Impact of mass administration of azithromycin as a preventive treatment on the prevalence and resistance of nasopharyngeal carriage of Staphylococcus aureus

Staphylococcus aureus is a major cause of serious illness and death in children, indicating the need to monitor prevalent strains, particularly in the vulnerable pediatric population. Nasal carriage of S. aureus is important as carriers have an increased risk of serious illness due to systemic invasion by this pathogen and can transmit the infection. Recent studies have demonstrated the effectiveness of azithromycin in reducing the prevalence of nasopharyngeal carrying of pneumococci, which are often implicated in respiratory infections in children. However, very few studies of the impact of azithromycin on staphylococci have been undertaken. During a clinical trial under taken in 2016, nasal swabs were collected from 778 children aged 3 to 59 months including 385 children who were swabbed before administration of azithromycin or placebo and 393 after administration of azithromycin or placebo. Azithromycin was given in a dose of 100 mg for three days, together with the antimalarials sulfadoxine-pyrimethamine and amodiaquine, on four occasions at monthly intervals during the malaria transmission season. These samples were cultured for S. aureus as well as for the pneumococcus. The S. aureus isolates were tested for their susceptibility to azithromycin (15 g), penicillin (10 IU), and cefoxitine (30 g) (Oxoid Ltd). S. aureus was isolated from 13.77% (53/385) swabs before administration of azithromycin and from 20.10% (79/393) six months after administration (PR = 1.46 [1.06; 2.01], p = 0.020). Azithromycin resistance found in isolates of S. aureus did not differ significantly before and after intervention (26.42% [14/53] vs 16.46% [13/79], (PR = 0.62 [0.32; 1.23], p = 0.172). Penicillin resistance was very pronounced, 88.68% and 96.20% in pre-intervention and in post-intervention isolates respectively, but very little Methicillin Resistance (MRSA) was detected (2 cases before and 2 cases after intervention). Monitoring antibiotic resistance in S. aureus and other bacteria is especially important in Burkina Faso due to unregulated consumption of antibiotics putting children and others at risk.

[Vancomycin-based Lowenstein-Jensen selective medium for reducing contamination of mycobacterial cultures by spore-forming bacteria]

INTRODUCTION

despite the development of new methods, culture on solid medium is the gold standard for the diagnosis of tuberculosis. However, this method is associated with increased rates of contamination of cultures by spore-forming bacteria. These bacteria are generally sensitive to vancomycin and to a combinsation of vancomycin, colistin, nystatin, and trimethoprim (VCNT). The purpose of this study was to assess the effectiveness of VCNT-based selective Lowenstein-Jensen (LJ) medium in reducing contamination of cultures by spore-forming bacteria.

METHODS

sputum samples, collected from the 120 TB and non-TB patients included in the study between October 2016 and May 2017, were decontaminated with the modified Petroff method. Decontamination pellets were inoculated onto conventional LJ media and selective VCNT-based LJ medium containing 10µg/ml vancomycin. Fifteen strains of spore-forming bacteria were inoculated onto the same media in order to assess their sensitivity to VCNT.

RESULTS

the contamination of cultures on VCNT-based LJ medium containing 10µg/ml of vancomycin and LJ medium were 11.66% (14/120) and 39.16% (47/120) with p <0.0001, respectively. Sensitivity of spore-forming bacteria to VCNT decreased with the increasing of culture incubation time.

CONCLUSION

VCNT-based selective LJ medium containing 10µg/ml vancomycin led to a significant reduction in the rate of culture contamination. This environment could contribute to improve the quality of mycobacterial cultures and thus bacteriological diagnosis of tuberculosis.

Identification of spore-forming bacteria isolated from contaminated Lowenstein Jensen media and effectiveness of Vancomycin to reduce Mycobacterial culture contamination in Burkina-Faso

The type of commensal microorganisms can influence the efficiency of sputum decontamination for TB diagnosis. A basic characterization of contaminants from LJ contaminated media showed that Gram positive Spore Forming Bacteria (SFB) were the major contaminants. This study aims to identify the species of this contaminants and to evaluate the effectiveness of VCNT at 10 µg of vancomycin to reduce mycobacterial culture contamination mainly linked to SFB. Fifty-three SFB isolated between February 2016 and May 2017 were used. The effectiveness of LJ with VCNT at 10 µg of Vancomycin were evaluated with sputum collected in the same period. SFB had been stored at -20 °C and identified after subculture onto 5% sheep blood Columbia agar and incubated at 37 °C during 24 h. Bacteria cells and isolated colonies were described. API 50CH/B was performed and MALDI-TOF MS was used for external quality control. Thirty- five (66%) isolates representing 4 genera (Bacillus, Paenibacillus, Brevisbacillus and Lysinibacillus) including 10 species were identified. The most important species were Bacillus cereus (30%) and Bacillus licheniformis (21%). Eighteen (34%) isolates were non-reactive Bacillus. The overall contamination rate on LJ with VCNT at 10 µg of vancomycin was statistically lower than which without VCNT (18.7% versus 43.8%) (p = 0.01). The most important SFB identified were B. cereus and B. licheniformis. Almost all identified strains were similar to those currently isolated in fermented traditional food suggesting in part food related contaminants. VCNT containing 10 µg of vancomycin is a good alternative method to reduce mycobacterial culture contamination.

Why oral antiseptic mouth rinsing before sputum collection cannot reduce contamination rate of mycobacterial culture in Burkina-Faso

Background

Tuberculosis (TB) diagnosis by culture in most resource-limited settings is hampered by high contamination rate varying up to 31%. Reduction of oral microorganism loads by mouth rinse with antiseptic before sputum collection showed a reduction of contamination. Moreover, knowing the characteristic of residual contaminant microorganisms would be an asset to understand contamination issues.

Objectives

The aim of this study was to evaluate the effects of mouth rinsing with chlorhexidine on mycobacteria culture contaminations and to characterize morphologically the residual contaminants.

Methods

We consecutively included 158 patients in a TB center. Each of them supplied two sputa: The first before mouth rinse, and the second after 60sec of mouth rinsing with chlorhexidine (0.1%). Petroff method and Lowenstein-Jensen media were used for sputum decontamination and inoculation respectively. The contamination rates were compared, and the type of residual contaminants were characterized and compared.

Results

The contamination rate did not differ before and after the mouth rinse (respectively 58/150 (39 %) vs 61/150 (41 %), p=0.7). The major residual contaminants were Gram positive spore forming bacteria (94%).

Conclusion

Chlorhexidine mouth rinsing before sputum collection did not reduce mycobacterial culture contamination rate. This is probably due to spore forming bacteria, highlighted as major residual contaminants.

Cervicovaginal secretory antibodies to human immunodeficiency virus type 1 (HIV-1) that block viral transcytosis through tight epithelial barriers in highly exposed HIV-1-seronegative African women

Antibodies to human immunodeficiency virus (HIV) of the IgA, IgG, and IgM isotypes and high levels of the HIV suppressive beta-chemokine RANTES (regulated on activation, normally T cell expressed and secreted) were found in the cervicovaginal secretions (CVSs) of 7.5% of 342 multiply and repeatedly exposed African HIV-seronegative female sex workers. The antibodies are part of a local compartmentalized secretory immune response to HIV, since they are present in vaginal fluids that are free of contaminating semen. Cervicovaginal antibodies showed a reproducible pattern of reactivity restricted to gp160 and p24. Locally produced anti-env antibodies exhibit reactivity toward the neutralizing ELDKWA epitope of gp41. Study results show that antibodies purified from CVSs block the transcytosis of cell-associated HIV through a tight epithelial monolayer in vitro. These findings suggest that genital resistance to HIV may involve HIV-specific cervicovaginal antibody responses in a minority of highly exposed HIV-seronegative women in association with other protecting factors, such as local production of HIV-suppressive chemokines.

Detection of Y chromosome DNA as evidence of semen in cervicovaginal secretions of sexually active women

The detection of traces of semen in cervicovaginal secretions (CVS) from sexually active women practicing unprotected sex is a prerequisite for the accurate study of cervicovaginal immunity. Two semen markers, the prostatic-specific antigen (PSA) and the Y chromosome, were detected in parallel in CVS obtained by a standardized vaginal washing of consecutive women attending the principal medical center for sexually transmitted diseases of Bangui, Central African Republic. PSA was detected by immunoenzymatic capture assay in the cell-free fraction of CVS, and the Y chromosome was detected by a single PCR assay of DNA extracted by silica from the cell fraction (Y PCR). Fifty (19%) cell-free fractions of the 264 beta-globin-positive CVS samples were positive for PSA, and 100 (38%) cell fractions of the CVS samples were positive for the Y chromosome. All the 50 (19%) PSA-containing CVS samples were also positive for the Y chromosome. Fifty (19%) CVS samples were positive only for the Y chromosome, with no detectable PSA. The remaining 164 (62%) CVS samples were both PSA and Y chromosome negative. These findings demonstrate that CVS from sexually active women may contain cell-associated semen residues unrecognized by conventional immunoenzymatic assays used to detect semen components. The detection of cell-associated male DNA with a highly sensitive and specific procedure such as Y PCR constitutes a method of choice to detect semen traces in female genital secretions.

Neutralizing antibodies and complement-mediated, antibody-dependent enhancement (C'-ADE) of human immunodeficiency virus infection in its vertical transmission

PROBLEM

Mother-to-child transmission is a major route for the spread of human immunodeficiency virus (HIV) worldwide. Our understanding of its mechanisms and parameters is still limited. Among the factors possibly involved in virus passage determination are the level and quality of antiviral humoral response.

METHOD OF STUDY

Anti-HIV-1/Lai neutralizing activity in sera from 35 mother-infant pairs (in which 13 transmission cases occurred) was investigated, as was the complement-mediated antibody-dependent enhancement capacity of the same sera.

RESULTS

Neutralization titers of 640 or more were found only in four mothers of uninfected children, but this result was not significant. No significant link was obtained with the occurrence of complement-mediated, antibody-dependent enhancement.

CONCLUSIONS

As suggested by a synthesis of the literature, vertical transmission of HIV is probably the result of multiple active and/or stochastic parameters in the mother, the fetal structures, and the viral population. The precise definition of cellular mechanisms involved in in utero infection would help to better define which immune activity in the mother should be more carefully considered.

Modulations of cytokine expression in pregnant women

PROBLEM

Although the overall anti-infectious and anti-parasitic immunity of parous women appears normal, several aspects of maternal cell-mediated and humoral immunity are altered during pregnancy. This has been suggested to occur via preferential local and systemic secretion of Th-2 type cytokines, which down-regulate or prevent secretion/action of Th-1 type cytokines, in animals as well as in humans.

METHOD

To evaluate the influence of gestation on the maternal immune system, we have measured, in pregnant women, the mRNAs coding for several cytokines (TNF alpha, IFN gamma, GM-CSF, IL-1 beta, IL-2, IL-4, IL-6, and IL-10) in peripheral blood mononuclear cells, by use of semi-quantitative RT-PCR.

RESULTS

Our results show significant modulations of IFN gamma, IL-1 beta, IL-4, and IL-6 genes expression especially during the third trimester and near parturition.

CONCLUSION

Cytokine expression is thus finely tuned in peripheral blood during pregnancy, in a previously unexpected complex pattern, related to gestational stage.

Clearance of HIV infection in 12 perinatally infected children: clinical, virological and immunological data

OBJECTIVE

A case of HIV infection clearance in a perinatally infected infant has been recently reported. We report here on the molecular, biological and clinical features of such virus clearance in 12 children.

DESIGN AND METHODS

We performed a retrospective analysis of the diagnosis in our 6-year cohort of 188 children born to HIV-seropositive mothers. HIV-1 was detected by coculture of infant peripheral blood mononuclear cells (PBMC) with cord blood cells, direct culture of infant cells, and DNA polymerase chain reaction (PCR). The children were diagnosed three times during the first 3 months of life and then followed up over a postnatal period of 18-36 months.

RESULTS

The 12 reverted children had at least two positive PCR in at least two amplified regions. Among them, six were tested positive in culture/coculture assay, and five were treated long-term with zidovudine. Thus, seven out of 12 reversions cannot be attributed to antiretroviral therapy. All the virological results became negative during the first year of life, and serology lowered to negative values between 9 and 23 months. We could not find any correlation between either neutralizing or antibody-dependent cellular cytotoxicity-mediating antibodies and HIV clearance.

CONCLUSION

In our cohort, we showed that an unexpected number of children born to HIV-seropositive mothers (6.7%) cleared HIV infection during the first year of life, and subsequently became seronegative. Interestingly, most of these children exhibited unspecified clinical signs during the first months of life. Five of these children were tested positive only by PCR, which suggests a low virus load and could, at least partly, explain spontaneous clearance. However, 4 years later, among the seven remaining infants, two seronegative children presented recurrent hepatosplenomegaly, which may indicate the presence of hidden virus not detectable by peripheral blood testing.