Throat Flora Research Articles

Microbiological profile of oxygen humidifiers at a tertiary care centre in the Himalayas

Background: Reusable humidifiers are often colonised by microbes, the aerosols generated from which are hypothesised to transmit respiratory infections-jeopardising patient safety. Materials and Methods: In this time-bound cross-sectional study, 10 ml of water was collected in sterile containers from humidifiers installed in selected wards/critical care units/intensive care units and from the source used to refill these humidifiers. These samples were subjected to KOH and gram staining followed by inoculation on blood, MacConkey and Sabouraud dextrose agar and brain heart infusion broth in the aerobic environment at 37°C. Observations were recorded as per standard guidelines and compared against blood and respiratory cultures of patients. Results: Despite an average of 8.23 days of exposure to oxygen humidified by contaminated water, n = 28 (of n = 39) blood samples reported no growth (NG) and n = 12 reported nonpathogenic organisms (NPO). Among n = 18 available respiratory samples, n = 1 reported Escherichia coli, which was not cultured from the same humidifier indicative of some other source. n = 1 reported NG, n = 6 reported NPO and n = 10 reported normal throat flora. No fungal elements were reported from any humidifier, source, or patient samples. The source-humidifier pathogen pair did not match for any humidifier. Conclusions: Sterile patient cultures, despite prolonged exposure to oxygen humidified with contaminated water, indicate that humidifier contaminants did not infect patients. The disparity between the source or patient cultures and humidifier contaminants may be attributed to compromised universal precautions due to the exhaustion of health-care professionals during COVID-19. Furthermore, the type of water used to refill (Distilled/RO/Tap water) had no effect on the microbial contamination of humidifiers.

Change in lung clearance index with microbiological status in children with cystic fibrosis.

The impact of infections caused by bacteria, especially Gram-negative, on the progression of lung disease in cystic fibrosis is well established. Decline in pulmonary function commence already at early age. In this group of patients, the lung clearance index seems to be a better marker than FEV1 allowing non-invasive monitoring of changes in small airways. The aim of this study was to investigate the association between the microbiological status and LCI derived from multiple breath washout (MBW) technique as well as FEV1 and FVC in children suffering from cystic fibrosis. Over the 1-year recruitment period, 136 CF patients aged 5-18 with: Staphylococcus aureus (n-27), Pseudomonas aeruginosa (first time (n-27), intermittent (n-9), and chronic (34) infection), Aspergillus fumigatus (n-6) and without pathogenic flora (n-33) were included in the study. Patients had performed a spirometry and MBW test during the visit at outpatient clinic. The study showed that the lung clearance index in patients infected with Aspergillus fumigatus was significantly higher (P < 0.05) than in those with normal throat flora. There was also statistically significant differences in the lung clearance index obtained in subjects with chronic Pseudomonas aeruginosa infection and those with first Pseudomonas aeruginosa infection (P < 0.05). Furthermore, significant statistical differences (P < 0.05) were observed between the groups of patients with chronic Pseudomonas aeruginosa infection FEV1 > 70% and FEV1 < 70%. In conclusion, LCI was associated with microbiological status of CF patients. Chronic lung infections, especially Aspergillus fumigatus and Pseudomonas aeruginosa, were associated with increased LCI. Early eradication of pathological flora positively affects the maintenance of lower LCI.

Role of hygienic factors in the etiology of allergic disorders in children.

We investigated the role of body flora and chronic inflammatory infections in the etiology of allergic disorders in Turkish children. Forty pediatric asthma patients with positive skin prick tests and 40 age-matched healthy subjects with negative skin prick tests were enrolled in this cross-sectional study. Serum H. pylori IgG, viral hepatitis serology, IL-10, and TGF-beta levels were measured. Stool and throat cultures were taken and tested for occurrence of microorganisms. A significantly higher percentage of nonatopic subjects tested positive for anti-H. pylori antibodies compared to atopic subjects (60% vs. 20%). Serum IL-10 levels were also significantly higher in nonatopic subjects. No significant differences in direct microscopy and culture specimens of stools were observed. Examination of throat flora showed significantly higher occurrences of Neisseria and beta-hemolytic Streptococcus in nonatopic subjects, but higher occurrences of gram-positive bacilli in atopic subjects. Higher prevalence of anti-H. pylori antibody and higher serum levels of IL-10 in nonatopic subjects suggest that chronic infection and inflammation may protect against atopic disease. Higher occurrences of Neisseria and beta-hemolytic Streptococcus in throat cultures from nonatopic subjects are novel findings that lend further support to the hygiene hypothesis.

Report of a Moraxella catarrhalis prosthetic joint infection in an immunocompetent woman and review of the literature of haematogenous infection due to throat flora bacteria

Introduction: Moraxella catarrhalis is an exclusively human commensal and mucosal pathogen. For years, this bacterium has been known to cause upper and lower respiratory tract infections, the latter of which most often occur in patients with chronic obstructive pulmonary disease. However, M. catarrhalis has also been described in various unusual localizations. Case presentation: We describe the first case of a knee prosthetic infection due to M. catarrhalis. A 75-year-old immunocompetent woman developed a knee infection 5 months after a total knee arthroplasty. The origin of the infection was probably due to a bronchitis episode with haematogenous spread leading to an acute prosthetic infection. Conclusion: M. catarrhalis should be included in the list of potential pathogens from the throat flora such as Streptococcus pneumoniae and Haemophilus influenzae. A review of the literature revealed the same clinical presentation, surgical strategy and outcome.

46 Microbiological airway flora in children with cystic fibrosis in the first year of life (To treat or not to treat, that's the question!)

In children with cystic fibrosis (CF) pulmonary microbial colonization and infection are important prognostic factors. In Germany a national CF newborn screening does not exist by now and only little is known about the microbial respiratory flora of children with CF in the first years of life. In Dresden a regional newborn screening program for eastern Saxony exists since 1996. Thus, a microbiological monitoring for patients with CF was already performed from diagnosis in the first month of life throughout babyhood and we collected data from 1997 on. In the following, we want to demonstrate the microbial colonization of 55 patients in our center in their first year of life. In all patients we found bacteria other than normal flora of mouth and throat. Most commonly we detected Staphylococcus aureus, Haemophilus influenzae and Escherichia coli, but also a variety of many other such as Klebsiella, Serratia, Streptococcus, Enterobacter, Enterococcus and Acinetobacter species, Bacillus cereus, Branhamella catarrhalis, and more. We also detected Pseudomonas aeruginosa and other Pseudomonas species already in patients at this young age. In several patients we found fungi in the throat swab, such as Aspergillus , Candida and Saccharomyces species. Most of the patients needed antibiotic therapy in their first year of life due to pulmonary exacerbation, but the clinical symptoms in many cases did not correlate with the microbiological findings by throat swab. With the introduction of a national newborn screening program for CF hopefully end of this year, we will have to discuss the influence of these bacterial findings in the first year of life on the prognosis and the need for treatment.

A Research of nasal methicillin resistant/sensitive Staphylococcus aureus and pharyngeal beta-haemolytic Streptococcus carriage in midwifery students in Kahramanmaras, Eastern Mediterranean Region of Turkey

Background: In the hospitals where hygienic conditions are not provided, nasal methicillin resistant/sensitive Staphylococcus aureus (MRSA/MSSA) colonization is seen in the hospital personnel and patients. Both the individuals’ themselves being MRSA/MSSA carriers and also other people around them are under risk and this bacterium leads to nasal colonization and then can propagate through contaminated hands and hospital materials.Objective: In this study, it was aimed to research MRSA/MSSA and beta-haemolytic streptococcus (BHS) carriage in the nose and throat flora of students of, School of Health.Methods: In the study, total of 160 midwifery students taking midwifery education was included in the research but 135 (84.4 %) out of 160 students were able to be reached. The nose and throat swab samples taken from students were examined through microbiological methods.Results: 14.1 % of students were nasal MSSA carrier. While there wasn't the nasal MRSA carrier among students attending the study in the 1st and 2nd class, 3.3 % (1 person) of the 3rd class students and 10.0 % (3 people) of the 4th class students were the nasal MRSA carrier. In addition, BHS carriage was determined in 1.5 % of students and there wasn't any difference between classes.Conclusions: These results indicate that midwifery students might have been contaminated with MSSA/MRSA during clinical practice. That MSSA/MRSA being an important pathogen is seen in midwifery students taking education in the birth units threatens the mother-child health. [Ethiop. J. Health Dev. 2010;24(1):57-60]

Influence of inhaled corticosteroids on distribution of throat flora in children with bronchial asthma

To explore the effects of inhaled corticosteroids (ICS) on the distribution of throat flora in children with bronchial asthma. Sixty healthy children were included in the study as the control group and 160 children with asthma in acute period before ICS therapy were chosen as the experimental group. The experimental group were treated with ICS therapy. In this group, 89 children were followed up for 3 months, 68 for 6 months and 60 for 12 months. The ICS in the study was budesonide with the trade name as Pulmicort. Swab from the pharynx was used, then inoculated in agar plate. The bacteria were isolated, the distribution and variation of the microbial population in pharyngeal portion were evaluated. The data collected were analyzed using SPSS12.0 software. Bacteria could be detected in all samples collected from children with asthma in acute, untreated period, which were mainly non-β-hemolytic streptococcus and gram negative cocci bacteria. Gram negative bacilli, streptococcus pneumoniae and mycetes were less. There were no significant differences (χ(2) value were 4.7441, 7.8582 and 1.5583 respectively, Fisher exact value were 0.0699, 0.6398, 0.2433, 0.8580, 0.6616, 0.6339, and 0.8479 respectively, P > 0.05) among children with asthma in acute period, children with asthma treated with ICS after 3, 6 and 12 months and control group. Three strains of mycetes were detected in the experimental group, and one strain in children with asthma treated with ICS for 6 months group. There were no significant changes in the distribution of throat flora between the control group and the experimental group. The throat microbiology did not show significant change. Inhaled corticosteroids had no obvious effect in throat flora in children with asthma after being used for a short term and for 12 months, which suggested that inhaled corticosteroids was safe in bronchial asthma treatment. Dynamic monitoring of throat flora while the inhaled corticosteroids are used is of clinical significance.

Detection of Fusobacterium necrophorum subsp. funduliforme in tonsillitis in young adults by real-time PCR

Throat swabs from 61 patients, aged 18-32 years, with non-streptococcal tonsillitis (NST) and 92 healthy controls were examined for the presence of Fusobacterium necrophorum DNA using a novel TaqMan-based real-time quantitative PCR assay for F. necrophorum subspecies. The assay was based on the gyrB subunit gene, and detected F. necrophorum DNA in 48% of patients with NST and in 21% of controls (p <0.001). F. necrophorum subsp. funduliforme was the only subspecies found in both patients and controls. The load of F. necrophorum DNA on swabs from patients with NST was significantly higher than that on swabs from controls (p <0.001). Furthermore, patients with recurrent NST had a significantly higher load of F. necrophorum DNA compared to patients with acute NST (p 0.04). In addition, 26 patients with tonsillitis and group C streptococci (GCS) had a significantly higher load of F. necrophorum DNA compared to the NST group (p <0.001). It was concluded that F. necrophorum subsp. funduliforme is present in small numbers as part of the normal human throat flora, and that F. necrophorum in large quantities may cause tonsillitis, especially recurrent tonsillitis. In addition, the study suggests that the concomitant presence of GCS may aggravate F. necrophorum tonsillitis.

Erythromycin resistance in the commensal throat flora of patients visiting the general practitioner: a reservoir for resistance genes for potential pathogenic bacteria

The prevalence and mechanism of erythromycin resistance in commensal throat streptococci was determined from October 2000 until December 2002 as part of an ongoing study of the NIVEL in general practice patients ( N = 678). Resistance prevalence for 1 mg/L and 16 mg/L erythromycin was 57% and 20%, respectively. The percentage of total commensal flora resistant within each patient ranged from 1% to 100% (median, 1%). mefA was predominantly found among isolates on the 1 mg/L plates, and ermB was found in 64% of the isolates on the 16 mg/L plates. Erythromycin resistance was transferred from a commensal isolate to Streptococcus pneumoniae with a frequency of 1 × 10 −9. Commensal streptococci of general practice patients in The Netherlands form a large reservoir of transferable erythromycin resistance (genes) for potential pathogenic microorganisms.

Hydroxymethyldihydropterin pyrophosphokinase from Plasmodium falciparum complements a folK-knockout mutant in E. coli when expressed as a separate polypeptide detached from dihydropteroate synthase

Resistance to antimicrobials is an increasing problem in the world of today, and develops faster than man can counter. It is therefore of importance to study metabolic pathways in order to develop new antibiotics, but also to understand how resistance spreads and stabilizes in microbial populations.The commensal flora could be an important factor in the spread of antimicrobial resistance, as drugs aimed at other targets also hit the harmless commensal bacteria. If stable resistance develops in such a population, it could seriously impair a later treatment with the same drug. After a treatment with the macrolide clarithromycin, resistance to this antibiotic increased markedly in the untargeted throat flora, and resistance levels did not recede until at least one year later. Another example of stable resistance can also be seen in sulfonamide resistant Streptococcus pyogenes. Sequence determinations of the dihydropteroate synthase (dhps) gene conferring this resistance revealed a mosaic organisation implying that the it had been brought there by horizontal transfer. Molecular characterization of this gene showed that the sulfonamide resistance was due to mutations of structurally important amino acids in position 65 and 213.The folate synthesis pathway has potential for being exploited further as a drug target. One possible new drug target is hydroxymethyl-dihydropterin pyrophosphokinase (hppk). In the malaria parasite Plasmodium falciparum this enzyme is part of a polyfunctional entity, also encoding dhps. The HPPK part can be separated from DHPS, but that the opposite is not possible. The PfHPPK has two insertions: one also present in other plasmodia, and one apparently unique to P. falciparum. Both are crucial for enzyme activity.To further characterize HPPK, we developed a spectrophotometric activity assay and a method to measure substrate channelling of hydroxymethyl-dihydropterin diphosphate.

Clarithromycin treatment selects for persistent macrolide-resistant bacteria in throat commensal flora

The aim of the study was to determine the effect of clarithromycin treatment on resistance development in the commensal throat flora. Alpha-haemolytic streptococci and Neisseria spp. were isolated from patients receiving clarithromycin for eradication of Helicobacter pylori. The treatment resulted in an immediate increase in the number of macrolide-resistant streptococci, which remained for one year after treatment, but declined to background level three years later. The most prevalent resistance gene was mef(A). Neisseria spp. were less affected by the treatment: the number of resistant isolates increased in only in one case during treatment. In conclusion, a one-week standard therapy with clarithromycin selects for an increased prevalence of macrolide-resistant streptococci that persisted for more than one year.

The Throat Flora and Its Mitogenic Activity in Patients with Kawasaki Disease

The etiology of Kawasaki disease (KD) remains unknown, although some infectious organism has been suggested as the cause. Recent studies suggest that some bacterial toxins with superantigen activity are involved in its pathogenesis, but no specific bacterial toxin has yet been identified. Throat swabs for bacterial culture were obtained from 21 patients with KD and 20 with other febrile illnesses as controls. Mitogenic activity in culture supernatants obtained from individual bacterial strains was measured by lymphocyte proliferation assay. Sixty-one bacterial strains were isolated from KD patients, and 62 strains from control patients. There was no apparent difference in bacterial species in the throat flora between KD patients and febrile controls. Moreover, total and individual mitogenic activity of strains from KD patients was no greater than that of strains from febrile controls. The bacterial superantigen activity of throat flora may not play a major role in the pathogenesis of KD.

The Involvement of Bacterial Products from Throat Flora in the Pathogenesis of Kawasaki Disease

Kawasaki disease (KD) is an acute vasculitis of unknown etiology, however, some studies suggest that superantigens are involved in its pathogenesis. To clarify an association between KD and bacterial infection, we studied bacterial culture supernatants from throat flora of acute stage KD patients for mitogenic activity. Twenty-five individual bacterial strains (Streptococcus sp., Stapylococcus sp., Neisseria sp., Pseudomonas sp. etc) were isolated from throat of nine acute-stage KD patients before treatments. Each of these bacterial strains was cultured overnight at 37centigrade in trypticase soy broth. Bacterial cells were removed by centrifugation and filtration with a 0.22μm pore size filter. The mitogenic activity in the supernatants was determined by a three-day lymphocyte assay. Fresh peripheral blood mononuclear cells (PBMC) were obtained by ficoll-paque centrifugation of heparinized blood from healthy adult. PBMC were cultured in RPMI 1640 containing 10% heat-inactivated fetal bovine serum. The bacterial culture supernatant (10μL) was added to the PBMC culture (105 cells in 0.1 mL of culture medium) and then cultured in each well of a 96-well microplate at 37centigrade in 5% CO2. Proliferation of PBMC was determined three days after by morphological observation and Cell Counting Kit-8 (Dojin Chemical). The mitogenic activity for human lymphocytes was observed in three of twenty-five supernatants. The three supernatants were contained two strains of S. pyogenes and one strain of methicillin-resistant S. aureus. The results indicate that at least three of nine acute-stage KD patients had bacteria producing mitogenic products in throat flora. These findings support the involvement of mitogenic products, such as superantigens, of group A streptococci and S. aureus in the pathogenesis of KD.

Erythromycin susceptibility of viridans streptococci from the normal throat flora of patients treated with azithromycin or clarithromycin

Objective To study the emergence of macrolide resistance in throat flora following treatment with clarithromycin or azithromycin.Methods Throat samples were collected before and after treatment and plated as a lawn on Columbia blood agar with an erythromycin E test strip. Minimum inhibitory concentrations (MICs) of erythromycin, clarithromycin and azithromycin were determined against isolates of distinct morphology with erythromycin E test MIC results equal to or greater than 2 mg/L. Polymerase chain reaction techniques were used to determine the genetic mechanisms of resistance.Results There were 749 resistant isolates of which 474 (63%) were streptococci. Only a quarter of the patients had no resistant streptococci before treatment started. There were increases in the numbers of resistant isolates and in the number of patients carrying a resistant flora during and after treatment. The most common genes identified were mefA/E in isolates with low-level resistance and ermA/M in isolates with high-level resistance.Conclusions There is a pool of streptococci carrying genes associated with macrolide resistance in the normal respiratory flora of generally healthy adults. Differences between the patients treated with clarithromycin and those treated with azithromycin were difficult to assess because of the large number of patients in each group with macrolide-resistant streptococci before treatment. Although there were some differences these were not statistically significant.

Sulphonamide resistant commensal Neisseria with alterations in the dihydropteroate synthase can be isolated from carriers not exposed to sulphonamides

BackgroundDevelopment of sulphonamide resistance in Neisseria meningitidis has been suggested to involve horizontal DNA-transfer from a commensal Neisseria species. In this study, we isolated commensal Neisseria from throat specimens and examined the isolates with respect to sulphonamide resistance.ResultsThree resistant clones were identified and the resistance phenotype could be explained by amino acid variations in their dihydropteroate synthase, the target molecule for sulphonamides. Some of these variations occurred in positions corresponding to previously detected variations in resistant N. meningitidis.ConclusionsSulphonamide resistant commensal Neisseria were isolated from an environment not exposed to sulphonamides, suggesting that resistant Neisseria has become a natural part of the commensal throat flora.

Antibiotic use and pneumococcal resistance to penicillin: the French experience

Antibiotic use and pneumococcal resistance to penicillin: the French experience

Clinico-bacteriological study of pyodermas in children.

One hundred cases of pyodermas in children were investigated clinically and bacteriologically. Nasal and throat swabs from all cases were subjected to bacteriological examination. Most of the children (42%) were in the 1-4 year age group. The majority (58%) belonged to lower socio-economic groups with poor standards of hygiene. A history of over-crowding was obtained from 87% of cases, 82% were undernourished. Most of the children (68%) reported during the hot and humid months of June, July, August, and September. Primary pyodermas were observed in 72% of the children, and secondary pyodermas in 28%. Impetigo was the commonest primary pyoderma (48.61%); among secondary pyodermas, infected scabies was noted predominantly (42.86%). The face and legs were more commonly involved. Bacteriological cultures from pyoderma lesions revealed a single microorganism in the majority of the patients (84%). Staphylococcus aureus was isolated in pure culture from 48% and pure beta-hemolytic streptococci from 36%. A combination of both was obtained from 16%. No other organism was isolated from any case. A similar pattern was also observed in cultures from the nose and throat. Only 46 out of the 64 strains (84.3%) of Staphylococcus aureus isolated from pyoderma were typable. The majority (39.1%) showed a mixed pattern of phages; the second commonest was the non-allocated phage type (30.4%). Nasal flora had more of the non-allocated phage type (50%); two out of the three strains (66.6%) isolated from the throat showed a mixed pattern. All the strains of beta hemolytic streptococci, isolated either from lesions of pyoderma, nose, or throat belonged to group A. Staphylococcus aureus and showed a high sensitivity to netilmycin (100%), ofloxacin (98.4%), amoxycillin/clavulanic acid (96.9%), ciprofloxacin (89.1%) and gentamycin (84.4%) but a high resistance to penicillin (85.9%). A greater correlation was noted between nasal flora and organisms causing pyodermas. A change in the pattern of organisms causing pyodermas in children and their antibiotic sensitivities in this part of the globe has been observed in this study. The role of endogenous nasal and throat flora in the causation of pyodermas has also been highlighted.

Tonsillar Microbial Flora: Comparison of Recurrent Tonsillitis and Normal Tonsils

Tonsillar microbial flora was studied in cultures of tonsillar core specimens from 34 patients tonsillectomized due to recurrent group A streptococcal pharyngotonsillitis (n=17) or sleep apnoea (n=17). Patients in the sleep apnoea subgroup, who had no history of recurrent tonsillitis and manifested no tonsillar hypertrophy at ENT examination, served as controls. Tonsillar core specimens were cultured for semi-quantitative estimation of growth of aerobic, anaerobic and facultative organisms. The recurrent tonsillitis and apnoea subgroups did not differ significantly in the mean number of isolates per patient, either of aerobic spp. (3.8 vs. 4.3) or anaerobic spp. (5.2 vs. 4.7). Nor did the two subgroups differ significantly in the proportion of patients whose specimens manifested beta-lactamase producers (71% vs. 59%), in the isolation frequency of viridans (alpha) streptococci, or in the occurrence of semi-quantitative growth estimates of 3-4+ for aerobic, anaerobic or beta-lactamase-producing spp. Thus, the study provided no support for the hypothesis that inactivation of penicillin V by beta-lactamase-producing bacteria in oral or throat flora, or the eradication of viridans streptococci with their GAS-inhibitory capacity, is an important factor with regard to recurrent group A streptococcal tonsillitis. Other possible explanations, such as poor antibiotic penetration at the site of infection, are discussed.

Pathogenicity of Hansenula anomala in model of immunocompromised mice.

Systemic infections caused by opportunistic fungi have shown an increased frequency in the past 10 years, particularly in immunocompromised patients. Hansenula anomala is an ascosporogenous yeast of the Ascomycetes class found in the skin, throat, and digestive tract transient normal flora. This study was conducted to compare the pathogenicity of H. anomala and Candida albicans in a model of immunocompromised mice. Thirty-eight Swiss mice were divided into two groups as follows: 30 animals received an intraperitoneal (i.p.) injection of cyclophosphamide (200 mg/kg) four days before the induction of infection with H. anomala (1 x 10(6) yeasts/mL), and 8 animals received 100 mg/kg of cyclophosphamide at 3-day intervals during 3 weeks before inoculation of 1 x 10(7) yeasts/mL. All animals were treated with amoxicillin/clavulanic acid (40 mg/kg) four days before induction of infection. A group of mice inoculated with C. albicans (ATCC 64548) served as control. Tissue samples from the lung, spleen, liver, and kidney for histological and mycologic studies were obtained at necropsy. In each animal, the number of viable yeasts per gram of kidney was determined. The organs most frequently infected by H. anomala were the kidneys and the liver (20%), and the lung (10%). However, in conditions of sustained immunosuppression, H. anomala was found in 65.5% of the organs examined. It is concluded that in an experimental model of immunocompromised mice, the pathogenicity of H. anomala was low.

Commensal relationship between group a streptococci and Neisseria Subflava

This study was carried out in a laboratory to examine the relationship between group A streptococci and Neisseria subflava. The study consisted of the following: a. A comparison of the growth of streptococci in pure versus mixed culture. b. The addition of cell‐free extracts from the Neisseria cultures as supplements to the streptococci growth media. c. The addition of measured quantities of riboflavin in the Streptococcus culture medium. The results of this investigation show that the presence of Neisseria subflava in a mixed culture enhances the growth of Streptococcus pyogenes. The group A streptococci are capable of causing clinical infection of the throat or skin in man. As a consequence, individuals having Neisseria subflava within their normal throat flora may be more susceptible to Streptococcal throat infections. The study of the interaction of the Neisseria‐Streptococcus indicates that in the presence of Neisseria subflava the generation time of Streptococcus pyogenes is significantly decreased. It appears that the growth of Neisseria subflava in the environment furnishes the nutritional factor riboflavin (vitamin B2) which is responsible for lowering the generation time of the group A streptococci.