Antimicrobial susceptibility patterns and characterization of clinical isolates of Staphylococcus aureus in KwaZulu-Natal province, South Africa

Characterization of enterotoxin, antibiotic resistance genes, and antimicrobial susceptibility profiling of Staphylococcus aureus isolated from table eggs: Implications for food safety and public health

Background

Staphylococcus aureus is a significant pathogen in both clinical and food safety contexts, capable of contaminating table eggs, which are a common dietary staple worldwide.

Aim

This study aimed to assess the prevalence, molecular characteristics, and antibiotic resistance profiles of S. aureus isolated from table eggs. The focus was on identifying methicillin-resistant S. aureus (MRSA) strains that produce enterotoxin (seb), resistance to β-lactam antibiotics (blaTEM), tetracycline (tetA), and vancomycin-resistant S. aureus.

Methods

A total of 200 egg samples were collected from various retail sources in Mymensingh City Corporation, Bangladesh. Swab samples (n = 100) were collected from eggshells, and another 100 samples were collected from the inner membrane, egg white, and yolk. Samples were enriched in trypticase soy broth and cultured on mannitol salt agar. Staphylococcus aureus was isolated through conventional culture techniques, confirmed by polymerase chain reaction targeting the nuc, and further screened for the mecA, seb, blaTEM, tetA, vanA, and vanC genes. Antibiotic susceptibility testing was conducted using the disc diffusion method against 13 antibiotics. Bivariate analysis is used to assess the strong and significant correlations between virulence genes and the pairs of any of two antibiotic-resistant S. aureus.

Results

Staphylococcus spp. and S. aureus were detected in 53% and 21% of eggshell samples, respectively, and 41% and 13% of egg content samples. Among 34 coagulase-positive isolates, 12 (57.14%) from eggshells and 4 (30.78%) from egg contents were positive for the nuc gene. Resistance was observed in eggshell isolates for mecA (33.33%), blaTEM (85.71%), tetA (33.33%), vanA (19.04%), vanC (33.33%), and seb (20.50%), whereas egg content isolates showed resistance to blaTEM (46.15%) and vanC (7.80%). All coagulase-positive isolates exhibited significant resistance to β-lactam antibiotics, cephalosporins, and glycopeptides, especially vancomycin. Notably, 19 (90.47%) and 12 (92.30%) eggshell and egg content isolates, respectively, were multidrug-resistant, with multiple antibiotic resistance indices ranging from 0.23 to 0.76.

Conclusion

The study revealed a high prevalence of multidrug-resistant S. aureus in table eggs, indicating a significant public health risk. The presence of MRSA and strains with enterotoxins and resistance genes underscores the need for enhanced monitoring, stricter biosecurity measures, and robust control strategies for egg production and distribution to ensure food safety.

Exploring phenotypic and genotypic diversity among methicillin-resistant, vancomycin-resistant, and sensitive Staphylococcus aureus

BACKGROUND

Methicillin-Resistant Staphylococcus aureus (MRSA) is a global concern owing to the increasing prevalence of multidrug-resistant (MDR) strains. Vancomycin has been the primary treatment for MRSA; however, Vancomycin-resistant strains are being increasingly reported worldwide. Therefore, comparative studies are essential to support antimicrobial stewardship and improving clinical management. Ultimately, the findings from this study are expected to inform treatment strategies and guide public health interventions effectively.

MATERIAL AND METHODS

This study investigated the prevalence, antimicrobial resistance, and virulence characteristics of Vancomycin-sensitive S. aureus (VSSA) and Vancomycin-resistant S. aureus (VRSA) within MRSA strains. By employing a combination of phenotypic methods, such as antimicrobial susceptibility testing, and genotypic techniques, including molecular typing and identification of virulence genes, we obtained comprehensive insights into VRSA and VSSA profiles.

RESULTS

Of 250 clinical samples, 62 (24.8%) were S. aureus and 27 (43.5%) were identified as MRSA. All MRSA isolates exhibited MDR patterns. Most MRSA strains were VSSA (20/27, 74.1%), while 7 (25.9%) were VRSA. The VRSA isolates showed more antimicrobial resistance than VSSA isolates; however, the VRSA isolates had less virulence than VSSA isolates. Linezolid was the most effective treatment, with a 3.7% resistance rate. A higher percentage of biofilm-producing MRSA (96.3%) was confirmed by both phenotypic and genotypic methods. All isolates, except one VRSA, showed multi-virulence patterns (harbored more than 3 virulence genes). High diversity and low clonality (D-value = 0.99) were found in both VSSA and VRSA. Based on our correlation findings, the emergence of vancomycin resistance could modify the association between antimicrobial resistance and virulence, potentially affecting the pathogenic profile of these strains. The study also revealed complex interactions among host factors (including age and gender), sample origin, antimicrobial resistance, biofilm production, and virulence genes.

CONCLUSION

This study highlights the alarming spread of MRSA and VRSA, which show significant resistance and virulence.

Prevalence of Extended-Spectrum Beta-Lactamase Producer Gram-Negative Rods and Associated Factors Among Patients With Wound Infection at University of Gondar Comprehensive Specialized Hospital, Northwest Ethiopia

Background: Multidrug-resistant (MDR) bacteria have significantly affected the management and treatment of wound infections globally. Data on the prevalence of MDR bacterial profiles that cause wound infections in Ethiopia are scarce. Therefore, this study aimed to determine MDR as well as extended-spectrum beta-lactamase production profiles of Gram-negative rods that are difficult to treat with conventional antibiotics and that cause wound infections. Objective: The aim of the study was to determine the prevalence of extended-spectrum beta-lactamase producer Gram-negative rods and associated factors among patients with wound infection at University of Gondar Comprehensive Specialized Hospital, northwest Ethiopia. Materials and Methods: This hospital-based cross-sectional study was conducted at University of Gondar Comprehensive Specialized Hospital between May and July 2022. Convenience sampling was used to recruit 228 participants. Swabs from different wound types were inoculated onto the MacConkey agar and blood agar plates and incubated overnight at 37°C for 24 h. Biochemical tests were performed on isolated colonies for the identification of bacterial species based on their biochemical reaction. Antimicrobial susceptibility tests were performed using the disk diffusion technique as per the standard Kirby-Bauer method by using Muller-Hinton agar, and the zone of inhibition was interpreted as resistant, intermediate, and sensitive as per the recommendation of Clinical Laboratory Standard Institute. Isolates were tested against ceftriaxone, cefotaxime, and ceftazidime for extended-spectrum beta-lactamase screening using the Kirby-Bauer disk diffusion method, and combined disk tests were applied for phenotypic confirmatory test of extended-spectrum beta-lactamase producing isolates. Result: Of 228 study participants, 162 (71.1%) were culture-positive. Among culture-positive patients, 165 Gram-negative bacteria were recovered. The most common Gram-negative isolates were Pseudomonas aeruginosa (47; 28.5%), followed by Escherichia coli (43; 26.1%) and Klebsiella pneumoniae (24; 14.5%). The susceptibility rates of the isolate for imipenem and tobramycin were 97.0% and 73.2%, respectively, and the overall multidrug resistance rate was 80.5%. Extended-spectrum beta-lactamase producer bacteria were also isolated. Besides, all (100%) of extended-spectrum beta-lactamase producer bacteria were MDR. Living in rural areas (AOR 5.8; 95% CI [2.01-16.7]), hospital admission (AOR 3.95; 95% CI [1.13-13.83]), antibiotic use (AOR 2.83; 95% CI [1.03-7.72]), and comorbidity (AOR 0.25; 95% CI [0.07-0.59]) were significantly associated with wound infection. Conclusions and Recommendations: There was a high prevalence of Gram-negative bacterial isolates in this study. Pseudomonas aeruginosa (28.5%) was the predominant isolate. In addition, high rates of multidrug resistance were observed. The high level of multidrug resistance in this study implies that definitive therapy should be based on culture and susceptibility analysis to promote the rational use of antibiotics and to reduce the emergence of bacterial resistance to antimicrobials.

Chronicity of high and low level mupirocin resistance in Staphylococcus aureus from 30 Indian hospitals

Mupirocin is one of the most effective topically used antibiotic for the treatment of dermatitis, nasal carriage, decolonization of methicillin susceptible Staphylococcus aureus and eradication of methicillin resistant Staphylococcus aureus. Extensive use of this antibiotic has resulted in mupirocin resistance in Staphylococcus aureus which is a matter of concern. This study was conducted to evaluate the high and low level of mupirocin resistance in Staphylococcus aureus collected from various Indian hospitals. A total of 600 samples, of which 436 were pus specimens and 164 wound site swabs were collected from 30 Indian hospitals. Disc diffusion and agar dilution methods were used to test mupirocin susceptibility in methicillin resistant Staphylococcus aureus. Out of 600 Staphylococcus aureus isolates, 176 isolates (29.33%) were found to be methicillin resistant Staphylococcus aureus (MRSA). Out of 176 non-duplicate MRSA strains, 138 isolates were found to be mupirocin sensitive, 21 isolates had high level resistance whereas 17 isolates had low level resistance to mupirocin, which contributed 78.41%, 11.93% and 9.66% respectively. Multidrug resistant susceptibility was tested for all the MRSA with Cefuroxime, Cotrimoxazole and Vancomycin antibiotics. All the high and low level resistant strain were subjected to genome screening for mupA ileS gene respectively. mupA gene was found positive in all the high level resistant strain and out of 17 low level resistant strain, 16 strain were found point mutation in V588F of ileS gene. Overall, high rate of mupirocin resistance was found in the studied samples which might be a result of indiscriminate use of mupirocin in the population of studied region. This data emphasizes the urgent need for formulation of a well-defined and regulated guidelines for mupirocin use. Moreover, continuous surveillance is needed for the use of mupirocin and routine test should be performed to detect MRSA in patients and health care personnel to prevent MRSA infections.

Antibiotic susceptibility pattern of canine coagulase positive and coagulase negative Staphylococcus spp. in a hot and dry region of India

The emergence of anti microbial resistance among Staphylococcus spp. isolated from clinical cases of canines should be continuously monitored hence the present study was formulated to ascertain the antibiotypes and methicillin resistance in coagulase positive and coagulase negative staphylococci of canine skin and associated mucous membrane affections from a hot and dry region of India. A total of 165 clinical samples were collected and Staphylococcus aureus was identified by conventional bacteriological methods and PCR. Antibiotic susceptibility test was done against commercially available antibiotic impregnated discs as per Clinical and Laboratory Standards Institute (CLSI) method. Methicillin resistance was determined by plate methods and then via PCR of mecA gene. These 165 samples yielded, 88 (53.33%) isolates of genus Staphylococcus and 46 Staphylococcus aureus and 51/88 (57.95%) isolates were coagulase positive staphylococci. Total 55 (62.5%) isolates showed susceptibility to Ceftriaxone/Sulbactum, 37 (42.05%) to Ciprofloxacin, 26 (29.55 %) to Oxacillin, 24 (27.27 %) to Penicillin, and 10 (11.36 %) to Gentamicin. Total 21 methicillin resistant Staphylococcus aureus (MRSA) and 12 methicillin resistant coagulase negative staphylococci (MRCoNS) were found on phenotypic basis whereas the mecA gene was detected in 6 /21 MRSA and 2 /12 MRCoNS isolates. Staphylococcus spp. showed increased level of resistance against commonly used antibiotics. The higher prevalence of methicillin resistance found with phenotypic methods than to mecA PCR indicates towards additional mechanisms responsible for emergence of MRS, especially in CoNS.

DNA microarray analysis of Staphylococcus aureus from Nigeria and South Africa

Staphylococcus aureus is an important human pathogen with an arsenal of virulence factors and a propensity to acquire antibiotic resistance genes. The understanding of the global epidemiology of S. aureus through the use of various typing methods is important in the detection and tracking of novel and epidemic clones in countries and regions. However, detailed information on antibiotic resistance and virulence genes of S. aureus, and its population structure is still limited in Africa. In this study, S. aureus isolates collected in South Africa (n = 38) and Nigeria (n = 2) from 2001-2004 were characterized by spa typing and DNA microarray. The combination of these two methods classified the isolates into seven spa types and three clonal complexes (CCs) i.e. t064-CC8 (n = 17), t037-CC8 (n = 8), t1257-CC8 (n = 6), t045-CC5 (n = 5), t951-CC8 (n = 1), t2723-CC88 (n = 1), t6238-CC8 (n = 1), and untypeable-CC8 (n = 1). A high percentage agreement (>95%) and kappa coefficient (>0.60) was largely observed with antibiotic susceptibility testing and DNA microarray, indicating substantial agreement. Some antibiotic and virulence gene markers were associated with specific clones. The detection of the collagen-binding adhesion (cna) gene was unique for t037-CC8-MRSA while the enterotoxin gene cluster (egc) and staphylococcal complement inhibitor (scn) gene were identified with t045-CC5-MRSA. Moreover, the combination of genes encoding enterotoxins (entA, entB, entK, entQ) was noted with most of the CC8 isolates. The t045-CC5-MRSA clone was positive for the mercury resistance (mer) operon. DNA microarray provides information on antibiotic resistance and virulence gene determinants and can be a useful tool to identify gene markers for specific S. aureus clones in Africa.

Distribution and Antibiotic Resistance Patterns of Pathogenic Bacteria in Patients With Chronic Cutaneous Wounds in China

Background: To determine the distribution and antimicrobial susceptibility pattern of pathogenic bacteria in patients with chronic cutaneous wounds on a national scale. Methods: A retrospective study was conducted using the data recorded between January 1, 2018 and January1, 2020 in 195 hospitals across China. After screening the data, 815 patients with chronic wounds were finally analyzed. The data collected included information about the patients' general condition and local cutaneous wound assessments, especially microbial culture and antibiotic susceptibility tests. The analyses were performed using SPSS Version 26. Results: The study included 815 patients (290 [35.6%] females; 63 [50-74] years). The most common causes of chronic cutaneous wounds were diabetes (183, 22.5%), infection (178, 21.8%), and pressure (140, 17.2%). Among these, 521(63.9%) samples tested yielded microbial growth, including 70 (13.4%) polymicrobial infection and 451 (86.6%) monomicrobial infection. The positive rate of microbial culture was highest in wound tissue of ulcers caused by infection (87.6%), followed by pressure (77.1%), diabetes (68.3%), and venous diseases (67.7%). Bates-Jensen wound assessment tool (BWAT) scores >25 and wounds that lasted for more than 3 months had a higher positive rate of microbial culture. BWAT scores >25 and wounds in the rump, perineum, and feet were more likely to exhibit polymicrobial infection. A total of 600 strains were isolated, of which 46.2% (277 strains) were Gram-positive bacteria, 51.3% (308 strains) were Gram-negative bacteria, and 2.5% (15 strains) were fungi. The most common bacterial isolates were Staphylococcus aureus (29.2%), Escherichia coli (11.5%), Pseudomonas aeruginosa (11.0%), Proteus mirabilis (8.0%), and Klebsiella pneumoniae (5.8%). The susceptibility tests showed that 116 cultured bacteria were Multidrug resistant (MDR) strains. The resistance rates of S. aureus were 92.0% (161/175) to penicillin, 58.3% (102/175) to erythromycin, and 50.9% (89/175) to clindamycin. Vancomycin was the most effective antibiotic (0% resistance rate) against all Gram-positive bacteria. Besides, the resistance rates of E. coli were 68.1% (47/69) to ampicillin, 68.1% (47/69) to ciprofloxacin, 60.9% (42/69) to levofloxacin. However, all the isolated Gram-negative bacteria showed low resistance rates to tigecycline (3.9%) and amikacin (3.6%). Conclusions: The distribution of bacteria isolated from chronic cutaneous wounds varies with the BWAT scores, causes, duration, and the location of wounds. Multidrug resistance is a serious health issue, and therefore antibiotics used in chronic wounds must be under strict regulation. Our findings may help clinicians in making informed decisions regarding antibiotic therapy.

Isolation, characterisation and antibiotic susceptibility of staphylococcal isolates with special reference to methicillin-resistant Staphylococcus aureus from the anterior nares of healthcare workers in A tertiary healthcare centre

Background: Staphylococcus aureus (S. aureus) and its resistant form methicillinresistant S. aureus (MRSA) is one of the most common nosocomial pathogens causing a wide range of infections in humans. The anterior nares are the main ecological niche for S. aureus. Nasal carriage of S. aureus acts as an important reservoir of infection among the colonised healthcare workers and they transmit the infection to the community. The aim of the present study was to estimate the nasal colonisation of S. aureus (with special reference to MRSA) in healthcare workers (doctors and nursing staff) and its antibiotic susceptibility pattern. Methods: A descriptive study was planned in the Department of Microbiology, JLN Medical College, Ajmer (Rajasthan, India) after due approval from the institutional ethics committee. A total of 170 healthcare workers of either sex aged between 18 to 60 years were screened for S. aureus. Identification was done using standard microbiological techniques, by studying their morphology, colony and biochemical characteristics. MRSA was detected by cefoxitin disc diffusion test, oxacillin disc diffusion test, minimum inhibitory concentration (MIC) of oxacillin by E-test and oxacillin screen agar test. The observations were described in proportions and Chisquared test was used to find independence. Statistical significance was considered at 5 %. Results: Among 170 samples, 159 (93.53 %) samples (50 doctors and 109 nursing staff) had staphylococci colonisation. Among these 159 isolates, 34 (21.38 %) were S. aureus. Further, 8 (5.03 %) S. aureus isolates were resistant to both cefoxitin and oxacillin and had oxacillin MIC values ≥ 4 µg/mL and were considered MRSA. All the MRSA were detected in the nursing staff (males: 5.50 %, females: 1.83 %). All S. aureus and MRSA isolates were found sensitive to linezolid, vancomycin and mupirocin (minimum inhibitory concentration ≤ 4 µg/mL). Conclusion: Screening and treatment of healthcare workers colonised with MRSA should be an important component of hospital infection control policy. These measures will prevent spread of infection to patients and the community and thereby reduce the morbidity, mortality and healthcare costs associated with nosocomial infections.

Resistance Profiles of Staphylococcus aureus and Immunological Status in Pregnant Women at Bafang, West Region of Cameroon: A Cross-Sectional Study

Background

Staphylococcus aureus, a facultative aero-anaerobic Gram-positive coccus typically considered normal flora in the human gastrointestinal tract, have increasingly become a major cause of healthcare-associated infections over the past decade. This study aimed to evaluate the changes in immune factors in pregnant women colonized by S. aureus in the town of Bafang, West Region of Cameroon.

Methods

A cross-sectional study was carried in antenatal care unit in various health center in Bafang. S. aureus were isolated in stools using specific bacterial culture media. Antimicrobial susceptibility test was carried out using disk diffusion method. Blood was used to measure CD3, CD4 and CD8 T-cell lymphocyte counts, white blood cell count, high sensitivity C-reactive protein (hs-CRP) and interleukin-6 measurement using flow cytometry, optical detection and the ELISA solid phase direct sandwich method, respectively.

Results

Out of the 169 patients studied, 76.30% patients were pregnant women and 23.70% were non-pregnant women. S. aureus were isolated in 70.41% participants that is, 78.15% in pregnant and 21.85% in non-pregnant women. The mean age was significantly higher in non-pregnant women (29.38 ± 7.685 years) compared to pregnant women (25.55 ± 5.521 years). CD4 T-cell (574.80 ± 165.94; 754.03 ± 162.28, p < 0.001), were significantly lower in pregnant than non-pregnant women respectively, contrary for CD8 T-cell (333.86 ± 233.04; 250.40 ± 227.75, p = 0.043). S. aureus were significantly more isolated in pregnant women with a CD4 T-cell count between 410 and 625 cells/µl (p < 0.001). S. aureus were more susceptible to imipenem (91.40%), (100%); ciprofloxacin (65.59%), (69.44%); amikacin (96.77%), (100%) and resistant to chloramphenicol (78.49%), doxycycline (64.52%) and cefotaxime (51.61%) in pregnant women. Staphylococcus aureus showed a significant increased multidrug resistant (MDR) and methicillin-resistant S. aureus (MRSA) phenotypes in pregnant compared to non-pregnant women (p < 0.05).

Conclusion

The present study revealed that, Staphylococcus aureus, including resistant phenotypes should be considered in pregnant women to improve their health care.

Molecular Characterization and Pathogenicity of Staphylococcus aureus Isolated from Benin-City, Nigeria

While numerous studies examine the epidemiology and molecular characterization of Staphylococcus aureus in most developed countries, the detailed molecular characterization and molecular epidemiology of S. aureus strains and clones in Africa is lacking. We determined the molecular epidemiology and virulence of 81 non-duplicate isolates of S. aureus from Benin-City, Nigeria, collected during January–July 2016, and compared with global strains. Forty-seven isolates (58.0%) were found to be methicillin-sensitive Staphylococcus aureus (MSSA), while 34 (42.0%) were methicillin-resistant Staphylococcus aureus (MRSA). ST152-MSSA (24.7%) and ST7-MRSA-V (19.8%) were the dominant groups identified, which were not genetically related to global predominant strains, but rather exhibited regional dominance. An interesting finding of the study was the presence of highly related strains in the region, which differed primarily in their methicillin resistance gene carriage, staphylococcal cassette chromosome mec (SCCmec), with 99.4–99.7% relatedness between the genomes of the strains within the MRSA–MSSA pairs. This suggests that the strains within a pair are experiencing gain or loss of SCCmec within local conditions, with evolution continuing to diversify the strains to a small degree. This study represents the most comprehensive genetic and virulence study of S. aureus in Nigeria.

Molecular epidemiology and mechanisms of antibiotic resistance in Enterococcus spp., Staphylococcus spp., and Streptococcus spp. in Africa: a systematic review from a One Health perspective

A systematic review of antibiotic-resistant Gram-positive bacteria in Africa from a One Health perspective is lacking. Here, we report result from a search for English-language articles on the resistance mechanisms and clonality of Gram-positive bacteria in Africa between 2007 and 2019 reported in PubMed, Web of Science, ScienceDirect, and African Journals OnLine; 172 studies from 22 different African countries were identified. Resistance genes, such as mecA, erm(B), erm(C), tet(M), tet(K), tet(L), vanB, vanA, vanC, and tet(O), were found to be common. Staphylococcus spp., Enterococcus spp., and Streptococcus spp. were the main species reported by the studies, with clones such as Staphylococcus aureus ST5 (n = 218 isolates), ST8 (n = 127 isolates), ST80 (n = 133 isolates), and ST88 (n = 117 isolates), and mobile genetic elements such as IS16 (n = 28 isolates), IS256 (n = 96), Tn916 (n = 107 isolates), and SCCmec (n = 4437 isolates) identified. SCCmec IV (n = 747 isolates) was predominant, followed by SCCmec III (n = 305 isolates), SCCmec II (n = 163 isolates), SCCmec V (n = 135 isolates), and SCCmec I (n = 79 isolates). Resistance to penicillin (n = 5926 isolates), tetracycline (n = 5300 isolates), erythromycin (n = 5151 isolates), rifampicin (n = 3823 isolates), gentamycin (n = 3494 isolates), sulfamethoxazole/trimethoprim (n = 3089 isolates), and ciprofloxacin (n = 2746 isolates) was common in most reports from 22 countries. Clonal dissemination of resistance across countries and between humans, animals, and the environment was observed. Resistance rates ranged from 1.4% to 100% for 15 of the studies; 10 were One Health-related studies. Strict infection control measures, antimicrobial stewardship, and periodic One Health epidemiological surveillance studies are needed to monitor and contain the threat of increasing antibiotic resistance in Africa.

The prevalence and molecular mechanisms of mupirocin resistance in Staphylococcus aureus isolates from a Hospital in Cape Town, South Africa

Background

Antimicrobial resistance is an increasingly serious problem in public health globally. Monitoring resistance levels within healthcare and community settings is critical to combat its ongoing increase. This study aimed to describe the rates and molecular mechanisms of mupirocin resistance in clinical Staphylococcus aureus isolates from Tygerberg Hospital, and to describe its association with strain types.

Methods

We retrospectively selected 212 S. aureus isolates which were identified from blood samples and pus swabs during the years 2009–2011 and 2015–2017. The isolates were identified using conventional microbiological methods and genotyping was done using spa typing. Cefoxitin (30 μg) disc diffusion and the two disc strategy (5 μg and 200 μg) were used to determine susceptibility to methicillin and mupirocin, respectively. Isolates with high-level resistance were screened for the plasmid mediated genes mupA and mupB by PCR, and sequencing of the ileS gene was done for all isolates exhibiting low-level resistance to describe the mutations associated with this phenotype. Chi-square test was used to assess the associations between mupirocin resistance and S. aureus genotypes.

Results

Of 212 S. aureus isolates, 12% (n = 25) were resistant to mupirocin, and 44% (n = 93) were methicillin resistant. Strain typing identified 73 spa types with spa t045 being the most predominant constituting 11% of the isolates. High-level mupirocin resistance was observed in 2% (n = 5), and low-level resistance in 9% (n = 20) of the isolates. The prevalence of high-level mupirocin resistance amongst MRSA and MSSA was 4 and 1% respectively, while the prevalence of low-level mupirocin resistance was significantly higher in MRSA (18%) compared to MSSA (3%), (p = 0.032). mupA was the only resistance determinant for high-level resistance, and the IleS mutation V588F was identified in 95% of the isolates which showed low-level resistance. A significant association was observed between spa type t032 and high-level mupirocin resistance, and types t037 and t012 and low-level resistance (p <  0.0001).

Conclusion

The study reported higher rates of low-level mupirocin resistance compared to high-level resistance, and in our setting, mupirocin resistance was driven by certain genotypes. Our study advocates for the continuous screening for mupirocin resistance in S. aureus in clinical settings to better guide treatment and prescribing practices.

Alternative Sigma Factor B in Bovine Mastitis-Causing Staphylococcus aureus: Characterization of Its Role in Biofilm Formation, Resistance to Hydrogen Peroxide Stress, Regulon Members

This study examines treatments of the bacterial pathogen Staphylococcus aureus, namely, in the context of its being a major cause of subclinical bovine mastitis. Such infections caused by S. aureus among dairy cows are difficult to detect and can easily become chronic, leading to reduced productivity and large losses for dairy manufacturers. In this study, the role of alternative sigma factor B (σ^B), which has been shown to be a global regulator for S. aureus infections, was explored in a mastitis-causing S. aureus strain, RF122. For comparison with the wild-type strain, a sigB null (ΔsigB) mutant was constructed and analyzed for its phenotypes and transcriptome. Our study found that σ^B is essential for biofilm formation as the ΔsigB mutant strain produced significantly less biofilm than did the wild-type strain at 48 h. σ^B is involved in response to H₂O₂ stress. However, σ^B plays a minor or no role in resistance to antiseptics (e.g., povidone-iodine and chlorhexidine), resistance to tested antibiotics, hemolysin activity, and invasion ability. RNA sequencing identified 225 σ^B-dependent genes, of which 171 are positively regulated and 54 are negatively regulated. The identified genes are involved in stress response, pathogenesis, and metabolic mechanisms. Quantitative TaqMan RT-PCR was performed to verify the RNA sequencing results; i.e., σ^B is a positive regulator for asp23, sarA, katA, yabJ, sodA, SAB2006c, and nrdD expressions. In the RF122 strain, σ^B plays a role in biofilm formation, general stress response (e.g., H₂O₂), and regulation of virulence factors and virulence-associated genes.

Mupirocin resistance in Staphylococcus aureus: A systematic review and meta-analysis

OBJECTIVES

Staphylococcus aureus is one of the most common pathogens causing nosocomial and community-acquired infections associated with high morbidity and mortality. Mupirocin has been increasingly used for treatment of methicillin-susceptible S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA) infections. The aim of this study was to determine the prevalence of mupirocin-resistant S. aureus (MuRSA), mupirocin-resistant MRSA (MuRMRSA), high-level MuRSA (HLMuRSA) and high-level MuRMRSA (HLMuRMRSA) worldwide.

METHODS

Online databases including Medline, Embase and Web of Science were searched (2000-2018) to identify studies addressing the prevalence of MuRSA, MuRMRSA, HLMuRSA and HLMuRMRSA. STATA v. software was used to interpret the data.

RESULTS

Of the 2243 records identified from the databases, 30 and 63 studies fulfilled the eligibility criteria for MuRSA and MuRMRSA, respectively. Finally, 27 and 60 studies were included separately for HLMuRSA and HLMuRMRSA, respectively. The analyses revealed pooled and averaged prevalences of MuRSA, MuRMRSA, HLMuRSA and HLMuRMRSA of 7.6% [95% confidence interval (CI) 6.2-9.0%], 13.8% (95% CI 12.0-15.6%), 8.5% (95% CI 6.3-10.7%) and 8.1% (95% CI 6.8-9.4%), respectively.

CONCLUSION

Overall, these results show a global increase in the prevalence of HLMuRSA and HLMuRMRSA among clinical S. aureus isolates over time. However, there was only a significant increase in the prevalence of MuRMRSA compared with the other categories, especially MuRSA. Since mupirocin remains the most effective antibiotic for MSSA and MRSA decolonisation both in patients and healthcare personnel, a reduction of its effectiveness presents a risk for invasive infection. Monitoring of mupirocin resistance development remains critical.

Field level interventions on subclinical mastitis and detection of Staphylococcus in crossbred dairy cows

Mastitis has emerged as one of the major managemental diseases of economic importance of high yielding dairy cows. A cross sectional study was carried out on 116 cross-bred dairy cows of small scale dairy farms; subclinical mastitis (SCM) was detected in 22 animals (cow-wise prevalence, 18.96%). Of the 88 individual quarter’s milk tested using California mastitis test (CMT) and somatic cell count (SCC) tests, 51 quarters showed SCM (quarterwise prevalence, 57.9%). Quarter-wise prevalence of SCM was 29.4, 31.4, 23.5 and 15.7% in right-fore (RF), right-hind (RH), left-fore (LF) and left-hind (LH) quarters, respectively. Fore-(52.9%) and right-(60.8%) quarters showed higher prevalence of SCM than hind-(47.1%) and left-(39.2%) quarters. All 4 quarters were found affected with SCM in 47% cows followed by 3-(23.5%), 1-(17.6%) and 2-(11.8%) quarters. Staphylococci were isolated and confirmed using 16S rRNA gene based genus-specific PCR in 39.2% of SCM affected quarters. Virulence associated nuc gene was detected in 75% of Staphylococcus isolates indicating their potential pathogenicity. Antibiogram showed multiple drug resistance (≥3 antimicrobial category) in 63.6% of Staphylococci. Multiple antimicrobial resistance (MAR) was recorded in 31.8% isolates. However, none of the isolate carried mecA gene. Interventions, viz. clean milk production practices, antimicrobial therapy and non-specific supportive treatments resulted in 77.7, 50 and 38.8% reductions in SCM compared to the untreated control (37.5%). This study accentuated higher prevalence of SCM among dairy cattle and predominance of Staphylococcus as the major mastitogen. Early detection and management of SCM among dairy cattle is recommended so as to prevent its progression to clinical illness and curtail potential economic loss to farmers.

Genomic analysis of methicillin-resistant Staphylococcus aureus isolated from poultry and occupational farm workers in Umgungundlovu District, South Africa

This study detected methicillin-resistant Staphylococcus aureus (MRSA) isolates circulating in poultry and farm workers at an intensive poultry production system in uMgungundlovu, South Africa and established the genetic relatedness and characteristics of the isolates using whole genome sequencing (WGS). A total of 145 S. aureus were isolated from poultry (120) and occupational workers (25) in the "farm to fork" continuum (farm, transport, slaughterhouse, and retail points). Twelve MRSA (12/145; 8.3%) isolates were found in the poultry food-chain. MRSA isolates were subjected to antibiotic susceptibility testing against a panel of 20 antibiotics using the broth dilution method and their whole genome was sequenced via the Illumina MiSeq. All the MRSA isolates were multi-drug resistant (MDR) and carried the mecA gene on the SCCmec mobile genetic element (MGE). The majority (11/12) of the MRSA isolates circulating between humans and animals in the continuum belonged to a human-associated clone, ST612-CC8-t1257-SCCmec_IVd (2B), previously reported in South Africa. Other MGEs present in the isolates included: plasmid replicons based on Rep 7 and 20, insertion sequences (IS1182), and prophages (phi2958PVL). Genomic analysis identified a distinct acquired antibiotic resistome in the clone, which accurately predicted the phenotypic antibiograms. Phylogenetic analysis clustered the isolates within the major cluster (I), suggesting the spread of the local dominant multidrug resistance MRSA clone ST612-CC8-t1257-SCCmec_IVd (2B) between humans and animals along the 'farm to fork' continuum. The findings of this study suggest the need to establish appropriate control measures to curb the spread of MDR-MRSA in the food chain.

Isolation and Molecular Identification of Virulence, Antimicrobial and Heavy Metal Resistance Genes in Livestock-Associated Methicillin-Resistant Staphylococcus aureus

Staphylococcus aureus is one of the most important pathogens of humans and animals. Livestock production contributes a significant proportion to the South African Gross Domestic Product. Consequently, the aim of this study was to determine for the first time the prevalence, virulence, antibiotic and heavy metal resistance in livestock-associated S. aureus isolated from South African livestock production systems. Microbial phenotypic methods were used to detect the presence of antibiotic and heavy metal resistance. Furthermore, molecular DNA based methods were used to genetically determine virulence as well as antibiotic and heavy metal resistance determinants. Polymerase chain reaction (PCR) confirmed 217 out of 403 (53.8%) isolates to be S. aureus. Kirby-Bauer disc diffusion method was conducted to evaluate antibiotic resistance and 90.8% of S. aureus isolates were found to be resistant to at least three antibiotics, and therefore, classified as multidrug resistant. Of the antibiotics tested, 98% of the isolates demonstrated resistance towards penicillin G. High resistance was shown against different heavy metals, with 90% (196/217), 88% (192/217), 86% (188/217) and 84% (183/217) of the isolates resistant to 1500 µg/mL concentration of Cadmium (Cd), Zinc (Zn), Lead (Pb) and Copper (Cu) respectively. A total of 10 antimicrobial resistance and virulence genetic determinants were screened for all livestock associated S. aureus isolates. Methicillin-resistant S. aureus (MRSA) isolates were identified, by the presence of mecC, in 27% of the isolates with a significant relationship (p < 0.001)) with the host animal. This is the first report of mecC positive LA-MRSA in South Africa and the African continent. The gene for tetracycline resistance (tetK) was the most frequently detected of the screened genes with an overall prevalence of 35% and the highest prevalence percentage was observed for goats (56.76%) followed by avian species (chicken, duck and wild birds) (42.5%). Virulence-associated genes were observed across all animal host species. The study reports the presence of luks/pv, a gene encoding the PVL toxin previously described to be a marker for community acquired-MRSA, suggesting the crossing of species between human and livestock. The high prevalence of S. aureus from the livestock indicates a major food security and healthcare threat. This threat is further compounded by the virulence of the pathogen, which causes numerous clinical manifestations. The phenomenon of co-selection is observed in this study as isolates exhibited resistance to both antibiotics and heavy metals. Further, all the screened antibiotic and heavy metal resistance genes did not correspond with the phenotypic resistance.

Methicillin-Resistant Staphylococcus aureus (MRSA): Prevalence and Antimicrobial Sensitivity Pattern among Patients-A Multicenter Study in Asmara, Eritrea

Background

Methicillin-resistant Staphylococcus aureus (MRSA) is a well-recognized public health problem throughout the world. The evolution of new genetically distinct community-acquired and livestock-acquired MRSA and extended resistance to other non-β-lactams including vancomycin has only amplified the crisis. This paper presents data on the prevalence of MRSA and resistance pattern to other antibiotics on the selected specimen from two referral hospitals in Asmara, Eritrea.

Method

A cross-sectional study was conducted among 130 participants recruited from two referral hospitals in Asmara, Eritrea. Isolation of S. aureus was based on culture and biochemical profiles. Standard antimicrobial disks representing multiple drug classes were subsequently set for oxacillin, gentamicin, erythromycin, and vancomycin. Data were analyzed using SPSS version 20 software.

Results

S. aureus isolation rate from the 130 samples was 82 (63.1%). Patients <18 years of age were more likely to be colonized by S. aureus compared to patients above 61 years. The proportion of MRSA among the isolates was 59 (72%), methicillin-intermediate S. aureus (MISA) was 7 (8.5%), and methicillin-sensitive S. aureus (MSSA) was 15 (19.5%). The isolates were mostly from the pus specimen in burn, diabetic, and surgical wound patients. Antimicrobial susceptibility test showed that 13 (15.9%) of the isolates were resistant to vancomycin, 9 (11.0%) to erythromycin, and 1 (1.2%) to gentamicin. Coresistance of MRSA isolates to some commonly used antibiotics was also noted: oxacillin/erythromycin 5 (6.1%) and oxacillin/vancomycin 9 (11%). A few isolates were resistant to oxacillin/vancomycin/erythromycin 2 (2.4%) and oxacillin/gentamicin and erythromycin 1 (1.2%).

Conclusion

This study reports a relatively high prevalence of MRSA. Isolates that are resistant to other tested antibiotics including vancomycin are also reported. The data have important implication for quality of patients care in the two settings: antibiotic selection and infection control practices, and the need for additional studies.

A review on mechanism of action, resistance, synergism, and clinical implications of mupirocin against Staphylococcus aureus

Mupirocin (MUP), bactroban, or pseudomonic acid is a natural crotonic acid derivative drug extracted from Pseudomonas fluorescens which is produced by modular polyketide synthases. This antibiotic has a unique chemical structure and mechanism of action. It is a mixture of A-D pseudomonic acids and inhibits protein synthesis through binding to bacterial isoleucyl-tRNA synthetase. MUP is often prescribed to prevent skin and soft tissue infections caused by S. aureus isolates and where the MRSA isolates are epidemic, MUP may be used as a choice drug for nasal decolonization. It is also used for prevention of recurring infections and control the outbreaks. The emergence of MUP resistance has been increasing particularly among methicillin-resistant Staphylococcus aureus (MRSA) isolates in many parts of the world and such resistance is often related with MUP widespread uses. Although both low-level and high-level MUP resistance were reported among MRSA isolates, the rate of resistance is different in various geographic areas. In this review, we will report the global prevalence of MUP resistance, discuss synergism and mechanism of action of MUP, and provide new insights into the clinical use of this antibiotic.

Antibiotic resistance profiles of coagulase-positive and coagulase-negative staphylococci from pit latrine fecal sludge in a peri-urban South African community

The aim of this study was to assess pit latrine samples from a peri-urban community in KwaZulu-Natal (South Africa) for the presence of multidrug-resistant (MDR) Staphylococcus spp. Standard procedures were used to isolate Staphylococcus spp. from pit latrine fecal sludge samples, with confirmation at genus level by polymerase chain reaction (PCR). Sixty-eight randomly selected pit latrine Staphylococcus spp. isolates were further characterized by using established disk diffusion procedures. An average Staphylococcus spp. count of 2.1 × 105 CFU per g fecal material was established using two randomly selected pit latrine samples. Of the 68-selected Staphylococcus spp. pit latrine isolates, 49% were identified as coagulase positive, 51% as coagulase negative and 65% (12 coagulase positive, 32 coagulase negative isolates) were categorized as MDR. The majority (66/68) of Staphylococcus spp. isolates displayed resistance to fusidic acid while only 5/68 isolates displayed resistance to chloramphenicol. The pit latrine samples analyzed in this study are a source of MDR Staphylococcus spp., highlighting the need for proper hygiene and sanitation regimes in rural communities using these facilities.

Mupirocin-resistant Staphylococcus aureus in Africa: a systematic review and meta-analysis

Background

Mupirocin is widely used for nasal decolonization of Staphylococcus aureus to prevent subsequent staphylococcal infection in patients and healthcare personnel. However, the prolonged and unrestricted use has led to the emergence of mupirocin-resistant (mupR) S. aureus. The aim of this systematic review was to investigate the prevalence, phenotypic and molecular characteristics, and geographic spread of mupR S. aureus in Africa.

Methods

We examined five electronic databases (EBSCOhost, Google Scholar, ISI Web of Science, MEDLINE, and Scopus) for relevant English articles on screening for mupR S. aureus from various samples in Africa. In addition, we performed random effects meta-analysis of proportions to determine the pooled prevalence of mupR S. aureus in Africa. The search was conducted until 3 August 2016.

Results

We identified 43 eligible studies of which 11 (26%) were obtained only through Google Scholar. Most of the eligible studies (28/43; 65%) were conducted in Nigeria (10/43; 23%), Egypt (7/43; 16%), South Africa (6/43; 14%) and Tunisia (5/43; 12%). Overall, screening for mupR S. aureus was described in only 12 of 54 (22%) African countries. The disk diffusion method was the widely used technique (67%; 29/43) for the detection of mupR S. aureus in Africa. The mupA-positive S. aureus isolates were identified in five studies conducted in Egypt (n = 2), South Africa (n = 2), and Nigeria (n = 1). Low-level resistance (LmupR) and high-level resistance (HmupR) were both reported in six human studies from South Africa (n = 3), Egypt (n = 2) and Libya (n = 1). Data on mupR-MRSA was available in 11 studies from five countries, including Egypt, Ghana, Libya, Nigeria and South Africa. The pooled prevalence (based on 11 human studies) of mupR S. aureus in Africa was 14% (95% CI =6.8 to 23.2%). The proportion of mupA-positive S. aureus in Africa ranged between 0.5 and 8%. Furthermore, the frequency of S. aureus isolates that exhibited LmupR, HmupR and mupR-MRSA in Africa were 4 and 47%, 0.5 and 38%, 5 and 50%, respectively.

Conclusions

The prevalence of mupR S. aureus in Africa (14%) is worrisome and there is a need for data on administration and use of mupirocin. The disk diffusion method which is widely utilized in Africa could be an important method for the screening and identification of mupR S. aureus. Moreover, we advocate for surveillance studies with appropriate guidelines for screening mupR S. aureus in Africa.

Characterisation of Staphylococcus aureus isolates from bloodstream infections, Democratic Republic of the Congo

Staphylococcus aureus is known worldwide as an invasive pathogen, but information on S. aureus from bloodstream infections in Central Africa remains scarce. A collection of S. aureus blood culture isolates recovered from hospitals in four provinces in the Democratic Republic of the Congo (2009-2013) was assessed. A total of 27/108 isolates were methicillin-resistant S. aureus (MRSA), of which >70% were co-resistant to aminoglycosides, tetracyclines, macrolides and lincosamides. For MRSA and methicillin-susceptible S. aureus (MSSA) isolates, resistance to chloramphenicol and trimethoprim-sulphamethoxazole (TMP-SMX) was <10%. However, 66.7% (72/108) of all isolates harboured the trimethoprim resistance gene dfrG. More than three-quarters (84/108, 77.8%) of isolates belonged to CC5, CC8, CC121 or CC152. Genetic diversity was higher among MSSA (31 spa types) compared to MRSA (four spa types). Most MRSA (23/27, 85.2%) belonged to CC8-spa t1476-SCCmec V and 17/23 (73.9%) MRSA ST8 were oxacillin susceptible but cefoxitin resistant. Among MRSA and MSSA combined, 49.1% (53/108) and 19.4% (21/108) contained the genes encoding for Panton-Valentine leucocidin (lukS-lukF PV, PVL) and toxic shock syndrome toxin-1 (tst, TSST-1), respectively. PVL was mainly detected among MSSA (51/53 isolates harbouring PVL were MSSA, 96.2%) and associated with CC121, CC152, CC1 and CC5. TSST-1 was associated with CC8-spa t1476-SCCmec V. The immune evasion cluster (IEC) genes scn, sak and chp were detected in 81.5% of isolates (88/108, equally represented among MSSA and MRSA). The present study confirms the occurrence of MRSA with high levels of multidrug co-resistance and PVL-positive MSSA among invasive S. aureus isolates in Central Africa.

[Antibiotic susceptibility of community-acquired strains ofstaphylococcus aureus in Nouakchott Region (Mauritania)]

INTRODUCTION

Staphilococcus aureus is a leading pathogen for humans causing a variety of infections such as skin, urinary tract and lung infections as well as sepsis. This study aims to evaluate the susceptibility of community-acquired strains of Staphylococcus aureus, isolated from various pathological products, compared with major antibiotics used in Nouakchott Region (Mauritania).

METHODS

We conducted a retrospective study of 281 strains of Staphylococcus aureus strains isolated from various pathological products from non-hospitalized patients in the National referral hospital laboratory and in two private laboratories in the city of Nouakchott between January 2014 and August 2015. Antibiotic sensitivity was determined by disk diffusion method using agar containing Mueller-Hinton medium according to CA-SFM's recommendations.

RESULTS

The resistance rate to penicillin G was high (96-100%). Community-acquired MRSA rate was between 25 and 26% in suppurations, 34.3% in urine cultures and 28% in sperm cultures. Macrolide -Lincosamyne-streptogramins (MLS) resistance, giving rise to the phenotype MLSb inducible, was found in 6% of urinary strains and 27% of strains isolated from suppurations. The activity of aminoglycosides was variable, amikacin was active against all strains. Cotrimoxazole activity was low (77% had resistance) and no vancomycin resistance was reported.

CONCLUSION

The activity of penicillin G against Staphylococcus aureusstrains isolated in Nouakchott region is almost zero and community-acquired MRSA rate is high, accounting for 34%. This could be explained by uncontrolled use of these molecules in our country.

Risk factors assessment for nasal colonization of Staphylococcus aureus and its methicillin resistant strains among pre-clinical medical students of Nepal

BACKGROUND

Staphylococcus aureus (S. aureus), a normal flora of nasal cavity, can cause minor to life threatening invasive diseases and nosocomial infections. Methicillin resistant strains of S. aureus are causing a great challenge for treatment options. Therefore, the purpose of this study was to assess the nasal carriage rate of S. aureus, its methicillin resistant strains and risk factors in medical students prior to clinical exposure.

METHODS

The bacterial growth of S. aureus from nasal swab culture was identified by using standard microbiological methods recommended by American Society for Microbiology. Modified Kirby-Bauer disk diffusion method was used for antibiotic susceptibility testing and methicillin resistance was confirmed using cefoxitin and oxacillin disks. D-zone test method was used to determine the inducible clindamycin resistance.

RESULTS

Among 200 participants, nasal carriage of S. aureus was detected from 30 (15%) subjects. Upper respiratory tract infections significantly (P < 0.05) contributed the carriage of S. aureus and their methicillin resistant strains. All of the isolates were reported to be susceptible to vancomycin and teicoplanin. S. aureus strains detected from 8 (4%) students were confirmed to be methicillin resistant.

CONCLUSIONS

The result of our study demands for strict policy to screen all the students for nasal carriage of S. aureus and its MRSA strains to minimize the transmission of this organism from community to hospital settings.

Characterisation of clinical Staphylococcus aureus isolates harbouring mecA or Panton-Valentine leukocidin genes from four tertiary care hospitals in Indonesia

OBJECTIVES

To determine the prevalence, antimicrobial susceptibility profiles and clonal distribution of either methicillin-resistant Staphylococcus aureus (MRSA) or Panton-Valentine leukocidin (PVL)-positive S. aureus obtained from clinical cultures in Indonesian hospitals.

METHODS

S. aureus isolates from clinical cultures of patients in four tertiary care hospitals in Denpasar, Malang, Padang and Semarang were included. We assessed the antimicrobial susceptibility profiles using the Vitek2(®) system, determined the presence of the mecA gene and genes encoding PVL using PCR and analysed the clonal relatedness with Raman spectroscopy. SCCmec typing was performed for all MRSA isolates. Multilocus sequence typing (MLST) was performed for a subset of isolates.

RESULTS

In total, 259 S. aureus strains were collected. Of these, 17/259 (6.6%) and 48/259 (18.5%) were MRSA and PVL-positive methicillin-susceptible S. aureus (MSSA), respectively. The prevalence of MRSA and PVL-positive MSSA ranged between 2.5-8.9% and 9.5-29.1%, respectively and depended on geographic origin. PVL-positive MRSA were not detected. Raman spectroscopy of the strains revealed multiple Raman types with two predominant clusters. We also showed possible transmission of a ST239-MRSA-SCCmec type III strain and a ST121 PVL-positive MSSA in one of the hospitals.

CONCLUSIONS

We showed that MRSA and PVL-positive MSSA are of clinical importance in Indonesian hospitals. A national surveillance system should be set-up to further monitor this. To reduce the prevalence of MRSA in Indonesian hospitals, a bundle of intervention measures is highly recommended.

Plasmid-mediated resistance and virulence mechanisms in the private health sector in KwaZulu-Natal, South Africa: An investigation of methicillin resistant Staphylococcus aureus (MRSA) clinical isolates collected during a three month period

OBJECTIVES

Due to the lack of information on the plasmid content of MRSA strains in South Africa (SA), this study investigated the resistance and virulence mechanisms of 27 clinical isolates from the private health care sector over a period of 3 months.

METHODS

Plasmids were extracted and the presence of MRSA confirmed by the presence of mecA. The isolates were subjected to antimicrobial susceptibility testing and molecular characterization of common resistance encoding genes and frequently encountered virulence factors by PCR using plasmid DNA as the template. The genetic relatedness between the isolates was determined by pulsed field gel electrophoresis (PFGE).

RESULTS

All isolates were plasmid positive, and displayed ampillicin, ciprofloxacin, gentamicin, rifampicin, tetracycline, erythromycin, and clindamycin resistance. They were all fully susceptible to daptomycin, linezolid, vancomycin, tigecycline and fusidic acid. Multidrug resistance (MDR) was found in 74.1% (20/27) of the MRSA isolates. The frequency of the resistance and virulence genes ranged from 100% to 0%. PFGE analysis revealed 10 pulsotypes, designated A-J, which showed correlation with resistance profile of the isolates in each group. Of note, 85.2% (23/27) of the isolates clustered into six major PFGE types giving an indication of similar circulating MRSA clones.

CONCLUSIONS

This study highlights the genetic diversity and resistance mechanisms in MRSA strains from the private health sector in SA hence the need for implementing effective infection control programs.

Genotyping of coa and aroA Genes of Methicillin-Resistant Staphylococcus aureus Strains Isolated From Nasal Samples in Western Iran

Background:

Methicillin-resistant Staphylococcus aureus (MRSA) is a bacterial pathogen frequently isolated in both hospital and community environments. Methicillin-resistant Staphylococcus aureus is considered a major nosocomial pathogen that causes severe morbidity and mortality.

Objectives:

The main objective of this study was to determine the genotypes of MRSA strains isolated from the nares of hospitalized and community patients in Kermanshah Hospital, western Iran, by PCR-restriction fragment length polymorphism (PCR-RFLP).

Materials and Methods:

Of 1387 patients, 1217 patients were screened for more than 48 hours after admission in hospital wards and 170 patients were screened in the hemodialysis unit of Kermanshah Hospital, which is the largest hospital in western Iran. S. aureus was identified by standard biochemical tests, including colonial morphology, production of coagulase, and DNase and the API20 Staph test. Methicillin-resistant Staphylococcus aureus was identified by the Oxacillin strip test.

Results:

In total, 258 S. aureus isolates were recovered from 1387 samples, of which 96 isolates were MRSA, 82 were hospital acquired, and 14 were community acquired. Digestion of the aro A gene revealed only one distinctive RFLP pattern in the 258 isolates.

Conclusions:

Methicillin-resistant Staphylococcus aureus is an increasingly common cause of nosocomial infections. Our results are in agreement with those of other studies reporting that a few specialized clones are responsible for most cases of MRSA nasal carriage. In this study, MRSA strains isolated from different wards of hospital were closely related when analyzed by coagulase gene typing. Identifying patients colonized with MRSA during hospitalization and rapidly typing them with these methods may facilitate detection of outbreaks and prevention of the spread of organisms in hospitals.

Inducible clindamycin resistance and nasal carriage rates of Staphylococcus aureus among healthcare workers and community members

BACKGROUND

Nasal carriage of Staphylococcus aureus is becoming an increasing problem among healthcare workers and community individuals.

OBJECTIVES

To determine the prevalence of methicillin-resistant S. aureus (MRSA) nasal colonization and inducible clindamycin resistance (ICR) of S. aureus among healthcare workers at Soba University Hospital and community members in Khartoum State, Sudan.

METHODS

Five hundred nasal swabs samples were collected during March 2009 to April 2010. Isolates were identified using conventional laboratory assays and MRSA determined by the disk diffusion method. The D-test was performed for detection of ICR isolates with Clinical Laboratory Standard Institute guidelines.

RESULTS

Of the 114 S. aureus isolated, 20.2% represented MRSA. The occurrence of MRSA was significantly higher among healthcare worker than community individuals [32.7% (18/55) vs. 6.9% (5/59)] (p=0.001). Overall the 114 S. aureus isolates tested for ICR by D-test, 29 (25.4%) yielded inducible resistance. Significantly higher (p=0.026) ICR was detected among MRSA (43.5%) than methicillin-susceptible S. aureus (MSSA) (20.9%).

CONCLUSION

MRSA nasal carriage among healthcare workers needs infection control practice in hospitals to prevent transmission of MRSA. The occurrence of ICR in S. aureus is of a great concern, D- test should be carried out routinely in our hospitals to avoid therapeutic failure.

Diversity and antimicrobial susceptibility profiling of staphylococci isolated from bovine mastitis cases and close human contacts

The objectives of this study were to examine the diversity of Staphylococcus spp. recovered from bovine intramammary infections and humans working in close contact with the animals and to evaluate the susceptibility of the staphylococcal isolates to different antimicrobials. A total of 3,387 milk samples and 79 human nasal swabs were collected from 13 sampling sites in the KwaZulu-Natal province of South Africa. In total, 146 Staph. aureus isolates and 102 coagulase-negative staphylococci (CNS) were recovered from clinical and subclinical milk samples. Staphylococcusaureus was isolated from 12 (15.2%) of the human nasal swabs and 95 representative CNS were recovered for further characterization. The CNS were identified using multiplex-PCR assays, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), and tuf gene sequencing. Seven Staphylococcus spp. were identified among the CNS of bovine origin, with Staph.chromogenes (78.4%) predominating. The predominant CNS species recovered from the human nasal swabs was Staph.epidermidis (80%) followed by Staph.chromogenes (6.3%). The antimicrobial susceptibility of all staphylococcal isolates was evaluated using disk diffusion and was supplemented by screening for specific antimicrobial resistance genes. Ninety-eight (67.1%) Staph.aureus isolates of bovine origin were pansusceptible; 39 (26.7%) isolates were resistant to a single class, and 7 (4.8%) isolates were resistant to 2 classes of antimicrobials. Two Staph. aureus (1.4%) isolates were multidrug-resistant. Resistance to penicillin was common, with 28.8% of the bovine and 75% of the human Staph. aureus isolates exhibiting resistance. A similar observation was made with the CNS, where 37.3% of the bovine and 89.5% of the human isolates were resistant to penicillin. Multidrug-resistance was common among the human CNS, with 39% of the isolates exhibiting resistance to 3 or more classes of antimicrobials. The antimicrobial susceptibility results suggest that resistance among staphylococci causing bovine intramammary infections in South Africa is uncommon and not a significant cause for concern. In contrast, antimicrobial resistance was frequently observed in staphylococcal isolates of human origin, highlighting a possible reservoir of resistance genes. Continued monitoring of staphylococcal isolates is warranted to monitor changes in the susceptibility of isolates to different classes of antimicrobials.

Molecular epidemiology of Methicillin-resistant Staphylococcus aureus in Africa: a systematic review

Methicillin-resistant Staphylococcus aureus (MRSA) infections are a serious global problem, with considerable impact on patients and substantial health care costs. This systematic review provides an overview on the clonal diversity of MRSA, as well as the prevalence of Panton-Valentine leukocidin (PVL)-positive MRSA in Africa. A search on the molecular characterization of MRSA in Africa was conducted by two authors using predefined terms. We screened for articles published in English and French through to October 2014 from five electronic databases. A total of 57 eligible studies were identified. Thirty-four reports from 15 countries provided adequate genotyping data. CC5 is the predominant clonal complex in the healthcare setting in Africa. The hospital-associated MRSA ST239/ST241-III [3A] was identified in nine African countries. This clone was also described with SCCmec type IV [2B] in Algeria and Nigeria, and type V [5C] in Niger. In Africa, the European ST80-IV [2B] clone was limited to Algeria, Egypt and Tunisia. The clonal types ST22-IV [2B], ST36-II [2A], and ST612-IV [2B] were only reported in South Africa. No clear distinctions were observed between MRSA responsible for hospital and community infections. The community clones ST8-IV [2B] and ST88-IV [2B] were reported both in the hospital and community settings in Angola, Cameroon, Gabon, Ghana, Madagascar, Nigeria, and São Tomé and Príncipe. The proportion of PVL-positive MRSA carriage and/or infections ranged from 0.3 to 100% in humans. A number of pandemic clones were identified in Africa. Moreover, some MRSA clones are limited to specific countries or regions. We strongly advocate for more surveillance studies on MRSA in Africa.

The Detection of Mupirocin Resistance and Nasal Carriage of Methicillin Resistant Staphylococcus aureus among Healthcare Workers at University Hospitals of Tehran, Iran

BACKGROUND

Nasal mupirocin is found to eradicate effectively methicillin-resistant Staphylococcus aureus (MRSA) from colonized patients, but there are concerns about resistant strains. The aim of this study was to detect the mupirocin resistance and nasal carriage of methicillin resistant S. aureus among healthcare workers (HCWS) at the university hospitals of Tehran.

METHODS

Totally 270 nasal swabs were collected and S. aureus were identified by confirmatory tests in 2013. Determination of oxacillin and mupirocin resistance was performed by disk diffusion method and the mupirocin MIC assessed using E-test. The ileS-2 (mupA) and mecA genes were detected in DNA extracts by multiplex PCR.

RESULTS

The prevalence of S. aureus nasal carriage among HCWs was 14.44%. E-test and disk diffusion methods showed 5 and 4 mupirocin resistant isolates, respectively. Statistically significant difference was observed between sex (P=0.035), hospitals (P=0.0001) and occupation (P=0.009) with nasal carriage of S. aureus. A significant difference was found between sex (P=0.041) and occupation (0.034) with regard to MRSA carriage. All MRSA isolates were susceptible to linezolid, fusidic acid and vancomycin.

CONCLUSION

Since the HCWs play an important role as a reservoir for resistant isolates in the hospital setting, regularly screening should be performed for identification of nasal carriers.

Staphylococcus aureus bacteraemia in Gauteng academic hospitals, South Africa

INTRODUCTION

Methicillin-resistant Staphylococcus aureus (MRSA) infections are responsible for longer hospital stays, increased hospital costs, and poorer outcomes compared to methicillin-sensitive S. aureus (MSSA) infections. We aimed to describe the epidemiology of S. aureus bacteraemia (SAB) and to determine factors associated with MRSA infection in South Africa.

METHODS

Cases of SAB were reported from September 2012 to September 2013 from three sentinel sites. A case was defined as the isolation of S. aureus from a blood culture during a 21-day period. Detailed clinical information was collected. Multivariable logistic regression was done to determine factors associated with MRSA infection and mortality.

RESULTS

There were 442 cases of SAB reported; antimicrobial susceptibility testing was performed on 240 isolates (54%). Thirty-six percent (86/240) of cases had an MRSA infection. A longer hospital stay before positive specimen collection (odds ratio (OR) 1.08, 95% confidence interval (CI) 1.02-1.13, p=0.004), hospitalization in the last year (OR 15.7, 95% CI 2.5-99.5, p=0.003), HIV infection (OR 4.9, 95% CI 1.05-22.90, p=0.044), and antibiotic use in the previous 2 months (OR 0.1, 95% CI 0.01-0.68, p=0.022) were independent predictors of MRSA. Older age, and in particular age 25-44 years (OR 22.2, 95% CI 2.7-185.5, p=0.004, compared to those aged<5 years), was the only independent predictor of mortality amongst cases with SAB. MRSA isolates were non-susceptible to more antimicrobial agents compared to MSSA isolates.

CONCLUSIONS

HIV infection was an independent risk factor for MRSA infection. The selection of appropriate empirical antimicrobial treatment is essential in patients with MRSA infections because of non-susceptibility to many other antimicrobial classes.

Structural characterization of a Gcn5-related N-acetyltransferase from Staphylococcus aureus

The Gcn5-related N-acetyltransferases (GNATs) are ubiquitously expressed in nature and perform a diverse range of cellular functions through the acetylation of small molecules and protein substrates. Using activated acetyl coenzyme A as a common acetyl donor, GNATs catalyse the transfer of an acetyl group to acceptor molecules including aminoglycoside antibiotics, glucosamine-6-phosphate, histones, serotonin and spermidine. There is often only very limited sequence conservation between members of the GNAT superfamily, in part, reflecting their capacity to bind a diverse array of substrates. In contrast, the secondary and tertiary structures are highly conserved, but then at the quaternary level there is further diversity, with GNATs shown to exist in monomeric, dimeric, or tetrameric states. Here we describe the X-ray crystallographic structure of a GNAT enzyme from Staphylococcus aureus with only low sequence identity to previously solved GNAT proteins. It contains many of the classical GNAT motifs, but lacks other hallmarks of the GNAT fold including the classic β-bulge splayed at the β-sheet interface. The protein is likely to be a dimer in solution based on analysis of the asymmetric unit within the crystal structure, homology with related GNAT family members, and size exclusion chromatography. The study provides the first high resolution structure of this enzyme, providing a strong platform for substrate and cofactor modelling, and structural/functional comparisons within this diverse enzyme superfamily.

Threat of drug resistant Staphylococcus aureus to health in Nepal

BACKGROUND

Staphylococcus aureus is the most commonly isolated organism from the different clinical samples in hospital. The emergence and dissemination of methicillin resistant Staphylococcus aureus (MRSA) and growing resistance to non-beta-lactam antibiotics is making treatment of infections due to this organism increasingly difficult.

METHODS

This study was conducted to determine the frequency of Staphylococcus aureus isolated from different clinical samples, rates of MRSA and full antibiotic susceptibility profiles. Clinical samples were cultured and Staphylococcus aureus was identified using standard microbiological methods recommended by the American Society for Microbiology (ASM). Methicillin resistance was confirmed using cefoxitin and oxacillin disks. Inducible clindamycin resistance was identified using D-zone test.

RESULTS

From the processed samples, 306 isolates of Staphylococcus aureus were recovered. All the isolates were susceptible to vancomycin and teicoplanin. Methicillin resistance was observed in 43.1% of isolates while inducible clindamycin resistance in 12.4% of the isolates.

CONCLUSIONS

The results of our study reveals that rates of resistance to commonly prescribed antibiotics in Staphylococcus aureus clinical isolates is high. In particular, rate of methicillin resistance is alarming, prompting concern on the rational use of antibiotics and vigilant laboratory-based surveillance of resistance rates in Nepal.

Purification, crystallization and preliminary X-ray diffraction analysis of the N-acetyltransferase SAV0826 from Staphylococcus aureus

Staphylococcus aureus is a prevalent microorganism that is capable of causing a wide range of infections and diseases. Several strains of this bacterial species have developed antibiotic resistance to methicillin and vancomycin, and higher death rates are still being reported each year owing to multidrug-resistant strains. Certain GCN5-related N-acetyltransferases (GNATs) exhibit a broad substrate range, including aminoglycosides, histones, other proteins and serotonin, and have been implicated in antibiotic drug resistance. Here, the expression, purification, crystallization and preliminary X-ray diffraction analysis of a GNAT from S. aureus (SaNAT) are reported. SaNAT was recombinantly expressed and crystallized by the hanging-drop vapour-diffusion method at 296 K, and the crystals diffracted to 1.7 Å resolution on the MX2 beamline at the Australian Synchrotron. The crystals belonged to space group P43212, with unit-cell parameters a = b = 84.86, c = 49.06 Å, α = β = γ = 90°. A single molecule is likely to be present in the asymmetric unit. A full structural and functional analysis is currently being undertaken to provide novel insights into the protein function, which in turn may provide a basis for drug design.

Incidence of constitutive and inducible clindamycin resistance among hospital-associated Staphylococcus aureus

Clindamycin is one of the important alternative antibiotics in the therapy of Staphylococcus aureus infections. Clinical failure of clindamycin therapy has been reported due to multiple mechanisms that confer resistance to macrolides, lincosamides and Streptogramin B (MLSB) antibiotics. In vitro routine tests for clindamycin susceptibility may fail to detect inducible clindamycin resistance due to erm genes, resulting in the treatment failure. Although data from the developed countries have shown to be enormity of the problem, data from the developing countries are lacking. The aim of the study was to distinguish different resistance phenotypes in erythromycin-resistant S. aureus by a simple double-disc diffusion test (D test). A total of 153 S. aureus isolates were subjected to routine antibiotic susceptibility testing, including cefoxitin disc (30 μg) and by oxacillin screen agar. Inducible clindamycin resistance was tested by 'D test' as per CLSI guidelines. Odds ratios (OR) and 95 % confidence intervals (95 % CI) were calculated. P values were calculated using SPSS (version 18). Among 153 S. aureus isolates, 42 (27.45 %) were resistant to methicillin, whereas 111 (72.54 %) were methicillin susceptible. Out of the 63 (41.17 %) erythromycin-resistant S. aureus isolates, 14 (9.15 %) showed inducible resistance [P = 0.0002, odds ratio (OR) 18.30; 95 % confidence interval (CI) 8.72-25.77), 20 (13.07 %)] showed constitutive resistance (P = 0.002, OR 14.38, 95 % CI 5.33-21.49), while the remaining 29 (18.95 %) showed inducible phenotype. Inducible and constitutive resistance was found to be higher in MSSA when compared with MRSA. Clinical laboratories should perform D test routinely to guide the clinicians about the inducible clindamycin resistance and to prevent misuse of antibiotics.

Could chloramphenicol be used against ESKAPE pathogens? A review of in vitro data in the literature from the 21st century

The widespread use of antibiotics has been associated with the emergence of antimicrobial resistance among bacteria. 'ESKAPE' (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acintobacter baumannii, Pseudomonas aeruginosa and Enterobacter spp.) pathogens play a major role in the rapidly changing scenario of antimicrobial resistance in the 21st century. Chloramphenicol is a broad spectrum antibiotic that was abandoned in developed countries due to its association with fatal aplastic anemia. However, it is still widely used in the developing world. In light of the emerging problem of multi-drug resistant pathogens, its role should be reassessed. Our paper reviews in vitro data on the activity of chloramphenicol against ESKAPE pathogens. Susceptibility patterns for Gram-positives were good, although less favorable for Gram-negatives. However, in combination with colistin, chloramphenicol was found to have synergistic activity. The risk-benefit related to chloramphenicol toxicity has not been analyzed. Therefore, extra precautions should be taken when prescribing this agent.

Epidemiology of Staphylococcus aureus bacteraemia at a tertiary children's hospital in Cape Town, South Africa

Background

Staphylococcus aureus is an important pathogen in paediatric patients with bloodstream infections. The epidemiology of S. aureus bacteraemia, however, has not been well documented in children in South Africa.

Methods

A retrospective study was conducted at a children’s hospital in Cape Town, South Africa, to investigate the epidemiology of S. aureus bacteraemia from 2007-2011. The incidence, clinical presentation, risk factors, management and outcomes of methicillin sensitive S. aureus (MSSA) and methicillin resistant S. aureus (MRSA) bacteraemia were compared.

Results

Over the five year study period, 365 episodes of S. aureus bacteraemia were identified. The annual incidence was 3.28 cases per 1000 hospital admissions. MRSA was responsible for 26% of S. aureus bacteraemia and 72% of nosocomial infections. Only six possible cases of community-acquired MRSA infections were described. MSSA bacteraemia was more likely to present as pulmonary and bone or joint infections, while bacteraemia without a source was the most common presentation with MRSA.  Infants, children with malnutrition, and residents of long-term care facilities were at highest risk for MRSA bacteraemia. The overall case fatality rate for S. aureus bacteraemia was 8.8% over five years, with MRSA being the only significant risk factor for mortality.

Conclusion

The incidence of S. aureus bacteraemia and MRSA bacteraemia in children has remained stable over the past five years. MRSA is a predominantly nosocomial pathogen in children with S. aureus bacteraemia in Cape Town, South Africa.