A Prospective Study to Assess the Optimal Incubation Times for Culture and Aerobic Bacterial Profile in Prosthetic Joint Infections.

Introduction With an increase in the number of total joint arthroplasties, the count of prosthetic joint infections (PJIs) is also increasing and has become a nightmare for an orthopaedic surgeon. Microbiological diagnosis is important for administering definitive antimicrobial treatment. Negative culture reports hamper patient management and prolonged incubation periods have increased the culture yield but at the risk of culture contamination in conventional microbiology settings. Thus, we aimed to optimize the best incubation time for culture and the aerobic bacterial profile of PJIs. Material and Methods Over a year, samples from clinically suspected PJI patients were collected and processed for culture using standard techniques. The samples were incubated for up to 10 days with daily subculturing on to solid media. The bacterial isolates were identified and antibiotic susceptibility was performed. Results Out of 200 patients, 105 were included in the study and samples were collected in triplicate. In 70 cases culture was positive and 35 were culture negative PJIs. Mean incubation days to culture positivity was 3.6 days with 97.14% culture positivity seen by the seventh day of incubation. Twenty-four percent methicillin-resistant Staphylococcus aureus , and more than 50% extended spectrum ß lactamase producing Klebsiella pneumoniae and Escherichia coli were isolated. Discussion Culture positivity in PJIs provides definitive evidence of infection and guides the treatment. Increasing the incubation times can help in maximizing the culture yield, and we found that 97.14% pathogens grew within 7 days of incubation. Prolonging it further would not provide an added advantage especially in a resource-constraint setting.

Isolation of Morganella Morganii and Providencia Species from Clinical Samples in a Tertiary Care Hospital in North India.

INTRODUCTION: The members of the tribe Proteeae, Morganella and Providencia are being increasingly recognized as important pathogens. The spectrum of disease caused by them is wide and in reported cases, the mortality is high. Previously both of these pathogens were considered to be rare pathogens as the potential to cause nosocomial transmission and infection was not much studied. But their phenomenal evolution and increase in multidrug-resistance (MDR) strains of these pathogens are posing a major threat toward public health throughout the world. METHODS: This present study was carried out from July 2018 to December 2018 on all the pus and body fluid samples that were received in the Department of Microbiology. Samples were processed as per the standard Microbiological guidelines and also were analyzed for their antimicrobial susceptibility profile as per Clinical Laboratory Standards Institute. RESULTS: Out of 8425 samples received, 2140 were culture positive, amongst which 19 samples (0.89%) were positive for Providencia species (9) and Morganella morganii(10). The male : female ratio of these 19 patients was 2.8 : 1 and maximum patients (13) belonged to 20-60 years. As far as risk factors are concerned, maximum patients were diabetics (7) followed by abnormal liver function tests (6), concomitant UTI (6), history of invasive procedure (5), prior exposure to antibiotics (5) and urinary catheterization (4). About 6 were polymicrobial infections. Antibiotic susceptibility patterns revealed that Providencia strains were sensitive to ampicillin- sulbactum (77.7%) and amikacin (77.7%), while all Morganella strains were 100% sensitive to tobramycin and piperacillintazobactam. CONCLUSION: This study heralds in need for more research in this area as infections caused by these two pathogens are on the rise. Moreover, resistance to antimicrobials is also an increasingly common problem thus delaying the treatment and prognosis of the disease.

Characterization and antimicrobial susceptibility of coagulase-negative staphylococci isolated from clinical samples.

PURPOSE: This study has been done to speciate coagulase-negative staphylococci (CoNS) and also study their antibiotic susceptibility pattern isolated from clinical samples. MATERIALS AND METHODS: A total of 120 consecutive CoNS were isolated from various clinical samples such as blood, pus, wound swab, drain fluid, tracheal aspirate, peritoneal fluid, and pleural fluid over a period of 6 months. CoNS were identified by characteristic growth on media such as Blood agar and MacConkey agar. Speciation and identification were done by a range of biochemical testing such as PYR broth hydrolysis, novobiocin resistance, polymyxin B sensitivity, and then by matrix-assisted laser desorption ionization-time of flight. Antibiotic susceptibility of the isolates was done by Kirby-Bauer disk diffusion method as per CLSI 2017 guidelines. RESULTS: Among the 120 isolates, the most common species was Staphylococcus epidermidis (56.67%) followed by Staphylococcus haemolyticus (21.67%), Staphylococcus lugdunensis (11.67%), Staphylococcus caprae (5%), Staphylococcus cohnii (3.33%), and finally Staphylococcus vitulinus (1.67%). Good in vitro susceptibility was noted toward linezolid (100%), vancomycin (100%), teicoplanin (100%), and doxycycline (80.2%). The antibiotics to which resistance was seen were penicillin (96.5%), ciprofloxacin (57.1%), and oxacillin (45.5%). MR CoNS in our study ranged from 50% to 68.67%. CONCLUSION: Antibiotic resistance in CoNS is increasing toward penicillin, ciprofloxacin, and oxacillin as found in our study. The antibiotics such as vancomycin, teicoplanin, linezolid, and doxycycline which showed good in vitro susceptibility, therefore, should be kept as reserve drugs and used judiciously.