Distribution of bacterial contamination in a teaching hospital in Tehran - a special focus on Staphylococcus aureus

A comparative study on antibiotic resistance and virulence properties of Staphylococcus aureus isolated from hospitalized patients and hospital environment

BACKGROUND

We compared the characteristics of clinical Staphylococcus aureus and S. aureus isolated from environmental surfaces in 3 hospitals.

METHODS

Clinical S. aureus isolates were collected from hospitalized patients. Environmental surfaces were sampled from the rooms of patients infected with S. aureus. After identifying rooms with the target organism, 3-5 high-touch surfaces in patient care areas were sampled using swabs before room cleaning by environmental services. S. aureus isolates were subjected to genotyping, antimicrobial susceptibility testing, and virulence determinant screening. The isolates were analyzed for integron content and sequences of variable region amplification products.

RESULTS

There were epidemiologically unrelated 79 clinical and 62 environmental S. aureus isolates. Overall, 11.4% of clinical and 59.7% of environmental isolates were methicillin-resistant. The environmental and clinical S. aureus exhibited very different virulence profiles: 79% of the environmental isolates were negative for virulence genes compared to 2.5% of clinical isolates (P < .001). Environmental isolates were more resistant to antibiotics compared to clinical isolates. Class 1 integrons were only detected in 7 of 62 environmental isolates, of which 3 isolates had integrons with cysteine synthase cassette, 1 had aadA1, and 1 had an unknown cassette.

CONCLUSION

These data indicate the different characteristics between environmental and clinical S. aureus, which may reflect different reservoirs from which the 2 groups acquired the strains.

Hospital-Based Air-Borne and Surface-Borne Bacterial Pathogens and Their Antimicrobial Profiles in Wolaita Sodo, Southern Ethiopia

Background. It is well documented that hospital environments are the niche/reservoir of many clinically important microorganisms, including multidrug-resistant air-borne and surface-borne pathogens. This problem is the most pressing public health concern, particularly in developing countries like Ethiopia, due to its poor infection management system. This study was planned to detect air-borne and surface-borne bacterial pathogens and their antimicrobial resistance patterns in Wolaita Sodo University Comprehensive Hospital, Southern Ethiopia. Method. A laboratory-based cross-sectional study was conducted from May to July 2021. Swabbing and open-plate sample collection methods were used to collect specimens. Standard bacteriological techniques were used to isolate and identify bacterial pathogens. The Mueller-Hinton agar was used to detect the drug susceptibility pattern of bacteria by using the Kirby-Bauer disc diffusion method. Result. From a total of 323 samples tested, 118 (36.5%) showed the growth of bacteria. The detection rate of bacterial pathogens in the intensive care unit (35.4%) was higher than in operation theater. From the total of 118 bacterial isolates, 39.8%, 27.9%, 20.3%, and 11.5% of S. aureus, P. aeruginosa, Klebsiella pneumoniae, and E. coli, respectively, were surface-borne. Whereas 37%, 25%, 20.83, and 16.6% of S. aureus, P. aeruginosa, Klebsiella species, and E. coli, respectively, were air-borne. S. aureus showed a 19.04 to 80.9% range of antimicrobial resistance to different classes of antibiotics from surface specimens. A 12.5–100% range of antibiotic resistance levels was detected for all Gram-negative surface-borne bacterial pathogens. P. aeruginosa was 66.7%, 73.3%, and 73.3% resistant to gentamicin, chloramphenicol, and ceftriaxone, respectively. K. pneumoniae showed 75% and 87.5% resistance to ceftriaxone and ciprofloxacin, respectively, and a completely ampicillin-resistant E. coli was detected. From a total of 48 bacterial pathogens identified from surfaces in the intensive care unit, 34 (70.8%) developed multidrug resistance. Conclusion. A significant prevalence of surface-borne bacterial pathogens was detected. This study revealed that S. aureus, P. aeruginosa, K. pneumoniae, and E. coli were nosocomial infection concerns of the hospital, and this could be the reason for different types of hospital acquired infections in the study area. A high prevalence of MDR was detected in the most surface-borne bacterial isolates.

Bacterial Pathogens and Their Antimicrobial Resistance Patterns of Inanimate Surfaces and Equipment in Ethiopia: A Systematic Review and Meta-analysis

Background

Hospital-acquired infections have remained a serious cause of mortality, morbidity, and extended hospitalization. Bacterial contamination of inanimate surfaces of the hospital environment and equipment is considered a major contributing factor to the development of several nosocomial infections worldwide. The hospital environment and many devices are an important reservoir of many clinically important bacterial agents including multidrug-resistant pathogens. Therefore, this systematic review and meta-analysis are aimed at investigating bacterial pathogens and their antimicrobial resistance patterns of inanimate surfaces and equipment in Ethiopia.

Methods

An exhaustive literature search was carried out using the major electronic databases including PubMed, Web of Science, MEDLINE, EMBASE, CINAHL, Google Scholar, Cochrane Library, Scopus, and Wiley online library to identify potentially relevant studies without date restriction. Original articles which address the research question were identified, screened, and included using the PRISMA flow diagram. Data extraction was prepared in Microsoft Excel, and data quality was assessed by using 9-point Joanna Briggs Institute critical appraisal tools. Then, data were exported to STATA 16.0 software for analyses of pooled estimation of outcome measures. Estimation of outcome measures at a 95% confidence interval was performed using DerSimonian-Laird's random-effects model. Finally, results were presented via text, figures, and tables.

Results

A total of 18 studies with 3058 bacterial isolates recovered from 3423 swab specimens were included for systematic review and meta-analysis. The pooled prevalence of bacterial contamination of inanimate surfaces and equipment was found 70% (95% CI: 59, 82). Among the Gram-negative bacterial species, the prevalence of ampicillin-resistant K. pneumoniae was the highest 80% (95% CI: 78, 92) followed by Citrobacter species 78% (95% CI: 57, 83).

Conclusion

This study has shown a high prevalence of bacterial contamination of inanimate surfaces and equipment in Ethiopia.

Impact of culture media and sampling methods on Staphylococcus aureus aerosols

Staphylococcus aureus has been detected indoors and is associated with human infection. Reliable quantification of S. aureus using a sampling technique followed by culture assay helps in assessing the risks of human exposure. The efficiency of five culture media and eight sampling methods in recovering S. aureus aerosols were evaluated. Methods to extract cells from filters were also studied. Tryptic soy agar (TSA) presented greater bacterial recovery than mannitol salt agar (MSA), CHROMagar staph aureus, Chapman stone medium, and Baird-Park agarose (P < 0.05). Moreover, 93 ± 2%-95 ± 2% and 42 ± 1%-49 ± 2% of S. aureus were, respectively, recovered by a 15-min heating of gelatin filters and 2-min vortex of polycarbonate (PC) filters. Evaluation of two filtration (IOM with gelatin filter and cassette with PC filter), two impaction (Andersen 1-STG loaded with TSA and MSA) and four impingement methods [AGI-30 and BioSampler filled with Tween mixture (TM) and phosphate-buffered saline (PBS)] revealed the BioSampler/TM performed best over 30 and 60 min of sampling (P < 0.05), while low recovery efficiencies were associated with the IOM/gelatin, cassette/PC, and AGI-30/PBS combinations (P < 0.05). In addition to BioSampler/TM, collecting S. aureus onto TSA from the Andersen 1-STG is also recommended, as it is the second best method at the 60-min sampling (P < 0.05).

Methods for quantifying Staphylococcus aureus in indoor air

Staphylococcus aureus has been detected in indoor air and linked to human infection. Quantifying S. aureus by efficient sampling methods followed by appropriate sample storage treatments is essential to characterize the exposure risk of humans. This laboratory study evaluated the effects of sampler type (all-glass impinger (AGI-30), BioSampler, and Andersen one-stage sampler (Andersen 1-STG)), collection fluid (deionized water (DW), phosphate-buffered saline (PBS), and Tween mixture (TM)), and sampling time (3-60 min) on cell recovery. Effects of storage settings on bacterial concentration were also assessed over 48 h. Results showed BioSampler performed better than Andersen 1-STG and AGI-30 (P < 0.05) and TM was superior to PBS and DW (P < 0.05). An increase in sampling time negatively affected the recoveries of cells in PBS of BioSampler and AGI-30 (P < 0.05), whereas cell recoveries in TM were increased at sampling of 6-15 min compared with 3 min. Concentrations of cells collected in PBS were decreased with storage time at 4 and 23 °C (P < 0.05), while cells stored in TM showed stable concentrations at 4 °C (P > 0.05) and increased cell counts at 23 °C (P < 0.05). Overall, sampling by BioSampler with TM followed by sample transportation and storage at 4 °C is recommended.

Molecular investigation of Staphylococcus aureus isolated from the patients, personnel, air and environment of an ICU in a hospital in Tehran

BACKGROUND

The aim of this study was to determine the prevalence and characteristics of Staphylococcus aureus isolates from the patients, staff, air and environments of an ICU in a hospital in Tehran.

MATERIALS AND METHODS

During this study, 37 S. aureus isolates were collected and analyzed via the spa typing method.

RESULTS

Of the 37 S. aureus isolates, 35 (94%) were methicillin resistant (MRSA), 28 (76%) were identified as SCCmec types III or IIIA, four (10%) were identified as SCCmec types I or IA and three (8%) were identified a SCCmec type IV. All of the MRSA isolates were resistant to oxacillin and contained mecA. The isolates were all spa typed and found to comprise 11 spa types, including t7688, t7689, and t7789, which have not previously been reported. The spa type t7688 was isolated from the hands of two ICU personnel. The spa type t7689 was observed among five isolates from the air and the environment. The spa type t7789 was observed among three isolates from the patients, ventilators and the air. The majority of the isolates (43%) belonged to spa types t030 and t037.

CONCLUSION

Our results revealed that MRSA strains that were isolated from the air, the environment of the ICU and the patients who were colonized or infected with MRSA often exhibited the same spa and SCCmec types. These results also reveal that the isolates from the patients and environment were usually indistinguishable.