Utility of ampicillin-sulbactam for empiric treatment of ventilator-associated pneumonia in a trauma population

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.

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.

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

BACKGROUND

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

PATIENTS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Ampicillin/sulbactam: its potential use in treating infections in critically ill patients

The purpose of this paper was to review the potential utility of ampicillin/sulbactam (SAM) as a therapy for serious infections in critically ill patients. Data for this review were identified by searches of PubMed and of the reference lists of the included articles. We found that SAM appears to have a number of characteristics that support its use in the treatment of serious infections in critically ill patients. SAM demonstrates extensive penetration into many infection sites, supporting its use in a wide range of infection types. Microbiologically, sulbactam has strong intrinsic antibiotic activity against multidrug-resistant (MDR) bacteria, including Acinetobacter baumannii, which supports its use for the treatment of infections mediated by this pathogen. Of some concern, there have been reports showing a decline in susceptibility of some bacteria to SAM. As such, use of lower doses (4/2g/day), particularly for MDR A. baumannii, has been linked with a 30% reduced success rate in critically ill patients. The therapeutic challenges for ensuring achievement of optimal dosing of SAM result partly from bacterial susceptibility but also from the pharmacokinetic (PK) alterations common to β-lactam agents in critical illness. These PK changes are likely to reduce the ability of standard dosing to achieve the concentrations observed in non-critically ill patients. Optimisation of therapy may be more likely with the use of higher doses, administration by 4h infusion or by combination therapy, particularly for the treatment of infections caused by MDR pathogens.