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Wolter DJ, Scott A, Armbruster CR, Whittington D, Edgar JS, Qin X, Buccat AM, McNamara S, Blackledge M, Waalkes A, Salipante SJ, Ernst RK, Hoffman LR. Repeated isolation of an antibiotic-dependent and temperature-sensitive mutant of Pseudomonas aeruginosa from a cystic fibrosis patient. J Antimicrob Chemother 2021; 76:616-625. [PMID: 33259594 DOI: 10.1093/jac/dkaa482] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2020] [Accepted: 10/02/2020] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND Bacteria adapt to survive and grow in different environments. Genetic mutations that promote bacterial survival under harsh conditions can also restrict growth. The causes and consequences of these adaptations have important implications for diagnosis, pathogenesis, and therapy. OBJECTIVES We describe the isolation and characterization of an antibiotic-dependent, temperature-sensitive Pseudomonas aeruginosa mutant chronically infecting the respiratory tract of a cystic fibrosis (CF) patient, underscoring the clinical challenges bacterial adaptations can present. METHODS Respiratory samples collected from a CF patient during routine care were cultured for standard pathogens. P. aeruginosa isolates recovered from samples were analysed for in vitro growth characteristics, antibiotic susceptibility, clonality, and membrane phospholipid and lipid A composition. Genetic mutations were identified by whole genome sequencing. RESULTS P. aeruginosa isolates collected over 5 years from respiratory samples of a CF patient frequently harboured a mutation in phosphatidylserine decarboxylase (psd), encoding an enzyme responsible for phospholipid synthesis. This mutant could only grow at 37°C when in the presence of supplemented magnesium, glycerol, or, surprisingly, the antibiotic sulfamethoxazole, which the source patient had repeatedly received. Of concern, this mutant was not detectable on standard selective medium at 37°C. This growth defect correlated with alterations in membrane phospholipid and lipid A content. CONCLUSIONS A P. aeruginosa mutant chronically infecting a CF patient exhibited dependence on sulphonamides and would likely evade detection using standard clinical laboratory methods. The diagnostic and therapeutic challenges presented by this mutant highlight the complex interplay between bacterial adaptation, antibiotics, and laboratory practices, during chronic bacterial infections.
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Affiliation(s)
- Daniel J Wolter
- Department of Pediatrics, University of Washington, Seattle, WA, USA.,Seattle Children's Hospital, Seattle, WA, USA
| | - Alison Scott
- Department of Microbial Pathogenesis, University of Maryland, Baltimore, MD, USA
| | | | - Dale Whittington
- Department of Medicinal Chemistry, University of Washington, Seattle, WA, USA
| | - John S Edgar
- Department of Medicinal Chemistry, University of Washington, Seattle, WA, USA
| | - Xuan Qin
- Seattle Children's Hospital, Seattle, WA, USA
| | | | | | | | - Adam Waalkes
- Department of Laboratory Medicine, University of Washington, Seattle, WA, USA
| | - Stephen J Salipante
- Department of Laboratory Medicine, University of Washington, Seattle, WA, USA
| | - Robert K Ernst
- Department of Microbial Pathogenesis, University of Maryland, Baltimore, MD, USA
| | - Lucas R Hoffman
- Department of Pediatrics, University of Washington, Seattle, WA, USA.,Seattle Children's Hospital, Seattle, WA, USA.,Department of Microbiology, University of Washington, Seattle, WA, USA
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Lipopolysaccharide loss produces partial colistin dependence and collateral sensitivity to azithromycin, rifampicin and vancomycin in Acinetobacter baumannii. Int J Antimicrob Agents 2015; 46:696-702. [PMID: 26391380 DOI: 10.1016/j.ijantimicag.2015.07.017] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Revised: 07/29/2015] [Accepted: 07/29/2015] [Indexed: 12/11/2022]
Abstract
Treatment options for multidrug-resistant (MDR) strains of Acinetobacter baumannii that acquire resistance to colistin are limited. Acinetobacter baumannii can become highly resistant to colistin through complete loss of lipopolysaccharide (LPS) owing to mutations in the genes encoding the first three enzymes involved in lipid A biosynthesis (lpxA, lpxC and lpxD). The objective of this study was to characterise the susceptibility to 15 clinically relevant antibiotics and 6 antimicrobial peptides (AMPs) of MDR A. baumannii clinical isolates that acquired colistin resistance due to mutations in lpxA, lpxC and lpxD as well as their colistin-susceptible counterparts. A dramatic increase in antibiotic susceptibility (≥16-fold increase) was observed upon LPS loss for azithromycin, rifampicin and vancomycin, whereas a moderate increase in susceptibility was seen for amikacin, ceftazidime, imipenem, cefepime and meropenem. Importantly, concentrations ranging from 8 mg/L to 32 mg/L of the six AMPs were able to reduce bacterial viability by ≥3 log10 in growth curve assays. We also demonstrate that colistin resistance results in partial colistin dependence for growth in LPS-deficient strains containing mutations in lpxA, lpxC and lpxD, but not when colistin resistance occurs via LPS modification due to mutations in the PmrA/B two-component system. The results of this study indicate that loss of LPS expression results in collateral sensitivity to azithromycin, rifampicin and vancomycin, and that the six AMPs tested retain activity against LPS-deficient strains, indicating that these antibiotics may be viable treatment options for infections caused by these strains.
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Ko SY, Chung HJ, Sung HS, Kim MN. Emergence of β-Lactam-Dependent Bacillus cereus associated with Prolonged Treatment with Cefepime in a Neutropenic Patient. Ann Lab Med 2007; 27:216-20. [DOI: 10.3343/kjlm.2007.27.3.216] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Affiliation(s)
- Sun-Young Ko
- Department of Laboratory Medicine, University of Ulsan College of Medicine and Asan Medical Center, Seoul, Korea
| | - Hee-Jung Chung
- Department of Laboratory Medicine, University of Ulsan College of Medicine and Asan Medical Center, Seoul, Korea
| | - Heong-Sup Sung
- Department of Laboratory Medicine, University of Ulsan College of Medicine and Asan Medical Center, Seoul, Korea
| | - Mi-Na Kim
- Department of Laboratory Medicine, University of Ulsan College of Medicine and Asan Medical Center, Seoul, Korea
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Goldstein F, Perutka J, Cuirolo A, Plata K, Faccone D, Morris J, Sournia A, Kitzis MD, Ly A, Archer G, Rosato AE. Identification and phenotypic characterization of a beta-lactam-dependent, methicillin-resistant Staphylococcus aureus strain. Antimicrob Agents Chemother 2007; 51:2514-22. [PMID: 17470657 PMCID: PMC1913265 DOI: 10.1128/aac.00040-07] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Methicillin resistance in Staphylococcus aureus is primarily mediated by the acquired penicillin-binding protein PBP 2a, which is encoded by mecA. PBP 2a acts together with native PBP 2 to mediate oxacillin resistance by contributing complementary transpeptidase and transglycosylase activities, respectively. In this study, we have investigated a phenotype of beta-lactam dependence in a clinical methicillin-resistant S. aureus strain (strain 2884D) obtained by in vitro selection with ceftobiprole. 28884D, which grew very poorly in blood agar, required the presence of the beta-lactam antibiotics to grow. On the basis of this observation, we hypothesized that a gene or genes essential for growth were dependent on oxacillin induction. Identification and analysis of genes regulated by oxacillin were performed by both real-time reverse transcription-PCR and spotted microarray analysis. We found that mecA was constitutively expressed in strain 2884D and that the constitutive expression resulted from perturbations in the two systems involved in its regulation, i.e., MecI/MecR1 (staphylococcal chromosome cassette mec type I) and BlaI/BlaR1 (nonfunctional penicillinase operon). PBP 2 appeared to be poorly induced by oxacillin in 2884D. Further analysis of the PBP 2 two-component VraSR regulatory system showed that it was nonfunctional, accounting for the lack of response to oxacillin. Together, these results support the notion that limited PBP 2 availability may have led 2884D to become dependent on oxacillin-mediated mecA induction as a required survival mechanism.
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MESH Headings
- Amino Acid Sequence
- Anti-Bacterial Agents/metabolism
- Bacterial Proteins/metabolism
- Cephalosporins/pharmacology
- Chromosomes, Bacterial
- DNA, Bacterial/analysis
- DNA, Bacterial/genetics
- DNA-Binding Proteins
- Electrophoresis, Gel, Pulsed-Field
- Gene Expression Regulation, Bacterial
- Methicillin Resistance/genetics
- Microbial Sensitivity Tests
- Molecular Sequence Data
- Oligonucleotide Array Sequence Analysis
- Phenotype
- Reverse Transcriptase Polymerase Chain Reaction
- Selection, Genetic
- Sequence Analysis, DNA
- Sequence Homology, Amino Acid
- Staphylococcus aureus/drug effects
- Staphylococcus aureus/genetics
- Transcription, Genetic
- beta-Lactams/metabolism
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Affiliation(s)
- Fred Goldstein
- Division of Infectious Diseases, Department of Internal Medicine, Virginia Commonwealth University, Richmond, VA 23298, USA
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