Simone Ambretti

Predictors of Mortality in Bloodstream Infections Caused by Klebsiella pneumoniae Carbapenemase–Producing K. pneumoniae: Importance of Combination Therapy

BACKGROUND The spread of Klebsiella pneumoniae (Kp) strains that produce K. pneumoniae carbapenemases (KPCs) has become a significant problem, and treatment of infections caused by these pathogens is a major challenge for clinicians. METHODS In this multicenter retrospective cohort study, conducted in 3 large Italian teaching hospitals, we examined 125 patients with bloodstream infections (BSIs) caused by KPC-producing Kp isolates (KPC-Kp) diagnosed between 1 January 2010 and 30 June 2011. The outcome measured was death within 30 days of the first positive blood culture. Survivor and nonsurvivor subgroups were compared to identify predictors of mortality. RESULTS The overall 30-day mortality rate was 41.6%. A significantly higher rate was observed among patients treated with monotherapy (54.3% vs 34.1% in those who received combined drug therapy; P = .02). In logistic regression analysis, 30-day mortality was independently associated with septic shock at BSI onset (odds ratio [OR]: 7.17; 95% confidence interval [CI]: 1.65-31.03; P = .008); inadequate initial antimicrobial therapy (OR: 4.17; 95% CI: 1.61-10.76; P = .003); and high APACHE III scores (OR: 1.04; 95% CI: 1.02-1.07; P < .001). Postantibiogram therapy with a combination of tigecycline, colistin, and meropenem was associated with lower mortality (OR: 0.11; 95% CI: .02-.69; P = .01). CONCLUSIONS KPC-Kp BSIs are associated with high mortality. To improve survival, combined treatment with 2 or more drugs with in vitro activity against the isolate, especially those also including a carbapenem, may be more effective than active monotherapy.

Infections caused by KPC-producing Klebsiella pneumoniae: differences in therapy and mortality in a multicentre study

OBJECTIVES Infections caused by Klebsiella pneumoniae (Kp) carbapenemase (KPC)-producing strains of Kp have become a significant threat in recent years. To assess their outcomes and identify risk factors for 14 day mortality, we conducted a 4 year (2010-13) retrospective cohort study in five large Italian teaching hospitals. METHODS The cohort included 661 adults with bloodstream infections (BSIs; n = 447) or non-bacteraemic infections (lower respiratory tract, intra-abdominal structure, urinary tract or other sites) caused by a KPC-Kp isolate. All had received ≥48 h of therapy (empirical and/or non-empirical) with at least one drug to which the isolate was susceptible. RESULTS Most deaths occurred within 2 weeks of infection onset (14 day mortality: 225/661, 34.1%). Logistic regression analysis identified BSI (OR, 2.09; 95% CI, 1.34-3.29), presentation with septic shock (OR, 2.45; 95% CI, 1.47-4.08), inadequate empirical antimicrobial therapy (OR, 1.48; 95% CI, 1.01-2.18), chronic renal failure (OR, 2.27; 95% CI, 1.44-3.58), high APACHE III score (OR, 1.05; 95% CI, 1.04-1.07) and colistin-resistant isolates (OR, 2.18; 95% CI, 1.37-3.46) as independent predictors of 14 day mortality. Combination therapy with at least two drugs displaying in vitro activity against the isolate was associated with lower mortality (OR, 0.52; 95% CI, 0.35-0.77), in particular in patients with BSIs, lung infections or high APACHE III scores and/or septic shock at infection onset. Combinations that included meropenem were associated with significantly higher survival rates when the KPC-Kp isolate had a meropenem MIC of ≤8 mg/L. CONCLUSIONS KPC-Kp infections are associated with high mortality. Treatment with two or more drugs displaying activity against the isolate improves survival, mainly in patients who are critically ill.

In Vivo Emergence of Colistin Resistance in Klebsiella pneumoniae Producing KPC-Type Carbapenemases Mediated by Insertional Inactivation of the PhoQ/PhoP mgrB Regulator

ABSTRACT Colistin is one of the few agents that retain activity against extensively drug-resistant strains of Klebsiella pneumoniae producing KPC-type carbapenemases (KPC-KP). However, resistance to colistin is increasingly reported among KPC-KP. Comparative genomic analysis of a pair of sequential KPC-KP isolates from the same patient including a colistin-susceptible isolate (KKBO-1) and a colistin-resistant isolate (KKBO-4) selected after colistin exposure revealed that insertional inactivation of the mgrB gene, encoding a negative regulator of the PhoQ/PhoP signaling system, is a genetic mechanism for acquired colistin resistance. The role of mgrB inactivation in acquired colistin resistance was confirmed by complementation experiments with wild-type mgrB, which restored colistin susceptibility in KKBO-4, and by construction of an mgrB deletion mutant from KKBO-1, which exhibited a colistin-resistant phenotype. Insertional mgrB inactivation was also detected in 60% of colistin-resistant mutants selected from KKBO-1 in vitro, following plating on colistin-containing medium, confirming the role (although not unique) of this mechanism in the emergence of acquired colistin resistance. In colistin-resistant mutants carrying insertional inactivation or deletion of the mgrB gene, upregulated transcription of phoP, phoQ, and pmrK (which is part of the pmrHFIJKLM operon) was detected. These findings confirmed the MgrB regulatory role in K. pneumoniae and were in agreement with the known association between upregulation of the PhoQ/PhoP system and activation of the pmrHFIJKLM operon, which eventually leads to resistance to polymyxins by modification of the lipopolysaccharide target.

In Vivo Evolution to Colistin Resistance by PmrB Sensor Kinase Mutation in KPC-Producing Klebsiella pneumoniae Is Associated with Low-Dosage Colistin Treatment

ABSTRACT Colistin is a key drug for the treatment of infections caused by extensively drug-resistant strains of Enterobacteriaceae producing carbapenemases. However, the emergence of colistin resistance is being increasingly reported, especially among Klebsiella pneumoniae strains producing KPC-type carbapenemases (KPC-KP). In this work, we investigated colistin-susceptible (KPB-1) and colistin-resistant (KPB-2) sequential isolates obtained from a patient with a KPC-KP infection before and after low-dosage colistin treatment, respectively. By using a next-generation sequencing approach and comparative genomic analysis of the two isolates, we detected in KPB-2 a nonsynonymous nucleotide substitution in the gene encoding the PmrB sensor kinase, resulting in a leucine-to-arginine substitution at amino acid position 82. Compared with KPB-1, KPB-2 exhibited upregulated transcription of pmrA and of pmrK, which is part of the pmrHFIJKLM operon responsible for modification of the colistin lipopolysaccharide target. Complementation with wild-type pmrB in KPB-2 restored colistin susceptibility and reduced the transcription of pmrA and pmrK to basal levels, while expression of PmrBL82R in KPB-1 did not alter colistin susceptibility or upregulate pmrA and pmrK expression, confirming the dominance of wild-type PmrB versus the PmrBL82R mutant. The present results indicated that PmrB mutations mediating colistin resistance may be selected during low-dosage colistin treatment. The colistin-resistant phenotype of KPB-2 was stable for up to 50 generations in the absence of selective pressure and was not associated with a significant fitness cost in a competition experiment.

Klebsiella pneumoniae bloodstream infection: epidemiology and impact of inappropriate empirical therapy.

AbstractMultidrug resistance associated with extended-spectrum beta-lactamase (ESBL) and Klebsiella pneumoniae carbapenemase (KPC) among K. pneumoniae is endemic in southern Europe. We retrospectively analyzed the impact of resistance on the appropriateness of empirical therapy and treatment outcomes of K. pneumoniae bloodstream infections (BSIs) during a 2-year period at a 1420-bed tertiary-care teaching hospital in northern Italy. We identified 217 unique patient BSIs, including 92 (42%) KPC-positive, 49 (23%) ESBL-positive, and 1 (0.5%) metallo-beta-lactamase-positive isolates. Adequate empirical therapy was administered in 74% of infections caused by non-ESBL non-KPC strains, versus 33% of ESBL and 23% of KPC cases (p < 0.0001). To clarify the impact of resistance on BSI treatment outcomes, we compared several different models comprised of non-antibiotic treatment-related factors predictive of patients’ 30-day survival status. Acute Physiology and Chronic Health Evaluation (APACHE) II score determined at the time of positive blood culture was superior to other investigated models, correctly predicting survival status in 83% of the study cohort. In multivariate analysis accounting for APACHE II, receipt of inadequate empirical therapy was associated with nearly a twofold higher rate of death (adjusted hazard ratio 1.9, 95% confidence interval 1.1–3.4; p = 0.02). Multidrug-resistant K. pneumoniae accounted for two-thirds of all K. pneumoniae BSIs, high rates of inappropriate empirical therapy, and twofold higher rates of patient death irrespective of underlying illness.

Correlation of high-risk human papillomavirus genotypes persistence and risk of residual or recurrent cervical disease after surgical treatment

The evidence on genotype‐specific risk in women infected with human papillomavirus (HPV) with normal cytology and the importance of the distinction of high‐risk (HR)‐HPV genotypes in the management of low‐grade lesions suggest that the distinction of HR‐HPV genotypes has the potential to improve the follow‐up of patients treated for high‐grade cervical lesions. The aims of this study were to define the persistence of the different HR‐HPV in the follow‐up of surgical treated women, to detect the changes of genotypes from the pre‐ to the post‐operative status, and to evaluate whether genotype‐specific persistence can predict the development of residual or recurrent disease during the follow‐up. HR‐HPV detection and genotyping was carried out by the Linear Array HPV Genotyping Test® on cervical cytological samples from 72 women treated by surgery. The 6‐month post‐operative HPV status was correlated with the pre‐operative HPV genotype and with the residual or recurrent disease within 24 months. It was observed that the residual or recurrent disease in women with persistence of HPV 16 and/or HPV 18 was higher (82.4%) than in women with persistence of at least one HR‐HPV type of group 2 (HPV 31, 33, 35, 45, 52, and 58) (66.7%) and at least one type of group 3 (HPV 39, 51, 56, 59, 68, 26, 53, 66, 73, and 82) (14.3%). These data defined HR‐HPV groups for the risk of progression of disease and suggested that the identification of persistent infection with different HR‐HPV genotypes has the potential to improve the management of these patients. J. Med. Virol. 80:1434–1440, 2008.

Epidemiology and outcomes of bloodstream infection in patients with cirrhosis

BACKGROUND & AIMS Bloodstream infections (BSIs) in cirrhotic patients are 10-fold more common than in non-cirrhotic patients and increasingly caused by resistant pathogens. We examined 162 BSI episodes in cirrhotic patients to describe the etiology and risk factors for 30-day mortality. METHODS We retrospectively analyzed all consecutive BSIs in patients with liver cirrhosis at our 1350-bed teaching hospital (January 2008 to June 2012). Cox-proportional hazard regression was used to analyze the impact of disease and treatment-related variables on the crude 30-day mortality. RESULTS BSI episodes were identified in 162 patients, including 29 mixed infections. Most of episodes were classified as hospital acquired or healthcare associated (93%). Gram-negative bacteria (GNB), Gram-positive bacteria and Candida spp. caused 64%, 38%, and 10% of episodes, respectively. GNB were classified as multi-drug resistant (MDR) and extensively drug resistant (XDR) in 25% and 21% of cases, respectively. The overall crude 30-day mortality rate was 29%. Four risk factors were independently associated with 30-day crude mortality: worsening of MELD score from baseline (the last MELD score available in the 2 weeks prior BSI) to that at BSI onset (HR 1.11 per point increase, 95% CI 1.07-1.15, p<0.0001), spontaneous bacterial peritonitis as BSI source (HR 4.42, 2.04-9.54, p=0.002), sepsis grading (HR 2.18, 1.39-3.43, p=0.0007), and inappropriate antibiotic therapy within 24h from blood cultures (HR 2.82, 1.50-5.41, p=0.002). CONCLUSION An increasing proportion of BSIs in cirrhotic patients are caused by resistant GNB and Candida spp. Accurate evaluation of risk factors for mortality may improve early appropriate therapeutic management.

In vitro activity and post-antibiotic effects of colistin in combination with other antimicrobials against colistin-resistant KPC-producing Klebsiella pneumoniae bloodstream isolates

OBJECTIVES Combination therapy is recommended for the treatment of KPC-producing Klebsiella pneumoniae (KPC-Kp), but the optimal regimen for colistin-resistant strains is unknown. We compared the synergistic activity and post-antibiotic effect (PAE) of colistin in combination with other antimicrobials against colistin-susceptible and -resistant KPC-Kp bloodstream isolates. METHODS The genotypes of nine colistin-susceptible and eight colistin-resistant KPC-Kp bloodstream isolates were analysed using PCR and amplicon sequencing. Combinations of colistin, meropenem, tigecycline, rifampicin and teicoplanin were then screened using the Etest, a chequerboard assay and time-kill studies. Synergistic combinations were also analysed with respect to the PAE in time-kill curves and the PAE at clinically achievable concentrations. RESULTS Insertional inactivation of the PhoQ/PhoB two-component regulatory system by mgrB-IS5 was identified in 6/8 (75%) colistin-resistant KPC-Kp. Colistin/rifampicin combinations resulted in no interactions [fractional inhibitory concentration (FIC) indices 1.5-2] for colistin-susceptible strains, but were uniformly synergistic (FIC indices 0.1-0.4) against colistin-resistant KPC-Kp. Time-kill kinetic analysis, at clinically achievable fixed concentrations of rifampicin and colistin, confirmed synergy and produced persistent growth inhibition (3 h) of colistin-resistant KPC-Kp strains exposed to colistin/rifampicin or colistin/rifampicin/tigecycline combinations. CONCLUSIONS Combinations of colistin plus rifampicin, and less frequently tigecycline, exhibited synergistic activity in vitro against colistin-resistant KPC-Kp strains.

Computed Tomographic Pulmonary Angiography for Diagnosis of Invasive Mold Diseases in Patients With Hematological Malignancies

BACKGROUND Invasive mold diseases (IMDs) of the lung remain a challenge for immunocompromised patients. Although timely diagnosis and treatment are crucial for the outcome of the infection, the poor sensitivity of microbiological techniques and the limited specificity of chest high-resolution computed tomography (HRCT) often delay definitive diagnosis of these infections. METHODS To explore the diagnostic utility of computed tomographic pulmonary angiography (CTPA) for detecting angioinvasive patterns of pulmonary infection, we performed a single-center, prospective, nonrandomized trial involving 36 patients with hematological malignancies who had clinical suspicion of IMD, as defined by European Organization for Research and Treatment of Cancer/Mycosis Study Group diagnostic criteria. RESULTS We found that 5 of 5 patients with proven IMD had CTPA-positive findings consistent with interruption of the arterial vessels (concordance, 100%). CTPA findings were positive in 5 of 7 patients with probable IMD (findings for 2 were considered false negative because lesions were too small or not evaluable). In 15 of 24 patients with a final diagnosis of possible IMD, CTPA findings were negative for 14 patients and were positive for 1 patient, who had septic emboli associated with Staphylococcus aureus bacteremia. CTPA findings were positive in the remaining 9 patients with a final diagnosis of possible IMD at the end of the study. CONCLUSIONS We conclude that CTPA appears to be a promising tool to exclude the diagnosis of IMD in high-risk patients without specific findings on HRCT scans, and it is most useful in the presence of well-circumscribed lesions in which there is suspicion for IMD.

The burden of early-onset sepsis in Emilia-Romagna (Italy): a 4-year, population-based study.

Abstract Objective: To provide the first Italian data on pathogens causing early-onset sepsis (EOS) and their antimicrobial susceptibility, after the successfully prevention of Group B streptococcus (GBS) EOS. Methods: Retrospective area-based cohort study from Emilia-Romagna (Italy). Cases of EOS registered (from 2009 to 2012) in all gestational age neonates were reviewed. Results: Live births (LB) numbered 146 682. Ninety neonates had EOS and 12 died (incidence rates of 0.61 and 0.08/1000 LB, respectively). EOS and mortality were the highest among neonates with a birth weight <1000 g (20.37/1000 LB and 8.49/1000 LB, respectively). The most common pathogens were GBS (n = 27, 0.18/1000 LB) and Escherichia coli (n = 19, 0.13/1000 LB). Most infants affected by E. coli EOS were born preterm (n = 13), had complications (n = 4) or died (n = 7). Among 90 isolates tested, only 3 were resistant to both first line empirical antibiotics. Multivariate logistic regression analysis showed that low gestational age, caesarean section and low platelet count at presentation were significantly associated with death or brain lesions (area under ROC curve = 0.939, H-L = 0.944, sensitivity 76.0%, specificity 90.7%). Conclusions: GBS slightly exceeds E. coli as a cause of EOS. However, E. coli is the prominent cause of death, complications and in most cases affects preterm neonates. Empirical antimicrobial therapy of EOS seems appropriate.