A history of Panton-Valentine leukocidin (PVL)-associated infection protects against death in PVL-associated pneumonia

Panton-Valentine leukocidin (PVL) is a Staphylococcus aureus toxin associated with skin and soft-tissue infections (SSTIs) and life-threatening necrotizing pneumonia in humans. Recent reports have demonstrated that neutralizing antibody to PVL is not protective against SSTI recurrence, thus raising a controversy about the expected clinical benefits from the use of PVL as a vaccine target. To investigate the impact of pre-existing immunity to PVL on the outcome of necrotizing pneumonia, we conducted a retrospective study of 114 cases and searched for an association between the history of PVL-associated infection and outcome. Death and severity factors, such as the need for mechanical ventilation and inotrope support, were significantly less frequent in patients with prior PVL-associated infection than in those without. These findings indicate a protective role of PVL-directed immunity in severe systemic PVL-associated disease, suggesting that anti-PVL vaccine could provide strong clinical benefits in this setting.     

Traitements antitoxiniques et pneumopathies nécrosantes à Staphylococcus aureus sécréteurs de leucocidine de Panton-Valentine

Staphylococcus aureus is responsible for two main clinical presentations in humans: suppurative infections and toxigenic diseases. A small percentage of S. aureus strains secrete Panton-Valentine leukocidin (PVL). This toxin is implicated in skin infections, furunculosis, osteoarticular infections, and particularly, in serious pulmonary infections known as necrotizing pneumonia, which affect immunocompetent patients with no comorbidity. A clear outline of the clinical presentation was described recently. Necrotizing pneumonia caused by PVL-secreting S. aureus strains is characterized by a combination of fever, hemoptysis, multilobar alveolar infiltrations, and leukopenia. The disease usually progresses to toxic shock or refractory hypoxemia. A number of interesting therapies targeting leukocidin have been proposed over the past few years based on in vitro data. This review focuses on the physiopathological basis and on the therapeutic relevance of various drugs.     

Implant retention and high rate of treatment failure in hematogenous acute knee and hip prosthetic joint infections

ObjectivesOnly few studies evaluated hematogenous prosthetic joint infections. We aimed to describe the characteristics of these infections and factors associated with management failure.MethodsWe selected hematogenously-acquired infections, defined by the occurrence of infectious symptoms more than a year after implantation among records of patients treated for hip and knee prosthetic joint infections at Montpellier University Hospital between January 2004 and May 2015. Failure was defined by death due to prosthesis-related infection, need for prosthesis removal in case of conservative treatment, or recurrence of infectious signs on a new prosthesis.ResultsForty-seven patients with hematogenous prosthetic joint infection were included (33 knee infections and 14 hip infections). Infectious agents were streptococci (43%), Staphylococcus aureus (43%), Gram-negative bacilli (13%), and Listeria monocytogenes (2%). Thirty-one patients were initially treated with debridement and implant retention and 15 with prosthesis removal (three with one-stage surgery, 10 with two-stage surgery). The median duration of antibiotic therapy was 66.5 days. The overall failure rate was 52% (24/48), 71% (22/31) with implant retention strategy, 13% (2/15) with prosthesis removal, and 63% (12/19) in case of Staphylococcus aureus infection. Conservative treatment was appropriate (arthrotomy on a well-implanted prosthesis without sinus tract and symptom onset <21 days) in 13/31 patients (42%) with a failure rate still high at 69% (9/13). The only factor associated with failure was conservative surgical treatment.ConclusionThe high risk of failure of conservative treatment for hematogenous prosthetic joint infections should lead to considering prosthesis replacement as the optimal strategy, particularly with Staphylococcus aureus.     

Staphylococcus aureus native arthritis over 10 years

ObjectivesSeptic arthritis is associated with significant case fatality and morbidity. Staphylococcus aureus is the most common cause of arthritis. We aimed to analyze the microbiological features of S. aureus causing native arthritis and to investigate their influence on the clinical outcome of the infection.Patients and methodsWe conducted a retrospective study including all episodes of S. aureus native arthritis between 2005–2015. Phenotypic (antimicrobial susceptibility, β-hemolysis, agr functionality, biofilm formation) and genotypic characteristics (pulsed-field gel electrophoresis, DNA microarrays) were investigated. The primary endpoint was microbiological failure of treatment, including infection relapse, persistence, or attributable death.ResultsTwenty-nine patients were included (65.5% of men, mean age: 59): seven (24.1%) patients presenting with methicillin-resistant S. aureus (MRSA) native arthritis and 19 with methicillin-susceptible S. aureus (MSSA) native arthritis. Treatment failure occurred in seven (26.9%) patients (4/7 patients [57.1%] among MRSA infections vs. 3/19 [15.8%] among MSSA infections). The persistence rate was similar in MRSA and MSSA infections (1/7 vs. 3/19). However, the case fatality was significantly higher in patients with MRSA infection (3/7 vs. 0/19). The most frequent clonal complex (CC) was CC5 (38.1%). MSSA showed higher genetic variability (nine CCs) versus MRSA (3 CCs).ConclusionsBeyond methicillin resistance, we did not find phenotypic or genotypic factors associated with the poor outcome of S. aureus native arthritis. CC5 was the major CC, showing the higher genetic variability of MSSA versus MRSA.     

Panton-valentine leucocidin carrying Staphylococcus aureus causing necrotizing pneumonia inactivates the JAK/STAT signaling pathway and increases the expression of inflammatory cytokines

PurposeMethicillin-resistant Staphylococcus aureus (MRSA) carrying Panton-Valentine leukocidin, a pore-forming toxin, is a common cause of necrotizing pneumonia. However, the early pulmonary inflammatory response following PVL(+) MRSA infection is unknown. The purpose of this study was to use a murine model to determine the effect of PVL(+) MRSA on lung tissues and the expression of cytokines and JAK and STAT mRNA and protein.MethodsMice were randomly divided into 3 groups and intra-nasally treated with PBS (control group), recombinant PVL (rPVL group), and PVL(+) MRSA (PVL group). At 24 and 48 h after inoculation, bronchoalveolar lavage fluid (BALF) was tested for cytokine levels, and lung tissues were tested for JAK and STAT mRNA and protein expression, and examined after hematoxylin and eosin staining.ResultsMice infected with the PVL(+) strain became ill, characterized by impaired mobility, hunched posture, ruffled fur, and labored breathing. Lung tissue exhibited tissue necrosis and hemorrhage. BALF levels of IL-8, TNF-α, IFN-γ, IL-12, sICAM-1, and sVCAM-1 were increased in the rPVL or PVL groups, while levels of IL-10 and IL-4 levels were similar among the groups. JAK1 and STAT1 mRNA expression and protein levels were increased in lung tissue from mice infected with PVL(+) MRSA and rPVL.ConclusionsPVL is a significant S. aureus virulence factor, and upregulates the expression of proinflammatory cytokines but does not affect the expression of anti-inflammatory cytokines. The effect of PVL may be due to JAK/STAT pathway activation. Blockade of the JAK/STAT pathway may decrease the severity of PVL(+) MRSA pneumonia.     

Molecular testing for respiratory pathogens in sickle cell disease adult patients presenting with febrile acute chest syndrome

BackgroundDifferentiating acute chest syndrome (ACS) from community-acquired pneumonia (CAP) is challenging in adults presenting with major sickle cell disease (SCD) (semiological similarity, rare microbiological documentation). We aimed to assess the usefulness of nucleic acid amplification test (NAAT) for respiratory pathogens, in combination with standard bacteriological investigations, in febrile ACS adult patients presenting with major SCD.MethodsWe performed a prospective, monocentric, observational study of 61 SCD adults presenting with febrile ACS from February 2015 to April 2016. Systematic blood, urine, and respiratory specimens were collected, before antibiotic initiation, for culture, urinary antigen tests, serology, and NAAT for respiratory pathogens.ResultsA pathogen was detected in 12 febrile ACS (19.7%): four viruses (6.6%) (Rhinovirus; Influenza A/B), seven bacteria (11.4%) (S. aureus, S. pneumoniae, K. pneumoniae, L. pneumophila, M. pneumoniae), one mixed infection (1.6%) (S. aureus and Influenza B). NAAT only detected L. pneumophila in one case (serogroup 2). Apart from a significantly shorter antibiotic therapy duration (6.1 vs. 7.8 days, P = 0.045), no difference was observed between undocumented and microbiologically-documented febrile ACS.ConclusionUsing NAAT for the detection of respiratory pathogens in adults presenting with SCD slightly improved the microbiological diagnostic of febrile ACS, although respiratory infections are not the main etiological factor.     

Staphylococcus aureus carrying Panton-Valentine leukocidin genes nasal colonization and skin infection: screening in case of outbreak in a school environment

Objectives

An outbreak of Staphylococcus aureus (SA) carrying the gene coding for Panton-Valentine leukocidin (PVL) skin infections in a primary school was investigated and monitored in the Val-d’Oise region (Greater Paris) in 2006.

Patients and methods

Skin infections reported after the beginning of the school year in primary-school teachers, students and their relatives were diagnosed and treated at the local hospital and screening for nasal colonization was implemented. A patient presenting with folliculitis, an abscess or furuncle with a positive-skin test or nasal swab for SA-PV was considered to be a case of infection. Colonization was defined as identification of SA-PVL in a nasal swab in the absence of skin lesions. In addition to recommended control measures, treatment by topical intranasal mupirocin was prescribed to all colonized patients and relatives of infected patients.

Results

Over five months, 22 cases of PVL-positive SA skin infections, including a case of simple folliculitis, were confirmed in 15 primary-school students (attack rate = 18.5%) and seven relatives. The occurrence of nasal colonization in relatives not attending the same school ranged from 0 to 30% according to the number of cases of skin infection in the family (p < 0,01). Two-thirds of patients treated with mupirocin were decolonized.

Conclusion

Transmission of this SA strain in school and family environments confirms the epidemic potential of PVL-positive isolates; however, screening for nasal colonization should be restricted to cases of skin infection and people in their immediate environment.     

Methicillin-resistant�CStaphylococcus aureus Hospitalizations, United States

Methicillin-resistant Staphylococcus aureus (MRSA) is increasingly a cause of nosocomial and community-onset infection with unknown national scope and magnitude. We used the National Hospital Discharge Survey to calculate the number of US hospital discharges listing S. aureus–specific diagnoses, defined as those having at least 1 International Classification of Diseases (ICD)-9 code specific for S. aureus infection. The number of hospital discharges listing S. aureus-specific diagnoses was multiplied by the proportion of methicillin resistance for each corresponding infection site to determine the number of MRSA infections. From 1999 to 2000, an estimated 125,969 hospitalizations with a diagnosis of MRSA infection occurred annually, including 31,440 for septicemia, 29,823 for pneumonia, and 64,706 for other infections, accounting for 3.95 per 1,000 hospital discharges. The method used in our analysis may provide a simple way to assess trends of the magnitude of MRSA infection nationally.     

Skin and soft tissue infections due to Panton–Valentine leukocidin producing Staphylococcus aureus

Objective

The authors had for aim to describe the epidemiological and clinical characteristics, and the treatment of patients presenting with skin and soft tissue infections due to Panton–Valentine leukocidin (PVL) producing Staphylococcus aureus in the Nord-Pas-de-Calais (NPDC) region, North of France.

Methods

We included patients presenting with PVL producing S. aureus infection from seven hospitals in the NPDC region, between February 2004 and April 2008. We retrospectively collected patient data using a standardized questionnaire. The features of patients presenting with skin and soft tissue were then analyzed.

Results

PVL producing S. aureus was isolated from 64 patients. Fifty-four patients presented with skin and soft tissue infections. The mean age of patients was 23.8 years (63% male patients). The mean number of persons living with the infected patient was 4.5 (vs. 2.5 in NPDC). The lesions were abscesses with inflammatory signs in 64.8% of the cases (20% were necrotic). Among the patients, 70.3% carried a methicillin resistant strain. Antibiotics per os were used for 83.3% of patients; the first-line antibiotics were considered inadequate in 53.3% of the cases. Among the patients, 83.3% underwent surgery. Fourteen out of 38 patients with available data had been exposed to antibiotic therapy during the three months before hospital management.

Conclusion

Recent exposure to antibiotics and living with a high number of persons are reasons to suspect a PVL producing S. aureus infection in patients with skin abscess.     

The ZEPHyR study: A randomized comparison of linezolid and vancomycin for MRSA pneumonia

BackgroundMethicillin-resistant Staphylococcus aureus (MRSA) accounts for 10–40% of hospital-acquired pneumonia, and even more in intensive care units. The current guidelines for the treatment of MRSA nosocomial pneumonia include vancomycin and linezolid. The authors of 2 prospective randomized trials comparing vancomycin and linezolid in nosocomial pneumonia had concluded to the non-inferiority of linezolid. A slight superiority of linezolid was observed in the MRSA pneumonia subgroup, in terms of clinical success and survival, but no definite conclusion could be drawn.MethodsA prospective randomized study was made to compare a fixed linezolid dose to dose-optimized vancomycin for the treatment of bacteriologically proven MRSA nosocomial pneumonia (ZEPHyR Study).ResultsAmong the 165 patients treated by linezolid (57.6%) in the PP population, 95 were clinically cured at the end of the study, compared to 81 of the 174 patients treated by vancomycin (46.6%) (IC 95% of the difference 0.5%–21.6%, P = 0.042). Nephrotoxicity in the mITT population reached 8.4% in the linezolid group compared to 18.2% in the vancomycin group.ConclusionLNZ was superior to vancomycin for the treatment of MRSA nosocomial pneumonia.     

57例甲型流感病毒感染合并肺炎患者感染指标与病毒载量相关性

 目的 分析流感高峰期甲型流感病毒感染且合并肺炎患者的临床表现特点。方法 将2018年12月—2019年4月某院呼吸内科甲型流感病毒感染合并肺炎住院患者列为甲流合并肺炎组,内科门诊就诊的甲型流感病毒感染患者列为甲流组,体检中心正常体检者列为体检组,回顾性分析患者临床表现和特征。结果 甲流合并肺炎组57例,甲流组42例,体检组33例,三组年龄比较,差异有统计学意义（F=16.57,P<0.001）,甲流合并肺炎组患者年龄最大,为（61.65±16.92）岁。甲流合并肺炎组患者白细胞（WBC）计数中性粒细胞百分比以及C反应蛋白（CRP）、降钙素原（PCT）、血清淀粉样蛋白（SAA）检测值均高于甲流组患者和体检组健康者（均P<0.05）。甲流合并肺炎组患者甲型流感病毒载量核酸检测CT值（16.18±2.53）低于甲流组患者（19.30±4.12）,差异有统计学意义（t=2.100,P=0.039）;甲流合并肺炎组患者检测结果CT值与其感染指标CRP、PCT相关系数（r）分别为-0.51、-0.55,均呈负相关。结论 甲型流感病毒感染患者为老年人,甲型流感病毒载量高,感染指标CRP、PCT升高提示感染者存在合并肺炎的风险,可为临床诊疗提供依据。     

全国细菌耐药监测网2021年泌尿外科患者分离细菌耐药监测报告

目的 了解2021年全国泌尿外科患者分离细菌菌种分布及耐药情况。方法 按照全国细菌耐药监测网(CARSS)技术方案,应用WHONET 5.6软件对2021年所有CARSS成员单位上报的泌尿外科患者分离细菌及药敏试验结果数据进行分析。结果 泌尿外科患者共分离菌株232 603株,其中革兰阴性菌166 483株(71.6%),革兰阳性菌66 120株(28.4%)。标本构成中排名前5位的分别为尿、血、伤口分泌物、痰和腹腔积液。分离细菌中革兰阴性菌排名前5位的分别为大肠埃希菌(57.5%)、肺炎克雷伯菌(10.8%)、铜绿假单胞菌(5.8%)、奇异变形杆菌(5.3%)和阴沟肠杆菌(3.4%);分离细菌中革兰阳性菌排名前5位的分别为粪肠球菌(36.2%)、屎肠球菌(14.9%)、表皮葡萄球菌(10.5%)、无乳链球菌(9.5%)和金黄色葡萄球菌(7.3%)。未发现对万古霉素、替考拉宁和利奈唑胺耐药的金黄色葡萄球菌,耐甲氧西林金黄色葡萄球菌对庆大霉素、利福平、左氧氟沙星、复方磺胺甲口恶唑、克林霉素和红霉素的耐药率均高于甲氧西林敏感金黄色葡萄球菌。大肠埃希菌、肺炎克雷伯菌、奇异变形杆菌对亚胺培南(...     

Pneumonia-Associated Emergency Transfers,Functional Decline,and Mortality in Nursing Home Residents

ObjectiveTo describe nursing home residents (NHRs) transferred to the emergency department (ED) with pneumonia, and investigate the association of pneumonia with functional ability and mortality.DesignCase-control observational multicenter study.Setting and participantsParticipants of the FINE study, including 1037 NHRs presenting to 17 EDs in France over 4 nonconsecutive weeks (1 per season) in 2016, mean age 87.2 years ± 7.1, 68.4% women.MethodsActivities of daily living (ADL) performance evolution between (1) 15 days before transfer and (2) within 7 days after discharge back to the nursing home was compared in NHRs with or without pneumonia. The association of pneumonia with functional evolution was investigated by a mixed-effect linear regression of ADL and mortality was compared by a χ² test.ResultsNHRs with pneumonia (n = 232; 22.4%) were more likely to have a lower ADL performance than NHRs without pneumonia (n = 805, 77.6%). They presented with a more severe clinical condition, were more likely to be hospitalized after ED and to stay longer in ED and in hospital. They showed a 0.5 decline in median ADL performance after transfer and a significantly higher mortality than NHRs without pneumonia (24.1% and 8.7%, respectively). Post-ED functional evolution did not differ significantly between NHRs with or without pneumonia.Conclusions and implicationsPneumonia-associated ED transfers resulted in longer care pathways and higher mortality, but no significant difference in functional decline. This study identified a suggestive course of symptoms that could facilitate early identification of NHRs developing pneumonia and early management to prevent ED transfer.     

Intensive care admission for Coronavirus OC43 respiratory tract infections

Background

Coronavirus OC43 infection causes severe pneumonia in patients presenting with comorbidities, but clinical signs alone do not allow for viral identification.

全国细菌耐药监测网2021年血液科患者分离细菌耐药监测报告

目的 了解全国血液科患者分离的常见病原菌分布及耐药性,为血液病感染患者抗菌药物的合理使用提供科学依据。方法 采用WHONET 5.6软件,分析2021年全国细菌耐药监测网(CARSS)网点医院按CARSS技术方案上报的血液科患者分离病原菌的分布及耐药性。结果 共收集血液科患者非重复分离菌74 300株,其中革兰阴性菌53 970株(72.6%),革兰阳性菌20 330株(27.4%)。病原菌分离率居首位的为大肠埃希菌(16 051株,21.6%),其次分别为肺炎克雷伯菌(11 214株,15.1%)、铜绿假单胞菌(6 071株,8.2%)、金黄色葡萄球菌(4 768株,6.4%)和屎肠球菌(3 600株,4.8%)。分离菌株中血标本占首位(24.6%),其次为痰(24.0%)和尿标本(16.6%)。对亚胺培南和美罗培南的耐药率：大肠埃希菌分别为4.4%、4.3%,肺炎克雷伯菌分别为10.8%、11.5%。铜绿假单胞菌对亚胺培南和美罗培南耐药率分别为16.7%、12.8%。鲍曼不动杆菌除对多黏菌素B、米诺环素和替加环素耐药率均<10%,对其他测试抗菌药物的耐药率为14.3%～27....     

上海地区粒细胞缺乏伴肺部感染血液病患者呼吸道分离细菌及耐药性多中心回顾性研究

目的了解上海地区中性粒细胞缺乏(粒缺)伴肺部感染血液病患者呼吸道分泌物检出病原菌的分布及耐药情况。方法回顾性收集2012年1月—2014年12月上海市12所医院血液科粒缺伴肺部感染住院患者呼吸道分泌物分离菌株的临床资料、药敏结果,分析病原菌分布及其药敏数据,比较不同原发疾病病原菌分布之间的差异。结果共分离病原菌623株,其中革兰阳性菌138株(22.2%),革兰阴性菌485株(77.8%),非发酵菌占革兰阴性菌的60.2%(292株)。淋巴瘤患者标本中分离革兰阳性菌构成比(35.0%)高于急性髓系白血病和急性淋巴细胞白血病患者。居前5位的细菌分别是嗜麦芽窄食单胞菌(104株,16.7%)、肺炎克雷伯菌(88株,14.1%)、鲍曼不动杆菌(62株,10.0%)、铜绿假单胞菌(56株,9.0%)、金黄色葡萄球菌(48株,7.7%)。肺炎克雷伯菌对碳青霉烯类抗生素敏感率98%,铜绿假单胞菌对亚胺培南和美罗培南的耐药率分别为24.3%、8.9%,嗜麦芽窄食单胞菌对左氧氟沙星、米诺环素、复方磺胺甲口恶唑敏感率90%,鲍曼不动杆菌对阿米卡星、头孢哌酮/舒巴坦的耐药率低于10%。耐甲氧西林金黄色葡萄球菌(MRSA)检出率为71.4%,未发现耐万古霉素、替考拉宁、利奈唑胺的金黄色葡萄球菌。结论粒缺伴肺部感染患者呼吸道分泌物分离菌株以革兰阴性菌占多数,其中非发酵菌占50%以上,细菌耐药率整体低于CHINET全国医院大样本监测结果。     

Necrotizing fasciitis—a disease of temperate and warm climates

Necrotizing fasciitis is a distinct clinical entity. It is usually due to Streptococcus pyogenes but may occasionally be caused by Staphylococcus aureus. It needs to be considered in relationship to other infections due to Streptococcus pyogenes, in which the clinical disease that occurs may be associated with the depth of inoculation of the coccus. Mild cases have been identified that are self-limiting as well as serious cases which would have succumbed without surgical debridement. It is likely that some cases of necrotic tropical ulcer are due to necrotizing fasciitis.     

Population variation in anti-S. aureus IgG isotypes influences surface protein A mediated immune subversion

BackgroundStaphylococcus aureus is a pathogen which causes life-threatening infection, the incidence of which rises during adult life. This, together with the emergence of drug-resistant strains and the expansion of more susceptible elderly populations, represents the rationale for the ongoing development of S. aureus vaccines targeting adult populations. Humoral responses to S. aureus naturally develop early in life, influence susceptibility to infection, and potentially influence the effect of vaccination. Despite this, the nature of pre-existing anti-S. aureus antibodies in healthy adult populations is not fully characterised.MethodsImmunoglobulin levels against S. aureus surface antigens were measured by a filter membrane enzyme-linked immunosorbent assay using fixed ΔSpA S. aureus as an antigen in serum samples obtained from three clinical cohorts comprising 133 healthy adult volunteers from 19 to 65 years of age. Functional capacity of antibody was also assessed, using antibody-mediated attachment of FITC-stained S. aureus to differentiated HL-60 cells.ResultsWide variation in the concentrations of immunoglobulins recognising S. aureus surface antigens was observed among individuals in all three cohorts. There was a decline of anti-S. aureus IgG1 with age, and a similar trend was observed in IgM, but not in IgA or other IgG sub-classes. Antibody mediated bacterial attachment to cells was associated with IgG1 and IgG3 concentrations in serum. The presence of SpA on the bacterial cell surface reduced antibody-mediated binding of bacteria to phagocytes in serum with low, but not high, levels of naturally occurring anti-S. aureus IgG3 antibodies.ConclusionsNaturally acquired immunoglobulin responses to S. aureus are heterogeneous in populations and their concentrations alter during adulthood. Elevated IgG1 or IgG3 titres against S. aureus enhance S. aureus recognition by phagocytosis and may be correlates of natural protection and/or vaccine efficacy in adult populations.     

Linezolid Versus Vancomycin in the Empiric Treatment of Nosocomial Pneumonia: A Cost-Utility Analysis Incorporating Results from the ZEPHyR Trial

ObjectiveTo examine the cost-effectiveness of vancomycin versus linezolid in the empiric treatment of nosocomial pneumonias incorporating results from a recent prospective, double-blind, multicenter, controlled trial in adults with suspected methicillin-resistant Staphylococcus aureus (MRSA) nosocomial pneumonia.MethodsA decision-analytic model examining the cost-effectiveness of linezolid versus vancomycin for the empiric treatment of nosocomial pneumonia was created. Publicly available cost, efficacy, and utility data populated relevant model variables. A probabilistic sensitivity analysis varied parameters in 10,000 Monte-Carlo simulations, and univariate sensitivity analyses assessed the impact of model uncertainties and the robustness of our conclusions.ResultsResults indicated that the cost per quality-adjusted life-year (QALY) increased 6% ($22,594 vs. $23,860) by using linezolid versus vancomycin for nosocomial pneumonia. The incremental cost per QALY gained by using linezolid over vancomycin was $6,089, and the incremental cost per life saved was $68,615 with the use of linezolid. Vancomycin dominated linezolid in the subset of patients with documented MRSA. The incremental cost per QALY gained using linezolid if no mortality benefit exists between agents or a 60-day time horizon was analyzed was $19,608,688 and $443,662, respectively.ConclusionsLinezolid may be a cost-effective alternative to vancomycin in the empiric treatment of patients with suspected MRSA nosocomial pneumonia; however, results of our model were highly variable on a number of important variables and assumptions including mortality differences and time frame analyzed.