Persistent gram-negative bacteremia. Observations in twenty patients

Serratia Marcescens, a Rare and Devastating Cause of Endocarditis: A Case Report and Review of the Literature

Serratia marcescens is a gram-negative bacillus that is an opportunistic agent in respiratory tract infections, urinary tract infections, and septicemia. It is rarely a cause of infective endocarditis, but in cases of endocarditis, it follows a rapid and devastating course.

A previously healthy female in her mid-50s presented with fever, abdominal pain, right lower extremity pain, and diarrhea. Blood cultures were positive for S. marcescens, and additional evaluation revealed infarction in the spleen and kidneys, raising concern for endocarditis with associated embolic phenomena. The patient was subsequently found to have an embolus in the right popliteal artery and underwent a right popliteal thromboembolectomy. Antimicrobial therapy with cefepime and gentamicin was begun. A transesophageal echocardiogram revealed a large, mobile mitral valve vegetation. Care was complicated by intracranial hemorrhage, and the decision was made to withdraw care.

A review of the databases Embase and PubMed revealed 63 additional cases of S. marcescens endocarditis. Analysis of these cases demonstrated a preponderance of aortic and mitral valve involvement, not tricuspid valve involvement, despite a risk factor of intravenous drug use in over 60% of cases. Mortality was 50%, and sequelae such as congestive heart failure and renal insufficiency occurred in the majority of survivors. In conclusion, S. marcescens is a rare but devastating cause of endocarditis with a primary risk factor of intravenous drug use but with a predilection for left-sided valvular lesions, not right-sided lesions.

Follow-Up Blood Culture Practices for Gram-Negative Bloodstream Infections in Immunocompromised Hosts at a Large Academic Medical Center

The role of follow-up blood cultures (FUBC) in gram-negative (GN) bloodstream infections (BSI) to improve clinical outcomes remains controversial, especially among immunocompromised patients. Among 139 patients, FUBCs were common (117, 84.2%); however, positive FUBCs were rare (3, 2.6%). Only presence of fever was associated with positive FUBC.

Microbial Cell-Free DNA Identifies Etiology of Bloodstream Infections, Persists Longer Than Conventional Blood Cultures, and its Duration of Detection is Associated with Metastatic Infection in Patients with Staphylococcus aureus and Gram-Negative Bacteremia

BACKGROUND

Microbial cell-free DNA (mcfDNA) sequencing of plasma can identify presence of a pathogen in a host. This study evaluated the duration of pathogen detection by mcfDNA sequencing vs. conventional blood culture in patients with bacteremia.

METHODS

Blood samples from patients with culture-confirmed bloodstream infection were collected within 24 hours of the index positive blood culture and 48 to 72 hours thereafter. mcfDNA was extracted from plasma and next-generation sequencing (NGS) applied. Reads were aligned against a curated pathogen database. Statistical significance was defined with Bonferroni adjustment for multiple comparisons (p < 0.0033).

RESULTS

A total of 175 patients with Staphylococcus aureus bacteremia (SAB; n=66), Gram-negative bacteremia (GNB; n=74), or non-infected controls (n=35) were enrolled. The overall sensitivity of mcfDNA sequencing compared to index blood culture was 89.3% (125/140) and the specificity was 74.3%. Among patients with bacteremia, pathogen specific mcfDNA remained detectable for significantly longer than conventional blood cultures (median 15 days vs. 2 days; p<0.0001). Each additional day of mcfDNA detection significantly increased the odds of metastatic infection (Odds Ratio [OR]: 2.89; 95% Confidence Interval [CI]: 1.53-5.46; p=0.0011).

CONCLUSIONS

Pathogen mcfDNA identified the bacterial etiology of bloodstream infection for a significantly longer interval than conventional cultures, and its duration of detection was associated with increased risk for metastatic infection. mcfDNA could play a role in the diagnosis of partially treated endovascular infections.

Impact of duration of antibiotic therapy in central venous catheter-related bloodstream infection due to Gram-negative bacilli

BACKGROUND

A progressive increase in the incidence of catheter-related bloodstream infection (CRBSI) due to Gram-negative bacilli (GNB) has been reported. Current guidelines recommend antibiotic treatment for at least 7-14 days, although the supporting evidence is limited.

METHODS

We performed a retrospective single-centre study including all patients with a definite diagnosis of GNB CRBSI from January 2012 to October 2018 in which the central venous catheter (CVC) was removed. The occurrence of therapeutic failure [clinical failure (persistence of symptoms and laboratory signs of infection), microbiological failure (persistent bacteraemia or relapse) and/or all-cause 30 day mortality] was compared between episodes receiving short [≤7 days (SC)] or long courses [>7 days (LC)] of appropriate antibiotic therapy following CVC removal.

RESULTS

We included 54 GNB CRBSI episodes with an overall rate of therapeutic failure of 27.8% (15/54). Episodes receiving SC therapy were more frequently due to MDR GNB [60.9% (14/23) versus 34.5% (10/29); P = 0.058] and had higher Pitt scores [median (IQR) 1 (0-4) versus 0 (0-2); P = 0.086]. There were no significant differences in the rate of therapeutic failure between episodes treated with SC or LC therapy [30.4% (7/23) versus 27.6% (8/29); OR 1.15; 95% CI 0.34-3.83; P = 0.822]. The use of SCs was not associated with increased odds of therapeutic failure in any of the exploratory models performed.

CONCLUSIONS

The administration of appropriate antibiotic therapy for ≤7 days may be as safe and effective as longer courses in episodes of GNB CRBSI once the CVC has been removed.

Complement levels in patients with bloodstream infection due to Staphylococcus aureus or Gram-negative bacteria

The complement system is a vital component of the innate immune system, though its role in bacteremia is poorly understood. We present complement levels in Staphylococcus aureus bacteremia (SAB) and Gram-negative bacteremia (GNB) and describe observed associations of complement levels with clinical outcomes. Complement and cytokine levels were measured in serum samples from 20 hospitalized patients with SAB, 20 hospitalized patients with GNB, 10 non-infected hospitalized patients, and 10 community controls. C5a levels were significantly higher in patients with SAB as compared to patients with GNB. Low C4 and C3 levels were associated with septic shock and 30-day mortality in patients with GNB, and elevated C3 was associated with a desirable outcome defined as absence of (1) septic shock, (2) acute renal failure, and (3) death within 30 days of bacteremia. Low levels of C9 were associated with septic shock in patients with GNB but not SAB. Elevated IL-10 was associated with increased 30-day mortality in patients with SAB. Complement profiles differ in patients with SAB and those with GNB. Measurement of IL-10 in patients with SAB and of C4, C3, and C9 in patients with GNB may help to identify those at higher risk for poor outcomes.

Follow-up blood cultures in Gram-negative bacilli bacteremia: are they needed for critically ill patients?

BACKGROUND

Gram-negative bacilli bacteremias (GNB-Bs) represent a major cause of morbidity and mortality in Intensive Care Unit (ICU) patients. Aim of this study was to investigate the role of follow-up blood cultures (FUBCs) and the clinical significance of persistent bacteremia (PB) in these settings.

METHODS

We retrospectively analyzed clinical data and outcome of GNB-Bs that occurred in ICU patients over a span of 1 year. In particular we sought information on development and clinical details of PB, defined as repeatedly positive FUBCs after ≥96 hours of appropriate antibiotic treatment and ≥48 hours after removal of endovascular devices.

RESULTS

Among 307 ICU patients, 69 (22.4%) developed 107 GNB-Bs. Of these, 78 (73%) could be eventually analyzed: 50 of 78 (64.1%) were non-PBs from 26 patients and 28 of 78 (35.9%) were PBs from 23 patients. Duration of fever and bacteremia, time to procalcitonin normalization and weaning from vasopressors were longer in episodes of PBs than non-PBs (P=0.04, P<0.001, P=0.02 and P=0.004, respectively). Primary bacteremia was more frequent in non-PBs than in PBs (29 of 50, 58% vs. 3/28, 10.7%, P=0.0001), whereas septic thrombus infection (STI) was the source of infection in 14 of 28 (50%). Finally, clinical features and 30-day mortality did not differ between patients with PB and those who developed only non-PB episodes.

CONCLUSIONS

Among our ICU patients, more than one third of GNB-Bs for which FUBCs were performed resulted PB. This condition is often associated with the presence of STI; therefore, FUBCs seem useful for the optimal management of GNB in this clinical setting.

Timing of follow-up blood cultures for community-onset bacteremia

Bacteremia is associated with high morbidity and mortality, but the utility and optimal timing of follow-up blood cultures (FUBCs) remain undefined. To assess the optimal timing of FUBCs related to appropriate antibiotic therapy (AAT), adults with community-onset bacteremia and FUBCs after bacteremia onset were retrospectively studied during the 6-year period in two hospitals. Based on the time gap between the initiation of AAT and FUBC sampling, 1,247 eligible patients were categorized as FUBCs prior to AAT (65 patients, 5.2%), 0–3 days (202, 16.2%), 3.1–6 days (470, 37.7%), 6.1–9 days (299, 24.0%), and ≥9 days (211, 16.9%) after AAT. The prognostic impact of the growth of the same bacteria in FUBCs on 30-day mortality was evidenced only in patients with FUBCs at 3.1–6 days after AAT (adjusted odds ratio [AOR], 3.75; P < 0.001), not in those with FUBCs prior to AAT (AOR, 2.86; P = 0.25), 0–3 days (AOR, 0.39; P = 0.08), 6.1–9 days (AOR, 2.19; P = 0.32), and ≥9 days (AOR, 0.41; P = 0.41) of AAT, after adjusting independent factors of 30-day mortality recognized by the multivariable regression in each category. Conclusively, persistent bacteremia in FUBCs added prognostic significance in the management of adults with community-onset bacteremia after 3.1–6 days of AAT.

Carbapenem sparing in the management of post-transrectal prostate biopsy bacteraemia

BACKGROUND

Sepsis following transrectal ultrasound (TRUS)-guided prostate biopsy is a major complication. With the emergence of multidrug-resistant organisms, empirical use of carbapenem antibiotics has been increasing. This study, conducted in the Illawarra Shoalhaven Local Health District (ISLHD), Australia, quantifies how much we can spare carbapenem use.

METHODS

A retrospective audit of patients who underwent TRUS prostate biopsy and were admitted post-operatively with proven bacteraemia between January 2007 and April 2016.

RESULTS

Of 2719 TRUS procedures, 50 (1.84%) cases had bacteraemia. The most common isolate was Escherichia coli in 44 of 50 (88%) of which six of 50 (12%) were extended-spectrum beta-lactamase (ESBL)-producing. Sixteen different empirical antimicrobial regimens were used, to which 42 of 50 (84%) of isolates were susceptible. Eight (16%) isolates were resistant to the chosen empiric combination, with five switched over to appropriate treatment once antimicrobial sensitivity results became available. Empirical carbapenem was utilized in 12 of 50 (24%) patients with only two of the ESBL isolates covered. A further 10 of 50 patients received carbapenems during their admission. Carbapenems could have been avoided in 18 of 22 (82%). A total of 86% of organisms (n = 43) were susceptible to the combination of amoxicillin-clavulanate and gentamicin.

CONCLUSION

Although the rates of bacteraemia with ESBL-producing organisms post-TRUS biopsy are increasing, use of carbapenem-free combination antimicrobials as empirical therapy appears to be safe and effective in our setting. Clinicians can utilize local resistance patterns to inform targeted and appropriate therapy for septic patients.

Utility of follow-up blood cultures for Gram-negative rod bacteremia in children

Persistent Gram-negative rod (GNR) bacteremia is uncommon under appropriate antibiotic therapy. A recent study showed that follow-up blood cultures (FUBCs) to confirm clearance 24-48 h after initiation of antibiotics, added little value in the management of GNR bacteremia in adults. However, the utility of FUBC in children is still unknown. We retrospectively reviewed the microbiology database to identify children aged <18 years with GNR bacteremia. Clinical information including gender, age, underlying diseases, presence of central venous line (CVC), source of bacteremia, and organisms was extracted from medical records. FUBCs for 99 episodes of GNR bacteremia in children became positive in 21%, which led to intervention in 57% of the episodes. In multivariate analysis between FUBC positive (n = 21) and negative (n = 78) groups, presence of CVC (n = 18, 86% vs n = 38, 49%, P = 0.001) and resistance to empirical antibiotics (n = 3, 14% vs n = 4, 5%, P = 0.04) were independently associated with positive FUBCs. Interestingly, no positive FUBC was observed in cases due to UTI (n = 13). Contrary to findings in adults, FUBC may still be useful in the management of GNR bacteremia in children.

Follow-up Blood Cultures in Gram-Negative Bacteremia: Are They Needed?

Background

Bloodstream infections remain a major cause of morbidity and mortality. Gram-negative bacilli (GNB) bacteremia is typically transient and usually resolves rapidly after the initiation of appropriate antibiotic therapy and source control. The optimal duration of treatment and utility of follow-up blood cultures (FUBC) have not been studied in detail. Currently, the management of gram-negative bacteremia is determined by clinical judgment. To investigate the value of repeat blood cultures, we analyzed 500 episodes of bacteremia to determine frequency of FUBC and identify risk factors for persistent bacteremia.

Methods

Of 500 episodes of bacteremia, we retrospectively analyzed 383 (77%) that had at least 1 FUBC. We sought information regarding presumed source of bacteremia, antibiotic status at the time of FUBC, antibiotic susceptibility, presence of fever, comorbidities (intravenous central lines, urinary catheters, diabetes mellitus, AIDS, end-stage renal disease, and cirrhosis), need for intensive care, and mortality.

Results

Antibiotic use did not affect the rate of positivity of FUBC, unless bacteria were not sensitive to empiric antibiotic. Fever on the day of FUBC was associated with higher rates of positive FUBC for gram-positive cocci (GPC) but not GNB. Mortality and care in the intensive care unit were not associated with positive FUBC. Seventeen FUBC and 5 FUBC were drawn for GNB and GPC to yield 1 positive result.

Conclusions

FUBC added little value in the management of GNB bacteremia. Unrestrained use of blood cultures has serious implications for patients including increased healthcare costs, longer hospital stays, unnecessary consultations, and inappropriate use of antibiotics.

Severe sepsis and septic shock: the role of gram-negative bacteremia

Abstract Although Gram-negative bacteria have often been implicated in the pathogenesis of severe sepsis and septic shock, how they trigger these often lethal syndromes is uncertain. In particular, the role played by blood-borne bacteria is controversial. This review considers two alternatives. In the first, circulating Gram-negative bacteria induce toxic reactions directly within the vasculature; in the second, the major inflammatory stimulus occurs in local extravascular sites of infection and circulating bacteria contribute little to inducing toxic responses. Evidence for each alternative is found in the literature. Bacteremia and severe sepsis are not so closely linked that the most striking cases can be a model for the rest. Intravascular and extravascular triggers may warrant different approaches to prevention and therapy.

Multiply high-level-aminoglycoside-resistant enterococci isolated from patients in a university hospital

Enterococci isolated from different body sites were tested for high-level gentamicin resistance. A total of 259 enterococcal isolates were screened for resistance (MIC, greater than 2,000 micrograms/ml) by a broth-tube method. Thirty-nine (15.1%) were found to exhibit resistance and were confirmed by agar screening (1,000 micrograms/ml) and agar dilution MIC determinations. The majority of isolates also showed high-level resistance to kanamycin and streptomycin. The remaining isolates showed high-level resistance to gentamicin and kanamycin but not streptomycin. Synergy testing of several isolates confirmed the correlation between lack of synergy and high-level resistance. A retrospective clinical review was performed. Most patients had a source of definite or likely infection (79%). Serious infections such as endocarditis or meningitis were not observed during the course of this study. Retrospective clinical data suggest that in cases not involving endocarditis or meningitis, neither infection refractory to therapy nor relapse of infection is a common sequela of infection with gentamicin-resistant enterococci in hospitalized patients.

Role of a cefoxitin-inducible beta-lactamase in a case of breakthrough bacteremia

Development of resistance during therapy with cefamandole contributes to treatment failure. A simple cefoxitin disk test was recently described which detects a cefamandole-active inducible beta-lactamase not otherwise detectable with cefamandole as the inducer. A case of breakthrough Enterobacter bacteremia due to selection of a resistant subpopulation is reported in an immunocompromised patient. The use of this simple disk test in selected clinical cases is advocated.

Simultaneous antibiotic levels in "breakthrough" gram-negative rod bacteremia

Of 237 cases of gram-negative rod bacteremia observed at the UCLA Medical Center during a 12 month period, 52 (22 per cent) occurred while the patient was receiving antibiotics which inhibited the infecting organism by disc diffusion tests. One half of the plasma samples available from 42 such patients with "breakthrough" bacteremia had subinhibitory circulating antibiotic levels when cultures were positive. Sepsis documented within 72 hours of initiation of therapy was usually due to antibiotic-sensitive Esch. coli and was associated with inadequate antibiotic levels; the patient was usually treated with a penicillin or cephalosporin. The source of bacteremia was most frequently the urinary tract or the biliary tree. In contrast, sepsis occurring more than 72 hours after the administration of antibiotics was frequently caused by multiple antibiotic-resistant Esch. coli in patients treated with gentamicin in adequate dosage and was associated with leukopenia or undrained purulent collections. Therapy ultimately failed in 20 cases (48 per cent): in early "breakthrough" bacteremia, failure was associated with subinhibitory antibiotic levels, and in late "breakthrough" bacteremias with inadequate drainage or impaired host defenses.

Metastatic infection secondary to genitourinary tract sepsis

Metastatic infections arising from sepsis in the genitourinary tract are reviewed in 175 cases, including five in which we treated the patients. The skeleton was the most common site of metastasis (59 per cent). The endocardium was next most frequently involved (28 per cent). Gram-negative organisms were implicated in less than two-thirds of the cases (59 per cent). Impaired host defense mechanisms were noted in 25 per cent of the patients experiencing metastatic infections. The lower urinary tract was the source of metastasis in 75 per cent of the patients, particularly after urologic manipulation in men. Women were more likely to experience metastatic infection from the upper urinary tract. Anatomic and pathologic considerations explaining these sex differences are presented.