Aims: The purpose of this study was to compare the ef®cacy, in terms of bacterial bio®lm penetration and killing, of alkaline hypochlorite (pH 11) and chlorosulfamate (pH 5á5) formulations. Methods and Results: Two species bio®lms of Pseudomonas aeruginosa and Klebsiella pneumoniae were grown by¯owing a dilute medium over inclined stainless steel slides for 6 d. Microelectrode technology was used to measure concentration pro®les of active chlorine species within the bio®lms in response to treatment at a concentration of 1000 mg total chlorine l ±1 . Chlorosulfamate formulations penetrated bio®lms faster than did hypochlorite. The mean penetration time into 1 mm-thick bio®lms for chlorosulfamate (6 min) was only one-eighth as long as for the same concentration of hypochlorite (48 min). Chloride ion penetrated bio®lms rapidly (5 min) with an effective diffusion coef®cient in the bio®lm that was close to the value for chloride in water. Bio®lm bacteria were highly resistant to killing by both antimicrobial agents. Bio®lms challenged with 1000 mg l ±1 alkaline hypochlorite or chlorosulfamate for 1 h experienced 0á85 and 1á3 log reductions in viable cell numbers, respectively. Similar treatment reduced viable numbers of planktonic bacteria to non-detectable levels (log reduction greater than 6) within 60 s. Aged planktonic and resuspended laboratory bio®lm bacteria were just as susceptible to hypochlorite as fresh planktonic cells. Conclusions: Chlorosulfamate transport into bio®lm was not retarded whereas hypochlorite transport clearly was retarded. Superior penetration by chlorosulfamate was hypothesized to be due to its lower capacity for reaction with constituents of the bio®lm. Poor bio®lm killing despite direct measurement of effective physical penetration of the antimicrobial agent into the bio®lm demonstrates that bacteria in the bio®lm are protected by some mechanism other than simple physical shielding by the bio®lm matrix. Signi®cance and Impact of the Study: This study lends support to the theory that the penetration of antimicrobial agents into microbial bio®lms is controlled by the reactivity of the antimicrobial agent with bio®lm components. The ®nding that chlorine-based biocides can penetrate, but fail to kill, bacteria in bio®lms should motivate the search for other mechanisms of protection from killing by antimicrobial agents in bio®lms.

The penetration of hydrogen peroxide into biofilms formed by wild-type and catalase-deficient Pseudomonas aeruginosa strains was measured using microelectrodes. A flowing stream of hydrogen peroxide (50 mM, 1 h) was unable to penetrate or kill wild-type biofilms but did penetrate and partially kill biofilms formed by an isogenic strain in which the katA gene was knocked out. Catalase protects aggregated bacteria by preventing full penetration of hydrogen peroxide into the biofilm.

SARS-CoV-2 infection in children produces mild respiratory symptoms or no symptoms at all in most cases. Some pediatric patients develop a severe complication associated with high mortality, the multisystem inflammatory syndrome in children (MIS-C). In both scenarios, there are reports of neurological manifestations. This article aims to review the cases of pediatric patients with severe neurological issues and a coexisting positive SARS-CoV-2 test. A literature search was performed between March 2020 and May 2021. The results included the data from 41 studies, with 159 children with severe neurological manifestations, within an age range from 24 h to 17 years. The neurological disorders included 38 cases with stroke, 32 with encephalitis, 22 with encephalopathy, and 10 with Guillain–Barre syndrome. Sixty-five out of 159 cases with severe neurological manifestations were diagnosed with MIS-C. Direct neuroinvasion and the exaggerated immune response in some patients seem to be the most critical factors triggering these manifestations. Further research in the ongoing pandemic is needed to elucidate the precise mechanism.

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