- Volume 3, Issue 10, 2021
Volume 3, Issue 10, 2021
- Research Articles
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Bovine apo-lactoferrin affects the secretion of proteases in Mannheimia haemolytica A2
More LessMannheimia haemolytica serotype A2 is the main bacterial causative agent of ovine mannheimiosis, a disease that leads to substantial economic losses for livestock farmers. Several virulence factors allow M. haemolytica to colonize the lungs and establish infection. Virulence factors can be directly secreted into the environment by bacteria but are also released through outer membrane vesicles (OMVs). In addition, due to the abuse of antibiotics in the treatment of this disease, multidrug-resistant bacterial strains of M. haemolytica have emerged. One therapeutic alternative to antibiotics or an adjuvant to be used in combination with antibiotics could be lactoferrin (Lf), a multifunctional cationic glycoprotein of the mammalian innate immune system to which no bacterial resistance has been reported. The aim of this work was to determine the effect of bovine iron-free Lf (apo-BLf) on the production and secretion of proteases into culture supernatant (CS) and on their release in OMVs. Zymography assays showed that addition of sub-MIC concentrations of apo-BLf to M. haemolytica cultures inhibited protease secretion without affecting culture growth. Biochemical characterization revealed that these proteases were mainly cysteine- and metalloproteases. The secretion of a 100 kDa metalloprotease was inhibited by sub-MIC concentrations of apo-BLf since this protease was present in the cytoplasm and OMVs but not in CS proteins, as corroborated by Western blotting. On the other hand, proteases produced by M. haemolytica caused cleavage of apo-BLf. However, when Lf is cleaved, peptides known as lactoferricins, which are more bactericidal than natural Lf, can be produced. M. haemolytica A2 protease-mediated degradation of host tissue proteins could be an important virulence factor during the infectious process of pneumonia in ovines. The mechanism of M. haemolytica protease secretion could be inhibited by treatment with apo-BLf in animals.
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Photodynamic antimicrobial chemotherapy coupled with the use of the photosensitizers methylene blue and temoporfin as a potential novel treatment for Staphylococcus aureus in burn infections
Photodynamic antimicrobial chemotherapy (PACT) is a novel alternative antimicrobial therapy that elicits a broad mechanism of action and therefore has a low probability of generating resistance. Such properties make PACT ideally suited for utilization in localized applications such as burn wounds. The aim of this study was to determine the antimicrobial activity of MB and temoporfin against both a S. aureus isolate and a P. aeruginosa isolate in light (640 nm) and dark conditions at a range of time points (0–20 min). A Staphylococcus aureus isolate and a Pseudomonas aeruginosa isolate were treated in vitro with methylene blue (MB) and temoporfin under different conditions following exposure to light at 640 nm and in no-light (dark) conditions. Bacterial cell viability [colony-forming units (c.f.u.) ml−1] was then calculated. Against P. aeruginosa , when MB was used as the photosensitizer, no phototoxic effect was observed in either light or dark conditions. After treatment with temoporfin, a reduction of less than one log (7.00×107 c.f.u. ml−1) was observed in the light after 20 min of exposure. However, temoporfin completely eradicated S. aureus in both light and dark conditions after 1 min (where a seven log reduction in c.f.u. ml−1 was observed). Methylene blue resulted in a loss of S. aureus viability, with a two log reduction in bacterial viability (c.f.u. ml−1) reported in both light and dark conditions after 20 min exposure time. Temoporfin demonstrated greater antimicrobial efficacy than MB against both the S. aureus and P. aeruginosa isolates tested. At 12.5 µM temoporfin resulted in complete eradication of S. aureus . In light of this study, further research into the validity of PACT, coupled with the photosensitizers (such as temoporfin), should be conducted in order to potentially develop alternative antimicrobial treatment regimes for burn wounds.
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Antimicrobial properties of phytohormone (gibberellins) against phytopathogens and clinical pathogens
More LessThe in vitro antimicrobial potential of physiologically active diterpenoid plant-derived gibberellins (gibberellic acids; GAs) was tested on microbial pathogens of significance to plant and human health. The racemic enantiomer GA3 produced varying inhibitory effects against a wide range of plant host disease causal agents (phytopathogens) comprising fungi, oomycetes and bacteria. The results showed that GA3 effected either strong growth arrest of phytopathogenic fungi or holistic biocidal effects on oomycete and phytopathogenic fungi at higher concentration (>10–50 mM) and increased hyphal extension growth when the concentration of GA3 was lowered (<10−0.1 mM). When human clinical pathogenic bacteria cohorts were challenged with gibberellin enantiomers, viz GA1, GA4, GA5, GA7, GA9 and GA13 (50 mM), employing Kirby–Bauer disc bioassay methods for assessment of their efficacies, no inhibitory effect was seen with gibberellin enantiomers, viz GA1, GA3, GA5 and GA13, while GA4 inhibited all human clinical bacterial organisms examined, with GA7 and GA9 showing limited activity. The antibiotic effects of enantiomeric diterpenoid phytohormones evinced in our preliminary study raise prospects for further studies to fully examine their potential therapeutic value for human healthcare and their compliance with cytotoxicity and other ethical considerations in the future.
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- Short Communications
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SARS-CoV-2 IgG antibody responses in rt-PCR-positive cases: first report from India
Introduction. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody responses remain poorly understood and the clinical utility of serological testing is still unclear.
Aim. To understand the relationship between the antibody response to SARS-CoV-2 infection and the demographics and cycle threshold (C t) values of confirmed RT-PCR patients.
Methodology. A total of 384 serum samples were collected from individuals between 4–6 weeks after confirmed SARS-CoV-2 infection and tested for the development of immunoglobulin class G (IgG) against SARS-CoV-2. The C t values, age, gender and symptoms of the patients were correlated with the development of antibodies.
Results. IgG positivity was found to be 80.2 % (95 % CI, 76.2–84.2). Positivity increased with a decrease in the C t value, with the highest (87.6 %) positivity observed in individuals with C t values <20. The mean (±sd) C t values for IgG positives and negatives were 23.34 (±6.09) and 26.72 (±7.031), respectively. No significant difference was found for demographic characteristics such as age and sex and symptoms and antibody response. The current study is the first of its kind wherein we have assessed the correlation of the RT-PCR C t with the development of IgG against SARS-CoV-2.
Conclusion. Although C t values might not have any relation with the development of symptoms, they are associated with the antibody response among SARS-CoV-2-infected individuals.
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Genetic characterization of co-trimoxazole non-susceptible Streptococcus pneumoniae isolates from Indonesia
We investigated the genetic variation of folA and folP genes encoding dihydropteroate synthase (DHPS) and dihydrofolate reductase (DHFR) enzymes amongst trimethoprim/sulfamethoxazole (co-trimoxazole) non-susceptible Streptococcus pneumoniae isolated from the Indonesian population. Archived S. pneumoniae isolates were screened for the presence and analysis of folA and folP genes using the polymerase chain reaction sequencing method. We found that 80 % of co-trimoxazole non-susceptible isolates (n=30/39) showed a 6 bp insertion in the sulphonamide-binding site of DHPS. The Asp-92-Ala and Ile-100-Leu substitutions were more common on DHFR (42 %; 22/53) followed by the Asp-92–Ala, Glu-94–Asp and Ile-100–Leu substitutions (32 %; 17/53). The combination of the Ile-100–Leu substitution at the DHFR region and the 6 bp insertion was the most dominant combination among isolates having both folA and folP genes.
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Identification of epidemic scarlet fever group A Streptococcus strains in the paediatric population of Houston, TX, USA
More LessScarlet fever (SF) has recently been associated with group A streptococcal (GAS) strains possessing multidrug resistance and specific streptococcal exotoxins. We screened a local surveillance collection of GAS emm12 strains in Houston, TX, USA for antimicrobial resistance and identified a single isolate matching the antimicrobial resistance pattern previously reported for SF clones. Using whole-genome sequencing and combining genome sequence data derived from national surveillance databases, we identified additional emm12 GAS clones similar to those associated with prior SF outbreaks, emphasizing the need for continued surveillance for epidemic emergence in the USA.
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- Case Reports
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Stenotrophomonas maltophilia as a rare cause of meningitis and ventriculoperitoneal shunt infection
Stenotrophomonas maltophilia is an extremely rare pathogen responsible for ventriculoperitoneal shunt infection and meningitis. This young female patient with history of multiple shunt revisions in the past, came to us with shunt dysfunction and exposure of the ventriculoperitoneal shunt tube in the neck. The abdominal end of the shunt tube was seen migrating into the bowel during shunt revision. The cerebrospinal fluid analysis showed evidence of Stenotrophomonas maltophilia growth. This is the first reported case of Stenotrophomonas maltophilia meningitis associated with ventriculoperitoneal shunt migration into the bowel.
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Infection with Clostridioides difficile ribotype 046 in a paediatric liver transplant patient
Clostridioides difficile causes nosocomial diarrhoea associated with antibiotic use and immunodeficiency. Although the number of paediatric C. difficile infections (CDIs) has increased worldwide, there are few studies on the molecular characterization of strains causing CDIs among children. We report the clinical features and strain molecular characterization of a CDI in a female child with a history of liver transplantation at 7 months of age. This is the first report of the 046 ribotype causing paediatric diarrhoea.
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Erosion of the sella turcica and pituitary expansion secondary to polymicrobial brain abscesses: a case report
More LessIntroduction. Brain abscesses can lead to a diverse array of complications, especially when they are polymicrobial in nature. Multiple underlying pathogens may present with a unique set of clinical symptoms which require an early identification and treatment. Skull base osteomyelitis with sellar floor erosion and pituitary involvement with SIADH are such rare complications of brain abscesses which have never been reported previously in the literature.
Case Presentation. We report the case of an immunocompetent 38-year-old male with altered mental sensorium and left hemiparesis due to polymicrobial brain abscess which required surgical evacuation. The post-operative recovery was complicated by severe hyponatremia secondary to SIADH which was treated uneventfully. Radiological imaging demonstrated pituitary enlargement with herniation through an eroded sella turcica without active CSF leak. Patient responded well to the antibiotic therapy based on microbiological susceptibility testing with a complete resolution of the pituitary enlargement on radiological follow-up.
Conclusion. Conservative treatment with targeted antibiotics can lead to the resolution of pituitary enlargement secondary to a brain abscess. However, a close clinical follow-up is required to look for a CSF leak considering the sellar floor erosion due to osteomyelitis.
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- Case Series
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Candida utilis: a rare cause of septicemia in children
Candida utilis is an emerging fungal pathogen in blood. The main aim of this study was to describe the prevalence, methods of speciation and antifungal susceptibility of Candida utilis at a tertiary care centre.
Methods. This was a retrospective study carried out at a tertiary care centre in South India. Over a period of 1 year, three Candida utilis were isolated from blood culture identified by MALDI–TOF MS Version 3.2 and were confirmed by ITS sequencing. Susceptibility testing was carried out by micro broth dilution.
Results. All three patients had a common risk factor of prolonged ICU stay but the source of infection could not be identified. Candida utilis isolates were identified by MALDI–TOF and confirmed by ITS sequencing. They were pansusceptible to all tested antifungal drugs. Among these, two patients who were treated in hospital had good clinical outcome and response to antifungal drugs. A third patient was lost to follow up.
Conclusion. Candida utilis was predominantly seen between 0–3 month olds. Conventional methods of speciation were unable to identify C. utilis to species level. Rapid identification was done by MALDI–TOF MS and confirmed by sequencing. Rapid identification leads to prompt treatment and favours a good clinical outcome.
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