Predictive value of methicillin-resistant staphylococcus aureus nasal swab in patients with COVID-19 pneumonia and secondary bacterial pneumonia.

OBJECTIVE: To determine the performance measures of admission methicillin-resistant Staphylococcus aureus (MRSA) nasal swabs for MRSA bacterial pneumonia in patients co-infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). METHODS: The study included patients admitted with SARS-CoV-2-positive nasopharyngeal specimens, MRSA nasal screens, and bacterial cultures to assess secondary MRSA pneumonia. RESULTS: 293 patients and 662 microbiological cultures evaluated. Overall, the specificity (91.8% [95% CI 88.6% to 95%]) and negative predictive value (NPV 97.4% [95% CI 95.4% - 99.3%]) of MRSA nasal swabs was high. However, the sensitivity (46.2%; 95% CI 19.1% to 73.3%) and positive predictive value (PPV 20.7%; 95% CI 59.5 - 35.4%) were low. Those patients in the MRSA nasal swab negative group had a shorter median duration of linezolid therapy. CONCLUSIONS: SARS-CoV-2 infection doesn't reduce the specificity or negative predictive value of MRSA nasal swabs for secondary MRSA pneumonia.

Ventilator-Associated Methicillin-Resistant Staphylococcus aureus (MRSA) Pneumonia in a Patient with a Negative MRSA Nasal Swab.

BACKGROUND Methicillin-resistant Staphylococcus aureus (MRSA) pneumonia is associated with high morbidity and mortality. Recently, MRSA testing by nasal swab has been utilized to "exclude" pneumonia caused by MRSA, given its high negative-predictive value (NPV). We present, however, a case of MRSA pneumonia diagnosed by endotracheal aspirate culture (EAC) in a patient with a negative MRSA nasal swab. CASE REPORT A 58-year-old woman presented with septic shock and respiratory failure. Chest X-ray (CXR) on admission was unrevealing; however, computed tomography (CT) revealed multifocal pneumonia. Intensive Care Unit (ICU)-level care was required for mechanical ventilation and vasopressors. She initially improved with treatment of community-acquired pneumonia (CAP) and was extubated on hospital day 6; however, she then developed a fever, tachycardia, and respiratory distress necessitating re-intubation later that day. Repeat CXR demonstrated a new left lower lobe infiltrate. Blood cultures were drawn and vancomycin and cefepime were started to cover for ventilator-associated pathogens. An EAC and nasal swab were collected to test for MRSA. The next day (day 7), the MRSA nasal swab returned negative, and vancomycin was discontinued. Our patient continued to experience fevers, worsening leukocytosis, and ongoing vasopressor need. On hospital day 9, the EAC results were obtained, and were positive for MRSA. Vancomycin was restarted and our patient recovered. CONCLUSIONS Negative MRSA nasal screening may be considered grounds to de-escalate empiric MRSA antibiotics if MRSA prevalence is low. However, in critically ill patients with high risk and suspicion for MRSA pneumonia, discontinuing empiric MRSA coverage should be done with caution or clinicians should wait until respiratory culture results are obtained before de-escalating antibiotics.

Case Report: Metagenomic next-generation sequencing assists in dynamic pathogen monitoring: powerful tool for progressing severe pneumonia.

Background: Severe community-acquired pneumonia (sCAP) is life-threatening and characterized by intensive care unit (ICU) admission and high mortality. And they are vulnerable to hospital-acquired infection. In such a severe condition, metagenomic next-generation sequencing (mNGS) outperforms for short turnaround time and broad detection spectrum. Case presentation: A 15-year-old male with severe influenza and methicillin-resistant Staphylococcus aureus (MRSA) pneumonia progressed rapidly, initially misdiagnosed as influenza co-infected with Aspergillus for misleading bronchoscopy manifestations. The turnaround time of mNGS is 13 h, which has the potential to expedite the clinical medication process. With the powerful support of mNGS and extracorporeal membrane oxygenation (ECMO), anti-infective therapy was adjusted accordingly, and vital signs gradually stabilized. After tortuous treatment and unremitting efforts, the patient recovered well. Conclusions: Rapid mNGS applications, timely medication adjustments, strong ECMO support and active family compliance contribute to this miracle of life. False-negative or false-positive results are alarming, anti-infective medications should be adjusted after a comprehensive review of physical status and other indicators.

Evaluating Methicillin-Resistant Staphylococcus aureus Polymerase Chain Reaction Nasal Screening as a Tool for Antimicrobial Stewardship.

INTRODUCTION: Initiation of broad-spectrum empiric antibiotics is common when infection is suspected in hospitalized adults. The benefits of early utilization of effective antibiotics are well documented. However, the negative effects of inappropriate antibiotic use have led to antimicrobial stewardship mandates. Recent data demonstrate the utility of methicillin-resistant Staphylococcus aureus (MRSA) polymerase chain reaction (PCR) nasal screening to steward anti-MRSA empiric antibiotics in pneumonia. We hypothesize that MRSA PCR nasal swabs would also be effective to rule out other MRSA infection to effectively limit unnecessary antibiotics for any infectious source. METHODS: We performed a single-center retrospective chart review of all adult patient encounters from October 2019-July 2021 with MRSA PCR nasal testing. We then reviewed all charts to evaluate for the presence of infections based on source cultures results, as the gold standard. Sensitivity, specificity, negative predictive value, and positive predictive value were calculated from 2 × 2 contingency tables. RESULTS: Among all patients with MRSA nasal screening, 1189 patients had any infection. Prevalence of MRSA nasal carriage among patients screened was 12%. Prevalence of MRSA infection among all infections was 7.5%. MRSA nasal swabs demonstrated a negative predictive value of 100% for MRSA urinary tract infection, 97.9% for MRSA bacteremia, 97.8% for MRSA pneumonia, 92.1% for MRSA wound infection, and 96.6% for other MRSA infections. Overall, MRSA PCR nasal swabs had a sensitivity of 68.5%, specificity of 90.1%, positive predictive value of 23.7%, and negative predictive value of 98.5% for any infections. CONCLUSIONS: MRSA PCR nasal swabs have a high negative predictive value for all infections. Our data support the use of MRSA PCR nasal swabs to rule out MRSA infection and thereby allow early de-escalation of MRSA coverage in hospitalized patients requiring empiric antibiotics. Implementation of MRSA screening could decrease antibiotic-associated morbidity, resistance, and costs. More studies should be conducted to validate these results and support these findings.

Pharmacist-Driven Methicillin-Resistant S. aureus Polymerase Chain Reaction Testing for Pneumonia.

BACKGROUND: Nasal colonization with methicillin-resistant Staphylococcus aureus (MRSA) can be detected using nasal swab polymerase chain reaction (PCR) assay and is associated with clinical MRSA infection. The MRSA nasal PCR has a rapid turnaround time and a negative predictive value for MRSA pneumonia of >98%; however, data are limited in critically ill patients. OBJECTIVE: The purpose of this study is to determine the impact of a pharmacist-driven algorithm, utilizing MRSA PCR nasal screening on duration of anti-MRSA therapy in patients admitted to the intensive care unit (ICU) with suspected pneumonia. METHODS: A single-center pre/post study was conducted in 4 ICUs at a large tertiary care community hospital. Adult patients admitted to the ICU initiated on vancomycin or linezolid for pneumonia managed using a pharmacist-driven MRSA PCR algorithm were included in the algorithm cohort. A historical cohort with standard management was matched 1:1 by age, type of pneumonia, and Acute Physiology and Chronic Health Evaluation II (APACHE II) score. The primary outcome was duration of anti-MRSA therapy. Secondary outcomes included MRSA rates, number of vancomycin levels, new onset of acute kidney injury (AKI), ICU length of stay (LOS), hospital LOS, and mortality. RESULTS: Of the 245 patients screened, 50 patients met inclusion criteria for the algorithm cohort and were matched to 50 patients in the historical cohort. The duration of anti-MRSA therapy was significantly lower compared with the historical cohort (47 vs 95 hours; P < 0.001). Secondary outcomes were similar between groups for MRSA rates, new onset of AKI, LOS, and mortality. There were less vancomycin levels ordered in the algorithm cohort (2 vs 3, P = 0.026). CONCLUSIONS: A pharmacist-driven MRSA PCR algorithm significantly reduced anti-MRSA duration of therapy in critically ill patients with pneumonia. Future studies should validate these results in critically ill populations and in settings where MRSA pneumonia is more prevalent.

Methicillin-Resistant Staphylococcus aureus Hospital-Acquired Pneumonia/Ventilator-Associated Pneumonia.

Methicillin-resistant Staphylococcus aureus (MRSA) is a common cause of hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP). MRSA pneumonia is associated with significant morbidity and mortality. Several virulence factors allow S. aureus to become an effective pathogen. The polysaccharide intracellular adhesin allows for the production of biofilms, some strains can produce capsular polysaccharides that protect against phagocytosis, microbial surface components recognizing adhesive matrix molecules (MSCRAMMs) allow for colonization of epithelial surfaces, and S. aureus secretes several exotoxins that aid in tissue destruction. The α-hemolysin exotoxin secreted by S. aureus is one of the most important virulence factors for the bacteria. The diagnosis of MRSA pneumonia can be challenging; the infection may present as a mild respiratory infection or severe respiratory failure and septic shock. Many individuals are colonized with MRSA and thus a positive nasopharyngeal swab does not confirm infection in the lower respiratory tract. The management of MRSA pneumonia has evolved. Historically, vancomycin has been the primary antibiotic used to treat MRSA pneumonia. Over the past decade, prospective studies have shown that linezolid leads to higher rates of clinical cure. Monoclonal antibodies are being studied as potential therapeutic options. MRSA is an important cause of HAP/VAP; novel diagnostics may facilitate rapid diagnosis of this infection and the available literature should be used to make informed decisions on management.

Impact of Prior-to-Admission Methicillin-Resistant Staphylococcus aureus Nares Screening in Critically Ill Adults With Pneumonia.

BACKGROUND: The high negative predictive value (NPV) of a negative nasal methicillin-resistant Staphylococcus aureus (MRSA) result in suspected MRSA pneumonia is well established; however, data are limited on the NPV of samples collected prior to hospital admission for critically ill patients. OBJECTIVE: To evaluate the predictive characteristics of MRSA nares screening performed prior to hospital admission in critically ill adult patients diagnosed with pneumonia. METHODS: A retrospective analysis was conducted in critically ill patients with pneumonia and MRSA nares screening within 60 days of respiratory culture. The primary outcome was NPV of MRSA nares for MRSA pneumonia using samples within 60 days compared to in-hospital respiratory cultures. A sensitivity analysis was performed for samples within 30 days. Secondary outcomes were prevalence, positive predictive value (PPV), sensitivity, specificity, and MRSA pneumonia risk factors. RESULTS: The NPV for MRSA nares screening collected prior to hospital admission was high at 98% (95% CI = 96%-99%) for samples collected within 60 days (n = 243) and 99% (95% CI: 94%-99.9%) for samples within 30 days (n = 119). Specificity for MRSA nares collected 60 days prior to admission (96%, 95% CI: 93-98) and 30 days (96%, 95% CI: 91%-99%) were both high. PPV and sensitivity were lower. Risk factors for MRSA pneumonia were similar. CONCLUSION AND RELEVANCE: MRSA nares screening within 60 days of intensive care unit admission has a high NPV and specificity for MRSA pneumonia in critically ill patients and may be a powerful stewardship tool for avoidance of empirical anti-MRSA therapy.

Clinical Utility of Dual Anterior Nares and Oropharynx MRSA Screening PCR for Patients with Suspected Pneumonia.

We reviewed the electronic health records of 1,419 inpatients with anterior nares (AN) and oropharynx (OP) MRSA PCR tests. Concordance was 96.5%. In discordant cases, AN negative-OP positive results increased detection of probable MRSA pneumonia by only 0.3%. A dual testing approach has limited utility in detecting MRSA pneumonia and increases resource utilization.

[Community-acquired Staphylococcus aureus pneumonia]. / Pneumonie communautaire à staphylocoque doré.

We report a clinical case of a patient hospitalized for community-acquired Staphylococcus aureus pneumonia. A 26-year-old patient with no medical history went to the emergency department for fever. He quickly developed acute respiratory failure and community-acquired Staphylococcus aureus pneumonia as well as bacteremia were confirmed. This pulmonary infection is rare but can affect all age groups and occur in a variety of ways. Patients with community-acquired Staphylococcus aureus pneumonia have more severe clinical outcomes than those with community-acquired pneumonia caused by other germs. The article discusses the main characteristics of community-acquired Staphylococcus aureus pneumonia and recalls the recommendations in case of bacteremia with Staphylococcus aureus.

Nous rapportons le cas clinique d'un patient de 26 ans, sans antécédents médicaux, se présentant au service des urgences pour cause de fièvre persistante depuis plusieurs jours. Dans le décours de son admission à l'hôpital, le patient développe une insuffisance respiratoire aiguë d'installation rapide. Une pneumonie communautaire associée à une bactériémie à staphylocoque doré est alors mise en évidence. Les pneumonies communautaires à staphylocoque doré sont rares, mais peuvent toucher toutes les tranches d'âge et se présenter de façon variée. Leur sévérité est plus importante que celle des pneumonies communautaires imputées à d'autres germes. Par le biais de ce cas clinique, les principales caractéristiques des pneumonies communautaires à staphylocoque doré sont discutées et les recommandations médicales associées sont abordées.

Cavitary Pneumonia Due to Methicillin-Resistant Staphylococcus aureus in a Non-Immunocompromised Patient After an Endoscopy: A Case Report.

BACKGROUND Methicillin-resistant Staphylococcus aureus (MRSA) pneumonia has well-defined characteristics. We present a case of cavitary pneumonia due to MRSA in a patient who had undergone a recent outpatient gastroscopic procedure. CASE REPORT A 32-year-old man presented at the Emergency Department with tonic-clonic seizures of 2 min durations. He had a history of seizures without current treatment or use of psychostimulant drugs. His personal history referred to hypothyroidism treated with levothyroxine, morbid type 3 obesity, gastritis with a gastric ulcer, penicillin allergies, and an ambulatory endoscopy with a biopsy (7 days ago) for erosive gastropathy. On the 3rd day of admission to the Intensive Care Unit (ICU), a bronchoscopy was performed, which showed a reddened mucosa with hemorrhagic points and a cavitary area in the right main bronchus. Multiple polymerase chain reaction and mass spectrometry analyses of samples of bronchioalveolar lavage from the bronchus revealed MRSA with a mechanism of resistance to the mecA gene (1×105 colony-forming unit/mL). The laboratory results for the cerebrospinal fluid were negative for bacterial growth. CONCLUSIONS This is a rare case of cavitary pneumonia due to MRSA of clinical and epidemiological characteristics, which is unusual after an outpatient endoscopic procedure.

Eosinophilic lung disease as a sequela of MSSA pneumonia.

Eosinophilic lung diseases are a rare group of lung disorders with multiple known and unknown aetiologies and the diagnosis is often challenging. We present a case of a young man who was admitted with pneumonia due to methicillin-sensitive Staphylococcus aureus and was discharged on antibiotics. He presented to the emergency department approximately 2 weeks after discharge with high-grade fever, cough and shortness of breath associated with serum and bronchoalveolar lavage eosinophilia. He was then treated with steroids with complete resolution of disease process.

Predictive Value of the Methicillin-Resistant Staphylococcus aureus Nasal Swab for Methicillin-Resistant Staphylococcus aureus Ventilator-Associated Pneumonia in the Trauma Patient.

Background: Many trauma centers have empiric treatment algorithms for ventilator-associated pneumonia (VAP) treatment prior to culture results that include antibiotic agents for methicillin-resistant Staphylococcus aureus (MRSA) coverage that can have adverse effects. This is the only study to evaluate risk factors and MRSA nasal swabs to risk-stratify trauma patients for MRSA VAP, thereby potentially limiting the need for empiric vancomycin. Patients and Methods: This was a single institution retrospective cohort study. Adult patients admitted to the trauma intensive care unit (ICU) between January 2013 and December 2017 who had a MRSA nasal swab and subsequently met criteria for VAP were included. Demographics, risk factors for MRSA pneumonia, and culture results were collected. Results: A total of 140 patients met inclusion criteria. The negative predictive value (NPV) of MRSA nasal swab at predicting subsequent MRSA pneumonia was 97%. The sensitivity, specificity, and positive predictive value were 50.0%, 96.2%, and 44.4%, respectively. Smokers were more likely to develop MRSA pneumonia, odds ratio: 7.0 (p = 0.02). When considering non-smokers with a negative MRSA nasal swab, NPV was 100%. Conclusions: This is the only study to date that assesses the utility of MRSA nasal swab and risk factor data to guide empiric VAP antibiotic therapy in trauma patients. Smoking was found to be a risk factor for MRSA pneumonia. The use of MRSA nasal swabs in combination with smoking status to guide empiric use of MRSA coverage antibiotic agents is recommended because of a 100% NPV. When utilized, as many as 68% of patients may safely be spared MRSA coverage antibiotic agents and the related adverse effects.

Association between a rapid diagnostic test to detect methicillin-resistant Staphylococcus Aureus pneumonia and decreased vancomycin use in a medical intensive care unit over a 30-month period.

Vancomycin overuse is common, yet few data are available regarding how to improve stewardship of this antibiotic. We identify an association between use of a PCR assay to rule out MRSA pneumonia and a significant, sustained decrease in average vancomycin days of therapy over a 30-month period.

Accuracy of Molecular Amplification Assays for Diagnosis of Staphylococcal Pneumonia: a Systematic Review and Meta-analysis.

Rapid and accurate identification of staphylococcal pneumonia is crucial for effective antimicrobial stewardship. We performed a meta-analysis to evaluate the diagnostic value of nucleic acid amplification tests (NAAT) from lower respiratory tract (LRT) samples from suspected pneumonia patients to avoid superfluous empirical methicillin-resistant Staphylococcus aureus (MRSA) treatment. PubMed, Scopus, Embase, Web of Science, and the Cochrane Library Database were searched from inception to 2 September 2020. Data analysis was carried out using a bivariate random-effects model to estimate pooled sensitivity, specificity, positive likelihood ratio (PLR), and negative likelihood ratio (NLR). Of 1,808 citations, 24 publications comprising 32 data sets met our inclusion criteria. Twenty-two studies (n = 4,630) assessed the accuracy of the NAAT for methicillin-sensitive S. aureus (MSSA) detection, while 10 studies (n = 2,996) demonstrated the accuracy of the NAAT for MRSA detection. The pooled NAAT sensitivity and specificity (with 95% confidence interval [CI]) for all MSSA detection were higher (sensitivity of 0.91 [95% CI, 0.89 to 0.94], specificity of 0.94 [95% CI, 0.94 to 0.95]) than those of MRSA (sensitivity of 0.75 [95% CI, 0.69 to 0.80], specificity of 0.88 [95% CI, 0.86 to 0.89]) in lower respiratory tract (LRT) samples. NAAT pooled sensitivities differed marginally among different LRT samples, including sputum, endotracheal aspirate (ETA), and bronchoalveolar lavage (BAL) fluid. Noticeably, NAAT pooled specificity against microbiological culture was consistently ≥88% across various types of LRT samples. A meta-regression and subgroup analysis of study design, sample condition, and patient selection method could not explain the heterogeneity (P > 0.05) in the diagnostic efficiency. This meta-analysis has demonstrated that the NAAT can be applied as the preferred initial test for timely diagnosis of staphylococcal pneumonia in LRT samples for successful antimicrobial therapy.

Genotypic and Phenotypic Characterization of Staphylococcus aureus Isolates from the Respiratory Tract in Mechanically-Ventilated Patients.

Staphylococcus aureus is a commensal and frequent colonizer of the upper respiratory tract. When mechanical ventilation disrupts natural defenses, S. aureus is frequently isolated from the lower airways, but distinguishing between colonization and infection is difficult. The objectives of this study were (1) to investigate the bacterial genome sequence in consecutive isolates in order to identify changes related to the pathological adaptation to the lower respiratory tract and (2) to explore the relationship between specific phenotypic and genotypic features with the patient's study group, persistence of the clinical isolate and clinical outcome. A set of 94 clinical isolates were selected and corresponded to 34 patients that were classified as having pneumonia (10), tracheobronchitis (11) and bronchial colonization (13). Clinical strains were phenotypically characterized by conventional identification and susceptibility testing methods. Isolates underwent whole genome sequencing using Illumina HiSeq4000. Genotypic characterization was performed with an in-house pipeline (BacterialTyper). Genomic variation arising within-host was determined by comparing mapped sequences and de novo assemblies. Virulence factors important in staphylococcal colonization and infection were characterized using previously established functional assays. (1) Toxin production was assessed using a THP-1 cytotoxicity assay, which reports on the gross cytotoxicity of individual isolates. In addition, we investigated the expression of the major virulence factor, alpha-toxin (Hla) by Western blot. (2) Adhesion to the important extracellular matrix molecule, fibronectin, was determined using a standardized microtitre plate assay. Finally, invasion experiments using THP-1 and A539 cell lines and selected clinical strains were also performed. Repeated isolation of S. aureus from endotracheal aspirate usually reflects persistence of the same strain. Within-host variation is detectable in this setting, but it shows no evidence of pathological adaptation related to virulence, resistance or niche adaptations. Cytotoxicity was variable among isolates with 14 strains showing no cytotoxicity, with these latter presenting an unaltered Fn binding capacity. No changes on cytotoxicity were reported when comparing study groups. Fn binding capacity was reported for almost all strains, with the exception of two strains that presented the lowest values. Strains isolated from patients with pneumonia presented a lower capacity of adhesion in comparison to those isolated during tracheobronchitis (p = 0.002). Hla was detected in 71 strains (75.5%), with most of the producer strains in pneumonia and bronchial colonization group (p = 0.06). In our cohort, Hla expression (presence or absence) in sequential isolates was usually preserved (70%) although in seven cases the expression varied over time. No relationship was found between low cytotoxicity and intracellular persistence in invasion experiments. In our study population, persistent S. aureus isolation from airways in ventilated patients does not reflect pathological adaptation. There is an important diversity of sequence types. Cytotoxicity is variable among strains, but no association with study groups was found, whereas isolates from patients with pneumonia had lower adhesion capability. Favorable clinical outcome correlated with increased bacterial adhesion in vitro. Most of the strains isolated from the lower airways were Hla producers and no correlation with an adverse outcome was reported. The identification of microbial factors that contribute to virulence is relevant to optimize patient management during lower respiratory tract infections.

A case of methicillin resistant Staphylococcus aureus necrotizing pneumonia with pulmonary cryptococcosis.

A 37-year-old healthy man was transferred to the emergency department of this hospital because of fever and hemoptysis. A radiograph of the chest revealed a cavitary lesion in the right upper lobe. Computed tomography of the chest showed necrotizing cavitary pneumonia. Urgent throacoscopic lobectomy was performed. Sputum and intraoperative pleural pus grew methicillin resistant Staphylococcus aureus (MRSA). The pathological examination reportedly revealed cryptococcal infection. He had a full recovery after intravenous linezolid treatment.

Neumonía estafilocócica complicada en un paciente pediátrico: a propósito de un caso clínico / Stafilocócica pneumony complicated in a pediatric patient: on the purpose of a clinical case

La neumonía es definida por la Organización Mundial de Salud (OMS) como una infección respiratoria aguda que afecta a los alvéolos pulmonares, dificultando la respiración y absorción de oxígeno afectando a la población infantil. Por eso se propuso analizar la neumonía estafilocócica complicada con enfoque clínico, radiológico y tratamiento en el paciente pediátrico para establecer elementos que ayuden a la elaboración de protocolos de diagnóstico y tratamiento. Se realizó un estudio de tipo documental, observacional y analítico mediante la entrevista directa con el paciente y familiares y el análisis clínico de los signos y síntomas presentados por el paciente. Mediante la valoración clínico, radiológico y oportuno tratamiento en el paciente pediátrico con neumonía estafilocócica complicada, se logró establecer elementos que podrán ayudar a la elaboración de un protocolo de diagnóstico y tratamiento de dicha patología(AU)

Pneumonia is defined by the World Health Organization (WHO) as an acute respiratory infection that affects the pulmonary alveoli, making it difficult to breathe and absorb oxygen, affecting the child population. Therefore, it was proposed to analyze complicated staphylococcal pneumonia with a clinical, radiological and treatment approach in the pediatric patient to establish elements that help to develop diagnostic and treatment protocols. A documentary, observational and analytical study was conducted through a direct interview with the patient and family members and the clinical analysis of the signs and symptoms presented by the patient. By means of the clinical, radiological evaluation and timely treatment in the pediatric patient with complicated staphylococcal pneumonia, it was possible to establish elements that may help to elaborate a protocol for the diagnosis and treatment of said pathology(AU)

Association of Staphylococcus aureus Colonization and Pneumonia in the Intensive Care Unit.

Importance: Carriage of Staphylococcus aureus is associated with S aureus infection. However, associations between S aureus carriage and the development of S aureus intensive care unit (ICU) pneumonia (SAIP) have not been quantified accurately, and interpretation of available data is hampered because of variations in definitions. Objective: To quantify associations of patient-related and contextual factors, including S aureus colonization status, with the occurrence of SAIP. Design, Setting, and Participants: This cohort study was conducted in ICUs of 30 hospitals in 11 European countries, geographically spread across 4 regions. Among patients with an anticipated length of stay 48 hours or longer who were undergoing mechanical ventilation at ICU admission, S aureus colonization was ascertained in the nose and lower respiratory tract. From this group, S aureus-colonized and noncolonized patients were enrolled into the study cohort in a 1:1 ratio. Data analysis was performed from May to November 2019. Main Outcomes and Measures: SAIP was defined as any pneumonia during the ICU stay developing 48 hours or more after ICU admission with S aureus isolated from lower respiratory tract specimens or blood samples. The incidence of SAIP was derived in the study cohort and estimated on the weighted incidence calculation for the originating overarching population, while taking competing events into account. Weighted risk factor analysis was performed using Cox multivariable regression. Results: The study cohort consisted of 1933 patients (mean [SD] age, 62.0 [16.0] years); 1252 patients (64.8%) were men, and 950 patients (49.1%) were S aureus carriers at ICU admission. In all, 304 patients (15.7%) developed ICU-acquired pneumonia, of whom 131 patients (6.8%) had SAIP. Weighted SAIP incidences were 11.7 events per 1000 patient-days in the ICU for S aureus-colonized patients and 2.9 events per 1000 patient-days in the ICU for noncolonized patients (overall incidence, 4.9 events per 1000 patient-days in the ICU). The only factor independently associated with SAIP was S aureus colonization status at ICU admission (cause-specific hazard ratio, 3.6; 95% CI, 2.2-6.0; P < .001). There were marked regional differences in SAIP incidence and cause-specific hazard ratios for colonization status. Conclusions and Relevance: SAIP incidence was 4.9 events per 1000 ICU patient-days for patients undergoing mechanical ventilation at ICU admission (or shortly thereafter). The daily risk of SAIP was 3.6 times higher in patients colonized with S aureus at ICU admission compared with noncolonized patients.