Genetic Polymorphism of agr Locus and Antibiotic Resistance of Staphylococcus aureus at two hospitals in Pakistan

Prevalence and epidemiological characteristics of methicillin-resistant Staphylococcus aureus isolated from cattle in Bangalore India as a part of the One Health approach

In India, limited studies are available on the epidemiological aspects of methicillin-resistant Staphylococcus aureus (MRSA) infections in both animal and human settings. Herein, we investigated the prevalence, antimicrobial resistance profile and molecular characteristics of MRSA isolates recovered from cattle using the One Health approach. Out of 66 mecA-positive staphylococci, species-specific multiplex PCR detected 24 % (n=16) of isolates as MRSA. Maximum antibiotic resistance was seen against cloxacillin (94 %, n=15) and least for enrofloxacin and cephalothin (each 13 %, n=2). Overall, 13 % (n=2) of MRSA isolates were multidrug-resistant. Molecular characterization by SCCmec typing identified 88 % (n=14) of MRSA isolates as type V. Twelve isolates (75 %) belonged to novel spa-type t17242, of which 67 % (n=8) belonged to agr type I. MLST analysis revealed ST 1687 (50 %, n=8) as the most predominant sequence type. Circulation of different MRSA clones among the cattle populace offers a risk of transmission to humans through direct contact, food chain or environmental contamination. Thus, continuous monitoring of MRSA strains is imperative for early diagnosis and for establishing effective treatment strategies to restrain the disease burden caused by MRSA infections.

Relationship between Biofilm Formation and Antibiotic Resistance and Adherence Genes in Staphylococcus aureus Strains Isolated from Raw Cow Milk in Shahrekord, Iran

The production of biofilms by S. aureus contributes significantly to treatment failures. The present study aims to establish the relationship between biofilm formation and antibiotic resistance and adhesion genes in Staphylococcus aureus strains isolated from raw cow milk in Shahrekord, Iran. A total of 90 samples of raw cow's milk were collected. Presumptive S. aureus strains were obtained using Baird-Parker plates after enrichment in tryptone soy broth, and final colonies were selected from brain heart infusion. Additional tests such as coagulase were done, and the identification was confirmed by the detection of the aroA gene. Biofilm producing strains were screened using a spectrophotometry method applied to microplates. Crystal violet staining was used to quantify the formation of biofilm. An antibiotic susceptibility test was performed using the Kirby-Bauer disc diffusion method. PCR was used to detect several biofilm and antibiotics resistance related genes. The chi-square test and Fisher's exact test were used to establish a statistically significant relationship between biofilm reaction and antibiotic resistance (p value <0.05). Results show a moderate (38.88%) recovery rate of S. aureus in milk and 65.71% of the isolates were strong biofilm producers. Antibiotic susceptibility tests show an alarming rate of resistance to beta-lactam antibiotics, especially penicillin (100%), ampicillin (91.42%), and oxacillin (71.42%). This finding correlates with antibiotic resistance gene detection, in which the gene blaZ was most found (71.42%), followed by mecA and Aac-D (42.85%). Detection of biofilm-related genes shows that all the genes targeted were found among S. aureus isolates. Statistical tests show a significant correlation between biofilm production and antibiotic resistance in S. aureus. This study revealed that there is a significant correlation between biofilm production and antibiotic resistance in S. aureus isolated from raw milk. These results highlight the need for regular surveillance of the occurrence of S. aureus strains in milk and milk products in Iran.

Antibiotic susceptibility of human-associated Staphylococcus aureus and its relation to agr typing, virulence genes, and biofilm formation

BACKGROUND AND OBJECTIVE

Carriage of virulence factors confers some evolutionary benefit to bacteria, which favors the resistant strains. We aimed to analyze whether antibiotic susceptibility of Staphylococcus aureus strains is affected by agr typing, biofilm formation ability, and virulence profiles.

METHODS

A total of 123 S. aureus clinical isolates were subjected to antimicrobial susceptibility testing by disk diffusion method, biofilm formation by microtiter plate method, as well as polymerase chain reaction screening to identify virulence genes and the accessory gene regulator (agr) types I-IV. A P value < 0.05 was considered significant.

RESULTS

The most prevalent virulence gene was staphyloxanthin crtN, followed by hemolysin genes, capsular cap8H, toxic shock toxin tst, and enterotoxin sea, respectively. Resistant isolates were more commonly found in the agr-negative group than in the agr-positive group. Isolates of agr type III were more virulent than agr I isolates. Strong biofilm producers showed more antibiotic susceptibility and carried more virulence genes than non-strong biofilm producers. Associations were found between the presence of virulence genes and susceptibility to antibiotics. Carriage of the virulence genes and agr was higher in the inpatients; while, resistance and strong biofilms were more prevalent in the outpatients.

CONCLUSION

These findings indicated the presence of several virulence factors, biofilm production capacity, agr types and resistance to antibiotics in clinical S. aureus isolates. Considering the importance of S. aureus for human medicine, an understanding of virulence and resistance relationships would help to reduce the impact of S. aureus infections.

Assessment of inducible clindamycin resistance and Hyper Variable Region (HVR) of mecA gene in clinical staphylococci

Objective:

To study the prevalence of inducible clindamycin along with vancomycin and methicillin resistance and assessment of hyper variable region (HVR) of mecA gene among different clinical isolates of Staphylococcus spp.

Methods:

A total of 176 clinical isolates of Staphylococci were collected from Pakistan Institute of Medical Sciences (PIMS), Islamabad during 2014-2015. The sample sources were pus, blood, urine, sputum, tracheal secretions and tissue fluids. Bacterial identification was done by colony morphology and biochemical tests. Kirby-Bauer disc-diffusion method was carried out to assess the susceptibility against different antibiotics. Minimal inhibitory concentrations (MICs) were done for vancomycin resistance. Double Disk Diffusion test (D-test) was used to detect the clindamycin inducible resistance. PCR was performed to detect erm(C), mecA and HVR genes.

Results:

Clindamycin inducible resistance among Staphylococcal isolates was found to be 7%, whereas in S. aureus it was 4%, and in coagulase negative Staphylococci (CoNS) it was 11%. The highest resistance was observed against fosfomycin, fusidic acid and cefoxitin. Vancomycin resistance was observed in 23 isolates (13%) of Staphylococci. erm(C), mecA and HVR genes were found in 18%, 50% and 42% respectively.

Conclusions:

D-test must be performed routinely to avoid clindamycin failure. A high level of resistance against vancomycin in Staphylococcal isolates is a concern for public health.

Identification of Hemolysine Genes and their Association with Antimicrobial Resistance Pattern among Clinical Isolates of Staphylococcus aureus in West of Iran

Background

Staphylococcus aureus is expressing a broad range of different hemolysins enhancing its ability to establish and maintain infection in humans. The aim of this study was to identify the types of hemolysins in different clinical isolates of S. aureus and their association with antibiotic resistance patterns.

Materials and Methods

In this cross-sectional and descriptive study, clinical isolates of S. aureus were collected from Hamedan's hospitals during an 11-month period from June 2016 to January 2017 and identified by using biochemical tests. To determine the antibiotic resistance pattern, disk diffusion method and minimum inhibitory concentration (MIC) were conducted. Genomic DNA was extracted using extraction kit. The polymerase chain reaction was done with specific primers for identification of hla, hlb, hld, and hld genes.

Results

Among a total of 389 clinical samples, 138 isolates (35.45%) of S. aureus were identified, which 87 isolates (63.04%) were cefoxitin MIC of >4 μg/ml and resistant to methicillin. The highest frequency of antibiotic resistance was observed against erythromycin in 108 isolates (78.26%) and penicillin in 133 isolates (96.37%) and the lowest resistance was against gatifloxacin in 50 isolates (36.23%) and Cefazolin in 11 isolates (97.7%). Furthermore, the hla, hlb, hld, and hlg genes were detected among 11 (7.97%), 7 (5.07%), 16 (11.59%), and 4 (2.89%) isolates, respectively. There was a significant relationship between the presence of alpha and delta hemolysin-encoding genes and the antibiotic resistance pattern of isolates (P < 0.05).

Conclusion

The results exhibited that the association between the presence of the hemolysin genes and the antibiotic resistance pattern can be considered as a serious issue.

Role of Intracellular Adhesion icaAD and agr genes in Biofilm Formation in Clinical S. aureus Isolates and Assessment of Two Phenotypic Methods

Objective:

To determine the role of icaAD and agr genes in biofilm formation and evaluate the consistency of two phenotypic methods for biofilm measurement.

Methods:

A total of 81 clinical S. aureus strains were included and analyzed for biofilm formation by two methods. The microtitration plate method was optimized using computational fluid dynamics and compared with the Congo red assay. The genes for icaAD and agr were detected using PCR.

Results:

Of 81 isolates, biofilm production was detected in 43% isolates using Congo red method while microtiter plate assay showed biofilm production in 92% isolates. Both methods showed correlation in 30% isolates. PCR detection showed icaAD gene in 42 (52%) isolates. Out of 81 S. aureus isolates 65 strains (80%) contained agr while 16 (20%) strains were non-typeable.

Conclusions:

In conclusion, biofilm production was observed for both agr positive and agr negative isolates. Furthermore, the presence of icaAD genes was not associated with all biofilm producing strains as some strains negative for icaAD genes displayed biofilm production.

Isolation, Characterization, and Antibacterial Activity of Bacteriophages Against Methicillin-Resistant Staphylococcus aureus in Pakistan

Background

In recent years, antibiotic resistance has been indicated as a paramount threat to public health. The use of bacteriophages appears to be a safer alternative for the control of bacterial infections.

Objectives

The present study aims to explore sewage water for the presence of indigenous bacteriophages, and to investigate their antibacterial potential against Methicillin-resistant Staphylococcus aureus (MRSA).

Methods

Bacterial isolates were first collected and identified from pus samples taken from the surgical and burn units using standard microbiological procedures. A cefoxitin disk screen test was then used and interpreted according to the clinical laboratory standards institute (CLSI) guidelines for the detection of MRSA. The sewage samples were processed and the phages enriched using S. aureus as a host organism. Turbid and clear plaques of different sizes were isolated using an overlay method, purified, and then enumerated by means of a dilution method.

Results

The phages exhibited good lytic activity against MRSA when tested in-vitro, and the highest activity was attained within three to six hours of phage infection. The isolated phage pq/48 was also found efficient in decreasing the bacterial count during an in-vivo trial in rabbits. A protein analysis using SDS-PAGE revealed 10 proteins of between 20 kDa and 155 kDa in size.

Conclusions

The overall results indicated that bacteriophages isolated from sewage exhibited excellent lytic activity against MRSA strains. In conclusion, bacteriophages can be further characterized and appear to be a promising candidate for phage therapy against MRSA in the future.

High frequency of methicillin-resistant Staphylococcus aureus in Peshawar Region of Pakistan

Staphylococcus aureus is an increasing problem in clinical practice because of reduced susceptibility to available antibiotics. The objective of the study was to determine the frequency of Methicillin-resistant S. aureus (MRSA) in Peshawar, Pakistan. Clinical isolates of S. aureus were subjected to determination of antibiotic resistance, MICs and inducible clindamycin resistance (ICR). Out of total 280 S. aureus isolates, the frequency of MRSA was 36.1 % (n = 101). MRSA infection was found higher among the age group 50-59 years (60.71 %, OR 3.09), followed by 20-29 years (47.5 %, OR 1.74). Frequency of MRSA in female and male was 39.8 and 34 % respectively. MRSA was more frequent in blood specimens (48.7 %, OR 2.14). The frequency of community and hospital acquired MRSA was 42 and 34.8 % respectively. MRSA showed high resistance (100 %) to penicillin and cefoxitin followed by erythromycin (99 %). While MRSA exhibited 100 % susceptibility to vancomycin and linezolid. We have also found 7 vancomycin intermediate sensitive S. aureus (VISA) isolates. ICR was observed in 15.84 % (n = 16) of MRSA isolates. It is concluded that MRSA is potential threat to public health in Peshawar. Vancomycin and linezolid could be prescribed as a drug of choice in treating MRSA associated infections. In addition, ICR should be routinely checked to avoid clindamycin treatment failure.