Empiric antimicrobial therapy for severe sepsis in the intensive care unit: In early, hit hard, out early

Common microbial isolates in an adult intensive care unit before and after its relocation and expansion

Objective: To describe the prevalence of common and clinically relevant microbial isolates before and after the migration of a 24-bed, open plan, adult intensive care unit (ICU) to a new extended design of 32 single rooms, supporting an expanded clinical oncology casemix while continuing all existing clinical services. Design: Retrospective, observational descriptive analysis covering the period 5 May 2014 to 4 May 2018 - the 2 years before and after the ICU relocation on 5 May 2016. Setting: A university-associated, tertiary teaching hospital and state trauma centre in Victoria, Australia. Patients: Adult ICU patients. Main outcome measures: Bacterial isolate frequency and incident rate ratios (IRRs) during the study period. Results: When compared with the old ICU, the incidence rates per 1000 occupied bed-days in the new ICU were lower for bacterial isolates overall (IRR, 0.88; 95% CI, 0.83-0.93), for coagulase-negative staphylococci (IRR, 0.64; 95% CI, 0.55-0.75) and for vancomycin-resistant enterococci (IRR, 0.50; 95% CI, 0.32-0.80). The incidence rates per 1000 occupied bed-days between ICU locations were unchanged for Staphylococcus aureus (IRR, 1.1; 95% CI, 0.91-1.3), extended-spectrum beta-lactamase-producing organisms (IRR, 1.4; 95% CI, 0.78-2.6) and carbapenemase-producing Enterobacterales (IRR, 0.85; 95% CI, 0.11-6.4). Conclusion: Within the limits of a before-after design and clinically directed sampling, relocation to a new ICU with single rooms and a growing oncological patient casemix was accompanied by no overall change in the apparent prevalence of the nosocomial pathogens S. aureus, extended-spectrum beta-lactamase-producing organisms or carbapenemase-producing Enterobacterales. These finding suggest that advanced physical infrastructure, including patient accommodation in single rooms, may play a role in overall safe delivery of critical care.

Mucosal surveillance cultures in predicting Gram-negative late-onset sepsis in neonatal intensive care units

This study aimed to examine the spectrum and time course of gut and nasopharyngeal colonization with Gram-negative micro-organisms, and to define the value of surveillance cultures in predicting late-onset sepsis in neonates admitted to neonatal intensive care units. Nasopharyngeal and rectal swabs were collected on admission and twice weekly thereafter in 278 neonates admitted within the first 72 h of life with risk factors of early-onset sepsis. Sterile body fluid cultures were obtained on admission and subsequently as clinically indicated. Approximately half of the rectal (693/1250, 55%) and nasopharyngeal (558/1153, 48%) samples but only 6% (32/555) of the sterile fluid samples in 26 patients were culture positive for Gram-negative organisms. In total, 2108 invasive and mucosal culture pairs were analysed. The overall sensitivity, specificity, and positive and negative predictive values of a mucosal sample to predict late-onset sepsis were 27%, 66%, 4% and 94%, respectively. Patients with pre-existing colonization with Klebsiella pneumoniae (P = 0.011), Klebsiella oxytoca (P = 0.002), Escherichia coli (P = 0.003), Stenotrophomonas spp. (P = 0.003) and Pseudomonas spp. (P ≤ 0.001) were more likely to develop late-onset sepsis. No such association was found for Acinetobacter baumannii, Serratia spp. or Enterobacter cloacae. In conclusion, routine mucosal cultures are inefficient for the prediction of Gram-negative late-onset sepsis in neonatal intensive care units. However, targeted screening for specific organisms in an outbreak (e.g. Klebsiella spp., E. coli, Stenotrophomonas spp. and Pseudomonas spp.) may offer an opportunity to improve infection control measures and enable timely initiation of appropriate antibiotic therapy.

Interpreting culture and susceptibility data in critical care: perks and pitfalls

PROBLEM

The need for immediate, effective antimicrobial therapy in the critical care patient must be tempered by approaches which simultaneously minimize emergence of antimicrobial resistance. Ideally, therapy will successfully resolve clinical signs of infection, while eradicating infecting pathogens such that the risk of resistance is avoided. Increasing limitations associated with empirical antimicrobial choices direct the need for culture and susceptibility data as a basis of therapy. Even so, such in vitro data should be utilized within its limitations.

OBJECTIVES

To demonstrate the attributes and limitations of patient and population culture and susceptibility (pharmacodynamic) data in the selection of antimicrobial drugs and to demonstrate the design of individualized dosing regimens based on integration of pharmacodynamic (PD) and pharmacokinetic (PK) data.

DIAGNOSIS

Limitations in culture and susceptibility testing begin with sample collection and continue through drug selection and dose design. Among the challenges in interpretation is discrimination between pathogens and commensals. Properly collected samples are critical for generation of data relevant to the patient's infection. Data are presented as minimum inhibitory concentrations (MICs). The MIC facilitate selection of the most appropriate drug, particularly when considered in the context of antimicrobial concentrations achieved in the patient at a chosen dose. Integration of MIC data with key PK data yields the C(max):MIC important to efficacy of concentration-dependent drugs and T>MIC, which guides use of time-dependent drugs. These indices are then used to design dosing regimens that are more likely to kill all infecting pathogens. In the absence of patient MIC data, population data (eg, MIC(90)) may serve as a reasonable surrogate.

CONCLUSIONS

Properly collected, performed, and interpreted culture and susceptibility data are increasingly important in the selection of and design of dosing regimens for antimicrobial drugs. Integration of PK and PD data as modified by host and microbial factors supports a hit hard, exit fast approach to therapy that will facilitate efficacy while minimizing resistance.