Freshwater and Marine Environments in California Are a Reservoir of Carbapenem-Resistant Bacteria

Carbapenems are last-resort antibiotics used to treat multidrug-resistant bacterial infections. Resistance to carbapenems has been designated as an urgent threat and is increasing in healthcare settings. However, little is still known about the distribution and characteristics of carbapenem-resistant bacteria (CRB) outside of healthcare settings. Here, we surveyed the distribution of CRB in ten diverse freshwater and seawater environments in California, U.S., ranging from San Luis Obispo County to San Bernardino County, combining both direct isolation and enrichment approaches to increase the diversity of isolated CRB. From the locations surveyed, we selected 30 CRB for further characterization. These isolates were identified as members of the genera Aeromonas, Enterobacter, Enterococcus, Paenibacillus, Pseudomonas, Sphingobacterium, and Stenotrophomonas. These isolates were resistant to carbapenems, other β-lactams, and often to other antibiotics (tetracycline, gentamicin, or ciprofloxacin). We also found that nine isolates belonging to the genera Aeromonas, Enterobacter (blaIMI-2), and Stenotrophomonas (blaL1) produced carbapenemases. Overall, our findings indicate that sampling different types of aquatic environments and combining different isolation approaches increase the diversity of the environmental CRB obtained. Moreover, our study supports the increasingly recognized role of natural water systems as an underappreciated reservoir of bacteria resistant to carbapenems and other antibiotics, including bacteria carrying carbapenemase genes.

The multidrug efflux pump regulator AcrR directly represses motility in Escherichia coli

Efflux and motility are two key biological functions in bacteria. Recent findings have shown that efflux impacts flagellum biosynthesis and motility in Escherichia coli and other bacteria. AcrR is known to be the major transcriptional repressor of AcrAB-TolC, the main multidrug efflux pump in E. coli and other Enterobacteriaceae. However, the underlying molecular mechanisms of how efflux and motility are co-regulated remain poorly understood. Here, we have studied the role of AcrR in direct regulation of motility in E. coli. By combining bioinformatics, electrophoretic mobility shift assays (EMSAs), gene expression, and motility experiments, we have found that AcrR represses motility in E. coli by directly repressing transcription of the flhDC operon, but not the other flagellum genes/operons tested. flhDC encodes the master regulator of flagellum biosynthesis and motility genes. We found that such regulation primarily occurs by direct binding of AcrR to the flhDC promoter region containing the first of the two predicted AcrR-binding sites identified in this promoter. This is the first report of direct regulation by AcrR of genes unrelated to efflux or detoxification. Moreover, we report that overexpression of AcrR restores to parental levels the increased swimming motility previously observed in E. coli strains without a functional AcrAB-TolC pump, and that such effect by AcrR is prevented by the AcrR ligand and AcrAB-TolC substrate ethidium bromide. Based on these and prior findings, we provide a novel model in which AcrR senses efflux and then co-regulates efflux and motility in E. coli to maintain homeostasis and escape hazards. IMPORTANCE Efflux and motility play a major role in bacterial growth, colonization, and survival. In Escherichia coli, the transcriptional repressor AcrR is known to directly repress efflux and was later found to also repress flagellum biosynthesis and motility by Kim et al. (J Microbiol Biotechnol 26:1824-1828, 2016, doi: 10.4014/jmb.1607.07058). However, it remained unknown whether AcrR represses flagellum biosynthesis and motility directly and through which target genes, or indirectly because of altering the amount of efflux. This study reveals that AcrR represses flagellum biosynthesis and motility by directly repressing the expression of the flhDC master regulator of flagellum biosynthesis and motility genes, but not the other flagellum genes tested. We also show that the antimicrobial, efflux pump substrate, and AcrR ligand ethidium bromide regulates motility via AcrR. Overall, these findings support a novel model of direct co-regulation of efflux and motility mediated by AcrR in response to stress in E. coli.

Urban and agricultural soils in Southern California are a reservoir of carbapenem-resistant bacteria

Carbapenems are last‐resort β‐lactam antibiotics used in healthcare facilities to treat multidrug‐resistant infections. Thus, most studies on identifying and characterizing carbapenem‐resistant bacteria (CRB) have focused on clinical settings. Relatively, little is still known about the distribution and characteristics of CRBs in the environment, and the role of soil as a potential reservoir of CRB in the United States remains unknown. Here, we have surveyed 11 soil samples from 9 different urban or agricultural locations in the Los Angeles–Southern California area to determine the prevalence and characteristics of CRB in these soils. All samples tested contained CRB with a frequency of <10 to 1.3 × 10⁴ cfu per gram of soil, with most agricultural soil samples having a much higher relative frequency of CRB than urban soil samples. Identification and characterization of 40 CRB from these soil samples revealed that most of them were members of the genera Cupriavidus, Pseudomonas, and Stenotrophomonas. Other less prevalent genera identified among our isolated CRB, especially from agricultural soils, included the genera Enterococcus, Bradyrhizobium, Achromobacter, and Planomicrobium. Interestingly, all of these carbapenem‐resistant isolates were also intermediate or resistant to at least 1 noncarbapenem antibiotic. Further characterization of our isolated CRB revealed that 11 Stenotrophomonas, 3 Pseudomonas, 1 Enterococcus, and 1 Bradyrhizobium isolates were carbapenemase producers. Our findings show for the first time that both urban and agricultural soils in Southern California are an underappreciated reservoir of bacteria resistant to carbapenems and other antibiotics, including carbapenemase‐producing CRB.

Comparative Genomics Reveals a Well-Conserved Intrinsic Resistome in the Emerging Multidrug-Resistant Pathogen Cupriavidus gilardii

The Gram-negative bacterium Cupriavidus gilardii is an emerging multidrug-resistant pathogen found in many environments. However, little is known about this species or its antibiotic resistance mechanisms. We used biochemical tests, antibiotic susceptibility experiments, and whole-genome sequencing to characterize an environmental C. gilardii isolate. Like clinical isolates, this isolate was resistant to meropenem, gentamicin, and other antibiotics. Resistance to these antibiotics appeared to be related to the large number of intrinsic antibiotic resistance genes found in this isolate. As determined by comparative genomics, this resistome was also well conserved in the only two other C. gilardii strains sequenced to date. The intrinsic resistome of C. gilardii did not include the colistin resistance gene mcr-5, which was in a transposon present only in one strain. The intrinsic resistome of C. gilardii was comprised of (i) many multidrug efflux pumps, such as a homolog of the Pseudomonas aeruginosa MexAB-OprM pump that may be involved in resistance to meropenem, other β-lactams, and aminoglycosides; (ii) a novel β-lactamase (OXA-837) that decreases susceptibility to ampicillin but not to other β-lactams tested; (iii) a new aminoglycoside 3-N-acetyltransferase [AAC(3)-IVb, AacC10] that decreases susceptibility to gentamicin and tobramycin; and (iv) a novel partially conserved aminoglycoside 3"-adenylyltransferase [ANT(3")-Ib, AadA32] that decreases susceptibility to spectinomycin and streptomycin. These findings provide the first mechanistic insight into the intrinsic resistance of C. gilardii to multiple antibiotics and its ability to become resistant to an increasing number of drugs during therapy.IMPORTANCECupriavidus gilardii is a bacterium that is gaining increasing attention both as an infectious agent and because of its potential use in the detoxification of toxic compounds and other biotechnological applications. In recent years, however, there has been an increasing number of reported infections, some of them fatal, caused by C. gilardii These infections are hard to treat because this bacterium is naturally resistant to many antibiotics, including last-resort antibiotics, such as carbapenems. Moreover, this bacterium often becomes resistant to additional antibiotics during therapy. However, little is known about C. gilardii and its antibiotic resistance mechanisms. The significance of our research is in providing, for the first time, whole-genome information about the natural antibiotic resistance genes found in this bacterium and their conservation among different C. gilardii strains. This information may provide new insights into the appropriate use of antibiotics in combating infections caused by this emerging pathogen.

Prevalence and characterization of carbapenem-resistant bacteria in water bodies in the Los Angeles-Southern California area

Carbapenems are β-lactam antibiotics used in healthcare settings as last resort drugs to treat infections caused by antibiotic-resistant bacteria. Carbapenem-resistant bacteria are increasingly being isolated from healthcare facilities; however, little is known about their distribution or prevalence in the environment, especially in the United States, where their distribution in water environments from the West Coast has not been studied before. The aim of this study was to determine the prevalence of carbapenem-resistant bacteria and carbapenemase genes in water bodies from the Los Angeles area (California, USA). All samples that were analyzed contained carbapenem-resistant bacteria with a frequency of between 0.1 and 324 carbapenem-resistant cfu per 100 mls of water. We identified 76 carbapenem-resistant or -intermediate isolates, most of which were also resistant to noncarbapenem antibiotics, as different strains of Enterobacter asburiae, Aeromonas veronii, Cupriavidus gilardii, Pseudomonas, and Stenotrophomonas species. Of them, 52 isolates were carbapenemase-producers. Furthermore, PCR and sequence analysis to identify the carbapenemase gene of these carbapenemase-producing isolates revealed that all Enterobacter asburiae isolates had a blaIMI-2 gene 100% identical to the reference sequence, and all Stenotrophomonas maltophlia isolates had a blaL1 gene 83%-99% identical to the reference blaL1 . Our findings indicate that water environments in Southern California are an important reservoir of bacteria-resistant to carbapenems and other antibiotics, including bacteria carrying intrinsic and acquired carbapenemase genes.

Cost/benefit analysis of pharmacologic hemostasis

BACKGROUND

Surgical bleeding with possible associated coagulopathies is a major source of morbidity and mortality. More than 27% of patients receive unnecessary blood or blood-product transfusions during cardiac operations. Analysis of the cost-benefit of pharmacologic hemostasis can be accomplished by relating all the components of cost, which include both direct and indirect costs to both direct and indirect benefits to the patient.

METHODS

A significant reduction in transfusion requirements can be achieved by the systematic application of a clinical algorithm. An alternative is to use drugs that enhance hemostasis. Four such drugs commonly used are desmopressin acetate, tranexamic acid, epsilon-aminocaproic acid, and aprotinin. All these agents have been shown to successfully reduce bleeding and the need for transfusion. It appears that the order of efficacy (greatest to least) is aprotinin, tranexamic acid, epsilon-aminocaproic acid, and desmopressin acetate.

RESULTS

Cost/benefit analysis associated with the use of these agents is complex. The direct costs of these drug treatments can be balanced against the costs related to blood and blood-product administration. Using epsilon-aminocaproic acid, blood used is valued at $30, whereas the drug treatment cost is less than $2. Aprotinin use results in costs of more than $500, with the drug costing $900.

CONCLUSIONS

Improved hemostasis should also result in indirect cost savings from reduced operating room time, reduced intensive care unit and hospital stay, and the avoidance of reoperation for bleeding.

Lung transplantation in Louisiana: report of the first twenty lung transplants performed in the state

Lung transplantation is a successful alternative treatment for a variety of end-stage lung diseases. The first 20 lung transplants performed in Louisiana between November 1990 and July 1994 are reported from Ochsner Foundation Hospital. Transplant procedures included 1 heart-lung, 11 bilateral sequential lung, and 8 single-lung transplants in 8 males and 11 females (1 retransplantation). The average age was 38 years (range 7-60), and the median waiting time was 34.5 days (range 1-329). Indications for transplant included emphysema, pulmonary fibrosis, pulmonary hypertension, cystic fibrosis, bronchiectasis, and bronchiolitis obliterans. Overall 1-year and 3-year survival were 65.0% and 58.5%, respectively. Infection was the major cause of morbidity and mortality. Rejection episodes were observed but treated successfully in all 20 patients. Lung transplantation has proved to be a successful treatment for a variety of severely limiting and terminal pulmonary conditions for patients in our state.

Risk of spinal cord dysfunction in patients undergoing thoracoabdominal aortic replacement

The records of 150 consecutive patients undergoing thoracoabdominal aortic replacement from 1980 to 1991 were retrospectively reviewed. There were 89 men and 61 women; mean age was 67.8 years (range: 33 to 88 years). Since June 1989, a multimodality prospective perioperative protocol was used to reduce the risk of spinal cord dysfunction. Ischemia is minimized by complete intercostal reimplantation whenever possible, cerebrospinal fluid drainage, and maintenance of proximal hypertension during cross-clamping. Spinal cord metabolism is reduced by moderate hypothermia, high-dose barbiturates, and avoidance of hyperglycemia. Reperfusion injury is minimized by the use of mannitol, steroids, and calcium channel blockers. Ninety-seven percent of patients survived long enough for evaluation of their neurologic function. Spinal cord dysfunction was reduced from 6 of 108 (6%) in the preprotocol group to 0 of 42 in the protocol group (0%) (p less than 0.01). The overall 30-day operative mortality was not significantly different between the groups (9% versus 12%, p = NS). A multimodality protocol appears to be effective in reducing the risk of spinal cord injury during thoracoabdominal aortic replacement.

Duane's retraction syndrome

Duane's retraction syndrome (DRS) is a congenital abnormality of ocular motility that occurs in about 1% of strabismic patients. Three types have been described and the clinical features include incomitant horizontal strabismus, restricted motility and globe retraction. Head turn, upshoot or downshoot of the adducted eye, and bilaterality may occasionally be present. Since strabismus is invariably present in DRS, careful assessment of extraocular motility should be performed on all children with a suspected or confirmed eye turn. Early diagnosis may save practitioners and parents hours of time and financial investment with orthoptic and surgical management attempts. A case of DRS is presented.