Perspectives of Arsenic Exposure and Asymptomatic Microbial Infections in Nawalparasi District

Abstract

Exposure to arsenic through groundwater has raised significant health problem in Terai region of Nepal. Elucidating antibiotic susceptibility pattern of urinary bacteria in community setting and dermatophyte carriage in scalp has very significant public health implications which have seldom been observed in Nepal. Based on the field work in arsenic affected communities of Nawalparasi district, various perspectives of arsenic exposure and status of asymptomatic bacteriuria and dermatophyte carriage were investigated.

Households of highly arsenic affected communities in the program areas of Filter for Families (FFF) were targeted for examination of arsenical dermatological manifestations and urine, hair and scalp swab collection. Hair and urine were analyzed by hydride generation atomic absorption spectrophotometer (SOLAAR 969AA Spectrometer, Thermo Elemental, UK) for total arsenic content and similarly, urine and scalp swab were cultured for urinary bacteria and fungi.

Among 240 participants observed, gender difference in dermatological manifestation was significant, males having nearly three times higher risk than females (p=0.01,OR=2.82, CI= 1.23-6.41). Similarly, dermatological manifestation was higher in the older age group (p=0.01) and tubewell users of high arsenic level (p=0.053). 70% (21/30) of arsenicosis cases had mild dermatological manifestation. The most common dermatological manifestations were keratosis of sole in male (28.5%) and keratosis of palm plus keratosis of soles in females (33.3%). Exposure analysis showed that 67% (73/109) and 65.8% (77/117) of subjects had urinary and hair arsenic level above the normal level. Similarly, subjects having urinary and hair arsenic level above normal level but without arsenical dermatological manifestations were 68.8% (75/109) and 47% (55/117), respectively. Difference in urinary arsenic level was insignificant for both gender and comparison of cases and non-cases (p>0.05). However, hair arsenic level differed significantly for both gender (p=0.01) and comparison of cases and non-cases (p=0.03). There was significant positive correlation of both urine and hair arsenic levels to tubewell arsenic level (r=0.27, 0.37, p<0.01) and negative correlation with the age of the subjects (r=-0.18, p=0.06). Binomial logistic regression revealed tubewell arsenic level, age and gender had the strongest association with arsenicosis (p<0.05).

Of 118 urine samples cultured, 37.2% (44/118) showed positive growth for uropathogens, females had higher growth rate (42.2%) than males (30.7%). The highest growth rate (47%) was in age group 31-45 years. E. coli was the most common isolate (19.6%) and multi-drug resistance (MDR) rate was 30.4%. Norfloxacin was the most effective antibiotic for Gram negative urinary isolates (with susceptibility of 96%; n=25) and ceftriazone for Gram positive isolates (with susceptibility of 71%; n=21). Resistance to amoxycillin was higher for both isolates (80%, 90.5%). Pseudomonas aeruginosa had the highest tolerance to As (V) (mean=725.71 ppm) and Klebsiella pneumoniae to As (III) (mean=25 ppm). Difference in mean tolerance of MDR and non-MDR isolates to As (III) and As (V) was not statistically significant (p>0.05).Urinary arsenic level shows significant positive correlation to tolerance of urinary bacteria to As (V) and As (III) (r=0.34, 0.4; p<0.05).

Of total 118 scalp swab cultured for fungi, 56.7% (67/118) showed positive growth. The fungal isolates comprised 8 (12%) dermatophytes and 59 (88%) non-dermatophytes. The dermatophyte carriage rate was 6.7% (8/118). Male had higher carriage rate (7.8%) than female (5.9%). The highest carriage rate (11.1%) was in age group 15-30 years. Trychophyton tonsurans, T. schonleinii and Epidermatophyton floccosum were common isolates, 25% (2/8) each. Aspergillus spp. was the most common non-dermatophytes isolate 28 (47.4%) There was no statistically significant difference in fungal growth in two seasons- summer and winter (p>0.05).

Exposure to arsenic and subsequent burden of the disease is still prevailing in highly arsenic contaminated communities of Nawalparasi district. Tube well arsenic level, age and gender have the strongest association with the disease. Multidrug resistance in uropathogens raises a challenge even in the community setting, and such drug resistance is not correlated to urinary arsenic level. Tolerance of uropathogens to As (V) and As (III) was correlated to urinary arsenic level. Carriage of dermatophytes in scalp of adolescent and older age group is a significant consideration and anthrophilic dermatophytes are more common isolates in scalp.

Key words: Arsenic; Asymptomatic bacteriuria; Dermatophyte carriage; Nawalparasi; MDR; As (V); As (III)