Using genomics to examine the persistence of Streptococcus pneumoniae serotype 19A in Ireland and the emergence of a sub-clade associated with vaccine failures.

BACKGROUND: Streptococcus pneumoniae serotype 19A remains a significant cause of invasive pneumococcal disease (IPD) in Ireland despite the successful introduction of a 13-valent pneumococcal conjugate vaccine (PCV13) in 2010 which reduced the overall incidence of IPD in children. METHODS: Invasive Streptococcus pneumoniae serotype 19A isolates from the Irish reference laboratory between 2007-08 and 2017-18 were analysed using whole genome sequencing (WGS) to investigate the persistence of this vaccine-preventable serotype. We compared the entire national 19A collection to other international collections using a standardised nomenclature of Global Pneumococcal Sequencing Clusters (GPSC). RESULTS: Expansion of GPSCs and clonal complexes (CCs) may have been associated with vaccine introduction and antimicrobial prescribing policies. A sub-clade of GPSC1-CC320 (n = 25) unique to Ireland, included five of the ten vaccine failures/breakthrough cases identified (p = 0.0086). This sub-clade was not observed in a global GPSC1-CC320 collection. All isolates within the sub-clade (n = 25) contained a galE gene variant rarely observed in a global pneumococcal collection (n = 37/13454, p < 0.001) nor within GPSC1-CC320 (n = 19/227) (p < 0.001). The sub-clade was estimated to have emerged at the start of the PCV-vaccine era (ancestral origin 2000, range 1995-2004) and expanded in Ireland, with most isolated after PCV13 introduction (n = 24/25). CONCLUSIONS: The identification of a sub-clade/variant of serotype 19A highlights the benefit of using WGS to analyse genotypes associated with persistence of a preventable serotype of S. pneumoniae. Particularly as this sub-clade identified was more likely to be associated with IPD in vaccinated children than other 19A genotypes. It is possible that changes to the galE gene, which is involved in capsule production but outside of the capsular polysaccharide biosynthesis locus, may affect bacterial persistence within the population. Discrete changes associated with vaccine-serotype persistence should be further investigated and may inform vaccine strategies.

Is It Time To Review The Vaccination Strategy To Protect Adults Against Invasive Pneumococcal Disease?

Pneumococcal conjugate vaccines (PCVs) have reduced the predominant serotypes causing invasive pneumococcal disease (IPD). We assessed the impact of the paediatric 7- and 13-valent pneumococcal conjugate vaccines (PCV7 and PCV13) among older adults. We compared serotype-specific incidence rates from 2007/08 to 2016/17, expressed as incidence rate ratios (IRR). Introducing PCV7 and PCV13 into the childhood immunisation programme resulted in a decline in these serotypes in adults ≥65 years of age, with PCV7 serotypes decreasing by 85% (IRR=0.11, 95%CI: 0.05-0.22, p<0.0001) and PCV13 serotypes not included in PCV7 (PCV13-7), decreasing by 9% (IRR=0.68, 95%CI: 0.40-1.16, p=0.134). However, there was a significant increase in serotypes only found in the 23-valent polysaccharide vaccine, PPV23-PCV13: IRR=2.57, 95%CI: 1.68-4.03, p<0.0001, and non-vaccine types (NVTs), IRR=3.33, 95%CI: 1.75-6.84, p=0.0001. The decline of IPD associated with PCV7/13 serotypes and the increase in PPV23-PCV13 serotypes indicates clear serotype replacement. Increasing PPV23 uptake could still reduce the burden of disease for this population.

The epidemiology of invasive pneumococcal disease in older adults in the post-PCV era. Has there been a herd effect?

The 7 and 13-valent pneumococcal conjugate vaccines (PCVs) have reduced the incidence of invasive pneumococcal disease (IPD) in children in many countries. The objective of this work was to assess the impact of PCVs and potential herd-protection in older adults in Ireland. IPD notification and typing data from adults ⩾65 years of age from July 2007 to June 2016 was assessed using national surveillance data. There was a 94% reduction in PCV7 serotypes from 2007-2008 to 2015-2016, incidence rate ratio (IRR 0·05, P < 0·0001). However, there was no decline in the additional PCV13 (PCV13-7) serotypes over the same period (IRR 0·90) nor in comparison with the pre-PCV13 period 2009-2010 (IRR 0·92). The incidence of serotypes in the 23-valent pneumococcal polysaccharide vaccine only (PPV23-PCV13) and non-vaccine types (NVTs) increased significantly (IRR 2·17, P = 0·0002 and IRR 3·43, P = 0·0001 respectively). Consequently, the overall IPD incidence rate in adults has remained relatively unchanged (from 28·66/100 000 to 28·88/100 000, IRR 1·01, P = 0·9477). Serotype 19A and NVTs were mainly responsible for penicillin resistance in recent years. The decline of PCV7 serotypes indicate that the introduction of PCV7 resulted in herd-protection for adults. However, increases in PPV23-PCV13 and NVTs suggest that changes in vaccination strategy amongst older adults are needed to build on the success of PCVs in children.

Klebsiella pneumoniae bloodstream infection, antimicrobial resistance and consumption trends in Ireland: 2008 to 2013.

This study aimed to describe the epidemiology and antimicrobial resistance trends of Klebsiella pneumoniae bloodstream infection (BSI) in Ireland, in conjunction with national antimicrobial consumption data, during the period 2008 to 2013. A retrospective cohort study of K. pneumoniae BSI cases was conducted, based on notifications from Irish microbiology laboratories to the Health Protection Surveillance Centre (HPSC). In total, 1942 K. pneumoniae BSI cases were identified over 6 years, with 310 reported in 2008 and 326 reported in 2013. From 2008 to 2013, the proportion of isolates resistant to co-amoxiclav (24 % versus 29 %), piperacillin-tazobactam (11 % versus 27 %), third generation cephalosporins (3GC) (11 % versus 21 %), fluoroquinolones (13 % versus 21 %) and gentamicin (11 % versus 17 %) increased overall, concurrent with increasing national rates of antimicrobial consumption in Ireland (acute hospitals: 35.87 versus 39.77 defined daily doses (DDD) per 100 bed days used (BDU); and community: 6.38 versus 7.85 DDD per 1000 inhabitants per day (DID)). Enhanced data on the patient's admission route was available for 735 (38 %) cases. Overall, 51 % (n = 378) were categorised as 'acquired in the reporting hospital'. The all-cause mortality was 20 %, with 115 deaths, 101 (88 %) of whom died within 30 days of blood culture sampling date. K. pneumoniae is the second most common cause of Gram-negative BSI in Ireland, with most cases healthcare-associated and an all-cause mortality of 20 % reported in this study. Annual increases in resistance to different antimicrobial classes and in a multi-drug resistant phenotype have been observed, concurrent with increasing national broad spectrum antimicrobial consumption. These trends portend a risk to patient outcomes and highlight the urgency for individual prescribers to evaluate their antimicrobial prescribing habits in hospitals, long-term care and community settings.

Increased incidence of invasive group A streptococcal disease in Ireland, 2012 to 2013.

Invasive group A streptococcal (iGAS) infections have been notifiable in Ireland since 2004. Incidence rates (2004-2011) have ranged from 0.8 to 1.65 per 100,000. In 2012, the iGAS rate rose to 2.66 per 100,000 and was associated with a high proportion of emm1 isolates. A further increase in January to June 2013 has been associated with increased prevalence of emm3. Public health departments and clinicians have been alerted to this increase.

Carbapenemase-producing Enterobacteriaceae in Irish critical care units: results of a pilot prevalence survey, June 2011.

The epidemiology of carbapenemase-producing Enterobacteriaceae (CPE) in Ireland is changing, with an increase in the number of reported cases in late 2010 and early 2011. Reported cases were predominantly linked to critical care units. In June 2011, a four-week national pilot survey took place in 40 Irish critical care units (37 adult and three paediatric) to examine the prevalence of rectal carriage of CPE and inform national CPE screening guidelines. A total of 760 screening swabs were taken over the study period, and CPE were not detected in any of the participating critical care units.

Invasive Group A streptococcal disease in Ireland, 2004 to 2010.

Invasive group A streptococcal infections (iGAS) are a major clinical and public health challenge. iGAS is a notifiable disease in Ireland since 2004. The aim of this paper is to describe the epidemiology of iGAS in Ireland for the first time over the seven-year period from 2004 to 2010. The Irish national electronic infectious disease reporting system was used by laboratories to enter the source of iGAS isolates, and by departments of public health to enter clinical and epidemiological details. We extracted and analysed data from 1 January 2004 to 31 December 2010. Over the study period, 400 iGAS cases were notified. The annual incidence of iGAS doubled, from 0.8 per 100,000 population in 2004 to 1.6 in 2008, and then remained the same in 2009 and 2010. The reported average annual incidence rates were highest among children up to five years of age (2.3/100,000) and adults aged over 60 years (3.2/100,000). The most common risk factors associated with iGAS were skin lesions or wounds. Of the 174 people for whom clinical syndrome information was available, 28 (16%) cases presented with streptococcal toxic shock syndrome and 19 (11%) with necrotising fasciitis. Of the 141 cases for whom seven-day outcomes were recorded, 11 people died with iGAS identified as the main cause of death (seven-day case fatality rate 8%). The notification rate of iGAS in Ireland was lower than that reported in the United Kingdom, Nordic countries and North America but higher than southern and eastern European countries. The reasons for lower notification rates in Ireland compared with other countries may be due to a real difference in incidence, possibly due to prescribing practices, or due to artefacts resulting from the specific Irish case definition and/or low reporting in the early stages of a new surveillance system. iGAS disease remains an uncommon but potentially severe disease in Ireland. Ongoing surveillance is required in order to undertake appropriate control measures and gain a greater understanding of this disease.

Serotype distribution of Streptococcus pneumoniae causing invasive disease in the Republic of Ireland.

The 7-valent pneumococcal conjugate vaccine (PCV7) was included in the routine infant immunization schedule in Ireland in September 2008. We determined the serotype of 977 S. pneumoniae isolates causing invasive disease between 2000-2002 and 2007-2008, assessed for the presence of the recently described serotype 6C and determined the susceptibility of isolates during 2007-2008 to penicillin and cefotaxime. Serotype 14 was the most common serotype during both periods and 7·7% of isolates previously typed as serotype 6A were serotype 6C. During 2000-2002 and 2007-2008, PCV7 could potentially have prevented 85% and 74% of invasive pneumococcal disease in the target population (i.e. children aged <2 years), respectively. The level of penicillin non-susceptibility was 17% in 2007-2008. Ongoing surveillance of serotypes is required to determine the impact of PCV7 in the Irish population and to assess the potential of new vaccines with expanded valency.

Irish-1 and Irish-2: UK epidemic meticillin-resistant Staphylococcus aureus strains associated with Northern Ireland.

Since 1998, an increasing number of meticillin-resistant Staphylococcus aureus (MRSA) isolates with one of two characteristic phage patterns have been referred to the authors' laboratory from Northern Ireland. These strains were designated 'Irish-1' and 'Irish-2'. Analysis of 956 submitted isolates classified as Irish-1 or Irish-2 showed that 97% of the former and 95% of the latter were from Northern Ireland. Only 0.2% and 3%, respectively, were from England. Eleven Irish-2 isolates had been referred from Western Australia as representatives of an epidemic strain originally isolated there in 1994. Ninety isolates with the Irish-1 phage pattern and 91 isolates with the Irish-2 phage pattern, from numerous hospitals, were characterized by SmaI pulsed-field gel electrophoresis (PFGE), toxin gene carriage and antibiotic susceptibility. PFGE showed that, within each collection, a few isolates represented unrelated strains, but the majority were within six band differences of the most common profiles. Half of the Irish-1 isolates were homogeneous, with 22 DNA profiles among the remainder. Irish-2 isolates had two common profiles, D1 and D2, equally divided between one-third of the isolates and differing from each other by two bands; the remaining isolates shared 31 DNA profiles. Cluster analysis showed some overlap in DNA profiles between the Irish-1 and Irish-2 strains, but clear separation from other epidemic MRSA strains. There was no obvious correlation between PFGE profile and either antibiotic resistance pattern or toxin gene possession. All but three Irish-1 isolates possessed only the staphylococcal enterotoxin A (sea) gene, whereas almost all Irish-2 isolates were negative for all 12 enterotoxin genes. Sixty-nine percent of Irish-2 isolates were resistant to ciprofloxacin, erythromycin, kanamycin, neomycin and streptomycin, while 90% of Irish-1 isolates were resistant to all these plus gentamicin and mupirocin. All isolates were sensitive to quinupristin/dalfopristin, teicoplanin and vancomycin. Urease production was negative in both strains. The results suggest that Irish-1 and Irish-2 are distinct epidemic strains, identifiable by phage typing, DNA profiles, antibiotic resistance and toxin gene carriage.

Impact of the European Antimicrobial Resistance Surveillance System on the development of a national programme to monitor resistance in Staphylococcus aureus and Streptococcus pneumoniae in Ireland, 1999-2003.

Presented here is the 5-year impact of a national antimicrobial resistance surveillance system in Ireland, which was introduced in accordance with the European Antimicrobial Resistance Surveillance System (EARSS). Participation in EARSS began in Ireland in 1999. Initially, 12 laboratories serving a mix of general and tertiary hospitals participated, but by 2003, participation had increased to 28 laboratories with a population coverage of 89%. During 1999-2003, 4,146 episodes of Staphylococcus aureus bacteraemia were reported, and methicillin resistance was detected in 1,709 (41.2%) of these isolates. Over the same period, 1,245 invasive (blood or cerebrospinal fluid) episodes of Streptococcus pneumoniae infection were reported, and 160 (12.9%) isolates were found to be non-susceptible to penicillin, with 23 (1.8%) demonstrating high-level penicillin resistance. By 2003, most Irish hospitals were participating in EARSS, which has been a catalyst for the development of a national antimicrobial resistance surveillance programme.

Emergence, spread, and characterization of phage variants of epidemic methicillin-resistant Staphylococcus aureus 16 in England and Wales.

Epidemic methicillin-resistant Staphylococcus aureus 16 (EMRSA-16) and EMRSA-15 are the two most important and prevalent EMRSA strains found in the United Kingdom and have also been found in a number of European countries and the United States. We describe for the first time the spread of an EMRSA strain (EMRSA-16) from its point of origin in one hospital to the surrounding hospitals and regions over the following 2 years. In the first 18 months after its original appearance, 136 hospitals referred EMRSA-16 isolates for typing, and interhospital and intraregional spread were reported: it was more prevalent in males between 60 and 80 years old and was isolated from sputum and throat more often than EMRSA-15. Important characteristics, e.g., carriage of the enterotoxin A (sea) and toxic shock syndrome toxin (tst) genes and production of urease, are described. Phage-variant strains of EMRSA-16 which share some of the characteristics of the classical strain, including toxin carriage and urease production, emerged, but without genotypic investigations, their relationship could only be inferred. A total of 129 clinical isolates from 52 hospitals, collected between March 1998 and April 1999 and representing classical EMRSA-16 (49 isolates) or phage variants (80 isolates), were compared by phage typing, pulsed-field gel electrophoresis (PFGE) following SmaI macrorestriction, antimicrobial susceptibility testing, urease production, and PCR detection of toxin gene carriage. PFGE analysis revealed 29 profiles, A1 to A29, with A1 representing the prototypic strain, NCTC 13143. All other profiles differed from A1 by 1 to 6 bands, but some differed from each other by up to 10 bands.

Antimicrobial susceptibility of invasive isolates of Streptococcus pneumoniae in Ireland.

Between January 1999 and June 2002, 646 invasive isolates of Streptococcus pneumoniae were collected in Ireland. MICs of penicillin, ciprofloxacin, cefotaxime, moxifloxacin and linezolid were determined by Etest methodology. Eighty-seven (13.5%) isolates showed intermediate resistance to penicillin, while seven (1.1%) showed high-level resistance. Eighty-seven (13.5%) isolates were resistant to erythromycin, but all isolates were susceptible to cefotaxime, moxifloxacin and linezolid. The prevalence of pneumococcal isolates non-susceptible to penicillin in Ireland is worryingly high, but currently there are alternative agents available to treat invasive infection.

Identification and characterization of phage variants of a strain of epidemic methicillin-resistant Staphylococcus aureus (EMRSA-15).

EMRSA-15 is one of the most important strains of epidemic methicillin-resistant Staphylococcus aureus (EMRSA) found in the United Kingdom. It was originally characterized by weak lysis with phage 75 and production of enterotoxin C but not urease. Two variant strains of EMRSA-15 which show a broader phage pattern than the progenitor strain have emerged. A total of 153 recent clinical isolates representing classical EMRSA-15 (55 isolates) or these phage variants (98 isolates) were compared by SmaI macrorestriction profiles in pulsed-field gel electrophoresis (PFGE) as well as by urease and enterotoxin C production. Eight of the 98 isolates were shown to be other unrelated strains by both PFGE and their production of urease, a misidentification rate of 8% by phage typing. Seventy-one EMRSA-15 isolates were enterotoxin C negative, and the majority of these were sensitive to phage 81. Examination of PFGE profiles and Southern blotting studies suggest that the enterotoxin C gene locus is encoded on a potentially mobile DNA segment of ca. 15 kb. After elimination of the eight non-EMRSA-15 isolates, the remaining 145 were characterized by PFGE, yielding 22 profiles. All profiles were within five band differences of at least one other profile. Classical EMRSA-15 isolates showed nine PFGE profiles, with the majority of isolates (68%) in profile B1. Six of these nine PFGE profiles were unique to the classical EMRSA-15 isolates. Among the phage variants of EMRSA-15, 16 profiles were seen, but the majority of isolates (83%) fell into 1 of 4 profiles (B2, B3, B4, and B7) which correlated well with phage patterns. The most divergent PFGE profiles among the EMRSA-15 isolates had as many as 12 band differences from one another, suggesting that in examining isolates belonging to such a temporally and geographically disseminated epidemic strain, the range of PFGE profiles must be regarded as a continuum and analyzed by relating the profiles back to the most common or progenitor profile.

[Methicillin resistant clinical strains of Staphylococcus aureus isolated from patients in the State Clinical Hospital Nr 2 in Szczecin]. / Oporne na metycyline szczepy Staphylococcus aureus izolowane od chorych w Panstwowym Szpitalu Klinicznym Nr 2 w Szczecinie.

Over a fivefold increase, from 11% to 58%, in the prevalence of methicillin-resistance was observed in 1994-95 amongst clinical isolates of Staphylococcus aureus in the State Clinical Hospital No 2 in Szczecin, one of the largest hospitals in the West Pomeranian region of Poland. The aim of this study was to see if any one particular strain was responsible for this apparent outbreak. Fifty-six randomly selected isolates were typed by SmaI macrorestriction analysis using PFGE and by analysis of antimicrobial susceptibility patterns. Results indicate the presence of two epidemic multi-drug resistant MRSA strains. Over 85% of typed MRSA belonged to the first strain, which was probably present in the hospital long before 1994. MRSA of this strain were isolated from patients in 8 hospital wards. The second strain was introduced into two wards of the hospital in the last year of the study.