Inhibition of Mycoplasma gallisepticum growth and attachment to chick tracheal rings by antibodies to a 64-kilodalton membrane protein of M. gallisepticum

A Mycoplasma gallisepticum (MG) strain R protein of 64 kilodaltons (p64) was partially digested from the surface of the bacterium by trypsin. Monospecific polyclonal anti-p64 IgG inhibited attachment of MG to chick tracheal rings by as much as 69%. However, trypsin treatment of viable MG cells did not reduce attachment to tracheal rings or hemagglutination titer. Anti-p64 IgG inhibited growth of MG strain R in broth and on solid media, inhibited the uptake of radiolabeled thymidine, but did not inhibit hemagglutination. Anti-p64 IgG inhibited growth of eight MG strains on solid medium. The degree of growth inhibition varied widely depending on the strain and correlated positively with the reported virulence of the MG strains with one exception (A5969). An IgG monoclonal antibody to p64 (MyG 001) inhibited growth of MG strain R on solid and in broth media. The strong attachment-inhibition activity of anti-p64 IgG may result from its growth-inhibiting activity. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of MG strains suggested that p64 is expressed in higher amounts in vitro in virulent strains (R, S6) than in strains of low virulence (F, M876, K503, K703, K730). P64 should be used to immunize chickens to determine if it can stimulate a growth and attachment-inhibiting response in the respiratory tract.

Streptococci and Pasteurella spp. associated with disease of the equine lower respiratory tract

The likelihood of finding evidence of inflammation in 551 tracheal washes collected endoscopically from 278 Thoroughbred racehorses increased with the number of bacterial colony forming units (cfu) per ml of wash (P < 0.001). The aerobic bacteria Streptococcus zooepidemicus, Pasteurella/Actinobacillus-like species and Streptococcus pneumoniae were significantly associated with lower airway inflammation whereas coagulase-negative Staphylococcus spp., alpha-haemolytic Streptococcus spp., Acinetobacter spp., Bacillus spp., Escherichia coli, Pseudomonas aeruginosa, non-haemolytic Streptococcus spp. and Enterobacteriaceae were not; Bordetella bronchiseptica was not isolated. Lower airway inflammation was particularly associated with bacteria in horses < or = 3 years of age. S. zooepidemicus, S. pneumoniae and Pasteurella/Actinobacillus-like species were isolated from 167 of 551 washes, either alone or in combination.

Detection of Mycoplasma gallisepticum infection in field samples using a species-specific DNA probe

Species-specific DNA probes for Mycoplasma gallisepticum (MG) were compared with serologic and isolation procedures as a routine diagnostic tool on field specimens acquired from chicken flocks experiencing egg-production losses and suspected of MG infection. The MG DNA probe clearly identified MG directly from tracheal specimens within 2 days, unlike the 7 to 10 days required for culture procedures. Cross-reaction of MG with M. synoviae continues to be a stumbling block in the serum plate agglutination test.

Protective immune response to Mycoplasma gallisepticum demonstrated in respiratory-tract washings from M. gallisepticum-infected chickens

Chickens inoculated with Mycoplasma gallisepticum (MG) produced IgA, IgM, and IgG detectable in washings from the upper respiratory tract (URTW; nasal sinuses and turbinates) and lower respiratory tract (LRTW; trachea, lungs, and air sacs). URTW and LRTW from infected chickens had significant protective effects in a MG-inoculated tracheal-ring-organ-culture system. Protective effects in vitro correlated positively with total MG-specific immunoglobulin titer, but not IgA titer, as determined by enzyme-linked immunosorbent assay. URTW and LRTW from infected chickens inhibited attachment of MG to tracheal-ring-organ cultures in a dose-dependent manner. This suggests that chickens produce a protective immune response to MG that locates in the respiratory tract and that attachment inhibition may be responsible for this protective effect.

A novel adherence assay for Bordetella pertussis using tracheal organ cultures

In a novel adherence model using tracheal rings removed from Papio anubis, we have demonstrated a functional role for the fimbriae of Bordetella pertussis. When compared to wild-type strains, B. pertussis mutants specifically deficient in fimbriae adhered less well to the tracheal rings but better to Vero (Green monkey kidney) cells. In contrast, mutants deficient in filamentous haemagglutinin (FHA) production had reduced adherence to both Vero cells and the tracheal rings. These observations indicate that the fimbriae of B. pertussis, like those of many other bacterial pathogens, may play an important role in the initial stages of colonisation.

Prevalence of mycoplasmal and ureaplasmal recovery from tracheobronchial lavages and of mycoplasmal recovery from pharyngeal swab specimens in cats with or without pulmonary disease

The prevalence of mycoplasmal and ureaplasmal recovery from tracheobronchial lavage specimens and prevalence of mycoplasmal recovery from pharyngeal swab specimens from cats with (28) or without (18) pulmonary disease were determined. Mycoplasmas were recovered from tracheobronchial lavage specimens in 21% of cats with pulmonary disease, but in no cats without pulmonary disease; this difference is significant (P = 0.04). Mycoplasmal recovery from tracheobronchial lavage specimens was not significantly associated with concurrent Pasteurella spp isolation, septic inflammation, or bronchitis. Ureaplasmas were only isolated from a tracheobronchial lavage specimen in 1 cat with pulmonary disease and in no cats without pulmonary disease. Similar mycoplasmal recovery rates were found for pharyngeal swab specimens from cats with (39%) or without (35%) pulmonary disease. Seemingly, mycoplasmas are part of the normal pharyngeal flora in approximately a third of the feline population, but mycoplasmas are not normal inhabitants of the lower respiratory tract in cats. It is unknown whether mycoplasmas isolated from tracheobronchial lavage specimens in cats with pulmonary disease are primary pathogens or opportunistic invaders. Seemingly, ureaplasmas are seldom associated with pulmonary disease in cats, and are not normal inhabitants of the trachea and bronchi of cats.

Topical antimicrobial prophylaxis of nosocomial pneumonia in mechanically ventilated patients. Microbiological observations

Generally, reduction of colonization and infection with potentially pathogenic microorganisms in intensive care units (ICU) is attempted by a combination of antimicrobial agents administered topically in the digestive tract and systematically. We tested the efficacy of topical antimicrobial prophylaxis of the oropharynx and stomach administered in combination with sucralfate without systemic prophylaxis in 25 mechanically ventilated ICU patients. The regimen successfully reduced colonization with potentially pathogenic microorganisms in the oropharynx and trachea without modifying the intestinal flora. However, colonization and infections with gram-positive cocci and gram-negative rods other than Enterobacteriaceae and Pseudomonadaceae and resistant to one or both the antimicrobial agents used were observed.

Epidemiological impact of prolonged systematic use of topical SDD on bacterial colonization of the tracheobronchial tree and antibiotic resistance. A three year study

OBJECTIVE

to evaluate the effect of the prolonged systematic use of topical SDD (tobramycin 80 mg, polymyxin E 100 mg, amphotericin B 500 mg) on ICU ecology as expressed by changes in tracheal colonization and bacterial resistances.

DESIGN

Prospective microbiological survey.

SETTING

Polyvalent ICU of a 2000 beds general hospital.

PATIENTS

Data concerning bacterial strains isolated from the tracheo-bronchial aspirates of all the patients admitted to a polyvalent ICU over 3 consecutive periods of 12 months ('88, '89, '90) were prospectively entered in a database and subsequently analyzed. During a 3-year period 502 patients required artificial ventilation for more than 72 h and 332 of them ('89 and '90) were treated with SDD. All samples collected within 72 h from ICU admission were excluded as well as duplicate samples from the same patients.

INTERVENTION

All the patients admitted to the ICU in '89 and '90 and submitted to artificial ventilation for at least 24 h were routinely treated with topical SDD without i.v. antibiotic prophylaxis; in '88 SDD was not employed.

MEASUREMENTS AND RESULTS

Criteria for collecting sputum samples and microbiological procedures remained unchanged throughout the study-time. Positive sputum were significantly less in '89 (80.8% versus 92.3% p < 0.001) and this was due to a very sharp decrease in the isolation of Gram-negative strains from 43-28% (-64% p < 0.0001) involving both: Enterobacteriaceae (-45%) and Pseudomonaceae (-77%). In 1990; however, a new increase in Gram negative was observed, although the overall amount of Gram-negative was still 49% lower in '90 if compared to '88 (p < 0.0001). A dramatic increase in Pseudomonas isolation was the only factor responsible for the "rebound" observed. An increasing percentage of Pseudomonas developed a resistance towards tobramycin and only 45% of Pseudomonas strains turned out to be sensible to tobramycin in '90 against 79% in '88. A similar trend was registered for all aminoglycosides with the exception of amikacin. Gram-positive colonizations tended to increase (+63%) (p < 0.0001) and this was mainly due to Coagulase negative Staphylococci (+290% p < 0.0001) and S. pneumoniae, whereas S. aureus isolations decreased (-18%) but not significantly.

CONCLUSIONS

Our data suggest that the prolonged use of SDD is associated with dramatic changes in ICU ecology: the incidence of Gram negative colonization is significantly diminished by SDD whereas Gram positive tend to increase. Pseudomonas developed an increasing resistance towards tobramycin one of the components of the SDD formula we used.

Selective decontamination of the digestive tract (SDD) does not prevent the formation of microbial biofilms on endotracheal tubes

The purpose of selective decontamination of the digestive tract (SDD) is to eradicate potentially disease-producing micro-organisms from the oropharynx and gastro-intestinal tract of intensive care unit (ICU) patients, thereby reducing the incidence of nosocomial sepsis, particularly pneumonia. Microbial biofilms form on endotracheal (ET) tubes even when SDD is being administered and may represent a persistent focus for infection. The aim of this investigation was to determine the susceptibilities of organisms adherent to ET tubes to SDD antibiotics (amphotericin B, tobramycin and polymyxin) and to measure the concentrations of these agents in the tracheal aspirates of 11 patients who were being mechanically ventilated. Following extubation, a section was cut from the tip of each ET tube and any adherent microorganisms subsequently isolated were identified and their MICs determined. Samples of tracheal aspirate were obtained three hours after administration of the SDD regimen and the concentrations of the constituent antimicrobials were measured. Enterobacteriaceae were not recovered from any of the tubes but six strains of Staphylococcus aureus, three Pseudomonas spp., three enterococci and four yeasts were isolated. Wide variations in the concentrations of all antibiotics were observed and in many cases they were below the MICs for the organisms isolated. In particular, tobramycin concentrations were uniformly less than the median MIC for the S. aureus isolates and this may account for the predominance of Gram-positive bacteria adherent to the ET tubes. Microbial biofilms attached to these tubes may have a role in the pathogenesis of nosocomial pneumonia in ICU patients.

Human papillomavirus infection in papillomas and nondiseased respiratory sites of patients with recurrent respiratory papillomatosis using the polymerase chain reaction

We examined human papillomavirus (HPV) infection in biopsy specimens and cellular scrapes that were taken from respiratory papillomas and six nondiseased sites from the respiratory tract of seven patients. Human papillomavirus was detected by polymerase chain reaction amplification, followed by DNA hybridization with probes for specific HPV types. All papillomas (100.0%, n = 5) were positive only for HPV type 6 or 11. In the nondiseased site specimens, 61.3% (19/31) of the specimens were positive, again only for HPV type 6 or 11. Among the nondiseased site specimens from the cervical trachea, intrathoracic trachea, and bronchus, 80% to 100% were HPV positive compared with only 25% to 50% of HPV infection detected in the nasopharynx, posterior tonsillar pillar, and aryepiglottic fold. These results support the tenet that HPV infection is present in clinically normal respiratory tract tissue and that the reservoir site of reinfection is more commonly in the lower airway. However, patients with upper-airway involvement were more likely to be diagnosed as having severe disease.

Aspergillosis granuloma in the mediastinum of a non-immunocompromised horse

A National Show Horse with a mediastinal granuloma was presented with clinical signs which included fever, nasal discharge and cough. The mediastinal mass was identified radiographically and ultrasonographically. A presumptive diagnosis of aspergillosis was made following isolation of Aspergillus spp. from both transtracheal aspirate and bronchoalveolar lavage fluid samples and agar gel immunodiffusion (AGID) identification of serum antibody to Aspergillus spp. The diagnosis was confirmed by histopathologic examination of the mediastinal mass obtained at necropsy examination.

Improved recovery of mycobacteria from respiratory secretions of patients with cystic fibrosis

Pulmonary colonization and infection of patients with cystic fibrosis by Mycobacterium spp. has recently been recognized as a potentially important clinical problem. However, frequent contamination of mycobacterial cultures by pseudomonads has hampered efforts to define the extent of this problem. This study was done to evaluate current techniques and to establish a more efficient method of recovering mycobacteria from respiratory secretions of patients with cystic fibrosis. Decontamination of respiratory specimens (n = 121) with 0.25% N-acetyl-L-cysteine and 1% sodium hydroxide (NALC-NaOH) was associated with a high rate of pseudomonas overgrowth for both Lowenstein-Jensen slants (74%) and BacTec vials supplemented with PANTA (polymyxin B [50 U/ml], amphotericin B [5 micrograms/ml], nalidixic acid [20 micrograms/ml], trimethoprim [5 micrograms/ml], azlocillin [10 micrograms/ml]) (36%). This overgrowth limited recovery of mycobacteria to only 64% (9 of 14) of specimens positive by smear for acid-fast bacilli (AFB). Decontamination of specimens (n = 441) with NALC-NaOH, followed by 5% oxalic acid treatment, resulted in contamination of only 5% of Lowenstein-Jensen slants and 3% of BacTec vials. AFB were recovered from all 90 AFB smear-positive specimens following the use of this decontamination technique. We recommend that respiratory secretions be decontaminated with NALC-NaOH and oxalic acid to decrease the incidence of Pseudomonas aeruginosa overgrowth.

Isolation and identification of mycoplasma strains from various species of wild rodents

Attempts were made to isolate mycoplasmas from respiratory and urogenital tracts of 35 apparently healthy wild rodents comprising 7 species under 4 genera. Mycoplasmas were isolated from nasal and oral cavities, tracheas, vaginas and penises of the wild rats: ricefield rats (Rattus argentiventer), roof rats (R. rattus) and Polynesian rats (R. exulans), but none was isolated from brown rats (R. norvegicus), house mice (Mus musculus), smithi's voles (Eothenomys smithi) and soft-furred field rats (Millardia meltada). These mycoplasma strains were identified as Mycoplasma pulmonis and M. arthritidis on the basis of their biological and serological properties.

[Ureaplasma urealyticum in tracheal aspirate of ventilated premature infants: report of 6 cases]

In the Netherlands, up till now no reports have appeared describing neonatal colonisation of mechanically ventilated preterm neonates with Ureaplasma urealyticum. The present, prospective study was designed to assess the incidence of U. ureaplasma infections in a group of preterm newborns with prolonged ventilatory support because of respiratory failure. In 1989 110 preterm newborns with hyaline membrane disease (HMD) were mechanically ventilated; 23 for more than 7 days because of pulmonary abnormalities. Six of them (26%) had positive cultures of endotracheal aspirate for U. urealyticum. Gestational age at birth ranged from 26 to 33 5/7 weeks, birth weight from 790 to 2545 gram. Other bacteria or viruses were not present. Although all patients with positive cultures for U. urealyticum were treated with erythromycin and U. urealyticum was eradicated, no clinical effect was seen. Five of the 6 patients (83%) with U. urealyticum developed bronchopulmonary dysplasia (BPD), 2 of them (33%) died. Of the 17 neonates without U. urealyticum 9 (53%) developed BPD, whereas one (6%) died. Differences were not significant (Chi 2 test/Fisher exact test). Also in the Netherlands U. urealyticum can be demonstrated in endotracheal aspirate of ventilated preterm newborns. The hypothesis, that early diagnosis and treatment of U. urealyticum in this group of patients might decrease the morbidity and mortality caused by HMD and BPD, needs further study.

Chronic lung disease of preterm infants in Finland is not associated with Ureaplasma urealyticum colonization

The occurrence of Ureaplasma urealyticum and Mycoplasma hominis in the airways and the association of these microorganisms with chronic lung disease was studied in preterm infants with a gestational age less than 30 weeks. Tracheal aspirates from 49 preterm infants were cultured; 14 (29%) infants were positive for U. urealyticum, and 1 (2%) was positive for M. hominis. Of the 16 patients who developed lung disease, 6 (38%) were positive for U. urealyticum, while the expected number of Ureaplasma-positive patients in this group, based on the overall incidence of Ureaplasma, was 4.6. On the other hand, 8 patients were positive for U. urealyticum but did not develop chronic lung disease, nor did samples taken from 10 patients with chronic lung disease show any Ureaplasma growth. From these data we conclude that colonization of the airways with U. urealyticum has no significant role in the development of chronic lung disease in preterm infants in the Finnish (Caucasian) population.

[Epidemic occurrences of multiresistant Acinetobacter baumannii strains in a neonatal intensive care unit]

In a period of nine months (May 1991 to January 1992), 39 infants were colonized with Acinetobacter baumannii in a paediatric intensive care unit. Colonization was observed mainly in premature infants, weighing between 680 g and 2,000 g, who were artificially ventilated. Shortly after birth, A. baumannii was isolated regularly from tracheal washings, and less frequently from other material, such as gastric juice, catheter tips, and umbilical swabs. In older children or adults, the bacteria were found only in very low frequency. In the intensive care unit, A. baumannii could be isolated from tap water, sinks, water traps of the ventilation devices, the inner wall of incubators, and from the hands of medical personnel. Patients strains of A. baumannii, and those isolated monitoring the intensive care unit had an identical biochemical profile and a similar pattern of antimicrobial resistance, as well as a similar reaction in other typing methods. Anti-infective measures are discussed.

Two types of bacteria adherent to bovine respiratory tract ciliated epithelium

Two hundred sixty tracheas were obtained from a Philadelphia abattoir under permit from the Department of Agriculture; the tracheas were excised from predominantly Holstein calves of both sexes that weighed approximately 250 kg. Tracheas were transported in normal saline to the laboratory at Thomas Jefferson University, Philadelphia, Pennsylvania. Evidence of bacteria adherent to the tracheal epithelium was found in specimens from 20/24 of these tracheas. The epithelium from each of five tracheas was placed in glutaraldehyde fixative for transmission electron microscopic examination. Epithelium from each of 12 other tracheas was placed in formaldehyde fixative for light microscopic examination. Microscopically, 13 of these 17 bovine tracheal epithelia were observed to contain bacteria located longitudinally parallel to and between cilia and microvilli of ciliated cells. Preparations of ciliary axonemes isolated from the epithelium of seven additional bovine tracheas also contained these bacteria in sections viewed by a transmission electron microscope. These bacteria had two different ultrastructural morphologies: filamentous with a trilaminar-structured cell wall and short with a thick, homogeneously stained cell wall beneath a regularly arrayed surface layer. The short bacillus had surface carbohydrates, including mannose, galactose, and N-acetylgalactosamine, identified by lectin binding. The filamentous bacillus was apparently externally deficient in these carbohydrates. Immunogold staining revealed that the filamentous bacillus was antigenically related to cilia-associated respiratory (CAR) bacillus, which has been identified in rabbit and rodent species. Significantly decreased numbers of cilia were obtained from tracheal epithelium heavily colonized by the filamentous bacilli, suggesting a pathologic change in ciliated cells.

Demonstration of Helicobacter pylori in tracheal secretions

A new gram-negative bacterium, Helicobacter pylori, has been found in gastric secretions. In view of an almost 9% incidence of unidentified gram-negative bacteria in aspiration pneumonia, the authors set out to prove that H pylori could be found in tracheal secretions. Eighteen sequential patients admitted to the intensive care unit who had endotracheal or nasogastric intubation for 24 hours or longer were studied. Of 20 sets of specimens from 18 patients. Helicobacter was recovered from 2(10%) of the endotracheal specimens. The authors conclude that H pylori can gain access to the endobronchial tree and therefore may contribute to the origin of pneumonia due to unidentified gram-negative bacteria.

Cilia-associated respiratory bacillus in wild rats in central Iowa

Twenty-eight wild rats were live-trapped in central Iowa (USA) to estimate the prevalence of the cilia-associated respiratory (CAR) bacillus. Both light and electron microscopy were used to look for the Gram-negative, filamentous bacterium among cilia in tracheal and lung tissue sections. The organism was observed in the trachea of 20 rats with chronic respiratory disease and in the trachea of three of eight normal rats. Therefore, the organism appears to be common among wild rats in central Iowa.

["Single-shot" antibiotic prophylaxis in thoracic surgery; reduction of the postoperative infection rate]

A prospective, controlled and randomised trial was started to detect the effectivity of a "single-shot" antibiotic prophylaxis in thoracic surgery using cefuroxime. Therefore 200 unselected patients, consecutively scheduled for major thoracic surgery except endoscopic procedures or mediastinoscopy were enrolled in this study and randomized into either the control group (no antibiotics perioperatively; n = 100) or the prophylaxis group (one dose of 1.5 g cefuroxime i.v. at induction of anaesthesia; n = 100). Clinical signs correlated with infection, radiological findings and the results of repeated microbiological examinations were recorded and a comparative statistical analysis was done. Compared to controls the prophylaxis group had fewer (not significant) infections of the wound, the pleural cavity and the urinary tract and fewer patients of this group showed "pronounced infiltration" in daily taken chest roentgenograms (significant), clinical signs for pneumonia and pathologic sputum findings, or new bacterial colonisation of sputum specimens on the first postoperative day, whereas bacteria, isolated from tracheal aspirates, immediately taken after intubation disappeared more often. Specimens of pleural fluid taken postoperatively were less often positive for bacteria. Fewer patients were treated with antibiotics in the postoperative course and the courses were shorter in the prophylaxis group compared to controls. Considering the risk factor "positive microbiological culture" in preoperative tracheal aspirates, patients of the prophylaxis group showed much more seldom new radiological "infiltration" (statistically highly significant) and, in addition, had lower white blood cell counts (significant) and lower mean maximal body temperatures. The results of our trial confirm the preventive effect of "single-shot" antibiotic prophylaxis in thoracic surgery against infections.

Polymerase chain reaction and a biotin-labeled DNA probe for detection of infectious bronchitis virus in chickens

Polymerase chain reaction (PCR) and a biotin-labeled DNA probe were used to amplify and detect the genome of infectious bronchitis virus (IBV) from tracheal swabs taken from chickens that were experimentally inoculated with the IBV Beaudette, Arkansas, and Gray strains. The viral genome was successfully detected by PCR and confirmed by dot-hybridization assay using a biotin-labeled DNA probe on days 1, 3, 9, and 14 after exposure. Direct electron microscopy (EM) analysis was used to compare the ability of the two tests to detect IBV from the same tracheal swab samples. The EM analysis did not detect IBV in four of eight necropsy groups that were positive using PCR and the biotin-labeled DNA probe. Although histopathological lesions were observed in the tracheas, no clinical signs or specific antibody response were observed in the birds. The virus was also detected in the allantoic fluid of embryonating chicken eggs that had been inoculated with field samples suspected to be IBV. The field samples were passed four to six times in embryonating eggs, and 10 of 17 samples were positive using PCR and the biotin-labeled probe.

A bactericidal monoclonal antibody specific for the lipooligosaccharide of Bordetella pertussis reduces colonization of the respiratory tract of mice after aerosol infection with B. pertussis

A mouse immunoglobulin G3 monoclonal antibody specific for the core oligosaccharide moiety of the lipooligosaccharide (LOS) of Bordetella pertussis has been shown to have complement-dependent bactericidal activity. This monoclonal antibody exhibits bactericidal activity against strains of B. pertussis that express the LOS A phenotype. In addition this monoclonal antibody was effective in reducing colonization by B. pertussis in both the lungs and tracheas of mice after aerosol infection.

Expression of protein F, the fibronectin-binding protein of Streptococcus pyogenes JRS4, in heterologous streptococcal and enterococcal strains promotes their adherence to respiratory epithelial cells

In a previous study we reported the identification of protein F, a fibronectin-binding protein that was essential to the ability of Streptococcus pyogenes JRS4 to adhere to respiratory epithelial cells (E. Hanski and M. Caparon, Proc. Natl. Acad. Sci. USA, 89:6172-6176, 1992). To further evaluate the role of protein F in the adherence of the group A streptococci, we screened other group A streptococcal strains, including six recent clinical isolates, and one strain of Enterococcus faecalis for their capacity to bind fibronectin and for the presence of the gene encoding protein F (prtF). Seven of eight group A streptococcal strains analyzed, including all recent clinical isolates, both bound fibronectin at high affinity and contained DNA sequences that hybridized with a prtF-specific probe. One group A streptococcal isolate and the strain of E. faecalis examined neither contained a prtF-related gene nor bound fibronectin. These two strains also could not efficiently adhere to respiratory epithelial cells. However, upon the introduction of the cloned prtF gene, both of these strains gained the capacity to bind fibronectin and to adhere to respiratory epithelial cells. These results suggest that protein F is an important adhesin, which may have a general role in the virulence of the group A streptococci.

Detection of enhanced neutrophil adhesion to parainfluenza-infected airway epithelial cells using a modified myeloperoxidase assay in a microtiter format

Despite growing evidence that respiratory virus infections precipitate episodes of airway obstruction and airway hyper-responsiveness in young children and in asthma, little information is available on the mechanisms by which virus infections alter the airway physiology. Airway inflammatory changes (including influx of inflammatory cells such as neutrophils) have been described during episodes of airway hyper-responsiveness in both animal models and human subjects. Neutrophil damage to several cell types has been shown to require adhesion as a primary step. In order to examine the potential interactions between virus-infected airway epithelial cells and neutrophils, we have studied the ability of neutrophils to adhere to virus-infected airway epithelial cell cultures. Neutrophil adherence was determined indirectly, using myeloperoxidase as a marker for adherent neutrophils in an assay system described here. Airway epithelial cell cultures (both primary human tracheal epithelial cells, and two permanent cell lines, A549 and BEAS-2B) were grown in 96-well tissue culture plates and infected with human parainfluenza virus type 2. Infected airway epithelial cell cultures supported significantly enhanced levels of neutrophil adherence (up to 50-75% of neutrophils added to the wells) compared to uninfected control cultures. Moreover, this adherence occurred in a virus dose-dependent fashion, with increasing levels of adherence noted at increasing viral multiplicities of infection. The assay system described allows the detection of small numbers of adherent neutrophils (as few as 1000 neutrophils) in a 96-well format.