Antibiotic resistance and ndvB gene expression among biofilm producing Pseudomonas aeruoginosa isolates

N.A. Mohammed, I.M. Abd Alla

 

Abstract

A novel antibiotic resistant mechanism among biofilms is glucan-mediated sequestration in which ndvB gene encodes a glucosyltransferase involved in the formation of this glucans. We studied the biofilm formation and antibiotic susceptibility pattern of P. aeruginosa isolated from clinical samples, and measured the expression of ndvB gene among biofilm forming isolates and their planktonic counterparts. The study was conducted on 92 P. aeruginosa isolates. Biofilm was measured using tissue culture plate method. Antibiotic susceptibility of biofilm positive isolates and planktonic counterparts for ciprofloxacin, tobramycin and gentamycin was tested using tube microdilution method. Expression of ndvB gene was measured using Syper green real time PCR. We found that 44 isolates (47.8%) of P. aeruginosa were biofilm positive. The biofilm formation was high among urine, endotracheal tube aspirate and burn isolates compared to isolates of wound specimens, with statistically nonsignificant differences. None of biofilm forming isolates was susceptible to the 3 antibiotics compared to the presence of susceptible isolates among the planktonic counterpart (18/40.9% for ciprofloxacin, 12/27.3% for tobramycin and 13/29.5% for gentamycin). Expression of ndvB gene was significantly high in biofilm isolates than their corresponding counterpart, with significant correlations with minimal biofilm inhibitory concentration (MBIC) values of cibrofloxacin (r=+ 0.65, p< 0.05 ), tobramycin (r= + 0.54 p< 0.05 ) and gentamycin (r=+ 0.77, p< 0.001 ).From this study we concluded that biofilm formation is an important character of P. aeruginosa that is a main cause of antibiotic resistance especially in isolates from catheterized urine , wound and endotracheal tube aspirate. NdvB gene expression is a mechanism of resistance to antibiotics in P. aeruginosa biofilms.

Keywords: P. aeruginosa, biofilm, antibiotic resistance and ndvB gene

Download full journal in PDF below

Antibiotic resistance and ndvB gene expression among biofilm producing Pseudomonas aeruoginosa isolates

Molecular detection of salmonella species from selected vegetables sold in a north-central Nigerian setting

D.S. Adeniyi, T.M. Akindigh, F.N. Aniweta, H.J. Zumbes, A.J. Anejo-okopi

 

Abstract

It is vital to study and understand the genetic basis to the virulence of different Salmonella strains in other to fully grasp the facts behind the unique capabilities of these pathogenic agents to causing diseases in both humans and animals. In this study, the conventional microbiological culture methods were used to isolate pure Salmonella strains from 120 vegetable samples of five different types; which were all obtained at seven different popular markets in the Jos Metropolis of North Central Nigeria. 25 (20.8%) pure isolates were obtained from 120 samples after initial culture and sub-cultures; with 24 (20%) of the pure isolates testing positive as being pathogenic after biochemical analysis. From the 25 pure isolates, the same 24 which tested positive for biochemical tests were also successfully amplified by PCR technique with the SalmonellainvA virulence gene. The result shows that 96% of the pure isolates were positive for the Salmonella invA gene. The PCR product which was very specific is a 250bp fragment of DNA which was visualized in 1.5% agarose gel. This finding shows that virulent Salmonella strains pose a major health hazard and public health concern to the affected population. Our study shows that there is a high prevalence rate of virulent Salmonella strains in North-Central Nigeria. It is thus concluded that although both the conventional culture and biochemical methods of isolating Salmonella species are most useful for obtaining pure isolates and identifying pathogenic strains, however, the PCR technique remains the most specific and sensitive; especially when the rapid identification and detection of virulent strains of Salmonella species are of utmost importance.

Keywords: Virulence, invA gene, PCR, North Central Nigeria

Download full journal in PDF below

Molecular detection of salmonella species from selected vegetables sold in a north-central Nigerian setting

Prevalence of methicillin-resistant Staphylococcus aureus and extended spectrum β–lactamase producers among bacteria isolated from infected wounds in a tertiary hospital in Ibadan City

O.S. Alabi, A.O. Obisesan, A.A. Ola

 

Abstract

Wound colonization by microorganisms is most frequently polymicrobial and incidences of high level resistance among bacterial isolates from wounds have been reported. Methicillin-resistant Staphylococcus aureus (MRSA) and extendedspectrum beta-lactamase (ESBL) producing Gram-negative bacteria both constitute serious challenge to physician in their choice of antibiotic treatment of infections caused by these bacteria. This study determined the antibiotic susceptibility profiles and prevalence of MRSA and ESBL producers among wound bacterial isolates from a tertiary hospital in Ibadan City.

Forty (40) clinical bacterial isolates from five wound sources were collected from the Microbiology unit of the University College Hospital (UCH), Ibadan and were authenticated with standard bacteriological techniques. Antibiotic susceptibility test was done by disc-diffusion method using 19 antibiotics belonging to 12 classes. MRSA strains were detected by their resistance to cefoxitin and/or oxacillin antibiotics. Presumptive ESBL production was by double-disc synergy test using 30 μg cefotaxime and ceftazidime around 20/10 μg amoxicillin-clavulanic acid discs. ESBL confirmation was by minimum inhibitory concentration (MIC) using agar-dilution method.

The authenticated isolates include Proteus spp (47.5%), Staphylococcus aureus (27.5%), Pseudomonas aeruginosa (12.5%), Klebsiella spp (7.5%), Acinetobacter baumanii (2.5%) and E. coli (2.5%). Distribution of the isolates collected according to wound sources includes: acute soft tissue wounds (35%), leg ulcer (32.5%), surgical wounds (17.5%), burn wounds (12.5%) and diabetic foot ulcer (2.5%). Distributions according to patients’ gender are: male (65%), female (35%), and according to age-groups are: 0 – 19 years (22.5%), 20 – 39 years (35%), 40 – 59 years (32.5%) and ≥ 60 years (10%). All (100%) the isolates were multidrug resistant (MDR) being resistant to ≥ 3 classes of antibiotics. Percentages of isolates resistance to each of the antibiotic include: piperacillin, piperacillin tozobactam and amoxicillin-clavulanic acid were 100%, ceftazidime, cefuroxime, cefixime, aztreonam, sulphamethoxazole-trimethoprim, erythromycin, chloramphenicol and doxycyclin were > 70%, cefoxitin (62.5%), Nitrofurantion (52.5%), ciprofloxacin (45%), ofloxacin (35%), perfloxacin (37.5%), gentamicin (32.5%) and imipenem (2.5%). Of the 11 Staphylococcus aureus collected, 54.5% were detected to be MRSA strains while ESBL production was detected in 55.2% of the Gram negative isolates.

This study revealed 100% MDR phenotype constituting high level of MRSA strains (54.5%) and ESBL producers (55.2%) among Gram-positive and Gram-negative bacterial wound isolates respectively. Hence, this calls for caution in the use of extended spectrum antibiotics in treating patients with infected wounds.

Download full journal in PDF below

Prevalence of methicillin-resistant Staphylococcus aureus and extended spectrum β–lactamase producers among bacteria isolated from infected wounds in a tertiary hospital in Ibadan City