Bacteriophages as therapeutic & disinfectant agents to tackle multidrug-resistant Acinetobacter baumannii

Background & objectives: Multidrug-resistant (MDR) Acinetobacter baumannii is a serious threat for human health worldwide. The studies on agents targeting A. baumannii are imperative due to identified A. baumannii co-infections in COVID-19. Bacteriophages are promising antibacterial agents against drug-resistant bacteria. This study intended to isolate bacteriophages against MDR A. baumannii from the water of river Ganga, to be used potentially as therapeutic and disinfectant particles. Methods: Acinetobacter phages were isolated from the Ganga water collected from Kanpur and further tested on 50 MDR A. baumannii isolates to determine host range. The phages were morphologically characterized by transmission electron microscopy. The disinfectant property of the isolated phages was tested by spraying of bacteriophage cocktail on MDR A. baumannii contaminated plastic surface, analyzed by colony-forming unit (CFU) and bioluminescence assay (adenosine triphosphate monitoring). Results: A total of seven bacteriophages were isolated against MDR A. baumannii. The bacteriophages lysed three MDR A. baumannii isolates out of 50 tested, showing narrow host range. Electron microscopy revealed hexagonal heads and long tails of bacteriophages, belonging to order Caudovirales. The bacteriophage cocktail reduced the MDR A. baumannii load efficiently on plastic surface, evidenced by reduction in CFUs and bioluminescence. Interpretation & conclusions: The findings of this study suggest that the isolated bacteriophages are potential lytic agents for MDR A. baumannii clinical isolates, and may be used as potential therapeutic agents as well as disinfectant to combat MDR A. baumannii with due consideration to phage host specificity, with further characterization.n

Exploring the Clinical Variables among Drug-Dependent HIV-Positive Patients: Implications for Treatment Strategies

This study explored the profile of HIV positive patients seeking treatment at a tertiary care addiction treatment facility. A retrospective study was done to collet detailed information on clinical characteristics: drug use (type, age of initiation, duration), general medical condition and past treatment history. The study included 138 patients with mean (SD) age 30.2 (8.3) years. Opioid dependence with injecting drug use (IDU) was diagnosed in 97% of the patients. The median age of injecting onset was 24.5 years (IQR 20-31 years). The most frequently injected substances were pheniramine (60.1%) and buprenorphine (59.4%). Past treatment seeking was reported by 57% patients and interestingly they were less likely to present any medical condition (2 =69.611, p < 0.001). Variability in the age of onset of drug use indicates the need for broad based approach to prevent IDU and motivation to seek treatment may lead to better health conditions.

Induction of resistant mutants of Salmonella enterica serotype Typhi under ciprofloxacin selective pressure.

Background & objectives: Infection with Salmonella enterica serovar Typhi (hereafter S. Typhi) is an important public health problem in India. There has been an increase in the number of reported clinical failures to ciprofloxacin treatment but the data on possible mechanism of failure are limited. One mechanism that has been widely reported and found associated with ciprofloxacin resistance, is the mutations in target genes in QRDR (quinolone resistance determining region). It is hypothesized that mutations in DNA gyrase or topoisomerase IV result in therapeutic failure under selective pressure of antibiotic while the patient is on treatment. We undertook in vitro sequential selection studies to expose the clinical isolates of S. Typhi to different concentration of ciprofloxacin to study the role of antibiotic selective pressure in the development of mutations in QRDR. Methods: Total 26 clinical isolates were divided in to two parts: part I included six isolates obtained from three patients with relapse of enteric fever and part II included 20 isolates with different ciprofloxacin MIC levels. For in vitro induction of mutation experiment, five S. Typhi isolates were selected which included three NAS (nalidixic acid sensitive) and 2 NAR (nalidixic acid resistant) S. Typhi. These isolates were grown under increasing concentrations of ciprofloxacin and mutations acquired in QRDR of DNA gyrase (gyrA and gyrB) and topoisomerase IV (parC and parE) were investigated by sequencing. Results: For the isolates included in the part I of the study, it was found that the MIC to ciprofloxacin increased in the isolates obtained during the relapse of enteric fever as compare to the first isolate. All isolates had single mutation in gyrA gene at S83 without additional mutation in the second isolate. In the second part of the study, the nine isolates with varying MICs to ciprofloxacin also had single mutation in gyrA gene at S83 and another six had triple mutations, two mutations in gyrA gene (at S83 and D87) and one mutation in parC gene (at S80). In in vitro induction of mutation experiment, all mutated isolates showed triple mutation (two mutation in gyrA and one in parC gene) while no mutations were found in wild isolates. Interpretation & conclusions: Upon exposure to the step-wise increased concentration of ciprofloxacin, isolates become more tolerant to the ciprofloxacin and showed 2-4 fold higher MICs without new mutation after 8 μg/ml. So the accumulation of mutations under continuous ciprofloxacin pressure and tolerance of the mutant isolates led to the clinical failure. These results also suggested that there could be another mechanism responsible for resistance.

Multiple locus sequence typing of Salmonella Typhi, isolated in north India - a preliminary study.

Background & objectives: In India enteric fever is a major public health problem and Salmonella Typhi is the most common aetiologic agent. Any control strategy for such infections depends to a large extent on the understanding of the disease and relatedness of strains across the world. Multi locus sequence typing (MLST) is one such method of genotyping of bacteria based upon housekeeping genes of known function and chromosome position. MLST data of pathogens are important to determine the molecular evolution by a stable and reproducible method. This study was undertaken to determine the sequence types of representatives S. Typhi isolates obtained from enteric fever patients in a tertiary care centre in north India, over a period of 20 years (1990-2010). Methods: A total of 30 representative isolates of S. Typhi identified by biochemical and serological tests were subjected to multi locus sequence typing (MLST). Seven housekeeping genes of known function and chromosome position were used for the typing by MLST. Sequencing was carried out by using an automated DNA sequencer and results were analyzed to generate phylogenetic tree. Results: MLST pattern grouped S. Typhi into two sequence types- ST1 and ST2. ST1 was predominantly present followed by ST2. Interpretation & conclusions: By MLST the presence of both sequence types, ST1 and ST2, was found in S. Typhi isolates in our region. Predominately ST1 was present followed by ST2. These preliminary results corroborate the global distribution of both sequence types of S. Typhi and also emphasize for the continuous screening of S. Typhi.

Primary meningococcal polyarthritis in a young man.

We report a rare occurrence of primary meningococcal polyarthritis in a 19-year-old man. The fluid in the elbow joint showed Gram-negative diplococci but the culture was sterile. The diagnosis was confirmed by polymerase chain reaction targeting crgA gene of Neisseria meningitidis.