Impact of Intrapartum Oral Azithromycin on <i>Staphylococcus aureus</i> Colonisation and Staphylococcal Antibiotic Resistance Among Women and Their Babies in The Gambia

Maternal and neonatal infections are a major public health problem leading to high morbidity and mortality in middle and low-income countries. There is a need for effective interventions suitable for these countries to reduce the high burden of disease. Intrapartum azithromycin is a potential intervention to reduce maternal and neonatal infections and their associated deaths. PregnAnZI-1, the first intrapartum oral azithromycin trial was a Phase III, double-blind, placebo controlled randomized clinical trial in which 829 women in labour were randomized to receive either a single dose of 2g of oral azithromycin or placebo (ratio 1:1). The trial was conceived as a pilot study to determine the impact of the intervention on maternal and neonatal bacterial colonization, as a necessary step towards sepsis. Nasopharyngeal swabs (NPS), breast milk (BM) and vaginal swabs (VS) were collected from study women and /or their babies during the first 4 weeks of follow-up (day 0, day 3, day 6, day 8, day 14 and day 28). Additionally, NPS were also collected from study children in a survey conducted 12 months following the trial. During the trial follow up period (birth to day 28), prevalence of carriage of S. aureus, S. pneumoniae and group B Streptococci decreased significantly in the intervention arm, whilst prevalence of azithromycin resistant S. aureus increased among mothers or their babies exposed to azithromycin compared to the placebo group. The aims of my PhD investigations are to determine the long-term impact of such intervention on S. aureus colonisation and antimicrobial resistance; molecular epidemiology of azithromycin resistant S. aureus and the prevalence of nasopharyngeal macrolide resistance genes following intrapartum oral azithromycin intervention. In the survey conducted 12 months following the main trial, a total of 461 NPS were screened for prevalence of carriage and azithromycin resistance for S. aureus and S. pneumoniae. As expected there was no difference in the prevalence of nasopharyngeal carriage of S. pneumoniae or S. aureus between children whose mothers had been exposed to azithromycin during labour and those whose mothers had not (85.0% vs 82.1%; odds ratio [OR], 1.23 [95% confidence interval, .73-2.08] for S. pneumoniae and 21.7% vs 21.3%; OR, 1.02 [95% CI, .64-1.64] for S. aureus). Also, prevalence of azithromycin-resistant S. pneumoniae (1.8% vs 0.9% p= 0.384) and S. aureus (3.1% vs 2.6% p= 0.724) were not different between children from the azithromycin and placebo arms, respectively. The intervention did not induce antibiotic resistance to other antibiotics commonly used in Africa for these two bacteria. A random selection of 7 mothers and 10 babies from both arms of the trial, who carried S. aureus resistant to azithromycin in the nasopharynx at day 3 and day 28 post-intervention were included in the second investigation undertaken as part of this PhD. A total of 66 S. aureus isolates underwent genomic investigation. Seven S. aureus sequence types (STs) were identified. ST5 predominated in the placebo arm (73.0% versus 49.0%, p = 0.039) and ST15 in the azithromycin arm (27.0% versus 6.0%, p = 0.022). Among azithromycin-resistant isolates, msr(A) gene was the main macrolide resistance gene (n = 36, 80%) and was found to be located on a multidrug resistant (MDR) plasmid. The intervention appeared to select for the ermC gene as 36% of resistant S. aureus isolates from mothers and babies exposed to antibiotic carried the gene as oppose to 0% in the placebo arm (p< 0.001). Having established that the genetic determinants for S. aureus macrolide resistance were predominantly msr(A) and 7ermC, I assessed the effect of intrapartum oral azithromycin on these genes in my final PhD investigation as they were found to be located on mobile genetic elements that can transfer horizontally between bacteria. PCRs were performed on 936 NPS from 312 children at three different time points (birth, day 28 and 12 months). At birth, prevalence of msr(A) gene was similar in both arms, higher in the azithromycin arm by day 28 (60.7% vs. 29.9% in the azithromycin and placebo arms, respectively; OR, 3.61 [95% CI, 2.20-5.93]) and again similar between arms at 12 months. Prevalence of ermC followed a similar pattern, with differences between arms only apparent at day 28 (63.9% vs. 45.9% in the azithromycin and placebo arms, respectively; OR, 2.09 [95% CI, 1.29-3.37]). In conclusion, the effectiveness of intrapartum oral azithromycin prophylaxis in decreasing carriage of bacteria associated with both maternal and neonatal infections had been established. Emergence of azithromycin resistant S. aureus shortly (28 days) following oral azithromycin exposure was of concern. However, in the long term (12 months), neither the increased azithromycin resistant S. aureus nor the increased nasopharyngeal macrolide resistance genes observed shortly following the intervention persisted among mothers or their new-borns. Hence, supporting the use of intrapartum oral azithromycin prophylaxis as a means to reduce maternal and neonatal infections in The Gambia and potentially other developing countries worldwide

Comparative and stability study of glucose concentrations measured in both sodium fluoride and serum separator tubes.

INTRODUCTION: Sodium fluoride/potassium oxalate (NaF/KOx) tubes has been regarded as the gold-standard tubes for glucose analysis. Even though their ineffectiveness in immediately inhibiting glycolysis has been reported in several studies especially in the first 1-4h, they are still used in our clinical biochemistry laboratory for glucose measurement. However, in its absence, only serum separator tubes are employed for glucose measurement. We aim to determine whether serum separator tubes (SSTs) can replace NaF/KOx tubes for laboratory measurement of blood glucose and to assess the stability of glucose concentrations for 3 days period. METHODS AND FINDINGS: NaF/KOx tube type was the reference method while SSTs type was the candidate method for glucose measurement. A total of 50 paired samples collected separately in NaF/KOx tubes and SSTs from healthy adult participants in the Gambia Adults Reference Intervals Study (GARIS) project were used as the project sample size. Following blood collection and separation, the glucose concentration was measured within 2 h, and at 24h, 42h and 72h time-points. Our data analysis showed no significant difference in the mean glucose concentrations between the reference tube and candidate tube types (Mean difference = 0.06 mmol/L; P = 0.38) recorded in the different timepoints. Using growth trajectory and mixed effects model, the study data further showed no significant change in the glucose concentrations (p = 0.25) for three days period. CONCLUSIONS: The study confirms that SSTs can produce similar glucose results when employed in the absence of NaF/KOx tubes. Besides, the glucose concentrations were stable in both tubes for three days when the samples were separated within 2 h and refrigerated in 2-8°C

Persistence of Nasopharyngeal Pneumococcal Vaccine Serotypes and Increase of Nonvaccine Serotypes Among Vaccinated Infants and Their Mothers 5 Years After Introduction of Pneumococcal Conjugate Vaccine 13 in The Gambia.

BACKGROUND: The widespread use of pneumococcal conjugate vaccine (PCV) has brought about a dramatic decrease in pneumococci of vaccine serotypes (VTs) but nonvaccine serotypes (NVTs) have emerged. METHODS: We conducted a cross-sectional survey (CSS) among infants who received 3 doses of 13-valent PCV (PCV13) and their mothers 5 years (CSS3) after PCV13 introduction. Nasopharyngeal swab samples were collected and cultured for isolation of Streptococcus pneumoniae. Whole-genome sequencing of the nontypeable strains was performed. Data were compared with those from 2 previous surveys conducted before PCV13 introduction (CSS1) and 1 year later (CSS2). RESULTS: Among infants, VT carriage decreased from 33.3% (113/339) in CSS1 to 11.4% (40/351) in CSS3 (P = .001) while NVTs increased from 53.1% (180/339) in CSS1 to 74.4% (261/351) in CSS3 (P < .001). Among mothers, there was a significant decrease in VTs between CSS2 8.4% (29/347) and CSS3 5.6% (19/342) (P = .006). NVTs increased from 16.6% (55/331) in CSS1 to 32.2% (110/342) in CSS3 (P < .001). In CSS3, the most prevalent VTs were 7F in infants and 3 in mothers, and the most prevalent NVTs were serogroup 16 and nontypeables, respectively. Genomic analysis showed that VTs were more likely than NVTs to lose their ability to express the capsule. CONCLUSIONS: Five years after PCV13 introduction, we show both direct (infants) and indirect effects (mothers) of the vaccine, while NVT replacement has occurred in both groups. Ongoing circulation of VTs warrants further study of their relevance in any consideration of a reduced dose schedule

Prevalence and risk factors for Staphylococcus aureus nasopharyngeal carriage during a PCV trial.

BACKGROUND: We conducted an ancillary study among individuals who had participated in a cluster-randomized PCV-7 trial in rural Gambia (some clusters were wholly-vaccinated while in others only young children had been vaccinated), to determine the prevalence and risk factors for Staphylococcus aureus nasopharyngeal carriage. METHODS: Two hundred thirty-two children aged 5-10 years were recruited and followed from 4 to 20 months after vaccination started. We collected 1264 nasopharyngeal swabs (NPS). S. aureus was isolated following conventional microbiological methods. Risk factors for carriage were assessed by logistic regression. RESULTS: Prevalence of S. aureus carriage was 25.9%. In the univariable analysis, prevalence of S. aureus carriage was higher among children living in villages wholly-vaccinated with PCV-7 [OR = 1.57 95%CI (1.14 to 2.15)] and children with least 1 year of education [OR = 1.44 95%CI (1.07 to 1.92)]. S. aureus carriage was also higher during the rainy season [OR = 1.59 95%CI (1.20 to 2.11)]. Carriage of S. pneumoniae did not have any effect on S. aureus carriage for any pneumococcal, vaccine-type (VT) or non-vaccine-type (NVT) carriage. Multivariate analysis showed that the higher prevalence of S. aureus observed among children living in villages wholly-vaccinated with PCV-7 occurred only during the rainy season OR 2.72 95%CI (1.61-4.60) and not in the dry season OR 1.28 95%CI (0.78-2.09). CONCLUSIONS: Prevalence of nasopharyngeal carriage of S. aureus among Gambian children increased during the rainy season among those children living in PCV-7 wholly vaccinated communities. However, carriage of S. aureus is not associated with carriage of S. pneumoniae. TRIAL REGISTRATION: ISRCTN51695599 . Registered August 04th 2006

Seasonality of Pneumococcal Nasopharyngeal Carriage in Rural Gambia Determined within the Context of a Cluster Randomized Pneumococcal Vaccine Trial.

BACKGROUND: We conducted an ancillary study among individuals who had participated in a PCV-7 trial in rural Gambia, to determine the influence of season on the prevalence of pneumococcal carriage. METHODS: 636 individuals above 30 months of age were followed from 4 to 20 months after vaccination with PCV-7 or meningococcal-conjugate-vaccine. Nasopharyngeal swabs were collected periodically between November 2006 and June 2008. Overall, 4,495 NPS were collected. RESULTS: Prevalence of pneumococcal nasopharyngeal carriage in the study subjects (median age 11 years) was 55.0%; this prevalence decreased linearly with increasing age (p = 0.001). Prevalence of carriage was significantly higher during the dry than the rainy season for any pneumococcal carriage [57.6% versus 47.8% (p<0.001)], pneumococcal vaccine serotype carriage [10.3% versus 6.5% (p< 0.001)] and non-vaccine serotype carriage [49.7% versus 42.7% (p<0.001)]. Differences remained significant in the adjusted analysis. CONCLUSIONS: In areas of Africa with marked variation in rainfall, seasonality of pneumococcal carriage needs to be considered when interpreting carriage data

Pre-Vaccination Nasopharyngeal Pneumococcal Carriage in a Nigerian Population: Epidemiology and Population Biology

Initiative (AVI) of the Global Alliance for Vaccines and Immunisation (GAVI). However, country data on the burden of pneumococcal disease (IPD) is limited and coverage by available conjugate vaccines is unknown. This study was carried out to describe the pre vaccination epidemiology and population biology of pneumococcal carriage in Nigeria. Methods: This was a cross sectional survey. Nasopharyngeal swabs (NPS) were obtained from a population sample in 1

Prevention of bacterial infections in the newborn by pre-delivery administration of azithromycin: Study protocol of a randomized efficacy trial.

BACKGROUND: Neonatal deaths, estimated at approximately 4 million annually, now account for almost 40% of global mortality in children aged under-five. Bacterial sepsis is a leading cause of neonatal mortality. Assuming the mother is the main source for bacterial transmission to newborns, the primary objective of the trial is to determine the impact of one oral dose of azithromycin, given to women in labour, on the newborn's bacterial carriage in the nasopharynx. Secondary objectives include the impact of the intervention on bacterial colonization in the baby and the mother during the first month of life. METHODS/DESIGN: This is a Phase III, double -blind, placebo controlled randomized clinical trial in which 830 women in labour were randomized to either a single dose of 2 g oral azithromycin or placebo (ratio 1:1). The trial included pregnant women in labour aged 18 to 45 years attending study health centres in the Western Gambia. A post-natal check of the mother and baby was conducted at the health centre by study clinicians before discharge and 8-10 days after delivery. Home follow up visits were conducted daily during the first week and then weekly until week 8 after delivery. Vaginal swabs and breast milk samples were collected from the mothers, and the pathogens Streptococcus pneumoniae, Group B Streptococcus (GBS) and Staphylococcus aureus were isolated from the study samples. For bacterial isolates, susceptibility pattern to azithromycin was determined using disk diffusion and E-test. Eye swabs were collected from newborns with eye discharge during the follow up period, and Chlamydial infection was assessed using molecular methods. DISCUSSION: This is a proof-of-concept study to assess the impact of antibiotic preventive treatment of women during labour on bacterial infections in the newborn. If the trial confirms this hypothesis, the next step will be to assess the impact of this intervention on neonatal sepsis. The proposed intervention should be easily implementable in developing countries. TRIAL REGISTRATION: ClinicalTrials.gov Identifier--NCT01800942--First received: February 26, 2013

Comparison of the prevalence of common bacterial pathogens in the oropharynx and nasopharynx of gambian infants.

BACKGROUND: CRM- based pneumococcal conjugate vaccines generally have little impact on the overall prevalence of pneumococcal carriage because of serotype replacement. In contrast, protein vaccines could substantially reduce the overall prevalence of pneumococcal carriage with potential microbiological and clinical consequences. Therefore, trials of pneumococcal protein vaccines need to evaluate their impact on carriage of other potentially pathogenic bacteria in addition to the pneumococcus. METHODS: As a prelude to a trial of an investigational pneumococcal vaccine containing pneumococcal polysaccharide conjugates and pneumococcal proteins, the prevalence of carriage of Streptococcus pneumoniae, Haemophilus influenzae, Moraxella species and Staphylococcus aureus in the nasopharynx of 1030 Gambian infants (median age 35 weeks) was determined. An oropharyngeal swab was obtained at the same time from the first 371 infants enrolled. Standard microbiological techniques were used to evaluate the bacterial flora of the pharynx and to compare that found in the oropharynx and in the nasopharynx. RESULTS: The overall pneumococcal carriage rate was high. Isolation rates of S. pneumoniae and Moraxella species were significantly higher using nasopharyngeal rather than oropharyngeal swabs (76.1% [95% CI 73.4%,78.7%] vs. 21.3% [95% CI 17.2%,25.8%] and 48.9% [95% CI 45.8%, 52.0%] vs. 20.5% % [95% CI 16.5%,25.0%] respectively). In contrast, S. aureus and H. influenzae were isolated more frequently from oropharyngeal than from nasopharyngeal swabs (65.0% [95% CI 59.9%, 69.8%] vs. 33.6% [95% CI 30.7%, 36.5%] and 31.8% [95% CI 16.5%, 25.0%] vs. 22.4% [95% CI 19.9%, 25.1%] respectively). No group A β haemolytic streptococci were isolated. CONCLUSION: Collection of an oropharyngeal swab in addition to a nasopharyngeal swab will provide little additional information on the impact of a novel pneumococcal vaccine on pneumococcal carriage but it might provide additional, valuable information on the impact of the vaccine on the overall microbiota of the pharynx

Effect of intra-partum azithromycin on the development of the infant nasopharyngeal microbiota: A post hoc analysis of a double-blind randomized trial.

BACKGROUND: Sepsis is a leading cause of neonatal death. Intrapartum azithromycin reduces neonatal nasopharyngeal carriage of potentially pathogenic bacteria, a prerequisite for sepsis. Early antibiotic exposure has been associated with microbiota perturbations with varying effects. This study aims to understand the effect of intrapartum azithromycin intervention on the developing nasopharyngeal microbiota of the child. METHODS: Using 16S rRNA gene sequencing, we analysed the microbiota of 343 nasopharyngeal samples collected from birth to 12 months from 109 healthy infants selected from a double-blind randomized placebo-controlled clinical trial conducted in the Gambia (PregnAnZI-1). In the trial, 829 women were given 2g oral azithromycin or placebo (1:1) during labour with the objective of reducing bacterial carriage in mother and child during the neonatal period. The post-hoc analysis presented here assessed the effect of the intervention on the child nasopharyngeal microbiota development. FINDINGS: 55 children were from mothers given azithromycin and 54 from mothers given placebo. Comparing arms, we found an increase in alpha-diversity at day-6 (p = 0·018), and a significant effect on overall microbiota composition at days 6 and 28 (R2 = 4.4%, q = 0·007 and R2 = 2.3%, q = 0·018 respectively). At genus level, we found lower representation of Staphylococcus at day-6 (q = 0·0303) and higher representation of Moraxella at 12 months (q = 0·0443). Unsupervised clustering of samples by microbial community similarity showed different community dynamics between the intervention and placebo arms during the neonatal period. INTERPRETATION: These results indicate that intrapartum azithromycin caused short-term alterations in the nasopharyngeal microbiota with modest overall effect at 12 months of age. Further exploration of the effects of these variations on microbiome function will give more insight on the potential risks and benefits, for the child, associated with this intervention. FUNDING: This work was jointly funded by the Medical Research Council (UK) (MC_EX_MR/J010391/1/MRC), Bill & Melinda Gates Foundation (OPP1196513), and MRCG@LSHTM Doctoral Training Program

Effect on nasopharyngeal pneumococcal carriage of replacing PCV7 with PCV13 in the Expanded Programme of Immunization in The Gambia.

INTRODUCTION: In 2011, two years after the introduction of 7-valent Pneumococcal conjugate vaccine (PCV7), the Gambian immunization programme replaced PVC7 with PCV13 (13-valent). Our objective was to assess the additional impact of PCV13 on prevalence of pneumococcal nasopharyngeal carriage. METHODS: We recruited healthy Gambian infants who had received three PCV doses. Nasopharyngeal swabs were collected from infants and their mothers during two cross-sectional surveys (CSS) conducted in infants vaccinated with PCV7 (CSS1) and vaccinated with PCV13 (CSS2). Pneumococci were isolated and serotyped following standardized methods. Whole genome sequencing was performed on non-typable pneumococcus isolated in CSS1 and CSS2. RESULTS: 339 and 350 infants and their mothers were recruited in CSS1 and CSS2, respectively. Overall prevalence of pneumococcal carriage was 85.4% in infants. Among infants, prevalence of vaccine type (VT) carriage was lower in CSS2 [9.4% versus 4.9% (p=0.025) for PCV7-VT; 33.3% versus 18.3% (p<0.001) for PCV13-VT and 23.9% versus 13.7% (p=0.001) for the 6 additional serotypes included in PCV13]. At CSS2, there was a decrease of serotypes 6A (from 15.3% to 5.7%, p<0.001) and 19F (from 5.6% to 1.7%, p=0.007), and an increase of non-typable pneumococci (0.3-6.0%, p<0.001), most of which (82.4%) were from typable serotype backgrounds that had lost the ability to express a capsule. Prevalence of overall and VT carriage in mothers was similar in CSS1 and CSS2. CONCLUSIONS: Replacing PCV7 for PCV13 rapidly decreased prevalence of VT carriage among vaccinated Gambian infants. An indirect effect in mothers was not observed yet. Vaccine-driven selection pressure may have been responsible for the increase of non-typable isolates