The epidemiology of ventilator-associated pneumonia in a network of community hospitals: a prospective multicenter study

A Study on the Epidemiological-Molecular Role of Staphylococcus aureus Strains in the Development of Ventilator-Associated Pneumonia in a Tertiary Hospital in Brazil

This study aimed to explore the molecular epidemiology of Staphylococcus aureus isolated from patients on mechanical ventilation and the participation of virulence factors in the development of ventilator-associated pneumonia (VAP). A prospective cohort study was conducted on patients under mechanical ventilation, with periodic visits for the collection of tracheal aspirates and clinical data. The S. aureus isolates were analyzed regarding resistance profile, virulence, expression of protein A and alpha-toxin using Western blot, clonal profile using PFGE, sequence type using MLST, and characterization and quantification of phenol-soluble modulins. Among the 270 patients in the study, 51 S. aureus strains were isolated from 47 patients. The incidence density of S. aureus and MRSA VAP was 2.35/1000 and 1.96/1000 ventilator days, respectively; of these, 45% (n = 5) were resistant to oxacillin, with 100% (n = 5) harboring SCCmec types II and IV. The most frequent among the tested virulence factors were icaA, hla, and hld. The clonal profile showed a predominance of sequence types originating from the community. Risk factors for VAP were the presence of solid tumors and the sea gene. In conclusion, patient-related risk factors, together with microbiological factors, are involved in the development of S. aureus VAP, which is caused by the patient's own strains.

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.

Trends and Factors Associated With Ventilator-Associated Pneumonia: A National Perspective

Background: Ventilator-associated pneumonia (VAP) is a hospital-acquired pneumonia that occurs more than 48 hours after mechanical ventilation. Studies showing temporal trends, predictors, and outcomes of VAP are very limited.

Objective: We used the National database to delineate the trends and predictors of VAP from 2009 to 2017.

Methods: We analyzed data from the Nationwide Inpatient Sample (NIS) for adult hospitalizations who received mechanical ventilation (MV) by using ICD-9/10-CM procedures codes. We excluded hospitalizations with length of stay (LOS) less than two days. VAP and other diagnoses of interest were identified by ICD-9/10-CM diagnosis codes. We then utilized the Cochran Armitage trend test and multivariate survey logistic regression models to analyze the data.

Results: Out of a total of 5,155,068 hospitalizations who received mechanical ventilation, 93,432 (1.81%) developed VAP. Incidence of VAP decreased from 20/1000 in 2008 to 17/1000 in 2017 with a 5% decrease. Patients who developed VAP had lower mean age (59 vs 61; p<0.001) and higher LOS (25 days vs. 12 days; p<0.001). In multivariable regression analysis, we identified that males, African Americans, teaching hospitals and co-morbidities like neurological disorders, pulmonary circulation disorders and electrolyte disorders are associated with the increased odds of developing VAP. VAP was also associated with higher rates of discharge to facilities and increased LOS.

Conclusion: Our study identified the trends along with the risk predictors of VAP in MV patients. Our goal is to lay the foundation for further in-depth analysis of this trend for better risk stratification and development of preventive strategies to reduce the incidence of VAP among MV patients.

Sputum susceptibilities in a nationwide veteran cohort

BACKGROUND

Respiratory infections are one of the most common causes of morbidity and mortality. This study examined antimicrobial susceptibility of common respiratory isolates from veterans.

METHODS

Sputum culture data from the Veteran Health Administration were obtained retrospectively between January 2009 and 2019. Cumulative antibiograms were constructed for bacterial isolate susceptibility.

RESULTS

Sputum and bronchial cultures from approximately 10,345 veterans were included each year. Haemophilus influenzae has maintained high levels of susceptibility to third generation cephalosporins from 2009 (99.7%) to 2018 (97.2%). Third generation cephalosporin susceptibilities amongst Klebsiella pneumoniae have trended upward from 2009 to 2018 as well (79.1% vs 86.4%). In Pseudomonas aeruginosa isolates, there has been an increase in susceptibility rates to cefepime from 2009 to 2018 (79.6%, to 86.6%), gentamicin (81.5% to 89.1%), and piperacillin/tazobactam (86.5% to 90%). Fluoroquinolone susceptibilities amongst Escherichia coli have remained low but stable between 2009 and 2018. Third generation cephalosporin susceptibilities for S. pneumoniae improved slightly from 92.2% to 95% between 2009 and 2018 while susceptibility to azithromycin trended down slightly from 56.8% in 2009 to 51.7% in 2018 for S. pneumoniae.

DISCUSSION

The antibiogram of sputum isolates from the VA Healthcare System were examined to determine changes in patterns of resistance over a decade of use.

CONCLUSIONS

This large-scale study investigated nationwide sputum culture susceptibility trends. Avoidance of macrolides for empiric treatment of community acquired pneumonia and avoidance of fluoroquinolones for empiric treatment of hospital acquired or ventilator associated pneumonia may be warranted based on susceptibility trends.

The effectiveness of Salvadora persica stick on the colonization of oral pathogens in mechanically ventilated patients in the intensive care unit (ICU): A pilot study

OBJECTIVE

To evaluate the effectiveness of antibacterial Salvadora persica stick on the colonization of oral pathogens in patients with mechanical ventilation.

METHOD

This research is quasi-experimental research with pre-test-post-test design. Oral care was administered every 12h on patients who required mechanical ventilation for less than 24h. The colonization of oral pathogen assessment was conducted with swab oral treatment before and 48h after mechanical ventilation. The data obtained were analyzed with a paired t-test.

RESULTS

The results of this research showed that the antibacterial effect of S. persica stick was significant in preventing the increase in the amount of oral pathogen colonization in mechanically ventilated patients (p<0.05). The colonization of oral pathogens decreased from 48×10⁶CFU/ml to 14×10⁶CFU/ml.

CONCLUSION

Oral care with S. persica can serve as a complementary therapy for patients with mechanical ventilation.

Automated Near Real-Time Ventilator Data Feedback Reduces Incidence of Ventilator-Associated Events: A Retrospective Observational Study

Objectives:

Critical care teams are encouraged to follow best practice protocols to help wean mechanically ventilated patients from the ventilator to reduce ventilator-associated events including ventilator-associated conditions, probable ventilator-associated pneumonias, and infection-related ventilator-associated conditions. Providers monitor for alerts suggestive of possible ventilator-associated events and advise when patients should undergo spontaneous breathing trials. Compliance with protocols in most units is suboptimal.

Design:

Retrospective review of clinical data over 24 months.

Setting:

St. Joseph Mercy Hospital Candler Hospital Medical-Surgical ICU.

Patients:

All mechanically ventilated patients.

Interventions:

The Respiratory Knowledge Portal was implemented in our ICU. For 13 months, Respiratory Knowledge Portal data were ported to ICU workstations (control). For the following 11 months, Respiratory Knowledge Portal data were also presented on tablet computers (intervention) for use during multidisciplinary rounds. We performed a retrospective review of Respiratory Knowledge Portal data from before and after the implementation of the tablet computers.

Measurements and Main Results:

Data were collected from 337 patients (187 control group, 150 intervention group). A decrease in the occurrence of ventilator-associated events was observed during the intervention group compared with the control group. Only 2.0% of patients in the intervention group experienced any category of ventilator-associated event, while 11.2% of patients in the control group experienced one event (p = 0.003). Intervention patients experienced less ventilator-associated conditions (p = 0.002), infection-related ventilator-associated conditions (p = 0.026), and probable ventilator-associated pneumonias (p = 0.036) than control patients. Twenty-one of the 24 patients with any ventilator-associated events were in the control group. There was no significant difference between the days spent on ventilation nor hospital length of stay in the control compared with intervention group patients.

Conclusions:

Fewer ventilator-associated events, ventilator-associated conditions, infection-related ventilator-associated conditions, and probable ventilator-associated pneumonias were seen during the period when Respiratory Knowledge Portal monitoring data was presented on tablet computers. There was no difference in time on ventilator nor overall length of stay.

Identification of Streptococcus pneumoniae in hospital-acquired pneumonia in adults

Hospital-acquired pneumonia (HAP) is often more severe and life-threatening than community-acquired pneumonia (CAP). The role of Streptococcus pneumoniae in CAP is well-understood, but its role in HAP is unclear. The objective of this study was to summarize the available literature on the prevalence of S. pneumoniae in HAP episodes. We searched MEDLINE for peer-reviewed articles on the microbiology of HAP in individuals aged ≥18 years, published between 2008 and 2018. We calculated pooled estimates of the prevalence of S. pneumoniae in episodes of HAP using a random-effects, inverse-variance-weighted meta-analysis. Forty-seven of 1908 articles met the inclusion criteria. Bacterial specimen isolation techniques for microbiologically defined HAP episodes included bronchoalveolar lavage, protective specimen brush, tracheobronchial aspirate and sputum, as well as blood culture. Culture was performed in all studies; five studies also used urine antigen detection (5/47; 10.6%). S. pneumoniae was identified in 5.1% (95% confidence interval (CI): 3.8-6.6%) of microbiologically defined HAP episodes (N = 20), with 5.4% (95% CI: 4.3-6.7%, N = 29) in ventilator-associated HAP and 6.0% (95% CI: 4.1-8.8%, N = 6) in non-ventilator-associated HAP. S. pneumoniae was identified in 5.3% (95% CI: 4.5-6.3%) of HAP occurring in the intensive care unit (ICU, N = 41) and in 5.6% (95% CI: 3.3-9.5%, N = 5) outside the ICU. A higher proportion of early-onset HAP (10.3%; 95% CI: 8.3-12.8%, N = 16) identified S. pneumoniae as compared with late-onset HAP (3.3%; 95% CI: 2.5-4.4%, N = 16). In conclusion, S. pneumoniae was identified by culture in 5.1% of microbiologically defined HAP episodes. The importance of HAP as part of the disease burden caused by S. pneumoniae merits further research.

Dissemination of VIM-producing Pseudomonas aeruginosa associated with high-risk clone ST654 in a tertiary and quaternary hospital in Makkah, Saudi Arabia

To the best of our knowledge, no molecular surveillance that has been conducted to identify the most common clones of carbapenem-resistant Pseudomonas aeruginosa (CRPA) in western Saudi Arabia. Therefore, this study aimed to identify genetic diversity and the most common CRPA clones in this region. Thirty-five CRPA isolates were collected from a tertiary and quaternary hospital in Makkah. bla _VIM was the most common carbapenemase-encoding gene (11 CRPA isolates), while bla_GES was reported in only three isolates. CRPA isolates were subjected to multi- locus sequence typing and showed relatively high genetic diversity with 20 sequence types. Approximately one-third (31.4%) of the CRPA isolates belonged to two high-risk clones (ST235 and ST654). This troublesome finding raises serious concerns about the emergence and further dissemination of CRPA high-risk clones in local hospitals and suggest that surveillance programs should be established in this region to monitor and control clonal dissemination of all multidrug resistant bacteria, including CRPA.

Staphylococcus aureus Nasal Carriage and Autoimmune Diseases: From Pathogenic Mechanisms to Disease Susceptibility and Phenotype

The role of infective agents in autoimmune diseases (ADs) development has been historically investigated, but in the last years has been strongly reconsidered due to the interest in the link between the microbiome and ADs. Together with the gut, the skin microbiome is characterized by the presence of several microorganisms, potentially influencing innate and adaptive immune response. S. aureus is one of the most important components of the skin microbiome that can colonize anterior nares without clinical manifestations. Data from the literature demonstrates a significantly higher prevalence of nasal colonization in ADs patients in comparison with healthy subjects, suggesting a possible role in terms of disease development and phenotypes. Thus, in the present narrative review we focused on the mechanisms by which S. aureus could influence the immune response and on its relationship with ADs, in particular granulomatosis with polyangiitis, rheumatoid arthritis, and systemic lupus erythematosus.

The utility of endotracheal aspirate bacteriology in identifying mechanically ventilated patients at risk for ventilator associated pneumonia: a single-center prospective observational study

Background

Ventilator-associated pneumonia (VAP) is a well-known, life-threatening disease that persists despite preventative measures and approved antibiotic therapies. This prospective observational study investigated bacterial airway colonization, and whether its detection and quantification in the endotracheal aspirate (ETA) is useful for identifying mechanically ventilated ICU patients who are at risk of developing VAP.

Methods

240 patients admitted to 3 ICUs at the Lahey Hospital and Medical Center (Burlington, MA) between June 2014 and June 2015 and mechanically ventilated for > 2 days were included. ETA samples and clinical data were collected. Airway colonization was assessed, and subsequently categorized into “heavy” and “light” by semi-quantitative microbiological analysis of ETAs. VAP was diagnosed retrospectively by the study sponsor according to a pre-specified pneumonia definition.

Results

Pathogenic bacteria were isolated from ETAs of 125 patients. The most common species isolated was S. aureus (56.8%), followed by K. pneumoniae, P. aeruginosa, and E. coli (35.2% combined). VAP was diagnosed in 85 patients, 44 (51.7%) with no bacterial pathogen, 18 associated with S. aureus and 18 Gram-negative-only cases, and 5 associated with other Gram-positive or mixed species. A higher proportion of patients who were heavily colonized with S. aureus developed VAP (32.4%) associated with S. aureus compared to those lightly colonized (17.6%). The same tendency was seen for patients heavily and lightly colonized with Gram-negative pathogens (30.0 and 0.0%, respectively). Detection of S. aureus in the ETA preceded S. aureus VAP by approximately 4 days, while Gram-negative organisms were first detected 2.5 days prior to Gram-negative VAP. VAP was associated with significantly longer duration of mechanical ventilation and hospitalization regardless of microbiologic cause when compared to patients who did not develop VAP.

Conclusions

The overall VAP rate was 35%. Heavy tracheal colonization supported identification of patients at higher risk of developing a corresponding S. aureus or Gram-negative VAP. Detection of bacterial ETA-positivity tended to precede VAP.

Electronic supplementary material

The online version of this article (10.1186/s12879-019-4367-7) contains supplementary material, which is available to authorized users.

Trimetoprim-sulfametoxazole in ventilator-associated pneumonia: a cohort study

To evaluate the effectiveness of trimetoprim-sulfametoxazole (TMP-SMX) for treatment of ventilator-associated pneumonia (VAP). A retrospective cohort study including patients with VAP from 2011 to 2017. Two groups were analysed: TMP-SMX group, including patients who had received TMP-SMX (as first-line and as de-escalation), and No-TMP-SMX group, including patients who had not received TMP-SMX treatment. Primary clinical outcome was mortality at 30 days from starting the antibiotic treatment (T30). Secondary outcomes were mortality at end of treatment (EoT), day survival at T30, and acquisition of multidrug-resistant bacteria during hospitalization in intensive care unit. Eighty cases of VAP were included and devised into two groups: No-TMP-SMX (31/80; 39%) and TMP-SMX (49/80; 61%). Univariate analysis showed no significant differences were found when the TMP-SMX group was compared with the No-TMP-SMX group, except for frequency of male gender (p = 0.025). No significant statistical correlations between mortality at T30 and individual factors were detected by the multivariate model. No cases of either severe allergy or Clostridium difficile disease were reported in the TMP-SMX and No-TMP-SMX groups. TMP-SMX treatment was not associated with higher mortality at EoT and T30 in comparison with the No-TMP-SMX group. TMP-SMX had a good safety profile, in terms of ecology (acquisition of MDR bacteria and Clostridium difficile disease) and clinical management (no allergy events).

Drug Prevention and Control of Ventilator-Associated Pneumonia

Ventilator-associated pneumonia (VAP) is one of the most prevalent and serious complications of mechanical ventilation, which is considered a common nosocomial infection in critically ill patients. There are some great options for the prevention of VAP: (i) minimize ventilator exposure; (ii) intensive oral care; (iii) aspiration of subglottic secretions; (iv) maintain optimal positioning and encourage mobility; and (v) prophylactic probiotics. Furthermore, clinical management of VAP depends on appropriate antimicrobial therapy, which needs to be selected based on individual patient factors, such as previous antibacterial therapy, history of hospitalization or mechanical ventilation, and bacterial pathogens and antibiotic resistance patterns. In fact, antibiotic resistance has exponentially increased over the last decade, and the isolation of a multidrug-resistant (MDR) pathogen has been identified as an independent predictor of inadequate initial antibiotic therapy and which is significantly associated with increased mortality. Multiple attempts were used in the treatment of VAP, such as novel antibacterial agents, inhaled antibiotics and monoclonal antibodies. In this review, we summarize the current therapeutic options for the prevention and treatment of VAP, aiming to better management of VAP in clinical practice.

Identification of carbapenem-resistant Pseudomonas aeruginosa in selected hospitals of the Gulf Cooperation Council States: dominance of high-risk clones in the region

PURPOSE

The molecular epidemiology and resistance mechanisms of carbapenem-resistant Pseudomonas aeruginosa (CRPA) were determined in hospitals in the countries of the Gulf Cooperation Council (GCC), namely, Saudi Arabia, the United Arab Emirates, Oman, Qatar, Bahrain and Kuwait.

METHODOLOGY

Isolates were screened for common carbapenem-resistance genes by PCR. Relatedness between isolates was assessed using previously described genotyping methods: an informative-single nucleotide polymorphism MassARRAY iPLEX assay (iPLEX20SNP) and the enterobacterial repetitive intergenic consensus (ERIC)-PCR assay, with selected isolates being subjected to multilocus sequence typing (MLST). Ninety-five non-repetitive isolates that were found to be resistant to carbapenems were subjected to further investigation.Results/Key findings. The most prevalent carbapenemase-encoding gene, blaVIM-type, was found in 37/95 (39 %) isolates, while only 1 isolate (from UAE) was found to have blaIMP-type. None of the CRPA were found to have blaNDM-type or blaKPC-type. We found a total of 14 sequence type (ST) clusters, with 4 of these clusters being observed in more than 1 country. Several clusters belonged to the previously recognized internationally disseminated high-risk clones ST357, ST235, ST111, ST233 and ST654. We also found the less predominant ST316, ST308 and ST823 clones, and novel MLST types (ST2010, ST2011, ST2012 and ST2013), in our collection.

CONCLUSION

Overall our data show that 'high-risk' CRPA clones are now detected in the region and highlight the need for strategies to limit further spread of such organisms, including enhanced surveillance, infection control precautions and further promotion of antibiotic stewardship programmes.

World-Wide Variation in Incidence of Staphylococcus aureus Associated Ventilator-Associated Pneumonia: A Meta-Regression

Staphylococcus aureus (S. aureus) is a common Ventilator-Associated Pneumonia (VAP) isolate. The objective here is to define the extent and possible reasons for geographic variation in the incidences of S. aureus-associated VAP, MRSA-VAP and overall VAP. A meta-regression model of S. aureus-associated VAP incidence per 1000 Mechanical Ventilation Days (MVD) was undertaken using random effects methods among publications obtained from a search of the English language literature. This model incorporated group level factors such as admission to a trauma ICU, year of publication and use of bronchoscopic sampling towards VAP diagnosis. The search identified 133 publications from seven worldwide regions published over three decades. The summary S. aureus-associated VAP incidence was 4.5 (3.9–5.3) per 1000 MVD. The highest S. aureus-associated VAP incidence is amongst reports from the Mediterranean (mean; 95% confidence interval; 6.1; 4.1–8.5) versus that from Asian ICUs (2.1; 1.5–3.0). The incidence of S. aureus-associated VAP varies by up to three-fold (for the lowest versus highest incidence) among seven geographic regions worldwide, whereas the incidence of VAP varies by less than two-fold. Admission to a trauma unit is the most important group level correlate for S. aureus-associated VAP.

Antibody-Antibiotic Conjugates: A Novel Therapeutic Platform against Bacterial Infections

Antibodies are potent components of the immune repertoire and have been successfully exploited to treat bacterial infections. Recently an antibody-antibiotic conjugate (AAC) that combines key attributes of an antibody and antibiotic has been shown to be efficacious against Staphylococcus aureus infection. An AAC has three components: an antibiotic payload to kill bacteria, an antibody to target delivery of the payload to bacteria, and a linker attaching the payload to the antibody. With increasing understanding of the biology and pathophysiology of S. aureus, this article highlights how this knowledge has led to the design principles of an efficacious AAC, and discusses how the AAC platform could be translationally applied to treat other perilous infectious diseases.

SIRT1‑mediated regulation of oxidative stress induced by Pseudomonas aeruginosa lipopolysaccharides in human alveolar epithelial cells

Sirtuin1 (SIRT1) is an NAD+‑dependent deacetylase that exhibits multiple biological functions, including cell differentiation inhibition, transcription regulation, cell cycle regulation and anti‑apoptosis. Lipopolysaccharides (LPS) are crucial virulence factors produced by Pseudomonas aeruginosa and serve an important role in adjusting the interactions between the host and the pathogen. However, the effect of SIRT1 in the regulation of LPS‑induced A459 human alveolar epithelial cells (AECs) oxidative stress remains unclear. The cellular reactive oxygen species (ROS) production was examined in A549 cells that were supplemented with LPS. Relative cell signaling pathway proteins were further investigated by western blot analysis. It was identified that LPS downregulated SIRT1 expression, however, upregulated ROS generation, which was associated with the increase of nuclear factor (NF)‑κB and acetyl‑NF‑κB. Activation of SIRT1 by resveratrol significantly reversed the effects of LPS on A549 cells. By contrast, inhibition of SIRT1 by nicotinamide had the opposite effects that enhance cell ROS production. Thus, the results indicated that SIRT1 serves an important role in the regulation of oxidative stress induced by LPS in human AECs.

Klebsiella pneumoniae: Going on the Offense with a Strong Defense

Klebsiella pneumoniae causes a wide range of infections, including pneumonias, urinary tract infections, bacteremias, and liver abscesses. Historically, K. pneumoniae has caused serious infection primarily in immunocompromised individuals, but the recent emergence and spread of hypervirulent strains have broadened the number of people susceptible to infections to include those who are healthy and immunosufficient. Furthermore, K. pneumoniae strains have become increasingly resistant to antibiotics, rendering infection by these strains very challenging to treat. The emergence of hypervirulent and antibiotic-resistant strains has driven a number of recent studies. Work has described the worldwide spread of one drug-resistant strain and a host defense axis, interleukin-17 (IL-17), that is important for controlling infection. Four factors, capsule, lipopolysaccharide, fimbriae, and siderophores, have been well studied and are important for virulence in at least one infection model. Several other factors have been less well characterized but are also important in at least one infection model. However, there is a significant amount of heterogeneity in K. pneumoniae strains, and not every factor plays the same critical role in all virulent Klebsiella strains. Recent studies have identified additional K. pneumoniae virulence factors and led to more insights about factors important for the growth of this pathogen at a variety of tissue sites. Many of these genes encode proteins that function in metabolism and the regulation of transcription. However, much work is left to be done in characterizing these newly discovered factors, understanding how infections differ between healthy and immunocompromised patients, and identifying attractive bacterial or host targets for treating these infections.

Staphylococcus aureus: the current state of disease, pathophysiology and strategies for prevention

Staphylococcus aureus is both a commensal organism and also an important opportunistic human pathogen, causing a variety of community and hospital-associated pathologies, such as bacteremia-sepsis, endocarditis, pneumonia, osteomyelitis, arthritis and skin diseases. The resurgence of S. aureus during the last decade in many settings has been facilitated not only by bacterial antibiotic resistance mechanisms but also by the emergence of new S. aureus clonal types with increased expression of virulence factors and the capacity to neutralize the host immune response. Prevention of the spread of S. aureus infection relies on the use of contact precautions and adequate procedures for infection control that so far have not been fully effective. Prevention using a prophylactic vaccine would complement these processes, having the potential to bring additional, significant progress toward decreasing invasive disease due to S. aureus.

Mechanical Ventilation and Clinical Outcomes in Patients with Acute Myocardial Infarction: A Retrospective Observational Study

Purpose

Patients with acute myocardial infarction (AMI) and respiratory impairment may be treated with either invasive or non-invasive mechanical ventilation (MV). However, there has been little testing of non-invasive MV in the setting of AMI. Our objective was to evaluate the incidence and associated clinical outcomes of patients with AMI who were treated with non-invasive or invasive MV.

Methods

This was a retrospective observational study in which consecutive patients with AMI (n = 1610) were enrolled. The association between exclusively non-invasive MV, invasive MV and outcomes was assessed by multivariable models.

Results

Mechanical ventilation was used in 293 patients (54% invasive and 46% exclusively non-invasive). In-hospital mortality rates for patients without MV, with exclusively non-invasive MV, and with invasive MV were 4.0%, 8.8%, and 39.5%, respectively (P<0.001). The median lengths of hospital stay were 6 (5.8–6.2), 13 (11.2–4.7), and 28 (18.0–37.9) days, respectively (P<0.001). Exclusively non-invasive MV was not associated with in-hospital death (adjusted HR = 0.90, 95% CI 0.40–1.99, P = 0.79). Invasive MV was strongly associated with a higher risk of in-hospital death (adjusted HR = 3.07, 95% CI 1.79–5.26, P<0.001).

Conclusions

In AMI setting, 18% of the patients required MV. Almost half of these patients were treated with exclusively non-invasive strategies with a favorable prognosis, while patients who needed to be treated invasively had a three-fold increase in the risk of death. Future prospective randomized trials are needed to compare the effectiveness of invasive and non-invasive MV for the initial approach of respiratory failure in AMI patients.

Antibacterial activity of achievable epithelial lining fluid exposures of Amikacin Inhale with or without meropenem

OBJECTIVES

While Amikacin Inhale (BAY41-6551), an integrated drug-device combination under development, achieves an estimated amikacin epithelial lining fluid (ELF) concentration of ∼ 5000 mg/L, its target site pharmacodynamics are unknown. We evaluated the pharmacodynamics of ELF exposure of inhaled amikacin ± meropenem.

METHODS

ELF exposures of inhaled amikacin (400 mg every 12 h), intravenous meropenem (2 g every 8 h) and a combination of both were studied in an in vitro pharmacodynamic model. Seven Klebsiella pneumoniae and 10 Pseudomonas aeruginosa with amikacin/meropenem MICs of 1 to 32,768/≤ 0.125 to >128 mg/L were included. Efficacy was assessed over 24-72 h.

RESULTS

The mean ± SD 0 h bacterial density was 6.5 ± 0.1 log10 cfu/mL. Controls grew to 8.0 ± 0.5 log10 cfu/mL by the end of the experiments. Simulation of inhaled amikacin monotherapy rapidly achieved and sustained bactericidal activity near the limit of detection over 24 h for all 13 isolates with amikacin MIC ≤ 256 mg/L except only ∼ 2 log10 cfu/mL reduction was observed in K. pneumoniae 375 (amikacin/meropenem MIC 64/32 mg/L) and P. aeruginosa 1544 (amikacin/meropenem MIC 64/128 mg/L). No activity was seen against the three isolates with amikacin MIC ≥ 2048 mg/L. Among the six isolates tested with meropenem monotherapy, five (meropenem MIC ≥ 16 mg/L) grew similarly to the controls while one (meropenem MIC 2 mg/L) achieved ∼ 2.5 log10 cfu/mL decrease. Among seven isolates tested in combination, four (amikacin/meropenem MIC ≤ 64/32 mg/L), including K. pneumoniae 375, maintained limit of detection until 72 h, whereas P. aeruginosa 1544 sustained a 1 log reduction. Combination therapy had no activity against the two isolates with amikacin MIC ≥ 2048 mg/L.

CONCLUSIONS

Inhaled amikacin monotherapy showed bactericidal activity against most isolates tested with amikacin MICs ≤ 256 mg/L. Adjunct inhaled amikacin plus meropenem sustained this activity for 72 h for the tested isolates with amikacin/meropenem MIC ≤ 64/32 mg/L.

Staphylococcus aureus infections: epidemiology, pathophysiology, clinical manifestations, and management

Staphylococcus aureus is a major human pathogen that causes a wide range of clinical infections. It is a leading cause of bacteremia and infective endocarditis as well as osteoarticular, skin and soft tissue, pleuropulmonary, and device-related infections. This review comprehensively covers the epidemiology, pathophysiology, clinical manifestations, and management of each of these clinical entities. The past 2 decades have witnessed two clear shifts in the epidemiology of S. aureus infections: first, a growing number of health care-associated infections, particularly seen in infective endocarditis and prosthetic device infections, and second, an epidemic of community-associated skin and soft tissue infections driven by strains with certain virulence factors and resistance to β-lactam antibiotics. In reviewing the literature to support management strategies for these clinical manifestations, we also highlight the paucity of high-quality evidence for many key clinical questions.

Respiratory infections in patients undergoing mechanical ventilation

Lower respiratory tract infections in mechanically ventilated patients are a frequent cause of antibiotic treatment in intensive-care units. These infections present as severe sepsis or septic shock with respiratory dysfunction in intubated patients. Purulent respiratory secretions are needed for diagnosis, but distinguishing between pneumonia and tracheobronchitis is not easy. Both presentations are associated with longlasting mechanical ventilation and extended intensive-care unit stay, providing a rationale for antibiotic treatment initiation. Differentiation of colonisers from true pathogens is difficult, and microbiological data show Staphylococcus aureus and Pseudomonas aeruginosa to be of great concern because of clinical outcomes and therapeutic challenges. Key management issues include identification of the pathogen, choice of initial empirical antibiotic, and decisions with regard to the resolution pattern.

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.

The impact of antimicrobial resistance and aging in VAP outcomes: experience from a large tertiary care center

Background

Ventilator associated pneumonia (VAP) is a serious infection among patients in the intensive care unit (ICU).

Methods

We reviewed the medical charts of all patients admitted to the adult intensive care units of the Massachusetts General Hospital that went on to develop VAP during a five year period.

Results

200 patients were included in the study of which 50 (25%) were infected with a multidrug resistant pathogen. Increased age, dialysis and late onset (≥5 days from admission) VAP were associated with increased incidence of resistance. Multidrug resistant bacteria (MDRB) isolation was associated with a significant increase in median length of ICU stay (19 vs. 16 days, p = 0.02) and prolonged duration of mechanical ventilation (18 vs. 14 days, p = 0.03), but did not impact overall mortality (HR 1.12, 95% CI 0.51–2.46, p = 0.77). However, age (HR 1.04 95% CI 1.01–1.07, p = 0.003) was an independent risk factor for mortality and age ≥65 years was associated with increased incidence of methicillin-resistant Staphylococcus aureus (MRSA) infections (OR 2.83, 95% CI 1.27–6.32, p = 0.01).

Conclusions

MDRB-related VAP is associated with prolonged ICU stay and mechanical ventilation. Interestingly, age ≥ 65 years is associated with MRSA VAP.

The molecular mechanism of acute lung injury caused by Pseudomonas aeruginosa: from bacterial pathogenesis to host response

Pseudomonas aeruginosa is the most common gram-negative pathogen causing pneumonia in immunocompromised patients. Acute lung injury induced by bacterial exoproducts is associated with a poor outcome in P. aeruginosa pneumonia. The major pathogenic toxins among the exoproducts of P. aeruginosa and the mechanism by which they cause acute lung injury have been investigated: exoenzyme S and co-regulated toxins were found to contribute to acute lung injury. P. aeruginosa secretes these toxins through the recently defined type III secretion system (TTSS), by which gram-negative bacteria directly translocate toxins into the cytosol of target eukaryotic cells. TTSS comprises the secretion apparatus (termed the injectisome), translocators, secreted toxins, and regulatory components. In the P. aeruginosa genome, a pathogenic gene cluster, the exoenzyme S regulon, encodes genes underlying the regulation, secretion, and translocation of TTSS. Four type III secretory toxins, namely ExoS, ExoT, ExoU, and ExoY, have been identified in P. aeruginosa. ExoS is a 49-kDa form of exoenzyme S, a bifunctional toxin that exerts ADP-ribosyltransferase and GTPase-activating protein (GAP) activity to disrupt endocytosis, the actin cytoskeleton, and cell proliferation. ExoT, a 53-kDa form of exoenzyme S with 75% sequence homology to ExoS, also exerts GAP activity to interfere with cell morphology and motility. ExoY is a nucleotidal cyclase that increases the intracellular levels of cyclic adenosine and guanosine monophosphates, resulting in edema formation. ExoU, which exhibits phospholipase A2 activity activated by host cell ubiquitination after translocation, is a major pathogenic cytotoxin that causes alveolar epithelial injury and macrophage necrosis. Approximately 20% of clinical isolates also secrete ExoU, a gene encoded within an insertional pathogenic gene cluster named P. aeruginosa pathogenicity island-2. The ExoU secretory phenotype is associated with a poor clinical outcome in P. aeruginosa pneumonia. Blockade of translocation by TTSS or inhibition of the enzymatic activity of translocated toxins has the potential to decrease acute lung injury and improve clinical outcome.