difference between smoking and non-smoking subjects regarding NO-synthase expression and in vitro activity. In another group of non-smoking subjects (n=10), spraying the oropharyngeal tract with the NO-synthase inhibitor NG-monomethyl-L-arginine (250 mg) significantly reduced exhaled NO levels for at least 30 min (-18%, p<0.01). Our data suggest that cigarette smoking does not affect non-enzymatic NO formation from nitrite in saliva. However, NO is also formed by inducible NO synthase in the squamous epithelium of the normal oropharyngeal tract. We suggest that cigarette smoking may down-regulate enzymatic NO formation in the oropharyngeal compartment as well as in the bronchial compartment.

Expression of Proteolytic Enzymes in Head and Neck Cancer–Associated Fibroblasts

OBJECTIVE

To elucidate tumor-stromal interactions during tumor invasion by assessing the expression of proteolytic enzymes by carcinoma-associated fibroblasts (CAFs) in vivo using complementary DNA (cDNA) array analysis.

METHODS

Tumor-associated stroma was isolated from tumor and adjacent mucosal specimens of the same patient by laser capture microdissection, and the messenger RNA (mRNA) was assessed by cDNA microarray specific for proteolytic enzymes and their inhibitors. Protein overexpression was then analyzed by immunoblotting of primary fibroblast isolates derived from skin, mucosa, and tumor specimens.

RESULTS

Array analysis of 4 tumor and 4 adjacent mucosal samples demonstrated significant (2.6-fold) overexpression of membrane type 1 matrix metalloproteinase (MT1-MMP) but not of serine proteases or other matrix metalloproteinases. Analysis of normal dermal fibroblasts, normal mucosal fibroblasts, and CAFs similarly demonstrated up-regulation of MT1-MMP.

CONCLUSIONS

These results suggest that MT1-MMP mRNA is specifically up-regulated in CAFs in vivo whereas MT1-MMP protein is specifically up-regulated in CAFs in vitro. Known to induce tumor cell invasion when expressed in tumor cells, CAF expression of MT1-MMP may be important in the stromal response to tumor cells that characterizes the desmoplastic reaction.

Efficiency of adenovirus-mediated gene transfer to oropharyngeal epithelial cells correlates with cellular differentiation and human coxsackie and adenovirus receptor expression

Adenovirus-mediated gene transfer is a novel treatment strategy for head and neck squamous cell carcinoma (HNSCC) that may improve the unacceptable morbidity and mortality associated with conventional treatment. Efficient adenoviral (AdV) infection largely depends on cellular expression of the human coxsackie and adenovirus receptor (hCAR); however, the relatively recent identification of this receptor precludes a comprehensive description of its tissue distribution. We have created tissue culture model systems that approximate the differentiation and three-dimensional structure of stratified squamous epithelium characteristic of head and neck mucosa. Using these systems, we have found that expression of hCAR in native and modeled normal oropharyngeal epithelium decreased as cells differentiated with the most superficial and differentiated cells expressing no detectable hCAR. In contrast, modeled stratified HNSCC cells, which did not differentiate morphologically and did not express cytokeratin markers of differentiation, had equivalent expression of hCAR in superficial and basal layers. The expression of hCAR in our models correlated not only with the undifferentiated state, but also with efficiency of AdV infection. Despite expression of hCAR in underlying basal and suprabasal cells, topical application of AdV to normal modeled epithelium resulted in inefficient transduction of the most superficial cell layer without any infection of underlying cells. These data suggest that in normal epithelium the overlying squamous cells act as a barrier preventing infection of underlying cells that would otherwise be easily infected. In modeled stratified HNSCC, transduction was much more efficient and occurred up to four cell layers deep, suggesting that unlike normal superficial epithelial cells, the superficial cells of stratified HNSCC do not act as an effective barrier to adenoviral infection. The distribution of hCAR in native tissue and the enhanced susceptibility of undifferentiated oropharyngeal epithelial cells, including undifferentiated cancer cells, to AdV infection has important implications for the development of AdV-based targeting strategies for the treatment of head and neck cancer or premalignancies.

Attachment of Moraxella catarrhalis occurs to the positively charged domains of pharyngeal epithelial cells

Attachment of bacteria to host cells is the initial step in the pathogenesis of infection. Several factors, such as hydrophobicity, surface electric charge, and van der Waals force, are considered to be responsible for the attachment step. However, it is not clear why bacteria and epithelial cells, both of which possess a negative surface charge, do not repel one another. In the present study, we used Moraxella catarrhalis and pharyngeal epithelial cells to study the surface charges of structures involved in the attachment. By atomic force microscopy (AFM) equipped with surface potential spectroscopy, it was found that the cell surface microplicae have a positive charge of 30.1+/-3.6 mV (mean+/-SE). The depressions between the microplicae have a negative surface charge of 43.5+/-4.0 mV. Using cationic ferritin and electron microscopy (EM) we confirmed that the depressions between the microplicae have a negative charge. By AFM and by using cationic ferritin with EM, it was found that the net surface charge of the bacterial cells is negative. By both AFM and EM, it was found that the bacterial cells attach to the microplicae of the pharyngeal epithelial cell. Our work confirmed the general belief that both kinds of cells do have a net negative charge. We conclude that there are positively and negatively charged domains on the surface of human pharyngeal epithelial cells. M. catarrhalis evidently attaches to the positively charged domain (i.e. microplicae) of pharyngeal epithelial cells.

Epstein-Barr virus (EBV) in infectious mononucleosis: detection of the virus in tonsillar B lymphocytes but not in desquamated oropharyngeal epithelial cells

AIMS

Despite its well established tropism for B cells, the nature of the cellular compartment(s) mediating primary and persistent Epstein-Barr virus (EBV) infection is still a matter of controversy. In view of the association of EBV with several lymphoid and epithelial malignancies, resolution of this issue is important.

METHODS

Desquamated oropharyngeal epithelial cells from 10 patients with acute infectious mononucleosis and from seven chronic virus carriers were studied for evidence of EBV infection using in situ hybridisation for the detection of the small EBV encoded RNAs (EBERs) and of the viral genome. In addition, immunocytochemistry was used to detect the BZLF1 transactivator protein of EBV.

RESULTS

There was no evidence of latent or replicative EBV infection in oropharyngeal epithelial cells in any of the samples. In contrast, EBV infected B cells were readily identified in a tonsil from a patient with infectious mononucleosis.

CONCLUSIONS

The results suggest that oropharyngeal epithelial cells are not a major site of EBV infection and provide further support for the notion that B cells mediate primary and persistent EBV infection.

[Histochemical study with lectins submucous glands of the hamster's tongue]

A histochemical study, with lectins, in oropharyngeal cavity of 5 Syrian golden Hamsters (Mesocricetus auratus) was performed in order to know the tongue submucous glands characteristics. Results showed a strong reactivity to HPA lectin for secretions of submucous glands of the Hamster's tongue and a slight reactivity to N-WGA and to WGA lectins.

M cells at locations outside the gut

Lymphoid tissue associated with mucosal membranes is found not only along the gastrointestinal tract, but also in the tonsils, the upper and lower airways, and the conjunctiva of the eye. The epithelia overlying this mucosa-associated lymphoid tissue (MALT) contain membranous (M) cells which transport antigenic matter across the mucosal membrane to initiate immune responses. Although the morphology and function of intestinal M cells have been thoroughly studied, relatively little is known about the presence and properties of M cells in MALT outside the gut. The available data on ultrastructure, histochemistry, and antigen sampling function of the epithelia in tonsils, nasal-, larynx-, bronchus-, and conjunctiva-associated lymphoid tissue are reviewed and critically discussed. It is concluded that, in principle, the concepts of mucosal immune protection can be applied to these sites of MALT. However, it is questionable whether a separate cell type similar to intestinal M cells exists and performs antigen sampling in the different MALT epithelia. Further studies combining functional and morphological techniques are essential to understand the initiation of immune reaction at the mucosal membranes.

Antiadhesive effects of xylitol on otopathogenic bacteria

The exposure of either epithelial cells or pneumococci or both to 5% xylitol reduced the adherence of pneumococci. Exposure of epithelial cells or bacteria alone to xylitol did not reduce the adherence of Haemophilus influenzae, although the exposure of both cells and bacteria to xylitol reduced the adherence significantly. The adherence of Moraxella catarrhalis remained low irrespective of the exposure.

[Cultivation of human keratinocytes of mucous membranes of the upper aerodigestive tract]

BACKGROUND

Cultivation of benign epithelial cells under standardized conditions is of major interest in many fields of clinical and basic research. A modified fast and simple method for isolation, growth and passage of epidermal cells has been developed with consideration given to the complex environment of the upper aerodigestive tract.

METHODS

Normal human mucosa of the upper aerodigestive tract was taken from 15 patients (4-73 years) during diagnostic and therapeutic operations. The epithelium could be separated easily from the mucosa after incubation the biopsies in disease over night. Subsequently, keratinocytes were isolated enzymatically by dissociation of epidermal sheets in trypsin, resulting a suspension of highly proliferating keratinocytes without contaminating fibroblasts (2 x 10(6) keratinocytes/biopsy). The cells were washed several times in fresh fetal calf serum before they were plated in untreated culture flasks. The keratinocytes were cultivated in serum-free medium supplemented with epidermal growth factor, bovine pituitary extract, amphotericin B, and penicillin/ streptomycin.

RESULTS

An average plating efficiency of 60% in primary cultures and 85% in subcultures was obtained. Passaging was possible every 10-13 days when keratinocytes reached sufficient confluency. The cells could be subcultured up to eight times (lifespan of 120 days), and exhibited the typical epithelial morphology during cultivation.

CONCLUSION

Because of the modified pretreatment of the keratinocytes before plating, this culturing protocol for keratinocytes derived from the upper aerodigestive tract enables easy and fast cultivation of keratinocytes, further simplifying currently available methods.

Moraxella (Branhamella) catarrhalis adherence to human bronchial and oropharyngeal cells: the role of adherence in lower respiratory tract infections

To study the role of Moraxella (subgenus Branhamella) catarrhalis (B. catarrhalis) adherence to airway cells in lower respiratory tract infections, the in vitro attachments of B. catarrhalis to upper airway (oropharyngeal) and lower airway (bronchial) epithelial cells were compared. The adherence of 4 strains (1 nonfimbriated and 3 fimbriated) of B. catarrhalis to respiratory tract epithelial cells collected from 11 patients with chronic pulmonary disease (CPD) and 11 healthy individuals was evaluated. Both the fimbriated and nonfimbriated strains showed increased attachment to oropharyngeal cells in the CPD patients (mean +/- SEM; 25.0 +/- 3.2/cell; P < 0.01) when compared to the control subjects (12.1 +/- 1.1/cell). On the average, the attachment to bronchial cells was 6.1 to 13.6 times greater per surface area (bacteria/micron2) than the attachment to oropharyngeal cells. The fimbriated strains tended to adhere in higher numbers to bronchial cells (19.0 +/- 1.8/cell) than the nonfimbriated strain (8.7 +/- 1.2/cell), although there was no difference between the CPD and control groups. In conclusion, the attachment of B. catarrhalis to oropharyngeal cells may be an enhancing factor for colonization in the upper respiratory tract in patients with CPD, and elevated adherence of the bacteria to bronchial cells may suggest pathogenic importance when mucociliary function is impaired.

Contribution of the major and minor subunits to fimbria-mediated adherence of Haemophilus influenzae to human epithelial cells and erythrocytes

Fimbriae are colonization factors of the human pathogen Haemophilus influenzae in that they mediate bacterial adherence to human eukaryotic cells. The contribution of the major (HifA) and putative minor (HifD and HifE) subunits of H. influenzae fimbriae to fimbria-specific adherence was studied by using mutants that were inactivated in distinct fimbrial genes. Both the major and minor subunits were required for adherence of H. influenzae to oropharyngeal epithelial cells and human erythrocytes carrying the AnWj antigen. Cloning of defined H. influenzae fimbrial genes in an Escherichia coli strain with type 1 fimbriae yielded recombinants expressing high amounts of HifA-containing H. influenzae fimbriae either with or without coexpression of both H. influenzae minor subunits. Both clones exhibited the specific adherence properties of H. influenzae fimbriae, implying that the minor H. influenzae subunits are dispensable for adherence and that the adhesive domain resides in the major subunit, HifA. In H. influenzae itself, the minor subunits probably affect adherence by raising the number of fimbriae above the minimal level required to establish adherence.

Differential binding of Haemophilus influenzae to human tissues by fimbriae

The hypothesis was investigated that tissue tropism of Haemophilus influenzae during colonisation and infection is associated with the ability of fimbriate bacteria to bind to the organs and cell types involved. H. influenzae type b with fimbriae (strain 770235f+) bound to several cell types, including ciliated columnar epithelial cells, pneumocytes, ependymal cells, glial cells, connective tissue fibroblasts, synovial cells, antigen-presenting cells, lymphocytes, erythrocytes and endothelial cells. Binding of H. influenzae to kidney, liver and conjunctiva cells was poor. Fimbriae-specific monoclonal antibody (MAb 6HE8) inhibited this binding. Some binding to endothelial cells and macrophages was also observed with non-fimbriate strains. This binding was not inhibited by MAb 6HE8. We conclude that in-vitro binding of fimbriate H. influenzae is mainly to those tissues and cells where H. influenzae is found during colonisation and infection. The data suggest that a shift to the non-fimbriate form is required for bacteria in the bloodstream to escape clearance mechanisms mediated by blood cells.

Haemophilus influenzae causing conjunctivitis in day-care children

The role of Haemophilus influenzae in acute purulent conjunctivitis was studied during an outbreak among children in day care. Five day-care centers contributed 20 cases and 35 controls. All the children were subjected to culture of the nasopharynx and the eyes. H. influenzae was carried in the nasopharynx of 53% of the children (range between day care centers, 20 to 91%). Of the 20 children with acute conjunctivitis 8 had eye cultures positive for H. influenzae, 2 had Moraxella and the remaining were culture-negative. Ten colonies of H. influenzae were isolated from each positive culture and identified by capsular type, biotype and multi-locus enzyme electrophoresis. All but one of the isolates were nonencapsulated. They belonged to 4 biotypes and 8 electrophoretic types. The same strain was recovered from the eyes and nasopharynx of the symptomatic children, suggesting that the H. influenzae in the eyes originated from the nasopharynx. There was no evidence for spread of the same H. influenzae strains between day-care centers. Even within each center the Haemophilus strains recovered from the eyes varied among the symptomatic children. The in vitro capacity to attach to oropharyngeal epithelial cells was not increased among the H. influenzae recovered from the eyes. The results question if the majority of conjunctivitis cases were caused by H. influenzae and suggested that eyes were colonized with the nasopharyngeal carrier strain rather than infected by an isolate with special virulence for the eye.

Interaction of Haemophilus influenzae with human erythrocytes and oropharyngeal epithelial cells is mediated by a common fimbrial epitope

The role of fimbriae in the adherence of Haemophilus influenzae to oropharyngeal epithelial cells and the hemagglutination (HA) of human Anton-positive erythrocytes was examined. HA of bacteria was lost after shearing. Fimbriae purified from the extracellular fluid caused HA and bound to oropharyngeal epithelial cells, as analyzed with immunoperoxidase staining, in a way which was similar to the adherence of bacteria to these cells: binding was over the entire surface of the cells and showed cell-to-cell variation. The specific role of fimbriae in HA and adherence was further examined by inhibition experiments with monoclonal antibodies elicited against the isolated fimbriae. These monoclonal antibodies bound along the entire length of the fimbriae, as seen by immunogold electron microscopy. The monoclonal antibodies and their Fab fragments inhibited HA (reduction in titer from 1:512 to 1:128 and 1:64, respectively) and inhibited the adherence of the homologous H. influenzae strain and of three of eight heterologous H. influenzae strains to oropharyngeal epithelial cells. These results indicate that fimbriae are involved in adherence and HA and that the binding site for the monoclonal antibodies on the fimbriae is not common on all strains.

The relationship between adherence of Pseudomonas aeruginosa to upper respiratory cells in vitro and susceptibility to colonization in vivo

The relationship between adherence of Pseudomonas aeruginosa to buccal cells in vitro and susceptibility of the oropharynx to colonization by P. aeruginosa in vivo was examined in rats subjected to food and water deprivation. After food and water deprivation for 3 days, buccal cell adherence of P. aeruginosa was significantly greater than the control group values, and all treatment animals inoculated intraorally with P. aeruginosa at that time became colonized. These changes in cellular adherence in vitro and susceptibility to colonization persisted through the fourth day of deprivation and the first day of refeeding, and no treatment animals inoculated with P. aeruginosa at that time became colonized. Following renal infarction, buccal cell adherence of P. aeruginosa was increased within 24 hr; the magnitude and duration of this increase were related to the extent of renal infarction. Nearly all animals (34 of 36) inoculated intraorally with P. aeruginosa at a time when their buccal cell adherence values in vitro were increased above control values became colonized with the organism. These data suggest a strong relationship between epithelial cell binding of gram-negative bacilli in vitro and susceptibility to colonization with these organisms. The mechanisms by which respiratory epithelial cell adherence of P. aeruginosa is increased remain speculative.

Evaluation of methylene blue and squamous epithelial cells as oropharyngeal markers: a means of identifying oropharyngeal contamination during transtracheal aspiration

The usefulness of 1% methylene blue (MB) and squamous epithelial cells as oropharyngeal markers in transtracheal aspiration was prospectively evaluated. In vitro studies showed that failure to detect MB by spectrophotometry ruled out contamination by greater than 0.05 microliters of oropharyngeal secretions and that visual inspection was almost as sensitive as spectrophotometry. Even minute contamination could be ruled out if greater than 5 x 10(4) organisms were found by culture of Gram-stained smear in a specimen that was MB-negative by spectrophotometry. In specimens of transtracheal aspirate obtained from 10 bronchitic patients, quantitative bacteriology ruled out even minute contamination in nine. Cytologic-morphometric examination revealed that 70% of both sterile and colonized specimens of transtracheal aspirate contained squamous epithelial cells that were indistinguishable, except by electron microscopy, from buccal mucosal cells. MB is a useful marker for identification of oropharyngeal contamination during transtracheal aspiration, and traditional cytologic screening is misleading in conditions associated with tracheobronchial squamous metaplasia.

Pneumococcal adherence to human epithelial cells

Evidence is presented that pneumococci adhere poorly to oropharyngeal cells in vitro and that the capsule may interfere with adherence. A brief survey indicated that pneumococci may also adhere poorly in vivo.