The prevalence and microbiological features of Staphylococcus species isolation from healthcare personnel in dental clinic in Tripoli, Libya

¹Department of Biological Sciences, School of Basic Sciences, Libyan Academy of Graduate Studies, Tripoli, Libya, ²Faculty of Medical Technology, University of Aljfarah, Aljfarah, Libya, ³Faculty of Dentistry, Cairo University, Cairo, Egypt, ⁴Burns and Plastic Surgery Centre, Tripoli, Libya, ⁵Department of Microbiology and Parasitology, Faculty of Veterinary Medicine, University of Tripoli P.O. Box 13362, Tripoli, Libya

^&Corresponding author
Mohamed Omar Ahmed, Department of Microbiology and Parasitology, Faculty of Veterinary Medicine, University of Tripoli, Tripoli, Libya

To the editors of the Pan African Medical Journal    

Methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant coagulase-negative staphylococci (MRCoNS) are increasingly reported from different healthcare settings, including dental clinics, showing variable epidemiological distribution and evolving characteristics [1]. These multidrug-resistant strains showed important virulent traits, presenting public health and zoonotic [2-4]. However, data concerning dental clinical settings on these drug-resistant pathogens are insufficient and limited. The aim of the current study was to investigate the carriage and antimicrobial susceptibility patterns of Staphylococcus species isolated from dental healthcare workers (HCWs) in Tripoli between February and March 2022. The HCWs were included on the basis of not suffering from any clinical conditions or being under any therapeutic treatment, including antimicrobial drugs, at least 3 months prior to sampling. Information from each participant was collected using a designated questionnaire, which included general and clinical information. A total of 274 HCWs from 38 dental healthcare settings (13 public and 25 private clinics) were volunteered. The age range was from 19 to 70 years (mean age of 31.65 years) and represented by 73% dentists (n=200/274) and 27% nurses (n=74/274). A duplicate swap sample was obtained from each volunteer using moist cotton swabs and cultured onto mannitol salt agar and Columbia-5% blood agar and incubated at 35°C for 24-48 hours. Plates were checked for a typical staphylococci colony and overnight grown on blood agar at 35°C for 24 hours. The grown colonies were further tested by Gram stain and catalase test, and then a definite characterization was performed using a BD Phoenix automated identification and susceptibility testing system.

The level of prevalence and rates of proportion was calculated by descriptive analysis using Statistical package for sociality science (SPSS) statistics for Windows version 20 (SPSS-20, IBM Corp, Armonk, NY). Associations between categorical variables were analyzed using the Chi-square test to determine the variability between more than two groups, whereas the Z-test was used to determine the significant difference between two groups at p ≤ 0.05. A total of 32.4% (n=89/274) of HCWs were colonized with Staphylococcus species and 7.3% (n=20/274) were colonized with MRS strains. Although there were no appreciable differences between the two genders, the male group had a higher carriage rate of staphylococci and MRSA, at 40% and 10%, compared to the female group's rates of 30% and 6.5%, respectively. Also, no difference was identified between any of the analyzed age groups, but staphylococci carriage in the first group (18 to 25 years) was higher at a rate of 34%, and the MRS carriage in the second group (26 to 44 years) was higher at a rate of 7%. Furthermore, no differences in the carriage rates of staphylococci and MRS were found between the two study groups based on the profession and type of clinic, but doctors were found to have high staphylococci and MRS carriage at 33% and 8%, respectively. Healthcare workers who worked in both the private and public sectors had high staphylococci and MRS carriage at 38% and 8%, respectively, with the HCWs group of private clinics having the highest rate of MRS at 10%. In contrast, participants who had not recently experienced infections or who had not received antibiotic treatment had higher carriage rates of staphylococci and MRS, with respective carriage rates of 33% and 8% for both groups. However, only the carriage rate of MRS was significantly different between the studied groups of these two variables.

A total of 89 Staphylococcus species and subspecies were collected, represented by 22 S. aureus isolates and 67 CoNS subspecies isolates distributed respectively as follows: S. epidermidis (n=46), S. capitis (n=8), S. haemolyticus (n=6), S. saprophyticus (n=3), S. warneri (n=2) and S. lugdunesis (n=1). Of these, 22.4% twenty of the 89 isolates (20/89) had the typical MRS phenotype, represented by S. aureus (n = 9), S. epidermidis (n = 4), S. haemolyticus (n= 4), and S. saprophyticus (n = 3) (Table 1). In the current study, 32.4% and 22.4% of the studied HCWs were colonized with Staphylococcus and MRSA, mostly of the CoNS group. Such rates exceeded the global prevalence estimates reported by various studies [5]. The cryptogenic organizing pneumonia (CoPS) group was only represented by S. aureus, accounting for 28.5% of the collected CoPS and a HCW colonization rate of 6.7%. On the other hand, 45.8% of the collected CoNS were MRS (i.e., MRCoNS), representing an HCW colonization rate of 12.3%. Furthermore, the MRSA group showed similar MDR profiling, whereas the MRCoNS showed variability at species and antibiogram levels. This is probably attributed to the large number of species that constitute the group of CoNS within Staphylococcus, which plays an important role as a reservoir of species and genetic elements posing a potential risk of transferring genetic elements between different staphylococci species [6]. In the current study, six MDR CoNS expressing a high level of mupirocin resistance were identified, represented by 4 S. epidermidis, a MLSB S. epidermidis and a MRS S. heamolyticus. These were identified using an automated microbiological system, which is a highly accurate tool to identify various healthcare-associated pathogens including the critically resistant Gram-negative rods [7-9]. The emergence of high-level mupirocin resistance is widely attributed to the repeated and/or long-term exposure of CoNS colonizing nasal mucosa to topical and indiscriminate use of mupirocin but also indicates a potential expansion of the reservoir of MDR and transferrable molecular determinants encoding mupirocin resistance such as mupA and mupB gene [10].

Conclusion    

In conclusion, this is the first study that provides important information and data of the prevalence and distribution of Staphylococcus species and the associated MDR phenotypes circulating in HCWs in dental clinics in Libya. Healthcare workers were significantly colonized with different MDR species of Staphylococcus, posing serious concern to other personnel and the general population.

Competing interests     

The authors declare no competing interests.

Authors' contributions     

All the authors contributed equally to this work and agreed to the final manuscript.All the authors have read and agreed to the final mansucript.

Tables     

Table 1: antimicrobial susceptibility profiling of MRS strains (n=20)

References