Prediction of risk factors of bronchial mucus plugs in children with Mycoplasma pneumoniae pneumonia.

BACKGROUND: Recently, many cases of pneumonia in children with Mycoplasma pneumoniae infection have been shown to have varying degrees of intrabronchial mucus plug formation. The clinical, laboratory, radiological characteristics, and treatment of patients with Mycoplasma infection are analyzed in this study. The risk factors for M. pneumoniae pneumonia (MPP) mucus plug formation in children are explored, and a risk factor scoring system is established. METHODS: MPP patients treated with bronchoscopy were retrospectively enrolled in the study from February 2015 to December 2019. The children were divided into a mucus plug group and a control group according to the presence or absence of mucus plug formation. The clinical, laboratory, radiological characteristics, and treatment of the two groups of children were compared. Univariate and multivariate logistic regression models were used to identify the risk factors for MPP mucus plug formation. The receiver operating characteristic (ROC) curve was drawn to evaluate the regression model and establish the MPP mucous plug risk factor scoring system. RESULTS: A univariate analysis showed that the children in the mucous group were older and had a longer fever duration, longer hospital stay, higher fever peak, more cases of wheezing symptoms and allergies, and azithromycin or corticosteroids were administered later. In addition, neutrophil, C-reactive protein (CRP), lactate dehydrogenase (LDH), D-dimer (DD), sputum MP-DNA copy number, and total immunoglobulin A (IgA) levels were higher, while prealbumin (PA) levels were lower. The ROC curve analysis showed that children with MPP had PA ≤144.5 mg/L, had used corticosteroids during the course of the illness of ≥4.5 days, CRP ≥12.27 mg/L, an LDH ≥ 462.65 U/L, and there was a possibility of intra-airway mucus formation. The independent risk factors were scored according to their odds ratio (OR) value. Among the 255 children with MPP, the high-risk group had 44 (83.02%) mucus plugs out of 53; the middle-risk group had 35 (34.3%) mucus plugs out of 102; and the low-risk group had 11 (11%) mucus plugs out of 100. CONCLUSIONS: PA levels, timing of corticosteroid use (use in the first few days), CRP levels, and LDH levels were independent risk factors for MPP mucus plug formation. This provides a basis for the early identification of MPP in children combined with mucus plug formation.

Effects of a combination of erythromycin sequential therapy and azithromycin on lung function and inflammatory factors in children with severe mycoplasma pneumonia.

This study aimed to investigate the effect of erythromycin sequential therapy plus azithromycin on lung function and inflammatory factors in children with severe mycoplasma pneumonia (MP). Ninety-three severe MP children were selected and randomized into azithromycin group, erythromycin group, and combination group, 31 cases in each. The disappearance time of cough, fever, lung rale and X-ray shadow in the combination group were shorter than those in the azithromycin group and erythromycin group. The clinical treatment efficiency of the combination group was higher than that of the azithromycin group. After treatment, FVC, FEV1/FVC and PEF in combination group were higher than before treatment; IL-8, IL-6, CRP in combination group were lower than erythromycin group and azithromycin group. IL-8, IL-6, CRP are negatively correlated with disappearance time of cough, fever, pulmonary rale, X-ray shadow and clinical treatment efficiency; FEV1/FVC is positively correlated with disappearance time of cough and fever, pulmonary rales and X-ray shadow, and clinical treatment efficiency. Sequential erythromycin therapy combined with azithromycin in the treatment of MP can effectively inhibit high inflammatory reactions, control the disease in a timely manner, improve lung function and produce fewer adverse reactions.

Human adenovirus Coinfection aggravates the severity of Mycoplasma pneumoniae pneumonia in children.

BACKGROUND: Mycoplasma pneumoniae (M. pneumoniae) is an important pathogen of community-acquired pneumonia (CAP) in children. The coinfection rate of M. pneumoniae pneumonia (MPP) can reach 52% in some areas, but the effects of coinfection with different pathogens have not been clearly recognized. METHODS: The cases of MPP hospitalized in Beijing Children's Hospital from 1/1/2014 to 12/31/2016 were screened. MPP patients coinfected with Human adenovirus (HAdV) were categorized into the research group. Patients with single M. pneumoniae infection were categorized into the control group, matching the research group by age and admission time with a ratio of 1:3. Clinical manifestations, laboratory examinations, and disease severity were compared between these two groups. RESULTS: A total of 2540 hospitalized MPP cases were screened in Beijing Children's Hospital, among which thirty cases were enrolled in the research group and ninety cases were enrolled in the control group. The results indicated that patients in the research group had longer hospital stays, longer fever durations and a higher rate of dyspnea, as well as a larger proportion applications of oxygen therapy and noninvasive continuous positive airway pressure (NCPAP). No obvious differences were found in lab examinations within the two groups. Regarding disease severity, the proportions of extremely severe pneumonia and severe disease defined by the clinical score system were higher in the research group than in the control group. CONCLUSION: Compared with single M. pneumoniae infection, MPP coinfected with HAdV in children was relatively more serious.

Bovine Epithelial in vitro Infection Models for Mycoplasma bovis.

Mycoplasma bovis causes bovine mycoplasmosis. The major clinical manifestations are pneumonia and mastitis. Recently an increase in the severity of mastitis cases was reported in Switzerland. At the molecular level, there is limited understanding of the mechanisms of pathogenicity of M. bovis. Host-pathogen interactions were primarily studied using primary bovine blood cells. Therefore, little is known about the impact of M. bovis on other cell types present in infected tissues. Clear in vitro phenotypes linked to the virulence of M. bovis strains or tissue predilection of specific M. bovis strains have not yet been described. We adapted bovine in vitro systems to investigate infection of epithelial cells with M. bovis using a cell line (MDBK: Madin-Darby bovine kidney cells) and two primary cells (PECT: bovine embryonic turbinate cells and bMec: bovine mammary gland epithelial cells). Two strains isolated before and after the emergence of severe mastitis cases were selected. Strain JF4278 isolated from a cow with mastitis and pneumonia in 2008 and strain L22/93 isolated in 1993 were used to assess the virulence of M. bovis genotypes toward epithelial cells with particular emphasis on mammary gland cells. Our findings indicate that M. bovis is able to adhere to and invade different epithelial cell types. Higher titers of JF4278 than L22/93 were observed in co-cultures with cells. The differences in titers reached between the two strains was more prominent for bMec cells than for MDBK and PECT cells. Moreover, M. bovis strain L22/93 induced apoptosis in MDBK cells and cytotoxicity in PECT cells but not in bMec cells. Dose-dependent variations in proliferation of primary epithelial cells were observed after M. bovis infection. Nevertheless, an indisputable phenotype that could be related to the increased virulence toward mammary gland cells is not obvious.

Clinical and histologic features of Mycoplasma pneumoniae-related erythema multiforme: A single-center series of 33 cases compared with 100 cases induced by other causes.

BACKGROUND: Mycoplasma pneumoniae infection has been documented in erythema multiforme (EM) and Stevens-Johnson syndrome-toxic epidermal necrosis (SJS-TEN). Clinical aspects of M pneumoniae-related EM have been poorly described in the literature. OBJECTIVE: To highlight differences between M pneumoniae EM and non-M pneumoniae EM. METHODS: This single-center, retrospective cohort study included all patients admitted to our dermatology department for EM during 2000-2015. We compared epidemiologic, clinical, and histologic data and follow-up for M pneumoniae EM and non-M pneumoniae EM cases. RESULTS: Thirty-three patients with M pneumoniae EM were compared with 100 patients with non-M pneumoniae EM. Disease onset in winter was more frequent with M pneumoniae EM (P = .003). Acrally distributed lesions (32% vs 88%, P < .0001) and typical targets (45% vs 74%, P = .01) were less common in M pneumoniae EM than non-M pneumoniae EM. Multiple (≥2) mucousal membrane involvement was more frequent in M pneumoniae EM than non-M pneumoniae EM (97% vs 60%; P < .0001), as were mucosal and respiratory tract sequelae (P < .05). The mean hospital stay was longer with M pneumoniae EM patients: 9.5 days versus 5.1 days (P = .0002). A TEN-like pattern was observed in all 14 (100%) M pneumoniae EM skin biopsies versus 10 of 27 (48%) non-M pneumoniae EM biopsies (P < .001). LIMITATIONS: The retrospective design. CONCLUSION: M pneumoniae EM has a distinctive presentation compared with non-M pneumoniae EM, with more diffuse and atypical targets, more mucositis and respiratory tract sequelae. Histologic data show a TEN-like pattern in all M pneumoniae EM skin samples.

Neurological Manifestations of Mycoplasma pneumoniae Infection in Hospitalized Children and Their Long-Term Follow-Up.

Objective In this retrospective study, we aimed to assess frequency, types, and long-term outcome of neurological disease during acute Mycoplasma pneumoniae (M. pneumoniae) infection in pediatric patients. Materials and Methods Medical records of patients hospitalized with acute M. pneumoniae infection were reviewed. Possible risk factors were analyzed by uni- and multivariate regression. Patients with neurological symptoms were followed up by expanded disability status score (EDSS) and the cognitive problems in children and adolescents (KOPKJ) scale. Results Out of 89 patients, 22 suffered from neurological symptoms and signs. Neurological disorders were diagnosed in 11 patients: (meningo-) encephalitis (n = 6), aseptic meningitis (n = 3), transverse myelitis (n = 1), and vestibular neuritis (n = 1), 11 patients had nonspecific neurological symptoms and signs. Multivariate logistic regression identified lower respiratory tract symptoms as a negative predictor (odds ratio [OR] = 0.1, p < 0.001), a preexisting immune deficit was associated with a trend for a decreased risk (OR = 0.12, p = 0.058). Long-term follow-up after a median of 5.1 years (range, 0.6-13 years) showed ongoing neurological deficits in the EDSS in 8/18, and in the KOPKJ in 7/17. Conclusion Neurological symptoms occurred in 25% of hospitalized pediatric patients with M. pneumoniae infection. Outcome was often favorable, but significant sequels were reported by 45%.

An Atypical Case of Hemoptysis.

Hemoptysis, a common sign of diffuse alveolar hemorrhage, can be caused by multiple factors, both infectious and noninfectious. A 45-year-old male with hypertension, obstructive sleep apnea, and stage IV pulmonary sarcoidosis with cardiac involvement, presented with a two-month history of cough and acute nonmassive hemoptysis with hypoxia. A chest CT showed ground glass consolidation and interlobular septal thickening, concerning for diffuse alveolar hemorrhage. Flexible bronchoscopy confirmed diffuse alveolar hemorrhage; microbiological analyses of bronchoalveolar washings did not reveal a causative organism. Mycoplasma pneumoniae-specific IgM in serum studies was consistent with mycoplasma pneumonia as the most likely etiology of this patient's diffuse alveolar hemorrhage and resultant hemoptysis. This report points to the need to consider atypical mycoplasma pneumonia as a possible etiology of hemoptysis in patients with underlying sarcoidosis.

EEG extreme delta brush: An ictal pattern in patients with anti-NMDA receptor encephalitis.

INTRODUCTION: The anti-NMDA receptor (NMDAr) encephalitis-associated syndrome includes neuropsychiatric symptoms, impaired consciousness, seizures, autonomic instability, and hypoventilation. The electroencephalographic (EEG) activity throughout the course of the disease has still not been well documented. We reviewed electroclinical data of patients with NMDAr encephalitis to characterize their EEG and its clinical correlation. MATERIAL AND METHODS: We retrospectively identified 16 patients with NMDAr encephalitis from 8 Spanish medical centers, 15 of whom underwent video-EEG in the acute phase. RESULTS: In 15 patients (11 females, median age: 37.4, range: 14-87 years), seizures occurred in 9 (60%) and status epilepticus (SE) in 5 (33.3%). Magnetic resonance imaging (MRI) was abnormal in 10 (66.6%), and CSF (cerebrospinal fluid) was normal in 3 and abnormal in 12, with positive PCR (polymerase chain reaction) for Mycoplasma pneumoniae (1/15) and herpes simple virus (1/15). An ovarian teratoma was found in 1 patient and other malignancies (small cell lung carcinoma) in 1 patient. The EEG was abnormal in the acute phase in 14/15 (93.3%). Extreme delta brush (EDB) was observed in 5 (33.3%), and the presence of EDB was associated with SE in all cases. Rhythmic delta activity without EDB was observed in 5 (33.3%), while excessive beta activity was present in 4 (26.6%). Extreme delta brush can follow a pattern of well-characterized electroclinical seizures. CONCLUSIONS: Almost invariably, patients with NMDAr encephalitis had abnormal EEG. The presence of EDB, which can follow a pattern of well-characterized electroclinical seizures, in our patients was associated with seizures and SE. These findings suggest that EDB could be an evolutive pattern of an SE in NMDAr encephalitis. This article is part of a Special Issue entitled "Status Epilepticus".

[Clinical efficacy of adjuvant therapy with glucocorticoids in children with lobar pneumonia caused by Mycoplasma pneumoniae].

OBJECTIVE: To study the clinical efficacy of adjuvant therapy with glucocorticoids in children with lobar pneumonia caused by Mycoplasma pneumoniae. METHODS: One hundred and eight children with lobar pneumonia caused by Mycoplasma pneumoniae were randomly divided into routine treatment and hormone treatment groups. Both groups were treated with azithromycin and other symptomatic therapies. In addition to the basic treatment, the hormone treatment group was given dexamethasone 0.25-0.3 mg/(kg·d) by intravenous drip until the body temperature was normal. Then given oral prednisone tablets 0.5-1 mg/(kg·d) (gradually reduced) for a total treatment course of 7-10 days. Before and after treatment pulmonary functions were examined, and serum C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), interleukin-2 (IL-2) and interleukin-6 (IL-6) were measured. RESULTS: The duration of fever, cough relief time and pulmonary shadow absorption time on chest X-ray were significantly shorter in the hormone treatment group than in the routine treatment group (P<0.05). After treatment, the two groups showed improvements in serum CRP, ESR, IL-2, and IL-6 (P<0.05), but the hormone treatment group showed significantly more improvement (P<0.05). Varying degrees of mixed ventilation dysfunction were seen in the two groups before treatment, and hormone therapy significantly improved pulmonary function, especially promoting the recovery of small airway function. CONCLUSIONS: Adjuvant therapy with glucocorticoids can effectively alleviate clinical symptoms, promote the absorption of pulmonary inflammation, and improve pulmonary function in children with lobar pneumonia caused by Mycoplasma pneumoniae.

Mast cell TNF receptors regulate responses to Mycoplasma pneumoniae in surfactant protein A (SP-A)-/- mice.

BACKGROUND: Mycoplasma pneumoniae (Mp) frequently colonizes the airways of patients with chronic asthma and likely contributes to asthma exacerbations. We previously reported that mice lacking surfactant protein A (SP-A) have increased airway hyperresponsiveness (AHR) during M pneumoniae infection versus wild-type mice mediated by TNF-α. Mast cells (MCs) have been implicated in AHR in asthma models and produce and respond to TNF-α. OBJECTIVE: Determine the contribution of MC/TNF interactions to AHR in airways lacking functional SP-A during Mp infection. METHODS: Bronchoalveolar lavage fluid was collected from healthy and asthmatic subjects to examine TNF-α levels and M pneumoniae positivity. To determine how SP-A interactions with MCs regulate airway homeostasis, we generated mice lacking both SP-A and MCs (SP-A(-/-)Kit(W-sh/W-sh)) and infected them with M pneumoniae. RESULTS: Our findings indicate that high TNF-α levels correlate with M pneumoniae positivity in human asthmatic patients and that human SP-A inhibits M pneumoniae-stimulated transcription and release of TNF-α by MCs, implicating a protective role for SP-A. MC numbers increase in M pneumoniae-infected lungs, and airway reactivity is dramatically attenuated when MCs are absent. Using SP-A(-/-)Kit(W-sh/W-sh) mice engrafted with TNF-α(-/-) or TNF receptor (TNF-R)(-/-) MCs, we found that TNF-α activation of MCs through the TNF-R, but not MC-derived TNF-α, leads to augmented AHR during M pneumoniae infection when SP-A is absent. Additionally, M pneumoniae-infected SP-A(-/-)Kit(W-sh/W-sh) mice engrafted with TNF-α(-/-) or TNF-R(-/-) MCs have decreased mucus production compared with that seen in mice engrafted with wild-type MCs, whereas burden was unaffected. CONCLUSION: Our data highlight a previously unappreciated but vital role for MCs as secondary responders to TNF-α during the host response to pathogen infection.

In vivo function of airway epithelial TLR2 in host defense against bacterial infection.

Decreased Toll-like receptor 2 (TLR2) expression has been reported in patients with chronic obstructive pulmonary disease and in a murine asthma model, which may predispose the hosts to bacterial infections, leading to disease exacerbations. Since airway epithelial cells serve as the first line of respiratory mucosal defense, the present study aimed to reveal the role of airway epithelial TLR2 signaling to lung bacterial [i.e., Mycoplasma pneumoniae (Mp)] clearance. In vivo TLR2 gene transfer via intranasal inoculation of adenoviral vector was performed to reconstitute TLR2 expression in airway epithelium of TLR2(-/-) BALB/c mice, with or without ensuing Mp infection. TLR2 and lactotransferrin (LTF) expression in airway epithelial cells and lung Mp load were assessed. Adenovirus-mediated TLR2 gene transfer to airway epithelial cells of TLR2(-/-) mice reconstituted 30-40% TLR2 expression compared with TLR2(+/+) cells. Such airway epithelial TLR2 reconstitution in TLR2(-/-) mice significantly reduced lung Mp load (an appropriate 45% reduction), coupled with elevated LTF expression. LTF expression in mice was shown to be mainly dependent on TLR2 signaling in response to Mp infection. Exogenous human LTF protein dose-dependently decreased lung bacterial load in Mp-infected TLR2(-/-) mice. In addition, human LTF protein directly dose-dependently decreased Mp levels in vitro. These data indicate that reconstitution of airway epithelial TLR2 signaling in TLR2(-/-) mice significantly restores lung defense against bacteria (e.g., Mp) via increased lung antimicrobial protein LTF production. Our findings may offer a deliverable approach to attenuate bacterial infections in airways of asthma or chronic obstructive pulmonary disease patients with impaired TLR2 function.

Pathogenesis of extrapulmonary manifestations of Mycoplasma pneumoniae infection with special reference to pneumonia.

Although pneumonia has been a hallmark of Mycoplasma pneumoniae infection, it has been revealed that this infection can cause a number of extrapulmonary manifestations in the absence of pneumonia. While the host immune response has been implicated in the pathomechanism of pneumonia, the pathomechanisms of extrapulmonary manifestations remain largely unknown. It is proposed in this review that extrapulmonary manifestations due to M. pneumoniae infection can be classified into three categories; the first is a direct type in which inflammatory cytokines locally induced by lipoproteins contained in the bacterial cell membrane must play a role, the second is an indirect type in which immune modulation such as autoimmunity through cross-reaction between the bacterial cell components and human cells must play a role, and the third is a vascular occlusion type in which vasculitis and/or thrombosis with or without systemic hypercoagulable state induced by the bacterium must play a role. Based on this classification, a literature review was carried out for extrapulmonary manifestations due to M. pneumoniae infection with special reference to pneumonia, including cardiovascular, dermatological, digestive organ, hematological/hematopoietic system, musculoskeletal, sensory organ, and urogenital tract manifestations. Consequently, most extrapulmonary manifestations due to M. pneumoniae infection can be reasonably classified into and explained by one of the three types of pathomechanisms mentioned above. Noticeably in this review, Kawasaki disease and infectious mononucleosis in association with M. pneumoniae infection, which are not unusual in Japan but have seldom been reported from Western countries, are included in the panel of extrapulmonary manifestations due to M. pneumoniae infection.

Mycoplasma pneumoniae infection complicated by pneumomediastinum and severe mucositis.

We report an 8-year-old boy with Mycoplasma pneumoniae respiratory infection complicated by pneumomediastinum and severe oral and conjunctival mucositis. M. pneumoniae-associated mucositis is distinct from the Stevens-Johnson syndrome. There are no skin lesions and it improves promptly with antibiotics. Spontaneous pneumomediastinum usually only requires rest, analgesia and management of the underlying condition.

Matrix metalloproteinase-2 and -9 expression increases in Mycoplasma-infected airways but is not required for microvascular remodeling.

Murine Mycoplasma pulmonis infection induces chronic lung and airway inflammation accompanied by profound and persistent microvascular remodeling in tracheobronchial mucosa. Because matrix metalloproteinase (MMP)-2 and -9 are important for angiogenesis associated with placental and long bone development and skin cancer, we hypothesized that they contribute to microvascular remodeling in airways infected with M. pulmonis. To test this hypothesis, we compared microvascular changes in airways after M. pulmonis infection of wild-type FVB/N mice with those of MMP-9(-/-) and MMP-2(-/-)/MMP-9(-/-) double-null mice and mice treated with the broad-spectrum MMP inhibitor AG3340 (Prinomastat). Using zymography and immunohistochemistry, we find that MMP-2 and MMP-9 rise strikingly in lungs and airways of infected wild-type FVB/N and C57BL/6 mice, with no zymographic activity or immunoreactivity in MMP-2(-/-)/MMP-9(-/-) animals. However, microvascular remodeling as assessed by Lycopersicon esculentum lectin staining of whole-mounted tracheae is as severe in infected MMP-9(-/-), MMP-2(-/-)/MMP-9(-/-) and AG3340-treated mice as in wild-type mice. Furthermore, all groups of infected mice develop similar inflammatory infiltrates and exhibit similar overall disease severity as indicated by decrease in body weight and increase in lung weight. Uninfected wild-type tracheae show negligible MMP-2 immunoreactivity, with scant MMP-9 immunoreactivity in and around growing cartilage. By contrast, MMP-2 appears in epithelial cells of infected, wild-type tracheae, and MMP-9 localizes to a large population of infiltrating leukocytes. We conclude that despite major increases in expression, MMP-2 and MMP-9 are not essential for microvascular remodeling in M. pulmonis-induced chronic airway inflammation.

Elevated cytokine and chemokine levels and prolonged pulmonary airflow resistance in a murine Mycoplasma pneumoniae pneumonia model: a microbiologic, histologic, immunologic, and respiratory plethysmographic profile.

Because Mycoplasma pneumoniae is hypothesized to play an important role in reactive airway disease/asthma, a comprehensive murine model of M. pneumoniae lower respiratory infection was established. BALB/c mice were intranasally inoculated once with M. pneumoniae and sacrificed at 0 to 42 days postinoculation. All mice became infected and developed histologic evidence of acute pulmonary inflammation, which cleared by 28 days postinoculation. By contrast, M. pneumoniae persisted in the respiratory tract for the entire 42 days studied. Tumor necrosis factor alpha, gamma interferon, interleukin-6 (IL-6), KC (functional IL-8), MIP-1alpha, and MCP-1/JE concentrations were significantly elevated in bronchoalveolar lavage samples, whereas IL-4 and IL-10 concentrations were not significantly elevated. Pulmonary airflow resistance, as measured by plethysmography, was detected 1 day postinoculation and persisted even after pulmonary inflammation had resolved at day 28. Serum anti-M. pneumoniae immunoglobulin G titers were positive in all mice by 35 days. This mouse model provides a means to investigate the immunopathogenesis of M. pneumoniae infection and its possible role in reactive airway disease/asthma.

Acute childhood encephalitis and Mycoplasma pneumoniae.

In a prospective 5-year study of children with acute encephalitis, evidence of Mycoplasma pneumoniae infection was demonstrated in 50 (31%) of 159 children. In 11 (6.9%) of these patients, M. pneumoniae was determined to be the probable cause of encephalitis on the basis of its detection in cerebrospinal fluid (CSF) by polymerase chain reaction (PCR) or by positive results of serologic tests for M. pneumoniae and detection of the organism in the throat by PCR. CSF PCR positivity correlated with a shorter prodromal illness (P=.015) and lack of respiratory symptoms (P=.06). Long-term neurologic sequelae occurred in 64% of probable cases. Thirty children (18.9%) who were seropositive for M. pneumoniae but did not have the organism detected by culture or PCR had convincing evidence implicating other organisms as the cause of encephalitis, suggesting that current serologic assays for M. pneumoniae are not sufficiently specific to establish a diagnosis of M. pneumoniae encephalitis.

Frequency of serological evidence of Bordetella infections and mixed infections with other respiratory pathogens in university students with cough illnesses.

Banked acute-phase and convalescent-phase serum samples from a previous study of respiratory illness in university students were examined for significant (>/=2-fold) increases in ELISA titers of IgA and IgG antibody to Bordetella pertussis filamentous hemagglutinin, pertactin, and fimbriae-2 and >/=4-fold titer increases to agglutinogens by agglutination. ELISA titers of antibody to pertussis toxin could not be determined because of technical problems. Chlamydia pneumoniae infections were diagnosed by culture or by a >/=4-fold increase in immunofluorescence assay titer or a single high titer (>/=512). Mycoplasma pneumoniae, influenza A and B, adenovirus, and respiratory syncytial virus infections were diagnosed by >/=4-fold increases in complement fixation titer or a single high titer (>/=64). There were 319 subjects with cough of >/=5 days' duration, and of these, 47 (15%) had significant increases in antibody to B. pertussis antigens; 26 (8%) had significant increases to fimbriae-2 or agglutinogens, indicative of B. pertussis infection, and 2 (1%) had evidence of non-B. pertussis bordetella infections. Seventeen (36%) had evidence of mixed infections or cross-reacting antibodies (influenza B infections, 5; adenovirus infections, 4; influenza A infections, 3; C. pneumoniae infections, 3; and M. pneumoniae infections, 2). Our findings suggest that bordetella infections are common in young adults with cough illnesses (incidence, 9%), and a surprising number of these are mixed infections with other respiratory pathogens.