The impact of private use of PCV7 in 2009 and 2010 on serotypes and antimicrobial resistance of Streptococcus pneumoniae carried by young children in Portugal: Comparison with data obtained since 1996 generating a 15-year study prior to PCV13 introduction

In Portugal, the 7-valent pneumococcal conjugate vaccine (PCV7) was not introduced in the national immunization plan but was commercially available between 2001 and 2010. We studied serotype distribution and antibiotic susceptibility of Streptococcus pneumoniae carried by children in 2009 and 2010. Vaccination with PCV7 was extracted from children's immunization bulletins and information on recent antimicrobial consumption was obtained through a questionnaire. For comparison, we included data from previous studies conducted since 1996: 1996-1999, 2001-2003, 2006-2007. Pneumococci were isolated from nasopharyngeal samples of 1092 children up to six years old attending day-care in an urban area. Among these, 76% (819/1070) were vaccinated and 62% (677/1092) carried pneumococci. In 2009-2010, serotype replacement was extensive. Carriage of PCV7 serotypes was 4.9% and 5.8%, in 2009 and 2010, respectively, with the majority being of serotype 19F (carried by 4.3% and 4.6% of all participants, respectively). Colonization by serotype 19F was associated with vaccine status (7.7% (19/248) of non-vaccinees vs. 3.5% (29/818) of PCV7-vaccinees, p=0.010). Carriage of serotype 19A was high in 2009 and 2010 (8.6% of all participants) consistent with values already observed in 2007; carriage of serotype 6A was <1% (10/1092), indicating a major decline after 2007 (5.8% or 31/538, p<0.001). Non-vaccine serotypes increased and serotype 6C became the most frequently carried serotype in 2010 (11.2% (54/481)). High-level resistance to penicillin (MIC ≥2mg/L) showed a decreasing trend (p<0.001), whereas resistance to both penicillin and erythromycin increased (p<0.001) and was detected in 15-20% of all isolates in 2009-2010, most of which were non-vaccine serotypes. Antimicrobial use decreased over time (p<0.001). In conclusion, widespread private use of PCV7 has impacted on colonization leading to near elimination of all PCV7 serotypes except for serotype 19F. Antimicrobial consumption declined but it may be too soon to observe generalized changes in antimicrobial resistance rates.

Carriage of beta-lactamase-producing Enterobacteriaceae among nursing home residents in north Lebanon

BACKGROUND

Multidrug-resistant (MDR) Enterobacteriaceae can cause severe infections with high morbidity, mortality, and health care costs. Individuals can be fecal carriers of these resistant organisms. Data on the extent of MDR Enterobacteriaceae fecal carriage in the community setting in Lebanon are very scarce. The aim of this study was to investigate the fecal carriage of MDR Enterobacteriaceae among the elderly residents of two nursing homes located in north Lebanon.

METHODS

Over a period of 4 months, five fecal swab samples were collected from each of 68 elderly persons at regular intervals of 3-4 weeks. Fecal swabs were subcultured on selective media for the screening of resistant organisms. The phenotypic detection of extended-spectrum beta-lactamase (ESBL), AmpC, metallo-beta-lactamase (MBL), and Klebsiella pneumoniae carbapenemase (KPC) production was performed using the beta-lactamase inhibitors ethylenediaminetetraacetic acid, phenylboronic acid, and cloxacillin. A temocillin disk was used for OXA-48. Multiplex PCRs were used for the genotypic detection of ESBL and carbapenemase genes, and sequencing was performed to identify CTX-M-15. The medical records of each subject were reviewed on a regular basis in order to assess the risk factors associated with MDR Enterobacteriaceae fecal carriage.

RESULTS

Over the study period, 76.5% of the recruited elderly persons were at least one-time carriers. A total of 178 isolates were obtained. Phenotypic testing revealed that 91.5% of them were ESBL producers, 4% were AmpC producers, 2.8% were co-producers of ESBL and AmpC, and 1.7% were co-producers of OXA-48 and ESBL. Recent antibiotic intake was found to be the only independent risk factor associated with the fecal carriage of MDR Enterobacteriaceae.

CONCLUSIONS

The high prevalence of MDR Enterobacteriaceae detected in this study and the emergence of carbapenem resistance is alarming. Efficient infection control measures and antibiotic stewardship programs are urgently needed in these settings in order to limit the spread of resistant strains.

Nasopharyngeal carriage of Streptococcus pneumoniae in adults infected with human immunodeficiency virus in Jakarta, Indonesia

This study investigated the distribution of serotype and antimicrobial susceptibility of Streptococcus pneumoniae carried by adults infected with human immunodeficiency virus (HIV) in Jakarta, Indonesia. Specimens of nasopharyngeal swab were collected from 200 HIV infected adults aged 21 to 63 years. Identification of S. pneumoniae was done by optochin susceptibility test and PCR for the presence of psaA and lytA genes. Serotyping was performed with sequential multiplex PCR and antibiotic susceptibility with the disk diffusion method. S. pneumoniae strains were carried by 10% adults with serotype 6A/B 20% was common serotype among cultured strains in 20 adults. Most of isolates were susceptible to chloramphenicol (80%) followed by clindamycin (75%), erythromycin (75%), penicillin (55%), and tetracycline (50%). This study found resistance to sulphamethoxazole/trimethoprim was most common with only 15% of strains being susceptible. High non-susceptibility to sulphamethoxazole/trimethoprim was observed in S. pneumoniae strains carried by HIV infected adults in Jakarta, Indonesia.

Detection of seasonal asymptomatic dermatophytes in Van cats

The Van cat is a domestic landrace found in the Van province of eastern Turkey. In this study, we aimed to determine the seasonal carriage of dermatophytes in Van cats without clinical lesions. A total of 264 hair specimens were collected from clinically healthy cats in and around the Van Province. Of these samples, 30.3% were obtained in spring, 30.6% in summer, 16.6% in autumn, and 22.3% in winter; 45.1% of samples were from male cats and the rest from female ones. Of the studied cats, 118 were younger than 1 year, 78 were 1-3 years old, and 68 were older than 3 years. The specimens were subjected to direct microscopic examination with 15% potassium hydroxide and cultured on Sabouraud dextrose agar and dermatophyte test medium supplemented with cycloheximide and chloramphenicol. Dermatophyte identification was carried out based on macroscopic and microscopic colony morphology, urease activities, in vitro hair perforation test, growth at 37°C, and pigmentation on corn meal agar. Dermatophytes were isolated from 19 (7.1%) of the 264 specimens examined. The most frequently isolated fungi were Trichophyton terrestre (4.1%), followed by Microsporum gypseum (1.1%), M. nanum (1.1%), and T. mentagrophytes (0.7%), and these fungi may represent a health risk for humans in contact with clinically healthy Van cats. M. canis was not isolated from any of the specimens. Our results show no significant (p>0.05) association between carriage of dermatophytes and the gender of cats. The carriage rate of dermatophytes was high in spring and winter, and the only possible risk factor for infection was age of the animal.

The turnover of strains in intermittent and persistent nasal carriers of Staphylococcus aureus

OBJECTIVES

We aimed to examine the dynamics of Staphylococcus aureus nasal carriage in healthy adults.

METHOD

Selected S. aureus strains isolated from weekly nasal swabs obtained from 122 healthy young adults over a 13 week period were spa typed.

RESULTS

The median duration of intermittent carriage was 4 weeks (IQR 2-6) and the median interval between episodes of carriage of different spa types was 3.5 weeks (IQR 2.25-4). 6/19 (32%) Persistent carriers were colonised with more than one spa type during the study, and in two persistent carriers a brief period of mixed colonisation with two spa types was observed. Even when the carriage strain changed, it was very rare for persistent carriers to have a period during which they were culture-negative (only 6/188 (3%) swabs submitted by persistent carriers failed to culture S. aureus).

CONCLUSIONS

Our results imply that at least every eight weeks a healthy young adult is exposed to S. aureus sufficient to cause a new episode of carriage among intermittent carriers. Persistent carriers are almost always colonised with S. aureus and over the course of a year there will be at least one replacement of the dominant strain.

Nasopharyngeal colonization of Gambian infants by Staphylococcus aureus and Streptococcus pneumoniae before the introduction of pneumococcal conjugate vaccines

Staphylococcus aureus and Streptococcus pneumoniae commonly colonize the upper respiratory tract and can cause invasive disease. Several studies suggest an inverse relationship between these two bacteria in the nasopharynx. This association is of particular concern as the introduction of pneumococcal conjugate vaccines (PCVs) that affect pneumococcal nasopharyngeal carriage become widespread. A cohort of children in rural Gambia were recruited at birth and followed for 1 year, before the introduction of PCV into the routine immunization program. Nasopharyngeal swabs were taken immediately after birth, every 2 weeks for the first 6 months and then every other month. The presence of S. aureus and S. pneumoniae was determined using conventional microbiologic methods. Prevalence of S. aureus carriage was 71.6% at birth, decreasing with age to reach a plateau at approximately 20% between 10 to 20 weeks of age. Carriage with any S. pneumoniae increased during the first 10 weeks of life to peak at approximately 90%, mostly of PCV13 serotypes. Although in the crude analysis S. aureus carriage was inversely associated with carriage of any S. pneumoniae and PCV13 serotypes, after adjusting by age and season, there was a positive association with any carriage (odds ratio 1.32; 95% confidence interval 1.07-1.64; p 0.009) and no association with carriage of PCV13 serotypes (odds ratio 0.99; 95% confidence interval 0.70-1.41; p 0.973). Among Gambian infants, S. aureus and S. pneumoniae are not inversely associated in nasopharyngeal carriage after adjustment for age. Further carriage studies following the introduction of PCV are needed to better understand the relationship between the two bacteria.

Serum antibody response to Moraxella catarrhalis proteins OMP CD, OppA, Msp22, Hag, and PilA2 after nasopharyngeal colonization and acute otitis media in children

BACKGROUND

There is no licensed vaccine for Moraxella catarrhalis (Mcat), which is a prominent bacterium causing acute otitis media (AOM) in children and lower respiratory tract infections in adults. Nasopharyngeal (NP) colonization caused by respiratory bacteria results in natural immunization of the host. To identify Mcat antigens as vaccine candidates, we evaluated the development of naturally induced antibodies to 5 Mcat surface proteins in children 6-30 months of age during Mcat NP colonization and AOM.

METHODS

Human serum IgG against the recombinant Mcat proteins, outer membrane protein (OMP) CD, oligopeptide permease (Opp)A, hemagglutinin (Hag), Moraxella surface protein (Msp)22, and PilA clade 2 (PilA2) was quantitated by using an ELISA assay.

RESULTS

There were 223 Mcat NP colonization episodes documented in 111 (60%) of 184 children in the study. Thirty five Mcat AOM episodes occurred in 30 (16%) of 184 children. All 5 Mcat candidate vaccine antigens evaluated stimulated a significant rise in serum IgG levles over time from 6 to 36 months of age (P<0.001), with a rank order as follows: Msp22=OppA>OMP CD=Hag=PilA2. Children with no detectable Mcat NP colonization showed a higher serum IgG level against OppA, Hag, and Msp22 compared to those with Mcat NP colonization (P<0.05). Individual data showed that some children responded to AOM with an antibody increase to one or more of the studied Mcat proteins but some children failed to respond.

CONCLUSIONS

Serum antibody to Mcat candidate vaccine proteins OMP CD, OppA, Msp22, Hag, and PilA2 increased with age in naturally immunized children age 6-30 months following Mcat NP colonization and AOM. High antibody levels against OppA, Msp22, and Hag correlated with reduced carriage. The results support further investigation of these vaccine candidates in protecting against Mcat colonization and infection.

Impact of the 13-valent pneumococcal conjugate vaccine (pcv13) on invasive pneumococcal disease and carriage in Alaska

BACKGROUND

Alaska Native (AN) children have experienced high rates of invasive pneumococcal disease (IPD). In March 2010, PCV13 was introduced statewide in Alaska. We evaluated the impact of PCV13 on IPD in children and adults, 45 months after introduction.

METHODS

Pneumococcal sterile site isolates, reported through state-wide surveillance, were serotyped using standard methods. We defined a pre-PCV13 time period 2005-2008 and post-PCV13 time period April 2010-December 2013; excluding Jan 2009-March 2010 because PCV13 was introduced pre-licensure in one high-risk region in 2009.

RESULTS

Among Alaska children <5 years, PCV13 serotypes comprised 65% of IPD in the pre-PCV13 period and 26% in the PCV13 period. Among all Alaska children <5 years, IPD rates decreased from 60.9 (pre) to 25.4 (post) per 100,000/year (P<0.001); PCV13 serotype IPD decreased from 37.7 to 6.4 (P<0.001). Among AN children <5 years, IPD rates decreased from 149.2 to 60.8 (P<0.001); PCV13 serotype IPD decreased from 87.0 to 17.4 (P<0.001); non-PCV13 serotype IPD did not change significantly. Among persons 5-17 and ≥45 years, the post-vaccine IPD rate was similar to the baseline period, but declined in persons 18-44 years (39%, P<0.001); this decline was similar in AN and non-AN persons (38%, P=0.016, 43%, P=0.014, respectively).

CONCLUSIONS

Forty-five months after PCV13 introduction, overall IPD and PCV13-serotype IPD rates had decreased 58% and 83%, respectively, in Alaska children <5 years of age when compared with 2005-2008. We observed evidence of indirect effect among adults with a 39% reduction in IPD among persons 18-44 years.

Epidemiology of Neisseria meningitidis infections: case distribution by age and relevance of carriage

Notwithstanding different meningococcal serogroups have changed their distribution and their impact in different age classes over time, N. meningitidis' invasive diseases are a major public health issue worldwide, due to the related complications and severe sequelae. Nowadays, the highest rates of invasive disease are registered in children younger than 1 year of age, with a second lesser peak in adolescents and young adults (15-25 years of age). On the contrary, the prevalence of carriage is low in newborns and in school-age children, and increases during adolescence and young-adult age; then it decreases again in older age. N. meningitidis' infection prevalence has greatly decreased in Europe and North America thanks to the use of conjugate vaccines (MenC and MenACWY) as well as the incidence of invasive disease due to serogroup A in sub-saharian Africa after the introduction of MenAfriVac conjugate vaccine. The great success of conjugate vaccines is related not only to the direct protection from disease but also to the impact on carriage; this latter allows an indirect protection of unimmunized subjects. For these reasons, the implementation of immunization with the new generation vaccines in the age classes most impacted by disease and carriage (first year of life, adolescence and young adulthood) could permit to achieve an extraordinary decrease of the incidence of meningococcal disease.

Historical outbreak of Salmonella hadar

BACKGROUND

This article reports a historical outbreak of Salmonella hadar in a maternity setting. The outbreak occurred following admission of an infected index case, with transmission to 11 other individuals over a three-month period in a maternity and neonatal unit.

METHODS

Despite rigorous assessment of clinical practices, screening of patients and staff, and review of disinfection and sterilization policies, the outbreak was difficult to control. This possibly reflects the capacity of S. hadar to survive well in the environment, and cause prolonged and asymptomatic carriage with intermittent shedding.

FINDINGS

It is likely that the index case was a mother who had contracted infection after eating suspect food. Additionally, infection may have been perpetuated by shared use of tubes of yellow soft paraffin for lubrication of digital rectal thermometers.

CONCLUSION

This outbreak emphasizes the difficulties in controlling outbreaks of S. hadar infection in an obstetric/neonatal setting, and also emphasizes the importance of early stool sampling in any patient with diarrhoeal symptoms.

Impact of livestock-associated MRSA in a hospital setting

OBJECTIVES

The Netherlands is known for a stringent search and destroy policy to prevent spread of MRSA. In the hospital setting, livestock-associated MRSA (LA-MRSA) is frequently found in patients coming from the high density farming area in the south of the Netherlands. The aim of the study was to determine the contribution of LA-MRSA in the epidemiology of MRSA in cases found following the Dutch search and destroy policy.

PATIENTS AND METHODS

From two hospitals serving a population of 550,000 persons all data on MRSA cultures and subsequent control measures from 2008 and 2009 were retrospectively collected and analyzed.

RESULTS

A total of 3856 potential index patients were screened for MRSA, 373 (9.7%) were found to be positive, 292 ( 78%) LA-MRSA and 81 (22%) non-LA-MRSA respectively. No secondary cases were found among contact research in persons exposed to LA-MRSA (0/416), whereas similar contact research for non-LA-MRSA resulted in 83 (2.5%) secondary cases. LA-MRSA were rarely found to cause infections.

CONCLUSIONS

LA-MRSA is more prevalent than non-LA-MRSA in Dutch Hospitals in the South of the Netherlands. However, retrospectively studied cases show that the transmission rate for LA-MRSA was much lower than for non-LA-MRSA. This suggest that infection control practices for LA-MRSA may possibly be less stringent than for non-LA-MRSA.

Meningococcal carriage in adolescents in the United Kingdom to inform timing of an adolescent vaccination strategy

OBJECTIVES

Recent development of serogroup B meningococcal (MenB) vaccines highlights the importance of pharyngeal carriage data, particularly in adolescents and young adults, to inform implementation strategies. We describe current UK carriage prevalence in this high risk population and compare methods of carriage detection.

METHODS

In this multisite study, pharyngeal swabs were collected on 3-4 occasions over 6-12 months, from 1040 school and university students, aged 10-25 years. Meningococcal carriage was detected by standard culture combined with seroagglutination or PCR of cultured isolates, or by direct PCR from swab. The factor H binding protein (fHBP) variants present in meningococcal isolates were determined.

RESULTS

Meningococcal serogroups B and Y were most common, with carriage up to 6.5% and 5.5% respectively, increasing throughout adolescence. Identification by seroagglutination was often unreliable, and the sensitivity of direct PCR detection was 66% compared to culture combined with PCR. Of MenB isolates, 89.1% had subfamily A variants of fHBP. The acquisition rate of MenB carriage was estimated at 2.8 per 1000 person-months.

CONCLUSIONS

If vaccination is to precede the adolescent rise in MenB carriage, these data suggest it should take place in early adolescence. Studies assessing vaccine impact should use molecular methods to detect carriage.

Anatomical patterns of colonization of pets with staphylococcal species in homes of people with methicillin-resistant Staphylococcus aureus (MRSA) skin or soft tissue infection (SSTI)

Methicillin-resistant strains of Staphylococcus aureus (MRSA), Staphylococcus pseudintermedius (MRSP), and other pathogenic staphylococci can cause infections in companion animals and humans. Identification of colonized animals is fundamental to research and practice needs, but harmonized methods have not yet been established. To establish the optimal anatomic site for the recovery of methicillin-resistant coagulase positive staphylococci (CPS), survey data and swabs were collected from 196 pets (dogs, cats, reptiles, birds, fish and pocket pets) that lived in households with an MRSA-infected person. Using broth-enrichment culture and PCR for speciation, S. aureus was identified in 27 of 179 (15%) pets sampled at baseline and 19 of 125 (15%) pets sampled at a three-month follow-up home visit. S. pseudintermedius was isolated from 33 of 179 (18%) pets sampled at baseline and 21 of 125 (17%) of pets sampled at follow-up. The baseline MRSA and MRSP prevalence was 8% and 1% respectively from 145 mammalian pets. The follow-up MRSA and MRSP prevalence was 7% and <1% respectively from 95 mammalian pets. The mouth was the most sensitive single site sampled for isolation of S. aureus and S. pseudintermedius in mammals. In a subset of pets, from which all available isolates were identified, dual carriage of S. aureus and S. pseudintermedius was 22% at baseline and 11% at follow-up. These results identify the mouth as the most sensitive site to screen for pathogenic staphylococci and suggest that it should be included in sampling protocols.

Neisserial Molecular Adaptations to the Nasopharyngeal Niche

The exclusive reservoir of the genus Neisseria is the human. Of the broad range of species that comprise the Neisseria, only two are frequently pathogenic, and only one of those is a resident of the nasopharynx. Although Neisseria meningitidis can cause severe disease if it invades the bloodstream, the vast majority of interactions between humans and Neisseria are benign, with the bacteria inhabiting its mucosal niche as a non-invasive commensal. Understandably, with the exception of Neisseria gonorrhoeae, which preferentially colonises the urogenital tract, the neisseriae are extremely well adapted to survival in the human nasopharynx, their sole biological niche. The purpose of this review is to provide an overview of the molecular mechanisms evolved by Neisseria to facilitate colonisation and survival within the nasopharynx, focussing on N. meningitidis. The organism has adapted to survive in aerosolised transmission and to attach to mucosal surfaces. It then has to replicate in a nutrition-poor environment and resist immune and competitive pressure within a polymicrobial complex. Temperature and relative gas concentrations (nitric oxide and oxygen) are likely to be potent initial signals of arrival within the nasopharyngeal environment, and this review will focus on how N. meningitidis responds to these to increase the likelihood of its survival.

Large hospital outbreak of KPC-2-producing Klebsiella pneumoniae: investigating mortality and the impact of screening for KPC-2 with polymerase chain reaction

BACKGROUND

Multi-drug-resistant Klebsiella pneumoniae carbapenemase (KPC)-2-producing K. pneumoniae are an increasing cause of healthcare-associated infections worldwide.

AIMS

To investigate the impact of clinical infection on mortality, and examine the effect of use of KPC-2-specific polymerase chain reaction (PCR) on the time to contact isolation during an outbreak.

METHODS

Cases were defined as patients clinically infected or colonized with KPC-2-producing K. pneumoniae between June 2010 and July 2012. Cases were described by demographic and health characteristics, and the association between infection and mortality, adjusted for comorbidities and demographic characteristics, was determined using Poisson regression with robust standard errors. A comparison was made between the time to contact isolation with a culture-based method and PCR using Wilcoxon's rank sum test.

FINDINGS

Of 72 cases detected, 17 (24%) had undergone transplantation and 21 (29%) had a malignancy. Overall, 35 (49%) cases were clinically infected, with pneumonia and sepsis being the most common infections. Infection was an independent risk factor for mortality (risk ratio 1.67, 95% confidence interval 0.99-2.82). The median time to contact isolation was 1.5 days (range 0-21 days) using PCR and 5.0 days (range 0-39 days) using culture-based methods (P = 0.003). Intermittent negative tests were observed in 48% (14/29) of cases tested using culture-based methods.

CONCLUSION

KPC-2-producing K. pneumoniae mainly affect severely ill patients. Half of the cases developed clinical infection, associated with increased risk of death. As PCR accelerates isolation and provides the opportunity for preventive measures in colonized cases, its use should be implemented promptly during outbreaks. Further studies are needed to enhance knowledge about KPC detection patterns and to adjust screening guidelines.

Persistent Staphylococcus aureus nasal colonization in ambulatory human immunodeficiency virus-infected patients in Nigeria: Risk factors and molecular features

This longitudinal study on Staphylococcus aureus colonization in Nigerian human immunodeficiency virus patients (n = 187) found a trend towards a higher proportion of persistent S. aureus carriage in patients with advanced human immunodeficiency virus infection, low CD4+ cell counts, and a predominance of isolates belonging to ST8/spa-CC064 in persistent carriers.

Acquisition of Streptococcus pneumoniae in South African children vaccinated with 7-valent pneumococcal conjugate vaccine at 6, 14 and 40 weeks of age

BACKGROUND

Seven-valent pneumococcal conjugate vaccine (PCV7) was introduced into the South African immunization program using 6, 14 and 40 weeks dosing schedule (2+1), with no catch-up in older children since April 2009. We investigated pneumococcal colonization acquisition in children who received this schedule and also compared it to historical cohorts of PCV-naïve children (n=123 in 2007) and children who received a 3+1 PCV7 schedule (n=124 in 2005/06).

METHODS

Two hundred and fifty children aged 6-12 weeks were enrolled from December 2009 to April 2010. Participants had nasopharyngeal swabs collected on eight occasions between enrolment and 2-years of age. Standard methods were undertaken for bacterial culture and Streptococcus pneumoniae were serotyped using the Quellung method. Pneumococcal and Staphylococcus aureus colonization in the present study was compared to colonization in two historical longitudinal cohorts.

RESULTS

S. pneumoniae was identified in 1081 (61.4%) of 1761 swabs collected in the current cohort. Pneumococcal colonization peaked at 41-weeks of age (76.8%) and decreased to 62.8% by 2-years of age (p=0.002); PCV7-serotype colonization decreased during the same period from 28.6% to 15.6% (p=0.001). Children from the current cohort compared to PCV-naïve children were less likely to be colonized by PCV7-serotypes from 40-weeks to 2-years of age and acquired PCV7-serotypes less frequently. No differences in overall pneumococcal, PCV7-serotype and non-PCV7-serotype colonization or new serotype acquisitions were detected comparing the current cohort to the historical cohort who received the 3+1 PCV7 schedule. Staphylococcus aureus colonization was similar in all three cohorts.

CONCLUSION

A 2+1 PCV7 schedule implemented in South Africa was temporally associated with reduced risk of vaccine-serotype colonization compared to historically unvaccinated children. Also, vaccine-serotype acquisition rate using the 2+1 schedule was similar to that in the 3+1 dosing cohort, suggesting that similar indirect protection against pneumococcal disease could be derived from either schedule in South Africa.

Detection of co-colonization with Streptococcus pneumoniae by algorithmic use of conventional and molecular methods

Detection of pneumococcal carriage by multiple co-colonizing serotypes is important in assessing the benefits of pneumococcal conjugate vaccine (PCV). Various methods differing in sensitivity, cost and technical complexity have been employed to detect multiple serotypes of pneumococcus in respiratory specimens. We have developed an algorithmic method to detect all known serotypes that preserves the relative abundance of specific serotypes by using Quellung-guided molecular techniques. The method involves culturing respiratory swabs followed by serotyping of 100 colonies by either capsular (10 colonies) or PCR (90 colonies) reactions on 96-well plates. The method was evaluated using 102 nasal swabs from children carrying pneumococcus. Multiple serotypes were detected in 22% of carriers, compared to 3% by World Health Organization (WHO)-recommended morphology-based selection of 1 to 3 colonies. Our method, with a processing cost of $87, could detect subdominant strains making up as low as 1% of the population. The method is affordable, practical, and capable of detecting all known serotypes without false positive reactions or change in the native distribution of multiple serotypes.

Value of an active surveillance policy to document clearance of meticillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci amongst inpatients with prolonged admissions

This article reports the impact of an active surveillance policy to identify clearance of meticillin-resistant Staphylococcus aureus (MRSA) or vancomycin-resistant enterococci (VRE) in known colonized inpatients with prolonged admissions in order to discontinue isolation precautions. Amongst 365 colonized patients with hospital admissions exceeding 30 days, clearance rates of 11% for MRSA and 18% for VRE were found after a median of 23 days and 26.5 days, respectively, resulting in a saving of 2152 patient-days of contact precautions over one year. This has proven to be a cost-beneficial policy.

Are the risk factors associated with Staphylococcus aureus nasal carriage in patients the same than in healthy volunteers? Data from a cohort of patients scheduled for orthopedic material implantation

The risk factors for Staphylococcus aureus nasal carriage have been mainly defined in healthy volunteers. Using data from a large multicenter prospective clinical cohort of orthopedic surgical patients we showed that obesity (BMI > 30) and younger age were independent risk factors for persistent carriage. In the absence of recommendations for S aureus decolonization in orthopedic surgery, this study suggests that at least obese patients should be targeted to prevent surgical site infections.

Staphylococcus aureus nasopharyngeal carriage in rural and urban northern Vietnam

Background

Staphylococcus aureus is a common human pathogen that can colonise the respiratory tract and cause infection. Here we investigate the risk factors associated with nasopharyngeal carriage of S. aureus (including methicillin-resistant S. aureus [MRSA]) in Vietnam.

Methods

Between February and June 2012, nasal and pharyngeal swabs for S. aureus culture, and demographic and socioeconomic data were taken from 1016 participants in urban and rural northern Vietnam, who were randomly selected from pre-specified age strata.

Results

Overall S. aureus prevalence was 303/1016 (29.8%; adjusted for age: 33.8%). Carriage in the main cohort was found to be associated with younger age (≤5 years [OR 3.13, CI 1.62–6.03]; 6–12 [OR 6.87, CI 3.95–11.94]; 13–19 [OR 6.47, CI 3.56–11.74]; 20–29 [OR 4.73, CI 2.40–9.31]; 30–59 [OR 1.74, CI 1.04–2.92); with ≥60 as reference), living in an urban area (OR 1.36, CI 1.01–1.83) and antibiotics use (OR 0.69, CI 0.49–0.96). MRSA was detected in 80/1016 (7.9%). Being aged ≤5 years (OR 4.84, CI 1.47–15.97); 6–12 (OR 10.21, CI 3.54–29.50); 20–29 (OR 4.01, CI 1.09–14.77) and wealth (>3/5 wealth index, OR 1.63 CI 1.01–2.62) were significant risk factors for MRSA carriage.

Conclusions

Nasopharyngeal carriage of S. aureus is present in one-third of the Vietnamese population, and is more prevalent among children. Pharyngeal carriage is more common than nasal carriage. Risk factors for S. aureus (including MRSA) carriage are identified in the community.

Meningococcal carriage prevalence in university students, 1824 years of age in Santiago, Chile

INTRODUCTION

Neisseria meningitidis invasive disease is a major public health problem. Pharyngeal carriage is considered a prerequisite for invasive infection. Prevalence reaches 10% in general population and up to 30% in the 20-24 years age group. The aim of this study was to asses pharyngeal carriage prevalence in healthy subjects aged 18-24 years, and as secondary endpoints evaluate known risk factors, to identify serogroups and sequence in the isolated strains.

METHODS

Cross-sectional study in 500 healthy subjects; students from Universidad de Chile aged 18-24 years, Santiago, Chile, October 2012. Each subject underwent a risk factor survey prior to throat culture sampling. Samples were processed in one central Microbiology Laboratory of Hospital Luis Calvo Mackenna and serogrouping and sequencing was performed at Instituto de Salud Pública de Chile.

RESULTS

We obtained throat samples from 500 healthy subjects, 20 (4%) positive for N. meningitidis. Of positive strains 20% were serogroup B, 15% W and the rest non groupable. The median age was 20 years, 50% were men. Of the risk factors evaluated, 24% were current smokers, 16% shared a room, 72% had kissed someone during the last month, 64% had gone to pub and 76% had consumed alcohol in the same period of time.

DISCUSSION

Literatures meningococcal carriage prevalence reaches up to 30% in people aged 18-24 years. Prevalence in our study was 4%. Different interpretations could be given; one could be the absence of overcrowding in our students because of the lack of dorms in our scholar system and also the characteristics of our enrolled group.

CONCLUSIONS

Our results suggest the necessity to extend the study to other age groups and to other cities, to better understand the Chilean reality, as well as others regions of America, considering that these results cannot be extrapolated to another countries.

Density and duration of experimental human pneumococcal carriage

The density and duration of pneumococcal carriage are considered to affect the likelihood of transmission and invasive disease. Because of its importance in both spreading and causing disease, carriage has been suggested as an endpoint in future vaccine studies. Culture is the current gold standard for detection, but may not be sensitive enough to detect changes at low density. Healthy adult volunteers received an intranasal inoculation of Streptococcus pneumoniae serotype 6B. Pneumococcal density in nasal washes collected at six time-points post-inoculation was determined by culture and quantitative PCR (qPCR). Natural pneumococcal carriers detected at initial screening were followed in parallel. In 331 nasal washes from 79 volunteers, the sensitivity and specificity of pneumococcal detection by qPCR, as compared with culture, were 92.3% and 75.9%. The estimation of pneumococcal density by culture and qPCR was highly correlated (r_s = 0.73, p <0.0001), although qPCR had a lower detection limit. Pneumococcal density fluctuated within a carriage episode, and occasionally fell below the detection limit of both methods. The duration of carriage episodes was underestimated when only one method was used. Similar fluctuations in density were observed in natural carriers. Pneumococcal carriage is a dynamic event. Culture and qPCR are complementary for surveying the density and duration of pneumococcal carriage episodes.

Standard method for detecting upper respiratory carriage of Streptococcus pneumoniae: updated recommendations from the World Health Organization Pneumococcal Carriage Working Group

In 2003 the World Health Organization (WHO) convened a working group and published a set of standard methods for studies measuring nasopharyngeal carriage of Streptococcus pneumoniae (the pneumococcus). The working group recently reconvened under the auspices of the WHO and updated the consensus standard methods. These methods describe the collection, transport and storage of nasopharyngeal samples, as well as provide recommendations for the identification and serotyping of pneumococci using culture and non-culture based approaches. We outline the consensus position of the working group, the evidence supporting this position, areas worthy of future research, and the epidemiological role of carriage studies. Adherence to these methods will reduce variability in the conduct of pneumococcal carriage studies undertaken in the context of pneumococcal vaccine trials, implementation studies, and epidemiology studies more generally so variability in methodology does not confound the interpretation of study findings.

Implications of targeted versus universal admission screening for meticillin-resistant Staphylococcus aureus carriage in a London hospital

Universal admission screening for meticillin-resistant Staphylococcus aureus (MRSA) has been performed in England since 2010. We evaluated the predictive performance of a regression model derived from the first year of universal screening for detecting MRSA at hospital admission. If we had used our previous targeted screening policy, 75% fewer patients (21,699 per year) would have been screened. However, this would have identified only ~55% of all MRSA carriers, 65% of healthcare-associated MRSA strains, and 40% of community-associated strains. Failing to identify ~45% of patients (262 per year) carrying MRSA at hospital admission may have implications for MRSA control.