Comprehensive stability analysis of 13 β-lactams and β-lactamase inhibitors in in vitro media, and novel supplement dosing strategy to mitigate thermal drug degradation

Non-clinical antibiotic development relies on in vitro susceptibility and infection model studies. Validating the achievement of the targeted drug concentrations is essential to avoid under-estimation of drug effects and over-estimation of resistance emergence. While certain β-lactams (e.g., imipenem) and β-lactamase inhibitors (BLIs; clavulanic acid) are believed to be relatively unstable, limited tangible data on their stability in commonly used in vitro media are known. We aimed to determine the thermal stability of 10 β-lactams and 3 BLIs via LC-MS/MS in cation-adjusted Mueller Hinton broth at 25 and 36°C as well as agar at 4 and 37°C, and in water at -20, 4, and 25°C. Supplement dosing algorithms were developed to achieve broth concentrations close to their target over 24 h. During incubation in broth (pH 7.25)/agar, degradation half-lives were 16.9/21.8 h for imipenem, 20.7/31.6 h for biapenem, 29.0 h for clavulanic acid (studied in broth only), 23.1/71.6 h for cefsulodin, 40.6/57.9 h for doripenem, 46.5/64.6 h for meropenem, 50.8/97.7 h for cefepime, 61.5/99.5 h for piperacillin, and >120 h for all other compounds. Broth stability decreased at higher pH. All drugs were ≥90% stable for 72 h in agar at 4°C. Degradation half-lives in water at 25°C were >200 h for all drugs except imipenem (14.7 h, at 1,000 mg/L) and doripenem (59.5 h). One imipenem supplement dose allowed concentrations to stay within ±31% of their target concentration. This study provides comprehensive stability data on β-lactams and BLIs in relevant in vitro media using LC-MS/MS. Future studies are warranted applying these data to antimicrobial susceptibility testing and assessing the impact of β-lactamase-related degradation.

Improved characterization of aminoglycoside penetration into human lung epithelial lining fluid via population pharmacokinetics

Aminoglycosides are important treatment options for serious lung infections, but modeling analyses to quantify their human lung epithelial lining fluid (ELF) penetration are lacking. We estimated the extent and rate of penetration for five aminoglycosides via population pharmacokinetics from eight published studies. The area under the curve in ELF vs plasma ranged from 50% to 100% and equilibration half-lives from 0.61 to 5.80 h, indicating extensive system hysteresis. Aminoglycoside ELF peak concentrations were blunted, but overall exposures were moderately high.

Unrecognized Potent Activities of Colistin Against Clinically Important mcr+ Enterobacteriaceae Revealed in Synergy with Host Immunity

Colistin (COL) is a cationic cyclic peptide that disrupts negatively-charged bacterial cell membranes and frequently serves as an antibiotic of last resort to combat multidrug-resistant Gram-negative bacterial infections. Emergence of the horizontally transferable plasmid-borne mobilized colistin resistance (mcr) determinant and its spread to Gram-negative strains harboring extended-spectrum β-lactamase and carbapenemase resistance genes threatens futility of our chemotherapeutic arsenal. COL is widely regarded to have zero activity against mcr+ patients based on standard antimicrobial susceptibility testing (AST) performed in enriched bacteriological growth media; consequently, the drug is withheld from patients with mcr+ infections. However, these standard testing media poorly mimic in vivo physiology and omit host immune factors. Here we report previously unrecognized bactericidal activities of COL against mcr-1+ isolates of Escherichia coli (EC), Klebsiella pneumoniae (KP), and Salmonella enterica (SE) in standard tissue culture media containing the physiological buffer bicarbonate. Moreover, COL promoted serum complement deposition on the mcr-1+ Gram-negative bacterial surface and synergized potently with active human serum in pathogen killing. At COL concentrations readily achievable with standard dosing, the peptide antibiotic killed mcr-1+ EC, KP, and SE in freshly isolated human blood proved effective as monotherapy in a murine model of mcr-1+ EC bacteremia. Our results suggest that COL, currently ignored as a treatment option based on traditional AST, may in fact benefit patients with mcr-1+ Gram negative infections based on evaluations performed in a more physiologic context. These concepts warrant careful consideration in the clinical microbiology laboratory and for future clinical investigation of their merits in high risk patients with limited therapeutic options.

Comprehensive whole genome sequencing with hybrid assembly of multi-drug resistant Candida albicans isolate causing cerebral abscess

Comprehensive whole genome sequencing (WGS) with hybrid assembly of a multi-drug resistant (MDR) Candida albicans (CA) isolate causing cerebral abscess was performed using Illumina paired end and Oxford Nanopore long read technologies. The innovative technologies utilized here enabled us to resolve fragmented assemblies, and implement comprehensive and detailed genomic analyses involved in antifungal resistance of Candida spp. Functionally important genes (MDR1, CDR2 and SQN2) involved in antifungal resistance were identified and a phylogenetic analysis of the clinical isolate was performed. Additionally, our clinical isolate was found to share 4 single nucleotide polymorphisms with two other sequenced strains of MDR C. auris (381 and 386) including translation elongation factor EF1α and EF3, ATPase activity associated proteins, and the lysine tRNA ligase.

Contribution of Streptococcus pyogenes M87 protein to innate immune resistance and virulence

Streptococcus pyogenes is a pre-eminent human pathogen, and classified by the hypervariable sequence of the emm gene encoding the cell surface M protein. Among a diversity of M/emm types, the prevalence of the M/emm87 strain has been steadily increasing in invasive S. pyogenes infections. Although M protein is the major virulence factor for globally disseminated M/emm1 strain, it is unclear if or how the corresponding M protein of M/emm87 strain (M87 protein) functions as a virulence factor. Here, we use targeted mutagenesis to show that the M87 protein contributes to bacterial resistance to neutrophil and whole blood killing and promotes the release of mature IL-1β from macrophages. While deletion of emm87 did not influence epithelial cell adherence and nasal colonization, it significantly reduced S. pyogenes-induced mortality and bacterial loads in a murine systemic infection model. Our data suggest that emm87 is involved in pathogenesis by modulating the interaction between S. pyogenes and innate immune cells.

Efficacy of pedicled anterolateral thigh flap for reconstruction of regional defects - a record analysis

BACKGROUND

The anterolateral thigh (ALT) flap was described as the fasciocutaneous flap. It can be harvested as a pedicled and/or free flap. Majority of the free flaps are harvested as a fasciocutaneous flap. Their use in head and neck reconstruction and limb trauma is well established. Apart from these advantages, this flap has various applications which are less utilized. ALT flap can be used as a myocutaneous flap along with vastus lateralis muscle. When muscle and fasciocutaneous flaps are required, both can be harvested as a chimeric flap which can cover two different regions of the wound. Moreover, harvest of the pedicled flap procedure is less time-consuming than that of a free flap. Since it has a long vascular pedicle, when used as pedicled flap, it can reach up to the gluteal region. To evaluate these less applied advantages of pedicled ALT flap, our study was undertaken. This study aimed to evaluate the efficiency of ALT flap in terms of the surface area of coverage, arc of rotation and the advantages of including vastus lateralis muscle as part of the flap.

METHODS

A retrospective record analysis of all pedicled ALT flap reconstruction of trochanteric, upper thigh, gluteal and flank regions from 2016 to 2018 was undertaken; 7 patients with 8 defects were included.

RESULTS

All the flaps healed successfully. There was no major necrosis of the flap and minor complications like wound gapping were found in three patients.

CONCLUSION

The ALT-vastus lateralis flap dimensions can be very large and can be easily harvested in a very short time. Vastus lateralis muscle harvested can be used to fill the defect or can be used as chimera to cover the defect. The use of muscle over long standing infective pressure sores can sterilize the wound bed and help in preventing recurrence. The vascularity of this flap is robust and highly reliable. Even after a maximum arc of rotation (up to 170°) all the flaps survived without any major complications.

Bacterial Membrane-Derived Vesicles Attenuate Vancomycin Activity against Methicillin-Resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) has evolved numerous antimicrobial resistance mechanisms and is identified as a serious public health threat by the World Health Organization and U.S. Centers for Disease Control and Prevention. The glycopeptide vancomycin (VAN) remains a cornerstone of therapy for severe MRSA infections despite increasing reports of therapeutic failure in hospitalized patients with bacteremia or pneumonia. Recently, the role of released bacterial-derived membrane vesicles (MVs) in antibiotic resistance has garnered attention. Here we examined the effect of exogenous MRSA-derived MVs on VAN activity against MRSA in vitro, using minimum inhibitory concentration and checkerboard assays, and ex vivo, incorporating components of host innate immunity such as neutrophils and serum complement present in blood. Additionally, the proteome of MVs from VAN-exposed MRSA was characterized to determine if protein expression was altered. The presence of MVs increased the VAN MIC against MRSA to values where clinical failure is commonly observed. Furthermore, the presence of MVs increased survival of MRSA pre-treated with sub-MIC concentrations of VAN in whole blood and upon exposure to human neutrophils but not human serum. Unbiased proteomic analysis also showed an elevated expression of MV proteins associated with antibiotic resistance (e.g., marR) or proteins that are functionally linked to cell membrane/wall metabolism. Together, our findings indicate MRSA-derived MVs are capable of lowering susceptibility of the pathogen to VAN, whole-blood- and neutrophil-mediated killing, a new pharmacodynamic consideration for a drug increasingly linked to clinical treatment failures.

Moriarty's sign - predictor of skin graft take

BACKGROUND

Resurfacing wound beds with split skin graft is the most common procedure in plastic surgery. Association of more pain in the donor site than in the recipient site has been used as a predictor of successful graft take by Stark in 1962 who termed it Moriartys sign.

PURPOSE

The aim of the study was: 1) to predict the successful take of skin graft by eliciting Moriartys sign; 2) to decide the day of first graft inspection based on Moriartys sign.

METHODS

The authors hereby present a prospective study in 100 patients who underwent wound resurfacing with split thickness skin graft at the Department of Plastic Surgery in a tertiary care center between January 2014 and June 2015. The area with more pain, absence of pain or equivocal response at the graft donor site was recorded on the visual analog scale for 10 days.

RESULTS

In this study, 80 patients had positive Moriartys sign, 12 patients had equivocal responses and 8 patients showed a negative sign. Patients with positive Moriartys sign underwent their first graft inspection on 10th postoperative day and showed 100% graft take. Twelve patients with equivocal response underwent first graft inspection on 5th day and had 70-80% graft take.  In 8 patients, with negative Moriartys sign first graft inspection done on 3rd day, the graft take was < 50%.

CONCLUSION

The study demonstrates that Moriartys sign is a reliable clinical predictor of split thickness skin graft take and may be useful as a guide to determine the day of first graft inspection. It is an effective method even for junior members of the surgical and nursing team to monitor parameters in relation to this sign. It can be practiced in a smaller group of hospitals, too. Hence, the authors recommend to integrate this clinical assessment in routine practice.

Necrotising Fasciitis: Appearances Can Be Deceptive

BACKGROUND

Necrotizing fasciitis is a potentially fatal infection of β hemolytic Group-A Streptococcus, often occurring in patients with other comorbidities, but can occur in healthy individuals as well. It commonly affects the extremities, perineum, and abdominal wall. The aim of this study was to highlight various presentations of necrotizing fasciitis in unusual anatomical sites with delayed diagnosis and treatment.

METHODS

In a retrospective analysis, seven cases of unusual presentations of necrotizing fasciitis were enrolled during a period of five years treated in a tertiary centre.

RESULTS

The patients were between 23 and 80 years. Four were males and three were females. Four out of seven were diabetic. All patients had septicemia (hypovolemic shock, with leucocytosis, thrombocytopenia and deranged coagulation parameters) on admission in the intensive care unit. All seven patients had minimal cutaneous manifestation and the remote primary pathology was diagnosed in two patients. Six patients out of seven survived and the morbid state continued in one patient in view of malignancy of rectum in one patient. The overall outcome was satisfactory in five out of seven cases.

CONCLUSION

Pain disproportionate to the local inflammation with florid constitutional symptoms should raise suspicion of necrotizing fasciitis. Early diagnosis, of stabilization of hemodynamics, emergency fasciotomy, staged debridement and the initiation of broad spectrum antibiotics reduced the morbidity and mortality. The disease may manifest with uncommon presentations and sometimes lead to the diagnosis of primary aetiology.

Azithromycin Exerts Bactericidal Activity and Enhances Innate Immune Mediated Killing of MDR Achromobacter xylosoxidans

Azithromycin (AZM), the most commonly prescribed antibiotic in the United States, is thought to have no activity against multidrug-resistant Gram-negative pathogens such as Achromobacter xylosoxidans (AX) per standard minimum inhibitory concentration testing in cation-adjusted Mueller Hinton Broth. Here we provide the first report of AZM bactericidal activity against carbapenem-resistant isolates of AX, with a multifold decrease in minimum inhibitory concentration across 12 clinical isolates when examined under physiologic testing conditions that better recapitulate the in vivo human environment. This pharmaceutical activity, evident in eukaryotic tissue culture media, is associated with enhanced AZM intracellular penetration and synergistic killing with human whole blood, serum, and neutrophils. Additionally, AZM monotherapy inhibited preformed AX biofilm growth in a dose-dependent manner together with a reduction in viable bacteria. In an illustrative case, AZM in combination with piperacillin-tazobactam exerted clear therapeutic effects in a patient with carbapenem-resistant AX mediastinitis, sternal osteomyelitis, and aortic graft infection. Our study reinforces how current antimicrobial testing practices fail to recapitulate the host environment or host-pathogen interactions and may misleadingly declare complete resistance to useful agents, adversely affecting patient outcomes. We conclude that AZM merits further exploration in the treatment of drug-resistant AX infections. Novel approaches to antimicrobial susceptibility testing that better recapitulate the host environment should be considered, especially as infections caused by multidrug-resistant Gram-negative bacterial pathogens are expanding globally with high morbidity and mortality.

Phage Therapy for a Multidrug-Resistant Acinetobacter baumannii Craniectomy Site Infection

In the era of antibiotic resistance, alternative treatment options for multidrug-resistant bacterial infections are being explored. We present a case of multidrug-resistant Acinetobacter baumannii infection treated with bacteriophages. Clinical trials are needed to further investigate bacteriophage therapy as an option to treat multidrug-resistant bacterial infections.

Listeria monocytogenes endocarditis: case report, review of the literature, and laboratory evaluation of potential novel antibiotic synergies

Endocarditis is a rare but serious manifestation of Listeria monocytogenes (LM). However, the optimal treatment strategy for LM endocarditis has yet to be established. Current antibiotic strategies for listeriosis include penicillin G or ampicillin (AMP) monotherapy, or AMP + gentamicin combination therapy which is often favored for endocarditis. The primary objective of our investigation was to assess the utility of AMP + ceftriaxone (CRO) and AMP + daptomycin (DAP) against LM, modeling less nephrotoxic antibiotic combinations traditionally used to manage resistant enterococcal endocarditis. Here we report a case of LM endocarditis, review the world literature, and evaluate alternative treatment strategies for listeriosis utilizing in vitro and ex vivo studies. The combination of AMP + CRO and AMP + DAP were each noted to have synergistic activity against a LM endocarditis isolate. Additionally, co-incubation of the isolate with sub-lethal concentrations of antibiotics (AMP, CRO, DAP, AMP + CRO or AMP + DAP) sensitized the bacterium to whole blood killing while pretreatment with CRO and DAP (at 1/4 MIC) sensitized the bacterium to neutrophil killing. However, these effects did not reflect potentiation of antibiotic activity to human cathelicidin peptide LL-37, which is abundant in neutrophils and highly active against LM. Interestingly, AMP pretreatment of the LM endocarditis isolate resulted in increased DAP binding to the bacterium when assessed by fluorescence microscopy. These in vitro and ex vivo studies suggest further investigation of combination therapy using AMP + CRO or AMP + DAP as an alternative treatment for LM infection is warranted.

Staphylococcus aureus Membrane-Derived Vesicles Promote Bacterial Virulence and Confer Protective Immunity in Murine Infection Models

Staphylococcus aureus produces membrane-derived vesicles (MVs), which share functional properties to outer membrane vesicles. Atomic force microscopy revealed that S. aureus-derived MVs are associated with the bacterial surface or released into the surrounding environment depending on bacterial growth conditions. By using a comparative proteomic approach, a total of 131 and 617 proteins were identified in MVs isolated from S. aureus grown in Luria-Bertani and brain-heart infusion broth, respectively. Purified S. aureus MVs derived from the bacteria grown in either media induced comparable levels of cytotoxicity and neutrophil-activation. Administration of exogenous MVs increased the resistance of S. aureus to killing by whole blood or purified human neutrophils ex vivo and increased S. aureus survival in vivo. Finally, immunization of mice with S. aureus-derived MVs induced production of IgM, total IgG, IgG1, IgG2a, and IgG2b resulting in protection against subcutaneous and systemic S. aureus infection. Collectively, our results suggest S. aureus MVs can influence bacterial-host interactions during systemic infections and provide protective immunity in murine models of infection.

Standard susceptibility testing overlooks potent azithromycin activity and cationic peptide synergy against MDR Stenotrophomonas maltophilia

OBJECTIVES

The Gram-negative bacillus Stenotrophomonas maltophilia (SM) is an emerging MDR opportunistic pathogen. Recent studies identify a potentially relevant activity of azithromycin against Gram-negative bacteria overlooked in standard bacteriological testing. We investigated azithromycin activity against SM in testing conditions incorporating mammalian tissue culture medium and host defence factors.

METHODS

MIC testing, chequerboard assays, time-kill assays and fluorescence microscopy were performed for azithromycin, the cationic peptide antibiotic colistin and the human defence peptide cathelicidin LL-37 alone or in combination in cation-adjusted Mueller-Hinton broth or mammalian tissue culture media. Azithromycin sensitization of SM to host immune clearance was tested in a human neutrophil killing assay and a murine pneumonia model.

RESULTS

We observed potent bactericidal activity of azithromycin against SM in mammalian tissue culture medium absent in bacteriological medium. Colistin and LL-37 strongly potentiated azithromycin killing of SM by increasing drug entry. Additionally, azithromycin sensitized SM to neutrophil killing and increased SM clearance in the murine pneumonia model.

CONCLUSIONS

Despite lack of activity in standard MIC testing, azithromycin synergizes with cationic peptide antibiotics to kill SM in medium mimicking tissue fluid conditions. Azithromycin, alone or in combination with colistin, merits further exploration in therapy of drug-resistant SM infections.

Azithromycin Synergizes with Cationic Antimicrobial Peptides to Exert Bactericidal and Therapeutic Activity Against Highly Multidrug-Resistant Gram-Negative Bacterial Pathogens

Antibiotic resistance poses an increasingly grave threat to the public health. Of pressing concern, rapid spread of carbapenem-resistance among multidrug-resistant (MDR) Gram-negative rods (GNR) is associated with few treatment options and high mortality rates. Current antibiotic susceptibility testing guiding patient management is performed in a standardized manner, identifying minimum inhibitory concentrations (MIC) in bacteriologic media, but ignoring host immune factors. Lacking activity in standard MIC testing, azithromycin (AZM), the most commonly prescribed antibiotic in the U.S., is never recommended for MDR GNR infection. Here we report a potent bactericidal action of AZM against MDR carbapenem-resistant isolates of Pseudomonas aeruginosa, Klebsiella pneumoniae, and Acinetobacter baumannii. This pharmaceutical activity is associated with enhanced AZM cell penetration in eukaryotic tissue culture media and striking multi-log-fold synergies with host cathelicidin antimicrobial peptide LL-37 or the last line antibiotic colistin. Finally, AZM monotherapy exerts clear therapeutic effects in murine models of MDR GNR infection. Our results suggest that AZM, currently ignored as a treatment option, could benefit patients with MDR GNR infections, especially in combination with colistin.

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Standard MIC testing conditions overlook a potent activity of azithromycin vs. multidrug-resistant Gram-negative bacteria.

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Colistin and endogenous host defense peptide LL-37 markedly potentiate azithromycin penetration into bacterial cells.

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Azithromycin reduced bacterial load and mortality in mouse models of multidrug-resistant Gram-negative infection.

Torsion of partial cleft of ear lobule

INTRODUCTION

Torsion is a well-known phenomenon involving organs with long mesentery. Torsion in the ear lobule is rare. Ear lobule is very well vascularized. In cases of partial cleft ear lobule, there is a small segment of lobule inferior to the cleft which is vascularized through the pedicles on either side of the cleft.

CASE REPORT

A lady aged 89 years presented with discoloration of the ear lobule. She was diagnosed as having gangrene of the central part of lobule. The segment of the lobule had undergone more than 360° torsion. She underwent debridement of gangrenous part and lobuloplasty.

DISCUSSION AND CONCLUSION

In our case laxity of the stretched lobule caused the torsion of the segment followed by gangrene. This rare complication indicates the need for correction of the cleft lobule not only for esthetic purpose, but also for the prevention of torsion.

Micropropagation of Pogostemon cablin Benth. through Direct Regeneration for Production of True to Type Plants

Multiple shoots from nodal explants of Pogostemon cablin Benth. MS supple-mented with 0.5 mg/l BAP initiated a mean of 45.66 shoots/nodal explant. Within four weeks of initiation, regenerated multiple shoots attained a height of 3.6 cm. Subsequent transfer of these in vitro derived nodal segments onto MS supplemented with BAP and Kn ( 0.5 mg/l), induced  a mean of 62.45 shoots. Higher concentration of either BAP or Kn more than 0.5 mg/l resulted in callus proliferation and showed hyperhydric shoots with morphological abnormalities. Rooting was readily achieved upon transfer of shoots on half strength MS supplemented with 100 mg/l activated charcoal. Rooted shoots, following acclimatization in greenhouse, were successfully transferred to soil with 91% survival. Also shoots regenerated in vitro were directly transplanted to soil and acclimatized. Tissue cultured plants were analyzed for oil content by employing gas chromatography and found that the patterns were similar to mother plants. This confirms the true to type nature of micropropagated plants. Key words: Micropropagation, Direct regeneration, Pogostemon cablin, organogenesis D.O.I. 10.3329/ptcb.v20i1.5971 Plant Tissue Cult. & Biotech. 20(1): 81-89, 2010 (June)

Security of payment for Hong Kong construction industry

In Hong Kong, getting paid is not always easy and the construction industry stands as an illustration of how much effort may be needed to achieve this and how adverse impacts can escalate from payment problems. At the moment, many jurisdictions have adopted some form of legislation or practical measures to enhance the ease and security of payment in the construction industry. Experience and insights from their operations provide guidance to Hong Kong for its way forward. By studying practices and feedback in other jurisdictions, this paper outlines and reviews the options and alternatives implemented for securing payment in the construction industry in Hong Kong. In addition, it also seeks to appraise their respective practicability for Hong Kong and highlight those areas to be considered if they are to be adopted or adapted for use in the Hong Kong construction industry. The ultimate aim is to provide an objective, balanced and reasoned overview for further study and discussion among stakeholders in the Hong Kong construction industry when moving forward. This is not intended to be an exhaustive review of all means adopted to achieve security of payment but aims to discuss those methods which are more likely to be suitable to be adopted in Hong Kong in the light of the circumstances and environment prevailing there. Furthermore, this study did not investigate the many modes of procurement that are available and which may address the concern of security of payment but focuses on the traditional form of contracts in use in Hong Kong. Public–private partnerships or private finance initiatives which would call for different discussions are not covered.