Pseudomonas aeruginosa biofilms in hospital water systems and the effect of sub-inhibitory concentration of chlorine

Comparative analysis of virulence factors & biotypes of Gardnerella vaginalis isolated from the genital tract of women with & without bacterial vaginosis

Background & objectives

: Bacterial vaginosis (BV) involves the presence of a thick vaginal multispecies biofilm, where Gardnerella vaginalis is the predominant species. The reason for an increase in the number of G. vaginalis which are usually present as normal flora of the female genital tract in cases of BV, is not known. Hence, the objective of the present study was to compare the biotypes and virulence factors of G. vaginalis isolated from the genital tract of women with and without BV.

Methods

: High vaginal swabs collected from 811 women of reproductive age were cultured. G. vaginalis isolates were biotyped and tested for adherence to vaginal epithelial cells, biofilm formation, agglutination of human red blood cells (RBCs), protease production, phospholipase production and surface hydrophobicity.

Results

: Of the isolates from women with BV, 83.3 per cent (60/72) showed good adherence, 78.4 per cent (58/74) produced biofilm, 82.9 per cent (63/76) produced phospholipase, 67.1 per cent (51/76) produced protease, 77.3 per cent (58/75) were positive for surface hydrophobicity and 61.6 per cent (45/73) were positive for haemagglutination of human RBC. In case of G. vaginalis from non-BV women, 25 per cent (15/60) isolates showed good adherence, 18.4 per cent (9/49) biofilm production, 35 per cent (21/60) phospholipase, 36.6 per cent (22/60) protease, 41.7 per cent (25/60) surface hydrophobicity and 10.1 per cent (6/59) agglutination of human RBCs. Maximum number of isolates belonged to biotypes 6, 2 and 3. Biotype 3 was more associated with non-BV rather than BV; biotype 6, 2 and 1 were more associated with cases of BV. Maximum virulence factors were expressed by biotypes 6, 2 and 1.

Interpretation & conclusions

: Virulence factors were more expressed by G. vaginalis isolates obtained from women with BV rather than from non-BV. Biotypes 6, 2 and 1 were more associated with cases of BV and expressed maximum virulence factors.

Diphtheroids-Important Nosocomial Pathogens

INTRODUCTION

Diphtheroids are defined as aerobic, non-sporulating, pleomorphic Gram-positive bacilli which are more uniformly stained than Corynebacterium diphtheriae, lack the metachromatic granules and are arranged in a palisade manner. They are usually commensals of the skin and mucous membranes. They differ from C.diphtheriae in biochemical rea-ctions as well as in toxin production. Since, they are usually found as commensals on the skin, they are often considered as mere contaminants when isolated from clinical samples. However, there are increasing reports of these organisms being associated with various infections. Hence, we felt the need to study the common species associated with infections and know the properties of these organisms which are otherwise considered as mere laboratory contaminants.

AIM

To identify the various species of diphtheroids isolated as pure growth from clinical specimens whose Gram's smear revealed numerous inflammatory cells with Gram positive bacilli and had clinical evidence.

MATERIALS AND METHODS

A total of 100 isolates of Gram-positive bacilli from 16,242 clinical samples received in the Microbiology Department of Kasturba Medical College were considered for this study from Dec 2013-Dec 2014. Gram-positive bacilli which were seen in the smear along with pus cells, isolated as pure growth and reported as "Corynebacterium spp having clinical significance" were taken for this study while those which were reported as 'Probable skin contaminants' were excluded from this study. Species identification of Gram-positive bacilli was done by biochemical reactions. Antibiotic susceptibility test was done by Kirby-Bauer disk diffusion method. Biofilm production was done by the microtitre plate method of O'Toole and Kolter and statistical analysis was done by using proportion test and Chi-square test.

RESULTS

Various species of diphtheroids were isolated from different clinical specimens. C. pseudotuberculosis, C. renale, C. ulcerans, C. striatum, C. minutissimum, Corynebacterium haemolyticum isolated from catheter tips, sputum, tracheostomy secretions and wound infections were highly resistant to many antibiotics while isolates from blood namely C. pseudotuberculosis, C. minutissimum, C. ulcerans and C. renale were nearly sensitive to most of them. It was also interesting to note that there was an increased rate of biofilm production in these isolates.

CONCLUSION

Corynebacterium pseudotuberculosis, Coryne- bacterium ulcerans, Corynebacterium renale, Corynebacterium bovis, Corynebacterium striatum, Corynebacterium minutissimum, Corynebacterium pseudodiphtheriticum and Corynebacterium haemolyticum may survive in the form of biofilms in hospitals and cause multidrug resistant infections. Hence, we need to judiciously identify these organisms, find their antimicrobial susceptibility, treat them and thus prevent infections in hospitals.

Epidemiology and Ecology of Opportunistic Premise Plumbing Pathogens: Legionella pneumophila, Mycobacterium avium, and Pseudomonas aeruginosa

BACKGROUND

Legionella pneumophila, Mycobacterium avium, and Pseudomonas aeruginosa are opportunistic premise plumbing pathogens (OPPPs) that persist and grow in household plumbing, habitats they share with humans. Infections caused by these OPPPs involve individuals with preexisting risk factors and frequently require hospitalization.

OBJECTIVES

The objectives of this report are to alert professionals of the impact of OPPPs, the fact that 30% of the population may be exposed to OPPPs, and the need to develop means to reduce OPPP exposure. We herein present a review of the epidemiology and ecology of these three bacterial OPPPs, specifically to identify common and unique features.

METHODS

A Water Research Foundation-sponsored workshop gathered experts from across the United States to review the characteristics of OPPPs, identify problems, and develop a list of research priorities to address critical knowledge gaps with respect to increasing OPPP-associated disease.

DISCUSSION

OPPPs share the common characteristics of disinfectant resistance and growth in biofilms in water distribution systems or premise plumbing. Thus, they share a number of habitats with humans (e.g., showers) that can lead to exposure and infection. The frequency of OPPP-infected individuals is rising and will likely continue to rise as the number of at-risk individuals is increasing. Improved reporting of OPPP disease and increased understanding of the genetic, physiologic, and structural characteristics governing the persistence and growth of OPPPs in drinking water distribution systems and premise plumbing is needed.

CONCLUSIONS

Because broadly effective community-level engineering interventions for the control of OPPPs have yet to be identified, and because the number of at-risk individuals will continue to rise, it is likely that OPPP-related infections will continue to increase. However, it is possible that individuals can take measures (e.g., raise hot water heater temperatures and filter water) to reduce home exposures.

Evaluation of an MPN test for the rapid enumeration of Pseudomonas aeruginosa in hospital waters

In this study, the performance of a new most probable number (MPN) test (Pseudalert(®)/Quanti-Tray(®)) for the enumeration of Pseudomonas aeruginosa from hospital waters was compared with both international and national membrane filtration-based culture methods for P. aeruginosa: ISO 16266:2006 and UK The Microbiology of Drinking Water - Part 8 (MoDW Part 8), which both use Pseudomonas CN agar. The comparison based on the calculation of mean relative differences between the two methods was conducted according to ISO 17994:2014. Using both routine hospital water samples (80 from six laboratories) and artificially contaminated samples (192 from five laboratories), paired counts from each sample and the enumeration method were analysed. For routine samples, there were insufficient data for a conclusive assessment, but the data do indicate at least equivalent performance of Pseudalert(®)/Quanti-Tray(®). For the artificially contaminated samples, the data revealed higher counts of P. aeruginosa being recorded by Pseudalert(®)/Quanti-Tray(®). The Pseudalert(®)/Quanti-Tray(®) method does not require confirmation testing for atypical strains of P. aeruginosa, saving up to 6 days of additional analysis, and has the added advantage of providing confirmed counts within 24-28 hours incubation compared to 40-48 hours or longer for the ISO 16266 and MoDW Part 8 methods.

The bacterial biofilms in dialysis water systems and the effect of the sub inhibitory concentrations of chlorine on them

INTRODUCTION

The presence of bacteria in the form of biofilms poses a problem in the fluid pathways of haemodialysis plants and procedures which are aimed to detach and neutralize biofilms are necessary to improve the patient safety and the quality of the healthcare. The present study was therefore aimed at isolating the organisms which colonized dialysis water systems as biofilms, as well as to study the effect of the sub inhibitory concentrations of chlorine on the biofilms which were produced by these isolates.

METHODS

Swabs were used to collect the biofilms which were produced on the internal surface of the dialysis tubing from the dialysis units. This study was conducted at the Department of Microbiology, Kasturba Medical College (KMC), Mangalore, India. The cultures were performed on MacConkey's agar and blood agar. The organisms which were isolated were identified and antibiotic sensitivity tests were performed. The biofilm production was done by the microtitre plate method of O'Toole and Kolter. The biofilm production was also studied in the presence of sub inhibitory concentrations of chlorine.

RESULTS

Acinetobacter spp and Pseudomonas aeruginosa were the two predominant organisms which colonized the dialysis water systems as biofilms. The sub inhibitory concentrations of chlorine did not bring about any decrease in the biofilm production by the isolates. On the contrary, there was an increase in the biofilm production.

CONCLUSION

Our study highlighted the importance of using appropriate methods to improve the quality of the water in dialysis units. This in turn, may help in reducing the biofilm formation in the water systems of dialysis units and thus, contribute to the prevention of hospital acquired infections in the patients who need haemodialysis.