Molecular Characterization of Staphylococcus aureus Isolates From Children With Periorbital or Orbital Cellulitis.

BACKGROUND: Periorbital and orbital cellulitis cause significant pediatric morbidity. Here, we define the clinical features of and characterize isolates from children with periorbital or orbital cellulitis caused by Staphylococcus aureus at Texas Children's Hospital in Houston. METHODS: Patients were identified from a prospective S aureus study database from January 2002 to July 2015. Demographic and clinical data were collected retrospectively. Isolates were genotyped by pulsed-field gel electrophoresis, and Panton-Valentine leukocidin (lukSF-PV [pvl]) genes were detected by quantitative polymerase chain reaction. Data were analyzed with the Fisher exact or Wilcoxon rank-sum test. RESULTS: Eighty-five patients with periorbital (n = 58) or orbital (n = 27) cellulitis were identified. We found 57 (67%) methicillin-resistant S aureus (MRSA) isolates, 72 (85%) pvl-positive (pvl+) isolates, and 66 (78%) USA300 isolates. No differences in clinical characteristics were found when we compared MRSA to methicillin-susceptible (MSSA) infections or USA300 to non-USA300 infections. Patients with orbital cellulitis were hospitalized a median of 12 days (range, 2-28 days) and received antibiotics for 21 days (range, 10-32 days). Twelve (44%) patients with orbital cellulitis received steroids. Steroid treatment did not affect the length of hospitalization or duration of antibiotic treatment. Six (7%) patients with orbital cellulitis were bacteremic. Patients with periorbital cellulitis were hospitalized for a median of 3 days (range, 0-17 days) and received antibiotics for 11 days (range, 7-32 days). According to computed tomography (CT), 19 (70%) patients with orbital cellulitis and 11 (41%) with periorbital cellulitis had sinusitis. CONCLUSIONS: The majority of periorbital and orbital S aureus infections at Texas Children's Hospital were caused by MRSA, and no change was observed over time. Empirical antibiotic treatment should include coverage for MRSA. PVL might be an important virulence factor in these presentations. S aureus is associated with sinusitis and its complications.

Analysis of Invasive Community-Acquired Methicillin-Susceptible Staphylococcus aureus Infections During a Period of Declining Community Acquired Methicillin-Resistant Staphylococcus aureus Infections at a Large Children's Hospital.

BACKGROUND: The epidemiology of community acquired (CA) Staphylococcus aureus infections is changing in the United States. We investigated the current epidemiology of S. aureus infections at Texas Children's Hospital. METHODS: Patients with CA-S. aureus skin and soft tissue and invasive infections were retrospectively identified from January 1, 2007 to December 31, 2014. Invasive CA-MSSA isolates were characterized by pulsed field gel electrophoresis, Spa typing, agr type and presence of lukSF-PV (pvl) genes. Medical records were reviewed. Statistical analyses included Fisher exact, χ for trend and Wilcoxon tests. RESULTS: CA-MRSA infections decreased by 60.4% (1461-578 infections) from 2007 to 2014 (P < 0.0001), while CA-MSSA infections averaged 550 infections annually. Invasive CA-MRSA infections decreased by 67.2% from 61 to 20 infections (P < 0.0001); invasive CA-MSSA averaged 44 infections annually. Among 296 invasive CA-MSSA isolates, 74 (25%) isolates were USA300 and 88 (30%) were pvl+. USA300 declined among invasive CA-MSSA over time (P < 0.008). Musculoskeletal infections were most common (242/296, 82%); 52/242 (21.5%) isolates were USA300 and 62/242 (25.6%) pvl+. All 18 isolates from musculoskeletal infections with deep venous thrombosis and/or septic shock were pvl+ and 16/18 (88.9%) were USA300. Pneumonia isolates were mainly USA300 (8, 66.7%) and pvl+ (11, 91.7%). CONCLUSIONS: MSSA now cause the majority of invasive CA-S. aureus infections at our institution. Molecular analysis of invasive CA-MSSA isolates suggests strain diversity with USA300 on the decline and that disease presentations are to some extent strain specific. Changes in the CA-S. aureus epidemiology may, in part, be related to changes in immunity to the USA300 clone in the general population.

Invasive Pneumococcal Disease in Infants Aged 0-60 Days in the United States in the 13-Valent Pneumococcal Conjugate Vaccine Era.

We identified 53 infants aged 0-60 days with invasive pneumococcal disease (IPD) at 8 children's hospitals in the United States (2005-2015). After the introduction of 13-valent pneumococcal conjugate vaccine (PCV13), IPD caused by PCV13 serotypes decreased ~30% providing some evidence of indirect protection. However, approximately 60% of IPD was still caused by PCV13 serotypes.

Osteoarticular Infections Caused by Streptococcus pneumoniae in Children in the Post-Pneumococcal Conjugate Vaccine Era.

BACKGROUND: Pneumococcal osteoarticular infections (OAIs) are an uncommon manifestation of invasive pneumococcal disease (IPD). We describe the demographic characteristics, hospitalization rate, serotype distribution and antibiotic susceptibility of children with pneumococcal OAI over a 16-year period. METHODS: We identified patients ≤18 years old with pneumococcal OAI at 8 children's hospitals in the United States (2000-2015). Pneumococcal isolates were collected prospectively. Serotyping and antibiotic susceptibility were performed in a central laboratory. RESULTS: We identified 97 (3.3%) patients with pneumococcal OAI out of 2943 patients with IPD. Over 60% of the children were <2 years old. Septic arthritis (56.7%, 55/97) was the most common pneumococcal OAI, followed by osteomyelitis (25.8%, 25/97) and septic arthritis with concomitant osteomyelitis (17.5%, 17/97). Hospitalization for pneumococcal OAI overall decreased from 6.8 [95% confidence interval (CI): 5.2-8.6] to 4.4 (95% CI: 3.0-6.3) per 100,000 admissions from 2000-2009 to 2010-2015 (-35%, P = 0.05). Hospitalization for pneumococcal OAI caused by PCV13 serotypes decreased from 4.6 (95% CI: 3.4-6.2) to 0.9 (95% CI: 0.3-1.9) per 100,000 admissions from 2000-2009 to 2010-2015 (-87%, P < 0.0001). Overall, 12% of isolates had a penicillin minimal inhibitory concentration> 2 µg/mL, 3% a ceftriaxone minimal inhibitory concentration> 1 µg/mL and 15% were clindamycin resistant; these proportions remained unchanged after the introduction of PCV13. Serotypes 19A and 35B were responsible for penicillin and ceftriaxone nonsusceptible isolates in 2010-2015. CONCLUSIONS: Pneumococcal OAI represents 3% of all IPD, affecting mainly healthy infants and young children. Hospitalization for pneumococcal OAI caused by PCV13 serotypes dramatically decreased (-87%) after the introduction of PCV13.

Impact of Health Care Exposure on Genotypic Antiseptic Tolerance in Staphylococcus aureus Infections in a Pediatric Population.

Staphylococcus aureus possessing either the smr gene or the qacA/B genes is associated with decreased susceptibility to chlorhexidine gluconate (CHG) and other antiseptics. Previous studies of antiseptic-tolerant staphylococci have focused largely on high-risk populations, and the exact role of health care exposure in the acquisition of these organisms is unclear. We sought to describe the risk factors and features of infection caused by antiseptic-tolerant S. aureus in a general pediatric population. Isolates were selected from an ongoing S. aureus surveillance study. Every third sequential isolate in the year 2014 was selected for inclusion. All isolates underwent PCR for the genes qacA/B and smr Medical records were reviewed. Five hundred six isolates were included in the study, with 377 (74.3%) being community acquired. One hundred (19.8%) isolates were smr positive and 79 (15.6%) qacA/B positive. In univariable analyses, the presence of either gene was associated with underlying medical conditions, nosocomial acquisition, recent hospitalization, central venous lines, and CHG exposure. In multivariable analyses, only differences between patients with chronic medical conditions (odds ratio [OR] = 1.72; 95% confidence interval [CI], 1.22 to 2.64) and nosocomial acquisition (OR = 2.48; 95% CI, 1.16 to 8.17) remained statistically significant. Among patients without risk factors, 27.9% had infection with an antiseptic-tolerant isolate. smr- or qacA/B-positive S. aureus isolates are common in children and are independently associated with nosocomial acquisition and underlying medical conditions. These findings imply a role for the health care environment in acquisition of these organisms. However, genotypic antiseptic tolerance was seen in >25% of healthy children with an S. aureus infection, indicating that these organism are prevalent in the community as well.

Staphylococcus aureus Central Nervous System Infections in Children.

BACKGROUND: Central nervous system (CNS) infections caused by Staphylococcus aureus are uncommon in pediatric patients. We review the epidemiology, clinical features and treatment in 68 patients with a S. aureus CNS infection evaluated at Texas Children's Hospital. METHODS: Cases of CNS infection in children with positive cerebrospinal fluid cultures or spinal epidural abscess (SEA) for S. aureus at Texas Children's Hospital from 2001 to 2013 were reviewed. RESULTS: Seventy cases of S. aureus CNS infection occurred in 68 patients. Forty-nine cases (70%) were secondary to a CNS device, 5 (7.1%) were postoperative meningitis, 9 (12.8%) were hematogenous meningitis and 7 (10%) were SEAs. Forty-seven (67.2%) were caused by methicillin-sensitive S. aureus (MSSA) and 23 (32.8%) by methicillin-resistant S. aureus (MRSA). Community-acquired infections were more often caused by MRSA that was clone USA300/pvl. Most patients were treated with nafcillin (MSSA) or vancomycin (MRSA) with or without rifampin. Among patients with MRSA infection, 50% had a serum vancomycin trough obtained with the median level being 10.6 µg/mL (range: 5.4-15.7 µg/mL). Only 1 death was associated with S. aureus infection. CONCLUSIONS: The epidemiology of invasive of S. aureus infections continues to evolve with MSSA accounting for most of the infections in this series. The majority of cases were associated with neurosurgical procedures; however, hematogenous S. aureus meningitis and SEA occurred as community-acquired infections in patients without predisposing factors. Patients with MRSA CNS infections had a favorable response to vancomycin, but the beneficial effect of combination therapy or targeting vancomycin trough concentrations of 15-20 µg/mL remains unclear.

Pneumococcal Pneumonia Requiring Hospitalization in US Children in the 13-Valent Pneumococcal Conjugate Vaccine Era.

BACKGROUND.: The impact of PCV13 on a number of clinical aspects of pneumococcal pneumonia (PP) in children has not been reported. We compared the serotype distribution, antibiotic susceptibility, and outcomes of children with PP 4 years before and 4 years after the introduction of PCV13. METHODS.: We identified patients ≤18 years with PP at 8 children's hospitals in the United States (2006-2014). Pneumococcal isolates were collected prospectively. Serotyping and antibiotic susceptibility were performed in a central laboratory. Clinical and laboratory data were collected retrospectively. Annual pneumococcal pneumonia hospitalization rates per 100 000 admissions with 95% confidence intervals were calculated. Dichotomous variables were analyzed by χ2 test and continuous variables with Mann-Whitney U test. RESULTS.: A total of 377 patients with PP requiring hospitalization were identified. Hospitalization rates of PP decreased from 53.6 to 23.3 per 100000 admissions post PCV13 (P < .0001). Complicated PP rates also decreased (P < .0001). Need for intensive care, mechanical ventilation, and invasive procedure remained unchanged after the introduction of PCV13. Comorbidities were more common among children with uncomplicated than complicated pneumonia (52.2% vs. 22.5%, P < .001). Overall, PCV13 serotypes 19A, 3, 7F, and 1 caused 80% of PP. Hospitalization rates of PCV13 serotype pneumonia decreased from 47.2 to 15.7 per 100000 admissions post PCV13. In 2014, the most common serotypes were 3, 19A and 35B. CONCLUSIONS.: PP requiring hospitalization significantly decreased in children after PCV13 introduction. Complicated PP rates decreased steadily in 2011-2014. PCV13 serotypes 19A and 3 were still responsible for half of the cases of PP in 2011-2014.

Emergence of Multidrug-Resistant Pneumococcal Serotype 35B among Children in the United States.

Streptococcus pneumoniae serotype 35B is a nonvaccine serotype associated with high rates of penicillin nonsusceptibility. An increase in the proportion of multidrug-resistant (MDR) 35B isolates has recently been reported. The genetic events contributing to the emergence of MDR serotype 35B are unknown. The sequence type (ST) composition of 78 serotype 35B isolates obtained from pediatric patients with invasive pneumococcal disease from 1994 to 2014 and 48 isolates from pediatric patients with otitis media (noninvasive) from 2011 to 2014 was characterized by multilocus sequence typing (MLST). The most common STs were ST558 (69.2%), ST156 (10.3%), and ST452 (3.8%). Two major clonal complexes (CC), CC558 and CC156, were identified by eBURST analysis. Overall, 91% (71/78) of isolates were penicillin nonsusceptible and 16.7% (13/78) were MDR. Among all invasive serotype 35B isolates, MDR isolates increased significantly, from 2.9% (1/35) to 27.9% (12/43) (P = 0.004), after the 13-valent pneumococcal conjugate vaccine (PCV13) was introduced. All CC156 isolates were identified after the introduction of PCV13 (0/35 [0%] before versus 9/43 [20.9%] after; P = 0.003) and were MDR. All CC156 isolates had similar antimicrobial susceptibility patterns; in contrast, high variability in antimicrobial susceptibility was observed among CC558 isolates. The distributions of CC558 and CC156 among invasive and noninvasive isolates were not different. The increased prevalence of MDR serotype 35B after the introduction of PCV13 was directly associated with the emergence of ST156. Genotyping suggests that capsular switching has occurred between MDR vaccine serotypes belonging to ST156 (e.g., 9V, 14, and 19A) and serotype 35B.

The Contemporary Microbiology and Rates of Concomitant Osteomyelitis in Acute Septic Arthritis.

BACKGROUND: Septic arthritis (SA) and acute osteomyelitis (AO) are among the most common serious bacterial infections of childhood. Knowledge of the microbiology of SA is critical to treatment. Awareness of the presence of attendant AO is also important to guide clinical management. We sought to describe the current microbiology of SA in children and clinical features associated with coexisting AO. MATERIALS AND METHODS: Patients with SA were identified from the infectious diseases consult service records from 2010 to 2014. Patients with penetrating/open trauma and orthopedic hardware in situ were excluded. RESULTS: A total of 168 patients with SA were included. The most common causative organism was Staphylococcus aureus accounting for 47.7% of cases (29.1% were methicillin-susceptible S. aureus and 18.5% were methicillin-resistant S. aureus), followed by group A streptococcus (GAS, 8.9%). The proportion of cases due to GAS increased from 2011 to 2014 (3.3%-16.7%; P = 0.1). One hundred eight (64.3%) patients had concurrent AO. The presence of osteomyelitis was associated with older median age (5.9 vs. 2.4 years; P = 0.04), a longer duration of symptoms (5 vs. 2.5 days; P < 0.001), S. aureus (62.1% vs. 21.7%; P < 0.001), bacteremia (46.2% vs. 20.3%; P = 0.001), a longer duration of fever after admission (5 vs. 2 days; P < 0.001) and a longer length of stay (10 vs. 6 days; P < 0.001). CONCLUSIONS: Methicillin-resistant S. aureus continues to be an important cause of SA though GAS may be increasing in frequency. The presence of concomitant osteomyelitis is higher than previously reported and associated with older age, a longer duration of symptoms and fever, bacteremia and S. aureus.

Invasive pneumococcal infections in children following transplantation in the pneumococcal conjugate vaccine era.

BACKGROUND: Pediatric recipients of hematopoietic stem cell and solid organ transplants are at increased risk of invasive pneumococcal infections (IPI). Data on IPI in this population are scarce. To our knowledge, this is the first study describing the epidemiology of IPI among pediatric transplant recipients in the pneumococcal conjugate vaccine (PCV) era. METHODS: We identified transplant recipients with IPI at 8 children's hospitals in the U.S. from our surveillance database (2000-2014). Pneumococcal isolates were collected prospectively. Serotyping and antibiotic susceptibility were performed in a central laboratory. Categorical variables were analyzed by Fisher's exact test and continuous variables with nonparametric tests. Indirect cohort study design was used to calculate vaccine effectiveness. RESULTS: We identified 65 episodes of IPI in transplant recipients. Recurrent IPI was observed in 10% of transplant recipients. The IPI crude incidence rate in solid organ transplant recipients was higher than in the general population. Most IPI episodes occurred >6 months after transplantation. Bacteremia and pneumonia were the most common presentations. Meningitis was unusual. No case fatalities were observed. Serotype 19A was the most common serotype (n=10), followed by 6C (n=7). In 2010-2014, 37% of IPI was caused by PCV13 serotypes. Four cases of vaccine breakthrough were identified. Most isolates were susceptible to penicillin and ceftriaxone. Pneumococcal conjugate and polysaccharide immunization rates were low. CONCLUSION: Pediatric transplant recipients remain at increased risk of IPI in the vaccine era. Most cases presented as a late post-transplant infection. The interval between transplantation and IPI may allow adequate time for pneumococcal immunization.

Clinical and Epidemiological Evidence of the Red Queen Hypothesis in Pneumococcal Serotype Dynamics.

BACKGROUND: The Red Queen hypothesis is an evolutionary theory that describes the reciprocal coevolution of competing species. We sought to study whether introduction of the 7- and 13-valent pneumococcal conjugate vaccines (PCV7 and PCV13, respectively) altered pneumococcal serotype dynamics among children with invasive pneumococcal disease (IPD) as predicted by the Red Queen hypothesis. METHODS: This study examined pneumococcal isolates (n = 641) obtained from children <18 years of age hospitalized with IPD from 1997 to 2014 in Utah. A review of the literature also identified several additional studies conducted in the United States and Europe that were used to test the external generalizability of our Utah findings. Simpson's index was used to quantify pneumococcal serotype diversity. RESULTS: In Utah, the introduction of PCV7 and PCV13 was associated with rapid increases in serotype diversity (P < .001). Serotypes rarely present before vaccine introduction emerged as common causes of IPD. Diversity then decreased (P < .001) as competition selected for the fittest serotypes and new evolutionary equilibriums were established. This pattern was also observed more broadly in the United States, the United Kingdom, Norway, and Spain. CONCLUSIONS: This vaccine-driven example of human/bacterial coevolution appears to confirm the Red Queen hypothesis, which reveals a limitation of serotype-specific vaccines and offers insights that may facilitate alternative strategies for the elimination of IPD.

Role of Operative or Interventional Radiology-Guided Cultures for Osteomyelitis.

BACKGROUND AND OBJECTIVE: Acute hematogenous osteomyelitis (AHO) is a severe infection in children. Drainage of purulent collections in bones provides specimens for culture as well as therapeutic benefit. Interventional radiology (IR)-guided procedures may serve as a less invasive means of culture in select patients. We examined the impact of IR and surgically obtained cultures in the diagnosis and management of AHO. METHODS: A retrospective review of cases of AHO was performed from 2011 to 2014. Patients with chronic disease, orthopedic hardware, puncture wounds, or an infected contiguous focus were excluded. RESULTS: A total of 250 cases met inclusion criteria. Blood cultures were positive in 107 of 231 cases (46.3%), and 123 of 150 patients had positive cultures (82%) obtained by orthopedic surgery. Of these 123 patients, 62 (50.4%) had organisms identified only through operating room (OR) cultures. Of the 66 patients who had cultures obtained by IR, 34 (51.5%) had positive IR cultures. For those with positive IR cultures, 18 (52.9%) had negative blood cultures. Among the 80 patients with negative blood culture and positive OR/IR culture, the results changed antibiotic therapy in 68 (85%) patients. CONCLUSIONS: IR or OR culture was the only means of identifying a pathogen in 80 of 216 cases (37%), and in >80% changed medical management. IR can be used effectively to obtain bone cultures in children with AHO not requiring open surgical drainage. Further research is needed to better understand the optimal utilization of IR and OR culture in pediatric AHO.

Healthcare-associated Staphylococcus aureus Bacteremia in Children: Evidence for Reverse Vancomycin Creep and Impact of Vancomycin Trough Values on Outcome.

INTRODUCTION: Elevated vancomycin minimum inhibitory concentrations (MICs) in Staphylococcus aureus have been associated with worse clinical outcomes in adults. For invasive meticillin-resistant S. aureus (MRSA) infections in adults, the Infectious Diseases Society of America recommends targeting vancomycin serum trough concentrations between 15 and 20 µg/mL. We evaluated trends in vancomycin MICs from healthcare-associated (HCA) S. aureus bacteremia isolates in children in addition to correlating vancomycin serum trough levels with clinical outcomes. METHODS: Patients and isolates were identified from a prospective S. aureus surveillance study at Texas Children's Hospital (TCH). HCA S. aureus bacteremia isolates from 2003 to 2013 were selected. Vancomycin MICs by E-test were determined and medical records were reviewed. Acute kidney injury (AKI) was defined as doubling of the baseline serum creatinine. RESULTS: Three hundred forty-one isolates met inclusion criteria. We observed a reverse vancomycin creep among MRSA isolates in the study period with a decline in the proportion of isolates with vancomycin MIC ≥ 2 µg/mL (from 32.7% to 5.6%; P < 0.001). However, the proportion of MSSA isolates with MIC ≥ 2 µg/mL increased (from 2.9% to 9%; P = 0.04). Among patients who had vancomycin troughs performed, there was no difference in duration of bacteremia or fever with vancomycin trough >15 versus <15 µg/mL. A vancomycin trough >15 µg/mL was, however, an independent risk factor for AKI. CONCLUSIONS: Vancomycin MICs are shifting among HCA S. aureus bacteremia isolates with significant differences between MRSA and MSSA at TCH. Higher vancomycin troughs did not improve outcomes in pediatric HCA S. aureus bacteremia but were associated with increased nephrotoxicity. Further studies are needed to better understand optimal management of children with S. aureus bacteremia.

Clinical and Molecular Features of Decreased Chlorhexidine Susceptibility among Nosocomial Staphylococcus aureus Isolates at Texas Children's Hospital.

One of the strategies utilized to decrease infections in the hospital setting relies on topical antimicrobials and antiseptics. While their use is beneficial, concerns arise over the potential to develop resistance or tolerance to these agents. We examined nosocomial Staphylococcus aureus isolates from 2007 to 2013 for the presence of genes associated with tolerance to chlorhexidine. Isolates and patients were identified from an S. aureus surveillance study at Texas Children's Hospital. Nosocomial S. aureus isolates (those causing infection at ≥72 h of hospitalization) were identified and underwent PCR for the qacA or qacB (qacA/B) and smr genes associated with elevated minimum bactericidal concentrations of chlorhexidine. Molecular typing with pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), and agr typing and a review of the medical record were performed. Two hundred forty-seven nosocomial S. aureus infections were identified. Overall, 111 isolates carried one or both genes (44.9%); 33.1% were positive for smr, 22.7% were positive for qacA/B, and 10.9% of the isolates possessed both genes. The smr-positive isolates were more often resistant to methicillin, ciprofloxacin, and/or clindamycin. The isolates positive for qacA/B were more often associated with indwelling central venous catheters and a vancomycin MIC of ≥2 µg/ml. Isolates carrying either smr or qacA/B were associated with a diagnosis of bacteremia. The smr-positive isolates more often belonged to sequence type 8 (ST8) than the isolates that were positive for qacA/B. Mupirocin resistance was detected in 2.8% of the isolates. Antiseptic-tolerant S. aureus strains are common in our children's hospital and are associated with decreased susceptibility to other systemic antimicrobials and with bloodstream infections. Further work is needed to understand the implications that these organisms have on the hospital environment and antiseptic use in the future.

Early Streptococcus pneumoniae serotype changes in Utah adults after the introduction of PCV13 in children.

INTRODUCTION: Pneumococcal conjugate vaccines (PCV) have indirect effects due to decreased Streptococcus pneumoniae colonization in vaccine recipients. We sought to determine whether the introduction of PCV13 in children led to changes in the epidemiology and clinical manifestations of invasive pneumococcal disease (IPD) in adults. METHODS: We described demographics, comorbidities, clinical manifestations, and serotypes of IPD in Utah adults before (November 2009-February 2010) and after (March 2010-March 2012) the introduction of PCV13 in children. We also compare serotypes causing IPD in Utah adults and children. RESULTS: After the introduction of PCV13 in the childhood vaccine program, the proportion of IPD due to PCV13 exclusive serotypes decreased significantly in Utah adults (64-40%, p=0.009), primarily due to a decline in serotype 7F (36-15%, p=0.008). There were non-significant increases in IPD due to Pneumococcal polysaccharide 23 (PPV23) unique serotypes and non-vaccine serotypes, most notably serotype 22F. Changes in the proportions of vaccine and non-vaccine serotypes were similar in adults and children. Meningitis was more commonly due to non-vaccine serotypes relative to non-meningitis cases (47% vs. 18%, p=0.007). When stratified by sex, decreases in PCV13 serotype IPD were only noted in men (76-33%, p=0.001). CONCLUSIONS: Serotype epidemiology of IPD in adults closely follows that of children in the PCV13 era. Continued surveillance is needed to confirm whether replacement serotypes will lead to increases in pneumococcal meningitis and whether there are sex differences in the indirect effects of PCV vaccination in children.

Characterization of Staphylococcus aureus infections in children with Down syndrome.

Staphylococcus aureus infections in the Down syndrome (DS) population have not been well characterized. This study determined clinical and molecular characteristics of S. aureus infections in children with DS followed at Texas Children's Hospital (TCH), from 2001 to 2011. Patients were retrospectively identified from an ongoing S. aureus surveillance study. Medical records were reviewed. Isolates were characterized by antimicrobial susceptibility, pulsed-field gel electrophoresis patterns, and detection of PVL genes (pvl), mupA (high-level mupirocin resistance gene), smr (chlorhexidine resistance conferring gene), and Staphylococcal Chromosomal Cassette mec (SCCmec) type. Twenty-six patients with DS had a total of 34 S. aureus infections (8 recurrent); 61% were MRSA. DS patients represented 16.8 per 10,000 community onset S. aureus infections seen at TCH. Among 26 initial infections 17 were skin and soft tissue (SSTI), 7 were outer or middle ear and 2 were invasive infections. Seventeen patients were hospitalized. Thirteen (65%) of 20 available isolates were USA300, 14 were pvl+, 5 were mupA+, and 8 were smr+. Five of 8 (63%) recurrent infections were ear infections. All 4 recurrent ear isolates available for study were smr+, ciprofloxacin non-susceptible and treated with ciprofloxacin otic drops. S. aureus infections among patients with DS were similar in presentation to other patient groups, except for a greater proportion being associated with ear infections. Seventy percent of ear fluid isolates carried antiseptic and fluoroquinolone resistance genes. A study of a greater number of DS patients is warranted to further explore these findings.

Impact of the 13-Valent Pneumococcal Conjugate Vaccine on Pneumococcal Meningitis in US Children.

BACKGROUND: The impact of 13-valent pneumococcal conjugate vaccine (PCV13) on pneumococcal meningitis (PM) in US children is unknown. We compared the serotype distribution, antibiotic susceptibility, hospital course, and outcomes of children with PM 3 years before and 3 years after the introduction of PCV13. METHODS: We identified patients ≤ 18 years of age with PM at 8 children's hospitals in the United States. Pneumococcal isolates were collected prospectively. Serotyping and antibiotic susceptibility were performed in a central laboratory. Clinical data were abstracted from medical records. Patients were divided into 3 subgroups: pre-PCV13 (2007-2009), transitional year (2010), and post-PCV13 (2011-2013). Categorical variables were analyzed by the χ(2) test and continuous variables by the Mann--Whitney U test. RESULTS: During the study period, 173 of 1207 episodes (14%) of invasive pneumococcal disease were identified as PM; 76 of 645 (12%) were during 2007-2009 and 69 of 394 (18%) during 2011-2013 (50% increase; P = .03). The proportion of PCV13 serotype cases decreased from 54% in 2007-2009 to 27% in 2011-2013 (P = .001). Non-PCV13 serotype cases represented 73% of the isolates in 2011-2013. Isolates with ceftriaxone minimum inhibitory concentration ≥ 1 µg/mL decreased (13% to 3%) from 2007-2009 to 2011-2013 (P = .03). No significant differences were identified for hospital course or outcome, with the exception that a greater proportion of patients had subdural empyema and hemiparesis in 2011-2013. CONCLUSIONS: After the introduction of PCV13, the number of cases of PM in children remained unchanged compared with 2007-2009, although the proportion of PCV13 serotypes decreased significantly. Serotype 19A continued to be the most common serotype in 2011-2013. Antibiotic resistance decreased significantly. Morbidity and case-fatality rate due to PM remain substantial.

Staphylococcus aureus retropharyngeal abscess in children.

A retrospective review of 33 patients comparing community-associated methicillin-resistant Staphylococcus aureus retropharyngeal abscess (RPA) with community-associated methicillin-susceptible S. aureus RPA from 2002-2013 at Texas Children's Hospital revealed most cases of S. aureus RPA have been due to community-associated methicillin-resistant S. aureus, which appears to be associated with a more complicated clinical course than RPA caused by community-associated methicillin-susceptible S. aureus.

Multicenter surveillance of Streptococcus pneumoniae isolates from middle ear and mastoid cultures in the 13-valent pneumococcal conjugate vaccine era.

BACKGROUND: Streptococcus pneumoniae is a common cause of otitis media (OM) in children; mastoiditis remains an important complication of OM. Limited data are available on the impact of the 13-valent pneumococcal conjugate vaccine (PCV13) on pneumococcal otitis. METHODS: Investigators from 8 children's hospitals in the United States prospectively collected pneumococcal isolates from middle ear or mastoid cultures from children from 2011 to 2013. Serotype and antibiotic susceptibilities were determined and PCV13 doses for children documented. RESULTS: Over the 3-year period, the proportion of isolates included in PCV13 (plus a related serotype) decreased significantly (P = .0006) among the middle ear/mastoid isolates (2011, 50% [74/149]; 2012, 40.5% [47/116]; 2013, 29% [34/118]). The number of serotype 19A isolates in 2013 (n = 12, 10.2% of total) decreased 76% compared with the number of 19A isolates in 2011 (n = 50, 33.6% of total). Of the children from whom serotype 19A was isolated (n = 93), 55% had previously received <3 doses of PCV13. The most common non-PCV13 serotypes for the combined years were 35B (n = 37), 21 (n = 20), 23B (n = 20), 15B (n = 18), 11 (n = 17), 23A (n = 14), 15A (n = 14), and 15C (n = 14). The proportion of isolates with a penicillin minimal inhibitory concentration >2 µg/mL decreased significantly over the 3 years (2011, 22% [35/154]; 2012, 20% [24/118]; 2013, 10% [12/120]; P < .02). CONCLUSIONS: The number of pneumococcal isolates and the percentage of isolates with high-level penicillin resistance from cultures taken from children with OM or mastoiditis for clinical indications have decreased following PCV13 use, largely related to decreases in serotype 19A isolates.