Diagnosis of pneumococcal pneumonia by coagglutination and counterimmunoelectrophoresis of sputum samples

Type-specific enzyme immunoassay for detection of pneumococcal capsular polysaccharide antigens in nasopharyngeal specimens

We developed a new competitive EIA method for the demonstration of pneumococcal capsular polysaccharides from respiratory samples. The pediatric types 4, 6B, 9V, 14, 18C, 19F and 23F were selected for this study, because these capsular polysaccharides were included in the first heptavalent pneumococcal conjugate vaccines, which were used in the Finnish Otitis Media Vaccine Trial. Sensitivity of the EIA tests for purified polysaccharide antigens varied between 5 and 100 ng/ml, depending on the type. The assays performed well in 100 nasopharyngeal samples (NPS) samples processed through an enrichment culture, with an almost 100% sensitivity compared with routine culture. The method appeared type-specific, except that EIA for 6B capsule also detected 6A. The method is applicable for type-specific identification of pneumococcus in carriage studies.

Antigen and antibody assays in the aetiological diagnosis of respiratory infection in children

The diagnostic efficacy of two methods--demonstration of seroconversion in paired sera and detection of antigen in clinical specimens--was evaluated in 183 children with respiratory syncytial, parainfluenza or adenoviral, or pneumococcal respiratory tract infection. Viral infection was diagnosed in 46 (37%) of the 125 cases by antigen assay alone, in 36 (29%) by antibody assay alone and in 43 (34%) by both methods. In respiratory syncytial viral infections, antigen assays were more often positive than antibody assays; 80% of the cases were antigen positive and 63% solely antigen positive. In parainfluenza and adenoviral infections, antigen assays were not as useful; a positive result was seen in 59% and 44% of cases, respectively. Pneumococcal infection was diagnosed in 25 (30%) of the 84 cases by antigen assay alone, in 54 (64%) by antibody assay alone and in only 5 (6%) by both methods. Thus nearly all pneumococcal infections were diagnosed by only one method. The efficacy of antigen and antibody assay was clearly dependent on the age of the patients. In infants less than six months of age, nearly all (27 (90%)) of the 30 infections were diagnosed by antigen detection; 25 solely by antigen detection. In older patients, antigen and antibody assays supplemented each other. We conclude that antigen detection should be used as the primary method for the diagnosis of viral or pneumococcal respiratory tract infection. In infants, antigen detection is the only reliable method of microbial diagnosis. In addition, antigen detection is the method of rapid microbial diagnosis. In pneumococcal infections, the sensitivities of antigen detection methods are not sufficient; this is an important area for further research.

Aetiology of community-acquired pneumonia in children treated in hospital

Viral and bacterial antigen and antibody assays were prospectively applied to study the microbial aetiology of community-acquired pneumonia in 195 hospitalised children during a surveillance period of 12 months. A viral infection alone was indicated in 37 (19%), a bacterial infection alone in 30 (15%) and a mixed viral-bacterial infection in 32 (16%) patients. Thus, 46% of the 69 patients with viral infection and 52% of the 62 patients with bacterial infection had a mixed viral and bacterial aetiology. Respiratory syncytial virus (RSV) was identified in 52 patients and Streptococcus pneumoniae in 41 patients. The next common agents in order were non-classified Haemophilus influenzae (17 cases), adenoviruses (10 cases) and Chlamydia species (8 cases). The diagnosis of an RSV infection was based on detecting viral antigen in nasopharyngeal secretions in 79% of the cases. Pneumococcal infections were in most cases identified by antibody assays; in 39% they were indicated by demonstrating pneumococcal antigen in acute phase serum. An alveolar infiltrate was present in 53 (27%) and an interstitial infiltrate in 108 (55%) of the 195 patients. The remaining 34 patients had probable pneumonia. C-reactive protein (CRP), erythrocyte sedimentation rate and total white blood cell count were elevated in 25%, 40% and 36% of the patients, respectively. CRP was more often elevated in patients with bacterial infection alone than in those with viral or mixed viral-bacterial infections. No other correlation was seen between the radiological or laboratory findings and serologically identified viral, bacterial or mixed viral-bacterial infections.(ABSTRACT TRUNCATED AT 250 WORDS)

Pneumococcal finding in a sample from upper airways does not indicate pneumococcal infection of lower airways

The presence of pneumococcus (Pnc) by antigen detection and culture was examined in nasopharyngeal aspirates (NPA) of 315 children hospitalized with middle or lower respiratory tract infection. Pnc was found in NPA from 115 (37%) patients, being demonstrated by antigen detection alone in 34 (30%), by culture alone in 26 (23%) and by both methods in 55 (48%) of Pnc-positive samples. Pnc findings in NPA were most common, 45-46%, in patients aged 1-4 years. Serological evidence of Pnc infection, based either on detection of Pnc antigen in serum or urine, or on demonstration of an antibody response to these antigens, was present in 31 (27%) of the 115 patients with and in 28 (14%) of the 200 patients without Pnc in NPA samples. In the 48 patients positive for Pnc in NPA samples both by antigen detection and culture the isolated Pnc strains were serotyped. In 45 (94%) of these the type/group of Pnc was the same by both methods indicating that the specificity of the antigen detection tests, latex particle agglutination and counterimmunoelectrophoresis, was high. To evaluate the diagnostic significance of Pnc antigen detection and culture in NPA, sensitivity, specificity and likelihood ratios were calculated; serological evidence of Pnc aetiology was used as a reference. For both methods, sensitivity was poor, less than 0.3, but specificity was good, greater than 0.8. It is concluded that the finding of Pnc by culture or antigen detection in NPA is no indication of Pnc respiratory infection. On the other hand, Pnc etiology is unprobable, if Pnc is not present in NPA.(ABSTRACT TRUNCATED AT 250 WORDS)

Pneumococcal capsular antigen detection and pneumococcal serology in patients with community acquired pneumonia

BACKGROUND

Methods to determine the microbial cause of community acquired pneumonia include detection of pneumococcal antigen and measurement of pneumococcal capsular antibody response. Their usefulness compared with conventional microbiological techniques was investigated in patients with pneumonia, some of whom had been treated with antibiotics.

METHODS

Pneumococcal capsular antigen was detected by latex agglutination in sputum and the results compared prospectively with results of conventional microbiological techniques in 90 patients with community acquired pneumonia. Serum, urine, and pleural fluid samples were also tested for antigen. Serum pneumococcal capsular antibody titres were measured.

RESULTS

A diagnosis was established by conventional microbiological techniques in 53 patients, 30 of whom had pneumococcal pneumonia. The sensitivity of antigen detection in first day sputum specimens (n = 18) in those with pneumococcal pneumonia was 94%; antigen was present in 23 of the 27 patients who produced representative sputum on admission and during follow up. The specificity of antigen detection in sputum in patients with non-pneumococcal pneumonia and lung infarction was 87%. Antigen was present in 12 of 25 patients with pneumonia of unknown aetiology who produced representative sputum. Antigen was rarely detected in serum and urine, but was present in pleural fluid in three of four patients with pneumococcal pneumonia and in all four patients with pneumonia of unknown aetiology. Pneumococcal antigen remained detectable in patients treated with antibiotics. Pneumococcal capsular antibody detection was as specific (85%) as antigen detection, but had a lower sensitivity (50%).

CONCLUSION

Pneumococcal antigen detection in sputum or pleural fluid is of value in making a rapid diagnosis and provides an additional diagnostic result in patients with pneumococcal pneumonia, especially those receiving antibiotic treatment.

Respiratory tract colonization and incidence of secondary infection during hospital treatment of community-acquired pneumonia

In a prospective study of 245 patients with community-acquired pneumonia, the respiratory tract of 93 patients (38%) became colonized during hospitalization. Gram-negative rods and Candida spp. predominated, and in more than 75% of cases colonization occurred within 72 h after admission. Multivariate analysis showed that colonization was significantly associated with increasing age, presence of chronic disease, and with decreasing serum albumin and a respiratory rate of greater than 30/min on admission. Colonization was a negative prognostic factor, associated with a 14-fold higher mortality (10% vs. 0.7%), doubled length of hospital stay and a slower recovery. Seventeen patients developed a secondary infection. However, only two had lower respiratory tract infection, and one (0.4%) pneumonia verified by X-ray. The previously reported high risk of respiratory superinfection in this category of patient does not seem to apply today.

Nasopharyngeal culture in the pneumonia diagnosis

The diagnostic value of bacterial cultures from nasopharynx (NPH) was prospectively studied in 261 patients with community-acquired pneumonia requiring hospitalization. NPH culture results were compared with those of other diagnostic methods: Culture from blood and sputum, pneumococcal antigen detection, enzyme immuno assay (EIA) for detection of antibodies against pneumococcal hemolysin and in selected cases bronchoscopy. Pneumococcal pneumonia was diagnosed by these other methods in 121 patients. Streptococcus pneumoniae was detected in NPH in 33 of these patients (27%, or 36% if only cultures obtained before start of antibiotics are considered), but in only four of the other 140 patients. For other species the relevance of NPH culture was uncertain. Because of its simplicity and high specificity NPH culture can be a valuable supplement to other diagnostic methods, particularly when sputum samples are difficult to obtain.

Comparison of three methods for detection of pneumococcal antigen in sputum of patients with community-acquired pneumonia

In a prospective study of 249 patients with community-acquired pneumonia, three tests for the detection of pneumococcal antigen in sputum were compared: a coagglutination test for detecting capsular antigens (Cap-CoA), a sandwich enzyme immunoassay (PnC-EIA) and a coagglutination test (PnC-CoA), both the latter detecting the pneumococcal C-polysaccharide common to all pneumococcal types. Sixty-three patients had culture-positive pneumococcal pneumonia, 45 pneumonia caused by other bacteria and 141 pneumonia of viral or unknown etiology. The sensitivity of Cap-CoA (63%) and PnC-CoA (65%) was somewhat higher than that of PnC-EIA (49%), but not significantly so. The specificity was 96-98% for all three methods. Using PnC-CoA 66 patients with possible pneumococcal infection were detected, the diagnosis being verified by culture in 41. Using Cap-CoA 59 such patients were detected, the diagnosis being verified in 40, and using the PnC-EIA 47 such patients were detected, the diagnosis being verified in 31. Antigen was found almost as often in non-purulent as in purulent samples, and as often in washed as in non-washed purulent samples. However, antibiotic treatment before the sputum sample was obtained resulted in significantly lower sensitivity of both PnC-CoA and Cap-CoA. This study confirms the high sensitivity and specificity of methods for pneumococcal antigen detection in sputum. Since CoA is easier and quicker to perform, and cheaper than the EIA, either PnC-CoA or Cap-CoA would seem to be the technique of choice for detection of pneumococcal antigen, whereby all sputum samples, including non-purulent samples, can be used.

Rapid streptococcal antigen detection in experimental keratitis

We assessed the role of commercially available immunodiagnostic procedures in comparison to Gram stain and culture in experimental bacterial keratitis. Rabbit corneas were inoculated with Streptococcus pneumoniae, S. pyogenes, S. faecalis, or Haemophilus influenzae. Corneal scrapings were processed before and during antibacterial therapy using a coagglutination assay to detect pneumococcal capsular antigen (Phadebact Pneumococcus test) and an enzyme immunoassay to detect group A streptococcal cell-wall antigen (TestPack Strep A test). In untreated infected eyes, both immunoassays were highly specific and as sensitive as Gram stain for detection of the respective microorganisms. For S. pneumoniae keratitis, the sensitivity of coagglutination was 82% and Gram stain, 73%. For S. pyogenes keratitis, the sensitivity of enzyme immunoassay was 100% and Gram stain, 62%. Immunoassays and Gram stain were less sensitive than culture during antibacterial therapy. Successful clinical application of the coagglutination assay in a patient with pneumococcal keratitis permitted early use of specific cephalosporin treatment.

Demonstration of cross-reactions between pneumococci and alpha-streptococci using gold-labelled mono- and polyclonal antibodies and electron microscopy

Cross-reactions between alpha-streptococci and the pneumococcal C-polysaccharide (PnC) were investigated using electron microscopy and immunogold labelling of bacterial cells. Monoclonal antibodies against two different determinants of the PnC molecule were used, one directed against the chain sugar of the repeating unit 2-acetamido-4-amino-2,4,6-trideoxygalactose (Sug) and the other against the phosphorylcholine residue. Two different immunogold techniques were tested, either by direct labelling of the monoclonal antibody or by using an antimouse immunogold conjugate to demonstrate binding of the monoclonal antibodies. Antibodies against the "Sug" determinant reacted only with pneumococci, whereas antibodies against the phosphorylcholine determinant bound to cross-reacting streptococci as well as to pneumococci. These results indicate that the cross-reacting antigens of the alpha-streptococci contain phosphorylcholine residues, but that they are not identical to the C-polysaccharide molecule.

Rapid etiological diagnosis of pneumonia in young men

The major findings and conclusions of the present study are: 1. Evidence of the etiology of the pneumonia was established in 86% of 106 young men with pneumonia. Pneumococcus was the most common etiologic agent; it was detected definitely in 30% of the pneumonia patients, and possibly in another 20%, by blood culture, sputum culture, antigen detection, and serological methods. 2. Pneumococcal antigen detection from purulent pretreatment sputum samples was the best rapid diagnostic method for pneumococcus; it was capable of identifying 90% of the pneumococcal pneumonias definite by our criteria, whereas sputum Gram stain was positive in 65% of these. 3. Detection of adenoviral antigens from nasopharyngeal specimens (NPS) by EIA or IF method or adenovirus DNA by HYB method showed good specificity but a somewhat lower sensitivity than did adenovirus isolation from NPS. 4. Adenovirus antigens and DNA can be demonstrated also from sputum specimens. 5. EIA is slightly superior to the CF method in detecting antibody responses to adenovirus, but the detection of different antibody classes offers no additional diagnostic possibilities. 6. Isolation of Mycoplasma pneumoniae from bronchoalveolar fluid in pneumonia patients is a specific and sensitive method in the diagnosis of mycoplasmal pneumonia. 7. It seems possible to differentiate by clinical signs and symptoms and by high CRP (over 85mg/1) and WBC (over 10 x 10(9)/1) values pneumococcal pneumonias from viral, mycoplasmal and mixed pneumonias and from upper respiratory infections. Moderately elevated CRP values were observed in adenoviral (Mean 50 mg/1) and in mycoplasma (mean 59 mg/l) pneumonias, as well as in MRI (mean 44 mg/l).

Availability of reaction with antibodies of the pneumococcal C-polysaccharide on the surface of capsulated pneumococci

Antigen detection for diagnosis of pneumococcal infections has earlier been based on the use of antibodies against capsular antigens. Methods based on the demonstration of C-polysaccharide (PnC) have the advantage of using antibodies against one single species-specific antigen instead of applying a polyvalent mixture of antisera against 83 different capsular antigens. Very little has been done earlier to evaluate the accessibility of the PnC on the surface of pneumococcal cells, particularly cells carrying capsules, and the release of PnC to the environment. We have used a monoclonal anti-PnC antibody in an ELISA inhibition test to demonstrate PnC during growth from four different Streptococcus pneumoniae strains (capsular types 1, 3 and 19F) and a C-mutant strain, reported to carry PnC as a small capsule. Heavily-capsulated types 3 and 19F exposed more PnC on their surface than the type 1 strain, and considerable amounts of PnC were released to the culture medium during growth. The C-mutant strain differed from the other strains in that it exposed less PnC on its surface. The type 1 strain and the C-mutant released approximately the same amount of PnC to the culture medium. Treatment with antibiotics during growth caused a decrease in surface-located PnC but did not significantly affect the amount released. The total accessible PnC in these cultures was quite significant and well above the limit of detection in an ELISA earlier described for the detection of PnC in clinical samples. The results presented here give support to the notion that the demonstration of PnC in clinical samples should provide a good basis for diagnosis of pneumococcal pneumonia.

Pneumococcal antigens and endotoxin in effusions from patients with secretory otitis media

Counterimmunoelectrophoresis revealed pneumococcus capsular polysaccharide antigen in 16% of 108 effusions from chronic secretory otitis media (SOM). Pneumococci were cultured from the effusion in only 1%. In an additional series of 23 SOM ears, only 4.3% were antigen-positive. Tests by means of pneumococcal coagglutination and C-polysaccharide detection gave identical results. Endotoxin was detected in 76% of the specimens. Control tests with aggregated NHS, IgG and IgA diluted 1: 10 were invariably positive. It appears that endotoxin positivity in SOM fluids results from the presence of activated immunoglobulins, most probably dimeric IgA, in the secretion, and so allows no conclusions as to the bacterial etiology of SOM.

Comparison of immunological methods for diagnosis of pneumococcal pneumonia in biological fluids

Five immunological tests were evaluated for their ability to detect Streptococcus pneumoniae antigen in serum and urine simultaneously as a means of rapid diagnosis in 40 patients with bacteremic or non-bacteremic pneumococcal pneumonia or pneumonia with other etiologies. Serum and urine were screened in parallel with counterimmunoelectrophoresis (CIE), two commercial latex agglutination kits - the Slidex pneumokit (LA-SPK) and the Bactigen Streptococcus pneumoniae kit (LA-Bac) - the coagglutination Phadebact Pneumococcus test (CoA) and a newly developed enzyme-linked immunosorbent assay (ELISA) containing the immunoglobulin G fraction from rabbit pneumococcal antiserum. The detection rate for accumulated serum in bacteremic patients was 18% for LA-Bac, 24% for CIE, 47% for LA-SPK and CoA and 76% for ELISA, whereas antigenuria was present in only 29% for LA-SPK, 24% for CIE, 19% for CoA, 14% for LA-Bac and 5% for ELISA. Detection by ELISA of pneumococcal antigen in severely ill patients can predict bacteremia and rapidly confirm the diagnosis of pneumococcal pneumonia if sputum and results of blood cultures are not available.

Diagnosis of pneumococcal pneumonia by enzyme-linked immunosorbent assay of antibodies to pneumococcal hemolysin (pneumolysin)

An enzyme-linked immunosorbent assay (ELISA) with a highly purified pneumolysin as the antigen was evaluated for serological diagnosis of pneumococcal pneumonia. One hundred four healthy controls were tested, and the specificity of the test was set to 95%. In samples from patients with bacteremic pneumococcal pneumonia, 82% (18 of 22) were positive, i.e., at least one serum sample had a titer above the upper normal limit or at least a twofold rise in antibody titers was noted. In nonbacteremic pneumococcal pneumonia, 45% (21 of 47) of samples were positive. All sera were negative for patients with pneumonia caused by Haemophilus influenzae, Legionella pneumophila, Chlamydia psittaci, and influenza A virus. However, in patients with a diagnosis of Mycoplasma pneumoniae infection, 8 of 25 (32%) samples were positive for antibodies to pneumolysin. All sera, including those from patients with mycoplasma infection, were negative to a protein control antigen by ELISA. Serum immunoglobulin G response to pneumolysin as measured by ELISA might thus be an aid in the laboratory diagnosis of pneumococcal pneumonia. This assay may also help to further elucidate the occurrence of dual infections with pneumococci.

Aetiology of community-acquired pneumonia in hospital treated patients

From May 1982 a prospective 1-year study of adult patients with community-acquired, radiologically verified, hospital treated pneumonia was performed at the Department of Infectious Diseases, Orebro Medical Center Hospital, Orebro, Sweden. The study included 147 patients with a median age of 71 years. Special efforts to diagnose a pneumococcal aetiology were accomplished by antigen detection of the pneumococcal C-polysaccharide (PnC) in sputum and saliva samples and by serological methods for determination of antibody titres against PnC. A pneumococcal aetiology was established in 46.9% of the patients, including 8.1% with double infections. Altogether Haemophilus influenzae A virus were noted in 9.5%, respectively, Mycoplasma pneumoniae in 5.4%, legionnaires' disease in 2.7% and Branhamella catarrhalis in 2.0%, whereas enteric gram-negative bacilli as aetiological organisms were not found in any patient. These findings imply that penicillin should still be the first drug of choice in hospitalized adult patients with community-acquired pneumonia in Sweden.

Comparison of enzyme-linked immunosorbent assay with coagglutination and latex agglutination for rapid diagnosis of pneumococcal pneumonia by detecting antigen in sputa

A sandwich enzyme-linked immunosorbent assay detecting the species-specific pneumococcal C polysaccharide was compared to latex agglutination and a coagglutination test which detected capsular pneumococcal antigens in sputum specimens with regard to specificity and sensitivity. Specimens from 52 patients with clinical and radiological evidence for pneumonia were tested. Twenty-one patients with Streptococcus pneumoniae isolated in sputum and 31 patients with a non-pneumococcal etiology were included. The predictive values for a positive test by enzyme-linked immunosorbent assay was 0.91 and for a negative test 0.97, by latex agglutination 0.90 and 0.91, and by coagglutination 0.84 and 0.85 respectively; these values did not show a statistically significant difference. Whereas agglutination tests are technically more simple and can be performed more rapidly, the enzyme-linked immunosorbent assay has the advantage of detecting pneumococcal C polysaccharide, an antigen common to all pneumococci. Thus it provides an interesting alternative to tests based on serum containing antibodies to all 83 different capsular polysaccharides.

Routine use of counterimmunoelectrophoresis for the detection of pneumococcal antigen in sputum

Sputum samples obtained routinely for culture from patients at a thoracic department were also examined for pneumococcal antigen by means of counterimmunoelectrophoresis (CIE), using a polyvalent antipneumococcal type serum (omniserum). Pneumococci were found in 1.3% of the 880 cultures, whereas pneumococcal antigen was detected with CIE in 6.5%. The validity of these findings was tested by correlating them with the presence of clinical symptoms in those with positive tests and also by antigen detection in ELISA using monoclonal antibodies specific for the C-polysaccharide common to all types of pneumococci. Clinical findings corresponding to confirmed or probable current chest infection were found in 36 of the 48 patients with positive CIE. ELISA was positive in 33 of the 38 patients with positive CIE who were tested. Although the study deals with an unselected material of chest patients, it indicates that CIE is a sensitive method and that it is independent of current antibiotic treatment. Pneumococcal infection is probably of importance in exacerbations of chronic obstructive lung disease, but the clinical usefulness of detecting pneumococcal and other antigens in this patient group needs to be studied further.

Detection of bacterial antigens in body fluids by the Phadebact system

150 infected patients from 2 study centers had body fluids examined for presence of bacterial antigens (group B streptococcus, Streptococcus pneumoniae, Neisseria meningitidis and Haemophilus influenzae type b) using the Pharmacia Phadebact system. The rates of detection of the pneumococcal antigens in the urine or serum of the patients with pneumococcal pneumonia, pneumococcal bacteremia and pneumococcal meningitis were 0.38, 0.47 and 0.5, respectively. The overall detection rate for H. influenzae infections was 0.92 and for group B streptococcal infections 0.87. Serum and urine from 100 non-infected patients were also tested for the presence of group B streptococcus, S. pneumoniae, N. meningitidis and H. influenzae type b antigens with only 1 false positive (H. influenzae type b).

Detection of C polysaccharide in Streptococcus pneumoniae in the sputa of pneumonia patients by an enzyme-linked immunosorbent assay

The pneumococcal C polysaccharide (PnC) is species specific and believed to be a cell wall component of all pneumococcal types. A sandwich enzyme-linked immunosorbent assay (ELISA) for detection of PnC in sputa has been developed by using a monoclonal antiphosphorylcholine antibody and a polyclonal rabbit anti-PnC antiserum in the test system. A 1-year study of adult hospitalized patients with community-acquired pneumonia was performed. A total of 147 patients with clinical and radiological evidence for pneumonia were accepted for the study. Of these, 105 patients provided a sputum sample upon admission to the ward. The sputa were cultured semiquantitatively as well as tested for the presence of antigen. Of the sputum samples from patients with Streptococcus pneumoniae, 27 of 33 (accounting for a sensitivity of 82%) were positive in the ELISA test. Of the sputum samples from patients with pneumonia of some other known or suspected etiology, 32 of 34 (accounting for a specificity of 94%) were negative. In addition, 7 sputum samples from 31 patients with pneumonia of unknown etiology were positive. The ELISA test described here is in our opinion a sensitive and specific test for detecting PnC from S. pneumoniae in sputa from patients with untreated pneumonia.

Cross-reactions between alpha-streptococci and Omniserum, a polyvalent pneumococcal serum, demonstrated by direct immunofluorescence, immunoelectroosmophoresis, and latex agglutination

In recent years several groups have used serological methods to demonstrate pneumococcal capsular antigens in sputum. In the present study 123 strains of alpha-hemolytic streptococci (including 97 strains from sputum or pharyngeal specimens) were tested for cross-reactions with a polyvalent antipneumococcal serum (Omniserum). Representatives of the following species were included: Streptococcus bovis, S. equinus, S. intermedius, S. lactis, S. milleri, S. mitis, S. mutans, S. sobrinus, S. salivarius, S. sanguis, S. suis, and Aerococcus viridans. Serological reactions were detected by direct immunofluorescence, immunoelectroosmophoresis, and latex agglutination. Fifteen (12%) of the strains gave positive reactions by all three methods. Positive reactions were also observed with another 32 strains (26%) with two of the methods, whereas 37 strains (30%) gave positive reactions by just one technique. Altogether 84 (68%) strains gave positive reactions with one or more of the methods. Latex agglutination gave positive reactions with 26 (21%) strains compared with 57 (46%) in immunofluorescence and 63 (51%) in immunoelectroosmophoresis. Absorption of the antiserum with one alpha-hemolytic strain reduced but did not entirely eliminate the cross-reactions with five tested strains. These findings indicate a potential risk of cross-reactions with polyvalent antipneumococcal serum in tests carried out on sputa or other specimens which may be contaminated with alpha-hemolytic streptococci.

Assessment of rapid methods of pneumococcal antigen detection in routine sputum bacteriology

Sputum specimens from 480 patients were examined for the presence of pneumococci by Gram film and culture and for pneumococcal antigen by counterimmunoelectrophoresis, coagglutination, and latex agglutination. Ninety six positive specimens were detected. Gram film and culture provided the most reliable techniques in well taken specimens collected early in the illness before antibiotic treatment had started. More than 70% of the specimens examined were submitted after starting antibiotics, however, and in these specimens, methods of antigen detection proved of greater value than either Gram film or culture. Counterimmunoelectrophoresis, coagglutination, and latex agglutination were similar in sensitivity and specificity, but coagglutination and latex agglutination were much easier to perform and to read.

Antibody response against the type specific capsular polysaccharide in pneumococcal pneumonia measured by enzyme linked immunosorbent assay

The enzyme linked immunosorbent assay (ELISA) was used for estimation of the IgG and IgM antibody responses against 13 type specific pneumococcal capsular polysaccharides, individually and in a pool, in 52 patients with pneumococcal pneumonia and in 20 control patients with non-pneumococcal pneumonia or enterobacterial septicemia. By use of the isolated type 3 polysaccharide as antigen a greater than or equal to 50% increase in absorbance from acute to convalescence phase serum, equivalent to a doubling in antibody titer, was seen significantly more often in 22 patients with type 3 pneumococcal pneumonia than in the 20 control patients (for IgG 14 vs. 3, p less than 0.01; for IgM 14 vs. 4, p less than 0.01). However, for an acceptable degree of specificity to be obtained (less than or equal to 10% control patients positive) a doubling of the IgG or IgM absorbance values had to be demanded. With this criterium only half of the patients infected with pneumococcal types included in the antigen set up used, showed a type specific antibody response and only one third of all patients with pneumococcal pneumonia could be diagnosed by use of the 13 polysaccharides as a pool antigen.

Diagnosis of pneumococcal pneumonia: a comparison between microscopic examination of expectorate, antigen detection and cultural procedures

Attempts to demonstrate Streptococcus pneumoniae, or its soluble type-specific polysaccharide antigen were made on specimens from 205 patients with acute community-acquired pneumonia by (i) blood, nasopharynx and sputum culture, (ii) counterimmunoelectrophoresis (CIE) of serum, urine and sputum specimens utilizing omni-, pool- and type-specific rabbit antisera, and (iii) microscopy of gram-stained sputum smears. Pneumococci could be cultured and/or pneumococcal antigen detected in specimens from 93 (45%) of the patients with the following frequencies in samples obtained before (and after) start of antimicrobial treatment: culture from blood 25% (6%), nasopharynx 59% (18%) and sputum 80% (13%), CIE on serum 3% (9%), urine 8% (18%), urine 20X concentrated 18% (24%), and sputum 56% (56%). Microscopy of sputum smears revealed pneumococci in 65% (17%) of the 93 patients. The value of cultures from blood and sputum was most evident when the samples were obtained early in the course of the disease. With nasopharynx culture and CIE on sputum the number of positive results was doubled if the sampling was repeated. For rapid diagnosis direct Gram stain and CIE on sputum were about equally effective and also strikingly complementary, alone diagnosing 42% and 48% of the patients, respectively, but together detecting 65% of them. Gram stain was most rewarding on early pretreatment samples and CIE on post-treatment samples.

Etiological diagnosis of bacterial pneumonia by gram stain and quantitative culture of expectorates. Leukocytes or alveolar macrophages as indicators of sample representativity

Sputum samples from 151 patients admitted to Roslagstull Hospital for Infectious Diseases, Stockholm, from Sept. 1978 through May 1979 with acute community-acquired lower respiratory tract disease and roentgenological evidence of acute pneumonia were examined by direct microscopy of gram-stained smears and semiquantitative culture. It was carefully noted if the specimen was collected before or after initiation of antibiotic therapy. For an estimate of the suitability of the samples for bacteriological examination 2 criteria were applied: (i) presence of alveolar macrophages, and (ii) purulence, i.e. a ratio leukocytes/squamous epithelial cells of greater than 5. The latter was found to be a good indicator of sample suitability, while the presence of macrophages was not. Of the 266 samples examined 76% were deemed purulent. Potentially pathogenic bacteria in numbers of greater than or equal to 10(5) colony forming units/ml were found in 67% of the purulent sputum samples obtained before antibiotic therapy but in only 36% if such treatment had already been started. Pneumococci were isolated from 52% of pre-treatment samples but from only 8% after treatment. H. influenzae was found as often in post-treatment samples (17%) as in pre-treatment ones (15%) and enteric gram-negative rods twice as often in post-treatment samples (11 vs. 6%). The use of gram-stained smears was a valuable aid in the interpretation of the culture results and the results could be made available to the clinician within minutes after receipt of the specimen. The results were in agreement with those of the cultures for about 75% of the purulent samples.