Epidemiology and outcome of pneumonia caused by methicillin-resistant Staphylococcus aureus (MRSA) in Canadian hospitals

Staphylococcus aureus Pneumonia in Can Tho, Vietnam: Clinical Characteristics, Antimicrobial Resistance Profile and Risk Factors of Mortality

INTRODUCTION

Staphylococcus aureus (S. aureus) is an important pathogen in both community-acquired and hospital-acquired pneumonia. S. aureus pneumonia has a high mortality rate and serious complications. Resistance to multiple antibiotics is a major challenge in the treatment of S. aureus pneumonia. Understanding the antibiotic resistance profile of S. aureus and the risk factors for mortality can help optimize antibiotic regimens and improve patient outcomes in S. aureus pneumonia.

METHODS

A prospective cohort study of 118 patients diagnosed with S. aureus pneumonia between May 2021 and June 2023 was conducted, with a 30-day follow-up period. Demographic information, comorbidities, Charlson Comorbidity Index, clinical characteristics, outcomes, and complications were collected for each enrolled case. The data were processed and analyzed using R version 3.6.2.

RESULTS

S. aureus pneumonia has a 30-day mortality rate of approximately 50%, with complication rates of 22% for acute respiratory distress syndrome (ARDS), 26.3% for septic shock, and 14.4% for acute kidney injury (AKI). Among patients with methicillin-resistant S. aureus (MRSA) pneumonia treated with vancomycin (n = 40), those with a vancomycin minimum inhibitory concentration (MIC) ≤ 1 had significantly higher cumulative survival at day 30 compared to those with MIC ≥ 2 (log-rank test p = 0.04). The prevalence of MRSA among S. aureus isolates was 84.7%. Hemoptysis, methicillin resistance, acidosis (pH < 7.35), and meeting the Infectious Diseases Society of America/American Thoracic Society (IDSA/ATS) criteria for severe pneumonia were significantly associated with mortality in a multivariate Cox regression model based on the adaptive least absolute shrinkage and selection operator (LASSO).

CONCLUSIONS

S. aureus pneumonia is a severe clinical condition with high mortality and complication rates. MRSA has a high prevalence in Can Tho City, Vietnam. Hemoptysis, methicillin resistance, acidosis (pH < 7.35), and meeting the IDSA/ATS criteria for severe pneumonia are risk factors for mortality in S. aureus pneumonia.

Is administration of anti-MRSA drugs recommended for patients with pneumonia when MRSA is isolated from respiratory specimens? A systematic review and meta-analysis

It is unclear whether anti-methicillin-resistant Staphylococcus aureus (MRSA) drugs should be uniformly administered to patients with pneumonia when MRSA is isolated from respiratory specimens. A systematic review was conducted to evaluate the efficacy of the uniform administration of anti-MRSA drugs. Two researchers independently searched the literature as of December 2022, extracted relevant papers, and performed a meta-analysis. The outcomes were mortality and adverse events. No applicable randomized controlled trials were found during the study period, but four observational studies were extracted. The relative risk of mortality in the anti-MRSA group was 1.67 [95% confidence interval 0.65-4.30], which did not differ significantly from the non-administered group. Further investigation into the background of patients demonstrated that anti-MRSA drugs were administered to groups in which only MRSA was cultured. However, the pneumonia severity index did not differ from that in the non-treated group. No studies of adverse events were found. Our review did not find a beneficial contribution to mortality from uniform anti-MRSA medication to patients with pneumonia when MRSA was isolated from respiratory specimens. Factors determining risk-based individualized treatment should be validated as the future question.

Aetiological agents of adult community-acquired pneumonia in Japan: systematic review and meta-analysis of published data

OBJECTIVE

Epidemiological information is essential in providing appropriate empiric antimicrobial therapy for pneumonia. This study aimed to clarify the epidemiology of community-acquired pneumonia (CAP) by conducting a systematic review of published studies in Japan.

DESIGN

Systematic review.

DATA SOURCE

PubMed and Ichushi web database (January 1970 to October 2022).

ELIGIBILITY CRITERIA

Clinical studies describing pathogenic micro-organisms in CAP written in English or Japanese, excluding studies on pneumonia other than adult CAP, investigations limited to specific pathogens and case reports.

DATA EXTRACTION AND SYNTHESIS

Patient setting (inpatient vs outpatient), number of patients, concordance with the CAP guidelines, diagnostic criteria and methods for diagnosing pneumonia pathogens as well as the numbers of each isolate. A meta-analysis of various situations was performed to measure the frequency of each aetiological agent.

RESULTS

Fifty-six studies were included and 17 095 cases of CAP were identified. Pathogens were undetectable in 44.1% (95% CI 39.7% to 48.5%). Streptococcus pneumoniae was the most common cause of CAP requiring hospitalisation or outpatient care (20.0% (95% CI 17.2% to 22.8%)), followed by Haemophilus influenzae (10.8% (95% CI 7.3% to 14.3%)) and Mycoplasma pneumoniae (7.5% (95% CI 4.6% to 10.4%)). However, when limited to CAP requiring hospitalisation, Staphylococcus aureus was the third most common at 4.9% (95% CI 3.9% to 5.8%). Pseudomonas aeruginosa was more frequent in hospitalised cases, while atypical pathogens were less common. Methicillin-resistant S. aureus accounted for 40.7% (95% CI 29.0% to 52.4%) of S. aureus cases. In studies that used PCR testing for pan-respiratory viral pathogens, human enterovirus/human rhinovirus (9.4% (95% CI 0% to 20.5%)) and several other respiratory pathogenic viruses were detected. The epidemiology varied depending on the methodology and situation.

CONCLUSION

The epidemiology of CAP varies depending on the situation, such as in the hospital versus outpatient setting. Viruses are more frequently detected by exhaustive genetic searches, resulting in a significant variation in epidemiology.

Clinical characteristics and risk factors for mortality in patients with community-acquired staphylococcal pneumonia

Staphylococcus aureus (S. aureus) is increasing in prevalence as a causative pathogen of community-acquired pneumonia (CAP). However, reports on the clinical features and mortality risk factors for S. aureus CAP are limited. We therefore aimed to identify the clinical characteristics and risk factors for mortality in these patients. We performed a post hoc and multivariate analysis of a multicenter prospective observational study that included adult hospitalized patients with S. aureus CAP. To elucidate the features of S. aureus CAP, we comparatively analyzed pneumococcal CAP (PCAP). We analyzed 196 patients with S. aureus CAP and 198 patients with PCAP. S. aureus CAP had a 30-day mortality of 16% (31/196) and a higher frequency of factors such as advanced age, comorbidities, poor functional ability, altered mental status, hypoalbuminemia, hyponatremia/hypernatremia, acidemia, and hypoxemia. In the multivariate analysis, the significant risk factors for mortality in S. aureus CAP were PaO₂/FiO₂ ≤250 [adjusted odds ratio (AOR), 3.29; 95% confidence interval (CI), 1.20-9.04] and albumin <3.0 g/dL (AOR, 2.41; 95% CI, 1.01-5.83). Non-ambulatory status tended to increase the risk (AOR, 2.40; 95% CI, 0.93-6.17). Methicillin resistance was not associated with mortality. In PCAP, hypoalbuminemia and non-ambulatory status affected mortality but hypoxemia did not. In conclusion, patients with S. aureus CAP have distinct clinical features, and their mortality risk factors can include hypoxemia and hypoalbuminemia. Physicians should recognize that the factors influencing mortality might differ somewhat among causative pathogens, and appropriate management should be performed after obtaining information on the causative pathogen.

Beta hemolysin gene of Staphylococcus phage 3AJ_2017 genome is a suitable molecular marker for identification and characterization of pathogenic Staphylococcus aureus

BACKGROUND

Staphylococcus aureus cause diseases both in humans and animals. These diseases range from mild to fatal infections thus necessitating development of a specific molecular method for detection of pathogenic S. aureus.

OBJECTIVES

To identify and analyze genetic profile of pathogenic S. aureus using bacteriophage based genetic biomarkers.

METHODS

Using culture and biochemical methods, 148 S. aureus (87 %) were isolated from 170 raw milk samples taken from 10 dairy farms in Marsabit and Isiolo counties in Northern Kenya between June 2016 and February 2017. The samples were collected directly from dairy lactating cows previously diagnosed with S. aureus in a follow-up study. The isolates were analyzed by PCR and sequencing of beta hemolysin (hlb) gene. The genetic relationship between five Kenyan S. aureus isolates and five isolates previously identified was inferred.

RESULTS

From the 96 isolates screened for hlb gene, 75 (78.1%) tested positive. Some of the positive isolates yielded a band size of 975 bp, while others 1100 bp. Through Basic Local Alignment Search Tool (BLAST) search analysis, the two different band sizes (975 bp and 1100 bp) were both confirmed to be hlb gene from S. aureus isolates indicating that the difference in band size may have been due to deletions that were detected in the 975 bp hlb gene. Some S. aureus isolates from Kenya appeared to be closely related to isolates from other parts of the world, while some showed a distant relationship.

CONCLUSIONS

Phage-derived hlb gene is a suitable molecular marker for detection of pathogenic S. aureus.

Staphylococcus aureus Ventilator-Associated Pneumonia: A Study of Bacterio-Epidemiological Profile and Virulence Factors

Ventilator-associated pneumonia (VAP) represents a major cause of nosocomial infections in the intensive care units in which Staphylococcus aureus is frequently involved. Better knowledge of this pathogen is required in order to enhance the patient’s treatment and care. In this article, we studied the bacteriological profile and virulence factors of S. aureus-related VAP on a 3-year period. We included a collection of S. aureus strains (n = 35) isolated from respiratory samples from patients diagnosed with VAP in the intensive care units. We studied the bacteriological aspects and we searched for the presence of virulence factors (SpA, FnbpA, Hla, and PVL genes) in the strains, and we also studied the clinical and biological aspects of the infections. The average age of our patients was of 36 years and they were predominantly males (sex ratio = 3.37). A severe head trauma or a history of coma was noted in 73.43% of the patients. The average duration of ventilation was 29 days. Among the studied strains, five were Methicillin-resistant S. aureus of which three expressed the mecA gene. Overall, the Hla gene was detected in 85.7% of the strains and it was more prevalent in Methicillin-susceptible than Methicillin-resistant strains (93.3% versus 40%; P = 0.014). FnbpA, Spa, and PVL genes were detected, respectively, in 80%, 45.7%, and 20% of the strains. Therefore, our studied strains were essentially associated with the production of Hla and FnbpA genes. It is, however, important to elucidate their expression in order to establish their role in the VAP pathogenesis.

Novel strategies for rapid identification and susceptibility testing of MRSA

INTRODUCTION

Methicillin-resistant Staphylococcus aureus (MRSA) is associated with adverse clinical outcomes and increased morbidity, mortality, length of hospital stay, and health-care costs. Rapid diagnosis of MRSA infections has been associated with positive impact on clinical outcomes.

AREAS COVERED

We searched relevant papers in PubMed for the last 10 years. In major papers, we scanned the bibliographies to ensure that important articles were included. This review describes screening and diagnostic test methods for MRSA and their analytical performances with a focus on rapid molecular-based assays including those that are on the horizon. Future novel technologies will allow more rapid detection of phenotypic resistance. In the case of whole-genome sequencing, detection of mutations may predict resistance, transmission, and virulence.

EXPERT OPINION

Currently there are many diagnostic options for the detection of MRSA in surveillance and clinical samples. In general, these are highly accurate and have resulted in improvements in targeted management and reduction in hospital or intensive care unit length of stay for both MSSA and MRSA. Impact on mortality has been variable. Promising novel technologies will not only accurately identify pathogens and detect their resistance markers but will allow discovery of virulence determinants that might further affect patient management.

Daily practice and prognostic factors for pneumonia caused by methicillin-resistant Staphylococcus aureus in Japan: A multicenter prospective observational cohort study

Pneumonia caused by methicillin-resistant Staphylococcus aureus (MRSA) is associated with poor clinical outcomes. We surveyed clinical outcomes of MRSA pneumonia in daily practice to identify risk factors for the clinical failure and mortality in patients with MRSA pneumonia. This multicenter prospective observational study was performed across 48 Japanese medical institutions. Adult patients with culture-positive MRSA pneumonia were recruited and treated with anti-MRSA antibiotics. The relationships between clinical and microbiological characteristics and clinical outcomes at test of cure (TOC) or 30-day all-cause mortality were analyzed. In total, 199 eligible patients, including nursing and healthcare-associated pneumonia (n = 95), hospital-acquired pneumonia (n = 76), and community-acquired pneumonia (n = 25), received initial treatment with anti-MRSA agents such as vancomycin (n = 135), linezolid (n = 36), or teicoplanin (n = 22). Overall clinical failure rate at TOC and the 30-day mortality rate were 51.1% (48/94 patients) and 33.7% (66/196 patients), respectively. Multivariable logistic regression analyses for vancomycin-treated populations revealed that abnormal white blood cell count (odds ratio [OR] 4.34, 95% confidence interval [CI] 1.31-14.39) was a risk factor for clinical failure and that no therapeutic drug monitoring (OR 3.10, 95% CI 1.35-7.12) and abnormally high C-reactive protein level (OR 3.54, 95% CI 1.26-9.92) were risk factors for mortality. In conclusion, this study provides evidence that majority of MRSA pneumonia patients are initially treated with vancomycin in Japan, and the absence of therapeutic drug monitoring for vancomycin is significantly associated with the mortality in patients with MRSA pneumonia.

What Is the Evidence for Co-trimoxazole, Clindamycin, Doxycycline, and Minocycline in the Treatment of Methicillin-Resistant Staphylococcus aureus (MRSA) Pneumonia?

Objective: To review the evidence for trimethoprim-sulfamethoxazole (TMP-SMX), clindamycin, doxycycline, and minocycline in the treatment of methicillin-resistant Staphylococcus aureus (MRSA) pneumonia. Data Source: MEDLINE, PubMed, EMBASE, Google, Google Scholar, Cochrane Central Register of Controlled Trials from 1946 to May 20, 2019. The search was performed with the keywords methicillin-resistant Staphylococcus aureus, MRSA, Staphylococcus aureus, pneumonia, trimethoprim, sulfamethoxazole drug combination, trimethoprim, sulfamethoxazole, TMP-SMX, co-trimoxazole, clindamycin, doxycycline, and minocycline. Data Extraction: Studies reporting the use of the above antibiotics for MRSA pneumonia treatment with clinical outcomes were included. Search parameters were limited to English language and human studies only. Data Synthesis: The search yielded 16 relevant articles: 6 TMP-SMX, 8 clindamycin, zero doxycycline, and 2 minocycline. For TMP-SMX, prospective randomized trials showed variable results; however, these studies were not specifically designed to assess MRSA pneumonia treatment. Retrospective studies with clindamycin suggested that it could be used as monotherapy or in combination with other anti-MRSA antibiotics. There was no evidence for doxycycline use, but 2 small retrospective reviews appeared to support minocycline as a treatment option. Relevance to Patient Care and Clinical Practice: These antibiotics are often used in clinical practice as potential treatment options for MRSA pneumonia. This article reviews the evidence for the clinical efficacy and safety of these agents. Conclusions: There are limited data to support use of TMP-SMX, clindamycin, doxycycline, or minocycline in MRSA pneumonia treatment. Randomized controlled trials are required to determine the effectiveness of these antibiotics. Clinicians should base their decision to use these agents on a case-by-case basis depending on clinical status and susceptibility results.

A Comparison of Clinical Characteristics and Outcomes of Ventilator-Associated Pneumonias Among Burn Patients by Diagnostic Criteria Set

OBJECTIVES

The National Healthcare Safety Network (NHSN) replaced its old definition for ventilator-associated pneumonia (VAP) with ventilator-associated events (VAEs) in 2013. Little data is available comparing the two definitions in burn patients.

METHODS

Data from 2011 to 2014 were collected on burn patients mechanically ventilated for at least 2 days. VAP was determined using two methods: (1) pneumonia as defined by the previous more clinical CDC (NHSN) definition captured in the burn registry; (2) pneumonia as defined by the recent CDC (NHSN) standard of VAEs where patients meeting the criteria for possible VAP were considered having a pneumonia. Cohen kappa statistic was measured to compare both definitions, and chi-square and ANOVA to compare admission and clinical outcomes.

RESULTS

There were 266 burn patients who were mechanically ventilated for at least 2 days between 2011 and 2014. One hundred patients (37.5%) met the criteria by the old definition and 35 (13.1%) met the criteria for both. The kappa statistic was 0.34 (95% confidence interval 0.23-0.45), suggesting weak agreement. Those who met both definitions were mechanically ventilated for a longer period of time (P = 0.0003), and had a longer intensive care unit (ICU) length of stay (LOS) (P = 0.0004) and hospital LOS (P = 0.0014).

CONCLUSIONS

There is weak agreement between the two definitions of VAP in severely burn patients. However, patients who met both VAP definitions had longer ventilator days, ICU, and hospital stays.

Factors influencing severity of community-acquired pneumonia

INTRODUCTION

Community-acquired pneumonia (CAP) is a common cause of morbidity and mortality in India. There is a need to understand the risk factors associated with severity of CAP in our population. This study was part of the international global initiative for methicillin-resistant Staphylococcus aureus (MRSA) pneumonia study to evaluate MRSA.

METHODS

A total of 100 consecutive cases of pneumonia admitted to the Department of Pulmonary Medicine in a tertiary care hospital were recruited in the study during March-July 2015. The severity of pneumonia was assessed based on the CURB-65 score. Individuals with pneumonia and CURB-65 score >2 were compared with subjects with CURB-65 score ≤2. Individuals were also evaluated for the causative organism and its resistance pattern with specific reference to the presence of MRSA.

RESULTS

Mean age of patients was 54.03 years, 66% were men. Patients were managed either in the intensive care unit (42%) or wards/high dependency unit (58%), 22% needed noninvasive ventilation and 18% needed mechanical ventilation within 24 h of admission. On multivariate analysis, prior respiratory infection (within last 1 year), obesity (body mass index >30), and alcoholism, old age (>60 years) were independently associated risk factors for severe pneumonia. There were no cases of MRSA. In 34% of cases, organisms could be identified. Most common organisms were Klebsiella (8%), influenza (8%), and Pseudomonas (5%).

CONCLUSION

Prior respiratory infection, obesity, alcoholism, and old age (>60 years) were observed to be important risk factors for severe CAP. Prospective studies should evaluate effect of weight reduction and cessation of alcohol consumption on recurrences of pneumonia in this population and on the severity of pneumonia.

Estimating the burden of antimicrobial resistance: a systematic literature review

Background

Accurate estimates of the burden of antimicrobial resistance (AMR) are needed to establish the magnitude of this global threat in terms of both health and cost, and to paramaterise cost-effectiveness evaluations of interventions aiming to tackle the problem. This review aimed to establish the alternative methodologies used in estimating AMR burden in order to appraise the current evidence base.

Methods

MEDLINE, EMBASE, Scopus, EconLit, PubMed and grey literature were searched. English language studies evaluating the impact of AMR (from any microbe) on patient, payer/provider and economic burden published between January 2013 and December 2015 were included. Independent screening of title/abstracts followed by full texts was performed using pre-specified criteria. A study quality score (from zero to one) was derived using Newcastle-Ottawa and Philips checklists. Extracted study data were used to compare study method and resulting burden estimate, according to perspective. Monetary costs were converted into 2013 USD.

Results

Out of 5187 unique retrievals, 214 studies were included. One hundred eighty-seven studies estimated patient health, 75 studies estimated payer/provider and 11 studies estimated economic burden. 64% of included studies were single centre. The majority of studies estimating patient or provider/payer burden used regression techniques. 48% of studies estimating mortality burden found a significant impact from resistance, excess healthcare system costs ranged from non-significance to $1 billion per year, whilst economic burden ranged from $21,832 per case to over $3 trillion in GDP loss. Median quality scores (interquartile range) for patient, payer/provider and economic burden studies were 0.67 (0.56-0.67), 0.56 (0.46-0.67) and 0.53 (0.44-0.60) respectively.

Conclusions

This study highlights what methodological assumptions and biases can occur dependent on chosen outcome and perspective. Currently, there is considerable variability in burden estimates, which can lead in-turn to inaccurate intervention evaluations and poor policy/investment decisions. Future research should utilise the recommendations presented in this review.

Trial registration

This systematic review is registered with PROSPERO (PROSPERO CRD42016037510).

Burn patients with infection-related ventilator associated complications have worse outcomes compared to those without ventilator associated events

BACKGROUND

The Centers for Disease Control and Prevention (CDC) replaced its definition for ventilator-associated pneumonia (VAP) in 2013. The aim of the current study is to compare the outcome of burn patients with ventilator associated events (VAEs).

METHODS

Burn patients with at least two days of ventilator support were identified from the registry between 2013 and 2016. Kruskal-Wallis and Fisher's exact tests were utilized for continuous and categorical variables, respectively. A logistic regression was used for the association between VAE and in-hospital mortality.

RESULTS

243 patients were admitted to our burn center, of whom 208 had no VAE, 8 had a VAC, and 27 had an IVAC or PVAP. There was no difference in hospital length of stay, ICU length of stay and ventilator support days between those with no VAE and a VAC. Those with IVAC-plus had significantly worse outcomes compared to patients with no VAEs.

CONCLUSIONS

Burn patients with IVAC-plus had significantly longer hospital and ICU lengths of stay, days on ventilator compared with patients with no VAEs.

A Phase II Randomized, Double-blind, Multicenter Study to Evaluate Efficacy and Safety of Intravenous Iclaprim Versus Vancomycin for the Treatment of Nosocomial Pneumonia Suspected or Confirmed to be Due to Gram-positive Pathogens

PURPOSE

The primary objective of this Phase II study was to compare the clinical cure rates of 2 iclaprim dosages versus vancomycin in the treatment of patients with nosocomial pneumonia suspected or confirmed to be caused by gram-positive pathogens.

METHODS

This study was a double-blind, randomized, multicenter trial. A total of 70 patients were randomized 1:1:1 to receive iclaprim 0.8 mg/kg IV q12h (iclaprim q12h; n = 23), iclaprim 1.2 mg/kg IV q8h (iclaprim q8h; n = 24), or vancomycin 1 g IV q12h (vancomycin; n = 23) for 7 to 14 days. The primary end point was clinical cure in the intention-to-treat population at test of cure (TOC; 7 [1] days' posttreatment) visit.

FINDINGS

The baseline and demographic characteristics of patients treated with either iclaprim or vancomycin were comparable. Cure rates in the intention-to-treat population were 73.9% (17 of 23), 62.5% (15 of 24), and 52.2% (12 of 23) at the TOC visit in the iclaprim q12h, iclaprim q8h, and vancomycin groups, respectively (iclaprim q12h vs vancomycin, P = 0.13; iclaprim q8h vs vancomycin, P = 0.47). The death rates within 28 days of the start of treatment were 8.7% (2 of 23), 12.5% (3 of 24), and 21.7% (5 of 23) for the iclaprim q12h, iclaprim q8h, and vancomycin groups (no statistically significant differences). The adverse event profile of both iclaprim dosing regimens was similar to that of vancomycin.

IMPLICATIONS

Iclaprim had clinical cure rates and a safety profile comparable with vancomycin among patients with nosocomial pneumonia. Iclaprim could be an important new therapeutic option for the treatment of nosocomial pneumonia, and a pivotal clinical trial is warranted to evaluate its safety and efficacy in this indication.

Estimation of the incidence of MRSA patients: evaluation of a surveillance system using health insurance claim data

Because sentinel surveillance systems cannot obtain information about patients who visit non-sentinel medical facilities, the characteristics of patients identified by these systems may be biased. In this study, we evaluated the representativeness of a methicillin-resistant Staphylococcus aureus (MRSA) surveillance system using health insurance claim (HIC) data, which does not depend on physician notification. We calculated the age-specific incidence of MRSA patients using data from the Japan Nosocomial Infections Surveillance (JANIS) programme, which is based on sentinel surveillance systems, and inpatient HICs submitted to employee health insurance organizations in 2011, and then computed age-specific incidence ratios between the HIC and JANIS data. Age-specific MRSA incidence in both datasets followed J-shaped curves with similar shapes. For all age groups, the ratios between HIC and JANIS data were around 10. These findings indicate that JANIS notification of MRSA cases was not affected by patients’ age.

An update on the pharmacotherapeutic management of lower respiratory tract infections

INTRODUCTION

Our knowledge about lower respiratory tract infections (LRTIs) has improved substantially in the last years, but the management of respiratory infections is still a challenge and we are still far from using precision medicine in their treatment. Areas covered: The approaches developed in recent years to improve the pharmacotherapeutic management of LRTIs, such as novel diagnostic assays to facilitate medical decision-making, attempts for selecting an optimal empiric antibiotic regimen, and the role of new and possibly unproven adjunctive therapies, are described. Expert opinion: Early and appropriate antibiotics remain the cornerstone in the treatment of LRTIs. The updated trend is to apply antimicrobial stewardship principles and initiatives to optimize both the management and the outcomes of LTRIs. Biomarkers, mainly C-reactive protein (CRP) and procalcitonin (PCT), can improve the diagnostic and prognostic assessment of LRTIs and aid to guide antibiotic therapy. The widespread use of antimicrobial agents has greatly contributed to faster development of antibiotic resistance and the emergence of opportunistic pathogens, which substitute the indigenous microbiota. However, very few new antibiotics in development to overcome existing resistance and ensure continued success in the treatment of LRTIs have been approved, likely because antibiotic stewardship programs discourage the use of new agents.

Hospital Dissemination of tst-1-Positive Clonal Complex 5 (CC5) Methicillin-Resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA), is one of the most prevalent clinical pathogens isolated from hospital settings, and has increasingly identified in community settings. In China, the SCCmecIII-ST239 strains are disseminated in different geographic regions, accounting for >75% of all MRSA isolates in some national studies. Here we characterized 150 non-duplicate MRSA isolates collected from February 2012 to May 2013 in a tertiary hospital in Suzhou, Eastern China, to explore the molecular epidemiology. All isolates were characterized by spa typing, SCCmec typing, and detection of genes encoding Panton-Valentine leukocidin (PVL) and toxic shock syndrome toxin (TSST-1). Representative genotypes were also subjected to multilocus sequence typing (MLST). Antibiotic susceptibility testing was performed using BD Phoenix™ Automated Microbiology System. Molecular typing identified 11 clonal complex (CC) and 28 spa types, with the CC5-spa t002 (29.3%) and CC239-spa t037 (14.7%) being the most prevalent. SCCmec types II, III, IV, and V were identified in 33.3, 21.3, 23.3, and 21.3% of all isolates, respectively. PVL genes (lukF/S-PV) were detected in 11.3% of all isolates and from 6 CCs (5, 8, 59, 88, 239, and 398). The TSST-1 gene (tst) was detected in 18.0% of the all isolates, predominantly in CC5 (96.3%). All the tst-1-positve CC5 isolates were spa t002. Eighteen patients died within 30 days of hospitalization, and the in-hospital 30-day mortality was 12.0%. Multivariable analysis showed that 60 years old (odds ratio [OR] = 7.2, P = 0.026), cancer diagnosis (OR = 9.6, P = 0.022), and MRSA isolate carriage of tst-1 (OR = 62.5, P < 0.001) were independent factors associated with 30-day mortality. Our study revealed unique MRSA dissemination patterns in our hospital in comparison to those of other regions in China. The finding that tst-1-positive CC5 strains were associated with higher mortality highlights the need for strict infection control measures in order to prevent further spread of these strains in our hospital, as well as others.

Methicillin-Resistant Staphylococcus aureus Pneumonia in Critically Ill Trauma and Burn Patients: A Retrospective Cohort Study

BACKGROUND

The timing and risk factors for methicillin-resistant Staphylococcus aureus (MRSA) pneumonia in trauma patients are not well characterized. This information is critical for the selection of appropriate empiric antibiotics. The objective of this study was to determine the incidence of MRSA pneumonia in early-onset and late-onset pneumonia and to identify risk factors for MRSA in the trauma-burn intensive care unit (ICU).

PATIENTS AND METHODS

We conducted a retrospective cohort study from January 2012 to March 2015 of patients in the trauma and burn ICU with clinical and microbiologic evidence of pneumonia. Demographics, injury type and severity, co-morbidities, antimicrobial agents, and MRSA nasal colonization at ICU admission were extracted from the medical record. A multi-variable exact logistic regression was performed to assess predictors of MRSA pneumonia.

RESULTS

Eighty patients with 88 episodes of pneumonia were included in the cohort. Ten patients had MRSA pneumonia, an overall incidence of 11.4% of pneumonia episodes with a median onset of seven days. The proportion of MRSA pneumonia episodes was not significantly different in early-onset (<5 days) or late-onset pneumonia, and there were no statistically significant risk factors for developing MRSA pneumonia. The majority of patients with MRSA had at least one known risk factor including homelessness, substance abuse, and receipt of broad-spectrum antibiotic agents.

CONCLUSIONS

The 11.4% overall incidence of MRSA pneumonia in this trauma-burn cohort was similar to what has been reported in other trauma populations, although MRSA was equally likely to be identified in early- and late-onset pneumonia. Our results suggest that risk factors other than duration of hospitalization may be important considerations in the decision to initiate MRSA-active empiric therapy for pneumonia in the trauma-burn ICU.

Pharmacist-managed dose adjustment feedback using therapeutic drug monitoring of vancomycin was useful for patients with methicillin-resistant Staphylococcus aureus infections: a single institution experience

Background

Vancomycin (VCM) requires dose adjustment based on therapeutic drug monitoring. At Aomori Prefectural Central Hospital, physicians carried out VCM therapeutic drug monitoring based on their experience, because pharmacists did not participate in the dose adjustment. We evaluated the impact of an Antimicrobial Stewardship Program (ASP) on attaining target VCM trough concentrations and pharmacokinetics (PK)/pharmacodynamics (PD) parameters in patients with methicillin-resistant Staphylococcus aureus (MRSA) infections.

Materials and methods

The ASP was introduced in April 2012. We implemented a prospective audit of prescribed VCM dosages and provided feedback based on measured VCM trough concentrations. In a retrospective pre- and postcomparison study from April 2007 to December 2011 (preimplementation) and from April 2012 to December 2014 (postimplementation), 79 patients were treated for MRSA infection with VCM, and trough concentrations were monitored (pre, n=28; post, n=51). In 65 patients (pre, n=15; post, n=50), 24-hour area under the concentration–time curve (AUC 0–24 h)/minimum inhibitory concentration (MIC) ratios were calculated.

Results

Pharmacist feedback, which included recommendations for changing dose or using alternative anti-MRSA antibiotics, was highly accepted during postimplementation (88%, 29/33). The number of patients with serum VCM concentrations within the therapeutic range (10–20 μg/mL) was significantly higher during postimplementation (84%, 43/51) than during preimplementation (39%, 11/28) (P<0.01). The percentage of patients who attained target PK/PD parameters (AUC 0–24 h/MIC >400) was significantly higher during postimplementation (84%, 42/50) than during preimplementation (53%, 8/15; P=0.013). There were no significant differences in nephrotoxicity or mortality rate.

Conclusion

Our ASP increased the percentage of patients that attained optimal VCM trough concentrations and PK/PD parameters, which contributed to the appropriate use of VCM in patients with MRSA infections.

The safety and efficacy of high versus low vancomycin trough levels in the treatment of patients with infections caused by methicillin-resistant Staphylococcus aureus: a meta-analysis

BACKGROUND

Recent guidelines have recommended vancomycin trough levels of 15-20 mg/L for treatment of serious infections caused by methicillin-resistant Staphylococcus aureus (MRSA). However, high trough levels may increase risk of nephrotoxicity and mortality, and high vancomycin trough levels have not been well studied. This study was designed to combine safety and efficacy results from independent studies and to compare between high and low vancomycin trough levels in the treatment of MRSA-infected patients using meta-analysis.

METHODS

From 19 eligible studies, 9 studies were included in meta-analysis to compare clinical success between high and low vancomycin trough levels, while 10 and 11 studies met criteria for comparing trough levels and nephrotoxicity and trough levels and mortality, respectively. The PubMed/Medline, Web of Science, and Scopus databases, and hand searching were used to identify eligible studies dated up to March 2016. Of 2344 subjects with MRSA infection, 1036 were assigned to trough levels ≥15 mg/L and 1308 to trough levels <15 mg/L.

RESULTS

High vancomycin trough levels were found to be associated with risk of nephrotoxicity (odds ratio [OR] 2.14, 95 % confidence interval [CI] 1.42-3.23 and adjusted OR 3.33, 95 % CI 1.91-5.79). There was no evidence of difference between high and low vancomycin trough levels for mortality (OR; 1.09; 95 % CI 0.75-1.60) or clinical success (OR 1.07; 95 % CI 0.68-1.68).

CONCLUSION

In this study, high vancomycin trough levels were identified as an independent factor associated with risk of nephrotoxicity in MRSA-infected patients. Association between vancomycin trough levels and both adverse effects and clinical outcomes requires further study.

Staphylococcus aureus Community-acquired Pneumonia: Prevalence, Clinical Characteristics, and Outcomes

BACKGROUND

Prevalence of Staphylococcus aureus community-acquired pneumonia (CAP) and its clinical features remain incompletely understood, complicating empirical selection of antibiotics.

METHODS

Using a multicenter, prospective surveillance study of adults hospitalized with CAP, we calculated the prevalence of methicillin-resistant S. aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) among all CAP episodes. We compared the epidemiologic, radiographic, and clinical characteristics of S. aureus CAP (per respiratory or blood culture) with those of pneumococcal (per respiratory or blood culture or urine antigen) and all-cause non-S. aureus CAP using descriptive statistics.

RESULTS

Among 2259 adults hospitalized for CAP, 37 (1.6%) had S. aureus identified, including 15 (0.7%) with MRSA and 22 (1.0%) with MSSA; 115 (5.1%) had Streptococcus pneumoniae Vancomycin or linezolid was administered to 674 (29.8%) patients within the first 3 days of hospitalization. Chronic hemodialysis use was more common among patients with MRSA (20.0%) than pneumococcal (2.6%) and all-cause non-S. aureus (3.7%) CAP. Otherwise, clinical features at admission were similar, including concurrent influenza infection, hemoptysis, multilobar infiltrates, and prehospital antibiotics. Patients with MRSA CAP had more severe clinical outcomes than those with pneumococcal CAP, including intensive care unit admission (86.7% vs 34.8%) and in-patient mortality (13.3% vs 4.4%).

CONCLUSIONS

Despite very low prevalence of S. aureus and, specifically, MRSA, nearly one-third of adults hospitalized with CAP received anti-MRSA antibiotics. The clinical presentation of MRSA CAP overlapped substantially with pneumococcal CAP, highlighting the challenge of accurately targeting empirical anti-MRSA antibiotics with currently available clinical tools and the need for new diagnostic strategies.

Pneumonia Caused by Methicillin-Resistant Staphylococcus aureus: Does Vancomycin Heteroresistance Matter?

Vancomycin remains the mainstay treatment for methicillin-resistant Staphylococcus aureus (MRSA) infections, including pneumonia. There is concern regarding the emergence of vancomycin tolerance, caused by heterogeneous vancomycin-intermediate S. aureus (hVISA), and subsequent vancomycin treatment failure. Pneumonia is associated with high morbidity and mortality, especially with delays in appropriate therapy. This study evaluated the clinical outcomes of patients with hVISA pneumonia compared to those with vancomycin-susceptible S. aureus (VSSA) pneumonia. A retrospective cohort of patients with MRSA pneumonia from 2005 to 2014 was matched at a ratio of 2:1 VSSA to hVISA infections to compare patient characteristics, treatments, and outcomes. hVISA was determined by the 48-h population analysis profile area under the curve. Characteristics between VSSA and hVISA infections were compared by univariate analysis and multivariable logistic regression analysis to determine independent risk factors of inpatient mortality. Eighty-seven patients were included, representing 29 hVISA and 58 VSSA cases of pneumonia. There were no significant differences in demographics or baseline characteristics. Sequential organ failure assessment (SOFA) scores were a median of 7 (interquartile ratio [IQR], 5 to 8) in hVISA patients and 5 (IQR, 3 to 8) in VSSA (P = 0.092) patients. Inpatient mortality was significantly higher in hVISA patients (44.8% versus 24.1%; P = 0.049). Predictors of inpatient mortality upon multivariable regression were SOFA score (adjusted odds ratio [aOR], 1.36; 95% confidence interval [CI], 1.08 to 1.70), Panton-Valentine leukocidin (PVL) positivity (aOR, 6.63; 95% CI, 1.79 to 24.64), and hVISA phenotype (aOR, 3.95; 95% CI, 1.18 to 13.21). Patients with hVISA pneumonia experienced significantly higher inpatient mortality than those with VSSA pneumonia. There is a need to consider the presence of vancomycin heteroresistance in pneumonia caused by MRSA in order to potentially improve clinical outcomes.

Managing skin and soft-tissue infection and nosocomial pneumonia caused by MRSA: a 2014 follow-up survey

As a follow-up to our 2009 survey, in order to explore opinion and practice on the epidemiology and management of meticillin-resistant Staphylococcus aureus (MRSA) in Europe, we conducted a second survey to elicit current opinions on this topic, particularly around antibiotic choice, dose, duration and route of administration. We also aimed to further understand how the management of MRSA has evolved in Europe during the past 5 years. Members of an expert panel of infectious diseases specialists convened in London (UK) in January 2014 to identify and discuss key issues in the management of MRSA. Following this meeting, a survey was developed comprising 36 questions covering a wide range of topics on MRSA complicated skin and soft-tissue infection and nosocomial pneumonia management. The survey instrument, a web-based questionnaire, was sent to the International Society of Chemotherapy for distribution to registered European infection societies and their members. This article reports the survey results from the European respondents. At the time of the original survey, the epidemiology of MRSA varied significantly across Europe and there were differing views on best practice. The current findings suggest that the epidemiology of healthcare-associated MRSA in Europe is, if anything, even more polarised, whilst community-acquired MRSA has become much more common. However, there now appears to be a much greater knowledge of current treatment/management options, and antimicrobial stewardship has moved forward considerably in the 5 years since the last survey.

In Vitro Activity of Ceftaroline against Staphylococcus aureus Isolates Collected in 2012 from Latin American Countries as Part of the AWARE Surveillance Program

The in vitro activities of ceftaroline and comparators, using broth microdilution, were determined against 1,066 Staphylococcus aureus isolates from hospitalized patients. Seventeen medical centers from Latin American countries contributed isolates. Methicillin-resistant S. aureus (MRSA) percentages ranged from 46% (Brazil) to 62% (Argentina). All methicillin-susceptible S. aureus (MSSA) isolates were susceptible to ceftaroline. Ceftaroline activity against MRSA varied with MIC90s of 0.5 (Venezuela) to 2 (Brazil, Chile, and Colombia) μg/ml, which was the highest MIC value. ST-5 was the most common sequence type.

Roemerine Improves the Survival Rate of Septicemic BALB/c Mice by Increasing the Cell Membrane Permeability of Staphylococcus aureus

Staphylococcus aureus is one of the most frequently occurring hospital- and community-associated pathogenic bacteria featuring high morbidity and mortality. The occurrence of methicillin-resistant S. aureus (MRSA) has increased persistently over the years. Therefore, developing novel anti-MRSA drugs to circumvent drug resistance of S. aureus is highly important. Roemerine, an aporphine alkaloid, has previously been reported to exhibit antibacterial activity. The present study aimed to investigate whether roemerine can maintain these activities against S.aureus in vivo and further explore the underlying mechanism. We found that roemerine is effective in vitro against four S. aureus strains as well as in vivo against MRSA insepticemic BALB/c mice. Furthermore, roemerine was found to increase cell membrane permeability in a concentration-dependent manner. These findings suggest that roemerine may be developed as a promising compound for treating S. aureus, especially methicillin-resistant strains of these bacteria.

Predictors of prolonged stay in patients with community-acquired pneumonia and complicated parapneumonic effusion

BACKGROUND AND OBJECTIVE

Development of CPE in CAP is associated with prolonged hospital stay and it may increase the morbidity and mortality. We aimed to identify microbiological and clinical factors that predicate a prolonged hospital admission in patients treated with a tube thoracostomy to control CPE.

METHODS

This retrospective cohort included patients with CPE requiring chest tube drainage in a tertiary referral Korean hospital from 1 January 2004 to 30 July 2012. After dichotomous grouping according to the mean duration of hospital stay, clinical, laboratory and microbiological parameters were compared.

RESULTS

The final analysis included 158 patients with CPE. The majority were male (130, 85.0%), and the mean age was 62.8 years. The mean duration of hospital stay was 17.7 (±10.2) days. The mean duration of chest tube drainage was 9.6 (±6.7) days. Streptococcus viridans (48.4%) was the most common pathogen. Intrapleural fibrinolysis was performed in 85 (53.8%); additional tube insertion was needed in 40 (25.3%) patients. In the multivariate analysis after adjusting for covariates, a prolonged hospital stay was associated with fever (aOR: 3.42, P = 0.02), lower PaO2 (aOR: 4.89, P = 0.007) and haemoglobin (aOR: 4.90, P = 0.003) levels, and an increased blood neutrophil fraction (aOR: 3.83, P = 0.01) on admission as well as the identification of microbes in CPE (aOR: 4.14, P = 0.03), and ineffective pleural drainage (aOR: 3.28, P = 0.03).

CONCLUSIONS

This study suggests that physicians should note the clinical symptoms and laboratory findings of severe infection and effectiveness of pleural drainage to predicate which patients with a CAP needing thoracostomy for CPE will have a prolonged hospital stay.

Exaggerated Acute Lung Injury and Impaired Antibacterial Defenses During Staphylococcus aureus Infection in Rats with the Metabolic Syndrome

Rats with Metabolic Syndrome (MetaS) have a dysregulated immune response to the aseptic trauma of surgery. We hypothesized that rats with MetaS would have dysregulated inflammation, increased lung injury, and less effective antibacterial defenses during Staphylococcus (S.) aureus sepsis as compared to rats without MetaS. Low capacity runner (LCR; a model of MetaS) and high capacity runner (HCR) rats were challenged intravenously with S. aureus bacteria. After 48 h, inflammatory mediators and bacteria were quantified in the blood, bronchoalveolar lavage fluid (BALF), and lung homogenates. Lungs were analyzed histologically. BALF protein and lung wet-dry ratios were quantified to assess for vascular leak. Endpoints were compared in infected LCR vs HCR rats. LCR rats had higher blood and lung S. aureus counts, as well as higher levels of IL-6 in plasma, lungs and BALF, MIP-2 in plasma and lung, and IL-17A in lungs. Conversely, LCR rats had lower levels of IL-10 in plasma and lungs. Although lactate levels, and liver and renal function tests were similar between groups, LCR rats had higher BALF protein and lung wet-dry ratios, and more pronounced acute lung injury histologically. During S. aureus bacteremia, as compared with HCR rats, LCR (MetaS) rats have heightened pro-inflammatory responses, accompanied by increased acute lung injury and vascular leak. Notably, despite an augmented pro-inflammatory phenotype, LCR rats have higher bacterial levels in their blood and lungs. The MetaS state may exacerbate lung injury and vascular leak by attenuating the inflammation-resolving response, and by weakening antimicrobial defenses.

Community-acquired pneumonia

PURPOSE OF REVIEW

This review examines the epidemiology, diagnosis, prognosis, treatment and prevention of community-acquired pneumonia (CAP) in adults.

RECENT FINDINGS

CAP is a significant cause of morbidity and mortality. Streptococcus pneumoniae is the most common CAP pathogen; however, microbial cause varies by geographic location and host factors. Identification of a microbial cause in CAP remains challenging - 30-65% of cases do not have a pathogen isolated. The use of molecular techniques in addition to culture, serology and urinary antigen testing has improved diagnostic yield. Scoring systems are useful for CAP prognostication and site of care decisions. Studies evaluating novel biomarkers including pro-B-type natriuretic peptide and procalcitonin suggest potential adjunctive roles in CAP prognosis. Guideline-based treatment for CAP has changed little in recent years. Effective and timely antimicrobial therapy is crucial in optimizing outcomes and should be based on local antimicrobial susceptibility patterns. Macrolides may have additional anti-inflammatory properties and a mortality benefit in severe CAP. Preventive strategies include immunization and modification of specific patient risk factors.

SUMMARY

CAP is common and causes considerable morbidity and mortality. A comprehensive approach including advanced diagnostic testing, effective and timely antimicrobial therapy and prevention is required to optimize CAP outcomes.

Epidemiology of methicillin-resistant Staphylococcus aureus pneumonia in community hospitals

OBJECTIVE

Describe the epidemiology of healthcare-related (ie, healthcare-associated and hospital-acquired) pneumonia due to methicillin-resistant Staphylococcus aureus (MRSA) among hospitalized patients in community hospitals.

DESIGN

Retrospective cohort study.

SETTING

Twenty-four community hospitals in the southeastern United States affiliated with the Duke Infection Control Outreach Network (median size, 211 beds; range, 103-658 beds).

METHODS

Adult patients with healthcare-related MRSA pneumonia admitted to study hospitals from January 1, 2008, to December 31, 2012, were identified using surveillance data. Seasonal and annual incidence rates (cases per 100,000 patient-days) were estimated using generalized estimating equation models. Characteristics of community-onset and hospital-onset cases were compared.

RESULTS

A total of 1,048 cases of healthcare-related pneumonia due to MRSA were observed during 5,863,941 patient-days. The annual incidence rate of healthcare-related MRSA pneumonia increased from 11.3 cases per 100,000 patient-days (95% confidence interval [CI], 6.8-18.7) in 2008 to 15.5 cases per 100,000 patient-days (95% CI, 8.4-28.5) in 2012 (P = .055). The incidence rate was highest in winter months and lowest in summer months (15.4 vs 11.1 cases per 100,000 patient-days; incidence rate ratio, 1.39 [95% CI, 1.06-1.82]; P = .016). A total of 814 cases (77.7%) were community-onset healthcare-associated pneumonia cases; only 49 cases (4.7%) were ventilator-associated cases. Of 811 patients whose disposition was known, 240 (29.6%) died during hospitalization or were discharged to hospice.

CONCLUSIONS

From 2008 through 2012, the incidence of healthcare-related MRSA pneumonia among patients who were admitted to a large network of community hospitals increased, despite the decreasing incidence of invasive MRSA infections nationwide. Additional study is warranted to evaluate trends in this important and potentially modifiable public health problem.

Risk factors for mortality among patients with Staphylococcus aureus bacteremia: a single-centre retrospective cohort study

INTRODUCTION

Staphylococcus aureus bacteremia is associated with significant morbidity and mortality. Given the paucity of recent Canadian data, we estimated the mortality rate associated with S. aureus bacteremia in a tertiary care hospital and identified risk factors associated with mortality.

METHODS

We retrospectively reviewed the records of adults with S. aureus bacteremia admitted to a tertiary care centre in southwestern Ontario between 2008 and 2012. Cox regression analysis was used to evaluate associations between predictor variables and all-cause, in-hospital, and 90-day postdischarge mortality.

RESULTS

Of the 925 patients involved in the study, 196 (21.2%) died in hospital and 62 (6.7%) died within 90 days after discharge. Risk factors associated with in-hospital and all-cause mortality included age, sepsis (adjusted hazard ratio [adjusted HR] 1.49, 95% confidence interval [CI] 1.08-2.06, p = 0.02), admission to the intensive care unit (adjusted HR 3.78, 95% CI 2.85-5.02, p < 0.0001), hepatic failure (adjusted HR 3.36, 95% CI 1.91-5.90, p < 0.0001) and metastatic cancer (adjusted HR 2.58, 95% CI 1.77-3.75, p < 0.0001). Methicillin resistance, hepatic failure, cerebrovascular disease, chronic obstructive pulmonary disease and metastatic cancer were associated with postdischarge mortality.

INTERPRETATION

The all-cause mortality rate in our cohort was 27.9%. Identification of predictors of mortality may guide empiric therapy and provide prognostic clarity for patients with S. aureus bacteremia.

Emergence of carbapenem-resistant Acinetobacter baumannii as the major cause of ventilator-associated pneumonia in intensive care unit patients at an infectious disease hospital in southern Vietnam

Ventilator-associated pneumonia (VAP) is a serious healthcare-associated infection that affects up to 30 % of intubated and mechanically ventilated patients in intensive care units (ICUs) worldwide. The bacterial aetiology and corresponding antimicrobial susceptibility of VAP is highly variable, and can differ between countries, national provinces and even between different wards in the same hospital. We aimed to understand and document changes in the causative agents of VAP and their antimicrobial susceptibility profiles retrospectively over an 11 year period in a major infectious disease hospital in southern Vietnam. Our analysis outlined a significant shift from Pseudomonas aeruginosa to Acinetobacter spp. as the most prevalent bacteria isolated from quantitative tracheal aspirates in patients with VAP in this setting. Antimicrobial resistance was common across all bacterial species and we found a marked proportional annual increase in carbapenem-resistant Acinetobacter spp. over a 3 year period from 2008 (annual trend; odds ratio 1.656, P = 0.010). We further investigated the possible emergence of a carbapenem-resistant Acinetobacter baumannii clone by multiple-locus variable number tandem repeat analysis, finding a blaOXA-23-positive strain that was associated with an upsurge in the isolation of this pathogen. We additionally identified a single blaNDM-1-positive A. baumannii isolate. This work highlights the emergence of a carbapenem-resistant clone of A. baumannii and a worrying trend of antimicrobial resistance in the ICU of the Hospital for Tropical Diseases in Ho Chi Minh City, Vietnam.

Methicillin-resistant Staphylococcus aureus pneumonia in adults

Methicillin-resistant Staphylococcus aureus (MRSA) has become one of the leading etiologies of nosocomial pneumonia as a result of an increase in staphylococcal infections caused by methicillin-resistant strains paired with extended ventilatory support of critically, and often, chronically ill patients. The prevalence of community-acquired MRSA pneumonia, which historically affects younger patients and is often preceded by an influenza-like illness, is also increasing. A high index of suspicion and early initiation of appropriate antibiotics are key factors for the successful treatment of this disease. Even with early diagnosis and appropriate treatment, MRSA pneumonia still carries an unacceptably high mortality rate. This article will review historical differences between hospital-acquired and community-acquired MRSA pneumonia, as well as, clinical features of, diagnosis and treatment of MRSA pneumonia.

Panton-Valentine Leukocidin-positive Staphylococcus aureus: a potentially significant pathogen in cystic fibrosis

Staphylococcus aureus is an important pathogen within the context of cystic fibrosis lung disease. Case reports have identified a strong association between the toxin Panton-Valentine Leukocidin (PVL) and lethal necrotizing pneumonia in healthy immunocompetent patients. PVL+ strains of Staphylococcus aureus have also been identified in patients with cystic fibrosis. We describe a further case of pneumonia in a patient with cystic fibrosis, and outline potential transmission of the organism from healthy family members to this patient. We review the evidence regarding the pathogenicity of PVL toxin with a special reference to patients with cystic fibrosis. We outline current concerns regarding the potential transmission of the organism and possible treatment strategies.

HMGB1 as a drug target in staphylococcal pneumonia

High mobility group box (HMGB)1 is a small DNA-binding protein. In the nucleus, HMGB1 plays a role in gene expression and DNA replication. When it is released or secreted into the extracellular milieu, HMGB1 functions as a pro-inflammatory cytokine-like mediator. Recently reported data support the view that treatment with a neutralizing anti-HMGB1 antibody ameliorated pulmonary damage in a murine model of pneumonia caused by a pathogenic strain of Staphylococcus aureus. These findings suggest that HMGB1 may be an important drug target as scientists, clinical investigators and pharmaceutical companies seek to develop better agents for the treatment of staphylococcal pneumonia. Unfortunately, however, encouraging results from murine models of human disease often fail to translate into positive findings in clinical trials. Thus, before moving from pre-clinical into clinical studies, it may be prudent to validate and extend the recent experimental findings by carrying out additional studies, using a large animal model of pneumonia.

The changing microbiologic epidemiology of community-acquired pneumonia

Community-acquired pneumonia (CAP) is a common infectious disease in the United States and the incidence continues to grow as the aging population increases. Overall, in-hospital patient mortality rates have been reported to be as high as 18%. Management of patients with CAP has been challenged by the evolution of resistant pathogens (particularly Streptococcus pneumoniae and Staphylococcus aureus) that have reduced susceptibility to recommended standard antimicrobial agents. Streptococcus pneumoniae continues to be the most frequently identified pathogen in CAP and recently, S. aureus has been found to be the second most often identified pathogen. Data from the SENTRY Antimicrobial Surveillance Program has shown declining susceptibility of pneumococci to penicillin, amoxicillin/clavulanate, and ceftriaxone from 1998 through 2011. In the Assessing Worldwide Resistance Evaluation (AWARE) surveillance program, > 50% of all S. aureus isolates from patient bloodstream infections, skin and skin structure infections, and pneumonia were methicillin-resistant. Stratifying risk factors to identify patients at risk for community-acquired multidrug-resistant pathogens should be considered when selecting therapy. Differences in microbiology and outcomes have been noted in patients presenting from the community with recent exposure to the health care system (eg, nursing home residents, patients with a recent hospital admission). These patients are at an increased risk of an infection caused by a multidrug-resistant pathogen. Understanding a patient's risk for drug-resistant pathogens will allow the physician to choose an appropriate empiric treatment regimen to optimize clinical outcomes.