Evaluating decontamination protocols for the isolation of Mycobacterium ulcerans from swabs

Improved protocols for isolation of Mycobacterium ulcerans from clinical samples

BACKGROUND

The isolation and culture of Mycobacterium ulcerans (Mu) as a primary diagnostic modality for Buruli ulcer (BU) disease are limiting due to their low sensitivity and slow-growing nature. M. ulcerans cultures can also be overgrown with other bacteria and fungi. Culture, however, remains an important tool for the study of persisting viable M. ulcerans, drug susceptibility tests, and other molecular assays to improve management of the disease. The challenge of contamination with other fast-growing bacteria necessitates decontamination of clinical samples prior to culturing, but current methods may be too harsh, resulting in low yields of M. ulcerans. We aimed to evaluate a Tika-Kic decontamination process for M. ulcerans that uses supplements to stimulate M. ulcerans growth to improve recovery.

METHODS

Swab and Fine Needle Aspirate (FNA) samples were collected from 21 individuals with confirmed BU at baseline (week 0) and weeks 2 and 4 after initiating antibiotic treatment. Samples were decontaminated with Tika-Kic decontamination medium and the modified Petroff (NaOH) methods then inoculated each into Mycobacterium Growth Indicator Tube (MGIT) or Löwenstein Jensen (LJ) medium. Time to growth detection and confirmation by qPCR as well as the proportion of positive cultures for all three methods and the proportion of positive cultures for all three time points were documented. Common contaminating bacteria were also isolated and identified.

RESULTS

The proportion of M. ulcerans positive cultures obtained was higher for Tika-MGIT samples [14/43 (32%)] compared to Petroff-MGIT samples [10/43 (23%)] and Petroff-LJ samples [8/43 (19%)]. Baseline samples had a higher isolate proportion [17 (53%)] compared to samples collected after treatment initiation [9 (28%) for week 2 and 6 (19%) for week 4]. Contaminating bacteria isolated include Burkholderia cepacia, Pseudomonas aeruginosa, Pasteurella pneumotropica, Proteus mirabilis, Morganella morganii, Staphylococcus aureus and Enterococcus.

CONCLUSION

Our study shows an advantage for culturing Mycobacterium ulcerans from clinical samples using the Tika-Kic decontamination and growth medium. Further research is needed to refine sample processing to improve M. ulcerans recovery.

Molecular identification of mycobacterial infections in nonsputum specimens

BACKGROUND

Mycobacterial infections can manifest in various anatomical sites, necessitating the analysis of nonsputum specimens for accurate diagnosis. The aim of this study was to identify the molecular cases of mycobacterial infections in nonsputum specimens using polymerase chain reaction based assays and gene sequencing methods.

METHODS

This observational study examined 161 nonsputum samples that have been stored in the Clinical Microbiology Laboratory at Hasanuddin University Hospital. Samples were analyzed by microscopy and molecular detection methods according to the standard methods at the Clinical Microbiology Laboratory of Hasanuddin University. Descriptive statistics were utilized to summarize patient demographics, infection characteristics, and outcomes.

RESULTS

The samples were collected from patients with an average age of 39.82 years. The anatomical sites of specimen collection varied, with musculoskeletal organs and eyes being the most common. Microbiological analysis revealed a predominance of Gram positive bacteria, with polymicrobial morphology observed. Methicillin susceptible Staphylococcus aureus were the most frequently isolated organisms. Acid fast bacilli were detected in 8.1% of samples. Phylogenetic analysis, based on 16S rRNA gene sequencing, revealed similarities between the samples and known mycobacterial species, including Mycobacterium parmense, Mycobacterium lacus, and Mycobacterium dioxanotrophicus.

CONCLUSIONS

The findings highlight the microbial diversity observed in these infections. The study advocates for comprehensive diagnostic evaluations and targeted testing strategies based on both clinical and laboratory findings. This knowledge can contribute to improved diagnostic accuracy and optimized treatment strategies for mycobacterial infections.

Bacterial Contamination of Surgical Instruments Used at the Surgery Department of a Major Teaching Hospital in a Resource-Limited Country: An Observational Study

Surgical instruments, be they disposable or reusable, are essential in any surgical procedure. Reusable surgical instruments should be properly sterilized or disinfected before use. However, the protocols are not always followed accordingly. This results in sterilization and disinfection failures, leading to a possible increase in the incidence of surgical site infections. This observational study report on bacterial contaminants identified instruments used for surgical procedures in a major teaching hospital in a resource-limited country. In total, 207 pre-sterilized surgical instruments and instrument parts used at three units-the general surgical theater, and the gastrointestinal (GI) endoscopy and urology endoscopy (uro-endoscopy) units-within the surgical department were randomly sampled and examined for bacterial contamination. Bacteria isolates were identified, and their antimicrobial susceptibility patterns were determined. Bacteria isolates that were identified included Citrobacter spp., Citrobacter freundii, Bacillus cereus, Staphylococcus hominis, and Staphylococcus aureus. Bacillus cereus was the most predominant bacteria isolated (30/61, 49.1%), and Staphylococcus hominis the least (1/61, 1.6%). In terms of the number of isolates from the three units examined, the uro-endoscopy unit recorded the highest followed by the general surgical theater and the GI endoscopy. However, there was no association between the various units and bacteria isolated, and no significant difference between the number of isolates among the various units (p = 0.9467, χ2 = 0.1095). In this study, even though CFU per device or device part counted was less than 20, bacteria isolated from the instruments used for a surgical procedure is of great concern considering that the setting of the study is a major teaching hospital. Multi-drug resistance was observed in almost all the isolated bacteria. Sterilization processes should be strictly adhered to, taking into consideration the length and temperature in order to reduce the risk of using contaminated instruments in these environments. It is therefore recommended that similar studies should be carried out in surgical departments at different levels of hospitals to ascertain the extent of this problem.