How Explainable Artificial Intelligence Can Increase or Decrease Clinicians' Trust in AI Applications in Health Care: Systematic Review.

BACKGROUND: Artificial intelligence (AI) has significant potential in clinical practice. However, its "black box" nature can lead clinicians to question its value. The challenge is to create sufficient trust for clinicians to feel comfortable using AI, but not so much that they defer to it even when it produces results that conflict with their clinical judgment in ways that lead to incorrect decisions. Explainable AI (XAI) aims to address this by providing explanations of how AI algorithms reach their conclusions. However, it remains unclear whether such explanations foster an appropriate degree of trust to ensure the optimal use of AI in clinical practice. OBJECTIVE: This study aims to systematically review and synthesize empirical evidence on the impact of XAI on clinicians' trust in AI-driven clinical decision-making. METHODS: A systematic review was conducted in accordance with PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, searching PubMed and Web of Science databases. Studies were included if they empirically measured the impact of XAI on clinicians' trust using cognition- or affect-based measures. Out of 778 articles screened, 10 met the inclusion criteria. We assessed the risk of bias using standard tools appropriate to the methodology of each paper. RESULTS: The risk of bias in all papers was moderate or moderate to high. All included studies operationalized trust primarily through cognitive-based definitions, with 2 also incorporating affect-based measures. Out of these, 5 studies reported that XAI increased clinicians' trust compared with standard AI, particularly when the explanations were clear, concise, and relevant to clinical practice. In addition, 3 studies found no significant effect of XAI on trust, and the presence of explanations does not automatically improve trust. Notably, 2 studies highlighted that XAI could either enhance or diminish trust, depending on the complexity and coherence of the provided explanations. The majority of studies suggest that XAI has the potential to enhance clinicians' trust in recommendations generated by AI. However, complex or contradictory explanations can undermine this trust. More critically, trust in AI is not inherently beneficial, as AI recommendations are not infallible. These findings underscore the nuanced role of explanation quality and suggest that trust can be modulated through the careful design of XAI systems. CONCLUSIONS: Excessive trust in incorrect advice generated by AI can adversely impact clinical accuracy, just as can happen when correct advice is distrusted. Future research should focus on refining both cognitive and affect-based measures of trust and on developing strategies to achieve an appropriate balance in terms of trust, preventing both blind trust and undue skepticism. Optimizing trust in AI systems is essential for their effective integration into clinical practice.

AI and XAI second opinion: the danger of false confirmation in human-AI collaboration.

Can AI substitute a human physician's second opinion? Recently the Journal of Medical Ethics published two contrasting views: Kempt and Nagel advocate for using artificial intelligence (AI) for a second opinion except when its conclusions significantly diverge from the initial physician's while Jongsma and Sand argue for a second human opinion irrespective of AI's concurrence or dissent. The crux of this debate hinges on the prevalence and impact of 'false confirmation'-a scenario where AI erroneously validates an incorrect human decision. These errors seem exceedingly difficult to detect, reminiscent of heuristics akin to confirmation bias. However, this debate has yet to engage with the emergence of explainable AI (XAI), which elaborates on why the AI tool reaches its diagnosis. To progress this debate, we outline a framework for conceptualising decision-making errors in physician-AI collaborations. We then review emerging evidence on the magnitude of false confirmation errors. Our simulations show that they are likely to be pervasive in clinical practice, decreasing diagnostic accuracy to between 5% and 30%. We conclude with a pragmatic approach to employing AI as a second opinion, emphasising the need for physicians to make clinical decisions before consulting AI; employing nudges to increase awareness of false confirmations and critically engaging with XAI explanations. This approach underscores the necessity for a cautious, evidence-based methodology when integrating AI into clinical decision-making.

Otitis media: Interactions between host and environment, immune and inflammatory responses.

OBJECTIVE: To review and highlight progress in otitis media (OM) research in the areas of immunology, inflammation, environmental influences and host-pathogen responses from 2019 to 2023. Opportunities for innovative future research were also identified. DATA SOURCES: PubMed database of the National Library of Medicine. REVIEW METHODS: Key topics were assigned to each panel member for detailed review. Search of the literature was from June 2019 until February 2023. Draft reviews were collated, circulated, and discussed among panel members at the 22nd International Symposium on Recent Advances in Otitis Media in June 2023. The final manuscript was prepared and approved by all the panel members. CONCLUSIONS: Important advances were identified in: environmental influences that enhance OM susceptibility; polymicrobial middle ear (ME) infections; the role of adaptive immunity defects in otitis-proneness; additional genes linked to OM; leukocyte contributions to OM pathogenesis and recovery; and novel interventions in OM based on host responses to infection. Innovative areas of research included: identification of novel bacterial genes and pathways important for OM persistence, bacterial adaptations and evolution that enhance chronicity; animal and human ME gene expression, including at the single-cell level; and Sars-CoV-2 infection of the ME and Eustachian tube.

Source Control of Gram-Negative Bacteria Using Self-Disinfecting Sinks in a Swedish Burn Centre.

Several retrospective studies have identified hospital sinks as reservoirs of Gram-negative bacteria. The aim of this study was to prospectively investigate the bacterial transmission from sinks to patients and if self-disinfecting sinks could reduce this risk. Samples were collected weekly from sinks (self-disinfecting, treated with boiling water, not treated) and patients in the Burn Centre at Linköping University Hospital, Sweden. The antibiotic susceptibility of Gram-negative isolates was tested, and eight randomly chosen patient isolates and their connected sink isolates were subjected to whole genome sequencing (WGS). Of 489 sink samples, 232 (47%) showed growth. The most frequent findings were Stenotrophomonas maltophilia (n = 130), Pseudomonas aeruginosa (n = 128), and Acinetobacter spp. (n = 55). Bacterial growth was observed in 20% of the samplings from the self-disinfecting sinks and in 57% from the sinks treated with boiling water (p = 0.0029). WGS recognized one transmission of Escherichia coli sampled from an untreated sink to a patient admitted to the same room. In conclusion, the results showed that sinks can serve as reservoirs of Gram-negative bacteria and that self-disinfecting sinks can reduce the transmission risk. Installing self-disinfecting sinks in intensive care units is an important measure in preventing nosocomial infection among critically ill patients.

The First Swedish Outbreak with VIM-2-Producing Pseudomonas aeruginosa, Occurring between 2006 and 2007, Was Probably Due to Contaminated Hospital Sinks.

Multidrug-resistant Pseudomonas aeruginosa is an increasing clinical problem worldwide. The aim of this study was to describe the first outbreak of a Verona integron-borne metallo-ß-lactamase (VIM)-2-producing P. aeruginosa strain in Sweden and its expansion in the region. A cluster of multidrug-resistant P. aeruginosa appeared at two neighbouring hospitals in 2006. The isolates were characterized by PCR, pulsed-field gel electrophoresis (PFGE), and whole-genome sequencing. Patient charts, laboratory records, and hygiene routines were reviewed, and patients, staff, and the environment were screened. The investigation revealed a clonal outbreak of a VIM-2-producing P. aeruginosa strain belonging to the high-risk clonal complex 111, susceptible only to gentamicin and colistin. No direct contact between patients could be established, but most of them had stayed in certain rooms/wards weeks to months apart. Cultures from two sinks yielded growth of the same strain. The outbreak ended when control measures against the sinks were taken, but new cases occurred in a tertiary care hospital in the region. In conclusion, when facing prolonged outbreaks with this bacterium, sinks and other water sources in the hospital environment should be considered. By implementing proactive control measures to limit the bacterial load in sinks, the waterborne transmission of P. aeruginosa may be reduced.

Correction to: Bacteria: back pain, leg pain and Modic sign-a surgical multicenter comparative study.

Unfortunately, the 5th author name was incorrectly published in the original paper. The complete correct name is given below.

Cluster of S. maltophilia among patients with respiratory tract infections at an intensive care unit.

BACKGROUND: Stenotrophomonas maltophilia is associated with respiratory tract infections in immunocompromised patients, and it has emerged as an important nosocomial pathogen, with admission to intensive care units (ICUs) and ventilators as recognized risk factors. AIM: To describe the investigation of a sudden increase in patients with pneumonia caused by S. maltophilia at a Swedish ICU and the control measures taken. METHODS: Lower respiratory tract cultures from patients admitted to the ICU were obtained, and environmental cultures were collected from sink drains and medical equipment. Isolates identified as S. maltophilia were subjected to antibiotic susceptibility testing and whole genome sequencing (WGS). FINDINGS: A total of 17 S. maltophilia isolates were found (four from patients and 13 from the environment). The WGS identified two outbreak clones, sequence type (ST) 361 and ST138, and seven unique ones. Most likely, the outbreak clones originated from two sinks, and transmission was enhanced by a calorimeter. After changing the sink and calorimeter routines, no more cases were registered. CONCLUSION: Acquisition of S. maltophilia from the hospital environment appears to be easy, especially if water is involved. To control this bacterium, better knowledge of its transmission routes in hospital environments is required.

Bacteria: back pain, leg pain and Modic sign-a surgical multicentre comparative study.

PURPOSE: To compare bacterial findings in pain-generating degenerated discs in adults operated on for lumbar disc herniation (LDH), and mostly also suffering from low back pain (LBP), with findings in adolescent patients with non-degenerated non-pain-generating discs operated on for scoliosis, and to evaluate associations with Modic signs on magnetic resonance imaging (MRI). Cutibacterium acnes (Propionibacterium acnes) has been found in painful degenerated discs, why it has been suggested treating patients with LDH/LBP with antibiotics. As multidrug-resistant bacteria are a worldwide concern, new indications for using antibiotics should be based on solid scientific evidence. METHODS: Between 2015 and 2017, 40 adults with LDH/LBP (median age 43, IQR 33-49) and 20 control patients with scoliosis (median age 17, IQR 15-20) underwent surgery at seven Swedish hospitals. Samples were cultured from skin, surgical wound, discs and vertebrae. Genetic relatedness of C. acnes isolates was investigated using single-nucleotide polymorphism analysis. DNA samples collected from discs/vertebrae were analysed using 16S rRNA-based PCR sequencing. MRI findings were assessed for Modic changes. RESULTS: No bacterial growth was found in 6/40 (15%) LDH patients, compared with 3/20 (15%) scoliosis patients. Most positive samples in both groups were isolated from the skin and then from subcutis or deep within the wound. Of the four disc and vertebral samples from each of the 60 patients, 235/240 (98%) were DNA negative by bacterial PCR. A single species, C. acnes, was found exclusively in the disc/vertebra from one patient in each group. In the LDH group, 29/40 (72%) patients had at least one sample with growth of C. acnes, compared to 14/20 (70%) in the scoliosis group. Bacterial findings and Modic changes were not associated. CONCLUSIONS: Cutibacterium acnes found in discs and vertebrae during surgery for disc herniation in adults with degenerated discs may be caused by contamination, as findings in this group were similar to findings in a control group of young patients with scoliosis and non-degenerated discs. Furthermore, such findings were almost always combined with bacterial findings on the skin and/or in the wound. There was no association between preoperative Modic changes and bacterial findings. Antibiotic treatment of lumbar disc herniation with sciatica and/or low back pain, without signs of clinical discitis/spondylitis, should be seriously questioned. These slides can be retrieved under Electronic Supplementary Material.

Outbreak of Methicillin-resistant Staphylococcus aureus in a Hospital Center for Children's and Women's Health in a Swedish County.

The objective of this study was to investigate a sudden increase in methicillin-resistant Staphylococcus aureus (MRSA) cases primarily in one maternity ward at the Center for Children's and Women's Health at Linköping University Hospital, Sweden. Approximately 300 individuals including patients, their family members, and healthcare workers were screened for MRSA. The antibiotic susceptibility was tested and isolates polymerase chain reaction (PCR)-positive for the mecA gene were spa typed. Isolates with the same antibiogram and spa type were further whole genome sequenced. Compliance to current cleaning and hygiene routines was also controlled, and environmental samples collected. The results showed that a total of 13 individuals were involved in the outbreak. It was caused by a t386 MRSA strain (ST-1, NCBI-accession AB505628) with additional resistance to erythromycin and clindamycin. All cases were epidemiologically connected to the index patient, who had recently emigrated from a high-endemic area for MRSA. With improved cleaning and better compliance to basic hygiene routines, no further cases were reported. This study demonstrates how rapid an MRSA strain can disseminate in a ward with susceptible patients and insufficient cleaning and hygiene. For a better control of MRSA, clinical cultures and screening samples need to be obtained early and more extensively than according to the current recommendations.

Rapid Increase in Carriage Rates of Enterobacteriaceae Producing Extended-Spectrum ß-Lactamases in Healthy Preschool Children, Sweden.

By collecting and analyzing diapers, we identified a >6-fold increase in carriage of extended-spectrum ß-lactamase (ESBL)-producing Enterobacteriaceae for healthy preschool children in Sweden (p<0.0001). For 6 of the 50 participating preschools, the carriage rate was >40%. We analyzed samples from 334 children and found 56 containing >1 ESBL producer. The prevalence in the study population increased from 2.6% in 2010 to 16.8% in 2016 (p<0.0001), and for 6 of the 50 participating preschools, the carriage rate was >40%. Furthermore, 58% of the ESBL producers were multidrug resistant, and transmission of ESBL-producing and non-ESBL-producing strains was observed at several of the preschools. Toddlers appear to be major carriers of ESBL producers in Sweden.

Protective ventilation reduces Pseudomonas aeruginosa growth in lung tissue in a porcine pneumonia model.

BACKGROUND: Mechanical ventilation with positive end expiratory pressure and low tidal volume, i.e. protective ventilation, is recommended in patients with acute respiratory distress syndrome. However, the effect of protective ventilation on bacterial growth during early pneumonia in non-injured lungs is not extensively studied. The main objectives were to compare two different ventilator settings on Pseudomonas aeruginosa growth in lung tissue and the development of lung injury. METHODS: A porcine model of severe pneumonia was used. The protective group (n = 10) had an end expiratory pressure of 10 cm H2O and a tidal volume of 6 ml x kg-1. The control group (n = 10) had an end expiratory pressure of 5 cm H2O and a tidal volume of 10 ml x kg-1. 1011 colony forming units of Pseudomonas aeruginosa were inoculated intra-tracheally at baseline, after which the experiment continued for 6 h. Two animals from each group received only saline, and served as sham animals. Lung tissue samples from each animal were used for bacterial cultures and wet-to-dry weight ratio measurements. RESULTS: The protective group displayed lower numbers of Pseudomonas aeruginosa (p < 0.05) in the lung tissue, and a lower wet-to-dry ratio (p < 0.01) than the control group. The control group deteriorated in arterial oxygen tension/inspired oxygen fraction, whereas the protective group was unchanged (p < 0.01). CONCLUSIONS: In early phase pneumonia, protective ventilation with lower tidal volume and higher end expiratory pressure has the potential to reduce the pulmonary bacterial burden and the development of lung injury.

Inadequate adherence to Swedish guidelines for uncomplicated lower urinary tract infections among adults in general practice.

In a primary care study of urinary tract infections (UTIs) performed 2008 in Uppsala County, Sweden, 43% of the patients were culture negative. In order to investigate the background to the observed overdiagnosis of UTI, study invitations were sent to the previously included patients. A total of 256 patients (88% women) approved to participate. Patient charts and recorded laboratory data were reviewed. Two or more of the cardinal symptoms were reported in 53% of the women and in 19% of the men. A dipstick test was performed in 93% of the consultations. The highest positive predicted values in women had a positive nitrite test (95%, 95% CI 87; 99) and dysuria in combination with urgency (81%, 95% CI 72; 88). Seventy-one percent of the women who fulfilled the symptom criteria received an antibiotic prescription directly, 87% of these had a positive culture. The drug of choice was pivmecillinam for women (51%) and quinolones (50%) for men. The treatment duration was too long for the women; 68% were treated for ≥7 days. In conclusion, the adherence to national guidelines/recommendations was inadequate. To reduce the selection of multiresistant bacteria, an improvement of the use of diagnostic criteria/tools and antibiotic drugs in primary care is necessary.

Individual-level effects of antibiotics on colonizing otitis pathogens in the nasopharynx.

BACKGROUND: Although there is evidence of an association between antibiotic consumption and resistant bacteria on a population level, the relationship on an individual level has been less well studied, particularly in terms of nasopharyngeal colonization. We have therefore analysed this association, using data from a closely followed cohort of children taking part in a vaccination trial. METHODS: 109 children with early onset of acute otitis media (AOM) were randomised to heptavalent pneumococcal conjugate vaccine (PCV7) or no vaccination. They were followed for three years with scheduled appointments as well as sick visits. Nasopharyngeal cultures were obtained at all visits. Antibiotic treatments were recorded, as were risk factors for AOM, including siblings, short breast-feeding and parental smoking. Data were entered into a Cox regression model, and the findings of Streptococcus pneumoniae and Haemophilus influenzae with reduced susceptibility to the penicillin group were related to the number of previous courses of antibiotics. RESULTS: There was evidence of an association between the amount of previously consumed betalactams and colonization with beta-lactamasenegative ampicillin-resistant (BLNAR) H. influenzae (RR 1.21; 95% CI 1.03-1.43; p = 0.03), and also with the most commonly prescribed drug; amoxicillin (RR 1.39; 95% CI 1.09-1.76; p = 0.01). There was no evidence for an association between antibiotic consumption and betalactamase producing H. influenzae or S. pneumoniae with reduced susceptibility to penicillin. Furthermore, there was no evidence of an association between resistant bacteria and AOM risk factors or PCV7. CONCLUSION: In this subgroup of children, most of whom were given several courses of antibiotics in early childhood, there was evidence of an association between betalactam/amoxicillin consumption and nasopharyngeal colonization with BLNAR strains, bacteria that have increased in prevalence during the last 10-15 years, and that are notoriously difficult to treat with oral antibiotics.

A trial with IgY chicken antibodies to eradicate faecal carriage of Klebsiella pneumoniae and Escherichia coli producing extended-spectrum beta-lactamases.

BACKGROUND: Extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae is an emerging therapeutic challenge, especially in the treatment of urinary tract infections. Following an outbreak of CTX-M-15 Klebsiella pneumoniae in Uppsala, Sweden, an orphan drug trial on IgY chicken antibodies was undertaken in an attempt to eradicate faecal carriage of ESBL-producing K. pneumoniae and Escherichia coli. METHODS: Hens were immunised with epitopes from freeze-dried, whole-cell bacteria (ESBL-producing K. pneumoniae and E. coli) and recombinant proteins of two K. pneumoniae fimbriae subunits (fimH and mrkD). The egg yolks were processed according to good manufacturing practice and the product was stored at-20°C until used. Using an internal database from the outbreak and the regular laboratory database, faecal carriers were identified and recruited from May 2005 to December 2013. The participants were randomised in a placebo-controlled 1:1 manner. RESULTS: From 749 eligible patients, 327 (44%) had deceased, and only 91 (12%) were recruited and signed the informed consent. In the initial screening performed using the polymerase chain reaction, 24 participants were ESBL positive and subsequently randomised and treated with either the study drug or a placebo. The study was powered for 124 participants. Because of a very high dropout rate, the study was prematurely terminated. From the outbreak cohort (n=247), only eight patients were screened, and only one was positive with the outbreak strain in faeces. CONCLUSIONS: The present study design, using IgY chicken antibodies for the eradication of ESBL-producing K. pneumonia and E. coli, was ineffective in reaching its goal due to high mortality and other factors resulting in a low inclusion rate. Spontaneous eradication of ESBL-producing bacteria was frequently observed in recruited participants, which is consistent with previous reports.

Effect of pneumococcal conjugate vaccination on nasopharyngeal carriage in children with early onset of acute otitis media - a randomized controlled trial.

CONCLUSION: Although children vaccinated with heptavalent pneumococcal conjugate vaccine (PCV) had fewer episodes of acute otitis media (AOM), this trial was unable to prove a simultaneous decrease in nasopharyngeal carriage. OBJECTIVE: Carriage rates of AOM pathogens in the nasopharynx are high among children, and colonization is the first step towards infection. The possible impact of PCV on carriage is therefore of interest, particularly in children with recurrent AOM. The aims of this study were to examine the effect of heptavalent PCV on carriage of AOM pathogens in children at high risk of developing recurrent disease, and to monitor carriage of resistant pathogens in vaccinated and unvaccinated children. METHODS: A total of 109 children with an onset of AOM before 6 months of age, 89 of whom developed recurrent disease, were enrolled in a trial. Fifty-two children were vaccinated and all were closely monitored for 3 years. RESULTS: There was no difference statistically between vaccinated children and controls concerning the carriage of any of the major AOM pathogens. There was evidence of within-child clustering for S. pneumoniae (p = 0.002) and H. influenzae (p < 0.001), indicating that children continued to carry either species over time. Resistance rates were generally low and comparable with national levels.

Level of decontamination after washing textiles at 60°C or 70°C followed by tumble drying.

BACKGROUND: Several major outbreaks in healthcare facilities have occurred with the emergence of multi-resistant bacteria. A possible route for dissemination is the hospital textiles and inadequate laundering of them. The aim of this study was to develop an easy-to-use method for simulating the laundering process of hospital textiles, and thereafter apply the method when evaluating the decontaminating efficacy of two different washing temperatures. METHODS: The laundering process, including tumble drying, took place at two professional laundries. Enterococcus faecium was used as bioindicator. RESULTS: The results showed that a lowering of the washing temperature from 70°C to 60°C did not affect the decontamination efficacy; the washing cycle alone reduced the number of bacteria with 3-5 log10 CFU, whereas the following tumble drying reduced the bacterial numbers with another 3-4 log10 CFU, yielding the same final result independent of washing temperature. Without tumble drying, there was an obvious risk of adding non-fermenting gram-negative bacteria to the fabric. These bacteria originated from the washing cycle. CONCLUSION: A simple method to simulate hospital laundering was developed. To save energy, it is possible to use a washing temperature of 60°C, but the washing cycle should be followed by tumble drying, and the whole laundering process needs to be monitored to maintain sufficient textile hygiene.

Immunologic findings in young children with early onset of acute otitis media.

CONCLUSION: No significant differences in the number of immune aberrations were seen between children with or without severe recurrent acute otitis media (rAOM); however, subnormal values of immunological markers were found more often than expected, and 4 of the 60 children had treatment-requiring immune deficiencies. OBJECTIVE: Minor immunologic aberrations have been reported to be more frequent in children with rAOM. Immune investigation is recommended in children with severe rAOM, defined as six or more AOM episodes per year. The purpose of this study was to describe immunological findings in young children at high risk of developing rAOM, and to relate these to the number of expected aberrations and to the presence of severe rAOM. METHODS: A total of 109 children at risk of developing rAOM were offered immune investigation including complement function, immunoglobulins with subclasses and cellular immunity. RESULTS: Sixty patients were tested, 31 of whom had severe rAOM and 12 of whom did not develop rAOM. Low levels of IgG2 (27%), C1q (31%) and mannan-binding lectin (21%) were found up to eight times as often as expected. Although subnormal values were more frequent among children with severe rAOM, the study was too small to provide reliable evidence of any difference. Four children were diagnosed with immune deficiencies that required treatment.

Silver resistance genes are overrepresented among Escherichia coli isolates with CTX-M production.

Members of the Enterobacteriaceae with extended-spectrum beta-lactamases (ESBLs) of the CTX-M type have disseminated rapidly in recent years and have become a threat to public health. In parallel with the CTX-M type expansion, the consumption and widespread use of silver-containing products has increased. To determine the carriage rates of silver resistance genes in different Escherichia coli populations, the presence of three silver resistance genes (silE, silP, and silS) and genes encoding CTX-M-, TEM-, and SHV-type enzymes were explored in E. coli isolates of human (n = 105) and avian (n = 111) origin. The antibiotic profiles were also determined. Isolates harboring CTX-M genes were further characterized, and phenotypic silver resistance was examined. The silE gene was present in 13 of the isolates. All of them were of human origin. Eleven of these isolates harbored ESBLs of the CTX-M type (P = 0.007), and eight of them were typed as CTX-M-15 and three as CTX-M-14. None of the silE-positive isolates was related to the O25b-ST131 clone, but 10 out of 13 belonged to the ST10 or ST58 complexes. Phenotypic silver resistance (silver nitrate MIC > 512 mg/liter) was observed after silver exposure in 12 of them, and a concomitant reduced susceptibility to piperacillin-tazobactam developed in three. In conclusion, 12% of the human E. coli isolates but none of the avian isolates harbored silver resistance genes. This indicates another route for or level of silver exposure for humans than that caused by common environmental contamination. Since silE-positive isolates were significantly more often found in CTX-M-positive isolates, it is possible that silver may exert a selective pressure on CTX-M-producing E. coli isolates.

Risk factors for carriage of AOM pathogens during the first 3 years of life in children with early onset of acute otitis media.

CONCLUSION: Risk factors associated with increased carriage rates are the same in children with recurrent acute otitis media (rAOM) as in healthy children. These are also known to be risk factors for the development of AOM itself. OBJECTIVES: The aim of this study was to describe risk factors for nasopharyngeal carriage in a cohort of young children at high risk of developing rAOM. METHODS: Children with an onset of AOM before 6 months of age, indicating an 80% risk of developing rAOM, were enrolled in a vaccination trial on heptavalent PCV. These children were monitored for 3 years during healthy and AOM periods with nasopharyngeal cultures, physical examinations, and questionnaires. RESULTS: A total of 109 children were included at a mean age of 5 months; 105 were followed for 3 years, 89 (82%) of whom developed rAOM. Risk factors associated with increased carriage of all major AOM pathogens were age <2 years, concurrent AOM, and fulfilment of rAOM criteria. Having siblings in day care was associated with increased carriage of Streptococcus pneumoniae and Haemophilus influenzae, recent antibiotic treatment was associated with H. influenzae and Moraxella catarrhalis carriage, and winter season was associated with M. catarrhalis carriage alone.