Evidence of Resistance of Heavy Metals from Bacteria Isolated from Natural Waters of a Mining Area in Mexico

This study focuses on identifying relationships between the content of heavy metals in water and the resistance patterns of different bacteria. Samples from watercourses in one of the most important mining areas in Mexico were collected. Seventy-one bacteria were isolated, and their resistance to Cr, Zn, Cu, Ag, Hg, and Co was studied. The Minimum Inhibitory Concentration range was determined, and a Multiple Metal Resistant index was calculated. After that, 11 isolated bacteria were chosen to estimate kinetic parameters. The obtained results show differences in the behavior of the studied bacteria concerning the presence of heavy metals in the media: (1) without effect, (2) inhibited growth; and (3) considerable inhibited growth. Finally, a Performance Index was proposed to select adequate bacteria for heavy metals removal; five bacteria were selected. Among them, Pseudomonas koreensis was identified as a good candidate for a future biosorption system since these bacteria can stimulate growth in the presence of all the metals tested.

Penicillin-Resistant Systemic Pneumococcal Infections in Children: A Retrospective Case-Control Study

Objective. To determine whether there are any risk factors that differentiate children with systemic infections due to Streptococcus pneumoniae relatively or fully resistant (minimum inhibitory concentration >0.1 µg/mL) to penicillin from those children with infections due to S pneumoniae susceptible to penicillin. Design. Retrospective case-control study. Setting. A large children's hospital. Participants. Forty-three children with systemic penicillin-resistant S pneumoniae infections identified at Texas Children's Hospital over the 51-month period from January 1989 through March 1993. Each case had one or two controls matched only for age and date of S. pneumoniae infection. Sixty-six controls were selected from a group of 341 children with susceptible isolates. Outcome measures. Variables compared included gender, race, diagnosis, underlying conditions, past hospitalization, geographic area of residence, antibiotic use in past month, amoxicillin-clavulanic acid use in past month, and outcome. Results. Thirty-seven patients (86%) had relatively resistant isolates (minimum inhibitory concentration range 0.125 to 1.0 µg/mL) and six patients (15%) had fully resistant isolates (minimum inhibitory concentration range 2.0 to 8.0 µg/mL). Thirty-three percent of the cases vs 36% of the controls had underlying conditions. Seventy-one percent of the cases vs 39% of the controls had received antibiotics in the previous month. Compared with their matched controls, the patients with penicillin-resistant systemic pneumococcal infections were more likely (P = .02) to have received a course of antibiotics within the month prior to their infection. Conclusion. The only identified associated risk factor in children who developed a systemic penicillin-resistant pneumococcal infection appears to have been the use of antibiotics within the month prior to their infection.