Multidrug-resistant pathogens and pneumonia: comparing the trauma and surgical intensive care units

Defining Pathogen and Susceptibility Patterns for Early Versus Late Ventilator Associated Pneumonia in Trauma Patients to Guide Empiric Treatment Decisions

INTRODUCTION

Studies have demonstrated that trauma patients with early-ventilator associated pneumonia (early-VAP, < 7 days) have decreased risk of methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa infections. We hypothesize that routinely using broad-spectrum antibiotics is unnecessary to treat trauma patients with the diagnosis of early-VAP.

METHODS

This retrospective cohort study included adult trauma patients with the diagnosis of VAP. The primary outcome was the presence of MRSA and/or P. aeruginosa in patients with early- and late-VAP. Secondary outcomes included the bacterial susceptibility of pathogens to methicillin, ampicillin/sulbactam, ceftriaxone, piperacillin/tazobactam, and cefepime. Intensive care unit (ICU) and hospital length of stay (LOS), ventilator-free days, and in-hospital mortality were also collected.

RESULTS

164 patients met inclusion criteria, and 208 organisms (n = 90 early vs n = 118 late) were identified by respiratory culture. The incidence of MRSA and P. aeruginosa in early-VAP was 7.7% (7/90) and 5.6% (5/90), respectively. The susceptibility of bacteria causing early-VAP to ampicillin/sulbactam and ceftriaxone was 73.3% (66/90) and 83.3% (75/90), respectively. Ventilator-free days at 30 days was similar between groups (P = .649). Patients with late-VAP spent more time in the ICU (P = .040); however, in-hospital mortality was higher in the early-VAP group (P = .012).

CONCLUSIONS

Ampicillin/sulbactam or ceftriaxone monotherapy did not provide reliable broad-spectrum coverage for early-VAP in our cohort. These findings highlight the importance of each institution performing a similar analysis to ensure adequate initial treatment of VAP.

Narrowing antibiotic spectrum of activity for trauma-associated pneumonia through the use of a disease-specific antibiogram

Background

Organism susceptibilities for trauma-associated pneumonia (TAP) differ from those in other patient populations, including the critically ill. The purpose of this study was to identify common organisms and their susceptibilities in the respiratory isolates of trauma patients diagnosed with pneumonia within the first 7 days of hospital admission, and to create a TAP-specific disease-state antibiogram to guide empiric antibiotic therapy in this patient population.

Methods

This study was a retrospective review of adult trauma patients with pneumonia admitted between September 1, 2015 and August 31, 2018. Patients included were diagnosed with and treated for pneumonia, with respiratory cultures drawn within the first 7 hospital-days; both culture-positive and culture-negative patients were included. Subgroup antibiograms were made for diagnosis made on days 1-3, 4-5, and 6-7.

Results

There were 131 patients included with a median age of 45; 85% were male, and 31% were illicit drug users. Most patients (63%) had ventilator-associated pneumonia, and most respiratory samples (77%) were obtained via bronchoalveolar lavage. Cultures were positive in 109 patients and negative in 22. There were 144 total isolates; 54% were Gram-negative bacteria. The most common Gram-negative pathogens were Haemophilus influenzae (16%) and Klebsiella pneumoniae (15%). The most common Gram-positive pathogen was Staphylococcus aureus; methicillin-resistant S. aureus (MRSA) constituted 8% of all isolates. With culture-negative patients counted as susceptible, ceftriaxone monotherapy and ceftriaxone+vancomycin susceptibilities were 85% and 94%, respectively. Susceptibilities to cefazolin, ampicillin/sulbactam, cefepime, piperacillin/tazobactam, and levofloxacin were 49%, 69%, 91%, 90%, and 92%, respectively. Illicit drug use and day of pneumonia diagnosis did not appreciably affect antibiotic susceptibilities.

Conclusions

For TAP diagnosed within the first 7 days of hospital admission, ceftriaxone monotherapy is adequate as empiric therapy, including in ventilated patients. The addition of vancomycin can be considered in patients with MRSA risk factors or who are critically ill.

Level of evidence

Level III, prognostic and epidemiological.

Trauma and Antimicrobial Resistance Are Independent Predictors of Inadequate Empirical Antimicrobial Treatment of Ventilator-Associated Pneumonia in Critically Ill Patients

Background: We aimed to assess independent risk factors for inadequate initial antimicrobial treatment (IAT) in critically ill patients with ventilator-associated pneumonia (VAP) treated in intensive care units (ICU) and to determine whether IAT is associated with adverse outcomes in patients with VAP. Patients and Methods: A prospective cohort study was performed and included 152 patients with VAP treated in an ICU for more than 48 hours. The main outcomes of interest were all-cause ICU mortality and VAP-related mortality. Other outcomes considered were: intra-hospital mortality, VAP-related sepsis, relapse, re-infection, length of stay in ICU (ICU LOS), and number of days on mechanical ventilation (MV). Results: One-third of patients (35.5%) received inadequate antimicrobial therapy. Trauma (odds ratio [OR], 3.55; 95% confidence interval [CI], 1.25-10.06) and extensively drug-resistant (XDR) causative agent (OR, 3.09; 95% CI, 1.23-7.74) were independently associated with inadequate IAT. Inadequate IAT was associated with a higher mortality rate (OR, 3.08; 95% CI, 1.30-7.26), VAP-related sepsis (OR, 2.39; 95% CI, 1.07-5.32), relapse (OR, 3.25; 95% CI, 1.34-7.89), re-infection (OR, 6.06; 95% CI, 2.48-14.77), and ICU LOS (β 4.65; 95% CI, 0.93-8.36). Acinetobacter spp., Pseudomonas aeruginosa and Klebsiella/Enterobacter spp. were the most common bacteria in patients with IAT and those with adequate antimicrobial therapy. Conclusions: This study demonstrated that inadequate IAT is associated with a higher risk of the majority of adverse outcomes in patients with VAP treated in ICUs. Trauma and XDR strains of bacteria are independent predictors of inadequate IAT of VAP in critically ill patients.

Impact of Invasive Quantitative Respiratory Cultures on Antimicrobial Therapy for Suspected Pneumonia in Trauma

BACKGROUND

Invasive quantitative respiratory cultures are generally not recommended because of a lack of demonstrated benefit. There is insufficient literature regarding specific populations such as trauma. The objective of this study was to evaluate the effect of invasive quantitative respiratory sampling on de-escalation to targeted antimicrobial therapy for the management of pneumonia in a trauma population.

METHODS

This was a single-center retrospective cohort study conducted at an American College of Surgeons-verified Level II Trauma Center in Nashville, TN. Adult patients admitted to the trauma service and diagnosed with pneumonia from July 2013 to August 2018 were divided into 2 groups: invasive quantitative respiratory sampling versus noninvasive respiratory sampling. The primary endpoint was rate of targeted antimicrobial therapy. Secondary endpoints included in-hospital mortality, antibiotic days of therapy, and frequency of discontinuation of antibiotics when quantitative cultures were below the diagnostic threshold.

RESULTS

A total of 88 patients were sampled, with 27 in the invasive quantitative group and 66 in the noninvasive group. There was no difference in rates of targeted therapy in patients with invasive quantitative sampling (17 [63%] vs. 35 [57%]; relative risk = 1.10; 95% confidence interval [0.76, 1.57]). No statistically significant differences were observed for in-hospital mortality (8 patients vs. 6 patients, p = .35) or antimicrobial days of therapy (10.3 ± 8.8 vs. 7.8 ± 3.6, p = .161). Only 2 patients (17%) had antibiotics withheld when below the diagnostic threshold.

CONCLUSIONS

Invasive quantitative respiratory sampling did not result in significant changes in targeted antibiotic therapy in a trauma population.

Incidence and Risk Factors Associated with Multi-Drug-Resistant Pathogens in a Critically Ill Trauma Population: A Retrospective Cohort Study

Background: Multi-drug resistance is considered a serious health threat particularly in the intensive care unit (ICU) setting. Studies evaluating multi-drug-resistant (MDR) pathogens in critically ill trauma patients are limited. The objectives were to describe the incidence of MDR, extensive-drug-resistant (XDR), and pan-drug-resistant (PDR) organism growth in ICU patients admitted with traumatic injuries and to identify any risk factors associated with MDR growth. Patients and Methods: This was a retrospective single-center cohort study of all ICU adult patients identified via the institution's trauma registry from January 1, 2016 to August 31, 2017. Patients were included if they had positive culture growth with susceptibility data taken during the index hospitalization. Patients were excluded if their cultures were drawn within 48 hours of emergency department triage. Study groups were defined based on the presence of at least one MDR pathogen during the index hospitalization. Results: A total of 2,578 charts were reviewed and 95 patients (mean age, 60 years; 66 males [69%]) with 201 total cultures were included. The majority of positive cultures were from respiratory (69%) and urinary (16%) sources. Of the 201 positive cultures, the majority of species identified was Enterobacteriaceae (47%), Staphylococcus (32%), Enterococcus (7%), Acinetobacter (5%), and Pseudomonas (3%). Of the 95 patients with positive cultures, the incidence of MDR, XDR, and PDR organisms was found to be 31%, 17%, and 0%, respectively. Augmented renal clearance (ARC) was the only risk factor associated with an increased risk for MDR organism growth (adjusted odds ratio 9.78, 95% confidence interval [CI] 2.56-37.41; p = 0.001). Conclusions: In this cohort of critically ill trauma patients, the incidence of an MDR pathogen occurred in 31% of patients. This is the first study to find an association of ARC and multi-drug resistance, which should be further validated as a potential cause for MDR organisms.

Pneumonia in Trauma Patients

Purpose of Review

This article reviews the new definitions of pneumonia, discusses risk factors for pneumonia among trauma patients, presents the latest evidence for prevention strategies, discusses the best ways to make the diagnosis, and reviews the microbiology and treatment for trauma patients with pneumonia.

Recent Findings

Pneumonia can be prevented by decreasing the duration of mechanical ventilation using daily paired spontaneous awakening and breathing trials, but not with early tracheostomy placement. Other useful prevention strategies include semirecumbent positioning and oral care. Mini-BAL is a sensitive and specific means of securing the diagnosis of pneumonia that does not require a physician to be present and is therefore especially useful in busy trauma centers.

Summary

Pneumonia is a frequent complication among trauma patients. Risk factors are largely unmodifiable. However, trauma centers can institute routine daily paired spontaneous awakening and breathing trials to decrease the duration of ventilation and incidence of pneumonia. Future research is needed to further characterize the microbiology of pneumonia among trauma patients.

Use of Gentamicin as Empiric Coverage for Ventilator-Associated Pneumonia: The "Con" Perspective

BACKGROUND

Gentamicin is used commonly as an empiric antibiotic prior to culture evidence in the treatment of ventilator-associated pneumonia (VAP) in surgical patients.

METHODS

The published literature on the use of gentamicin for empiric therapy in VAP was reviewed and in combination with the author's personal experience, an evaluation has been made about the indications for the use of this antibiotic in VAP.

RESULTS

Empiric gentamicin use appears to benefit less than 1% of patients in the treatment of presumptive VAP. The problematic pharmacokinetics of gentamicin use in this patient population combined with potential toxicity from the drug can be observed to yield greater risks than benefits in this clinical situation when published evidence is reviewed.

CONCLUSION

There is no definitive evidence to support empiric use of gentamicin in the treatment of VAP when evaluated on a cost-effective basis.

Multi-Drug-Resistant Gram-Negative Infections in Deployment-Related Trauma Patients

BACKGROUND

The contribution of multi-drug-resistant gram-negative bacilli infections (MDRGN-I) in patients with trauma is not well described. We present characteristics of MDRGN-Is among military personnel with deployment-related trauma (2009-2014).

PATIENTS AND METHODS

Data from the Trauma Infectious Disease Outcomes Study were assessed for infectious outcomes and microbial recovery. Infections were classified using standardized definitions. Gram-negative bacilli were defined as multi-drug-resistant if they showed resistance to ≥3 antibiotic classes or were producers of extended-spectrum β-lactamase or carbapenemases.

RESULTS

Among 2,699 patients admitted to participating U.S. hospitals, 913 (33.8%) experienced ≥1 infection event, of which 245 (26.8%) had a MDRGN-I. There were 543 MDRGN-I events (24.6% of unique 2,210 infections) with Escherichia coli (48.3%), Acinetobacter spp. (38.6%), and Klebsiella pneumoniae (8.4%) as the most common MDRGN isolates. Incidence of MDRGN-I was 9.1% (95% confidence interval [CI]: 8.0-10.2). Median time to MDRGN-I event was seven days with 75% occurring within 13 days post-trauma. Patients with MDRGN-Is had a greater proportion of blast injuries (84.1% vs. 62.5%; p < 0.0001), traumatic amputations (57.5% vs. 16.3%; p < 0.0001), and higher injury severity (82.0% had injury severity score ≥25 vs. 33.7%; p < 0.0001) compared with patients with either no infections or non-MDRGN-Is. Furthermore, MDRGN-I patients were more frequently admitted to the intensive care unit (90.5% vs. 48.5%; p < 0.0001), colonized with a MDRGN before infection (58.0% vs. 14.7%; p < 0.0001), and required mechanical ventilation (78.0% vs. 28.8% p < 0.0001). Antibiotic exposure before the MDRGN-I event was significantly higher across antibiotic classes except first generation cephalosporins and tetracyclines, which were very commonly used with all patients. Regarding outcomes, patients with MDRGN-Is had a longer length of hospitalization than the comparator group (53 vs. 18 days; p < 0.0001).

CONCLUSIONS

We found a high rate of MDRGN-I in our population characterized by longer hospitalization and greater injury severity. These findings inform treatment and infection control decisions in the trauma patient population.

Observations of resistance through minimum inhibitory concentrations trends for respiratory specimens of commonly isolated organisms

OBJECTIVE

The objective of this study was to determine minimum inhibitory concentration (MIC) trends among common bacterial organisms found in respiratory isolates in the trauma intensive care unit setting.

METHODS

In this retrospective observational study, MIC data was reviewed over a three year period from January 2009 to December 2011 for the three most frequently identified organisms isolated from respiratory specimens in a trauma intensive care unit along with corresponding hospital data.

RESULTS

The most frequently isolated bacterial species identified were Staphylococcus aureus (229 isolates), Pseudomonas aeruginosa (129 isolates), and Acinetobacter species (87 isolates) in the analysis within our institution from 2009-2011. There was considerable variability among the MIC trends for the analyzed organisms. For Pseudomonas isolates, observed sensitivities were as high as 100% for antibiotics ciprofloxacin and imipenem in 2009, but decreased over the next two years in 2010 and 2011. There was considerable variability among the MIC trends for Acinetobacter over the three year period for the antibiotics tested. The MIC data for most Staphylococcus aureus isolates over the three years were sensitive to vancomycin with little change in the observed MIC data.

CONCLUSION

The data reported is observational and indicates the need for future studies to establish a valid relationship of the MIC data over time in our institution particularly among our gram negative organisms, to monitor patterns of antimicrobial resistance.

Antimicrobial susceptibilities of respiratory pathogens in the surgical/trauma intensive care unit compared with the hospital-wide respiratory antibiogram in a level I trauma center

BACKGROUND

Unit-specific antibiograms have developed to guide clinicians to appropriate antibiotic choices for subsets of patients. The additional level of a unit- and respiratory-specific antibiogram for surgical and trauma patients defines key differences in susceptibility information for treating hospital-acquired pneumonia.

METHODS

This was a three-year, retrospective single-center study. A total of 729 positive respiratory specimens from 612 patients were analyzed using Quality Compass Pathfinder(®), the antibiotic-reporting software. Culture and susceptibility reports were compared for the surgical/trauma intensive care unit (S/TICU) and the general hospital (excluding the S/TICU but including the medical ICU [MICU]). Data were filtered to include those genera and organisms with a high association with hospital-acquired pneumonia: Acinetobacter, Citrobacter, Enterobacter, Escherichia coli, Haemophilus, Klebsiella, Neisseria, Pseudomonas, Staphylococcus, Stenotrophomonas, Streptococcus, and Serratia.

RESULTS

For gram-negative organisms, susceptibility differences were noted for Acinetobacter and Pseudomonas between the S/TICU and the rest of the hospital. In particular, Acinetobacter was significantly more susceptible to ciprofloxacin (86% vs. 43%; p<0.001), gentamicin (86% vs. 54%; p=0.001), imipenem-cilastatin (93% vs. 55%; p<0.001), trimethoprim-sulfamethoxazole (88% vs. 54%; p=0.001), and tobramycin (50% vs. 0; p=0.012). Pseudomonas isolates from the S/TICU were significantly more susceptible to aztreonam (83% vs. 68%; p=0.037), ciprofloxacin (86% vs. 69%; p=0.019), and imipenem-cilastatin (94% vs. 79%; p=0.01). For gram-positive organisms, Staphylococcus isolates from the S/TICU were significantly more susceptible to erythromycin (81% vs. 57%; p=0.007) and trimethoprim-sulfamethoxazole (98% vs. 91%; p=0.034) than were the hospital isolates.

CONCLUSIONS

For key respiratory pathogens, such as Pseudomonas, Acinetobacter, and Staphylococcus, surgical and trauma patients present greater susceptibility to several antibiotics. Although this information cannot be extrapolated to other institutions, it does provide a basis for comparable institutions to consider developing unit- and collection-site-specific antibiograms for infections that affect surgical/trauma patients commonly.

Differential impact of infection control strategies on rates of resistant hospital-acquired pathogens in critically ill surgical patients

BACKGROUND

There were two major outbreaks of multi-drug resistant Acinetobacter baumannii (MDRA) in our general surgery and trauma intensive care units (ICUs) in 2004 and 2011. Both required aggressive multi-faceted interventions to control. We hypothesized that the infection control response may have had a secondary benefit of reducing rates of methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus (VRE), and Clostridium difficile (C. diff).

METHODS

We analyzed data retrospectively from a prospective infection control database at a major university hospital and calculated the incidence rates of nosocomial MRSA, VRE, and C. diff before and after the two MDRA outbreaks (2004 and 2011) in the general surgery and trauma ICUs, and two unaffected control ICUs: thoracic surgery ICU and medical ICU. We tracked incidence rates in 6 mos segments for 24 mos per outbreak and created a composite variable of "any resistant pathogen" for comparison.

RESULTS

The incidence rates of "any resistant pathogen" were significantly lower in the general surgery ICU after both outbreaks (24 to 11 cases per 1000 patient days in 2004, p=0.045 and 7.7 ->4.0 cases per 1000 patient days in 2011, p=0.04). This did not persist after 6 mos. The trauma ICU's rate of "any resistant pathogen" did not change after either outbreak (16 ->16.5 cases per 1000 patient days in 2004, p=0.44 and 4.6 ->1.9 cases per 1000 patient days in 2011, p=0.41). The rates in the control ICUs were unchanged during the study periods.

CONCLUSIONS

Rates of resistant pathogens were lower in the general surgery ICU after response to MDRA outbreaks in both 2004 and 2011 although the rates increased again with time. There were no changes in rates of resistant pathogens in the trauma ICU after MDRA outbreaks in 2004 and 2011. Outbreak responses may have a differential impact in general surgery ICU versus trauma ICUs.

Infectious complications and mortality in an American acute care surgical service

BACKGROUND

Acute care surgery (ACS) services have evolved in an effort to provide 24-h surgical services for a wide array of general surgical emergencies. The formation of ACS services has been shown to improve outcomes and lead to more expeditious care. Despite the advances of ACS, the etiology and timing of patient mortality has yet to be described. We hypothesized that infectious complications occur more frequently in ACS patients that die during their hospitalization.

METHODS

A retrospective review of a local ACS service (non-trauma) registry was conducted. Demographic variables, admission and discharge data, and ICD-9 codes were collected. ICD-9 codes were used to identify patients with sepsis, shock, GI perforation, peritonitis, and other hospital acquired infections (urinary tract, bloodstream, and ventilator-associated pneumonias). Univariate and multivariate logistic regression analysis was performed to model the outcome of death.

RESULTS

1,329 patients were analyzed. 53 % were male with the mean age of 52 years and an average length of stay of 13 days. 106 (8 %) died while in the hospital. Of the patients who died, 34 (32 %) died within 7 days of admission. The majority of mortalities (56 %) occurred after hospital day 14. In ACS patients that died, there were significantly higher rates of sepsis, shock, peritonitis, urinary tract infections, and VAP. After adjustment; age, sepsis on admission, and shock on admission were associated with greater odds of death.

CONCLUSION

ACS patients with sepsis and shock have higher mortality rate than those patients without. The majority of ACS patient deaths occurred after hospital day 14. Further investigation and continued focus on preventing and rapidly treating infectious complications as they arise is warranted.

Locally derived versus guideline-based approach to treatment of hospital-acquired pneumonia in the trauma intensive care unit

BACKGROUND

Appropriate initial antibiotic therapy for presumed pneumonia in critically ill patients decreases the mortality rate. To achieve this goal, treatment guidelines developed by groups such as the American Thoracic Society (ATS) have been stressed. However, often overlooked is the importance of incorporating local microbiologic data into an empiric algorithm. Our hypothesis was that an empiric algorithm supported by our locally-driven analysis would predict more accurate coverage than one defined strictly by an unmodified guideline-driven approach.

METHODS

Retrospective review of all first hospital-acquired (HAP) and ventilator-associated pneumonia (VAP) pathogens in consecutive trauma intensive care unit (TICU) patients over 18 months. Microbiologic data were analyzed to update our TICU-specific empiric algorithm. The ATS guidelines define patients at risk for multidrug-resistant (MDR) organisms on the basis of standardized criteria and time since admission (early <5 days; late ≥5 days).

RESULTS

A total of 164 pathogens caused 117 pneumonias. For early coverage, ATS guidelines stress identification of MDR risks; these criteria failed to identify 8 of 13 (62%) early MDR pneumonias. For early HAP/VAP with no MDR risks, the ATS guidelines recommend monotherapy; susceptibility differed (49% to ciprofloxacin, 68% to ampicillin-sulbactam, 83% to ceftriaxone). A total of 15% of early pathogens were MDR gram-positive, so addition of vancomycin resulted in adequate predicted coverage of 100%, 79%, and 95% for ciprofloxacin, ampicillin-sulbactam, and ceftriaxone, respectively. For late HAP/VAP, ATS recommends regimens based on broad-spectrum drugs. Vancomycin with ciprofloxacin, cefepime, or piperacillin-tazobactam had predicted coverage of 95%, 94%, and 93%, respectively.

CONCLUSIONS

The empiric algorithm derived from analysis of local microbiologic data predicted significantly better coverage than one defined by an unmodified guideline-driven approach for early HAP/VAP. Our locally-derived TICU algorithm of ceftriaxone+vancomycin for early pneumonia and piperacillin-tazobactam+vancomycin for late pneumonia optimizes the adequacy of initial therapy. Understanding local patterns of pneumonia ensures the creation and maintenance of empiric algorithms that achieve the best clinical outcomes.