Investigation of isoniazid and ethionamide cross-resistance by whole genome sequencing and association with poor treatment outcomes of multidrug-resistant tuberculosis patients in South Africa.

OBJECTIVE/BACKGROUND: Ethionamide (ETH) and isoniazid (INH) are part of the backbone regimen used for the treatment of multidrug-resistant tuberculosis (MDR-TB). Both ETH and INH are structurally similar and are activated by ethA and katG gene products. Resistance to INH among MDR-TB patients may cause ETH to be ineffective, as both target nicotinamide adenine dinucleotide-dependent enoyl-acyl carrier protein reductase inhA protein and mutations within inhA gene may lead to their cross-resistance. Furthermore, ETH resistance is caused by mutations within ethA and ethR genes forming part of the ETH drug activation pathway. Nicotinamide adenine dinucleotide is coded by the ndh gene, and its overexpresion may lead cross-resistance between INH and ETH drugs. Phenotypic drug susceptibility testing of ETH is difficult and often unreliable. We used whole genome sequencing to compare inhA, inhA promoter, ethA, ethR ndh, and katG genetic regions in serial isolates (baseline and follow-up) with treatment outcomes. METHODS: MDR-TB strains were collected from 46 patients before and during second-line drug treatment in KwaZulu-Natal and Eastern Cape between 2005 and 2009. All patients had phenotypically determined MDR-TB at baseline and had treatment outcomes documented. Unfavorable treatment outcomes were defined as death, default, and failure, while favorable outcomes were cure and treatment completion. Each strain had baseline and at least one strain collected on follow-up. From each strain, DNA was extracted from colonies grown on Löwenstein-Jensen slants, and fragment and jumping paired-end Illumina DNA libraries were constructed and sequenced on the Illumina HiSeq 2000 (Broad Institute, Cambridge, MA, USA). Sequences were aligned to H37Rv genome and Pilon was run to generate a list of SNPs. In silico spoligotyping was performed to a database 43 unique spacer sequences. Cross-resistance was defined as the presence of both inhA and either ethA or ethR mutations in clinical isolates. RESULTS: A total of 92 sequences from 46 serial isolates of MDR-TB patients from KwaZulu-Natal (29 isolates) and Eastern Cape (17 isolates) were analyzed. Most patients (29/46; 63.0%) had unfavorable outcomes, 13 (28.3%) had favorable outcomes, while four (8.7%) had unknown outcomes. Phylogenetic reconstruction revealed that primary genotype differed by province. The Beijing genotype was predominant in Eastern Cape, while EuroAmerican lineage (S, T, LAM, X) was found in KwaZulu-Natal. Whole genome analysis revealed nonsynonymous insertions and deletions within katG, ethA, ethR, ndh, and inhA and its promoter region. Among patients with treatment outcome data, mutations were detected in 92.8% in katG, 50% in inhA, 53.6% in ethA, 2.4% in ethR, and 19% in ndh. The majority of mutations causing ETH (20/29; 68.9%) and INH (18/29; 62.1%) resistance occurred among patients with unfavorable outcomes. Both inhA and either ethA or ethR mutations were detected in 16/29 (55.2%) patients with unfavorable outcomes. Cross-resistance of both INH and ETH drugs was associated with unfavorable treatment outcomes (p=0.021) in 16/29 (55.2%) patients compared with favorable treatment outcomes in 2/13 (15.4%) patients. CONCLUSION: Baseline ETH molecular resistance before second-line treatment is a concern. Unfavorable treatment outcomes of patients with ethA, ethR, and inhA mutations highlight the importance of genotypic testing before initiation of treatment containing ETH. The clinical significance of whole genome analysis for early detection of mutations predictive of treatment failure needs further investigation.

Community-based care vs. centralised hospitalisation for MDR-TB patients, KwaZulu-Natal, South Africa.

SETTING: KwaZulu-Natal, South Africa, a predominantly rural province with a high burden of tuberculosis (TB), multidrug-resistant TB (MDR-TB) and human immunodeficiency virus (HIV) infection. OBJECTIVE: To determine the most effective care model by comparing MDR-TB treatment outcomes at community-based sites with traditional care at a central, specialised hospital. DESIGN: A non-randomised observational prospective cohort study comparing community-based and centralised care. Patients at community-based sites were closer to home and had easier access to care, and home-based care was available from treatment initiation. RESULTS: Four community-based sites treated 736 patients, while 813 were treated at the centralised hospital (total = 1549 patients). Overall, 75% were HIV co-infected (community: 76% vs. hospitalised: 73%, P = 0.45) and 86% received antiretroviral therapy (community: 91% vs. hospitalised: 82%, P = 0.22). On multivariate analysis, MDR-TB patients were more likely to have a successful treatment outcome if they were treated at a community-based site (adjusted OR 1.43, P = 0.01). However, outcomes at the four community-based sites were heterogeneous, with Site 1 demonstrating that home-based care was associated with an increased treatment success of 72% compared with success rates of 52-60% at the other three sites. CONCLUSION: Community-based care for MDR-TB patients was more effective than care in a central, specialised hospital. Home-based care further increased treatment success.

Inflammation and tuberculosis: host-directed therapies.

Tuberculosis (TB) is an airborne infectious disease that kills almost two million individuals every year. Multidrug-resistant (MDR) TB is caused by strains of Mycobacterium tuberculosis (M. tb) resistant to isoniazid and rifampin, the backbone of first-line antitubercular treatment. MDR TB affects an estimated 500,000 new patients annually. Genetic analysis of drug-resistant MDR-TB showed that airborne transmission of undetected and untreated strains played a major role in disease outbreaks. The need for new TB vaccines and faster diagnostics, as well as the development of new drugs, has recently been highlighted. The major problem in terms of current TB research and clinical demands is the increasing number of cases of extensively drug-resistant and 'treatment-refractory' TB. An emerging scenario of adjunct host-directed therapies is intended to target pulmonary TB where inflammatory processes can be deleterious and lead to immune exhaustion. 'Target-organ-saving' strategies may be warranted to prevent damage to infected tissues and achieve focused, clinically relevant and long-lasting anti-M. tb cellular immune responses. Candidates for such interventions may be biological agents or already approved drugs that can be 're-purposed' to interfere with biologically relevant cellular checkpoints. Here, we review current concepts of inflammation in TB disease and discuss candidate pathways for host-directed therapies to achieve better clinical outcomes.

Midtrimester vaginal Mycoplasma genitalium in women with subsequent spontaneous preterm birth.

OBJECTIVE: We sought to determine the midtrimester prevalence of Mycoplasma genitalium in women who had subsequent spontaneous preterm birth. STUDY DESIGN: In a prospective study of lower genital tract infections, we identified 127 women who subsequently had spontaneous preterm birth. Vaginal samples were obtained between 21 and 25 weeks' gestation for pH, for bacterial vaginosis Gram stain, and cultures that yielded Chlamydia trachomatis, Neisseria gonorrhoeae, and Trichomonas vaginalis. M genitalium was identified by using validated polymerase chain reaction (PCR) primers, and the results were compared to pregnancy outcomes. RESULTS: Of 124 women with spontaneous preterm births, only five (3.9%) had PCR assays positive forM genitalium. The mean +/- SD delivery gestational age was similar for women with a positive PCR (34.6 +/- 2.2 weeks) and a negative PCR (34.0 +/- 2.7 weeks) (P =.62). None of the women with positive PCR results tested positive for any other sexually transmitted disease, whereas 36 (30%) women with negative PCR results tested positive. CONCLUSIONS: The occurrence of M genitalium in the vagina at midtrimester is infrequent in women with subsequent spontaneous preterm birth.

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.

A link between chronic asthma and chronic infection.

BACKGROUND: Asthma is a prevalent disease with marked effects on quality of life and economic societal burden. However, the cause of asthma and its pathophysiology are not completely defined. Recently, the possibility that chronic infection may play a role has been suggested. OBJECTIVE: We sought to define the association between Mycoplasma and Chlamydia species and chronic asthma. METHODS: We performed a comparison study of asthmatic patients and normal control subjects. Fifty-five patients with chronic stable asthma were compared with 11 normal control subjects by using PCR, culture, and serology for Mycoplasma species, Chlamydia species, and viruses from the nasopharynx, lung, and blood. Bronchoalveolar lavage cell count and differential, as well as tissue morphometry, were also evaluated. Computer-generated scoring for the degree of chronic sinusitis in asthmatic patients was additionally evaluated. RESULTS: Thirty-one of 55 asthmatic patients had positive PCR results for Mycoplasma (n = 25) or Chlamydia species (n = 6), which were mainly found on lung biopsy specimens or in lavage fluid. Only 1 of 11 normal control subjects had positive PCR results for Mycoplasma species. The distinguishing phenotype between asthmatic patients with positive and negative PCR results was the significantly greater number of tissue mast cells in the group with positive results. CONCLUSION: A significant number of patients with chronic stable asthma demonstrate the presence of Mycoplasma species, Chlamydia species, or both in their airways, with the distinguishing feature of increased mast cell number. These findings need further delineation but may help us to understand the pathophysiology of asthma and new treatment options.

Development of antimicrobial agents in the era of new and reemerging infectious diseases and increasing antibiotic resistance.

During the past 2 decades, new infectious diseases have appeared and old ones previously thought to be controlled have reemerged. New and reemerging infectious agents will continue to pose serious threats well into the 21st century. The prediction that the threat of infectious disease may not diminish is supported by evidence that infectious agents cause many chronic diseases and cancer of previous unknown etiology. Moreover, the utility of existing antimicrobial agents is rapidly eroding, tipping the balance in favor of multidrug-resistant pathogens, and there appear to be few, if any, new classes of drugs currently in clinical development. The need for research directed toward development of new antibiotics has never been greater. Advances in research technologies and microbial genome sequencing in the past decade have led to identification of a large number of new targets. Functional genomics and integrative biology should validate these targets and provide the best opportunity for developing effective new therapies, improved diagnostic techniques, and better tools to understand host-pathogen interactions.

The complete sequence of the mucosal pathogen Ureaplasma urealyticum.

The comparison of the genomes of two very closely related human mucosal pathogens, Mycoplasma genitalium and Mycoplasma pneumoniae, has helped define the essential functions of a self-replicating minimal cell, as well as what constitutes a mycoplasma. Here we report the complete sequence of a more distant phylogenetic relative of those bacteria, Ureaplasma urealyticum (parvum biovar), which is also a mucosal pathogen of humans. It is the third mycoplasma to be sequenced, and has the smallest sequenced prokaryotic genome except for M. genitalium. Although the U. urealyticum genome is similar to the two sequenced mycoplasma genomes, features make this organism unique among mycoplasmas and all bacteria. Almost all ATP synthesis is the result of urea hydrolysis, which generates an energy-producing electrochemical gradient. Some highly conserved eubacterial enzymes appear not to be encoded by U. urealyticum, including the cell-division protein FtsZ, chaperonins GroES and GroEL, and ribonucleoside-diphosphate reductase. U. urealyticum has six closely related iron transporters, which apparently arose through gene duplication, suggesting that it has a kind of respiration system not present in other small genome bacteria The genome is only 25.5% G+C in nucleotide content, and the G+C content of individual genes may predict how essential those genes are to ureaplasma survival.

Dissection of bacteriophage lambda site-specific recombination using synthetic peptide combinatorial libraries.

A wide variety of tools have been used to dissect biochemical pathways, inhibitors being chief among them. Combinatorial approaches have made the search for inhibitors much more efficient. We have applied such an approach to identify hexapeptides which inhibit different steps in a site-specific recombination reaction mediated by the bacteriophage lambda integrase protein. Integrase's mechanism is still incompletely understood, in large part because several pathway intermediates remain hard to isolate. Integrase-catalyzed recombination is very efficient, but if blocked, it is highly reversible to substrates; this combination makes some intermediates exceedingly transient. We have used synthetic peptide combinatorial libraries to screen for hexapeptides that affect the recombination pathway at different stages, and have identified two families of peptides: one probably blocks DNA cleavage, the other may stabilize the Holliday junction intermediates. These peptides do not resemble parts of integrase or any of the other helper functions in the pathway. The deconvolution of hexapeptide libraries based both on inhibition of an enzymatic reaction as well as on accumulation of reaction intermediates is a novel approach to finding useful tools for dissecting a biochemical pathway.

Peptide inhibitors of DNA cleavage by tyrosine recombinases and topoisomerases.

The study of biochemical pathways requires the isolation and characterization of each and every intermediate in the pathway. For the site-specific recombination reactions catalyzed by the bacteriophage lambda tyrosine recombinase integrase (Int), this has been difficult because of the high level of efficiency of the reaction, the highly reversible nature of certain reaction steps, and the lack of requirements for high-energy cofactors or metals. By screening synthetic peptide combinatorial libraries, we have identified two related hexapeptides, KWWCRW and KWWWRW, that block the strand-cleavage activity of Int but not the assembly of higher-order intermediates. Although the peptides bind DNA, their inhibitory activity appears to be more specifically targeted to the Int-substrate complex, insofar as inhibition is resistant to high levels of non-specific competitor DNA and the peptides have higher levels of affinity for the Int-DNA substrate complex than for DNA alone. The peptides inhibit the four pathways of Int-mediated recombination with different potencies, suggesting that the interactions of the Int enzyme with its DNA substrates differs among pathways. The KWWCRW and KWWWRW peptides also inhibit vaccinia virus topoisomerase, a type IB enzyme, which is mechanistically and structurally related to Int. The peptides differentially affect the forward and reverse DNA transesterification steps of the vaccinia topoisomerase. They block formation of the covalent vaccinia topoisomerase-DNA intermediate, but have no apparent effect on DNA religation by preformed covalent complexes. The peptides also inhibit Escherichia coli topoisomerase I, a type IA enzyme. Finally, the peptides inhibit the bacteriophage T4 type II topoisomerase and several restriction enzymes with 2000-fold lower potency than they inhibit integrase in the bent-L pathway.

Antibody responses after Sendai virus infection and their role in upper and lower respiratory tract disease in rats.

BACKGROUND AND PURPOSE: Sendai virus infection in rats is an excellent model for studying development and role of host defenses throughout the respiratory tract after this infection. Therefore, development of serum antibody responses and disease were studied. METHODS: Forty-two anesthetized pathogen-free 3- to 4- week-old LEW/NCr rats were inoculated intranasally with Sendai virus. At postinoculation days 0, 2, 3, 5, 8, 10, and 14, rats were euthanized by administration of a pentobarbital sodium overdose followed by exsanguination. Serum was obtained from all animals, and nasal wash and bronchoalveolar lavage specimens were collected during selected experiments. An ELISPOT assay was used to measure numbers of Sendai virus-specific antibody-forming cells in respiratory tract lymphoid tissue. RESULTS: Recovery from disease and clearance of virus from respiratory tract tissues coincided with development of serum antibody responses. Upper respiratory tract lymph nodes were the initial and major sites of appearance of antibody-forming cells. Immunoglobulin G was the predominant subtype of these cells during recovery from the infection and in rats resistant to infection. Passive transfer of antisera or specific IgG protected the lower but not the upper respiratory tract. CONCLUSIONS: Circulating components of immunity have a major role in resistance and recovery from disease in the lower respiratory tract, whereas local responses are likely involved in protection of the upper respiratory tract. Local lymphoid tissues are the major production sites of IgG, which contributes to resistance to and recovery from respiratory tract diseases.

Mycoplasma penetrans bacteremia and primary antiphospholipid syndrome.

Mycoplasma penetrans, a rare bacterium so far only found in HIV-infected persons, was isolated in the blood and throat of a non-HIV-infected patient with primary antiphospholipid syndrome (whose etiology and pathogenesis are unknown).

The geometry of a synaptic intermediate in a pathway of bacteriophage lambda site-specific recombination.

Bacteriophage lambda uses site-specific recombination to move its DNA into and out of the Escherichia coli genome. The recombination event is mediated by the phage-encoded integrase (Int) at short DNA sequences known as attachment ( att ) sites. Int catalyzes recombination via at least four distinct pathways, distinguishable by their requirements for accessory proteins and by the sequence of their substrates. The simplest recombination reaction catalyzed by Int does not require any accessory proteins and takes place between two attL sites. This reaction proceeds through an intermediate known as the straight-L bimolecular complex (SL-BMC), a stable complex which contains two attL sites synapsed by Int. We have investigated the orientation of the two substrates in the SL-BMC with respect to each other using two independent direct methods, a ligation assay and visualization by atomic force microscopy (AFM). Both show that the two DNA substrates in the complex are arranged in a tetrahedral or nearly square planar alignment skewed towards parallel. The DNA molecules in the complex are bent.

Preventing the misuse of microorganisms: the role of the American Society for Microbiology in protecting against biological weapons.

The American Society for Microbiology's (ASM) involvement with issues surrounding biological weapons began during World War II and continues to the present time. The Public and Scientific Affairs Board (PSAB) of the ASM has played an important role in monitoring and responding to legislative and regulatory issues involving biological weapons. As this review makes apparent, there is no consensus of opinion among scientists on their role in biological defense research, or is it likely that there will ever be complete agreement. There is consensus that steps should be taken to prevent biological warfare and that openness of scientific research and global surveillance of disease outbreaks can significantly increase transparency for detecting development of biological weapons. The ASM recommends increased attention to and efforts directed toward global surveillance of disease outbreaks, not only to aid public health organizations in improving human health, but also to establish baseline data against which unusual disease outbreaks can be assessed. Issues of how best to increase global security and to achieve a scientifically based verification protocol of the Biological Weapons Convention are important and continue to be addressed by the ASM.

Safety and efficacy of azithromycin in the treatment of community-acquired pneumonia in children.

OBJECTIVE: To compare the safety and efficacy of azithromycin with amoxicillin/clavulanate or erythromycin for the treatment of community-acquired pneumonia, including atypical pneumonia caused by Mycoplasma pneumoniae and Chlamydia pneumoniae. METHODS: Multicenter, parallel group, double blind trial in which patients 6 months to 16 years of age with community-acquired pneumonia were randomized 2:1 to receive either azithromycin for 5 days or conventional therapy for 10 days (amoxicillin/clavulanate if < or =5 years of age or erythromycin estolate if >5 years of age). Patients from 23 geographically diverse sites were evaluated for clinical outcomes and/or adverse events at Days 3 to 5, Days 15 to 19 and 4 to 6 weeks posttherapy. Microbiology (culture or polymerase chain reaction) was done at baseline and Days 15 to 19 for bacteria, Chlamydia pneumoniae and Mycoplasma pneumoniae. Serology for C. pneumoniae and M. pneumoniae was done at baseline and 4 to 6 weeks posttherapy. RESULTS: Of 456 patients enrolled during 17 consecutive months, 420 were evaluable. Clinical success at Study Days 15 to 19 was 94.6% in the azithromycin group and 96.2% in the comparative treatment group (P = 0.735) and at 4 to 6 weeks posttherapy 90.6 and 87.1%, respectively (P = 0.330). Evidence of infection was identified in 46% of 420 evaluable patients (1.9% bacteria, 29.5% M. pneumoniae and 15% C. pneumoniae). Microbiologic eradication was 81% for C. pneumoniae and 100% for M. pneumoniae in the azithromycin group vs. 100 and 57%, respectively, in the comparator group. Treatment-related adverse events occurred in 11.3% of the azithromycin group and 31% in the comparator group (P < 0.05). CONCLUSION: Azithromycin used once daily for 5 days produced a satisfactory therapeutic outcome similar to those of amoxicillin/clavulanate or erythromycin given three times a day for 10 days for treatment of community-acquired pneumonia. Azithromycin had significantly fewer side effects than comparator drugs.

Mycoplasma pneumoniae pneumonia in a mouse model.

To investigate the pathogenesis of acute Mycoplasma pneumoniae infection, BALB/c mice were anesthetized with metofane, and M. pneumoniae was introduced intranasally on days 0, 1, and 2. Mice were sacrificed on days 0-15. A histopathologic scoring system defined inflammatory changes in the lungs on a scale of 0-26 (least to most severe). Broth cultures were positive for all nasal passage and bronchoalveolar lavage (BAL) specimens. Histopathologic scores ranged from 0 to 21. The mean log10 (cfu/mL) were 4.1-6.4 on days 1-10 and >/=1.7 on days 13-15 for nasal passage and BAL specimens. Serum polymerase chain reaction was negative. ELISA for serum IgM and immunoblots for M. pneumoniae antibody were positive in 21 (62%) of 34 and 33 (97%) of 34 infected animals, respectively, at days 8-15. ELISA for IgG antibody was negative. This mouse pneumonia model can be used to study the immunologic and therapeutic responses to acute M. pneumoniae infection.

Detection of Mycoplasma pneumoniae in the airways of adults with chronic asthma.

Infection with Mycoplasma pneumoniae has been shown to exacerbate asthma in humans. However, the role of M. pneumoniae in the pathogenesis of chronic asthma has not been defined. Eighteen asthmatics with chronic, stable asthma and 11 nonasthmatic control subjects underwent evaluation of the upper and lower airways and serologic analysis to determine the presence of M. pneumoniae, Chlamydia pneumoniae, and seven respiratory viruses through culture, enzyme-linked immunoassay (EIA) and polymerase chain reaction (PCR). M. pneumoniae was detected by PCR in 10 of 18 asthmatics and one of 11 control subjects (p = 0.02). In nine of the 10 patients, the organism was detected in bronchoalveolar lavage or bronchial biopsies. Seven of 18 asthmatics and one of 11 control subjects were also positive for M. fermentans and M. genitalium by PCR. All patients' cultures, EIAs, and serology were negative for M. pneumoniae. All PCR and cultures were negative for C. pneumoniae, and all EIAs for respiratory viruses were negative in all subjects. Nine asthmatics and one control subject exhibited positive serology for C. pneumoniae (p = 0.05). M. pneumoniae was present in the lower airways of chronic, stable asthmatics with greater frequency than control subjects, and may play a role in the pathogenesis of chronic asthma.

Infectious causes of chronic inflammatory diseases and cancer.

Powerful diagnostic technology, plus the realization that organisms of otherwise unimpressive virulence can produce slowly progressive chronic disease with a wide spectrum of clinical manifestations and disease outcomes, has resulted in the discovery of new infectious agents and new concepts of infectious diseases. The demonstration that final outcome of infection is as much determined by the genetic background of the patient as by the genetic makeup of the infecting agent is indicating that a number of chronic diseases of unknown etiology are caused by one or more infectious agents. One well-known example is the discovery that stomach ulcers are due to Helicobacter pylori. Mycoplasmas may cause chronic lung disease in newborns and chronic asthma in adults, and Chlamydia pneumoniae, a recently identified common cause of acute respiratory infection, has been associated with atherosclerosis. A number of infectious agents that cause or contribute to neoplastic diseases in humans have been documented in the past 6 years. The association and causal role of infectious agents in chronic inflammatory diseases and cancer have major implications for public health, treatment, and prevention.

Roles of innate and adaptive immunity in respiratory mycoplasmosis.

Current evidence suggests that host defense in respiratory mycoplasmosis is dependent on both innate and humoral immunity. To further delineate the roles of innate and adaptive immunity in antimycoplasmal defenses, we intranasally infected C3H/HeSnJ-scid/scid (C3H-SCID), C3H/HeSnJ (C3H), C57BL/6J-scid/scid (C57-SCID), and C57BL/6N (C57BL) mice with Mycoplasma pulmonis and at 14 and 21 days postinfection performed quantitative cultures of lungs and spleens, quantification of lung lesions, and histopathologic assessments of all other major organs. We found that numbers of mycoplasmas in lungs were associated with genetic background (C3H susceptible, C57BL resistant) rather than functional state of adaptive immunity, indicating that innate immunity is the main contributor to antimycoplasmal defense of the lungs. Extrapulmonary dissemination of mycoplasmas with colonization of spleens and histologic lesions in multiple organs was a common occurrence in all mice. The absence of adaptive immune responses in severe combined immunodeficient (SCID) mice resulted in increased mycoplasmal colonization of spleens and lesions in extrapulmonary sites, particularly spleens, hearts, and joints, and also reduced lung lesion severity. The transfer of anti-M. pulmonis serum to infected C3H-SCID mice prevented extrapulmonary infection and disease, while the severity of lung lesions was restored by transfer of naive spleen cells to infected C3H-SCID mice. Collectively, our results strongly support the conclusions that innate immunity provides antimycoplasmal defense of the lungs and humoral immunity has the major role in defense against systemic dissemination of mycoplasmal infection, but cellular immune responses may be important in exacerbation of mycoplasmal lung disease.

Weekly oral azithromycin as prophylaxis for agents causing acute respiratory disease.

Since the 1950s the U.S. military has used intramuscular injections of benzathine penicillin G (BPG) to control outbreaks of respiratory disease. In an effort to find an alternative prophylaxis, a randomized field trial was conducted among 1,016 male U.S. Marine trainee volunteers at high risk for respiratory disease. Participants were evaluated for evidence of acute respiratory infection by serological tests on pretraining and posttraining sera (63 days apart). Oral azithromycin prophylaxis (500 mg/w) outperformed BPG, preventing infection from Streptococcus pyogenes (Efficacy [E] = 84%; 95% confidence interval [CI], 63%-93%), Streptococcus pneumoniae (E = 80%; 95% CI, 50%-92%), Mycoplasma pneumoniae (E = 64%; 95% CI, 25%-83%), and Chlamydia pneumoniae (E = 58%; 95% CI, 15%-79%) in comparison with results in a no-treatment group. Azithromycin group subjects reported few side effects and less respiratory symptoms than the BPG and no-treatment groups. According to serological tests, oral azithromycin is an effective alternative prophylaxis to BPG for military populations.