Peptostreptococcus Species Research Articles

Anaerobic Spondylodiscitis: Case Series and Systematic Review

Bacterial spondylodiscitis is rarely caused by anaerobic organisms. We describe two patients with lumbar vertebral osteomyelitis and discitis caused by anaerobic bacteria, including an unusual occurrence after an endodontic procedure, and review the salient clinical features and outcomes of 31 previously reported cases. Case reports and review of the literature. Median age at presentation was 65 years, with a male-to-female ratio of 2:1. The most common presenting symptoms were back pain, fever, and neurologic deficits. The lumbar spine was most frequently involved (43%); an equal number of cases involved contiguous extension or hematogenous spread. Causative anaerobes were recovered from disk space or vertebrae (13), blood (4), and/or soft tissue abscess and included Bacteroides species (12), Propionibacterium acnes (7), Peptococcus species (4), Peptostreptococcus species and Clostridium species (3 each), Corynebacterium diphtheroides and Fusobacterium species (2 each), and unspecified anaerobes (3). Apart from specific antibiotic selection, medical treatment and outcomes for anaerobic spondylodiscitis are similar to those for aerobic vertebral disk infection.

Socket Infection Due to Retained Gauze After Evisceration

A 64-year-old man had late-onset socket infection due to retained surgical gauze after evisceration. External examination showed a mass of retained surgical gauze with copious yellowish discharge and gas bubbles. Computed tomography scans showed a 3.2 x 2.4 x 2.4-cm heterogeneous mass and numerous gas bubbles. Culture of the discharge yielded Pseudomonas aeruginosa, Streptococcus viridans, Peptostreptococcus species, and Fusobacterium species. Surgical debridement and antibiotic therapy achieved a rapid resolution. Retained gauze after evisceration may lead to socket infection, and such a complication should be avoided.

Antimicrobial Use in Septic Shock

Journal of Gynecologic SurgeryVol. 20, No. 1 Infectious DiseasesAntimicrobial Use in Septic ShockNewton G. OsborneNewton G. OsborneSearch for more papers by this authorPublished Online:6 Jul 2004https://doi.org/10.1089/104240604323022025AboutSectionsPDF/EPUB ToolsPermissionsDownload CitationsTrack CitationsAdd to favorites Back To Publication ShareShare onFacebookTwitterLinked InRedditEmail FiguresReferencesRelatedDetails Volume 20Issue 1Mar 2004 To cite this article:Newton G. Osborne.Antimicrobial Use in Septic Shock.Journal of Gynecologic Surgery.Mar 2004.29-31.http://doi.org/10.1089/104240604323022025Published in Volume: 20 Issue 1: July 6, 2004PDF download

Sensitivity of Bacterial Isolates in Odontogenic Abscesses and Clinical Response to Clindamycin

Objective: To analyse the sensitivity of bacterial isolates in odontogenic abscesses and the clinical response to clindamycin.Patients and Methods: 150 adult patients with odontogenic infections for less than 1 week, requiring surgery, antibiotic therapy, and yielding pus on aspiration were enrolled in a microbiological and clinical study. Patients were treated with 150 mg of clindamycin 4 times daily. The effect of clindamycin was evaluated according to the absence or presence of pus in the abscess after 7 days of treatment plus white blood cell count, blood pressure, and body temperature. Pus samples were inoculated on brain-heart infusion agar in aerobic incubation, and Schaedler agar in anaerobic incubation. The isolated bacteria were identified based on growth characteristics, colonial morphology, Gram's stain reactions, and biochemical assays. Using a disk-diffusion method, the antimicrobial susceptibility of the isolates was determined. According to the rapid iodometric slide test method, β-lactamase production was assayed.Results: All patients had more than 1 microorganism isolated from their abscess. A total of 426 isolates were identified -181 isolates were aerobes and 245 were anaerobes. The most common aerobes were Staphylococcus aureus (75.3%), the viridans-group of Streptococcus (42.7%), and Streptococcus haemolyticus (2.7%). The most common anaerobes found were Peptococcus species (55.3%), gram positive rods (46.0%), Peptostreptococcus species (34.0%), and gram-negative rods (24.7%). Of the 113 strains of Staphylococcus aureus isolated, all were sensitive to clindamycin. All microorganisms were β-lactamase-negative. There were no clinically significant changes in blood pressure, white blood cell count, or body temperature after the treatment.Conclusions: Clindamycin can be considered a good choice of antibiotic and is bacteriologically and clinically effective for treating odontogenic infections.

Clinical presentation and bacteriologic analysis of infected human bites in patients presenting to emergency departments.

Previous studies of infected human bites have been limited by small numbers of patients and suboptimal microbiologic methodology. We conducted a multicenter prospective study of 50 patients with infected human bites. Seventy percent of the patients and assailants were young adult men. Fifty-six percent of injuries were clenched-fist injuries and 44% were occlusional bites. Most injuries were to the hands. Fifty-four percent of patients were hospitalized. The median number of isolates per wound culture was 4 (3 aerobes and 1 anaerobe); aerobes and anaerobes were isolated from 54% of wounds, aerobes alone were isolated from 44%, and anaerobes alone were isolated from 2%. Isolates included Streptococcus anginosus (52%), Staphylococcus aureus (30%), Eikenella corrodens (30%), Fusobacterium nucleatum (32%), and Prevotella melaninogenica (22%). Candida species were found in 8%. Fusobacterium, Peptostreptococcus, and Candida species were isolated more frequently from occlusional bites than from clenched-fist injuries. Many strains of Prevotella and S. aureus were beta-lactamase producers. Amoxicillin-clavulanic acid and moxifloxacin demonstrated excellent in vitro activity against common isolates.

Bacteriologic findings in Patients with Chronic Sinusitis

We studied the bacteriology of maxillary sinus aspirates obtained from patients diagnosed with chronic sinusitis. We recovered 659 strains from 510 aspirates; of these, 572 (86.8%) were aerobes and 87 (13.2%) were anaerobes. Aerobes only were recovered from 310 of the 510 specimens (60.8%) and anaerobes only from 31 (6.1%). Among the 572 aerobic bacteria, the most prevalent organisms were Streptococcus viridans (158 strains [27.6%]), Streptococcus pneumoniae (67 [11.7%]), Corynebacterium species (66 [11.5%]), Staphylococcus aureus (54 [9.4%]), Moraxella catarrhalis (38 [6.6%]), Hemophilus parainfluenzae (33 [5.8%]), and group C beta-hemolytic streptococci (26 [4.5%]). Among the 87 recovered anaerobes were species of Peptostreptococcus (32 strains [36.8%]), Prevotella (22 [25.3%]), Actinomyces (13 [14.9%]), Propionibacterium (11 [12.6%]), Fusobacterium (8 [9.2%]), and Veillonella (1 [1.1%]). Beta-lactamase production was detected in 115 of the 572 aerobic strains (20.1%) and in 10 of the 87 anaerobic strains (11.5%). We found that the prevalence and type of organisms we identified in chronic sinusitis did not differ substantially from those reported in previous studies. Our study is one of the more extensive reports on the type and prevalence of pathogens in chronic sinusitis that has been published to date.

Specific PCR detection of Peptostreptococcus magnus.

Peptostreptococcus magnus is the most pathogenic and one of the most common Gram-positive anaerobic cocci found in human clinical specimens. The organism has been isolated in pure culture from a range of serious infections, including meningitis and endocarditis. However, isolation of Peptostreptococcus magnus from the oral cavity has rarely been attempted. Identification of Peptostreptococcus magnus in clinical specimens is reliant upon microbiological culture and biochemical methods, which often give ambiguous results. The aim of this study was to develop a PCR assay for the specific detection of Peptostreptococcus magnus in oral clinical specimens. PCR primers specific for Peptostreptococcus magnus DNA were derived by comparison of 16S rRNA gene sequences and selection of primers that demonstrated specificity at their 3' ends for Peptostreptococcus magnus. PCR positivity for Peptostreptococcus magnus DNA was indicated by the amplification of a 553 bp product. The PCR assay was then used to attempt detection of Peptostreptococcus magnus DNA in subgingival plaque samples from adult periodontitis patients and pus aspirates from subjects with acute dento-alveolar abscesses. The PCR assay was demonstrated to be highly specific for Peptostreptococcus magnus DNA, since no PCR products were obtained when genomic DNA from a wide range of other oral bacteria, including closely related Peptostreptococcus species, was used in the PCR assay. Confirmation of specific amplification of Peptostreptococcus magnus DNA was obtained by digestion of PCR products with the restriction endonuclease RsaI, which gives a unique restriction profile for Peptostreptococcus magnus. Of the 33 subgingival plaque samples analysed, 2 (6 %) were positive for Peptostreptococcus magnus DNA. None of the 60 pus aspirates analysed was positive for Peptostreptococcus magnus DNA. It is concluded that Peptostreptococcus magnus is not a major pathogen in adult periodontitis or dento-alveolar abscesses. The PCR assay provides a more rapid, specific and sensitive alternative to conventional methods for identification of Peptostreptococcus magnus in clinical specimens.

Development of a PCR assay specific for Peptostreptococcus anaerobius.

Peptostreptococcus anaerobius is a gram-positive anaerobic coccus that is widely distributed in the normal human flora. The organism has also been implicated as a causative agent of several systemic infections, including endocarditis and infections of the genitourinary and gastrointestinal tracts. Its role in oral disease is less well defined, although it has been implicated in periodontal disease, gingivitis and root canal infections. Identification of P. anaerobius in clinical samples is currently reliant upon traditional culture and biochemical methods. The aim of this study was to develop a novel PCR assay for the detection of P. anaerobius and to attempt detection of this organism in oral samples. PCR primers specific for P. anaerobius DNA were developed by alignment of bacterial 16S ribosomal RNA gene sequences and selection of sequences specific at their 3' ends for P. anaerobius. When used in a PCR assay, positivity for P. anaerobius DNA was indicated by the amplification of a 943-bp product. The primers were shown to be specific for P. anaerobius DNA, as no PCR products were obtained when genomic DNA from a wide range of other Peptostreptococcus species and other oral bacteria were used as templates. The PCR assay was then applied to the detection of P. anaerobius DNA in subgingival plaque samples from adult periodontitis patients and pus aspirates from subjects with acute dento-alveolar abscesses. All of 60 subgingival plaque samples from 16 patients were negative for P. anaerobius DNA. None of the 43 pus samples analysed contained P. anaerobius DNA. These results suggest that P. anaerobius is not a major pathogen in adult periodontitis and dento-alveolar abscesses. The PCR assay is a more rapid, sensitive and specific alternative to culture-based methods for identification of P. anaerobius in clinical samples.

Randomized, double-blind, multicenter comparison of oral cefditoren 200 or 400 mg BID with either cefuroxime 250 mg BID or cefadroxil 500 mg BID for the treatment of uncomplicated skin and skin-structure infections

Background: Uncomplicated skin and skin-structure infections are commonly observed in medical practice. Because these infections typically are confined to the superficial layers and seldom lead to the destruction of skin structures and resultant systemic dissemination, in general they can be treated with an oral antibiotic with potent microbiologic activity against gram-positive pathogens.Objective: This paper compares the efficacy and tolerability of 3 beta-lactam antibiotics in patients with uncomplicated skin and skin-structure infections.Methods: Two double-blind, multicenter, parallel-group studies were conducted, in which patients aged ≥12 years with uncomplicated skin and skin-structure infections were randomized to receive cefditoren 200 or 400 mg, cefuroxime 250 mg, or cefadroxil 500 mg, each BID for 10 days. Study 1 compared cefditoren with cefuroxime; Study 2 compared cefditoren with cefadroxil. Clinical and microbiologic responses were assessed at a post-treatment visit (within 48 hours of treatment completion) and test-of-cure visit (7–14 days after treatment completion). Patients were monitored closely throughout the study with the use of physical examinations, clinical laboratory tests, and assessment of adverse events.Results: A total of 1685 patients (855 males, 830 females; mean age, 41.1 years [range, 12–95 years]) were enrolled. Within both studies, the 3 treatment groups were similar at baseline based on demographic characteristics and types of infection. Cellulitis (26%), wound infection (25%), and simple abscess (15%) were the most common infections. Clinical cure rates at the test-of-cure visit were 85% (443/523) for cefditoren 200 mg, 83% (427/516) for cefditoren 400 mg, 88% (234/265) for cefuroxime, and 85% (211/248) for cefadroxil. At the test-of-cure visit, cefditoren 200 mg had eradicated significantly fewer of the causative pathogens isolated before treatment in microbiologically evaluable patients than did cefuroxime in Study 1 (P = 0.043) but significantly more of the pathogens than did cefadroxil in Study 2 (P = 0.018). Eradication rates for the most commonly isolated pathogens were generally similar in the 3 treatment groups in both studies, with the only significant difference favoring cefditoren 200 and 400 mg over cefadroxil for Peptostreptococcus species in Study 2 (P = 0.016 and P = 0.003, respectively). A minority of patients (≤5% in any treatment group) discontinued study-drug treatment prematurely due to a treatment-related adverse event, with statistically higher rates for cefditoren 400 mg than for cefditoren 200 mg and the comparator cephalosporins (each P < 0.05). All 3 cephalosporins were generally well tolerated. Most adverse events (>93%) were categorized as mild to moderate, with the most common being diarrhea, nausea, and headache.Conclusion: In this population of patients with uncomplicated skin and skin-structure infections, including those due to Staphylococcus aureus or Streptococcus pyogenes, the clinical cure rate and tolerability of cefditoren were comparable to those of cefuroxime and cefadroxil.

Cytotoxic effects ofprevotella nigrescenson cultured cells

Infection of the dental pulp commonly occurs as a consequence of caries. Pulpal infections often progress to pulp necrosis and periapical lesion development with periapical bone destruction. The severity of pulpal/periapical inflammation has been directly correlated with the total microbial content within root canals, and with the length of time the periapical tissues were exposed to the infecting microorganisms. Microbial studies of endodontic infections have revealed that gramnegative anaerobic bacteria are the prominent microorganisms. Some combinations of bacterial species present in root canals are more pathogenic in inducing periapical inflammation and bone destruction. Species of Prevotella, Porphyromonas, Fusobacterium, and Peptostreptococcus are strongly linked to increased periapical destruction. Sunqvist et al identified 25 strains of black pigmented Bacteroides in 22 of 72 infected root canals and Jin-Soon Han, Eun-Sook Kim, Su-Jong Lee, Yong-Ouk You*, Kyung-Soo Han**, Mi-Kyung Im Department of Conservative Dentistry, College of Dentistry, Wonkwang University Department of Oral Biochemistry, College of Dentistry, Wonkwang University* Department of Oral Medicine, College of Dentistry, Wonkwang University** Cytotoxic Effects of Prevotella nigrescens on Cultured Cells

Splenic abscess caused by Peptostreptococcus species, diagnosed with the aid of abdominal computerized tomography and treated with percutaneous drainage and antibiotics: a case report

We describe herein a 63-year-old patient with a splenic abscess due to Peptostreptococcus spp., diagnosed with the aid of abdominal computerised tomography and treated with ultra-sound guided percutaneous drainage and antibiotics. The bacteriological characteristics of splenic abscesses are discussed.

Recovery of anaerobic bacteria from four children with postthoracotomy sternal wound infection.

The cases of 4 children who developed postthoracotomy sternal wound infection caused by anaerobic bacteria are presented. The predominate anaerobes were Peptostreptococcus species and pigmented Prevotella species. Polymicrobial infection was present in all cases, and aerobic bacteria also were recovered in 2 instances. All patients responded to surgical debridement and antimicrobials effective against the isolated aerobic and anaerobic bacteria. These findings highlight the potential importance of anaerobic bacteria in postthoracotomy sternal wound infection.

Detection of Peptostreptococcus micros DNA in clinical samples by PCR

Peptostreptococcus micros is a gram-positive anaerobic coccus which, although considered to be a natural commensal of the human oral cavity, is associated with periodontal, endodontal and peritonsillar infections. Identification of the organism has to date relied upon conventional culture methods and biochemical analyses. The purpose of this study was to develop a PCR method for rapid and specific identification of this organism in clinical samples. A pair of primers was selected, each of which was specific at the 3' end for P. micros DNA; they were used in the PCR assay, resulting in a 1074-bp product. The primers were shown to be specific for P. micros DNA as no PCR products were obtained when genomic DNA extracts from a wide range of other Peptostreptococcus species and other oral bacteria were used as templates. The PCR assay was then applied to the identification of P. micros DNA in subgingival plaque samples from adult periodontitis patients and pus samples from subjects with acute dento-alveolar abscesses. Confirmation of specific amplification of P. micros DNA was obtained by digestion of PCR products with the restriction endonuclease RsaI, which gives a unique restriction profile for P. micros, and DNA sequencing. Sixty-eight subgingival plaque samples from 18 patients were analysed, of which 19 (28%) were positive for P. micros DNA; the proportion of patients carrying P. micros DNA in at least one sampled site was 11 (61%) of 18. Twenty (71%) of 28 pus samples analysed by PCR contained P. micros DNA. These results confirm that P. micros may be involved in the aetiology of acute dentoalveolar abscesses and adult periodontitis. The PCR assay provides a more rapid and reliable alternative to conventional methods for identification of P. micros in clinical samples.

Phospholipid analogue profiles of &lt;i&gt;Peptostreptococcus&lt;/i&gt;, &lt;i&gt;Micromonas&lt;/i&gt;, and &lt;i&gt;Finegoldia&lt;/i&gt; species analysed by fast atom bombardment mass spectrometry

Species of Peptostreptococcus cause a variety of infections, primarily abscesses of soft tissues, joints, and mucous membranes. The aim of this study was to compare the phospholipid analogue profiles of Peptostreptococcus species, represented by P. anaerobius, P. asaccharolyticus, P. indolicus, P. lacrimalis, and P. prevotii; Micromonas micros (P. micros) and Finegoldia magna (P. magnus). After anaerobic growth on blood-FAA, lipids extracted by chloroform-methanol (2:1 v/v) were purified, then analysed by fast atom bombardment mass spectrometry (FAB-MS) in negative ion mode. The major peaks with mass to charge (m/z) 719, 721, and 749, corresponded to phosphatidylglycerol analogues, namely PG (32:1), PG (32:0), and PG (34:0), which have been found previously in Lactobacillus spp., Clostridium difficile, and Staphylococcus spp. Other major peaks observed, with m/z 619, 647, 665, 675, 677, 687, 691, 693, 701, 703, 707, 733, and 746 have also been reported in one or more of these three species. However, other major peaks found here in Peptostreptococcus, Micromonas, and Finegoldia have not been described elsewhere; these are 501, 514, 515, 618, 659, 673, 676, 688, 690, 692, 694, 700, 706, 715, 718, 722, and 750. We conclude that Peptostreptococcus, Micromonas, and Finegoldia isolates are chemically unique.

Phospholipid analogue profiles of Peptostreptococcus, Micromonas, and Finegoldia species analysed by fast atom bombardment mass spectrometry

Species of Peptostreptococcus cause a variety of infections, primarily abscesses of soft tissues, joints, and mucous membranes. The aim of this study was to compare the phospholipid analogue profiles of Peptostreptococcus species, represented by P. anaerobius, P. asaccharolyticus, P. indolicus, P. lacrimalis, and P. prevotii; Micromonas micros (P. micros) and Finegoldia magna (P. magnus). After anaerobic growth on blood-FAA, lipids extracted by chloroform-methanol (2:1 v/v) were purified, then analysed by fast atom bombardment mass spectrometry (FAB-MS) in negative ion mode. The major peaks with mass to charge (m/z) 719, 721, and 749, corresponded to phosphatidylglycerol analogues, namely PG (32:1), PG (32:0), and PG (34:0), which have been found previously in Lactobacillus spp., Clostridium difficile, and Staphylococcus spp. Other major peaks observed, with m/z 619, 647, 665, 675, 677, 687, 691, 693, 701, 703, 707, 733, and 746 have also been reported in one or more of these three species. However, other major peaks found here in Peptostreptococcus, Micromonas, and Finegoldia have not been described elsewhere; these are 501, 514, 515, 618, 659, 673, 676, 688, 690, 692, 694, 700, 706, 715, 718, 722, and 750. We conclude that Peptostreptococcus, Micromonas, and Finegoldia isolates are chemically unique.

Evaluation of a phenotypic scheme for identification of the 'butyrate-producing' Peptostreptococcus species.

Gram-positive anaerobic cocci (GPAC) are isolated from approximately one quarter of all infections involving anaerobic bacteria. However, studies of the significance of this group of pathogens have been hindered by an inadequate taxonomy and the lack of a valid identification scheme. In the present study, a phenotypic scheme for the identification of 'butyrate-producing' GPAC based on the analysis of volatile fatty acid profiles by gas-liquid chromatography, biochemical profiles (including the use of the rapid ID 32 A commercial kit) and carbohydrate fermentation reactions, was evaluated. The identity of 68 clinical isolates of GPAC was determined by application of the scheme published by Murdoch. The scheme was found to be easy to apply and only four of the test isolates could not be readily assigned to a species or well-defined group. The species most frequently identified in the test collection were Peptostreptoccoccus vaginalis, P. tetradius and the betaGAL group. A large number of strains was assigned to the heterogeneous 'prevotii/tetradius' group. Some species regarded as being restricted to particular clinical sites were shown to be more widespread than previously thought. The clinical source of the isolates did not show any consistent correlation with species identity.

Characterization of Peptostreptococcus species in skin infections.

We examined the characteristics of Peptostreptococcus species in infectious skin diseases. P. magnus was the species identified most frequently, followed by P. asaccharolyticus. Peptostreptococcus species were mainly isolated from infected atheroma and secondary infections due to ulcers; their resistance to five antimicrobial agents was generally low. The resistance of the three predominant Peptostreptococcus species to the antimicrobials was similar to that of all of the Peptostreptococcus species. The predominant Peptostreptococcus species isolated from infected atheroma might be pathogenic. It was considered that the presence of anaerobes as well as aerobes was important to induce the infectious condition.

Laboratory diagnosis of anaerobic pleuropulmonary infections

Anaerobic organisms play a major role in pleuropulmonary infections. Clinical manifestations range from simple aspiration to acute, severe, necrotizing pneumonias to chronic infections, such as lung abscess and empyema. Implicated pathogens are usually of endogenous origin. Laboratory diagnosis of anaerobic pleuropulmonary infections is based on recovering the etiological agent from clinical specimens. Appropriate specimens include pleuml fluid, transtracheal aspirates, transthoracic aspirates and fiberoptic bronchoscopic aspirates. Collection and transport of uncontaminated specimens is crucial to the recovery of the causative agents. Evaluation of a Gram's stain of clinical material provides a guide to initial therapy. Pigmented and non-pigmented Prevotella species, Fusobacterium nucleatum, Peptostreptococcus species, and Bacteriodes species are the most commonly recovered anaerobes in pleuropulmonary infections. Successful treatment of anaerobic pleuropulmonary infections requires a combination of antibiotic therapy and surgical interventions. Routine susceptibility testing of recovered isolates is rarely warranted.

Dynamics of nasopharyngitis in children

Purpose: Our goal was to characterize the dynamics and bacterial interaction of the aerobic and anaerobic flora of nasal discharge of children at different stages of uncomplicated nasopharyngitis. Methods And Patients: Serial semiquantitative nasopharyngeal (NP) and quantitative nasal discharge (ND) cultures were taken every 3 to 5 days from 20 children in whom purulent discharge eventually developed (group 1), and a single culture was obtained from a group of 20 who had only clear discharge (group 2). Results: Aerobic and anaerobic bacteria were isolated from all NP cultures. Bacterial growth was present in 8 (40%) NDs of group 2. Only 7 (35%) of the clear NDs of group 1 showed bacterial growth; the number increased to 14 (70%) at the mucoid stage and 20 (100%) at the purulent stage. It declined to 6 (30%) at the final clear stage. The number of species and total number of organisms increased in the NDs of group 1. Group 1 patients had higher recovery rates of Streptococcus pneumoniae and Haemophilus influenzae in their NP cultures than group 2 patients ( P < 0.05). During the purulent stage, Peptostreptococcus species were isolated in 15 (75%), Fusobacterium species in 10 (50%), Prevotella species in 9 (45%), H influenzae in 8 (40%), S pneumoniae in 6 (30%), and β-hemolytic streptococci in 5 (25%) of group 1 NDs. This was higher than their recovery in the clear stages of both groups and the mucoid stage of group 1. A total of 8 organisms capable of interfering with the growth of potential pathogens were isolated from the NPs of group 1, as compared with 35 from group 2 ( P < 0.001). Conclusions: The development of purulent nasopharyngitis is associated with the pre-existing presence of potential pathogens and the absence of interfering organisms. (Otolaryngol Head Neck Surg 2000;122:696-700.)

Dynamics of nasopharyngitis in children.

Our goal was to characterize the dynamics and bacterial interaction of the aerobic and anaerobic flora of nasal discharge of children at different stages of uncomplicated nasopharyngitis. Serial semiquantitative nasopharyngeal (NP) and quantitative nasal discharge (ND) cultures were taken every 3 to 5 days from 20 children in whom purulent discharge eventually developed (group 1), and a single culture was obtained from a group of 20 who had only clear discharge (group 2). Aerobic and anaerobic bacteria were isolated from all NP cultures. Bacterial growth was present in 8 (40%) NDs of group 2. Only 7 (35%) of the clear NDs of group 1 showed bacterial growth; the number increased to 14 (70%) at the mucoid stage and 20 (100%) at the purulent stage. It declined to 6 (30%) at the final clear stage. The number of species and total number of organisms increased in the NDs of group 1. Group 1 patients had higher recovery rates of Streptococcus pneumoniae and Haemophilus influenzae in their NP cultures than group 2 patients (P < 0.05). During the purulent stage, Peptostreptococcus species were isolated in 15 (75%), Fusobacterium species in 10 (50%), Prevotella species in 9 (45%), H influenzae in 8 (40%), S pneumoniae in 6 (30%), and beta-hemolytic streptococci in 5 (25%) of group 1 NDs. This was higher than their recovery in the clear stages of both groups and the mucoid stage of group 1. A total of 8 organisms capable of interfering with the growth of potential pathogens were isolated from the NPs of group 1, as compared with 35 from group 2 (P < 0.001). The development of purulent nasopharyngitis is associated with the pre-existing presence of potential pathogens and the absence of interfering organisms.