Outcome in bacteremia associated with nosocomial pneumonia and the impact of pathogen prediction by tracheal surveillance cultures

Risk factors for surgical site infection following cardiac surgery in a region endemic for multidrug resistant organisms

OBJECTIVES

To identify risk factors for surgical site infections following cardiosurgery in an area endemic for multidrug resistant organisms.

DESIGN

Single-center, historical cohort study including patients who underwent cardiosurgery during a 6-year period (2014-2020).

SETTING

Joint Commission International accredited, multiorgan transplant center in Palermo, Italy.

MAIN OUTCOME MEASURES

Surgical site infection was the main outcome.

RESULTS

On a total of 3609 cardiosurgery patients, 184 developed surgical site infection (5.1 %). Intestinal colonization with multidrug resistant organisms was more frequent in patients with surgical site infections (69.6 % vs. 33.3 %; p < 0.001). About half of surgical site infections were caused by Gram-negative bacteria (n = 97; 52.7 %). Fifty surgical site infections were caused by multidrug resistant organisms (27.1 %), with extended-spectrum Beta-lactamase-producing Enterobacterales (n = 16; 8.7 %) and carbapenem-resistant Enterobacterales (n = 26; 14.1 %) being the predominant resistance problem. However, in only 24 of surgical site infections caused by multidrug resistant organisms (48 %), mostly carbapenem-resistant Enterobacterales (n = 22), a pathogen match between the rectal surveillance culture and surgical site infections clinical culture was demonstrated. Nevertheless, multivariate logistic regression analysis identified a rectal swab culture positive for multidrug resistant organisms as an independent risk factor for SSI (odds ratio 3.95, 95 % confidence interval 2.79-5.60). Other independent risk factors were female sex, chronic dialysis, diabetes mellitus, previous cardiosurgery, previous myocardial infarction, being overweight/obese, and longer intubation time.

CONCLUSION

In an area endemic for carbapenem-resistant Enterobacterales, intestinal colonization with multidrug resistant organisms was recognized as independent risk factor for surgical site infections.

IMPLICATIONS FOR CLINICAL PRACTICE

No causal relationship between colonization with resistant pathogens and subsequent infection could be demonstrated. However, from a broader epidemiological perspective, having a positive multidrug resistant organisms colonization status appeared a risk factor for surgical site infections. Therefore, strict infection control measures to prevent cross-transmission remain pivotal (e.g., nasal decolonization, hand hygiene, and skin antisepsis).

Biochemical analysis of protein-protein interfaces underlying the regulation of bacterial secretion systems

Bacterial pathogens such as Pseudomonas aeruginosa use complex regulatory networks to tailor gene expression patterns to meet complex environmental challenges. P. aeruginosa is capable of causing both acute and chronic persistent infections, each type being characterized by distinct symptoms brought about by distinct sets of virulence mechanisms. The GacS/GacA phosphorelay system sits at the heart of a complex regulatory network that reciprocally governs the expression of virulence factors associated with either acute or chronic infections. A second non-enzymatic signaling cascade involving four proteins, ExsA, ExsC, ExsD, and ExsE is a key player in regulating the expression of the type three secretion system, an essential facilitator of acute infections. Both signaling pathways involve a remarkable array of non-canonical interactions that we sought to characterize. In the following section, we will outline several strategies, we adapted to map protein-protein interfaces and quantify the strength of biomolecular interactions by pairing complex mutational analyses with FRET binding assays and Bacterial-Two-Hybrid assays with appropriate functional assays. In the process, protocols were developed for disrupting large hydrophobic interfaces, deleting entire domains within a protein, and for mapping protein-protein interfaces formed primarily through backbone interactions.

Healthcare-associated infections in adult intensive care unit patients: Changes in epidemiology, diagnosis, prevention and contributions of new technologies

Patients in intensive care units (ICUs) are at high risk for healthcare-acquired infections (HAI) due to the high prevalence of invasive procedures and devices, induced immunosuppression, comorbidity, frailty and increased age. Over the past decade we have seen a successful reduction in the incidence of HAI related to invasive procedures and devices. However, the rate of ICU-acquired infections remains high. Within this context, the ongoing emergence of new pathogens, further complicates treatment and threatens patient outcomes. Additionally, the SARS-CoV-2 (COVID-19) pandemic highlighted the challenge that an emerging pathogen provides in adapting prevention measures regarding both the risk of exposure to caregivers and the need to maintain quality of care. ICU nurses hold a special place in the prevention and management of HAI as they are involved in basic hygienic care, steering and implementing quality improvement initiatives, correct microbiological sampling, and aspects antibiotic stewardship. The emergence of more sensitive microbiological techniques and our increased knowledge about interactions between critically ill patients and their microbiota are leading us to rethink how we define HAIs and best strategies to diagnose, treat and prevent these infections in the ICU. This multidisciplinary expert review, focused on the ICU setting, will summarise the recent epidemiology of ICU-HAI, discuss the place of modern microbiological techniques in their diagnosis, review operational and epidemiological definitions and redefine the place of several controversial preventive measures including antimicrobial-impregnated medical devices, chlorhexidine-impregnated washcloths, catheter dressings and chlorhexidine-based mouthwashes. Finally, general guidance is suggested that may reduce HAI incidence and especially outbreaks in ICUs.

Reevaluation of the impact of methicillin-resistance on outcomes in patients with Staphylococcus aureus bacteremia and endocarditis

BACKGROUND/AIMS

Methicillin-resistant Staphylococcus aureus (MRSA) is highly prevalent in hospitals, and has recently emerged in the community. The impact of methicillin-resistance on mortality and medical costs for patients with S. aureus bacteremia (SAB) requires reevaluation.

METHODS

We searched studies with SAB or endocarditis using electronic databases including Ovid-Medline, Embase-Medline, and Cochrane Library, as well as five local databases for published studies during the period January 2000 to September 2011.

RESULTS

A total of 2,841 studies were identified, 62 of which involved 17,563 adult subjects and were selected as eligible. A significant increase in overall mortality associated with MRSA, compared to that with methicillin-susceptible S. aureus (MSSA), was evidenced by an odds ratio (OR) of 1.95 (95% confidence interval [CI], 1.73 to 2.21; p < 0.01). In 13 endocarditis studies, MRSA increased the risk of mortality, with an OR of 2.65 (95% CI, 1.46 to 4.80). When three studies, which compared mortality rates between CA-MRSA and CA-MSSA, were combined, the risk of methicillin-resistance increased 3.23-fold compared to MSSA (95% CI, 1.25 to 8.34). The length of hospital stay in the MRSA group was 10 days longer than that in the MSSA group (95% CI, 3.36 to 16.70). Of six studies that reported medical costs, two were included in the analysis, which estimated medical costs to be $9,954.58 (95% CI, 8,951.99 to 10,957.17).

CONCLUSION

MRSA is still associated with increased mortality, longer hospital stays and medical costs, compared with MSSA in SAB in studies published since the year 2000.

Derivation and validation of a simple score to predict the presence of bacteria requiring carbapenem treatment in ICU-acquired bloodstream infection and pneumonia: CarbaSCORE

Background

The recommendations of learned societies mention risk factors for the presence of multidrug resistant bacteria in hospital-acquired infections, but they do not propose a scoring system to guide empiric antibiotic therapy. Our study was aimed at developing a simple score for predicting "the presence of bacteria requiring carbapenem treatment" in ICU-acquired bloodstream infection and pneumonia.

Methods

Between December 2011 and January 2015, we conducted a retrospective study using a prospectively collected French database of nosocomial infections in the polyvalent intensive care unit of a French university hospital. All patients with ICU-acquired bloodstream infection or pneumonia were included in the study. Bivariate and multivariate analyses were performed to develop the CarbaSCORE, and this score was internally validated.

Results

In total, 338 patients were analyzed, including 27 patients requiring carbapenem treatment. The CarbaSCORE was composed of four criteria: "presence of bloodstream infection" (as opposed to pneumonia) scored 2 points, "chronic hemodialysis" scored 4 points, "travel abroad in the last 6 months" scored 5 points, and "MDR-colonization or prior use of a β-lactam of class ≥ 3" scored 6 points. Internal validation by bootstrapping showed an area under the receiver operating characteristic curve of 0.81 [0.73-0.89]. Sensitivity was 96% at the 6-point threshold and specificity was 91% at the 9-point threshold.

Conclusions

The CarbaSCORE is a simple and efficient score for predicting the presence of bacteria requiring carbapenem treatment. Further studies are needed to test this score before it can be used in practice.

Epidemiology of Multidrug Resistant Infections after Inter-ICU Transfer in India

Background and aims

The patients in the intensive care unit (ICU) are often infected with multidrug resistant (MDR) organisms. When they are transferred to other ICUs, they can expand the reservoir of MDR organisms and pose a threat to the infection control program. The present observational study was undertaken to describe the epidemiology and compare the outcome of MDR and non-MDR infections after inter ICU patient transfer.

Materials and methods

A retrospective study was conducted in a cohort of 134 consecutive admitted patients in a tertiary care ICU from other ICUs. The primary objective was to measure the prevalence of MDR and non-MDR infections. The secondary objective was to compare the outcome between MDR and non-MDR group and identify the factors independently associated with mortality for each group.

Results

Among 134 patients, 89 had infections (66.4%) and in 29 (21.6%) were due to MDR organisms. The most common organism was Klebsiella in the MDR and E. coli in the non-MDR group. There was no difference between the groups in mortality, duration of mechanical ventilation and length of ICU stay. The duration of mechanical ventilation and ICU stay >7 days was independently associated with mortality in the MDR group. No association was found in the non-MDR group.

Conclusion

The study demonstrates a high prevalence of MDR infections after inter ICU transfer. There is no difference in outcome between the groups, but the mortality in the MDR group is independently associated with a longer duration of mechanical ventilation and ICU stay.

How to cite this article

Choudhuri AH, Ahuja B, Biswas PS, Uppal R. Epidemiology of Multidrug Resistant Infections after Inter-ICU Transfer in India. Indian Journal of Critical Care Medicine, January 2019;23(1):1-6.

High rates of methicillin-resistant Staphylococcus aureus colonisation in a Brazilian Intensive Care Unit

OBJECTIVE

To evaluate the colonisation rate of Staphylococcus aureus in the oropharynx and the insertion site of central venous catheters in intensive care unit patients.

DESIGN

Cross-sectional study.

SETTING

Brazilian intensive care unit.

MEASUREMENTS

Samples were collected from October to December 2015 from the oropharyngeal cavity and central venous catheter insertion site of 110 patients. Samples that presented growth of Staphylococcus aureus were isolated and their sensitivity profiles were tested for several antimicrobials.

FINDINGS

The study participants (110) were mostly females older than 60 years (53.6%). The mean length of hospitalisation was 15.5 days (±31.3). A total of 188 biological samples were collected: 110 collected from the oropharynx and 78 from the central venous catheter insertion site. A 35% (n = 38/110) S. aureus colonisation rate of the patients was observed in at least one collection site. In the oropharynx alone, a 31% rate (n = 34/110) was found, and a 12.8% rate (n = 10/78) at central venous catheter insertion sites only. MRSA colonisation in the oropharynx or at the central venous catheter occurred in 29 (26.4%) patients and vancomycin resistant Staphylococcus aureus was present in 24 (22.4%) of the patients studied. Patients hospitalised for seven days or more were 4.8 times more likely to be colonised compared to patients hospitalised less than seven days (95% CI = 1.2-28.5).

CONCLUSION

The oropharynx and the central venous catheter are important reservoirs of this bacterium that in critical conditions may become pathogenic. The data showed a high degree of resistance of the bacterial populations isolated to different drugs, which may hinder the control of these organisms.

Prospective observational study to compare oral topical metronidazole versus 0.2% chlorhexidine gluconate to prevent nosocomial pneumonia

BACKGROUND

Nosocomial pneumonia is one of the most common health care-associated infections in intensive care units (ICUs) worldwide, attributing to high morbidity and mortality. Our study aim is to investigate the effectiveness of oral hygiene with 0.2% chlorhexidine gluconate (CHX) and 0.08% metronidazole (MDE) influencing the microbiologic epidemiology and incidence of nonintubation pneumonia (NIP) and ventilator-associated pneumonia (VAP).

METHODS

Patients who stayed >48 hours in the emergency ICU between 2008 and 2012 were enrolled and provided oral hygiene by swabbing with 0.08% MDE twice daily until discharge or death during the first year (period M), whereas CHX was applied during the following 3 years (period C). The incidence and microbiologic epidemiology of NIP and VAP were studied.

RESULTS

There were 873 patients enrolled. There were 44 episodes of NIP and 25 episodes of VAP that occurred among 212 patients in period M, and 84 episodes of NIP and 49 episodes of VAP occurred among 661 patients in period C. Overall, the rate of NIP and VAP decreased year by year. Acinetobacter baumannii was the most frequently identified bacteria for NIP (22.9%) and VAP (25.3%), with an annual ascent. Few changes were observed on bacteria distribution for NIP and VAP.

CONCLUSIONS

Oral hygiene with CHX, having reduced the incidence of nosocomial pneumonia among critical ill patients, suggests a benefit of oral hygiene in decreasing the incidence of nosocomial pneumonia, including VAP in ICUs, but not bacterial epidemiology.

Clinical manifestations of pneumonia according to the causative organism in patients in the intensive care unit

BACKGROUND/AIMS

Whether the causative organism influences the clinical course of pneumonia in the intensive care unit (ICU) is controversial. We assessed the clinical manifestations and prognosis of pneumonia according to the causative pathogens in patients in a medical ICU.

METHODS

A retrospective observational study was performed in a medical ICU. Among 242 patients who were admitted to the ICU, 103 who were treated for pneumonia were analyzed.

RESULTS

The causative pathogen was identified in 50 patients (49.0%); 22 patients (21.6%) had multidrug-resistant (MDR) pathogens. The distribution of causative micro-organisms was Staphylococcus aureus (20%), Pseudomonas species (16%), Klebsiella pneumoniae (14%), and Acinetobacter baumannii (12%). No significant difference in ICU mortality rate, duration of ICU stay, duration of mechanical ventilation, or frequencies of re-intubation and tracheostomy were detected based on the identification of any pathogen. In sub-analyses according to the pneumonia classification, the number of pathogens identified did not differ between pneumonia types, and a higher incidence of identified MDR pathogens was detected in the hospital-acquired pneumonia group than in the community-acquired or healthcare- acquired pneumonia groups. However, the clinical outcomes of pneumonia according to identification status and type of pathogen did not differ significantly between the groups.

CONCLUSIONS

Neither the causative micro-organism nor the existence of MDR pathogens in critically ill patients with pneumonia was associated with the clinical outcome of pneumonia, including ICU mortality. This result was consistent regardless of the pneumonia classification.

Potential role for telavancin in bacteremic infections due to gram-positive pathogens: focus on Staphylococcus aureus

Staphylococcus aureus bacteremia (SAB) is one of the most common serious bacterial infections and the most frequent invasive infection due to methicillin-resistant S. aureus (MRSA). Treatment is challenging, particularly for MRSA, because of limited treatment options. Telavancin is a bactericidal lipoglycopeptide antibiotic that is active against a range of clinically relevant gram-positive pathogens including MRSA. In experimental animal models of sepsis telavancin was shown to be more effective than vancomycin. In clinically evaluable patients enrolled in a pilot study of uncomplicated SAB, cure rates were 88% for telavancin and 89% for standard therapy. Among patients with infection due to only gram-positive pathogens enrolled in the 2 phase 3 studies of telavancin for treatment of hospital-acquired pneumonia, cure rates for those with bacteremic S. aureus pneumonia were 41% (9/22, telavancin) and 40% (10/25, vancomycin) with identical mortality rates. These data support further evaluation of telavancin in larger, prospective studies of SAB.

Surveillance cultures in healthcare-associated pneumonia: sense or nonsense?

PURPOSE OF REVIEW

This review explores the usefulness of surveillance cultures in healthcare-associated pneumonia (HCAP).

RECENT FINDINGS

The definition of HCAP is controversial. Causative micro-organisms of HCAP resemble those found in hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP). Some types of surveillance cultures have proven useful in hospitalized patients. Whereas numerous studies have investigated the role of surveillance cultures in VAP, one may wonder whether surveillance culture implementation should belong in HCAP management guidelines.

SUMMARY

Studies exploring the usefulness of obtaining surveillance cultures in VAP are numerous, but are mostly retrospective, observational and/or quasi-experimental in nature. Surveillance cultures may be useful for antibiotic guidance, but positive predictive value and specificity of surveillance cultures are low, obviously negatively impacting on cost effectiveness, especially in the large population at risk for HCAP. On the other hand, multidrug-resistance is increasing and surveillance cultures for methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci in ICU-admitted patients appeared useful and cost-effective. Furthermore, surveillance cultures for the presence of multidrug-resistant Gram-negative bacilli might be useful for antibiotic guidance. Currently, neither community-acquired pneumonia, HCAP, HAP nor VAP guidelines incorporate surveillance cultures. In the future, surveillance cultures in populations at risk for HCAP may be able to differentiate HCAP from other kinds of pneumonia and authorize its reason for existence.

Minimizing antibiotic exposure in the ICU: in search of the optimal strategy

The current paradigm for antibiotic management in critically ill patients is to initiate broad-spectrum therapy followed by de-escalation based on microbiological results. Routine screening cultures may allow better targeting and reduce unnecessary exposure to antibiotics.

De-escalation of antimicrobial treatment in neutropenic patients with severe sepsis: results from an observational study

BACKGROUND

In severe sepsis, guidelines recommend de-escalating the empirical antimicrobial treatment as soon as the microbiological results are available. We aimed to determine the rate of de-escalation of the empirical antimicrobial treatment in neutropenic patients with severe sepsis. The characteristics of antimicrobial treatment associated with de-escalation and its impact on short- and long-term survival were also determined.

METHODS

In the intensive care unit (ICU) of a cancer referral center, we prospectively collected observational data related to the antimicrobial management in neutropenic patients who developed severe sepsis and were admitted to ICU for at least 48 h. De-escalation of antimicrobial therapy consisted either of deleting one of the empirical antibiotics of a combined treatment, or, whenever possible, to use a betalactam antibiotic with a narrower spectrum of activity. Multivariate logistic regression was conducted to determine the factors associated with de-escalation, while a Cox proportional hazards model with a time-dependent covariate was fitted to assess the effect of de-escalation on 30-day survival. Finally 1-year survival after ICU discharge was compared across de-escalation groups.

RESULTS

Cumulative incidence of de-escalation of the empirical antimicrobial treatment among the 101 patients of the cohort was 44%, [95% confidence interval (CI) 38-53%], including 30 (68%) patients with ongoing neutropenia. A microbiological documentation was available in 63 (63%) patients. Factors associated with de-escalation were the adequation of the empirical antimicrobial treatment in ICU [OR = 10.8 (95% CI 1.20-96)] for adequate documented treatment versus appropriate empirical treatment, the compliance with guidelines regarding the empirical choice of the anti-pseudomonal betalactam [OR = 10.8 (95% CI 1.3-89.5)]. De-escalation did not significantly modify the hazard of death within the first 30 days [HR = 0.51 (95% CI 0.20-1.33)], nor within 1 year after ICU discharge [HR = 1.06 (95% CI 0.54-2.08)].

CONCLUSION

Our data suggest that, in ICU, de-escalation of the empirical antimicrobial treatment is frequently applied in neutropenic cancer patients with severe sepsis. No evidence of any prognostic impact of this de-escalation was found.

Outcomes in critically ill chronic lymphocytic leukemia patients

BACKGROUND

Although recent studies have demonstrated an improvement in the prognosis of critically ill cancer patients, little is known regarding the prognosis of patients with non-aggressive underlying malignancies. The aims of this study were to assess the prognosis of critically ill patients with chronic lymphocytic leukemia (CLL) and to evaluate risk factors for hospital mortality.

METHODS

In retrospective mono-center cohort study, consecutive adult patients with CLL requiring ICU admission from 1997 to 2008 were included.

RESULTS

Sixty-two patients of 67 years (62-75) were included. Median time interval between CLL diagnosis and ICU admission was 6.7 years (2.6-10.8). Nine patients (15 %) had stage C disease at the time of ICU admission, and seven patients (11 %) had Richter syndrome. Most ICU admissions were related to bacterial or fungal pulmonary infections (n = 47; 76 %). ICU, in-hospital, and 90-day mortality were 35 % (n = 22), 42 % (n = 26), and 58 % (n = 36), respectively. Only three factors were independently associated with in-hospital mortality: oxygen saturation lower than 95 % when breathing room air (odds ratio (OR) 5.80; 95 % confidence interval (CI) 1.23-27.33), need for vasopressors (OR 27.94; 95 % CI 5.37-145.4), and past history of infection (OR 6.62; 95 % CI 1.34-32.68). The final model did not change when disease-related variables (Binet classification, Richter syndrome, long-term steroids) or treatment-related variables (fludarabine, rituximab, or alemtuzumab) were included.

CONCLUSION

Acute pulmonary infections remain the leading cause of ICU admission in patients with CLL. The severity at ICU admission and past history of infection were the only factors associated with hospital mortality. Neither disease characteristics nor previous cancer treatments were associated with outcome.

Self-trimerization of ExsD limits inhibition of the Pseudomonas aeruginosa transcriptional activator ExsA in vitro

The opportunistic pathogen Pseudomonas aeruginosa ranks among the leading causes of nosocomial infection. The type III secretion system (T3SS) aids acute Pseudomonas aeruginosa infection by injecting potent cytotoxins into host cells to suppress the host's innate immune response. Expression of all T3SS-related genes is strictly dependent on the transcription factor ExsA. Consequently, ExsA and the biological processes that regulate ExsA function are of great biomedical interest. The present study focused on the ExsA-ExsC-ExsD-ExsE signaling cascade, which ties host cell contact to the upregulation of T3SS gene expression. Prior to T3SS induction, the antiactivator protein ExsD binds to ExsA and blocks ExsA-dependent transcription by interfering with ExsA dimerization and promoter interactions. Upon host cell contact, ExsD is sequestered by the T3SS chaperone ExsC, resulting in the release of ExsA and upregulation of the T3SS. Previous studies have shown that the ExsD-ExsA interactions are not freely reversible. Because independently folded ExsD and ExsA were not found to interact, it has been hypothesized that folding intermediates of the two proteins form the complex. Here, we demonstrate, for the first time, that ExsD alone is sufficient to inhibit ExsA-dependent transcription in vitro and that no other cellular factors are required. More significantly, we show that independently folded ExsD and ExsA are capable of interacting, but only at 37 °C and not at 30 °C. Guided by the crystal structure of ExsD, we designed a monomeric variant of the protein, and demonstrated that ExsD trimerization prevents ExsD from inhibiting ExsA-dependent transcription at 30 °C. We propose that this unique mechanism plays an important role in T3SS regulation.

Early diagnosis of resistant pathogens: how can it improve antimicrobial treatment?

Infections with organisms that are resistant to various anti-microbial agents pose a serious challenge to effective management of infections. Resistance to antimicrobial agents, which may be intrinsic or acquired, has been noted in a wide variety of microorganisms causing human infections. These include resistance to antiviral agents in HIV, HBV, CMV and influenza virus, anti-parasitic agents in Plasmodium falciparum, anti-fungal agents in certain Candida species and MDR (multidrug-resistant) tuberculosis. It is however, the problem of multidrug-resistant bacterial infections (caused by MRSA, VRE, ESBL/AmpC/metallo-β lactamase producers and colistin-resistant Gram-negative bacilli) that has become a cause of major concern in clinical settings. Infections with these organisms can increase morbidity, mortality, increase the cost of therapy and increase the duration of hospitalization. The objective of this article is to review the question how early diagnosis of these infections, affects the overall management of infected or colonized patients, with regard to antimicrobial therapy.

Value of lower respiratory tract surveillance cultures to predict bacterial pathogens in ventilator-associated pneumonia: systematic review and diagnostic test accuracy meta-analysis

PURPOSE

In ventilator-associated pneumonia (VAP), early appropriate antimicrobial therapy may be hampered by involvement of multidrug-resistant (MDR) pathogens.

METHODS

A systematic review and diagnostic test accuracy meta-analysis were performed to analyse whether lower respiratory tract surveillance cultures accurately predict the causative pathogens of subsequent VAP in adult patients. Selection and assessment of eligibility were performed by three investigators by mutual consideration. Of the 525 studies retrieved, 14 were eligible for inclusion (all in English; published since 1994), accounting for 791 VAP episodes. The following data were collected: study and population characteristics; in- and exclusion criteria; diagnostic criteria for VAP; microbiological workup of surveillance and diagnostic VAP cultures. Sub-analyses were conducted for VAP caused by Staphylococcus aureus, Pseudomonas spp., and Acinetobacter spp., MDR microorganisms, frequency of sampling, and consideration of all versus the most recent surveillance cultures.

RESULTS

The meta-analysis showed a high accuracy of surveillance cultures, with pooled sensitivities up to 0.75 and specificities up to 0.92 in culture-positive VAP. The area under the curve (AUC) of the hierarchical summary receiver-operating characteristic curve demonstrates moderate accuracy (AUC: 0.90) in predicting multidrug resistance. A sampling frequency of >2/week (sensitivity 0.79; specificity 0.96) and consideration of only the most recent surveillance culture (sensitivity 0.78; specificity 0.96) are associated with a higher accuracy of prediction.

CONCLUSIONS

This study provides evidence for the benefit of surveillance cultures in predicting MDR bacterial pathogens in VAP. However, clinical and statistical heterogeneity, limited samples sizes, and bias remain important limitations of this meta-analysis.

Assessment of microbial diversity in biofilms recovered from endotracheal tubes using culture dependent and independent approaches

Ventilator-associated pneumonia (VAP) is a common nosocomial infection in mechanically ventilated patients. Biofilm formation is one of the mechanisms through which the endotracheal tube (ET) facilitates bacterial contamination of the lower airways. In the present study, we analyzed the composition of the ET biofilm flora by means of culture dependent and culture independent (16 S rRNA gene clone libraries and pyrosequencing) approaches. Overall, the microbial diversity was high and members of different phylogenetic lineages were detected (Actinobacteria, beta-Proteobacteria, Candida spp., Clostridia, epsilon-Proteobacteria, Firmicutes, Fusobacteria and gamma-Proteobacteria). Culture dependent analysis, based on the use of selective growth media and conventional microbiological tests, resulted in the identification of typical aerobic nosocomial pathogens which are known to play a role in the development of VAP, e.g. Staphylococcus aureus and Pseudomonas aeruginosa. Other opportunistic pathogens were also identified, including Staphylococcus epidermidis and Kocuria varians. In general, there was little correlation between the results obtained by sequencing 16 S rRNA gene clone libraries and by cultivation. Pyrosequencing of PCR amplified 16 S rRNA genes of four selected samples resulted in the identification of a much wider variety of bacteria. The results from the pyrosequencing analysis suggest that these four samples were dominated by members of the normal oral flora such as Prevotella spp., Peptostreptococcus spp. and lactic acid bacteria. A combination of methods is recommended to obtain a complete picture of the microbial diversity of the ET biofilm.

Overview of antimicrobial therapy in intensive care units

In the management of a patient with severe sepsis, it is important to suspect the infection early, to collect samples immediately after diagnosis and to promptly initiate a broad-spectrum antibiotic treatment. The choice of this empirical antimicrobial therapy should be based on host characteristics, site of infection, local ecology and pharmacokinetics/pharmacodynamics of antibiotics. In severe infection, guidelines recommend the use of a combination of antibiotics. After results of cultures are obtained, treatment should be re-evaluated to either de-escalate or escalate the antibiotic prescription. This is associated with optimal costs, decreased incidence of superinfection and minimal development of antimicrobial resistance. All these steps should rely on written protocols, and the compliance to these protocols should be continuously monitored in order to detect violations and implement corrective procedures.

The role of surveillance cultures in the prediction of susceptibility patterns of Gram-negative bacilli in the intensive care unit

Surveillance cultures may detect colonisation with drug-resistant Gram-negative bacteria and can be hypothesised to guide appropriate initial antibiotic treatment for intensive care unit (ICU) patients. We investigated the microbiological data of 228 episodes of nosocomial bloodstream infection (BSI) due to Gram-negative bacteria in an ICU in which piperacillin/tazobactam or meropenem was used empirically for serious infections, to evaluate the contribution of surveillance cultures to an appropriate choice of initial antibiotic therapy. Surveillance cultures were taken in advance of BSI in 218 (95.6%) of 228 episodes. Concordant organisms with identical identification and susceptibilities were found in prior surveillance cultures and subsequent blood cultures in 65 (29.8%) of 218 episodes. Surveillance cultures predicted resistance in 52.9% and 51.4% of BSIs caused by resistant pathogens to piperacillin/tazobactam and meropenem, respectively. The negative predictive value of surveillance cultures negative for a resistant organism also exceeded 90% for piperacillin/tazobactam and meropenem. Given that the overall resistant rates of BSI pathogens of our study were 11.3% to piperacillin/tazobactam and 16.4% to meropenem, surveillance cultures in our setting may provide important information on the probability of drug resistance of the causative pathogens and some utility in aiding empiric antibiotic therapy for ICU patients who subsequently develop BSI.

[Antibiotic multiresistance in critical care units]

The presence of microorganisms with acquired resistance to multiple antibiotics complicates the management and outcome of critically ill patients. The intensivist, in his/her daily activity, is responsible for the prevention and control of the multiresistance and the challenge of prescribing the appropriate treatment in case of an infection by these microorganisms. We have reviewed the literature regarding the definition, important concepts related to transmission, recommendations on general measures of control in the units and treatment options. We also present data on the situation in our country known primarily through the ENVIN-UCI register. Addressing the multiresistance not only requires training but also teamwork with other specialists and adaptation to the local environment.

A New Approach to Ventilator-associated Pneumonia Based on the PIRO System

Several new scoring systems have been developed over recent years to assess the degree of organ failure (e.g., Acute Physiology and Chronic Health Evaluation [APACHE] II, APACHE III, Sequential Organ Failure Assessment [SOFA], Simplified Acute Physiology Score [SAPS] II, and Multiple Organ Dysfunction Score [MODS]). Most of these were models generated based on the concepts of sepsis, severe sepsis and septic shock. In 2001, an International Sepsis Definition Conference updated these terms in order to facilitate standardized enrolment into clinical trials, but due to their simplicity and easy use physicians rapidly adopted them for daily clinical practice [1].

Systematic review and meta-analysis of the efficacy of appropriate empiric antibiotic therapy for sepsis

Quantifying the benefit of early antibiotic treatment is crucial for decision making and can be assessed only in observational studies. We performed a systematic review of prospective studies reporting the effect of appropriate empirical antibiotic treatment on all-cause mortality among adult inpatients with sepsis. Two reviewers independently extracted data. Risk of bias was assessed using the Newcastle-Ottawa score. We calculated unadjusted odds ratios (ORs) with 95% confidence intervals for each study and extracted adjusted ORs, with variance, methods, and covariates being used for adjustment. ORs were pooled using random-effects meta-analysis. We examined the effects of methodological and clinical confounders on results through subgroup analysis or mixed-effect meta-regression. Seventy studies were included, of which 48 provided an adjusted OR for inappropriate empirical antibiotic treatment. Inappropriate empirical antibiotic treatment was associated with significantly higher mortality in the unadjusted and adjusted comparisons, with considerable heterogeneity occurring in both analyses (I(2) > 70%). Study design, time of mortality assessment, the reporting methods of the multivariable models, and the covariates used for adjustment were significantly associated with effect size. Septic shock was the only clinical variable significantly affecting results (it was associated with higher ORs). Studies adjusting for background conditions and sepsis severity reported a pooled adjusted OR of 1.60 (95% confidence interval = 1.37 to 1.86; 26 studies; number needed to treat to prevent one fatal outcome, 10 patients [95% confidence interval = 8 to 15]; I(2) = 46.3%) given 34% mortality with inappropriate empirical treatment. Appropriate empirical antibiotic treatment is associated with a significant reduction in all-cause mortality. However, the methods used in the observational studies significantly affect the effect size reported. Methods of observational studies assessing the effects of antibiotic treatment should be improved and standardized.

Patterns of antimicrobial therapy in severe nosocomial infections: empiric choices, proportion of appropriate therapy, and adaptation rates--a multicentre, observational survey in critically ill patients

This prospective, observational multicentre (n=24) study investigated relationships between antimicrobial choices and rates of empiric appropriate or adequate therapy, and subsequent adaptation of therapy in 171 ICU patients with severe nosocomial infections. Appropriate antibiotic therapy was defined as in vitro susceptibility of the causative pathogen and clinical response to the agent administered. In non-microbiologically documented infections, therapy was considered adequate in the case of favourable clinical response <5 days. Patients had pneumonia (n=127; 66 ventilator-associated), intra-abdominal infection (n=23), and bloodstream infection (n=21). Predominant pathogens were Pseudomonas aeruginosa (n=29) Escherichia coli (n=26), Staphylococcus aureus (n=22), and Enterobacter aerogenes (n=21). In 49.6% of infections multidrug-resistant (MDR) bacteria were involved, mostly extended-spectrum beta-lactamase (EBSL)-producing Enterobacteriaceae and MDR non-fermenting Gram-negative bacteria. Prior antibiotic exposure and hospitalisation in a general ward prior to ICU admission were risk factors for MDR. Empiric therapy was appropriate/adequate in 63.7% of cases. Empiric schemes were classified according to coverage of (i) ESBL-producing Enterobacteriaceae and non-fermenting Gram-negative bacteria ("meropenem-based"), (ii) non-fermenting Gram-negative bacteria (schemes with an antipseudomonal agent), and (iii) first-line agents not covering ESBL-Enterobacteriaceae nor non-fermenting Gram-negative bacteria. Meropenem-based schemes allowed for significantly higher rates of appropriate/adequate therapy (p<0.001). This benefit remained when only patients without risk factors for MDR were considered (p=0.021). In 106 patients (61%) empiric therapy was modified: in 60 cases following initial inappropriate/inadequate therapy, in 46 patients in order to refine empiric therapy. In this study reflecting real-life practice, first-line use of meropenem provided significantly higher rates of the appropriate/adequate therapy, irrespective of presence of risk factors for MDR.

Efficacy of monotherapy in the treatment of Pseudomonas ventilator-associated pneumonia in patients with trauma

BACKGROUND

Controversy persists regarding the optimal treatment regimen for Pseudomonas ventilator-associated pneumonia (VAP). Combination antibiotic therapy is used to broaden the spectrum of activity of empiric treatment and provide synergistic bacteriocidal activity. The relevance of such "synergy" is commonly supposed but poorly supported. The purpose of this study was to evaluate the efficacy of monotherapy in the treatment of Pseudomonas VAP as measured by microbiological resolution.

METHODS

Patients admitted to the trauma intensive care unit during a 36-month period with gram-negative VAP diagnosed on initial bronchoalveolar lavage (BAL) (> or = 10(5) colony forming units [CFU]/mL) were evaluated. All patients received empiric antibiotic monotherapy based on the duration of intensive care unit stay. Patients with Pseudomonas VAP were identified and appropriate monotherapy was selected. Repeat BAL was performed on day 4 of appropriate antibiotic therapy to determine efficacy. Microbiological resolution was defined as < or = 10(3) CFU/mL. Combination therapy with an aminoglycoside was reserved for patients with either persistent positive or increasing colony counts on repeat BAL. Recurrence was defined as > or = 10(5) CFU/mL on subsequent BAL after 2 weeks of appropriate therapy.

RESULTS

One hundred ninety-six patients were identified with late gram-negative VAP. There were 84 patients with Pseudomonas VAP. Monotherapy achieved microbiological resolution in 79 patients (94.1%) with zero recurrence. Thirty-six isolates were completely eradicated at repeat BAL. Five patients (5.9%) required combination therapy to achieve resolution.

CONCLUSIONS

Monotherapy in the treatment of Pseudomonas VAP has an excellent success rate in patients with trauma. Empiric monotherapy therapy should be modified once susceptibility of the microorganism is documented (all isolates were sensitive to cefepime) and antibiotic choice should be based on local patterns of susceptibilities. The routine use of combination therapy for synergy is unnecessary. Combination therapy should be reserved for patients with persistent microbiological evidence of Pseudomonas VAP despite adequate therapy.

Epidemiology and outcome of nosocomial bloodstream infection in elderly critically ill patients: a comparison between middle-aged, old, and very old patients

BACKGROUND

We investigated the epidemiology of nosocomial bloodstream infection in elderly intensive care unit (ICU) patients.

METHODS

In a single-center, historical cohort study (1992-2006), we compared middle-aged (45-64 years; n = 524), old(65-74 years; n = 326), and very old ICU patients (> 75 years; n = 134) who developed a nosocomial bloodstream infection during their ICU stay.

RESULTS

Although the total number of ICU admissions (patients aged > or = 45 years) decreased by approximately 10%, the number of very old patients increased by 33% between the periods 1992-1996 and 2002-2006. The prevalence of bloodstream infection (per 1,000 ICU admissions) increased significantly over time among old (p = 0.001) and very old patients (p = 0.002), but not among middle-aged patients (p = 0.232). Yet, this trend could not be confirmed with the incidence data expressed per 1,000 patient days (p > 0.05). Among patients with bloodstream infection, the proportion of very old patients increased significantly with time from 7.2% (1992-1996) to 13.5% (1997-2001) and 17.4% (2002-2006) (p <0.001). The incidence of bloodstream infection (per 1000 patient days) decreased with age: 8.4 per thousand in middle-aged, 5.5 per thousand in old, and 4.6 per thousand in very old patients (p < 0.001). Mortality rates increased with age: 42.9%, 49.1%, and 56.0% for middle-aged, old, and very old patients, respectively (p = 0.015). Regression analysis revealed that the adjusted relationship with mortality was borderline significant for old age (hazard ratio, 1.2; 95% confidence interval, 1.0 -1.5) and significant for very old age (hazard ratio,1.8; 95% confidence interval, 1.4 -2.4).

CONCLUSION

Over the past 15 years, an increasing number of elderly patients were admitted to our ICU. The incidence of nosocomial bloodstream infection is lower among very old ICU patients when compared to middle-aged and old patients. Yet, the adverse impact of this infection is higher in very old patients.

Predictors of bacteraemia and mortality in patients with acute liver failure

PURPOSE

To determine what physiological and biochemical factors predict development of bacteraemia and mortality in patients with acute liver failure (ALF).

METHODS

Retrospective analysis of 206 ALF patients admitted to a specialist liver intensive therapy unit (LITU) from January 2003 to July 2005 (data collected prospectively).

RESULTS

A total of 206 patients were defined with ALF: 72 (35%) suffered bacteraemia (BAClf) and 134 (65%) did not (NBAClf). Gram positive organisms were observed in 44% of isolates, gram negatives in 52% and fungaemia in 4%. Median time to first bacteraemia was 10 (7-16) days. On admission, BAClf patients had higher SIRS scores and degrees of hepatic encephalopathy (HE). During their LITU course, BAClf patients had significantly increased requirements for renal replacement therapy (RRT), mechanical ventilation, and longer median LITU stay. Multivariate analysis (logistical regression) demonstrated significant predictors of bacteraemia on admission were HE grade >2 (Odds Ratio 1.6) and SIRS score >1 (OR 2.7). In all patients, independent predictors of mortality (logistical) were age (OR 1.41), maximum HE grade pre-intubation (1.76), Lactate (1.14) and Acute Physiology and Chronic Health Evaluation II score (APACHEII) (1.09), but not bacteraemia. Transplantation was protective (OR 0.20).

CONCLUSION

In this study, severity of hepatic encephalopathy and SIRS score >1 were predictive of bacteraemia. APACHEII was independently predictive of mortality in all ALF patients but not bacteraemia.

Determinants and impact of multidrug antibiotic resistance in pathogens causing ventilator-associated-pneumonia

INTRODUCTION

The idea that multidrug resistance (MDR) to antibiotics in pathogens causing ventilator-associated pneumonia (VAP) is an independent risk factor for adverse outcome is still debated. We aimed to identify the determinants of MDR versus non-MDR microbial aetiology in VAP and assessed whether MDR versus non-MDR VAP was independently associated with increased 30-day mortality.

METHODS

We performed a retrospective analysis of a prospectively registered cohort of adult patients with microbiologically confirmed VAP, diagnosed at a university hospital intensive care unit during a three-year period. Determinants of MDR as compared with non-MDR microbial aetiology and impact of MDR versus non-MDR aetiology on mortality were investigated using multivariate logistic and competing risk regression analysis.

RESULTS

MDR pathogens were involved in 52 of 192 episodes of VAP (27%): methicillin-resistant Staphylococcus aureus in 12 (6%), extended-spectrum beta-lactamase producing Enterobacteriaceae in 28 (15%), MDR Pseudomonas aeruginosa and other non-fermenting pathogens in 12 (6%). Multivariable logistic regression identified the Charlson index of comorbidity (odds ratio (OR) = 1.38, 95% confidence interval (CI) = 1.08 to 1.75, p = 0.01) and previous exposure to more than two different antibiotic classes (OR = 5.11, 95% CI = 1.38 to 18.89, p = 0.01) as predictors of MDR aetiology. Thirty-day mortality after VAP diagnosis caused by MDR versus non-MDR was 37% and 20% (p = 0.02), respectively. A multivariate competing risk regression analysis showed that renal replacement therapy before VAP (standardised hazard ratio (SHR) = 2.69, 95% CI = 1.47 to 4.94, p = 0.01), the Charlson index of comorbidity (SHR = 1.21, 95% CI = 1.03 to 1.41, p = 0.03) and septic shock on admission to the intensive care unit (SHR = 1.86, 95% CI = 1.03 to 3.35, p = 0.03), but not MDR aetiology of VAP, were independent predictors of mortality.

CONCLUSIONS

The risk of MDR pathogens causing VAP was mainly determined by comorbidity and prior exposure to more than two antibiotics. The increased mortality of VAP caused by MDR as compared with non-MDR pathogens was explained by more severe comorbidity and organ failure before VAP.

Pseudomonas aeruginosa infection after living-donor liver transplantation in adults

OBJECTIVES

Pseudomonas aeruginosa infection is a major cause of bacterial infection after deceased-donor liver transplantation. The incidence and risk factors of P. aeruginosa infection after living-donor liver transplantation (LDLT), however, are not known.

METHODS

We retrospectively reviewed the data from 170 adult patients who underwent LDLT at the University of Tokyo Hospital. The microbiologic and medical records of the patients from admission to 3 months after LDLT were reviewed. Uni- and multivariate analyses were performed to identify the independent risk factors for postoperative P. aeruginosa infection.

RESULT

Preoperative P. aeruginosa carriage was identified in 15 (9%) patients. Only 2 of the 15 patients later presented with postoperative P. aeruginosa infection. Postoperative P. aeruginosa infection occurred in 27 (16%) of 170 patients by median postoperative day 38. Among those 27 patients, surgical site infections were recorded in 8 (30%) and intra-abdominal infections in 14 (52%). In 5 of the 27 (19%) patients, P. aeruginosa isolates were multiple antimicrobial resistant. Postoperative bile leakage independently predicted postoperative P. aeruginosa infection.

CONCLUSION

P. aeruginosa infections were frequently detected after LDLT, including those by multiple antimicrobial-resistant isolates. Postoperative bile leakage predisposed patients to P. aeruginosa infection. Surveillance culture should be checked periodically after LDLT to ensure that appropriate antimicrobials can be administered for postoperative infection.

Screening for resistant gram-negative microorganisms to guide empiric therapy of subsequent infection

OBJECTIVE

To define the potential of resistant gram-negative colonization surveillance to predict etiology of subsequent infection and improve adequacy of empiric antimicrobial treatment.

DESIGN

Retrospective cohort study.

SETTING

A mixed medical-surgical six-bed intensive care unit (ICU), from November 2003 to December 2006.

PATIENTS

All patients having at least one episode of ventilator-associated pneumonia (VAP) or bloodstream infection (BSI) caused by a resistant gram-negative pathogen during the study period.

INTERVENTIONS

Colonization surveillance of the respiratory tract and gastrointestinal tract was systematically performed in all ICU patients. Tracheal aspirates were obtained twice weekly and rectal swabs once weekly. Both tracheal and rectal samples were cultured in antibiotic-enriched media (containing ceftazidime, ciprofloxacin, imipenem or piperacillin/tazobactam), to focus on resistant gram-negative pathogen isolation.

MEASUREMENTS AND RESULTS

Colonization concordance between resistant, gram-negative pathogens of infectious episodes and previous, recent (<or=7 days) colonization of the respiratory and gastrointestinal tract was determined, based on species identity and antimicrobial susceptibility. Concordance was 82% in VAP and 86% in BSI cases and was further confirmed by molecular testing of 15 randomly selected cases by REP-PCR. Previous colonization had high sensitivity and specificity in VAP, but was less specific in BSI cases. Knowledge of previous colonization improved the rate of adequate empiric antimicrobial treatment (91 vs. 40% in VAP and 86 vs. 50% in BSI cases, P < 0.05).

CONCLUSIONS

Colonization surveillance for resistant gram-negative microorganisms is predictive of subsequent infection etiology and can improve empiric antimicrobial treatment adequacy in a critical care setting.

Potent in vitro activity of tomopenem (CS-023) against methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa

Tomopenem (formerly CS-023) is a novel 1beta-methylcarbapenem with broad-spectrum coverage of gram-positive and gram-negative pathogens. Its antibacterial activity against European clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa was compared with those of imipenem and meropenem. The MICs of tomopenem against MRSA and P. aeruginosa at which 90% of the isolates tested were inhibited were 8 and 4 microg/ml, respectively, and were equal to or more than fourfold lower than those of imipenem and meropenem. The antibacterial activity of tomopenem against MRSA was correlated with a higher affinity for the penicillin-binding protein (PBP) 2a. Its activity against laboratory mutants of P. aeruginosa with (i) overproduction of chromosomally coded AmpC beta-lactamase; (ii) overproduction of the multidrug efflux pumps MexAB-OprM, MexCD-OprJ, and MexEF-OprN; (iii) deficiency in OprD; and (iv) various combinations of AmpC overproduction, MexAB-OprM overproduction, and OprD deficiency were tested. The increases in the MIC of tomopenem against each single mutant compared with that against its parent strain were within a fourfold range. Tomopenem exhibited antibacterial activity against all mutants, with an observed MIC range of 0.5 to 8 microg/ml. These results suggest that the antibacterial activity of tomopenem against the clinical isolates of MRSA and P. aeruginosa should be ascribed to its high affinity for PBP 2a and its activity against the mutants of P. aeruginosa, respectively.