Successful Treatment of Carbapenem-Resistant Acinetobacter baumannii Meningitis With Sulbactam-Durlobactam.

BACKGROUND: The treatment of carbapenem-resistant Acinetobacter baumannii/calcoaceticus complex (CRAB) presents significant treatment challenges. METHODS: We report the case of a 42-year-old woman with CRAB meningitis who experienced persistently positive cerebrospinal fluid (CSF) cultures for 13 days despite treatment with high-dose ampicillin-sulbactam and cefiderocol. On day 13, she was transitioned to sulbactam-durlobactam and meropenem; 4 subsequent CSF cultures remained negative. After 14 days of sulbactam-durlobactam, she was cured of infection. Whole genome sequencing investigations identified putative mechanisms that contributed to the reduced cefiderocol susceptibility observed during cefiderocol therapy. Blood and CSF samples were collected pre-dose and 3-hours post initiation of a sulbactam-durlobactam infusion. RESULTS: The CRAB isolate belonged to sequence type 2. An acquired blaOXA-23 and an intrinsic blaOXA-51-like (ie, blaOXA-66) carbapenemase gene were identified. The paradoxical effect (ie, no growth at lower cefiderocol dilutions but growth at higher dilutions) was observed by broth microdilution after 8 days of cefiderocol exposure but not by disk diffusion. Potential markers of resistance to cefiderocol included mutations in the start codon of piuA and piuC iron transport genes and an A515V substitution in PBP3, the primary target of cefiderocol. Sulbactam and durlobactam were detected in CSF at both timepoints, indicating CSF penetration. CONCLUSIONS: This case describes successful treatment of refractory CRAB meningitis with the administration of sulbactam-durlobactam and meropenem and highlights the need to be cognizant of the paradoxical effect that can be observed with broth microdilution testing of CRAB isolates with cefiderocol.

Clinical outcomes and emergence of resistance of Pseudomonas aeruginosa infections treated with ceftolozane-tazobactam versus ceftazidime-avibactam.

Few studies compare outcomes of patients with difficult-to-treat resistance (DTR) Pseudomonas aeruginosa infections treated with ceftolozane-tazobactam versus ceftazidime-avibactam. A multicenter prospective study was conducted of unique patients with DTR P. aeruginosa infections from 2018 to 2023 receiving >72 h of ceftolozane-tazobactam or ceftazidime-avibactam, with confirmation that the P. aeruginosa isolate was susceptible to the agent administered by broth microdilution. Inverse probability weighting (IPW) incorporating propensity scores was utilized to ensure balanced baseline characteristics. Regression performed on the post-IPW group determined 30-day mortality and subsequent emergence of resistance (i.e., ≥4-fold increase in MIC) to the initial treatment (i.e., ceftolozane-tazobactam or ceftazidime-avibactam). Among 186 eligible patients, 102 (55%) received ceftolozane-tazobactam and 84 (45%) received ceftazidime-avibactam. In the post-IPW cohort, balance was achieved across all variables [e.g., demographics, severity of illness, severe immunocompromise, Charlson Comorbidity Index ≥5, continuous renal replacement therapy (CRRT), source of infection, combination therapy]. Thirty-day mortality was similar between the ceftolozane-tazobactam and ceftazidime-avibactam groups [21% vs 17%; adjusted odds ratio (aOR): 1.01 (95% confidence interval, CI: 0.90-1.14)]. Emergence of resistance was higher in the ceftolozane-tazobactam group [38% vs 25%; aOR: 1.89 (95% CI: 0.98-4.88)], but did not achieve statistical significance. Prolonged treatment durations and use of CRRT were associated with increased emergence of resistance (both P = 0.04). Although the survival of patients with DTR P. aeruginosa infections appears similar regardless of whether ceftolozane-tazobactam or ceftazidime-avibactam is prescribed, the emergence of resistance may be more concerning with the former. Plausible mechanistic explanations support these findings. Modifiable risk factors were identified that may mitigate this risk.

In a Pinch: Cefiderocol for CRAB Infections.

Carbapenem-resistant Acinetobacter baumannii (CRAB) can cause significant infections with limited treatment options available. Falcone et al. (https://doi.org/10.1128/aac.02142-21) describe a single-center retrospective study comparing clinical outcomes among patients with CRAB infections treated with cefiderocol-containing versus colistin-containing regimens. Patients who received cefiderocol-containing regimens had lower 30-day mortality, though there are several limitations raised here, which make interpretation and applicability difficult.

StenoSCORE: Predicting Stenotrophomonas maltophilia Bloodstream Infections in the Hematologic Malignancy Population.

Stenotrophomonas maltophilia bloodstream infections (BSI) are associated with considerable mortality in the hematologic malignancy population. Trimethoprim-sulfamethoxazole (TMP-SMX) is the treatment of choice; however, it is not routinely included in empirical treatment regimens, both because of its adverse event profile and the relative rarity of S. maltophilia infections. We developed a risk score to predict hematologic malignancy patients at increased risk for S. maltophilia BSI to guide early (TMP-SMX) therapy. Patients ≥12 years of age admitted to five hospitals between July 2016 and December 2019 were included. Two separate risk scores were developed, (i) a "knowledge-driven" risk score based upon previously identified risk factors in the literature in addition to variables identified by regression analysis using the current cohort, and (ii) a risk score based upon automatic variable selection. For both scores, discrimination (receiver operator characteristic [ROC] curves and C statistics) and calibration (Hosmer-Lemeshow goodness-of-fit test and graphical calibration plots) were assessed. Internal validation was assessed using leave-one-out cross-validation. In total, 337 unique patients were included; 21 (6.2%) had S. maltophilia BSI. The knowledge-driven risk score (acute leukemia, absolute neutrophil count category, mucositis, central line, and ≥3 days of carbapenem therapy) had superior performance (C statistic = 0.75; 0.71 after cross-validation) compared to that of the risk score utilizing automatic variable selection (C statistic = 0.63; 0.38 after cross-validation). A user-friendly risk score incorporating five variables easily accessible to clinicians performed moderately well to predict hematologic malignancy patients at increased risk for S. maltophilia BSI. External validation using a larger cohort is necessary to create a refined risk score before broad clinical application.

Prevalence of blaCTX-M Genes in Gram-Negative Bloodstream Isolates across 66 Hospitals in the United States.

Understanding bacterial species at greatest risk for harboring blaCTX-M genes is necessary to guide antibiotic treatment. We identified the species-specific prevalence of blaCTX-M genes in Gram-negative clinical isolates from the United States. Twenty-four microbiology laboratories representing 66 hospitals using the GenMark Dx ePlex blood culture identification Gram-negative (BCID-GN) panel extracted blood culture results from April 2019 to July 2020. The BCID-GN panel includes 21 Gram-negative targets. Along with identifying blaCTX-M genes, it detects major carbapenemase gene families. A total of 4,209 Gram-negative blood cultures were included. blaCTX-M genes were identified in 462 (11%) specimens. The species-specific prevalence of blaCTX-M genes was as follows: Escherichia coli (16%), Klebsiella pneumoniae (14%), Klebsiella oxytoca (6%), Salmonella spp. (6%), Acinetobacter baumannii (5%), Enterobacter species (3%), Proteus mirabilis (2%), Serratia marcescens (0.6%), and Pseudomonas aeruginosa (0.5%). blaCTX-M prevalence was 26%, 24%, and 22% among participating hospitals in the District of Columbia, New York, and Florida, respectively. Carbapenemase genes were identified in 61 (2%) organisms with the following distribution: blaKPC (59%), blaVIM (16%), blaOXA (10%), blaNDM (8%), and blaIMP (7%). The species-specific prevalence of carbapenemase genes was as follows: A. baumannii (5%), K. pneumoniae (3%), P. mirabilis (3%), Enterobacter species (3%), Citrobacter spp. (3%), P. aeruginosa (2%), E. coli (<1%), K. oxytoca (<1%), and S. marcescens (<1%). Approximately 11% of Gram-negative organisms in our US cohort contain blaCTX-M genes. blaCTX-M genes remain uncommon in organisms beyond E. coli, K. pneumoniae, and K. oxytoca Future molecular diagnostic panels would benefit from the inclusion of plasmid-mediated ampC and SHV and TEM extended-spectrum beta-lactamase (ESBL) targets.

Type II Secretion-Dependent Degradative and Cytotoxic Activities Mediated by Stenotrophomonas maltophilia Serine Proteases StmPr1 and StmPr2.

Stenotrophomonas maltophilia is an emerging opportunistic pathogen that primarily causes pneumonia and bacteremia in immunocompromised individuals. We recently reported that S. maltophilia strain K279a encodes the Xps type II secretion system and that Xps promotes rounding, actin rearrangement, detachment, and death in the human lung epithelial cell line A549. Here, we show that Xps-dependent cell rounding and detachment occur with multiple human and murine cell lines and that serine protease inhibitors block Xps-mediated rounding and detachment of A549 cells. Using genetic analysis, we determined that the serine proteases StmPr1 and StmPr2, which were confirmed to be Xps substrates, are predominantly responsible for secreted proteolytic activities exhibited by strain K279a, as well as the morphological and cytotoxic effects on A549 cells. Supernatants from strain K279a also promoted the degradation of type I collagen, fibrinogen, and fibronectin in a predominantly Xps- and protease-dependent manner, although some Xps-independent degradation of fibrinogen was observed. Finally, Xps, and predominantly StmPr1, degraded interleukin 8 (IL-8) secreted by A549 cells during coculture with strain K279a. Our findings indicate that while StmPr1 and StmPr2 are predominantly responsible for A549 cell rounding, extracellular matrix protein degradation, and IL-8 degradation, additional Xps substrates also contribute to these activities. Altogether, our data provide new insight into the virulence potential of the S. maltophilia Xps type II secretion system and its StmPr1 and StmPr2 substrates.

Extended-Infusion ß-Lactam Therapy, Mortality, and Subsequent Antibiotic Resistance Among Hospitalized Adults With Gram-Negative Bloodstream Infections.

Importance: Current evidence is conflicting for associations of extended-infusion ß-lactam (EI-BL) therapy with clinical outcomes. Objective: To investigate the association of EI-BL therapy with survival, adverse events, and emergence of antibiotic resistance in adults with gram-negative bloodstream infections (GN-BSI). Design, Setting, and Participants: This cohort study of consecutive adults with GN-BSI admitted to 24 United States hospitals between January 1, 2019, and December 31, 2019, receiving EI-BL were compared with adults with GN-BSI receiving the same agents as intermittent infusion ß-lactam (II-BL; ≤1-hour infusions). Statistical analysis was performed from January to October 2023. Exposures: EI-BL (ie, ≥3-hour infusion). Main Outcomes and Measures: EI-BL and II-BL groups underwent 1:3 nearest-neighbor propensity score matching (PSM) without replacement. Multivariable regression was applied to the PSM cohort to investigate outcomes, all censored at day 90. The primary outcome was mortality; secondary outcomes included antibiotic adverse events and emergence of resistance (≥4-fold increase in the minimum inhibitory concentration of the ß-lactam used to treat the index GN-BSI). Results: Among the 4861 patients included, 2547 (52.4%) were male; and the median (IQR) age was 67 (55-77) years. There were 352 patients in the EI-BL 1:3 PSM group, and 1056 patients in the II-BL 1:3 PSM group. Among 1408 PSM patients, 373 (26.5%) died by day 90. The odds of mortality were lower in the EI-BL group (adjusted odds ratio [aOR], 0.71 [95% CI, 0.52-0.97]). In a stratified analysis, a survival benefit was only identified in patients with severe illness or elevated minimum inhibitory concentrations (ie, in the intermediate range for the antibiotic administered). There were increased odds of catheter complications (aOR, 3.14 [95% CI, 1.66-5.96]) and antibiotic discontinuation because of adverse events (eg, acute kidney injury, cytopenias, seizures) in the EI-BL group (aOR, 3.66 [95% CI, 1.68-7.95]). Emergence of resistance was similar in the EI-BL and II-BL groups at 2.9% vs 7.2%, respectively (P = .35). Conclusions and Relevance: In this cohort study of patients with GN-BSI, EI-BL therapy was associated with reduced mortality for patients with severe illness or those infected with nonsusceptible organisms; potential advantages in other groups remain unclear and need to be balanced with potential adverse events. The subsequent emergence of resistance warrants investigation in a larger cohort.

Stenotrophomonas maltophilia encodes a type II protein secretion system that promotes detrimental effects on lung epithelial cells.

The Gram-negative bacterium Stenotrophomonas maltophilia is increasingly identified as a multidrug-resistant pathogen, being associated with pneumonia, among other infections. Despite this increasing clinical problem, the genetic and molecular basis of S. maltophilia virulence is quite minimally defined. We now report that strain K279a, the first clinical isolate of S. maltophilia to be sequenced, encodes a functional type II protein secretion (T2S) system. Indeed, mutants of K279a that contain a mutation in the xps locus exhibit a loss of at least seven secreted proteins and three proteolytic activities. Unlike culture supernatants from the parental K279a, supernatants from multiple xps mutants also failed to induce the rounding, detachment, and death of A549 cells, a human lung epithelial cell line. Supernatants of the xps mutants were also unable to trigger a massive rearrangement in the host cell's actin cytoskeleton that was associated with K279a secretion. In all assays, a complemented xpsF mutant behaved as the wild type did, demonstrating that Xps T2S is required for optimal protein secretion and the detrimental effects on host cells. The activities that were defined as being Xps dependent in K279a were evident among other respiratory isolates of S. maltophilia. Utilizing a similar type of genetic analysis, we found that a second T2S system (Gsp) encoded by the K279a genome is cryptic under all of the conditions tested. Overall, this study represents the first examination of T2S in S. maltophilia, and the data obtained indicate that Xps T2S likely plays an important role in S. maltophilia pathogenesis.

Hfq-dependent, co-ordinate control of cyclic diguanylate synthesis and catabolism in the plague pathogen Yersinia pestis.

Yersinia pestis, the cause of the disease plague, forms biofilms to enhance flea-to-mammal transmission. Biofilm formation is dependent on exopolysaccharide synthesis and is controlled by the intracellular levels of the second messenger molecule cyclic diguanylate (c-di-GMP), but the mechanisms by which Y. pestis regulates c-di-GMP synthesis and turnover are not fully understood. Here we show that the small RNA chaperone Hfq contributes to the regulation of c-di-GMP levels and biofilm formation by modulating the abundance of both the c-di-GMP phosphodiesterase HmsP and the diguanylate cyclase HmsT. To do so, Hfq co-ordinately promotes hmsP mRNA accumulation while simultaneously decreasing the stability of the hmsT transcript. Hfq-dependent regulation of HmsP occurs at the transcriptional level while the regulation of HmsT is post-transcriptional and is localized to the 5' untranslated region/proximal coding sequence of the hmsT transcript. Decoupling HmsP from Hfq-based regulation is sufficient to overcome the effects of Δhfq on c-di-GMP and biofilm formation. We propose that Y. pestis utilizes Hfq to link c-di-GMP levels to environmental conditions and that the disregulation of c-di-GMP turnover in the absence of Hfq may contribute to the severe attenuation of Y. pestis lacking this RNA chaperone in animal models of plague.

Impact of weekly asymptomatic testing for severe acute respiratory coronavirus virus 2 (SARS-CoV-2) in inpatients at an academic hospital.

We analyzed the impact of a 7-day recurring asymptomatic SARS-CoV-2 testing protocol for all patients hospitalized at a large academic center. Overall, 40 new cases were identified, and 1 of 3 occurred after 14 days of hospitalization. Recurring testing can identify unrecognized infections, especially during periods of elevated community transmission.

Severe acute respiratory coronavirus virus 2 (SARS-CoV-2) exposure investigations using genomic sequencing among healthcare workers and patients in a large academic center.

Severe acute respiratory coronavirus virus 2 (SARS-CoV-2) transmissions among healthcare workers and hospitalized patients are challenging to confirm. Investigation of infected persons often reveals multiple potential risk factors for viral acquisition. We combined exposure investigation with genomic analysis confirming 2 hospital-based clusters. Prolonged close contact with unmasked, unrecognized infectious, individuals was a common risk.

Hospital-acquired infections among adult patients admitted for coronavirus disease 2019 (COVID-19).

In a multicenter cohort of 963 adults hospitalized due to coronavirus disease 2019 (COVID-19), 5% had a proven hospital-acquired infection (HAI) and 21% had a proven, probable, or possible HAI. Risk factors for proven or probable HAIs included intensive care unit admission, dexamethasone use, severe COVID-19, heart failure, and antibiotic exposure upon admission.

Stenotrophomonas maltophilia strains replicate and persist in the murine lung, but to significantly different degrees.

The environmental bacterium Stenotrophomonas maltophilia is increasingly described as a multidrug-resistant pathogen of humans, being associated with pneumonia, among other diseases. But the degree to which S. maltophilia is capable of replicating in a mammalian host has been an issue of controversy. Using a model of intranasal inoculation into adult A/J mice, we now document that S. maltophilia strain K279a, the clinical isolate of S. maltophilia whose complete genome sequence was recently determined, is in fact capable of replicating in lungs, displaying as much as a 10-fold increase in c.f.u. in the first 8 h of infection. Importantly, as few as 10(4) c.f.u. deposited into the A/J lung was sufficient to promote bacterial outgrowth. Bacterial replication in the lungs of the A/J mice was followed by elevations in pro-inflammatory cytokines and also promoted resistance to subsequent challenge. We also found that DBA/2 mice were permissive for S. maltophilia K279a replication, although the level of growth and persistence in these animals was less than it was in the A/J mice. In contrast, the BALB/c and C57BL/6 mouse strains were non-permissive for S. maltophilia K279a growth. Interestingly, when five additional clinical isolates were introduced into the A/J lung, marked differences in survival were observed, with some strains being much less infective than K279a and others being appreciably more infective. These data suggest that the presence of major virulence determinants is variable among clinical isolates. Overall, this study confirms the infectivity of S. maltophilia for the mammalian host, and illustrates how both host and bacterial factors affect the outcome of Stenotrophomonas infection.

Prevalence of Co-infection at the Time of Hospital Admission in COVID-19 Patients, A Multicenter Study.

BACKGROUND: Bacterial infections may complicate viral pneumonias. Recent reports suggest that bacterial co-infection at time of presentation is uncommon in coronavirus disease 2019 (COVID-19); however, estimates were based on microbiology tests alone. We sought to develop and apply consensus definitions, incorporating clinical criteria to better understand the rate of co-infections and antibiotic use in COVID-19. METHODS: A total of 1016 adult patients admitted to 5 hospitals in the Johns Hopkins Health System between March 1, 2020, and May 31, 2020, with COVID-19 were evaluated. Adjudication of co-infection using definitions developed by a multidisciplinary team for this study was performed. Both respiratory and common nonrespiratory co-infections were assessed. The definition of bacterial community-acquired pneumonia (bCAP) included proven (clinical, laboratory, and radiographic criteria plus microbiologic diagnosis), probable (clinical, laboratory, and radiographic criteria without microbiologic diagnosis), and possible (not all clinical, laboratory, and radiographic criteria met) categories. Clinical characteristics and antimicrobial use were assessed in the context of the consensus definitions. RESULTS: Bacterial respiratory co-infections were infrequent (1.2%); 1 patient had proven bCAP, and 11 (1.1%) had probable bCAP. Two patients (0.2%) had viral respiratory co-infections. Although 69% of patients received antibiotics for pneumonia, the majority were stopped within 48 hours in patients with possible or no evidence of bCAP. The most common nonrespiratory infection was urinary tract infection (present in 3% of the cohort). CONCLUSIONS: Using multidisciplinary consensus definitions, proven or probable bCAP was uncommon in adults hospitalized due to COVID-19, as were other nonrespiratory bacterial infections. Empiric antibiotic use was high, highlighting the need to enhance antibiotic stewardship in the treatment of viral pneumonias.